Changes in benthic ecosystems and ocean circulation in the Southeast Atlantic across Eocene Thermal Maximum 2

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doi: 10.1002/2015PA002821
Author(s): Jennions, S. M.; Thomas, E.; Schmidt, D. N.; Lunt, D.; Ridgwell, A.
Author Affiliation(s): Primary:
University of Bristol, School of Earth Sciences, Bristol, United Kingdom
Other:
Yale University, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 30(8), p.1059-1077. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. NSF grants OCE-0903014 and OCE-1232413. 103 refs.; illus., incl. 5 tables, strat. cols.
Summary: Eocene Thermal Maximum 2 (ETM2) occurred ∼1.8 Myr after the Paleocene-Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion and warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to show that benthic foraminiferal diversity and accumulation rates declined more precipitously and severely at the shallower site during peak ETM2. As the sites are in close proximity, differences in surface productivity cannot have caused this differential effect. Instead, we infer that changes in ocean circulation across ETM2 may have produced more pronounced warming at intermediate depths (Site 1263). The effects of warming include increased metabolic rates, a decrease in effective food supply and increased deoxygenation, thus potentially explaining the more severe benthic impacts at Site 1263. In response, bioturbation may have decreased more at Site 1263 than at Site 1262, differentially affecting bulk carbonate records. We use a sediment-enabled Earth system model to test whether a reduction in bioturbation and/or the likely reduced carbonate saturation of more poorly ventilated waters can explain the more extreme excursion in bulk δ13C and sharper transition in wt % CaCO3 at Site 1263. We find that both enhanced acidification and reduced bioturbation during the ETM2 peak are needed to account for the observed features. Our combined ecological and modeling analysis illustrates the potential role of ocean circulation changes in amplifying local environmental changes and driving temporary, but drastic, loss of benthic biodiversity and abundance. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2015
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Assemblages; Atlantic Ocean; Benthic taxa; C-13/C-12; Carbon; Cenozoic; Ecosystems; Eocene; Eocene Thermal Maximum 2; Faunal list; Foraminifera; GENIE; Invertebrata; Isotope ratios; Isotopes; Leg 208; Lithostratigraphy; Marine environment; Microfossils; Numerical models; O-18/O-16; ODP Site 1262; ODP Site 1263; Ocean Drilling Program; Ocean circulation; Oxygen; Paleo-oceanography; Paleoecology; Paleoenvironment; Paleogene; Protista; Quantitative analysis; South Atlantic; Southeast Atlantic; Stable isotopes; Tertiary; Walvis Ridge
Coordinates: S283200 S271100 E0024700 E0013400
Record ID: 2015104826
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom