The Unusal Presence of Diatoms in Western North Atlantic Sediments during the Deglaciation

Abstract:

Since the North Atlantic flooding by southern sourced water (SSW) during the last deglaciation has likely promoted increased siliceous primary productivity and preservation, it is relevant to define its occurrence and its composition to assess how marine productivity conditions were modified.

This work presents the study of the siliceous microfossil content of several cores from the western North Atlantic during the last deglaciation. Diatoms are mostly present during the Mystery Interval (here, 18.5 - 14.5 ka). At sites between 74ºN and 48ºN, part of the diatom record was composed by Ethmodiscus fragments and their abundance was notably increased during the first part of the interval. Then, the others marine diatom genera were more abundant and Ethmodiscus fragments even disappeared from the southern sites sediments.

The ecologic specificities of Ethmodiscus vs other marine diatom genera will be discussed and compared with oxygen isotopes measurements to interpret the possible sequence of oceanographic processes involved.