Pliocene sclerochronology

Queen scallop showing microgrowth

BGS climate change scientists and partners have been studying the shells of a modern-day bivalve (known as the Queen Scallop, Aequipecten opercularis) and a fossil bivalve (Arctica islandica) using a technique called sclerochronology.

The modern shells have been compared to fossil shells from the Coralline Crag Formation of Suffolk, eastern England, to see how the marine environment has changed over the last 3.5 million years (since the Pliocene).

The Pliocene is thought to have been a much warmer world shortly before the onset of a major glaciation of the northern-hemisphere. During this time, there was substantial variation in oceanic heat supply to the north-east Atlantic region.

By understanding these variations, future changes in the climate can be understood and, in particular, the future behaviour of the Gulf Stream in response to global warming.

What is sclerochronology?

Bivalve cross section

As plants and animals grow, the hard tissues, e.g. shells, bones or wood, have a physical and chemical 'signature' relating to the environment in which they lived. Sclerochronology is the study of these changing signatures over time.

Results

Results from this study have shown:

  • The seasonal range of temperatures on the seafloor during the middle of the Pliocene was less than in the present-day in the southern North Sea. The temperature at the bottom of the sea during winter was probably about the same as at present, while summer seafloor temperature was probably lower.
  • The seasonal range in temperature of the sea surface was higher during the middle of the Pliocene than in the southern North Sea at present.
  • While the middle Pliocene climate was warmer than now in summer, this state alternated with year-round warming.
  • The cause of fluctuations in climate state may have been due to variation in heat supply from the Gulf Stream. This may mean that we see similar temperature fluctuations with future climate change in the UK.

Further information

Johnson, A. L. A., Hickson, J. A., Bird, A., Schöne, B. R., Balson, P. S., Heaton, T. H. E. and Williams, M. (2009) Comparative sclerochronology of modern and mid-Pliocene (c. 3.5 Ma) Aequipecten opercularis (Mollusca, Bivalvia): an insight into past and future climate change in the north-east Atlantic region, Palaeogeography Palaeoclimatology Palaeoecology, v284, issue 3-4, p164-179.

Further reading:

Dowsett HJ, Chandler MA, Robinson MM (2009) Surface temperatures of the Mid-Pliocene North Atlantic Ocean: implications for future climate. Phil. Trans. Roy. Soc. A367, 69-84.

Johnson ALA, Hickson JA, Swan J, Brown MR, Heaton THE, Balson PS, Chenery S (2000) The Queen Scallop Aequipecten opercularis: a new source of information on late Cenozoic marine environments in Europe. 425-439 in Harper EM, Taylor JD, Crame JA (eds) The Evolutionary Biology of the Bivalvia, Geological Society, London.

Williams M, Haywood AM, Harper EM, Johnson ALA, Knowles T, Leng MJ, Lunt DJ, Okamura B, Taylor PD, Zalasiewicz J (2009) Pliocene climate and seasonality in North Atlantic shelf seas. Phil. Trans. Roy. Soc. A367, 85-108.

Johnson ALA, Hickson JA, Bird A, Schöne BR, Balson PS, Heaton THE, Williams M (2009, in press) Comparative sclerochronology of modern and mid-Pliocene (c. 3.5 Ma) Aequipecten opercularis (Mollusca, Bivalvia): an insight into past and future climate change in the north-east Atlantic region. Palaeogeog. Palaeoclimatol. Palaeoecol.

De Schepper S, Head MJ, Louwye S (2008) Pliocene dinoflagellate cyst stratigraphy, palaeoecology and sequence stratigraphy of the Tunnel-Canal Dock, Belgium. Geol. Mag. 146, 92-112.

Schöne BR, Fiebig J (2009) Seasonality in the North Sea during the Allerød and Late Medieval Climate Optimum using bivalve sclerochronology. Int. J. Earth Sci. 98, 83-98.

Naish T and 55 others (2009) Obliquity-paced Pliocene West Antarctic ice sheet oscillations. Nature 458, 322-329.

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