Ocean acidification and its ensuing recovery during the Paleocene-Eocene thermal maximum as chronicled by spatial/temporal patterns of carbonate sedimentation in the South Atlantic and Southern Oceans

Author(s): Kelly, D. C.; Zachos, J. C.; Schellenberg, S. A.; Nielsen, T. M.; McCarren, Heather K.
Author Affiliation(s): Primary:
University of Wisconsin-Madison, Department of Geology and Geophysics, Madison, WI, United States
Other:
University of California at Santa Cruz, United States
San Diego State University, United States
Volume Title: Geological Society of America, 2005 annual meeting
Source: Abstracts with Programs - Geological Society of America, 37(7), p.413; Geological Society of America, 2005 annual meeting, Salt Lake City, UT, Oct. 16-19, 2005. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: A negative carbon isotope excursion (CIE) and widespread carbonate dissolution in deep-sea records indicate that the oceans were acidified by the rapid release of vast quantities of carbon during the Paleocene-Eocene thermal maximum (PETM, ca. 55 Ma). Three basic subdivisions of the CIE (pre-CIE, CIE, CIE-recovery) are used to decipher the history of carbonate sedimentation at a series of PETM sections from the Walvis Ridge depth transect in the southeastern Atlantic (ODP Sites 1263, 1266, 1262) and the Maud Rise in the Southern Ocean (ODP Sites 689, 690). Though carbonate content declined at all sites during the CIE onset, dissolution was far more intense in the southeastern Atlantic, where the CIE onset is marked by a layer of clay. Such spatial differences in the degree of carbonate dissolution likely reflect proximity to the carbon source and/or areas where thermohaline circulation transferred liberated carbon to the deep ocean. In contrast, grossly similar patterns of carbonate sedimentation are preserved within the CIE-recovery intervals of the Walvis Ridge and Maud Rise sites. Specifically, carbonate content gradually recovers, increasing into an extended maximum that is higher than pre-CIE levels. This carbonate-enrichment is initially paralleled by a brief increase in wt% coarse-fraction that is rapidly reversed with wt% coarse-fraction declining into an extended minimum that is lower than pre-CIE levels. We attribute this sedimentological shift to a dilution effect driven by increased coccolithophorid production/preservation during the CIE recovery. A notable exception to this CIE-recovery pattern is the deepest of the PETM sites (Site 1262), where both carbonate content and wt% coarse-fraction increase above pre-CIE levels. This discrepancy is owed to the deeper water depth (3.6 km) of Site 1262, and reflects improved foraminiferal-shell preservation as the lysocline/CCD descended to depths deeper than initial levels, an interpretation confirmed by shell fragmentation data. Though the Maud Rise sites do not capture the full range of lysocline movement, the coherent patterns of carbonate sedimentation typifying the CIE recovery period do conform to a predicted "over-deepening" of the lysocline/CCD likely fostered by an alkalinity overshoot driven by increased continental weathering/runoff.
Year of Publication: 2005
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Acidification; Atlantic Ocean; C-13/C-12; Carbon; Cenozoic; Deep-sea environment; Eocene; Fragmentation; Isotope ratios; Isotopes; Leg 113; Leg 208; Lower Eocene; Lysoclines; Marine environment; Maud Rise; ODP Site 1262; ODP Site 1263; ODP Site 1266; ODP Site 689; ODP Site 690; Ocean Drilling Program; Paleo-oceanography; Paleocene; Paleogene; Patterns; Runoff; Sedimentation; Shells; Solution; South Atlantic; Southern Ocean; Stable isotopes; Tertiary; Thermohaline circulation; Upper Paleocene; Walvis Ridge; Weathering; Weddell Sea
Coordinates: S643101 S643100 E0030600 E0030559
S650938 S650937 E0011218 E0011218
S283200 S283200 E0024700 E0024700
S283300 S283200 E0022100 E0022000
S271100 S271100 E0013500 E0013400
Record ID: 2006082892
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States

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