Palynology and foraminiferal geochemistry of the Lower Pleistocene Olduvai Subchron (ca. 1.8 Ma) in DSDP Hole 603C, western North Atlantic
Abstract
Marine palynology and benthic and planktonic foraminiferal geochemistry are combined
to reveal long- and short-term (Milankovitch-scale) paleoceanographic changes across
the upper half of the Olduvai Subchron (ca. 1.86--1.77 Ma, lower Pleistocene) in DSDP
Hole 603C from the lower New Jersey continental rise. Planktonic foraminiferal Mg/Ca
ratios reveal annual sea-surface temperatures between 14.5° and 25°C, whereas modern
values vary between 16° and 20°e. Despite evidence of downslope transport in much of
the studied interval, dinoflagellate cyst and acritarch assemblages appear to reflect
fluctuating temperate to subtropical water masses. These assemblages comprise both
neritic and oceanic species, and are marked by a transition upsection from warm
conditions, dominated by Lingulodinium machaerophorum, Polysphaeridium zoharyi and
Cymatiosphaera? invaginata, to cooler conditions dominated by Filisphaera filifera.
Combining dinoflagellate cyst proxies with planktonic foraminiferal geochemistry allows
downslope transport events to be recognized during glacial episodes, and events
dominated by intensified bottom-water circulation during interglacial episodes. Sixtytwo
in-situ dinoflagellate cyst and acritarch taxa were recorded including several not
previously described.