Bottom water changes in the subtropical North Atlantic and the Southern Ocean associated to the Middle Eocene Climatic Optimum

Author(s): Moebius, I.; Friedrich, O.; Edgar, K. M.; Scher, H. D.; Sexton, Philip
Author Affiliation(s): Primary:
Goethe University Frankfurt, Institute for Geosciences, Frankfurt, Germany
Cardiff University, United Kingdom
University of South Carolina, United States
Open University, United Kingdom
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Middle Eocene Climatic Optimum (MECO) is a ∼650 kyr interval of pronounced global warmth from which the climate system recovered in less than 50 kyr. Despite the valuable insights that the deep-sea sedimentary record could provide on the benthic ecosystem response to this protracted global warming event, and the mechanisms responsible for its relatively rapid recovery, we have little understanding of either. Here we present new data on bottom-water characteristics from ODP Sites 1051 (subtropical North Atlantic) and 738 (Southern Ocean), spanning the MECO and post-MECO interval (41.1 to 39.5 Ma). At Site 1051 we used benthic foraminiferal assemblages and benthic foraminifera accumulation rates (BFAR). We find little change in the species composition, but we identify two transient intervals of BFARs increasing by one order of magnitude associated with peak warming: High Productivity Intervals HPI-1 (40.07-39.98 Ma) and HPI-2 (39.70-39.62 Ma). We correlate these HPIs to intervals of increased organic carbon burial found in the Tethys and suggest that they represent periods of strengthened productivity in the subtropical North Atlantic and the Tethys. At Southern Ocean Site 738 we used benthic foraminiferal assemblages in combination with Cerium-anomaly data. In contrast to Site 1051, we notice a turnover of the benthic foraminiferal communities during the MECO (40.60 and 39.95 Ma) towards an assemblage dominated by infaunal taxa indicative of eutrophication. Additionally, we observe a drop in benthic foraminiferal abundances during the peak warming (40.10-39.97 Ma), synchronous to a low Cerium-anomaly and small excursion in εNd values. This indicates a decrease in bottom-water oxygenation during MECO peak warming, potentially caused by the transient influence of an older, oxygen-depleted water mass. Overall, our data suggest that the extent and rate of environmental change associated with the MECO vary greatly in different ocean basins and that the processes influencing bottom waters are subject to large latitudinal differences.
Year of Publication: 2013
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Assemblages; Atlantic Ocean; Benthic taxa; Blake Nose; Blake Plateau; Cenozoic; Eocene; Foraminifera; Invertebrata; Kerguelen Plateau; Leg 119; Leg 171B; Marine environment; Microfossils; Middle Eocene; North Atlantic; ODP Site 1051; ODP Site 738; Ocean Drilling Program; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Paleogene; Protista; Southern Ocean; Tertiary
Coordinates: S624233 S624232 E0824715 E0824714
N300311 N300311 W0762128 W0762128
Record ID: 2015085783
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