Paleoceanographic inferences from benthic foraminifera across the early Aptian Ocean Anoxic Event 1a in the western Tethys

The paleoenvironmental impact of the early Aptian Ocean Anoxic Event 1a (OAE 1a, ca. 121 Ma) has been investigated in detail Cismon Core (Lombardy Basin, western Tethys) by using different geochemical and micropaleontological proxies. We provide first high-resolution data benthic foraminiferal assemblages through upper Barremian - lower stratigraphic interval. Benthic foraminifera are integrated with calcareous nannofossil planktonic records to create a comprehensive characterization bottom surface waters across OAE 1a. communities indicative marked change bottom-waters around “nannoconid decline” (latest Barremian) due increased flux organic matter seafloor intermittent dysoxic conditions probably promoted pulses higher productivity during initial Greater Ontong Java (GOJE). experienced crisis abundance (“benthic crisis” BFC) 35 kyr before correspondence onset most intense GOJE phase. literature survey shows that BFC is commonly recorded several sections worldwide, therefore, it here proposed as global event. At Cismon, deep-water anoxia was reached at lasted for 300 kyr, eventually enhanced water stratification super-greenhouse climate. continuation repopulation event, resulting from influx relatively cooler oxygenated waters. In turn, anoxic conditions, likely response primary sustained N-fixing bacteria. distribution documented other Selli Level equivalent show features point local factors such paleodepth runoff. post-OAE characterized coupled moderate seafloor. site termination coincided return more abundant taxa restoration favorable allowing development diversified communities.