Millennial and sub-millennial-scale variability in sediment colour from the Barra Fan, NW Scotland: implications for British ice sheet dynamics
Sediment colour, together with other proxy data, provides a novel, rapid and non-destructive tool in the investigation of glacier-influenced sedimentation on the Barra Fan, NW Scotland. Lightness (L*) and reflectance (400-700 nm) measurements at this site provide a quantitative estimate of changes i...
Main Authors: | , |
---|---|
Other Authors: | , |
Format: | Book Part |
Language: | English |
Published: |
Geological Society of London
2002
|
Subjects: | |
Online Access: | https://research-portal.st-andrews.ac.uk/en/researchoutput/millennial-and-submillennialscale-variability-in-sediment-colour-from-the-barra-fan-nw-scotland-implications-for-british-ice-sheet-dynamics(553ba7c5-b49c-479f-953e-25082a66a703).html http://www.scopus.com/inward/record.url?scp=0038445632&partnerID=8YFLogxK |
Summary: | Sediment colour, together with other proxy data, provides a novel, rapid and non-destructive tool in the investigation of glacier-influenced sedimentation on the Barra Fan, NW Scotland. Lightness (L*) and reflectance (400-700 nm) measurements at this site provide a quantitative estimate of changes in calcium carbonate and clay content. Interstadials are carbonate-rich/clay-poor (higher L* and reflectivity), whereas stadials are carbonate-poor/clay-rich (lower L* and reflectivity). Detailed sedimentological investigations suggest that the last British Ice Sheet (BIS) extended to the outer continental shelf-break shortly after 30 ka Bp. This climatic response of the BIS to global cooling at the Marine Isotope Stage (MIS) 3 - 2 transition marks a significant increase in sediment delivery to the Barra Fan. Prior to 30 ka BP, strong Dansgaard/Oeschger (D/O) cyclicity dominates the record. After 30 ka BP, shorter periodicities prevailed as the BIS reached its maximum extent. Glacier dynamics plays a significant role in the delivery of ice-rafted debris (IRD) across this margin, highlighting the inherent difficulties of correlating millennial-scale IRD events when the IRD is derived from different ice sheets. An event stratigraphy based upon carbonate-rich interstadials provides a more robust means of amphi-Atlantic correlation during this interval. |
---|