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Significant Southern Ocean warming event in the late middle Eocene

Steven M. Bohaty and James C. Zachos
Significant Southern Ocean warming event in the late middle Eocene
Geology (Boulder) (November 2003) 31 (11): 1017-1020


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 delta (super 18) O values ( approximately 1.0ppm) is observed ca. 41.5 Ma. This excursion is interpreted as primarily a temperature signal, with a transient warming of 4 degrees 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 pCO (sub 2) levels is suspected, possibly as a result of metamorphic decarbonation in the Himalayan Orogen or increased ridge/arc volcanism during the late middle Eocene.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 31
Serial Issue: 11
Title: Significant Southern Ocean warming event in the late middle Eocene
Affiliation: University of California at Santa Cruz, Earth Sciences Department, Santa Cruz, CA, United States
Pages: 1017-1020
Published: 200311
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 28
Accession Number: 2003-083434
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2003148
Illustration Description: illus. incl. sketch map
S58°26'27" - S58°26'27", E78°58'53" - E78°58'54"
S64°31'01" - S64°31'00", E03°05'59" - E03°06'00"
S65°09'38" - S65°09'37", E01°12'18" - E01°12'18"
S62°42'33" - S62°42'32", E82°47'14" - E82°47'15"
S61°34'40" - S61°34'39", E80°35'27" - E80°35'28"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200324
Program Name: ODPOcean Drilling Program
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