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Advisor(s)
Abstract(s)
During Integrated Ocean Drilling Program Expedition 339, the
shipboard micropaleontological studies of Site U1387 core catcher
samples revealed the preservation of diatoms and radiolarians in
specific depths from early Pleistocene age (900–1000 ka). To evaluate the ecological significance of those diatoms, we analyzed 98
samples from the intervals of 244 to 274 m along the corrected
splice, corresponding to marine isotope Stage (MIS) 25 to MIS 29,
for the abundance of diatoms and silicoflagellates. In 6 samples,
the composition of the diatom assemblage was determined as
well. Although most samples were barren of siliceous microfossils,
the downcore record revealed two intervals, 249–252 corrected
meters composite depth (cmcd) and 263–265 cmcd, where diatoms and silicoflagellates reach their maximum values. These
maxima occurred from the MIS 26/25 transition to interglacial
MIS 25, and again during early MIS 27. The diatom assemblage includes 27 identified taxa with Chaetoceros (Hyalochaete) resting
spores being dominant and Thalassionema nitzschioides and Paralia sulcata significant. The Chaetoceros spores clearly indicate
strong influence of seasonal upwelling and associated high primary productivity. Special to the diatom record is, however, the
occurrence of the large-diameter (>125 µm) centric diatoms Coscinodiscus asteromphalus, Coscinodiscus apiculatus, and Coscinodiscus
cf. gigas that imply incursions of low-nutrient, open-ocean water
into the southern Portuguese coast during MIS 25.
Description
Keywords
IODP Diatoms Gulf of Cadiz Paleoceanography MId-Pleistocene Transition Micropaleontology
Citation
Publisher
Integrated Ocean Drilling Program