Leg 208 summary

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doi: 10.2973/odp.proc.ir.208.101.2004
Author(s): Zachos, James C.; Kroon, Dick; Blum, Peter; Bowles, Julie; Gaillot, Philippe; Hasegawa, Takashi; Hathorne, Edmund C.; Hodell, David A.; Kelly, Daniel C.; Jung, Ja-Hun; Keller, Susan M.; Lee, Youn Soo; Leuschner, Dirk C.; Liu Zhifei; Lohmann, Kyger C.; Lourens, Lucas; Monechi, Simonetta; Nicolo, Micah J.; Raffi, Isabella; Riesselman, Christina; Röhl, Ursula; Schellenberg, Stephen A.; Schmidt, Daniela; Sluijs, Appy; Thomas, Deborah J.; Thomas, Ellen; Vallius, Henry
Ocean Drilling Program, Leg 208, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
University of California at Santa Cruz, Earth Sciences Department, Santa Cruz, CA, United States
Other:
Vrije Universiteit, Netherlands
Texas A&M University, United States
Scripps Institution of Oceanography, United States
Université Montpellier II, France
Kanazawa University, Japan
Open University, United Kingdom
University of Florida, United States
University of Wisconsin at Madison, United States
Pukyong National University, South Korea
Korea Institute of Geosciences and Mineral Resources, South Korea
Universität Leipzig, Federal Republic of Germany
Tongji University, China
University of Michigan, United States
Utrecht University, Netherlands
Universita degli Studi di Firenze, Italy
Rice University, United States
Universitario "G. D'Annunzio", Italy
Stanford University, United States
Universität Bremen, Federal Republic of Germany
San Diego State University, United States
Royal Holloway University of London, United Kingdom
University of North Carolina at Chapel Hill, United States
Wesleyan University, United States
Geological Survey of Finland, Finland
Korean Institute of Geoscience and Mineral Resources, South Korea
Volume Title: Proceedings of the Ocean Drilling Program; initial reports; early Cenozoic extreme climates; the Walvis Ridge Transect; covering Leg 208 of the cruises of the drilling vessel JOIDES Resolution; Rio de Janeiro, Brazil, to Rio de Janeiro, Brazil; sites 1262-1267, 6 March-6 May 2003
Volume Author(s): Zachos, James C.; Kroon, Dick; Blum, Peter; Bowles, Julie; Gaillot, Philippe; Hasegawa, Takashi; Hathorne, Edmund C.; Hodell, David A.; Kelly, Daniel C.; Jung, Ja-Hun; Keller, Susan M.; Lee, Youn Soo; Leuschner, Dirk C.; Liu Zhifei; Lohmann, Kyger C.; Lourens, Lucas; Monechi, Simonetta; Nicolo, Micah J.; Raffi, Isabella; Riesselman, Christina; Röhl, Ursula; Schellenberg, Stephen A.; Schmidt, Daniela; Sluijs, Appy; Thomas, Deborah J.; Thomas, Ellen; Vallius, Henry; Neville, Heather; Sherar, Kenneth
Source: Proceedings of the Ocean Drilling Program; initial reports; early Cenozoic extreme climates; the Walvis Ridge Transect; covering Leg 208 of the cruises of the drilling vessel JOIDES Resolution; Rio de Janeiro, Brazil, to Rio de Janeiro, Brazil; sites 1262-1267, 6 March-6 May 2003, James C. Zachos, Dick Kroon, Peter Blum, Julie Bowles, Philippe Gaillot, Takashi Hasegawa, Edmund C. Hathorne, David A. Hodell, Daniel C. Kelly, Ja-Hun Jung, Susan M. Keller, Youn Soo Lee, Dirk C. Leuschner, Liu Zhifei, Kyger C. Lohmann, Lucas Lourens, Simonetta Monechi, Micah J. Nicolo, Isabella Raffi, Christina Riesselman, Ursula Röhl, Stephen A. Schellenberg, Daniela Schmidt, Appy Sluijs, Deborah J. Thomas, Ellen Thomas, Henry Vallius, Heather Neville and Kenneth Sherar; Ocean Drilling Program, Leg 208, Shipboard Scientific Party, College Station, TX. Proceedings of the Ocean Drilling Program, Part A: Initial Reports, Vol.208, 112p. Publisher: Texas A&M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5883 CODEN: IDSDA6
Note: In English. Also available on CD-ROM in PDF format and on the Web in PDF or HTML. 138 refs.CD-ROM format, ISSN 1096-2522; WWW format, ISSN 1096-2158; illus., incl. sects., 3 tables, sketch maps
Summary: During Ocean Drilling Program Leg 208, six sites were drilled at water depths between 2500 and 4770 m to recover lower Cenozoic sediments on the northeastern flank of Walvis Ridge. Previous drilling in this region (Deep Sea Drilling Project [DSDP] Leg 74) recovered pelagic oozes and chalk spanning the Cretaceous/Paleogene (K/P), Paleocene/Eocene, and Eocene/Oligocene boundaries. The objective of Leg 208 was to recover intact composite sequences of these "critical" transitions from a wide range of depths. Multichannel seismic data (Meteor Cruise M49/1) along with information from DSDP Leg 74 sites were used to identify sites where continuous sequences of lower Cenozoic sediment should be present. Double to triple advanced piston coring, occasional extended core barrel coring to deepen the holes, and high-resolution physical property measurements were employed to construct "composite sections." The composite sections provide a detailed history of paleoceanographic variation associated with several prominent episodes of early Cenozoic climate change, including the K/P boundary, the Paleocene/Eocene Thermal Maximum (PETM), the early Eocene Climatic Optimum, and the early Oligocene Glacial Maximum. The PETM interval, the main focus of Leg 208, was recovered at five sites along a depth transect of 2.2 km. The sediment sequence is marked by a red clay layer, which varies in thickness from 20 to 50 cm from site to site, within a thick and uniform sequence of upper Paleocene and lower Eocene foraminifer-bearing nannofossil ooze. The basal color contact is relatively sharp, although magnetic susceptibility data show a more gradual, steplike transition at the deeper Sites 1262 and 1267. The carbonate content drops to 0 wt% at all sites except for Site 1265. The upper contact is gradational in the shallow sites and relatively sharp at the deeper sites. Overlying the clay layer is a sequence of nannofossil ooze, which is slightly richer in carbonate than the unit immediately underlying the clay layer. The depth transect permits testing of the leading hypothesis for the cause of the PETM: the abrupt dissociation of as much as 2000 Gt of marine methane hydrate. Numerical modeling demonstrates that the injection of such a large mass of carbon to the ocean/atmosphere could have triggered a rapid (∼10 k.y.) global shoaling of the calcite compensation depth (CCD) and lysocline, followed by a gradual recovery, and "overcompensation" with the CCD overshooting pre-excursion depths. Based on sediment cores recovered during Leg 208, the CCD shoaled by >2 km during the excursion, considerably more than predicted in present carbon cycle models of the event. Leg 208 material also documents biotic responses to environmental changes as a result of the methane release and CCD shoaling (e.g., severe dissolution over such a large depth range may well have been an important factor in the benthic foraminiferal extinction event coincident with the base of the clay layer at every site, and nannofossils showed a short-term relative abundance response from Fasciculithus to Zygrhablithus). Planktonic foraminifers are heavily dissolved in the clay layer with only extremely rare specimens of acarinids and morozovellids remaining. The Leg 208 transect complements a transect drilled on the southern Shatsky Rise during Leg 198, a deep latitudinal transect in the equatorial Pacific drilled during Leg 199, a shallow to bathyal transect drilled on Demarera Rise during Leg 207, and a depth transect proposed for future drilling in the western North Atlantic Ocean (J-Anomaly Ridge and southeast Newfoundland Rise).
Year of Publication: 2004
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 20 Geophysics, Applied; Algae; Atlantic Ocean; Biostratigraphy; Cenozoic; Climate change; Eocene; Foraminifera; Geophysical methods; Geophysical profiles; Geophysical surveys; Invertebrata; Leg 208; Lithostratigraphy; Lower Cenozoic; Microfossils; Nannofossils; Ocean Drilling Program; Oligocene; Paleo-oceanography; Paleocene; Paleoclimatology; Paleogene; Paleomagnetism; Plantae; Protista; Seismic methods; Seismic profiles; South Atlantic; Surveys; Tertiary; Walvis Ridge
Coordinates: S290000 S270000 E0040000 E0000000
Record ID: 2004064222
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.