A record of late Cenozoic stratigraphy, sedimentation and climate change from the Hebrides Slope, NE Atlantic Ocean

Abstract

A punctuated 103.3 m thick succession of upper Palaeogene to Quaternary sediments has been recovered in a borehole from the upper Hebrides Slope, west of Britain. The borehole proved 11.2m of upper Oligocene, carbonate-rich muds at the base, unconformably overlain by 2.85 m of middle to upper Miocene, glauconitic sands. This is in turn unconformably overlain by 89.25 m of predominantly Plio-Pleistocene sands and muds, with a Holocene sea-bed veneer. The post-Miocene succession is subdivided into two units: the sand-dominated, Pliocene to lower middle Pleistocene, Lower MacLeod sequence between 89.25 and 67.82 m, and the mud-dominated, middle Pleistocene to Holocene, Upper MacLeod sequence above 67.82 m. Regional mapping indicates that these sequences are commonly associated with large-scale shelf-margin progradation and slope-front fan construction. The borehole core provides an excellent record of the transition from pre-glacial to glacial conditions in the mid-latitude NE Atlantic Ocean. Climatic conditions warmer than present prevailed in the late Oligocene, mid- to late Miocene and Pliocene, although the influx of ice-rafted detritus in the late Pliocene marks the onset of climatic deterioration. This deterioration continued, in a fluctuating manner, until the early mid-Pleistocene (0.44 Ma) when fully glacial conditions were established on the Hebridean Margin.

The northern sector of the last British Ice Sheet: Maximum extent and demise

“…Ma), although expansive glaciation of the continental shelf probably did not occur until the early Mid-Pleistocene, about 0.44 Ma (MIS 12) (Shackleton et al, 1984;Cameron et al, 1987;Stoker et al, 1994). In the central and northern North Sea Basin, and on the Hebrides and West Shetland shelves, seismic reflection profiles reveal stacked glacigenic sequences that imply recurrent glaciation of the continental shelf between MIS 12 and MIS 2 (Skinner and Gregory, 1983;Stoker et al, 1985Stoker et al, , 1993Stoker et al, , 1994Cameron et al, 1987;Sejrup et al, 1987Sejrup et al, , 1991Sejrup et al, , 1994Sejrup et al, , 2000Sejrup et al, , 2005Johnson et al, 1993;Gatliff et al, 1994;Holmes, 1997).…”

“…In total, this trough is about 200 km long, up to 50 km wide, and contains locally thick accumulations (50-150 m) of subglacial and proglacial sediments, including basal till, multiple ice-contact sequences, stratified proglacial outwash and glacimarine sediments (Stoker et al, 1994;Stoker and Bradwell, 2005). Pleistocene glaciations, including the LGM (Stoker and Bradwell, 2005;Bradwell et al, 2007).…”

Cenozoic post-rift sedimentation off northwest Britain: Recording the detritus of episodic uplift on a passive continental margin

“…In this study, the distribution and thickness of the Eocene and Oligocene successions has been determined from regional offshore mapping by the BGS (Stoker et al, 1994;British Geological Survey, 2002, 2007Stoker, 2010;Stoker & Varming, 2010) and from commercial seismic datasets (Robinson, 2004). For the Miocene-Lower Pliocene and Lower…”

Progress in marine geoconservation in Scotland’s seas: assessment of key interests and their contribution to Marine Protected Area network planning

“…All of these large fans, and adjacent shelf slopes, contain records of sedimentation stretching back many hundreds of thousands of years and thus represent extremely valuable archives of Quaternary glacial history (Stoker et al, 1994;Scourse et al, 2009;Hibbert et al, 2010).…”

“…Studies of past regionalscale changes in ocean circulation from the sedimentary records in this region, notably from cores in the trough-mouth Barra Fan, Rosemary Bank and Rockall Trough, have played an important part in elucidating the links with the wider global climate system and have the potential to improve greatly our understanding of future changes. For example, they have revealed repeated marine-terminating and shelf-edge glaciations (Stoker et al, 1994;Thierens et al, 2012), regional-scale changes in palaeoceanography and climate variations at the subMilankovitch (millennial) scale (Kroon et al, 1997(Kroon et al, , 2000Howe et al, 1998;Knutz et al, 2001Knutz et al, , 2007Austin and Kroon 2001;Dickson et al, 2008;McIntyre and Howe, 2009;Hall et al, 2011;Austin et al, 2012;Small et al, 2013), complex spatial and temporal variations in the advance and retreat of the last British-Irish Ice Sheet at millennial timescales linked to latitudinal variations in the North Atlantic Polar Front (Knutz et al, 2001(Knutz et al, , 2007Peters et al, 2008;Scourse et al, 2009;Hibbert et al, 2010) and changing sedimentation patterns and processes (Kroon et al, 2000;.…”