Significant Southern Ocean warming event in the late middle Eocene

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doi: 10.1130/G19800.1
Author(s): Bohaty, Steven M.; Zachos, James C.
Author Affiliation(s): Primary:
University of California at Santa Cruz, Earth Sciences Department, Santa Cruz, CA, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 31(11), p.1017-1020. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. With GSA Data Repository Item 2003148. 28 refs.; illus., incl. sketch map
Summary: A prominent middle Eocene warming event is identified in Southern Ocean deep-sea cores, indicating that long-term cooling through the middle and late Eocene was not monotonic. At sites on Maud Rise and the Kerguelen Plateau, a distinct negative shift in δ18O values (∼1.0ppm) is observed ca. 41.5 Ma. This excursion is interpreted as primarily a temperature signal, with a transient warming of 4 °C over 600 k.y. affecting both surface and middle-bathyal deep waters in the Indian-Atlantic region of the Southern Ocean. This isotopic event is designated as the middle Eocene climatic optimum, and is interpreted to represent a significant climatic reversal in the midst of middle to late Eocene deep-sea cooling. The lack of a significant negative carbon isotope excursion, as observed during the Paleocene-Eocene thermal maximum, and the gradual rate of high-latitude warming suggest that this event was not triggered by methane hydrate dissociation. Rather, a transient rise in pCO2 levels is suspected, possibly as a result of metamorphic decarbonation in the Himalayan Orogen or increased ridge/arc volcanism during the late middle Eocene.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Anomalinidae; Benthic taxa; Biochemistry; Biostratigraphy; C-13/C-12; Carbon; Cassidulinacea; Cenozoic; Chemostratigraphy; Cibicidoides; Climate change; Cores; Eocene; Foraminifera; Invertebrata; Isotope ratios; Isotopes; Kerguelen Plateau; Leg 113; Leg 119; Leg 120; Marine sediments; Maud Rise; Microfossils; Middle Eocene; Nuttallides; O-18/O-16; ODP Site 689; ODP Site 690; ODP Site 738; ODP Site 744; ODP Site 748; Ocean Drilling Program; Oxygen; Paleo-oceanography; Paleoclimatology; Paleogene; Paleogeography; Paleotemperature; Protista; Rotaliina; Sediments; Southern Ocean; Stable isotopes; Statistical analysis; Tertiary; Time series analysis; Weddell Sea
Coordinates: S643101 S643100 E0030600 E0030559
S650938 S650937 E0011218 E0011218
S624233 S624232 E0824715 E0824714
S613440 S613439 E0803528 E0803527
S582627 S582627 E0785854 E0785853
Record ID: 2003083434
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