Late Quaternary sedimentation on the Southern Sohm Abyssal Plain

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ABSTRACT

Six closely spaced sediment cores taken below the carbonate compensation depth penetrated fine silty muds and entered sandy sediment at 10–12 m below the seafloor. Foraminiferal assemblages and δ8O analyses on planktonic foraminifera indicated that the surface muds down to 2 m are Holocene and derived from local promontories above the CCD. Below these sediments are about 6 m of clays deposited during the late Wisconsin. These are unfossiliferous and have a possible northern source suggested by the higher chlorite content. Sandy sediments below 9 m in the cores contain well preserved benthic foraminifera from the Scotian Shelf. Glacial δ18O values on planktonic tests indicate the sandy sediments are most likely of latest Wisconsin age. Thus during the recent interglacial, the sand fraction of the southern Sohm Abyssal Plain sediments is mostly locally derived, but during glacial periods the sediments have a distant northern source containing quartz sand that was initially deposited on the Scotian Shelf 1,500 km to the north.

Ancillary