Biogeography of the Late Paleocene Benthic Foraminiferal Extinction
During the Late Paleocene Thermal Maximum (LPTM) benthic foraminifera at middle bathyal and greater depths suffered extinction of 30-50% of species during a few thousand years. Extinction was less severe at neritic to upper bathyal depths, where temporary changes in faunal composition prevailed. Pre-extinction deep-sea faunas were cosmopolitan and diverse, and contained heavily calcified species. Immediate post-extinction faunas were more variable geographically, exhibited low diversity, and were dominated by thin-walled calcareous or agglutinated taxa, possibly because CaCO3 dissolution increased globally from neritic to abyssal depths just before the extinction. These assemblages were dominated either by long-lived taxa such as Nuttallides truempyi or by buliminid taxa, the latter accompanied by agglutinants in some areas. Faunas dominated by N. truempyi were common in the South Atlantic and at lower bathyal through upper abyssal depths in the Indian Ocean, and might indicate oligotrophic conditions as well as increased corrosiveness. Buliminid-dominated faunas might indicate high rates of deposition of organic matter or low-oxygen conditions. Such faunas were common globally along continental margins, and locally co-occurred with sedimentologic or planktonic faunal indicators of high productivity. In the bathyal central Pacific, however, buliminid dominated faunas co-occurred with planktonic faunas suggesting oligotrophy, and they could reflect low-oxygen conditions resulting from sluggish ocean circulation, oxidation of dissociated methane hydrates, or warming of bathyal-abyssal waters caused by a change in deep-sea circulation. Alternatively, they could indicate that the faction of organic matter reaching the seafloor increased as a result of decreased oceanic oxygenation. The latest Paleocene benthic extinction thus was complex, and factors such as changes in deep-sea circulation, increased CaCO3 corrosiveness. increased temperatures, decreased oxygenation and changes in the patterns of high productivity may have contributed to its severity.
Ellen Thomas. "Biogeography of the Late Paleocene Benthic Foraminiferal Extinction" Late Paleocene-Early Eocene Climatic and Biotic Events in the Marine and Terrestrial Records. Ed. M. P. Aubry, S. Lucas and W. A. Berggren. New York: Columbia University Press, 1998. 214-243.
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