Paleocene to Eocene benthic foraminiferal isotopes and assemblages: Implications for deepwater circulation

摘要: Early Paleogene warm climates may have been linked to different modes and sources of deepwater formation. Warm polar temperatures the Paleocene Eocene resulted from either increased atmospheric trace gases or heat transport through deep intermediate waters. The possibility increasing ocean production saline waters (WSDW) in Tethyan region has generated considerable interest. In addition, General Circulation Model results indicate that source regions be highly sensitive changing basin configurations. To decipher changes, we examined detailed benthic foraminiferal faunal isotopic records late early (∼60 50 Ma) two critical regions: North Atlantic (Bay Biscay Site 401) Pacific (Shatsky Rise 577). These are compared with published data Southern Ocean (Maud 690, Islas Orcadas 702). During Paleocene, similar δ18O values were recorded at all four sites. This indicates uniform temperatures, consistent a single water. highest δ13C 0.5‰ more positive than those Pacific. We infer was proximal nutrient-depleted water during Paleocene. Upper Reflector Ab cut on western Bermuda by cyclonically circulating bottom water, also suggesting vigorous Ocean. A dramatic negative excursion both carbon oxygen isotopes occurred latest is short-term (<100 kyr), globally synchronous event which apparent as approximately 1‰. Faunal analyses sites largest turnover Cenozoic excursion, lending support hypothesis extinctions caused change circulation. speculate reduced eliminated time excursion. Eocene, remained enriched relative However, these basins. interpret patterns although cool, upper ventilated probably originated low latitudes, i.e., WSDW.