Biotic response to early Eocene Thermal Maximum 3 at Walvis Ridge, SE Atlantic Ocean

Author(s): Thomas, Ellen; Balestra, Barbara; Monechi, Simonetta; Roehl, Ursula
Author Affiliation(s): Primary:
Yale University, Department of Geology and Geophysics, New Haven, CT, United States
University of California at Santa Cruz, United States
Universita di Firenze, Italy
Bremen University, Germany
Volume Title: Geological Society of America, 2015 annual meeting & exposition
Source: Abstracts with Programs - Geological Society of America, 47(7), p.631; Geological Society of America, 2015 annual meeting & exposition, Baltimore, MD, Nov. 1-4, 2015. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: Late Paleocene-early Eocene climate was punctuated by transient global warming events (thermal maxima) due to release of isotopically light carbon into the ocean-atmosphere, characterized by a global, negative carbon isotope excursion (CIE) coeval with warming and deep-sea carbonate dissolution. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM). The biotic response to the PETM has been widely studied, but less severe hyperthermals have not yet been well documented. Eocene Thermal Maximum 3 (ETM3) was the largest ETM after the PETM and ETM2 (Elmo), occurring ∼3.1 myr after the PETM. We combined stable isotope records with calcareous nannoplankton and benthic foraminiferal data for ODP Sites 1263 (paleodepth ∼1500 m) and 1262 (paleodepth ∼3600 m) on Walvis Ridge (SE Atlantic). ETM3 (planktic foraminifer Zone P7, calcareous nannofossil Zone CP10) is characterized by a CIE of ∼0.9 ppm, deep-sea warming of ∼2.5°C and a rise in the lysocline. Dissolution-resistant calcareous nannoplankton species (species of Discoaster and Sphenolithus) and eutrophic indicators ('HS'-group) increased in abundances at Site 1263, while mesotrophic Toweius spp., decreased slightly. At Site 1262 changes were more muted. Benthic foraminiferal diversity and relative abundance of cylindrical species decreased at both sites, while the % of opportunistic abyssaminids increased. Benthic Foraminiferal Accumulation Rates (BFAR), indicative of food supply to the benthos, remained stable at Site 1262, but declined severely at 1263, as did ARs of all species. At the deeper Site 1262 assemblage changes in nannofossils and benthic taxa thus were much less pronounced, suggesting that they cannot be due to dissolution alone. Overall, surface primary productivity may have increased, especially at shallower, slightly more coastal Site 1263, where food supply to the benthos declined severely, in contrast to the Site 1262. Increased ocean stratification, warming, and shallowing of the thermocline may have caused increased remineralization of organic matter, resulting in declining food supply to the sea floor, potentially more pronounced at the shallower site because of more pronounced warming due to circulation changes during ETM3.
Year of Publication: 2015
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Assemblages; Atlantic Ocean; Cenozoic; Eocene; Eocene Thermal Maximum 3; Foraminifera; Invertebrata; Isotopes; Leg 208; Lower Eocene; Marine environment; Microfossils; Nannofossils; ODP Site 1262; ODP Site 1263; Ocean Drilling Program; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Paleogene; Plantae; Protista; South Atlantic; Stable isotopes; Tertiary; Walvis Ridge
Coordinates: S271100 S271100 E0013500 E0013400
S290000 S270000 E0030000 E0013000
Record ID: 2016055448
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States