Paleoredox changes across the Paleocene-Eocene Thermal Maximum, Walvis Ridge (ODP Sites 1262, 1263, and 1266); evidence from Mn and U enrichment factors

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doi: 10.1029/2009PA001861
Author(s): Chun, Cecily O. J.; Delaney, Margaret L.; Zachos, James C.
Author Affiliation(s): Primary:
University of California at Santa Cruz, Institute of Marine Sciences, Santa Cruz, CA, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 25(4). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 73 refs.; illus., incl. 2 tables
Summary: An understanding of sediment redox conditions across the Paleocene-Eocene thermal maximum (PETM) (∼55 Ma) is essential for evaluating changes in processes that control deep-sea oxygenation, as well as identifying the mechanisms responsible for driving the benthic foraminifera extinction. Sites cored on the flanks of Walvis Ridge (Ocean Drilling Program Leg 208, Sites 1262, 1266, and 1263) allow us to examine changes in bottom and pore water redox conditions across a ∼2 km depth transect of deep-sea sediments of PETM age recovered from the South Atlantic. Here we present measurements of the concentrations of redox-sensitive trace metals manganese (Mn) and uranium (U) in bulk sediment as proxies for redox chemistry at the sediment-water interface and below. All three Walvis Ridge sites exhibit bulk Mn enrichment factors (EF) ranging between 4 and 12 prior to the warming, values at crustal averages (Mn EF = 1) during the warming interval, and a return to pre-event values during the recovery period. U enrichment factors across the PETM remains at crustal averages (U EF = 1) at Site 1262 (deep) and Site 1266 (intermediate depth). U enrichment factors at Site 1263 (shallow) peaked at 5 immediately prior to the PETM and dropped to values near crustal averages during and after the event. All sites were lower in dissolved oxygen content during the PETM. Before and after the PETM, the deep and intermediate sites were oxygenated, while the shallow site was suboxic. Our geochemical results indicate that oxygen concentrations did indeed drop during the PETM but not sufficiently to cause massive extinction of benthic foraminifera.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Actinides; Atlantic Ocean; C-13/C-12; Calcium carbonate; Carbon; Cenozoic; Chemostratigraphy; Concentration; Cores; Diagenesis; Dissolved oxygen; Eh; Enrichment; Eocene; Isotope ratios; Isotopes; Leg 208; Lithofacies; Manganese; Marine environment; Metals; ODP Site 1262; ODP Site 1263; ODP Site 1266; Ocean Drilling Program; Oxygen; Paleo-oceanography; Paleocene; Paleocene-Eocene Thermal Maximum; Paleoclimatology; Paleogene; Solutes; South Atlantic; Stable isotopes; Tertiary; Trace metals; Uranium; Walvis Ridge
Coordinates: S271100 S271100 E0013500 E0013400
S283200 S283200 E0024700 E0024700
S283300 S283200 E0022100 E0022000
Record ID: 2013034375
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