Publication Date:
2023-07-10
Description:
The oxygen- and carbon-isotope compositions of planktic and benthic foraminifera and calcareous nannofossils from Middle Oligocene-Early Miocene Equatorial Atlantic sediments (DSDP Site 354) indicate two important paleoceanographic changes, in the Late Oligocene (foraminiferal Zone P.21) and in the Early Miocene (foraminiferal Zone N.5). The first change, reflected by a delta18O increase of 1.45‰ in Globigerina venezuelana, affected only intermediate pelagic and not surface, deep or bottom waters. The second change affected surface and intermediate waters, whereas deep and bottom waters showed only minor fluctuations. In the case of the former the isotope effect of the moderate ice accumulation on the Antarctic continent is amplified in the Equatorial Atlantic by changes in the circulation pattern. The latter paleoceanographic change, reflected by a significant increase in 18O in both planktic and benthic forms (about 1.0‰ and 0.5‰, respectively), may have been caused by ice volume increase and temperature decrease. Both oxygen- and carbon-isotope compositions indicate a marked depth-habitat stratification for planktic foraminifera and calcareous nannofossils. Three different dwelling groups are recognized: shallow Globigerinoides, Globoquadrina dehiscens, Globorotalia mayeri and nannofossils; intermediate Globigerina venezuelana; and deep Catapsydrax dissimilis. The comparison of foraminifera and calcareous nannofossils suggests that the isotopic compositions of nannofossils are generally controlled by the same parameters which control the isotopic composition of shallow-dwelling foraminifera, but the former are more enriched in 18O.
Keywords:
39-354; Catapsydrax dissimilis, δ13C; Catapsydrax dissimilis, δ18O; Cibicidoides pseudoungerianus, δ13C; Cibicidoides pseudoungerianus, δ18O; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Foraminifera, benthic δ13C; Foraminifera, benthic δ18O; Globigerina venezuelana, δ13C; Globigerina venezuelana, δ18O; Globigerinoides ruber, δ13C; Globigerinoides ruber, δ18O; Globigerinoides trilobus, δ13C; Globigerinoides trilobus, δ18O; Globocassidulina subglobosa, δ13C; Globocassidulina subglobosa, δ18O; Globoquadrina dehiscens, δ13C; Globoquadrina dehiscens, δ18O; Globoquadrina globularis, δ13C; Globoquadrina globularis, δ18O; Globorotalia kugleri, δ13C; Globorotalia kugleri, δ18O; Globorotalia mayeri, δ13C; Globorotalia mayeri, δ18O; Globorotalia opima opima, δ13C; Globorotalia opima opima, δ18O; Glomar Challenger; Leg39; North Atlantic/CONT RISE; ORDINAL NUMBER; Oridorsalis umbonatus, δ13C; Oridorsalis umbonatus, δ18O; Planktic foraminifera zone; Sample code/label; Stilostomella spp., δ13C; Stilostomella spp., δ18O; δ13C, carbonate; δ18O, carbonate
Type:
Dataset
Format:
text/tab-separated-values, 415 data points
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