Miocene deepwater oceanography

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doi: 10.1029/PA004i001p00087
Author(s): Woodruff, Fay; Savin, Samuel M.
Author Affiliation(s): Primary:
Univ. South. Calif., Dep. Geol. Sci., Los Angeles, CA, United States
Other:
Case Western Reserve Univ., United States
Volume Title: Paleoceanography
Source: Paleoceanography, 4(1), p.87-140. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 150 refs.; illus. incl. 3 tables, sketch maps
Summary: A global synthesis of Miocene benthic foraminiferal carbon and oxygen isotopic and faunal abundance data indicates that Miocene thermohaline circulation evolved through three regimes corresponding approximately to early, middle, and late Miocene times. There is evidence for major qualitative differences between the circulation of the modern ocean and the Miocene ocean prior to 11 Ma. The 13C/12C ratios of the benthic foraminifera Cibicidoides are interpreted in terms of water mass aging, i.e., the progressive depletion of dissolved O2 and lowering of δ13C values as the result of oxidation of organic matter as water flows further from its sources at the surface of the oceans. Both isotopic and faunal data indicate that the early Miocene regime, from 22 to 15 Ma, was the most different from today"s. During that interval intermediate and deep waters of both the Atlantic and the Pacific oceans aged in a northward direction, and the intermediate waters of the Indian, the South Atlantic and the South Pacific oceans were consistently the youngest in the global ocean. We speculate that early Miocene global thermohaline circulation may have been strongly influenced by the influx of warm saline water, Tethyan Indian Saline Water, from the Tethys into the northern Indian Ocean. The isotopic and faunal data suggest that flow from the Tethyan region into the Indian Ocean diminished or terminated at about 14 Ma. Isotopic and faunal data give no evidence for North Atlantic Deep Water (NADW) formation prior to about 14.5 Ma (with the exception of a brief episode in the early Miocene). From 14.5 to 11 Ma NADW formation was weak, and circumpolar and Antarctic water flooded the deep South Atlantic and South Pacific as the Antarctic ice cap grew. From about 10 Ma to the end of the Miocene, thermohaline circulation resembled the modern circulation in many ways. In latest Miocene time (6 to 5 Ma) circulation patterns were very similar to today's except that NADW formation was greatly diminished. The distribution pattern of siliceous oozes in Miocene sediments is consistent with our proposed reconstruction of thermohaline circulation. Major changes which occurred in circulation during the middle Miocene were probably related to the closing of the Tethys and may have contributed to rapid middle Miocene growth of the Antarctic ice cap. Copyright 1989 by the American Geophysical Union.
Year of Publication: 1989
Research Program: DSDP Deep Sea Drilling Project
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Anomalinidae; Benthic taxa; Bottom water; C-13/C-12; Carbon; Cassidulinacea; Cenozoic; Cibicidoides; Deep Sea Drilling Project; Foraminifera; Global; Invertebrata; Isotopes; Microfossils; Miocene; Neogene; O-18/O-16; Oxygen; Paleo-oceanography; Paleocirculation; Protista; Ratios; Rotaliina; Stable isotopes; Stratigraphy; Tertiary; Thermohaline circulation
Record ID: 1989074078
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute.

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