North Atlantic Quaternary silicoflagellates, Deep Sea Drilling Project Leg 94

Quaternary silicoflagellates from Deep Sea Drilling Project (DSDP) Mid-Atlantic Leg 94 are generally sparse and dissolution-thinned. Mesocena quadrangula, a low-latitude biostratigraphic guide species, occurs at all four sites studied (606, 607, 609, and 611), allowing identification of low-latitude zones—Dictyocha aculeata Zone, Mesocena quadrangula Zone, and Dictyocha stapedia stapedia Zone. A lack of cool-water Distephanus speculum speculum reflects warm relative paleotemperature values (Ts 74 to 98) for Leg 94. Comparison with assemblages at coastal DSDP Hole 397, off Africa, shows that Hole 397 has more abundant D. speculum speculum, suggesting that upwelling nutrient supply may significantly affect the total numbers of this species. The siliceous record of Leg 94 is sporadic, with several levels of nonpreservation that make paleotemperature trends difficult to establish by silicoflagellates. The northern range of M. quadrangula is extended to 52°50'N at Hole 611C. Opal phytoliths occur at southern Holes 606 and 607. These grasslands-produced nannofossils, representing eolian sedimentation from northwestern Africa, were likely distributed most widely during arid glacial intervals.