Stable Isotope Facility

BGS Science Facilities – Centre for Environmental Geochemistry

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We are a node of the National Environmental Isotope Facility (NEIF) and employ a wide variety of stable isotope methodologies in environmental change, pollution, hydrology, and human-landscape interactions research.

We focus on the environment, in particular climate change and human-landscape interactions, with increasing importance on the Anthropocene and the modern calibration period. We also use stable isotopes as tracers of modern pollution and to better understand the hydrological cycle, especially in areas suffering from significant human impact. We work with the UK higher education institutes community and international partners to deliver research, method development and training.

As part of NEIF, the Stable Isotope Facility analytical capabilities and technical expertise can be accessed (free at the point of access) by UK researchers via an application to one of NEIF’s steering committees. We also welcome to opportunity to collaborate via other research funding streams such as NERC Standard or Large Grant applications or via direct access/commercial routes.

Find out more about:

Capability

We are the largest UK producer of stable isotope data, particularly specialising in climate, environmental, and archaeological studies. We undertake high precision 2H/1H, 13C/12C, 15N/14N, 18O/16O, 30Si/28Si, and 34S/32S analysis, at natural abundance levels, of a wide range of sample materials, including waters, carbonates, silicates, organics, N & S compounds, phosphates, and methane. The laboratory has eleven gas-source isotope ratio mass spectrometers that are supported by adaptable ‘off-line’ preparation methods, with access to four high vacuum gas preparation lines, alongside state-of-the-art, fully automated ‘on-line’ techniques.

We specialise in the study of geochemical processes in the hydrosphere and atmosphere, with particular strength in 15N/14N and 34S/32S analysis of a wide variety of compounds associated with nutrient transfer and pollution in the global nitrogen and sulphur cycles. 18O/16O analysis of nitrates, phosphates and sulphates, which can provide valuable additional information on these environmentally important species, has now been added as a routine capability.

Our fluorination 18O/16O and 30Si/28Si analysis of diatoms and other opaline forms of silica is a unique capability in the UK, and one of only a handful of laboratories of its kind in the world.

For archaeological research, we specialise in triple 13C/12C, 15N/14N and 34S/32S methods in palaeodietary studies; and in addition, we have the capability to analyse 18O/16O on a wide range of material (including both phosphate and carbonate analyses of bioapatite). The wider facility’s combined 18O/16O and 87Sr/86Sr capability is especially valuable in studies of archaeological migration.

Materials we analyse include:

  • Waters: 2H/1H and 18O/16O of marine and fresh waters, fluid inclusions (following microlitre extractive methods), and soil/plant materials (following vacuum distillation)
  • Carbonates: 13C/12C and 18O/16O of microfossil and other pure calcium carbonates (down to 5 micrograms), impure carbonates, and aqueous bicarbonate
  • Silicates and phosphates: 18O/16O and 30Si/28Si of rock minerals, biogenic silica, and tooth/bone materials.
  • Organic materials: 2H/1H, 13C/12C, 15N/14N, 18O/16O, and 34S/32S of bulk organic materials (plants, soils, etc.)
  • Nitrogen and Sulphur compounds: 15N/14N, 34S/32S, and 18O/16O of nitrate, ammonium, sulphate, sulphide, and organic nitrogen and sulphur
  • Phosphate: 18O/16O of phosphate from soils, sediments and teeth
  • Methane: 13C/12C and 2H/1H in gas and water samples

The Stable Isotope Facility has eleven isotope ratio mass spectrometer systems:

  • GV Isoprime with EuroPyrOH for analysis of water 2H/1H in marine and fresh waters, fluid inclusions, soil/plant materials
  • Isoprime 100 with AquaPrep for analysis of water 18O/16O in marine and fresh waters, fluid inclusions, soil/plant materials
  • Isoprime 100 with MultiPrep for analysis of 13C/12C and 18O/16O of single microfossils
  • Isoprime precisION with isoFLOW for analysis of 13C/12C and 18O/16O of aqueous bicarbonate
  • GV Isoprime with MultiPrep for analysis of 13C/12C and 18O/16O of microfossil and other pure calcium carbonates
  • VG Optima for analysis of 13C/12C and 18O/16O of impure carbonates and aqueous bicarbonate
  • Isoprime precisION with vario ISOTOPE cube for analysis of 13C/12C, 15N/14N and C/N of bulk organic materials (plants, soils, etc.)
  • Thermo Finnigan DeltaplusXL with oxidative and reductive elemental analysers for analysis of nitrogen and sulphur compounds: 15N/14N, 34S/32S, and 18O/16O of nitrate, ammonium, sulphate, sulphide, and organic N and S as well as 2H/1H, 13C/12C, 15N/14N, 18O/16O, and 34S/32S of bulk organic materials (plants, soils, etc.)
  • Thermo Finnigan MAT 253 with manifold for analysis of 18O/16O and 30Si/28Si of rock minerals, biogenic silica, and tooth/bone materials
  • Thermo Finnigan IsoLink Elemental Analyser linked via continuous flow to a Delta V Isotope Ratio Mass Spectrometer. The IsoLink combines both oxidative combustion, and high temperature reductive pyrolysis and utilises helium management to enable very high precision analysis on a variety of matrices for O/H and C/N/S. The technology allows triple analysis of CNS on small sample sizes at high precision.
  • Sercon Cyroprep for the analysis of 13C/12C and 2H/1H of methane from high to atmospheric concentrations in both gas and water samples.

How to access the Stable Isotope Facility

If you are eligible for a NERC training award or research grant you can apply for access to the Stable Isotope Facility via NEIF, which is free at the point of access. You can find out more about your eligibility by reading section C of the NERC Research Grants handbook.

Before submitting your application, it is important that you first seek the advice of staff at the facility. Applications are reviewed twice yearly (in June and November) by a NEIF panel appointed by NERC. Further details about NEIF, the application process, and a link to the application portal can be found at: isotopesuk.org/

News, awards and publications

2020

May 2020: Congratulations to the following who have received National Environmental Isotope Facility funding at the Spring 2020 meeting for the following research projects

  • IP–2229–0520: Dr K Beck (Lincoln) – Disentangling Southern Hemisphere climate and environmental interactions of the late Pleistocene.
  • IP–2232–0520:  Dr K Edgar (Birmingham) – What was the dominant driver(s) of the early Eocene hyperthermal events? New insights from a benthic foraminiferal record from the Indian Ocean (IODP Site U1514).
  • IP–2236–0520:  Dr S Engels (Birkbeck) – Investigating and refining the use of oxygen isotopes from chironomid head capsule chitin to record past climatic changes.
  • IP–2237–0520:  Prof P Dennis (East Anglia) – RESOLVE.
  • IP–2242–0520:  Dr M Frogley (Sussex) – High-resolution responses to Holocene environmental shifts in the Balkans.
  • IP–2243–0520:  Dr K Selby (York) – Assessing the impact of current and future climate change on UK small lakes.
  • IP–2252–0520:  Prof R Gehrels (York) – Response of peatlands to future climate change: reconciling palaeoecological and experimental methods.
  • IP–2255–0520:  Dr M Jones (Nottingham) – Reconstructing lake levels and palaeohydrology from the Lake Lisan Formation, Jordan.
  • IP–2258–0520:  Dr S Kender (Exeter) – Understanding the causes and consequences of palaeoenvironmental change in the high latitudes during the Toarcian Oceanic Anoxic Event.
  • IP–2260–0520:  Prof B Lomax (Nottingham) – Inferring hydroclimate of subtropical Australia through the Holocene.

2020

May 2020: Meet the isotope hunters: Part 2

In this post, Dr. Andi Smith and Dr. Jack Lacey will continue to explain their work as “Isotope Hunters” for environmental investigations and we will see how the answers provided by isotope fingerprints are powerful tools supporting academics and policymakers in their fight against high levels of pollution in air, water and soil and delivering them information on past climate.

More information

May 2020: Meet the isotope hunters: Part 1

In many countries, institutions are investigating ways to detect and measure pollution levels, allowing regulatory bodies to implement preventive actions to limit the negative effect of pollution on the air, land, and water, and their associated risks for human and environmental health. In environmental investigations that seek to understand climate change or pollution sources, isotope fingerprints can provide a unique insight into the origin or production of a sample material, providing a strong supportive tool for investigators. One such laboratory is the National Environmental Isotope Facility based at the British Geological Survey in Nottingham (UK), where the “Isotope Hunters” have been providing expert support for environmental research. In this series of posts, we want to better understand the work of “Isotope Hunters” for environmental investigations. For this reason, we interviewed Dr. Andi Smith and Dr. Jack Lacey, who will be discussing the work they carry out on environmental change within their specialty of stable isotope geochemistry.

2020

December 2020: Palaeogeography, Palaoclimatology, Palaoecology

The common whelk, Buccinum undatum, is a commercially important gastropod found throughout the North Atlantic. One method of age and life history analysis for gastropod species is the use of oxygen isotope ratio (δ18O) measurements from their shells, which is a well-established technique for the reconstruction of historical seawater temperatures at the time of shell biomineralization. Palaeotemperature calibrations have been developed for different types of calcium carbonate as well as species-specific equations to produce the most accurate seawater temperature reconstructions. Here we investigate the four-layer internal structure of B. undatum shells and confirm an aragonite composition using Micro-Raman Spectroscopy (MRS). We then calibrate a species-specific palaeotemperature equation for this gastropod species. This was achieved through the isotopic analysis of shells from laboratory reared specimens of known provenance reared at specific seawater temperatures to produce the following:

t(°C) = 14.96 (± 0.15) – 4.94 (± 0.22) x (δ18Oshell – δ18Owater)

The calibrated equation differs significantly from previously published data derived from both aragonite and calcite. An offset of 1.04‰ (± 0.41‰) was discovered between observed δ18OShell values and those expected under equilibrium, suggesting a species-specific vital effect. The calibrated equation was used to reconstruct accurate, high resolution historical seawater temperatures from three sites across the U.K. (Shetland, the Menai Strait and Jersey). With this new accurate calibration, both modern and fossil B. undatum shells now have the potential to be employed as high-resolution archives of recent and historical seawater temperature.

Hollyman, P R, Leng, M J, Chenery, S R N, Sloane, H J, and Richardson, C A. 2020. Calibration of shell δ18O from the common whelk Buccinum undatum highlights potential for palaeoenvironmental reconstruction. Palaeogeography, Palaeoclimatology, Palaeoecology.

October 2020: Palaeogeography, Palaoclimatology, Palaoecology

The shell δ18O of young modern Aequipecten opercularis from the southern North Sea provides an essentially faithful record of seasonal variation in seafloor temperature. In this well-mixed setting, A. opercularis shell δ18O also serves as a proxy for seasonal variation in surface temperature. Individuals from less agitated (e.g. deeper) settings in a warm climate would not be expected to record the full seasonal range in surface temperature because of thermal stratification in summer. Such circumstances have been invoked to explain cool isotopic summer temperatures from early Pliocene A. opercularis of eastern England. Support for a sub-thermocline setting derives from high-amplitude variation in microgrowth-increment size, which resembles the pattern in sub-thermocline A. opercularis from the southern Mediterranean Sea. Here, we present isotope and increment profiles from further sub-thermocline individuals, live-collected from a location in the Adriatic Sea for which we provide modelled values of expected shell δ18O. We also present data from supra-thermocline shells from the English Channel and French Mediterranean coast. The great majority of sub-thermocline A. opercularis show high-amplitude variation in increment size, and winter and summer δ18O values are generally quite close to expectation. However, the relatively warm summer conditions of 2015 are not recorded, in most cases due to a break in growth, perhaps caused by hypoxia. The supra-thermocline shells show subdued increment variation and yield isotopic winter and summer temperatures quite close to the local directly measured values. A. opercularis shells therefore provide a fairly good isotopic record of ambient temperature (if not always of relatively warm summer conditions below the thermocline) and their hydrographic setting can be determined from increment data. Early Pliocene examples from eastern England can be interpreted as having lived in a setting below the thermocline, with a higher seasonal range in surface temperature than now in the adjacent southern North Sea.

Johnson, A L A, Valentine, A-M M, Schöne, B R, Leng, M J, Sloane, H J, and Janekoviće, I. 2020. Growth-increment characteristics and isotopic (δ18O) temperature record of sub-thermocline Aequipecten opercularis (Mollusca:Bivalvia): Evidence from modern Adriatic forms and an application to early Pliocene examples from eastern England. Palaeogeography, Palaeoclimatology, Palaeoecology.

October 2020: Palaeogeography, Palaoclimatology, Palaoecology

Reduction in atmospheric pCO2 has been hypothesised as a causal mechanism for the Mid-Pleistocene Transition (MPT), which saw global cooling and increased duration of glacials between 0.6 and 1.2 Ma. Sea ice-modulated high latitude upwelling and ocean-atmospheric CO2 flux is considered a potential mechanism for pCO2 decline, although there are no long-term nutrient upwelling records from high latitude regions to test this hypothesis. Using nitrogen isotopes and opal mass accumulation rates from 0 to 1.2 Ma, we calculate a continuous high resolution nutrient upwelling index for the Bering Sea and assess possible changes to regional CO2 fluxes and to the relative control of sea ice, sea level and glacial North Pacific Intermediate Water (GNPIW) on deep mixing and nutrient upwelling in the region. We find nutrient upwelling in the Bering Sea correlates with global ice volume and air temperature throughout the study interval. From ~1 Ma, and particularly during the 900 ka event, suppressed nutrient upwelling would have lowered oceanic fluxes of CO2 to the atmosphere supporting a reduction in global pCO2 during the MPT. This timing is consistent with a pronounced increase in sea ice during the early Pleistocene and restriction of flow through the Bering Strait during glacials after ~900 ka, both of which would have acted to suppress upwelling. We suggest that sea-level modulated GNPIW expansion during glacials after 900 ka was the dominant control on subarctic Pacific upwelling strength during the mid-late Pleistocene, while sea ice variability played a secondary role.

Worne, S, Kender, S, Swann, G E A Leng, M J, and Ravelo, A C. 2020. Reduced upwelling of nutrient and carbon-rich water in the subarctic Pacific during the Mid-Pleistocene Transition. Palaeogeography, Palaeoclimatology, Palaeoecology, 555, 109845.

September 2020: Science Advances

The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.

Wilke, T, Hauffe, T, Jovanovska, E, Cvetkoska, A, Donders, T, Ekschmitt, K, Francke, A, Lacey, J H, Levkov, Z, Marshall, C R, Neubauer, T A, Silvestro, D, Stelbrink, B, Vogel, H, Albrecht, C, Holtvoeth, J, Krastel, S, Leicher, N, Leng, M J, Lindhorst, K, Masi, A, Ognjanova-Rumenova, N, Panagiotopoulos, K, Reed, J M, Sadori, L, Tofilovska, S, Van Bocxlaer, B, Wagner-Cremer, F, Wesselingh, F P, Wolters, V, Zanchetta, G, Zhang, X, and Wagner, B. 2020. Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem. Science Advances, 6.

September 2020: Marine Micropaleontology

Stable isotope analyses of ostracod shells are a commonly-used proxy for palaeoenvironmental reconstruction. Although the fundamental controls on isotope composition of ostracod shells are well understood and, in some instances, quantifiable, the paleoclimatic and palaeoenvironmental interpretation of records from lake sediments depends strongly on the characteristics of individual lakes including the climatic setting, depth, volume, hydrology, aquatic vegetation and catchment properties. This is particularly important for coastal lakes where physio-chemical variations may occur on diurnal timescales. Here, we combine variations in δ18Owater, δ18Oostracod and δ13Costracod, hourly water temperature, and Mg/Caostracod inferred water temperatures (constraining calcification temperature) to improve palaeoenvironmental interpretation and provide insights into lake carbon cycle. The dataset improves understanding of complex coastal lake site systematics and downcore interpretation of stable isotopes from C. torosa, a geographically widespread brackish water ostracod. The δ18Oostracod values show a complex relationship with temperature and suggest, in most circumstances, that δ18Owater is the dominant control on δ18Oostracod. During times of fresher water, δ13Costracod increases, suggesting increasing aquatic productivity. Above a certain δ18Owater threshold however, aquatic productivity begins to decline. The interpretation of δ13Costracod in some coastal lakes, may therefore be dependent on understanding of the range of expected δ18Owater. Due to short-term (diurnal to seasonal) variations that cause large ranges in δ18Owater and δ18Oostracod, stable isotope analyses of C. torosa should be: (1) undertaken on multiple single shells (2) where carapaces are preserved, paired with trace-element/Ca analyses on the same individual; and (3) undertaken alongside a study of the modern lake system.

Roberts, L R, Holmes, J A, Sloane, H J, Arrowsmith, C, Leng, M J, and Horne, D J. 2020. δ18O and δ13C of Cyprideis torosa from coastal lakes: Modern systematics and down-core interpretation. Marine Micropaleontology. 160.

September 2020: Earth and Planetary Science Letters

The Li/Mg, Sr/Ca and oxygen isotopic (O) compositions of many marine biogenic carbonates are sensitive to seawater temperature. Corals, as cosmopolitan marine taxa with carbonate skeletons that can be precisely dated, represent ideal hosts for these geochemical proxies. However, efforts to calibrate and refine temperature proxies in cold-water corals (<20 °C) remain limited. Here we present skeletal Li/Mg, Sr/Ca, O and carbon isotope (C) data from live-collected specimens of aragonitic scleractinian corals (Balanophyllia, Caryophyllia, Desmophyllum, Enallopsammia, Flabellum, Lophelia, and Vaughanella), both aragonitic and high-Mg calcitic stylasterid genera (Stylaster and Errina), and shallow-water high-Mg calcite crustose coralline algae (Lithophyllum, Hydrolithon, and Neogoniolithon). We interpret these data in conjunction with results from previously explored taxa including aragonitic zooxanthellate scleractinia and foraminifera, and high-Mg calcite octocorals. We show that Li/Mg ratios covary most strongly with seawater temperature, both for aragonitic and high-Mg calcitic taxa, making for reliable and universal seawater temperature proxies. Combining all of our biogenic aragonitic Li/Mg data with previous calibration efforts we report a refined relationship to temperature: Li/MgAll Aragonite =  (). This calibration now permits paleo-temperature reconstruction to better than ±3.4 °C (95% prediction intervals) across biogenic aragonites, regardless of taxon, from 0 to 30 °C. For taxa in this study, aragonitic stylasterid Li/Mg offers the most robust temperature proxy (Li/MgStylasterid (Arag) =  ()) with a reproducibility of ±2.3 °C. For the first time, we show that high-Mg calcites have a similar exponential relationship with temperature, but with a lower intercept value (Li/Mg =  ()). This calibration opens the possibility of temperature reconstruction using high-Mg calcite corals and coralline algae. The commonality in the relationship between Li/Mg and temperature transcends phylogeny and suggests a similar abiogenic trace metal incorporation mechanism.

Stewart, J A, Robinson, L F, Day, R D, Strawson, I, Burke, A, Rae, J W B, Spooner, P T, Samperiz, A, Etnoyer, P J, Williams, B, Paytan, A, Leng, M J, Häussermann, V, Wickes, L N, Bratt, R, and Pryer, H. 2020. Refining trace metal temperature proxies in cold-water scleractinian and stylasterid corals. Earth and Planetary Science Letters, 545, 116412.

September 2020: Earth and Planetary Science Letters

Stylasterids are a ubiquitous deep-sea coral taxon that build their skeletons from either calcite, aragonite, or both. Yet, robust geochemical proxy data from these corals are limited. In this study, 95 modern stylasterids, spanning a wide range of depths (63 to 2894 m) and ambient seawater temperatures (0 to 17 °C), were tested for their potential use as paleoceanographic archives. Stable oxygen and carbon isotopic composition (O and C) were measured from the main trunk of all specimens and five specimens were further sub-sampled to assess internal chemical variability. The isotope data show non-equilibrium precipitation from seawater for both O and C, with the growing tips of colonies yielding the isotopically lowest values. Overall, the calcitic corals showed lower isotope values for O and C than aragonitic specimens. Within the aragonite corals, we present a O:temperature calibration that exhibits a significant linear relationship with the equation Ocoral-seawater = −0.22(°C) + 3.33(±0.06) across a temperature range of 0 to 30 °C, using samples from this study and published data. This work highlights the potential application of stylasterid coral O data to reconstruct paleo seawater temperature.

Samperiz, A, Robinson, L F, Stewart, J A, Strawson, I, Leng, M J, Rosenheim, B E, Ciscato, E R, Hendry, K R, and Santodomingo, N. 2020. Stylasterid corals: A new paleotemperature archive. Earth and Planetary Science Letters, 545, 116407.

August 2020: Geobiology

With annual precipitation less than 20 mm and extreme UV intensity, the Atacama Desert in northern Chile has long been utilized as an analogue for recent Mars. In these hyperarid environments, water and biomass are extremely limited, and thus, it becomes difficult to generate a full picture of biogeochemical phosphate‐water dynamics. To address this problem, we sampled soils from five Atacama study sites and conducted three main analyses—stable oxygen isotopes in phosphate, enzyme pathway predictions, and cell culture experiments. We found that high sedimentation rates decrease the relative size of the organic phosphorus pool, which appears to hinder extremophiles. Phosphoenzyme and pathway prediction analyses imply that inorganic pyrophosphatase is the most likely catalytic agent to cycle P in these environments, and this process will rapidly overtake other P utilization strategies. In these soils, the biogenic δ18O signatures of the soil phosphate (δ18OPO4) can slowly overprint lithogenic δ18OPO4 values over a timescale of tens to hundreds of millions of years when annual precipitation is more than 10 mm. The δ18OPO4 of calcium‐bound phosphate minerals seems to preserve the δ18O signature of the water used for biogeochemical P cycling, pointing toward sporadic rainfall and gypsum hydration water as key moisture sources. Where precipitation is less than 2 mm, biological cycling is restricted and bedrock δ18OPO4 values are preserved. This study demonstrates the utility of δ18OPO4 values as indicative of biogeochemical cycling and hydrodynamics in an extremely dry Mars‐analogue environment.

Shen, J, Smith, A C, Claire, M W, and  Zerkle, A L. Unraveling biogeochemical phosphorus dynamics in hyperarid Mars‐analogue soils using stable oxygen isotopes in phosphate. Geobiology. 2020; 00: 1– 20.

August 2020: Quaternary Science Reviews

The Holocene hydroclimate of south-central Alaska has been studied extensively, but conflicting interpretations between oxygen isotope paleoclimate datasets are seemingly as common as converging reconstructions, in part due to the challenges of interpreting oxygen isotope ratios in terms of climate. Here, we present a new Holocene record of biogenic silica abundance (BSi), diatom flora, and diatom oxygen isotopes (δ18OBSi) analyzed in sediments from Sunken Island Lake (SIL) in the Kenai Peninsula lowlands, which we interpret in the context of previously published paleoclimate records, and use to understand regional changes in hydroclimate. Changes in lake level documented by aerial photography coupled with a survey of regional lake water isotopes indicate SIL is sensitive to changes in the balance of precipitation and evaporation (P-E). However, an analysis of SIL δ18OBSi over the instrumental period indicates that δ18OBSi is sensitive to both P-E and the isotope composition of precipitation (δ18Oprecip), which is driven by changes in the Aleutian Low atmospheric pressure cell (AL). We attribute a ∼2‰ increase in δ18OBSi from 5.5 to 4.5 ka cal BP to a stronger AL, which resulted in the delivery of isotopically heavier precipitation to the Kenai lowlands, and wetter conditions during the late Holocene. These interpretations are supported by late Holocene increases in the relative abundance of planktonic diatoms and BSi-inferred storminess, and by evidence for higher-than-present lake levels on the paleo-shorelines above SIL at ∼1.5–0.5 ka cal BP. Our dataset demonstrates that this region was characterized by relatively low lake levels and dry climate in the early Holocene, a strengthening of the AL in the late Holocene, and wetter climate during the late Holocene until recent decades.

Broadman, E, Kaufman, D S, Henderson, A C E, Berg, E E, Anderson, S, Leng, M J, Stahnke, S A, and Muñoz, S E. 2020. Multi-proxy evidence for millennial-scale changes in North Pacific Holocene hydroclimate from the Kenai Peninsula lowlands, south-central Alaska. Quaternary Science Reviews, 241, 106420.

August 2020: Earth-Science Reviews

Understanding and quantifying the processes and geochemical cycles associated with catchment erosion, the development of soils and weathering horizons, and terrestrial habitat change beyond the scales of modern observations remain challenging. Such research, however, has become increasingly important to help predict future landscape change in light of increasing land use and rapid global warming. We herein review organic and inorganic geochemical tools applied to depositional archives to better understand various aspects of landscape evolution on geological time scales. We highlight the potentials and limitations of inorganic geochemical analytical methods, such as major element geochemistry, metal and radiogenic isotopes, and in-situ cosmogenic nuclides, as qualitative, semi-quantitative, and quantitative proxies for the transformation of bedrock material via regolith and soils to sediments. We also show how stable isotope geochemistry applied to lacustrine endogenic carbonates can be used to infer rock-water interactions, vegetation change, and soil development in limestone-rich catchments. Proxies focusing on the silicilastic element of sediment formation, transport and deposition are ideally combined with organic geochemical proxies for vegetation change and soil organic matter evolution in a catchment to gain a comprehensive picture of the Critical Zone’s evolution over time. Multi-proxy and multidisciplinary research combining organic and inorganic geochemical techniques from several sedimentary archives in the same catchment have high potential to provide comprehensive information on Quaternary landscape evolution and thus improve the robustness of associated forecasting models.

Francke, A, Holtvoeth, J, Codilean, A, Lacey, J H, Bayon, G, and Dosseto, A. 2020. Geochemical methods to infer landscape response to Quaternary climate change and land use in depositional archives: A review. Earth-Science Reviews, 207, 103218.

July 2020: Hydrological Processes

The young water fraction of streamflow (Fyw), an important hydrological variable, has been calculated for the first time, for a monsoon‐fed coastal catchment in northern Vietnam. Oxygen stable isotopes (δ18O) from 6 river sites in the Day River Basin (DRB) were analysed monthly, between January 2015 and December 2018. River δ18O signatures showed sine wave variability, reflecting the amount effect and tropical (dry‐rainy) seasonality of the region. The δ18O composition of precipitation ranged from ‐12.67 to +1.68‰, with a mean value of ‐5.14‰, and in‐streamflow signatures ranged from ‐11.63 to ‐1.37‰ with a mean of ‐5.02‰. Fractions of young water (Fyw) were calculated from the unweighted and flow‐weighted δ18O composition of samples. Unweighted Fyw ranged between 29±8% and 82±21% with a mean value of 51±19%, and was not significantly different from flow‐weighted Fyw (range between 33±25% and 92±73%, mean 52±36%). Both unweighted and flow‐weighted Fyw were highest in the middle of stream and lowest in downstream sites, capturing the impacts of landuse changes, hydrology, and human activities in the catchment. Our calculations imply that more than a half of rainwater reaches the DRB river mainstream within the first 3 months. The Fyw is much higher than the global average (of one third) and insensitive to discharge due to the combination of a humid catchment with high rainfall, low storage capacity, flat landscape and an intensive drainage system in the DRB. Also the low discharge sensitivity of Fyw in the DRB implies that the regional hydrology is severely altered by humans.

Duc, T A, Nga, D T, Panizzo, V N, McGowan, S, and Leng, M J. 2020. Using stable isotopes to estimate young water fractions in a heavily‐regulated, tropical lowland river basin. Hydrological Processes.

July 2020: Quaternary Science Reviews

Andøya on the NW coast of Norway is a key site for understanding the Last Glacial Maximum (LGM) in northern Europe. Controversy has arisen concerning the local conditions, especially about the timing and extent of local glacial cover, maximum July temperatures and whether pine and/or spruce could have grown there. We reviewed all existing data and add newly analysed ancient sedimentary DNA (sedaDNA), pollen, macrofossils, geochemistry and stable isotopes from three lake sediment cores from Øvre Æråsvatnet. A total of 23 new dates and age-depth modelling suggests the lake has been ice-free since GI2 (<23.4 cal ka BP) and possibly GS3 (<26.7 cal ka BP). Pinus and Picea sedaDNA was found in all three cores but at such low frequencies that it could not be distinguished from background contamination. LGM samples have an exceptionally high organic matter content, with isotopic values indicating that carbon and nitrogen derive from a marine source. Along with finds of bones of the little auk (Alle alle), this indicates that the lake received guano from an adjacent bird colony. SedaDNA, pollen and macrofossil assemblages were dominated by Poaceae, Brassicaceae and Papaver, but scattered occurrence of species currently restricted to the Low Arctic Tundra Zone (July temperature of 8–9 °C) such as Apiaceae (sedaDNA, 8–9 °C), and Alchemilla alpina (macrofossil, 8–9 °C) were also recorded. The review of >14.7 cal ka BP data recorded 94 vascular plant taxa, of which 38% have a northern limit in Shrub Tundra or more southern vegetation zones. This unusual assemblage likely stems from a combination of proximity to ice-free water in summer, geographical isolation linked with stochastic long-distance dispersal events, and the presence of bird-fertilized habitats. The environmental reconstruction based on all records from the area does not preclude local growth of tree species, as the local climate combined with high nutrient input may have led to periodically suitable environmental ‘hotspot’ conditions.

Alsos, I, Sjögren, P, Brown, A, Gielly L, Merkel, M, Paus, A, Lammers, Y, Edwards, M, Alm, T, Leng, M, Goslar, T, Langdon, C, Bakke, J, and van der Bilt, W. 2020. Last Glacial Maximum environmental conditions at Andøya, northern Norway; evidence for a northern ice-edge ecological “hotspot”. Quaternary Science Reviews, 239.

June 2020: Chemical Geography

Although the oxygen isotope composition (δ18O) of calcite (δ18Ocalcite) and, to a lesser extent, diatom silica (δ18Odiatom) are widely used tracers of past hydroclimates (especially temperature and surface water hydrology), the degree to which these two hosts simultaneously acquire their isotope signals in modern lacustrine environments, or how these are altered during initial sedimentation, is poorly understood. This study compares oxygen and hydrogen isotope data (δ18O, δ2H) of contemporary lake water samples at ~2-weekly intervals over a 2-year period (2010–12) with matching collections of diatoms (δ18Odiatom) and calcite (δ18Ocalcite) from sediment traps (at 10 m and 25 m) at Rostherne Mere (maximum depth 30 m), a well-monitored, eutrophic, seasonally stratified monomictic lake in the UK. The epilimnion shows a seasonal pattern of rising temperature and summer evaporative enrichment in 18O, and while there is a temperature imprint in both δ18Odiatom and δ18Ocalcite, there is significant inter-annual variability in both of these signals. The interpretation of δ18Odiatom and δ18Ocalcite values is complicated due to in-lake processes (e.g. non-equilibrium calcite precipitation, especially in spring, leading to significant 18Ocalcite depletion), and for δ18Odiatom, by post-mortem, depositional and possibly dissolution or diagenetic effects. For 2010 and 2011 respectively, there is a strong temperature dependence of δ18Ocalcite and δ18Odiatom in fresh trap material, with the fractionation slope for δ18Odiatom of ca. −0.2‰/°C, in agreement with several other studies. The δ18Odiatom data indicate the initiation of rapid post-mortem secondary alteration of fresh diatom silica (within ~6 months), with some trap material undergoing partial maturation in situ. Diatom δ18O of the trap material is also influenced by resuspension of diatom frustules from surface sediments (notably in summer 2011), with the net effect seen as an enrichment of deep-trap 18Odiatom by about +0.7‰ relative to shallow-trap values. Contact with anoxic water and anaerobic bacteria are potentially key to initiating this silica maturation process, as deep-trap samples that were removed prior to anoxia developing do not show enrichment. Dissolution (perhaps enhanced by anaerobic bacterial communities) may also be responsible for changes to δ18Odiatom that lead to increasing, but apparently predictable, error in inferred temperatures using this proxy. High resolution, multi-year monitoring can shed light on the complex dynamics affecting δ18Odiatom and δ18Ocalcite and supports the careful use of sedimentary δ18Odiatom and δ18Ocalcite as containing valuable hydroclimatic signals especially at a multi-annual resolution, although there remain substantial challenges to developing a reliable geothermometer on paired δ18Odiatom and δ18Ocalcite. In particular, δ18Odiatom needs cautious interpretation where silica post-mortem secondary alteration is incomplete and diatom preservation is not perfect, and we recommend dissolution be routinely assessed on diatom samples used for isotopic analyses.

Ryves, D B, Leng, M J, Barker, P A, Snelling, A M, Sloane, H J, Arrowsmith, C, Tyler, J J, Scott, D R, Radbourne, A D, and Anderson, N J. 2020. Understanding the transfer of contemporary temperature signals into lake sediments via paired oxygen isotope ratios in carbonates and diatom silica: Problems and potential, Chemical Geology, 119705.

May 2020: Quaternary Science Reviews

We provide evidence for a large-scale geomorphic event in Cambodia’s great lake, the Tonlé Sap, during the middle Holocene. The present-day hydrology of the basin is dominated by an annual flood pulse where water from the Mekong River raises the lake level by c. 8 m during the monsoon season. We present new subsurface geophysical data, allied to new and past core studies, which unequivocally show a period of major mid-Holocene erosion across the entire Tonlé Sap basin that is coincident with establishment of the lake’s flood pulse. We argue that this widespread erosion, which removed at least 1.2 m of sediment across the lake’s extent, was triggered by up to three, likely interacting, processes: (1) base-level lowering due to mid-Holocene sea-level fall, leading to (2) capture of the Tonlé Sap drainage by the Mekong River, and (3) a drying climate that also reduced lake level. Longer-term landscape evolution was thus punctuated by a rapid, river capture- and base-level fall- induced, lake drainage that established the ecosystem that flourishes today. The scale of change induced by this mid-Holocene river capture event demonstrates the susceptibility of the Tonlé Sap lake to ongoing changes in local base-level and hydrology induced by anthropogenic activity, such as damming and sand mining, within the Mekong River Basin.

Darby, S E Langdon, P G, Best, J L, Leyland, J, Hackney, C R Marti, M, Morgan, P R, Ben, S, Aalto, R, Parsons, D R, Nicholas, A P, and Leng, M J. 2020. Drainage and erosion of Cambodia’s great lake in the middle-late Holocene: The combined role of climatic drying, base-level fall and river capture. Quaternary Science Reviews, 236, 106265.

May 2020: Scientific Drilling

The Neogene and Quaternary are characterised by enormous changes in global climate and environments, including global cooling and the establishment of northern high–latitude glaciers. These changes reshaped global ecosystems, including the emergence of tropical dry forests and savannahs that are found in Africa today, which in turn may have influenced the evolution of humans and their ancestors. However, despite decades of research we lack long, continuous, well-resolved records of tropical climate, ecosystem changes, and surface processes necessary to understand their interactions and influences on evolutionary processes. Lake Tanganyika, Africa, contains the most continuous, long continental climate record from the mid-Miocene (~10 Ma) to the present anywhere in the tropics and has long been recognised as a top priority site for scientific drilling. The lake is surrounded by the Miombo woodlands, part of the largest dry tropical biome on Earth. Lake Tanganyika also harbors incredibly diverse endemic biota and an entirely unexplored deep microbial biosphere, and it provides textbook examples of rift segmentation, fault behaviour, and associated surface processes. To evaluate the interdisciplinary scientific opportunities that an ICDP drilling program at Lake Tanganyika could offer, more than 70 scientists representing 12 countries and a variety of scientific disciplines met in Dar es Salaam, Tanzania, in June 2019. The team developed key research objectives in basin evolution, source-to-sink sedimentology, organismal evolution, geomicrobiology, palaeoclimatology, palaeolimnology, terrestrial palaeoecology, palaeoanthropology, and geochronology to be addressed through scientific drilling on Lake Tanganyika. They also identified drilling targets and strategies, logistical challenges, and education and capacity building programs to be carried out through the project. Participants concluded that a drilling program at Lake Tanganyika would produce the first continuous Miocene–present record from the tropics, transforming our understanding of global environmental change, the environmental context of human origins in Africa, and providing a detailed window into the dynamics, tempo and mode of biological diversification and adaptive radiations.

Russell, J M, Barker, P, Cohen, A, Ivory, S, Kimirei, I, Lane, C, Leng, M, Maganza, N, McGlue, M, Msaky, E, Noren, A, Park Boush, L, Salzburger, W, Scholz, C, Tiedemann, R, Nuru, S, and the Lake Tanganyika Scientific Drilling Project (TSDP) Consortium. 2020. ICDP workshop on the Lake Tanganyika Scientific Drilling Project: a late Miocene–present record of climate, rifting, and ecosystem evolution from the world’s oldest tropical lake, Sci. Dril., 27, 53–60.

May 2020: Geography and the Environment

Rapid development and climate change in southeast Asia is placing unprecedented pressures on freshwater ecosystems, but long term records of the ecological consequences are rare. Here we examine one basin of Tasik Chini (Malaysia), a UNESCO‐designated flood pulse wetland, where human disturbances (dam installation, iron ore mining, oil palm and rubber cultivation) have escalated since the 1980s. Diatom analysis and organic matter geochemistry (δ13Corg and C/N ratios) were applied to a sediment sequence to infer ecological changes in the basin since c. 1900 CE. As the Tasik Chini wetland is a rare ecosystem with an unknown diatom ecology, contemporary diatom habitats (plant surfaces, mud surfaces, rocks, plankton) were sampled from across the lake to help interpret the sedimentary record. Habitat specificity of diatoms was not strongly defined and, although planktonic and benthic groupings were distinctive, there was no difference in assemblages among the benthic habitat surfaces. An increase in the proportion of benthic diatom taxa suggests that a substantial decrease in water level occurred between c. 1938 and 1995 CE, initiated by a decline in rainfall (supported by regional meteorological data), which increased the hydrological isolation of the sub‐basin. Changes in the diatom assemblages were most marked after 1995 CE when the Chini dam was installed. After this time both δ13Corg and C/N decreased, suggesting an increase in autochthonous production relative to allochthonous river flood pulse inputs. Oil palm plantations and mining continued to expand after c. 1995 CE and we speculate that inputs of pollutants from these activities may have contributed to the marked ecological change. Together, our work shows that this sub‐basin of Tasik Chini has been particularly sensitive to, and impacted by, a combination of human and climatically induced changes due to its hydrologically isolated position.

Briddon, C L, McGowan, S, Metcalfe, S E, Panizzo, V, Lacey, J, Engels, S, Leng, M, Mills, K, Shafiq, M, and Idris, M. 2020. Diatoms in a sediment core from a flood pulse wetland in Malaysia record strong responses to human impacts and hydro–climate over the past 150 yearsGeo: Geography and Environment.

April 2020: PNAS

The timing of human colonization of East Polynesia, a vast area lying between Hawai‘i, Rapa Nui, and New Zealand, is much debated and the underlying causes of this great migration have been enigmatic. Our study generates evidence for human dispersal into eastern Polynesia from islands to the west from around AD 900 and contemporaneous paleoclimate data from the likely source region. Lake cores from Atiu, Southern Cook Islands (SCIs) register evidence of pig and/or human occupation on a virgin landscape at this time, followed by changes in lake carbon around AD 1000 and significant anthropogenic disturbance from c. AD 1100. The broader paleoclimate context of these early voyages of exploration are derived from the Atiu lake core and complemented by additional lake cores from Samoa (directly west) and Vanuatu (southwest) and published hydroclimate proxies from the Society Islands (northeast) and Kiribati (north). Algal lipid and leaf wax biomarkers allow for comparisons of changing hydroclimate conditions across the region before, during, and after human arrival in the SCIs. The evidence indicates a prolonged drought in the likely western source region for these colonists, lasting c. 200 to 400 y, contemporaneous with the phasing of human dispersal into the Pacific. We propose that drying climate, coupled with documented social pressures and societal developments, instigated initial eastward exploration, resulting in SCI landfall(s) and return voyaging, with colonization a century or two later. This incremental settlement process likely involved the accumulation of critical maritime knowledge over several generations.

Sear, D A, Allen, M S, Hassall, J D, Maloney, A E, Langdon, P G, Morrison, A E, Henderson, A C G, Mackay, H, Croudace, I W, Clarke, C, Sachs, J, Macdonald, G, Chiverrell, R, Leng, M, Cisneros-Dozal, L, and Fonville, T. 2020. Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought. Proceedings of the National Academy of Sciences of the United States of America, 117, 8813–8819.

March 2020: Palaeogeography, Palaeoclimatology, Palaeoecology

Wetland sediments archive information about past terrestrial ecosystem change including variations in fire occurrence and terrestrial carbon fluxes. The charcoal content of sediments is important for understanding past fire regimes, as well as the role this recalcitrant carbon plays in the global carbon cycle. Infrared (IR) spectroscopy provides a rapid, non-destructive and cost effective method for simultaneously analysing numerous organic and inorganic sediment properties. The use of IR spectroscopy is well developed for determining concentrations of total organic carbon (TOC), total nitrogen (TN), biogenic silica and carbonate in lacustrine sediments. In soil science IR spectroscopy is also routinely used to determine charcoal content, however the potential for analysing charcoal content from lacustrine sediments has yet to be investigated. Here we develop IR spectroscopy and partial least squares regressions (PLSR) to predict the charcoal and TOC content of an organic, 130,000 year old sediment sequence from North Stradbroke Island (Minjerribah), Australia. Charcoal concentrations used for model development were derived using both traditional palaeoecological area measures (cm2 g−1) and solid state 13C nuclear magnetic resonance (13C NMR) of poly-aryl structures. The IR PLSR models yielded significant correlations for the two charcoal methodologies (area measurements, R2 = 0.57, p < .05; 13C NMR, R2 = 0.70, p < .05). We additionally find a very strong, significant, correlation for TOC (R2 = 0.92, p < .05), consistent with previous studies. Hence, IR is a promising tool for determining the charcoal content of lacustrine sediments, particularly for first-order sample screening, as part of a multi-proxy framework. IR spectroscopy can therefore provide a reliable and rapid technique for the initial investigation of fire histories and organic constituents of sedimentary sequences.

Cadd, H R, Tyler, J, Tibby, J, Baldock, J, Hawke, B, Barr, C, and Leng, M.J. 2020. The potential for rapid determination of charcoal from wetland sediments using infrared spectroscopy. Palaeogeography, Palaeoclimatology, Palaeoecology, 542,109562.

February 2020: PNAS

Global perturbations to the Early Jurassic environment (∼201 to ∼174 Ma), notably during the Triassic–Jurassic transition and Toarcian Oceanic Anoxic Event, are well studied and largely associated with volcanogenic greenhouse gas emissions released by large igneous provinces. The long-term secular evolution, timing, and pacing of changes in the Early Jurassic carbon cycle that provide context for these events are thus far poorly understood due to a lack of continuous high-resolution δ13C data. Here we present a δ13CTOC record for the uppermost Rhaetian (Triassic) to Pliensbachian (Lower Jurassic), derived from a calcareous mudstone succession of the exceptionally expanded Llanbedr (Mochras Farm) borehole, Cardigan Bay Basin, Wales, United Kingdom. Combined with existing δ13CTOC data from the Toarcian, the compilation covers the entire Lower Jurassic. The dataset reproduces large-amplitude δ13CTOC excursions (>3‰) recognized elsewhere, at the Sinemurian–Pliensbachian transition and in the lower Toarcian serpentinum zone, as well as several previously identified medium-amplitude (∼0.5 to 2‰) shifts in the Hettangian to Pliensbachian interval. In addition, multiple hitherto undiscovered isotope shifts of comparable amplitude and stratigraphic extent are recorded, demonstrating that those similar features described earlier from stratigraphically more limited sections are nonunique in a long-term context. These shifts are identified as long-eccentricity (∼405-ky) orbital cycles. Orbital tuning of the δ13CTOC record provides the basis for an astrochronological duration estimate for the Pliensbachian and Sinemurian, giving implications for the duration of the Hettangian Stage. Overall the chemostratigraphy illustrates particular sensitivity of the marine carbon cycle to long-eccentricity orbital forcing.

Storm, M S, Hesselbo, S P Jenkyns, H C, Ruhl, M, Ullmann, C V, Xu, W, Leng, M J, Riding, J B, and Gorbanenko, O. 2020. Orbital pacing and secular evolution of the Early Jurassic carbon cycle. Proceedings of the National Academy of Sciences of the United States of America, 117, 3974–3982.

February 2020: Scientific Reports

Field data about the effect of soil pH on phosphorus (P) cycling is limited. A promising tool to study P cycling under field conditions is the 18O/16O ratio of phosphate (δ18OP). In this study we investigate whether the δ18OP can be used to elucidate the effect of soil pH on P cycling in grasslands. Soils and plants were sampled from different fertilisation and lime treatments of the Park Grass long term experiment at Rothamsted Research, UK. The soils were sequentially extracted to isolate different soil P pools, including available P and corresponding δ18OP values were determined. We did not observe changes in plant δ18OP value, but soil P δ18OP values changed, and lower δ18OP values were associated with higher soil pH values. At sites where P was not limiting, available P δ18OP increased by up to 3‰ when lime was applied. We show that the δ18OP method is a useful tool to investigate the effect of pH on soil P cycling under field conditions as it highlights that different soil processes must govern P availability as pH shifts. The next challenge is now to identify these underlying processes, enabling better management of soil P at different pH.

Pfahler, V, Macdonald, A, Mead, A, Smith, A C, and Tamburini, F. 2020. Changes of oxygen isotope values of soil P pools associated with changes in soil pHScientific Reports 10.

January 2020: Quaternary Science Reviews

Mediterranean mid-altitude sites are critical for the survival of plant species allowing for elevational vegetation shifts in response to high-amplitude climate variability. Pollen records from the southern Balkans have underlined the importance of the region in preserving plant diversity over at least the last half a million years. So far, there are no records of vegetation and climate dynamics from Balkan refugia with an Early Pleistocene age. Here we present a unique palynological archive from such a refugium, the Lake Ohrid basin, recording continuously floristic diversity and vegetation succession under obliquity-paced climate oscillations. Palynological data are complemented by biomarker, diatom, carbonate isotope and sedimentological data to identify the mechanisms controlling shifts in the aquatic and terrestrial ecosystems within the lake and its catchment. The study interval encompasses four complete glacial-interglacial cycles (1365–1165 ka; MIS 43–35). Within the first 100 kyr of lake ontogeny, lake size and depth increase before the lake system enters a new equilibrium state as observed in a distinct shift in biotic communities and sediment composition. Several relict tree genera such as Cedrus, Tsuga, Carya, and Pterocarya played an important role in ecological succession cycles, while total relict abundance accounts for up to half of the total arboreal vegetation. The most prominent biome during interglacials is cool mixed evergreen needleleaf and deciduous broadleaf forests, while cool evergreen needleleaf forests dominate within glacials. A rather forested landscape with a remarkable plant diversity provide unique insights into Early Pleistocene ecosystem resilience and vegetation dynamics.

Panagiotopoulos, K, Holtvoeth, J, Kouli, K, Marinova, E, Francke, A, Cvetkoska, A, Jovanovska, E, Lacey, J, Lyons, E, Buckel, C, Bertini, A, Donders, T, Just, J, Leicher, N, Leng, M, Melles, M, Pancost, R, Sadori, L, Tauber, P, Vogel, H, Wagner, B, and Wilke, T 2020. Insights into the evolution of the young Lake Ohrid ecosystem and vegetation succession from a southern European refugium during the Early Pleistocene. Quaternary Science Reviews, 227.

January 2020: Marine Geology

Remotely operated vehicle (ROV) explorations of the Kahouanne Seamounts, located 25 km SE of Montserrat in the northern Lesser Antilles island arc, have discovered the occurrence of honeycomb-scalloped erosional features on volcanic and limestone outcrops at depths of up to 600 m below sea level (mbsl). These features, combined with the flat-topped morphology of the seamounts, the occurrence of shallow-water carbonates (rhodoliths, benthic foraminifera), and the presence of oxidized, highly-vesicular volcanic fragments, suggest that the seamounts were once subaerial islands and have subsequently subsided to their present depth. The subsidence is likely to have been in response to a combination of 1) graben development southeast of the island of Montserrat where faulting and extension are driven by the accommodation of slip convergence associated with oblique subduction along the Lesser Antilles volcanic arc and 2) regional subsidence inferred from studies of nearby carbonate platforms. 40Ar/39Ar dating of basalt/andesite lavas from the central seamount indicates active volcanism around 5.4 Ma. Shallow-water carbonates recovered from an apparent wave-cut terrace at ~600 mbsl in the same area, were deposited approximately 3 Ma, based on Sr-isotope stratigraphy, indicating significant subsidence of the complex since that time. The total subsidence is in line with displacements in the Kahouanne valley graben and regional subsidence rates inferred from carbonate platform depths around the islands of Guadeloupe and Martinique, implying that intra-arc subsidence has been a significant process shaping the present bathymetry and topography of this island arc.

Carey, S, Sparks, R S J, Tucker, M E, Li, T, Robinson, L, Watt, S F L, Gee, M, Hastie, A, Barfod, D N, Stinton, A, Leng, M, Raineault, N, and Ballard, R.D. 2020. The polygenetic Kahouanne Seamounts in the northern Lesser Antilles island arc: Evidence for large-scale volcanic island subsidence. Marine Geology, 419, 106046.

January 2020: Journal of Biogeography

A sedimentary record covering the last c. 10 500 years was recovered from the volcanic crater that contains Lake Lanoto’o near the centre of Upolu Island. Information on past ecological change was obtained from microscopic and macroscopic remains extracted from the sediments: charcoal (fire history), pollen/spores and plant remains (vegetation history), and lake status (algae/cyanobacteria). Information on the depositional environment and climate was obtained from geochemical and sedimentary analysis: loss-on-ignition (sediment composition), cryptotephras (volcanic eruptions) and precipitation regime (Ti/inc). The environmental history developed was compared with the archaeological record from the region. Charcoal material was found in the Lake Lanoto’o sediments at higher abundances and more frequently in samples from the period after the first archaeological evidence of people on Upolu (c. 2900–2700 years ago). No abrupt shift is recognized in the vegetation or aquatic ecosystem assemblages coincident with the arrival of people on the island. Macrocharcoal is demonstrated to be an effective proxy for detecting human occupation of Upolu around 2800 years ago. The immediate impact of these settlers on the vegetation seems to have been minimal; however, a subsequent opening up of the landscape is suggested through the gradual increase in ferns. The absence of any significant change in the aquatic community associated with, or after, the arrival of people on the islands suggests that humans rarely visited the lake. We suggest that on Upolu a simple model of decreasing human impact away from coastal areas is applicable.

Gosling, W D, Sear, D A, Hassall, J D, Langdon, P G, Bönnen, M N T, Driessen, T D, van Kemenade, Z R, Noort, K, Leng, M J, Croudace, I W, Bourne, A J, and McMichael, C N H. 2020. Human occupation and ecosystem change on Upolu (Samoa) during the Holocene. Journal of Biogeography.

Contact

Contact Béatrice Bullock-von Moos for further information about the Stable isotope facility.

Archive

April 2019: European Science Foundation

Congratulations to Prof Melanie Leng who has been appointed to sit on the European Science Foundation College of external reviewers for a three year period.

March 2019: Isotopes in Biogenic Silica group

Congratulations to Jack Lacey for being invited to be a convenor of the working group: Isotopes in Biogenic Silica (IBiS). The study of biogenic silica (silica deposited in plants, algae and animals) in Quaternary sediments is currently being revolutionised by technical advances in stable-isotope mass spectrometry, ICP–MS and 32Si dating. Growing interest in the global biogeochemical cycle of silicon and its coupling with the carbon cycle is evident from an upsurge of papers, while a wide range of disciplines including physiology, ecology, geochemistry, hydrology, geomorphology, pedology, agronomy, forestry, limnology, oceanography and biogeochemical modelling has begun to focus on processes involving biogenic silica in the modern environment.

2019

November 2019: Congratulations to the following who have received National Environmental Isotope Facility funding at the Autumn 2019 meeting for the following research projects

  • EK307–08/18: Dr C Rice (Southampton) — Macroecological study of the field metabolic rates of marine fishes using otolith carbon stable isotopes
  • IP–1939–1119: D Gooddy (BGS) — A multi–nutrient isotope approach to understand the impact of water treatment on inorganic nitrogen and phosphorus in public water supplies
  • IP–1942–1119: R Holdsworth (Durham) — Fracture connectivity and fluid sourcing in the Cleveland Basin
  • IP–1943–1119: M Jones (Nottingham) — 2,000 years of hydrological change in Africa: implications for future climate scenarios
  • IP–1944–1119: J Lee–Thorp (Oxford) — Sea surface temperature and hunter–gatherer marine resource use from marine carbonates in northern Japanese prehistory
  • IP–1948–1119: S McGowan (Nottingham) — Understanding long–term environmental conditions to inform sustainable aquaculture development in Lake Victoria, Kenya
  • IP–1949–1119: H O’Regan (Nottingham) — A multi–isotope study of human movement and diet in Middle Saxon East Anglia
  • IP–1950–1119: V Peck (BAS) — Reconstructing variability of the “cold water route” through the late Pleistocene

June 2019: Member of the British Empire

Melanie Leng, head of the Stable isotope facility (and Chief Scientist for Environmental Change Adaptation and Resilience) has been awarded an MBE in this year’s Queen’s Birthday Honours List for services to environmental science. The list, which has been published annually since 1917, recognises those who have contributed to the British Empire. MBE, or Member of the British Empire, is bestowed upon those who have made a considerable contribution to the community through their line of work.

June 2019: The following NEIF–SC applications to the stable isotope facility at BGS were awarded

  • IP–1901–0619: Dr K Adamson (Manchester Met) – Reconstructing palaeoenvironmental conditions in the Egyptian Nile Valley from the Old Kingdom to present (pilot)
  • IP–1910–1019: Dr A Henderson (Newcastle) – Holocene climate evolution in Arctic Alaska and its link to Aleutian Low variability
  • IP–1913–0619: Dr B Hoogakker (Heriot Watt) – Lessons from the past: Deoxygenation of the ocean
  • IP–1914–1619: Dr S Kender (Exeter) – Deep sea biotic responses during Cretaceous Oceanic Anoxic Event (OAE) 2 in the southern high latitudes
  • IP–1915–0619: Dr S Kender (Exeter) – Oceanographic and vegetation changes across the Palaeocene–Eocene Thermal Maximum in NW Europe and the Arctic
  • IP–1918–0619: Prof M Leng (Nottingham) – Stable C Isotope Analyses Coupled to XRF Core Scanning through a UK Black Shale Giant
  • IP–1924–0619: Dr J Pike (Cardiff) – Holocene diatom and sponge spicule oxygen isotope ratios from the west Antarctic Peninsula: exploring seasonal and depth related isotope offsets using paired samples
  • IP–1926–0619: Dr Z Shi (Birmingham) – Changing Shipping Emissions: Impact on sulphate Aerosol in the marine atmosphere (CSEIA)
  • IP–1927–0619: Prof G Shields (UCL) – Paleoceanographic context of organic matter deposition on the Yangtze craton, South China during the Ediacaran Period
  • IP–1929–0619: Dr M van Hardenbroek (Newcastle) – Iron Age Palaeoenvironments of North West Scotland (pilot)

March 2019: British Academy/Leverhulme Trust

Angela Lamb and Jane Evans, along with Richard Madgwick (University of Cardiff) have been awarded a British Academy/Leverhulme Trust small grant (supported by the Department for Business, Energy and Industrial Strategy and the Caton-Thompson Fund), entitled ‘Wet Feet: Developing sulphur isotope provenance methods to identify wetland inhabitants’. The project aims to refine our understanding of how sulphur isotopes can be used as an isotope fingerprinting tool for individuals living on Jurassic mudstones and/or wetland environments.

January 2019: Australian Research Council award

Congratulations to Melanie Leng for her contribution to the successful Australian Research Council grant: “East Australian climate extremes through the Holocene”. The project aims are to document climate variability in eastern Australia over the Holocene (the last ~11 500 years) and seeks to develop Australia’s two highest–resolution Holocene climate records using novel techniques (including isotopes) to infer past rainfall, temperature and evaporation. In particular the plan is to determine the frequency, duration and causes of megadroughts in eastern Australia, of which little is known. Expected project outcomes include improved decision making capacity for natural resource management, and planning. Mel is a Partner Investigator with the University of Adelaide Chief Investigators (Dr John Tibby and Dr Jonathan Tyler).

2019

December 2019: Suigetsu, Sediment and Silica: Embarking on my PhD: by Charlie Rex

Anyone who has started researching something new is well aware of the challenges involved: vast amounts of literature, creating sensible hypotheses and selecting a suitable methodology (among other hurdles!). For new PhD students, this can also involve a totally new setting, such as a new city, country, or continent. Thankfully I didn’t have to move continent, but I did make the move to Scotland and start fresh on a PhD topic that I found fascinating and unfamiliar in equal measure. Though this was daunting, I am incredibly fortunate to be surrounded by a multidisciplinary, multi-continental academic network who have helped me get off to a good start! Find out more about Charlie’s experience below.

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November 2019: Building Capacity for Archaeological Science in Turkey: by Emma Baysal and Holly Miller

Emma Baysal from Trakya University and Holly Miller of the University of Nottingham and BGS Visiting Research Fellow were awarded a Newton Advanced Fellowship. ‘Building Capacity for Sustainable Archaeological Science and Heritage in Turkey’ (NAFR1180204) promotes capacity building, education and training in the field of archaeological science in Turkey. This is the second in a series of three blogs that will discuss their initial three weeks of activities at BGS with guest researchers from Turkey.

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October 2019: BGS Wilding Group – Every Tree Counts

The BGS Keyworth based Wilding Group have been up and running for a few months now and over the course of a lunchtime each month we work on specific areas of our site to encourage wildlife and help increase biodiversity.

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October 2019: Newton Advanced Fellowship: BGS Training Program Week One… by Emma Baysal et al

Emma Baysal (Trakya University) and Holly Miller (University of Nottingham) were awarded a Newton Advanced Fellowship to promote capacity building, education and training in the field of archaeological science in Turkey. This is the first in a series of three blogs that will discuss their initial three weeks of activities at BGS, with guest researchers from Turkey.

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September 2019: Stable Isotope Mass Spectrometer User Group meeting 2019 by Rob Burton

The 15th SIMSUG meeting was hosted by the Organic Geochemistry Unit at the University of Bristol. SIMSUG offers a platform for innovations in stable isotope research methodology and analytical instrumentation to be communicated amongst members of the stable isotope community. Attendees at SIMSUG included delegates from research institutes, manufacturers and technical experts; each providing a unique contribution towards the wide-ranging spectrum of content.

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August 2019: Why we need a Geo-Observatory of Africa’s oldest lake by Melanie Leng

This summer, Melanie Leng (BGS’s Chief Scientist for Environmental Change Adaptation) attended a workshop in Dar es Saleem, Tanzania, with around 70 other scientists from 10 countries, with the aim to form a plan to create a palaeo Geo–Observatory in this region. The Geo–Observatory, in the form of a long sediment core, will contain information on past conditions in Lake Tanganyika and tropical East Africa. Here Melanie tells us about why we need to do research in this region and what happens next.

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March 2019: Homeward Bound: Last Leg of the ORCHESTRA Cruise (Part 4)… by Carol Arrowsmith

We were at sea for around eight weeks on the RRS James Clark Ross, undertaking the ANDREXII transect. We set off from the Punta Arenas, Chile, calling in at the Falklands before crossing the Drake Passage to the tip of the Antarctic Peninsula at 60oS, and then out along over 3000 miles to the Indian Ocean at 30oE. Find out more from Carol below.

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May 2019: Talking environmental change and human impact at EGU19… by Dr Jack Lacey

Dr Jack Lacey from the BGS Stable Isotope Facility attended EGU from April 7–12. Today he tells us about his week and the research he presented…

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May 2019: Latest Developments in Methane Isotope Analysis… by Andi Smith

Recent requirements for understanding methane formation processes has led to investment in a new stable isotope mass spectrometer by BGS. This instrument is specifically designed to analyse both carbon and hydrogen isotopes in water and gas samples and is perfectly set up to support large groundwater and soil gas surveys. As part of the launch of this equipment the stable isotope team including Prof. Melanie Leng and Dr Andi Smith went and presented the new instrumentation at European General Assembly last month.

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March 2019: Prehistoric Britons rack up food miles for feasts near Stonehenge

A collaboration between BGS (Angela Lamb, Jane Evans and Hilary Sloane) and scientists from Cardiff University, University of Sheffield and University College London has provided evidence of the earliest large-scale celebrations in Britain – with people and animals travelling hundreds of miles for prehistoric feasting rituals. The study, led by Dr Richard Madgwick of Cardiff University, is the most comprehensive to date and examined the bones of 131 pigs, the prime feasting animals, from four Late Neolithic (c. 2800-2400BC) complexes. Serving the world-famous monuments of Stonehenge and Avebury, the four sites – Durrington Walls, Marden, Mount Pleasant and West Kennet Palisade Enclosures – hosted the very first pan-British events, feasts that drew people and animals from across Britain. The isotope results show pig bones excavated from these sites were from animals raised as far away as Scotland, North East England and West Wales, as well as numerous other locations across the British Isles. The study, ‘Multi-isotope analysis reveals that feasts in the Stonehenge environs and across Wessex drew people and animals from throughout Britain’, was funded by the British Academy and NERC and is published in Science Advances.

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March 2019: Full steam ahead with the sampling on the RRS James Clark Ross: ORCHESTRA Part 3… by Carol Arrowsmith

We are now cruising along the 60oS latitude, having crossed the Drake Passage, passing Elephant Island (off the tip of the Antarctic Peninsula), between Coronation and Laurie Island and are now out in the Weddell Sea at approximately 23oW. This leg of the ORCHESTRA hydrographic/tracer section covers the northern rim of the Weddell Gyre and is called ANDREXII (Antarctic Deep Water Rates of Export). This leg was previously sampled 10 years ago so we are interested to see the difference global warming has made to the ocean. Carol is half way through a research cruise across the Weddell Sea as part of ORCHESTRA.

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March 2019: Tropical palaeoclimate meeting as temperatures break records in the UK… by Heather Moorhouse

In 2018, the UK NERC-funded collaborators of the International Continental scientific Drilling Program – DeepCHALLA project met in Cambridge amidst a Siberian blast, known as the ‘Beast from the East’, as temperatures plummeted and ice and snow disrupted UK travel. In 2019 however, the scientists met in tropical Lancaster, during maximum temperature records for the month of February. It is predicted that weather events will be increasingly unpredictable, variable and extreme, and the temperature differences between our two meetings merely serves to highlight the future under climate change.

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March 2019: From Chile to the Falklands and beyond: ORCHESTRA Part 2… by Carol Arrowsmith

I left the UK last Saturday and flew to Punta Arenas in Chile. There we waited (with various, BAS, NOC and university colleagues) to board the RRS James Clark Ross; a few days later we departed for the Falkland Islands. On board our first task was to lash down all the equipment in the ship’s laboratories needed for our sampling and familiarise ourselves with the layout of the ship. We have been accompanied for most of the journey so far by a variety of birds and mammals, including magnificent black-browed albatross, that mostly just sit in the water surrounding the ship waiting for food (to upwell from beneath the ship).

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February 2019: Investigating the Southern Ocean: Part 1… by Carol Arrowsmith

In a few days I will be embarking on my leg of the major NERC project called ORCHESTRA (Ocean Regulation of Climate through Heat and Carbon Sequestration and Transport) to collect seawater samples for isotope analysis. My leg is called ANDREX II – Antarctic Deep Water Rates of Export (ANDREX), and is the second time this part of the ocean has been sampled. I will be boarding the RRS James Clark Ross in Punta Arenas and following a stop off in the Falklands will start sampling from the tip of the Antarctic Peninsula along the 60°S parallel and across the Southern Ocean to 30°E, before returning to the Falklands in mid April.

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February 2019: BGS and Heriot–Watt Partnership in Action: Geochemistry and Carbon Burial at the BSRG AGM 2018… by Joe Emmings

In late December, Joe Emmings (BGS) and Tom Wagner (Heriot–Watt University) convened Geochemistry and Carbon Burial Sessions at the British Sedimentological Research Group (BSRG) AGM. Here Joe tells us about the conference and ongoing research in this area…

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February 2019: Can we use carbon isotopes to tell us about past levels of CO2 in the atmosphere?… by Barry Lomax and Melanie Leng

Dr Barry Lomax and Prof Melanie Leng are isotope geochemists who work on understanding how the isotopic composition of environmental materials can tell us about past environments. Here they blog about their new paper, available via open access in the premiere geochemistry journal (Geochimica et Cosmochimica Acta), co–authored by Dr Janice Lake and Dr Phillip Jardine on the use of carbon isotopes in plant materials to predict atmospheric CO2. The paper sets out to test this relationship to determine if it could be used as a tool for estimating changes in atmospheric CO2 concentrations through geological time.

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2019

November 2019: Congratulations to Savannah Worne on the successful defence of her PhD entitled Investigating Bering Sea oceanographic response to the Milankovitch orbital cycle climatic shift during the middle Pleistocene. Savannah wrote her thesis by paper and these have been published so far:

  • Worne, S, Kender, S, Swann, G E A, Leng, M J, and Ravelo, A C. 2019. Coupled climate and subarctic Pacific nutrient upwelling over the last 850 000 years. Earth and Planetary Science Letters. 522, 87–97.
  • Kender, S, Ravelo, A C, Worne, S, Swann, G E A, Leng, M J, Asahi, H, Becker, J, Detlef, H, Aiello, I W, Andreasen D, and Hall, I R. 2018. Closure of the Bering Strait caused Mid–Pleistocene Transition cooling. Nature Communications. 9, 5386.
  • Swann, G E A, Kendrick, C P, Dickson, A J, and Worne, S. 2018. Late Pliocene marine pCO2 reconstructions from the Subarctic Pacific Ocean. Paleoceanography and Paleoclimatology. 33, 457–469.

 

Savannah was supervised at Nottingham by Profs George Swann and Sarah Metcalfe, at Exeter by Dr Sev Kender and undertook her isotope analysis at BGS with Prof Melanie Leng.

June 2019: Congratulations to Elizabeth Atar on the successful defence of her PhD thesis entitled ‘Late Jurassic Sedimentation in the Boreal–Tethyan Seaway: climate modelling, geochemistry, and petrography of the Kimmeridge Clay Formation’

Climate exerts a strong influence on sedimentation. Understanding the processes behind the spatial and temporal heterogeneities in sedimentary successions can, therefore, be used to reconstruct climate processes in the geological past. Deposited across >1000 km in northwest Europe in the shallow (< 200 m), epicontinental Laurasian Seaway, the Kimmeridge Clay Formation provides an exceptional opportunity to study climate processes and their effect on sedimentation at different latitudes through the Late Jurassic (Kimmeridgian–Tithonian). This thesis presents independent climate modelling, sedimentological, and geochemical datasets from three time–equivalent sections, spanning 1 million years, in the northern and southern extents of the Laurasian Seaway (30–60°°N palaeo–latitude) in order to investigate climate dynamics and controls on sedimentation at different northern hemisphere latitudes in the Late Jurassic. The climate modelling results yield two different hypotheses: 1) HadCM3L indicates that an expanded Hadley Cell and migrated intertropical convergence zone resulted in tropical conditions over the Laurasian Seaway, whereby organic carbon-enrichment in sediments was promoted through enhanced nutrient supply resulting from continental weathering and erosion, and 2) FOAM suggests subtropical–temperate conditions prevailed and that organic carbon enrichment was driven by wind–driven upwelling of nutrient–rich water.

Sedimentological and geochemical analyses for the Ebberston 87 Core, drilled in the Cleveland Basin (Yorkshire, UK), indicates depositional conditions fluctuated between three distinct states and that alternations of organic carbon–rich, carbonate–rich, and clay–rich mudstone and redox conditions were driven by the expansion/migration of the intertropical convergence zone. Analysis of the Swanworth Quarry 1 Core, drilled in the Wessex Basin (Dorset, UK), reveals that although depositional energy differed between the Cleveland and Wessex Basins, sedimentation in both basins was driven by the same, over–arching tropical climate control. Analysis of a third core, drilled in Adventdalen (Svalbard), demonstrates that organic carbon–rich sedimentation occurred in a deltaic setting, which had a markedly higher depositional energy. While the depositional environments in the northern and southern sectors of the Laurasian Seaway differed substantially, similarities between the three studied sections, namely cyclical deposition of terrestrial organic carbon–rich and detrital–rich sedimentation, integrated with published data from throughout the seaway, suggest a low–latitude, tropical influence on sedimentation and organic carbon enrichment across the entire Laurasian Seaway. Furthermore, the palaeogeographic setting of the Laurasian Seaway made the sedimentary system sensitive to subtle changes in weathering and water depths, resulting in distinct modes of sedimentation and biogeochemical cycling.

June 2019: Congratulations to Katrina Kerr on the successful defence of her PhD thesis entitled ‘Reconstructing the Indian Summer Monsoon response to global climate change’

The Indian Summer Monsoon, a subsystem of the Asian Monsoon, is one of Earth’s most dynamic expressions of oceanic–atmospheric–terrestrial processes affecting some of Earth’s most densely populated regions. Therefore, it is imperative to have a comprehensive understanding of the Indian Summer Monsoon in order to understand how its behaviour may be manifested by anthropogenic induced climate changes. Reconstructing how the monsoon behaved in the past presents an opportunity to disentangle its sensitivities to a range of forcing parameters (e.g.ice volume) during periods of differing climatic states.

However, understanding of how the Indian Summer Monsoon behaved in the past has been limited both spatially and temporally, further constrained by discrepancies among climate proxy records. This work fills both a temporal and spatial gap in our knowledge of the past behaviour of the Indian Summer Monsoon. High–resolution (millennial to centennial scale) records of Indian Summer Monsoon induced river runoff and surface freshening from the core convective region of the Indian Summer Monsoon, the northern Bay of Bengal and Andaman Sea, have been generated from 70 to 140 thousand years ago. These records provide an insight into how the Indian Summer Monsoon responded to the penultimate deglaciation (Termination II), the subsequent warmth of the Last Interglacial Period and ensuing oscillations between the warm interstadial and cold stadial periods of Marine Isotope Stage 5. These records are compared with both high–latitude and low–latitude climate records in order to understand how the monsoon responded to changes in Earth’s internal climate system and the influence of external preconditioning

May 2019: Congratulations to Dr Stuart Young on the successful defence of his PhD thesis entitled: The ecology of immune variation in wild house mice (Mus musculus domesticus).

Stuart was supervised by Jan Bradley (University of Nottingham) and collaborated with Angela Lamb (BGS) on stable isotope analysis. Stuart is now working as a Programme Officer for the IUCN Asian Wild Cattle Specialist Group based at Chester Zoo. A paper on Stuart’s work has just been published in Functional Ecology:

Taylor, C H, Young, S, Fenn, J, Lamb, A L, Lowe, A E, Poulin, B, MacColl, A D C, and Bradley, J E. 2019. Immune state is associated with natural dietary variation in wild mice Mus musculus domesticus. Functional Ecology. doi: 10.1111/1365-2435.13354.

2019

December 2019: Scientific Reports

Navan Fort is an iconic prehistoric Irish ceremonial centre and the legendary capital of Ulster. The fort has produced an exceptional pig-dominated faunal assemblage that also contained a barbary macaque skull. Dating from the 4th to 1st century BC, it is likely to be a ceremonial feasting centre that may have drawn people and their animals from across Ulster and beyond. This study uses a multi–isotope (87Sr/86Sr, δ34S, δ13C, δ15N) approach to identify non-local animals and reconstruct site catchment. New biosphere mapping means that isotope data can be more confidently interpreted and the combination of strontium and sulphur analysis has the potential to estimate origins. In the absence of human remains, fauna provide the best proxy for human movement. Results for the 35 analysed animals are wide–ranging, especially in terms of strontium (0.707–0.715), which has the largest range for an Irish site. Sulphur values are more restricted (13.1‰–17.1‰) but are high in the context of British and Irish data. Results provide clear evidence for animals (and thus people) coming from across Ulster and beyond, demonstrating the site’s wide catchment. Navan Fort was clearly a major ceremonial centre with far-reaching influence and hosted feasts that drew people and animals from afar.

Madgwick, R, Grimes, V, and Lamb, A L. et al. 2019. Feasting and Mobility in Iron Age Ireland: Multi-isotope analysis reveals the vast catchment of Navan Fort, Ulster. Scientific Reports.

November 2019: Rapid Communications in Mass Spectrometry

Although the analysis of skeletal remains dominates the study of ancient dietary stable isotopes, mummified bodies also allow short–term diet to be studied through the analysis of soft tissues. The application of resins, waxes and oils during mummification can affect the results obtained. This study assesses a range of methods for removing such substances from mummified tissue. An experimental mummification model following ancient Egyptian methods was created using a modern pig leg. Sub-samples of skin, muscle and bone were removed and coated with a range of substances used in Egyptian mummification. Four methods were used to clean these samples before the measurement of the carbon and nitrogen stable isotope ratios of their gelatinised collagen content using a ThermoFinnigan Flash Elemental analyser coupled to a DeltaPlus XL isotope ratio mass spectrometer via a ConFlo III interface. The results showed that embalming materials can significantly affect dietary stable isotope ratios, and that these substances are most effectively removed using a mixture of polar and non–polar solvents. Results indicate that bone samples demineralised with HCl and skin samples produce more accurate results than bone samples demineralised with EDTA or muscle samples. The choice of tissue and the preparation methods used can have a significant effect on the accuracy of stable isotope data obtained from mummified tissue, particularly when embalming materials are also present. A mixture of solvents appears to be a more effective cleaning agent than a single solvent. Demineralisation with HCl is preferable for well–preserved bone as used in this study, but whether this is the case for more fragile, less well-preserved bone requires further study. Skin samples produce more consistent data than muscle, but visually distinguishing between these tissues is not simple on ancient mummies.

Cockitt, J, Lamb, A, and Metcalfe, R. 2019. An Ideal Solution? Optimising Pretreatment Methods for Artificially Mummified Ancient Egyptian Tissues. Rapid Communications in Mass Spectrometry.

November 2019: Palaeogeography, Palaeoclimatology, Palaeoecology

Early diagenetic redox oscillation processes have been rarely recognised in the ancient rock record but potentially exert an important control on mineral authigenesis, hydrocarbon prospectivity and supply of metals and/or reduced S as part of associated mineral systems. The upper unit of the Mississippian Bowland Shale Formation is a candidate record of diagenetic redox oscillation processes because it was deposited under a relatively high sediment accumulation rate linked to a large delta system, and under dominantly anoxic and intermittently sulphidic bottom-water conditions. In order to characterise the syngenetic and early diagenetic processes, sedimentological and geochemical data were integrated through the Upper Bowland Shale at three sites in the Craven Basin (Lancashire, UK). Organic matter (OM) comprises a mixture of Type II, II–S, II/III and III OM. ‘Redox zones’ are defined by patterns of Fe–speciation and redox–sensitive trace element enrichment and split into two groups. ‘Sulphidic’ zones (EUX, AN–III, AN–I and AN–IT) represent sediments deposited under conditions of at least intermittently active sulphate–reduction in bottom–waters. ‘Non–sulphidic’ zones (OX–RX, OX–F and OX) represent sediments deposited under non–sulphidic (oxic to ferruginous anoxic) bottom–waters. Operation of a shelf–to–basin ‘reactive Fe’ (FeHR) shuttle, moderated by sea level fluctuation and delta proximity, controlled the position and stability of redoxclines between zones of Fe and sulphate reduction, and methanogenesis. Early diagenetic redoxclines were capable of migration through the shallow sediment column relatively quickly, in response to sea level fluctuation. Preservation of syngenetic and early diagenetic geochemical signals shows redoxclines between Fe and sulphate reduction, and the upper boundary of sulphate-methane transition zone, were positioned within decimetres (i.e., 10s cm) of seabed. Falling sea level and increasing FeHR supply is recognised as a switch from zones EUX (high sea level), AN–III and ultimately AN–I and AN–IT (low sea level). Zone AN–I defines the operation of ‘redox oscillation’, between zones of Fe and sulphate reduction in shallow porewaters, associated with enhanced degradation of OM and complete dissolution of primary carbonate. Preservation of OM and carbonate, in this system, was a function of changing bottom and pore water redox processes. Redox oscillation operated in a siliciclastic, prodeltaic environment associated with a relatively high sediment accumulation rate and high loadings of labile organic matter and metal oxides. These findings are important for understanding Late Palaeozoic black shales in the context of hydrocarbon and mineral systems.

Emmings, J F, Poulton, S W, Vane, C H, Davies, S, Jenkin, G R T, Stephenson, M H, Leng, M J, Lamb, A, Moss-Hayes, V. 2019. A Mississippian black shale record of redox oscillation in the Craven Basin, UK. Palaeogeography, Palaeoclimatology, Palaeoecology, 109423.

November 2019: The Holocene

Norsminde Fjord has received extensive geoarchaeological investigation, hosting one of the classic Stone Age shell midden sites in Denmark, and one of the best examples of the widespread oyster decline at the Mesolithic–Neolithic transition. Here, intra–shell δ18O (and δ13C) analyses from the common periwinkle Littorina littorea (L.) are used to infer inter–annual environmental changes at the Mesolithic–Neolithic transition (four from each period). This study utilises a modern δ18O L. littorea–salinity training set previously developed for the Limfjord, Denmark to quantify winter salinity. δ18O values range between +1.6 per cent and +4.0 per cent in the late Mesolithic and ‒6.3 per cent to +2.0 per cent in the early Neolithic. Using maximum δ18O values, winter salinity at the known temperature of growth cessation in L. littorea (i.e. +3.7 ± 1°C) for the first annual cycle of each shell ranges between 25.5 and 26.8 psu (standard deviation (SD): 0.56) for the late Mesolithic, with an average salinity of 26.1 psu. Early-Neolithic shells range between 19.4 and 28.2 psu (SD: 4.59) with an average salinity of 23.7 psu. No statistically significant change in salinity occurs between the late Mesolithic and early Neolithic. This result supports recent diatom/mollusc-based inferences that salinity was not the sole cause of the oyster decline, although some evidence is presented here for more variable seasonal salinity conditions in the early Neolithic, which (along sedimentary change and temperature deterioration) might have increased stress on oyster populations in some years. It is recommended here that for robust palaeo-environmental inferences, where possible, multiple specimens should be used from the same time period in conjunction with multiproxy data.

Lewis, J P, Lamb, A L, Ryves, D B, Rasmussen, P, Leng, M J, Andersen, S H. 2019. δ18O–inferred salinity from Littorina littorea (L.) gastropods in a Danish shell midden at the Mesolithic–Neolithic transition. The Holocene.

October 2019: Rapid Communications in Mass Spectrometry

The isotopic composition of oxygen bound to phosphorus (δ18OP value) offers an opportunity to gain insight into P cycling mechanisms. However, there is little information for tropical forest soils, which present a challenge for δ18OP measurements due to low available P concentrations. Here we report the use of a rapid ammonium fluoride extraction method (Bray–1) as an alternative to the widely used anion–exchange membrane (AEM) method for quantification of δ18OP values of available P in tropical forest soils. We compared P concentrations and δ18OP values of available and microbial P determined by AEM and Bray–1 extraction for a series of tropical forest soils from Panama spanning a steep P gradient. This involved an assessment of the influence of extraction conditions, including temperature, extraction time, fumigation time, and solution-to-soil ratio, on P concentrations and isotope ratios. Depending on the extraction conditions, Bray–1 P concentrations ranged from 0.2 to 66.3 mg P kg–1 across the soils. Extraction time and temperature had only minor effects on Bray–1 P, but concentrations increased markedly as the solution-to-soil ratio increased. In contrast, extraction conditions did not affect Bray–1 δ18OP values, indicating that Bray–1 provides a robust measure of the isotopic composition of available soil P. For a relatively high P soil, available and fumigation-released (microbial) δ18OP values determined by Bray–1 extraction (20‰ and 16‰, respectively) were higher than those determined by AEM (18‰ and 12‰, respectively), which we attribute to slightly different P pools extracted by the two methods and/or differences resulting from the longer extraction time for the AEM method. The short extraction time, insensitivity to extraction conditions, and smaller mass of soil required to extract sufficient P for isotopic analysis, make Bray–1 extraction a suitable alternative to the AEM method for the determination of δ18OP values of available P in tropical soils.

Pfahler, V, Bielnicka, A, Smith, A C, Granger, S J, Blackwell, M S A, and Turner, B L. 2019. A rapid ammonium fluoride method to determine the oxygen isotope ratio of available phosphorus in tropical soils. Rapid Communications in Mass Spectrometry

October 2019: Rapid Communications in Mass Spectrometry

The suitability of organic matter (OM) removal pre-treatments in isotopic studies of lacustrine carbonates is currently under debate. Naturally occurring OM seems to have a negligible effect on the bulk isotopic composition of carbonates compared with changes induced by pre-treatments. This study provides further insights into the possible effects induced by commonly used pre-treatments on natural lacustrine carbonates. Sixteen samples from the Fucino F1–F3 lacustrine succession (Abruzzo, central Italy) were characterised for their mineralogical and geochemical composition and split in three identical aliquots. One aliquot was left untreated while the remaining two were treated with NaOCl and H2O2 dilutions. The same treatment was applied to an internal standard consisting of pure Carrara marble. The treated and untreated samples were analysed for their carbon (δ13C values) and oxygen (δ18O values) isotope compositions using an Analytical Precision AP2003 isotope ratio mass spectrometer. The samples had variable proportions of endogenic and detrital components, the detrital portion being more (less) abundant during colder (warmer) climate phases. We observed that neither the NaOCl nor the H2O2 treatment were able to completely remove OM and therefore there was selective removal of compounds within the OM pool. A possible effect of pre-treatment is the loss of carbonates intimately interspersed within the OM, as suggested by the evolution of isotopic ratios towards the local detrital array. Our study highlights sample–specific changes in geochemistry associated with sample pre-treatments; however, such changes do not seem to lead to either systematic and/or predictable isotopic shifts. We suggest that the suitability of NaOCl or H2O2 pre-treatments for OM removal should be evaluated on a case-by-case basis. In the specific case of lacustrine marls from palaeo-lake Fucino containing relatively low amounts of OM and in which both detrital and endogenic carbonates occur, both pre-treatments should be avoided.

Mannella, G, Zanchetta, G, Regattieri, E, et al. 2019. Effects of organic removal techniques prior to carbonate stable isotope analysis of lacustrine marls: a case study from palaeo–lake Fucino (central Italy). Rapid Commun Mass Spectrom.

September 2019: Nature

Mediterranean climates are characterised by strong seasonal contrasts between dry summers and wet winters. Changes in winter rainfall are critical for regional socioeconomic development, but are difficult to simulate accurately and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial–interglacial cycles 2,3 with different orbital geometries, global ice volume and atmospheric greenhouse gas concentrations are scarce. Moreover, the underlying mechanisms of change and their persistence remain unexplored. Here we show that, over the past 1.36 million years, wet winters in the north-central Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784 000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low–pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation. Our data cover multiple insolation maxima and are therefore an important benchmark for testing climate model performance.

Wagner, B, Vogel, H, Francke, A, Friedrich, T, Donders, T, Lacey, J H, Leng, M J, Regattieri, E, Sadori, L, Wilke, T, Zanchetta, G, Albrecht, C, Bertini, A, Combourieu–Nebout, N, Cvetkoska, A, Giaccio, B, Grazhdani, A, Hauffe, T, Holtvoeth, J, Joannin, S, Jovanovska, E, Just, J, Kouli, K, Kousis, I, Koutsodendris, A, Krastel, S, Lagos, M, Leicher, N, Levkov, Z, Lindhorst, K, Masi, A, Melles, M, Mercuri, A, Nomade, S, Nowaczyk, N, Panagiotopoulos, K, Peyron, O, Reed, J, Sagnotti, L, Sinopoli, G, Stelbrink, B, Sulpizio, R, Timmermann, A, Tofilovska, S, Torri, P, Wagner–Cremer, F, Wonik, T, and Zhang, X. 2019. Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years. Nature.

September 2019: Limnology and Oceanography Letters

Arctic lakes are poised for substantial changes to their carbon (C) cycles in the near future. Autochthonous processes in lakes which consume inorganic C and create biomass that can be sequestered in sediments are accompanied by allochthonous inputs of organic matter from the surrounding watershed. Both C sources can be mineralized and degassed as CO2, but also become recalcitrant and accumulate in pelagic waters. Using stable carbon isotope (δ13C) values and elemental ratios as geochemical proxies, we investigated diverse organic matter sources to lakes located across a hydro-climatic gradient in Southwest Greenland. Particulate organic matter (POM) and sediments were clearly of autochthonous algal origin, while dissolved organic matter (DOM) was a mix between autochthonous macrophytes and allochthonous watershed sources. Our results imply that a warmer and drier Arctic will lead to decoupled C pools: a water column dominated by increasingly autochthonous, macrophytic DOM, and sediments dominated by autochthonous algal POM.

Osburn, C L, Anderson, N J, Leng, M J, Barry, C D, and Whiteford, E J. 2019. Stable isotopes reveal independent carbon pools across an Arctic hydro–climatic gradient: Implications for the fate of carbon in warmer and drier conditions. Limnology and Oceanography Letters.

September 2019: The Holocene

The environmental ramifications of rapid development on the functioning of warm tropical freshwater ecosystems are poorly understood. Here, a multi–proxy palaeolimnological approach is used to examine the nature and degree of anthropogenic environmental change in a tropical lowland reservoir in Singapore. Singapore has undergone a dramatic transformation over the past century, transitioning from a country with a largely agrarian landscape to one that is highly urbanised. Two radiometrically dated sediment cores were retrieved from one of the country’s oldest reservoirs and analysed for spheroidal carbonaceous particles (SCPs), mercury (Hg), atomic carbon (C) and nitrogen (N), stable C and N isotopes (δ13C and δ15N), and diatoms. The sedimentary data show clear evidence of atmospheric pollution and nutrient enrichment as a result of human activities in Singapore and the region. During the early stages of Singapore’s development (1900s–1960s), the reservoir was minimally impacted and characterised by oligotrophic conditions. As the country began to industrialise and urbanise (1970s–1990s), the SCP data indicate increasing contamination by air pollutants derived from domestic sources of fossil fuel combustion, while the diatom, C/N, δ13C, and δ15N data suggest that the reservoir was becoming more productive, possibly from N depositions arising from an increase in electricity generation and a rapid expansion in transport infrastructure in Singapore. As the pace of development in Singapore slowed down (1990s–the present), the sedimentary data collectively indicate increasing depositions of atmospheric pollutants and nutrient enrichment mediated by a warming climate. A substantial component of increased atmospheric pollution is likely to be of distal, and thus transboundary, origin.

Fong, L S, Leng, M J, and Taylor, D. 2019. A century of anthropogenic environmental change in tropical Asia: Multi–proxy palaeolimnological evidence from Singapore’s Central Catchment. The Holocene.

August 2019: Climate of the Past

The Kimmeridge Clay Formation (KCF) is a laterally extensive, total-organic-carbon-rich succession deposited throughout northwest Europe during the Kimmeridgian–Tithonian (Late Jurassic). It has recently been postulated that an expanded Hadley cell, with an intensified but alternating hydrological cycle, heavily influenced sedimentation and total organic carbon (TOC) enrichment by promoting primary productivity and organic matter burial in the UK sectors of the Boreal Seaway. Consistent with such climate boundary conditions, petrographic observations, total organic carbon and carbonate contents, and major and trace element data presented here indicate that the KCF of the Cleveland Basin was deposited in the Laurasian Seaway under the influence of these conditions. Depositional conditions alternated between three states that produced a distinct cyclicity in the lithological and geochemical records: lower–variability mudstone intervals (LVMIs) which comprise clay-rich mudstone and higher-variability mudstone intervals (HVMIs) which comprise TOC-rich sedimentation and carbonate-rich sedimentation. The lower-variability mudstone intervals dominate the studied interval but are punctuated by three ∼ 2–4 m thick intervals of alternating TOC-rich and carbonate-rich sedimentation (HVMIs). During the lower-variability mudstone intervals, conditions were quiescent with oxic to suboxic bottom water conditions. During the higher-variability mudstone intervals, highly dynamic conditions resulted in repeated switching of the redox system in a way similar to the modern deep basins of the Baltic Sea. During carbonate-rich sedimentation, oxic conditions prevailed, most likely due to elevated depositional energies at the seafloor by current-wave action. During TOC-rich sedimentation, intermittent anoxic-euxinic conditions led to an enrichment of redox-sensitive and sulfide-forming trace metals at the seafloor and a preservation of organic matter, and an active Mn–Fe particulate shuttle delivered redox-sensitive and sulfide-forming trace metals to the seafloor. In addition, based on TOC-S-Fe relationships, organic matter sulfurisation appears to have increased organic material preservation in about half of the analysed samples throughout the core, while the remaining samples were either dominated by excess Fe input into the system or experienced pyrite oxidation and sulfur loss during oxygenation events. New Hg∕TOC data do not provide evidence of increased volcanism during this time, consistent with previous work. Set in the context of recent climate modelling, our study provides a comprehensive example of the dynamic climate-driven depositional and redox conditions that can control TOC and metal accumulations in a shallow epicontinental sea, and it is therefore key to understanding the formation of similar deposits throughout Earth’s history.

Atar, E, Marz, C, Aplin, A, Dellwig, O, Herringshaw, L, Lamoureux-Var, V, Leng, M J, Schnetger, B, and Wagner, T. 2019. Dynamic climate-driven controls on the deposition of the Kimmeridge Clay Formation in the Cleveland Basin, Yorkshire, UK. Climate of the Past.

September 2019: Marine Geology

We assessed the use of δ13C, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of δ13C, TOC and C/N values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands, and was compared to microfossil (foraminiferal and thecamoebian) assemblages. Four vertically zoned environments were identified:

  • tidal flat (δ13C: –18.6 ± 2.8‰; TOC: 10.2 ± ;5.7%; C/N: 12.7 ± 3.1)
  • mangrove (δ13C: –26.4 ± 1.0‰; TOC: 33.9 ± 13.4%; C/N: 24.3 ± 6.2)
  • brackish transition (δ13C: –28.8 ± 0.7‰; TOC: 40.8 ± 11.7%; C/N: 21.7 ± 3.7)
  • freshwater swamp (δ13C: –28.4 ± 0.4‰; TOC: 42.8 ± 4.8%; C/N: 17.0 ± 1.1)

These environments had distinct δ13C, TOC and C/N values, with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone. The foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water (MHHW), likely resulting from washover or transport by storms. However, the ratio of foraminifera to thecamoebians (F/T) along with δ13C, TOC and C/N values refines the distinction between brackish and freshwater environments. Using linear discriminant analysis, we applied the δ13C, TOC, C/N and F/T distributions to a 1.7 m core containing a continuous sequence of Rhizophora mangle peat, which began accumulating at ~1650–1930 CE. Together, microfossils, δ13C, TOC, and C/N values, and the core chronology from 137Cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery, making it unsuitable for relative sea-level reconstruction. We caution that in the absence of detailed litho-, bio-, chemo-, or chrono-stratigraphic analyses as presented here, care should be taken in interpreting sea-level histories derived from single dates on mangrove peats.

Khan, N S, Vane, C H, Engelhart, S E, Kendrick, C, and Horton, B P. 2019. The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico. Marine Geology.

August 2019: Archaeological and Anthropological Sciences

The geographic origins of livestock found at the Late Neolithic site of Durrington Walls (Wiltshire, UK) is explored using strontium (87Sr/86Sr) and oxygen (δ18OcarbVSMOW) isotope analysis of tooth enamel as an archive of lifetime movement. The analysis of 49 cattle is augmented with data for small numbers of animals from the contemporaneous monumental centres of West Kennet Palisade Enclosures (4), Stonehenge (1), and Marden (1). Unburnt human remains are scarce at these sites and the suite of biomolecular analyses that can be undertaken on cremated remains is limited. Therefore, these animals provide the best proxy for the origins of the people who raised them and give key information on livestock management. This builds on the Sr isotope analysis of 12 animals previously published from Durrington Walls and complements recent research on pig remains from the same sites, providing further evidence for the scale of human and animal movement and the catchment of these sites. The strontium isotope signatures from the animals’ teeth range between values that are consistent with local chalkland grazing to radiogenic values typical of granites and older rock types. The oxygen isotope data, coupled with the strontium results, provide new geographic resolution and indicate that the majority of the animals come from southern and western areas of Britain.

Evans, J, Parker Pearson, M, Madgwick, R, Sloane, H, and Albarella, U. 2019. Strontium and oxygen isotope evidence for the origin and movement of cattle at Late Neolithic Durrington Walls, UK. Archaeological and Anthropological Sciences.

July 2019: Earth and Planetary Science Letters

High latitude deep water upwelling has the potential to control global climate over glacial timescales through the biological pump and ocean–atmosphere CO2 exchange. However, there is currently a lack of continuous long nutrient upwelling records with which to assess this mechanism. Here we present geochemical proxy records for nutrient upwelling and glacial North Pacific Intermediate Water (GNPIW) formation in the Bering Sea over the past 850 kyr, which demonstrates that glacial periods were characterised by reduced nutrient upwelling, when global atmospheric CO2 and temperature were also lowered. We suggest that glacial expansion of sea ice in the Bering Sea, and the simultaneous expansion of low nutrient GNPIW, inhibited vertical mixing and nutrient supply across the subarctic Pacific Ocean. Our findings lend support to the suggestion that high latitude sea ice and the resultant intermediate water formation, modulated deep water upwelling and ocean–atmosphere CO2 exchange on glacial-interglacial timescales.

Worne, S, Kender, S, Swann, E A, Leng, M J, and Ravelo, A C. 2019. Coupled climate and subarctic Pacific nutrient upwelling over the last 850 000 years. Earth Planetary Science Letters.

July 2020: Quaternary Science Reviews

The Western Irish Sea preserves an exceptionally thick (ca. 40 m) Holocene succession that is ideally suited to understanding the pattern of palaeostratification and water mass productivity changes in the region, and their relationship with sea level, sedimentation, and biota. Additionally, the presence of shallow-buried methane provides an opportunity to explore its potential impact on the local pattern of Holocene marine environmental change. Multi-proxy investigation of a cored borehole succession through the Holocene interval tracks changes from mixed to seasonally stratified conditions. In the earliest Holocene (11.2–10 ka), high productivity, mixed water conditions prevailed, with abundant and diverse foraminifera and dominant heterotrophic dinoflagellate cysts. Productivity was probably driven by high nutrient fluxes related to high rates of sedimentation (>1600 cm/kyr), in turn influenced by relatively low sea level and restricted sediment accommodation space across shelf areas to the east of the borehole site (eastern Irish Sea Basin). With rising sea level in the later part of the Early Holocene, the region evolved into a relatively lower productivity mixed water mass system, with significant changes in ecology revealed by dinoflagellate cysts and foraminifera. In the latest Early Holocene and earliest Mid Holocene (ca. 8.4–8.2 ka) a return to higher productivity is signalled by dinoflagellate cyst data; a result of seasonal stratification becoming established, evidenced by sharply increased summer sea surface temperature estimates (typically 16–17 °C) that contrast with an opposite (more positive) trend in δ18O values for benthic foraminifera. Reductions in turbulent mixing associated with stratification might have exacerbated the palaeoecological impact of shallow-buried methane associated with the borehole site, potentially evidenced by a significant change in dominant benthic foraminifera and strong, localised excursions in the benthic δ13C/δ18O record.

Woods, M A, Wilkinson, I P, Leng, M J, Riding, J B, Vane, C H, Lopes dos Santos, R A, Kender, S, De Schepperd, S, Hennissen, J A I, Ward, S L, Gowing, C J B, Wilby, P R, Nichols, M D, and Rochelle, C A. 2019. Tracking Holocene palaeostratification and productivity changes in the Western Irish Sea: A multi–proxy record. Palaeogeography, Palaeoclimatology, Palaeoecology.

May 2019: PLOS One

Methods of reconstructing changes in plant traits over long time scales are needed to understand the impact of changing environmental conditions on ecosystem processes and services. Although Holocene pollen have been extensively used to provide records of vegetation history, few studies have adopted a functional trait approach that is pertinent to changes in ecosystem processes. Here, for woody and herbaceous fen peatland communities, we use modern pollen and vegetation data combined with pollen records from Holocene deposits to reconstruct vegetation functional dynamics. The six traits chosen (measures of leaf area-to-mass ratio and leaf nutrient content) are known to modulate species’ fitness and to vary with changes in ecosystem processes. We fitted linear mixed effects models between community weighted mean (CWM) trait values of the modern pollen and vegetation to determine whether traits assigned to pollen types could be used to reconstruct traits found in the vegetation from pollen assemblages. We used relative pollen productivity (RPP) correction factors in an attempt to improve this relationship. For traits showing the best fit between modern pollen and vegetation, we applied the model to dated Holocene pollen sequences from Fenland and Romney Marsh in eastern and southern England and reconstructed temporal changes in trait composition. RPP adjustment did not improve the linear relationship between modern pollen and vegetation. Leaf nutrient traits (leaf C and N) were generally more predictable from pollen data than mass-area traits. We show that inferences about biomass accumulation and decomposition rates can be made using Holocene trait reconstructions. While it is possible to reconstruct community-level trends for some leaf traits from pollen assemblages preserved in sedimentary archives in wetlands, we show the importance of testing methods in modern systems first and encourage further development of this approach to address issues concerning the pollen-plant abundance relationship and pollen source area.

Carvalho, F, Brown, K A, Waller, M P, Bunting, M J, Boom, A, et al. 2019. A method for reconstructing temporal changes in vegetation functional trait composition using Holocene pollen assemblages. PLOS ONE 14(5).

June 2019: Palaeontology

The species of the brachiopod Gigantoproductus are giants within the Palaeozoic sedentary benthos. This presents a dilemma as living brachiopods have low‐energy lifestyles. Although brachiopod metabolic rates were probably higher during the Palaeozoic than today, the massive size reached by species of Gigantoproductus is nevertheless unusual. By examining the diet of Gigantoproductus species from the Visean (Mississippian, Carboniferous) of Derbyshire (UK), we seek to understand the mechanisms that enabled those low-metabolism brachiopod species to become giants. Were they suspension feeders, similar to all other brachiopods, or did endosymbiosis provide a lifestyle that allowed them to have higher metabolic rates and become giants? We suggest that the answer to this conundrum may be solved by the identification of the biogeochemical signatures of symbionts, through combined analyses of the carbon and nitrogen‐isotopic compositions of the occluded organic matrix within their calcite shells. The shells are formed of substructured columnar units that are remarkably long and a few hundreds of microns wide, deemed to be mostly pristine based on multiple analyses (petrography, cathodoluminescence (CL), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM)); they contain occluded organic fractions detected by TEM, nuclear magnetic resonance (NMR) and gas chromatography mass spectrometry (GC–MS) analyses. We conclude that the gigantic size reached by the species of Gigantoproductus is probably the result of a mixotroph lifestyle, by which they could rely on the energy and nutrients derived both from photosymbiotic microbes and from filtered particulate food.

Angiolini, L, Crippa, G, Azmy, K, Capitani, G, Confalonieri, G, Della Porta, G, Griesshaber, E, Harper, D A, Leng, M J, Nolan, L, Orlandi, M, Posenato, R, Schmahl, W W, Banks, V J, and Stephenson, M H. 2019. The giants of the phylum Brachiopoda: a matter of diet? Palaeontology.

April 2019: Functional Ecology

  1. The ability, propensity and need to mount an immune response vary both among individuals and within a single individual over time
  2. A wide array of parameters have been found to influence immune state in carefully controlled experiments, but we understand much less about which of these parameters are important in determining immune state in wild populations
  3. Diet can influence immune responses, for example when nutrient availability is limited. We therefore predict that natural dietary variation will play a role in modulating immune state, but this has never been tested
  4. We measured carbon and nitrogen stable isotope ratios in an island population of house mice Mus musculus domesticus as an indication of dietary variation, and the expression of a range of immune related genes to represent immune state
  5. After accounting for potential confounding influences such as age, sex and helminth load, we found a significant association between carbon isotope ratio and levels of immune activity in the mesenteric lymph nodes, particularly in relation to the inflammatory response
  6. This association demonstrates the important interplay between diet and an animal’s response to immune challenges, and therefore potentially its susceptibility to disease

Taylor, C H, Young, S, Fenn, J, Lamb, A L, Lowe, A E, Poulin, B, MacColl, A D C, and Bradley, J E. 2019. Immune state is associated with natural dietary variation in wild mice Mus musculus domesticus. Functional Ecology.

April 2019: Paleoceanography and Paleoclimatology

The Late Cretaceous–Early Paleogene is the most recent period in Earth history that experienced sustained global greenhouse warmth on multi-million year timescales. Yet, knowledge of ambient climate conditions and the complex interplay between various forcing mechanisms are still poorly constrained. Here we present a 14.75 million-year-long, high-resolution, orbitally tuned record of paired climate change and carbon–cycling for this enigmatic period (~67–52 Ma), which we compare to an up–to–date compilation of atmospheric pCO2 records. Our climate and carbon-cycling records, which are the highest resolution stratigraphically complete records to be constructed from a single marine site in the Atlantic Ocean, feature all major transient warming events (termed ‘hyperthermals’) known from this time period. We identify eccentricity as the dominant pacemaker of climate and the carbon cycle throughout the Late Maastrichtian to Early Eocene, through the modulation of precession. On average, changes in the carbon cycle lagged changes in climate by ~23 000 years at the long eccentricity (405000-year) band, and by ~3000–4500 years at the short eccentricity (100 000-year) band, suggesting that light carbon was released as a positive feedback to warming induced by orbital forcing. Our new record places all known hyperthermals of the Late Maastrichtian–Early Eocene into temporal context with regards to evolving ambient climate of the time. We constrain potential carbon cycle influences of Large Igneous Province volcanism associated with the Deccan Traps and North Atlantic Igneous Province, as well as the sensitivity of climate and the carbon–cycle to the 2.4 million-year-long eccentricity cycle.

Barnet, J S K, Littler, K, Westerhold, T, Kroon, D, Leng, M J, Bailey, I, Röhl, U, and Zachos, J C. 2019. A High–Fidelity Benthic Stable Isotope Record of Late Cretaceous–Early Eocene Climate Change and Carbon–Cycling. Paleoceanography and Paleoclimatology.

April 2019: Global and Planetary Change

Understanding the evolution of soil systems on geological time scales has become fundamentally important to predict future landscape development in light of rapid global warming and intensifying anthropogenic impact. Here, we use an innovative uranium isotope-based technique combined with organic carbon isotopes and elemental ratios of sediments from Lake Ohrid (North Macedonia/Albania) to reconstruct soil system evolution in the lake’s catchment during the last ~16 000 cal yr BP. Uranium isotopes are used to estimated the paleo-sediment residence time, defined as the time elapsed between formation of silt and clay sized detrital matter and final deposition. The chronology is based on new cryptotephra layers identified in the sediment sequence. The isotope and elemental data are compared to sedimentary properties and pollen from the same sample material to provide a better understanding of past catchment erosion and landscape evolution in the light of climate forcing, vegetation development, and anthropogenic land use.

During the Late Glacial and the Early Holocene, when wide parts of the catchment were covered by open vegetation, wetter climates promoted the mobilisation of detrital matter with a short paleo-sediment residence time. This is explained by erosion of deeper parts of the weathering horizon from thin soils. Detrital matter with a longer paleo-sediment residence time, illustrating shallow erosion of thicker soils is deposited in drier climates. The coupling between climatic variations and soil erosion terminates at the Early to Mid-Holocene transition as evidenced by a pronounced shift in uranium isotope ratios indicating that catchment erosion is dominated by shallow erosion of thick soils only. This shift suggests a threshold is crossed in hillslope erosion, possibly as a result of a major change in vegetation cover preventing deep erosion of thin soils at higher elevation. The threshold in catchment erosion is not mirrored by soil development over time, which gradually increases in response to Late Glacial to Holocene warming until human land use during the Late Holocene promotes reduced soil development and soil degradation. Overall, we observe that soil system evolution is progressively controlled by climatic, vegetation, and eventually by human land use over the last ~16 000 years.

Francke, A, Dosseto, A, Panagiotopoulos, K, Leicher, N, Lacey, J H, Kyrikou, S, Wagner, B, Zanchetta, G, Kouli, K, and Leng, M J. 2019. Sediment residence time reveals Holocene shift from climatic to vegetation control on catchment erosion in the Balkans. Global and Planetary Change.

March 2019: Nature Geoscience

The responses of Asian monsoon subsystems to both hemispheric climate forcing and external orbital forcing are currently issues of vigorous debate. The Indian summer monsoon is the dominant monsoon subsystem in terms of energy flux, constituting one of Earth’s most dynamic expressions of ocean-atmosphere interactions. Yet, the Indian summer monsoon is grossly under-represented in Asian monsoon palaeoclimate records. Here, we present high-resolution records of Indian summer monsoon-induced rainfall and fluvial runoff recovered in a sediment core from the Bay of Bengal across Termination II, 139–127 thousand years ago, including coupled measurements of the oxygen isotopic composition and Mg/Ca, Mn/Ca, Nd/Ca and U/Ca ratios in surface-ocean-dwelling foraminifera. Our data reveal a millennial-scale transient strengthening of the Asian monsoon that punctuates Termination II associated with an oscillation of the bipolar seesaw. The progression of deglacial warming across Termination II emerges first in the Southern Hemisphere, then the tropics in tandem with Indian summer monsoon strengthening, and finally the Northern Hemisphere. We therefore suggest that the Indian summer monsoon was a conduit for conveying Southern Hemisphere latent heat northwards, thereby promoting subsequent Northern Hemisphere deglaciation.

Neilsson–Kerr, K, Anand, P, Sexton, P F, Leng, M J, Misra, S, Clemens, S C, and Hammond, S J. 2019. Role of Asian summer monsoon subsystems in the inter–hemispheric progression of deglaciation. Nature Geoscience.

March 2019: Science Advances

The great henge complexes of southern Britain are iconic monuments of the third millennium BCE, representing great feats of engineering and labor mobilisation that hosted feasting events on a previously unparalleled scale. The scale of movement and the catchments that the complexes served, however, have thus far eluded understanding. Presenting the largest five–isotope system archeological dataset (87Sr/86Sr, δ34S, δ18O, δ13C, and δ15N) yet fully published, we analyze 131 pigs, the prime feasting animals, from four Late Neolithic (approximately 2800 to 2400 BCE) complexes to explore the networks that the feasts served. Because archeological evidence excludes continental contact, sources are considered only in the context of the British Isles. This analysis reveals wide-ranging origins across Britain, with few pigs raised locally. This finding demonstrates great investment of effort in transporting pigs raised elsewhere over vast distances to supply feasts and evidences the very first phase of pan-British connectivity.

Madgwick, R, Lamb, A L, Sloane,H, Nederbragt, A J, Albarella, U, Parker Pearson, M, and Evans, J A. 2019. Multi-isotope analysis reveals that feasts in the Stonehenge environs and across Wessex drew people and animals from throughout Britain. Science Advances, 5 (3), eaau6078.

March 2019: Journal of human evolution

This study assesses the seasonal scheduling of shellfish harvesting among hunter-gatherer populations along the southernmost coast of South Africa, based on a large number of serial oxygen isotope analyses of marine mollusc shells from four archaeological sites. The south coast of South Africa boasts an exceptional record of coastal hunter-gatherer occupation spanning the Holocene, the last glacial cycle and beyond. The significance of coastal adaptations, in this region in particular, for later modern human evolution has been prominently debated. Shellfishing behaviours are an important focus for investigation given the dietary and scheduling implications and the abundant archaeological shell remains in numerous sites. Key to better understanding coastal foraging is whether it was limited to one particular season, or year-round. Yet, this has proven very difficult to establish by conventional archaeological methods. This study reconstructs seasonal harvesting patterns by calculating water temperatures from the final growth increment of shells. Results from two Later Stone Age sites, Nelson Bay Cave (together with the nearby Hoffman’s Robberg Cave) and Byneskranskop 1, show a pronounced cool season signal, which is unexpected given previous ethnographic documentation of summer as the optimal season for shellfishing activities and inferences about hunter-gatherer scheduling and mobility in the late Holocene. Results from two Middle Stone Age sites, Klasies River and Pinnacle Point 5–6, show distinct seasonal patterns that likely reflect the seasonal availability of resources in the two locations. The Pinnacle Point 5–6 assemblage, which spans the MIS5–4 transition, records a marked shift in shellfishing seasonality at c. 71 ka that aligns with other indications of archaeological and environmental change at this time. We conclude that the scheduling and intensity of shellfishing in this region is affected by a suite of factors, including environmental and cultural drivers, rather than a single variable, such as population growth.

Lomax, B H, Lake, J A, Leng, M J, and Jardine, P E. 2019. An experimental evaluation of the use of δ13C as a proxy for palaeoatmospheric CO2. Geochimica et Cosmochimica Acta 247, 162–174.

February 2019: Geochimica et Cosmochimica Acta

Understanding changes in atmospheric CO2 over geological time via the development of well constrained and tested proxies is of increasing importance within the Earth sciences. Recently a new proxy (identified as the C3 proxy) has been proposed that is based on the relationship between CO2 and carbon isotope discrimination (δ13C) of plant leaf tissue. Initial work suggests that this proxy has the capacity to deliver accurate and potentially precise palaeo–CO2 reconstructions through geological time since the origins of vascular plants (~450 Mya). However, the proposed model has yet to be fully validated through independent experiments. Using the model plant Arabidopsis thaliana exposed to different watering regimes and grown over a wide range of CO2 concentrations (380, 400, 760, 1000, 1200, 1500, 2000 and 3000 ppm) relevant to plant evolution we provide an experimental framework that allows for such validation. Our experiments show that a wide variation in δ13C as a function of water availability is independent of CO2 treatment. Validation of the C3 proxy was undertaken by comparing growth CO2 to estimates of CO2 derived from δ13C. Our results show significant differences between predicted and observed CO2 across all CO2 treatments and water availabilities, with a strong under prediction of CO2 in experiments designed to simulate Cenozoic and Mesozoic atmospheric conditions (≥1500 ppm). Further assessment of δ13C to predict CO2 was undertaken using Monte Carlo error propagation. This suite of analysis revealed a lack of convergence between predicted and observed CO2. Collectively these findings suggest that the relationship between δ13C and CO2 is poorly constrained. Consequently the use of δ13C as a proxy to reconstruct palaeoatmospheric CO2 is of limited use as the estimates of CO2 are not accurate when compared to known growth conditions.

Lomax, B H, Lake, J A, Leng, M J, and Jardine, P E. 2018. An experimental evaluation of the use of d13C as a proxy for palaeoatmospheric CO2. Geochimica et Cosmochimica Acta. In Press.

February 2019: Palaios

Plio-Pleistocene mass extinction of marine bivalves on the US eastern seaboard has been attributed to declines in temperature and primary production. We investigate the relationship of growth rate in the scallop Carolinapecten eboreus to variation in these parameters to determine which contributed to its extinction. We use ontogenetic profiles of shell δ18O to estimate growth rate and seasonal temperature, microgrowth-increment data to validate δ18O-based figures for growth rate, and shell δ13C to supplement assemblage evidence of production. Post–larval growth started in the spring/summer in individuals from the Middle Atlantic Coastal Plain but in the autumn/winter in some from the Gulf Coastal Plain. Growth rate typically declined with age and was usually higher in summer than winter. Many individuals died in winter but the largest forms typically died in spring, possibly on spawning for the first time. No individuals lived longer than two years and some grew exceedingly fast overall, up to 60 per cent more rapidly than any other scallop species (<145.7 mm in a year). Faster growth was generally achieved by secreting more rather than larger microgrowth increments. Some very fast growing individuals lived in settings of high production and low temperature. No individuals grew slowly under high production whereas most if not all grew slowly under ‘average’ production and low temperature. In that the rapid growth evidently enabled by high production would have afforded protection from predators, Plio-Pleistocene decline in production was probably contributory to the extinction of C. eboreus. However, the negative impact of low temperature on growth under ‘average’ production suggests that temperature decline played some part.

Johnson, A L A, Valentine, A M, Leng, M J, Schone, B R, and Sloane, H J. 2019. Life history, environment and extinction of the scallop Carolinapecten eboreus (Conrad) in the Plio-Pleistocene of the US Eastern seaboard. Palaios, 34, 49–70.

February 2019: Scientific Reports

The La Niña and El Niño phases of the El Niño-Southern Oscillation (ENSO) have major impacts on regional rainfall patterns around the globe, with substantial environmental, societal and economic implications. Long-term perspectives on ENSO behaviour, under changing background conditions, are essential to anticipating how ENSO phases may respond under future climate scenarios. Here, we derive a 7700-year, quantitative precipitation record using carbon isotope ratios from a single species of leaf preserved in lake sediments from subtropical eastern Australia. We find a generally wet (more La Niña-like) mid-Holocene that shifted towards drier and more variable climates after 3200 cal. yr BP, primarily driven by increasing frequency and strength of the El Niño phase. Climate model simulations implicate a progressive orbitally-driven weakening of the Pacific Walker Circulation as contributing to this change. At centennial scales, high rainfall characterised the Little Ice Age (~1450–1850 CE) in subtropical eastern Australia, contrasting with oceanic proxies that suggest El Niño-like conditions prevail during this period. Our data provide a new western Pacific perspective on Holocene ENSO variability and highlight the need to address ENSO reconstruction with a geographically diverse network of sites to characterise how both ENSO, and its impacts, vary in a changing climate.

Barr, C, Tibby, J, Leng, M J, Tyler, J J, Henderson, A C G, Overpeck, J T, Simpson, G L, Cole, J E, Phipps, S J, Marshall, J C, McGregor, G G, Hua, Q, and McRobie, F H. 2019. Holocene El Niño–Southern Oscillation variability reflected in subtropical Australian precipitation. Scientific Reports, 9, 1627.

January 2019: Book Chapter

The southern Red Sea coast is the location of more than 4200 archaeological shell midden sites. These shell middens preserve archaeological and climatic archives of unprecedented resolution and scale. By using shells from these contexts it is possible to link past environmental information with episodes of human occupation and resource processing. This chapter summarises current knowledge about the marine gastropod Conomurex fasciatus (Born 1778) and discusses its use in environmental and climatic reconstruction using stable isotope and elemental ratio analysis. It offers a review of the most recent studies of shell midden sites on the Farasan Islands, their regional importance during the mid-Holocene, theories about seasonal use of the coastal landscape, and preliminary results from new methods to acquire large climatic datasets from C. fasciatus shells.

Hausmann, H, Kokkinaki, O, and Leng, M J. 2019. Red Sea Palaeoclimate: stable isotope and element–ratio analysis of marine mollusc shells. In: Rasul, N M A, and Stewart, I C F (eds.), Geological Setting, Palaeoenvironment and Archaeology of the Red Sea, Springer.

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Contact Béatrice Bullock-von Moos for further information about the Stable isotope facility.

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