The BGS Lexicon of Named Rock Units — Result Details

Upper Nordland Unit

Computer Code: NORDU Preferred Map Code: notEntered
Status Code: Full
Age range: Mid Pleistocene (QPM) — Holocene Epoch (QH)
Lithological Description: Lithological information is largely derived from BGS boreholes and short cores, complemented by some commercial data north of Shetland. For ease of description, a shelf facies and a slope and basinal facies are here differentiated. The shelf facies, where represented by the acoustically structureless to chaotic texture, is characterised by a stacked assemblage of diamictons (a poorly sorted admixture of mud, sand and gravel), which are commonly mud-dominated, olive grey to very dark grey-brown, and stiff to hard, with subordinate sandy and gravelly diamictons, and thinner, interbedded, sandy gravels, gravelly sands, graded sands and sporadic muds with dropstones and shell fragments. The diamictons may vary from massive to crudely stratified, and from matrix- to clast-supported. The slope and basinal facies comprises a variable ratio of interbedded debris flows and glacimarine and marine deposits (Paul et al., 1998; King et al., 1996; Stoker et al., 1998). The debris flows dominate the slope apron (e.g. 85/01), and are composed of very soft to firm, lightly to non-bioturbated, very dark grey to dark grey brown, very poorly sorted, massive, muddy and sandy diamictons, with a gravel clast-content, including mud rip-up clasts, ranging from 2-30%. The gravel is matrix-supported and randomly orientated. Sporadic shell fragments indicate a shelf-derived fauna. The glacimarine and marine strata, which comprise the acoustically-layered strata, consist of interbedded, normally- to lightly-overconsolidated, muds, sandy muds, sandy silts and muddy sands. These are variably bioturbated, poorly sorted, dark grey to olive grey to olive, and contain common shells, shell fragments and scattered, matrix-supported, dropstones.
Definition of Lower Boundary: On the shelf and upper slope, the lower boundary is a widespread, seismically-distinct, planar to irregular, angular, erosional unconformity - the glacial unconformity - which truncates Middle Nordland and older strata. On the lower slope, it is more planar in form and commonly a downlap surface becoming a more conformable, less seismically-distinct, draped surface in the basin.
Definition of Upper Boundary: The upper boundary is the present-day sea bed.
Thickness: none recorded or not applicable
Geographical Limits: The Upper Nordland unit is widely distributed on the West Shetland Margin, extending from the West Shetland Shelf into the Faroe-Shetland Channel. It is locally absent on rock platforms especially around Orkney and Shetland, although these may be covered by a veneer of sea-bed sediment, and at the south-west end of the Faroe-Shetland Channel.
Parent Unit: Nordland Group (NORD)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  BGS borehole 77/07: 0 - 47.5 m below sea bed (Stoker, 1999). 
Reference Section  BGS borehole 84/04: 0 - 62.5 m below sea bed (Stoker, 1999). 
Reference Section  BGS borehole 85/01: 0 - 13.9 m below sea bed (Stoker, 1999). 
Reference(s):
Stoker, M S. 1999. Stratigraphic nomenclature of the UK North West Margin. 3. Mid- to Late Cenozoic Stratigraphy. BGS, Nottingham. 
Paul, M A, Talbot, L A, and Stoker, M S. 1998. Shallow geotechnical profiles, acoustic character and depositional history in glacially influenced sediments from the Hebrides and West Shetland Slopes. In: Stoker, M S, Evans, D, and Cramp, A (eds.), Geological Processes on Continental Margins: Sedimentation, Mass-Wasting and Stability. Geological Society Special Publication, 129, 117-131. 
Stoker, M S, Akhurst, M C, Howe, J A, and Stow, D A V. 1998. Sediment drifts and contourites on the continental margin off northwest Britain. Sedimentary Geology, 115, 33-51. 
King, E L, Sejrup, H P, Haflidason, H, Elverhoi, A, and Aarseth, I. 1996. Quaternary seismic stratigraphy of the North Sea fan: glacially-fed gravity flow aprons, hemipelagic sediments, and large submarine slides. Marine Geology, 130, 293-315. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable