Benthic foraminiferal assemblages during ETM2; variations by geography and depth

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Author(s): Thomas, Ellen
Author Affiliation(s): Primary:
Yale University, Department of Geology and Geophysics, New Haven, CT, United States
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English. 2 refs.
Summary: Early Paleogene hyperthermal events were perturbations of the global carbon cycle of varying magnitude, characterized by global warming and ocean acidification. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM; ≈ 55.9 Ma), with Eocene Thermal Event 2 (ETM2) ≈ 1.8 myr later. These events of different magnitude allow us to investigate whether the response of biota to hyperthermal events scales with the magnitude of the event (given by its carbon isotope excursion). During the PETM deep-sea benthic foraminifera suffered severe extinction; assemblages directly postdating the extinction have low diversity and high dominance of opportunistic taxa. Faunas had partially recovered before ETM2, but never recovered the full pre-PETM diversity. Across ETM2, assemblages at Walvis Ridge (SE Atlantic) Sites 1263 (paleodepth 1500m) and 1262 (paleodepth 3600m) (Jennions et al., 2015) and at Site 1209 (Shatsky Rise, subtropical Pacific, paleodepth 1900 m) and Site 1215 (tropical eastern Pacific Ocean) did not suffer extinction. All sites saw temporary declines in diversity and equity, increased abundance of low-food indicators, and declining benthic foraminiferal accumulation rates, possibly linked to increased remineralization in the water column (Lewis et al. 2017). ETM2 records for deep Pacific Site 1215 are incomplete, because the site was close to, and at times, below the CCD, but assemblages are similar to these at deeper Site 1262 (above the Atlantic CCD), with abundant oligotrophic taxa. ETM2 assemblages at Site 1209 and 1263 both have more rectilinear and buliminid taxa than the deeper sites, indicative of a higher food supply. Site 1263, the shallowest of the studied sites, saw a much more severe decline in diversity and abundance of benthic foraminifera than Site 1209, and than both deeper sites. Deep-sea benthic assemblages thus show no simple correlation between the magnitude of hyperthermal events and that of the global biotic response, but have strong geographic and bathymetric variability. Jennions, S. M., Thomas, E., Schmidt, D. N., Lunt, D., and Ridgwell, A., 2015, Paleoceanography, 30 1059-1077 Lewis, A., Griffith, E. M., Thomas, E., and Winguth, A., 2017. Marine Export Production and Remineralization during early Eocene hyperthermal events. AGU, this session.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Assemblages; Atlantic Ocean; Benthic taxa; Cenozoic; East Pacific; Eocene; Foraminifera; Leg 198; Leg 199; Leg 208; Marine environment; Microfossils; North Pacific; Northeast Pacific; Northwest Pacific; ODP Site 1209; ODP Site 1215; ODP Site 1262; ODP Site 1263; Ocean Drilling Program; Pacific Ocean; Paleoclimatology; Paleoecology; Paleoenvironment; Paleogene; Shatsky Rise; South Atlantic; Tertiary; Walvis Ridge; West Pacific
Coordinates: N260200 N260200 W1475600 W1475600
N323900 N324000 E1583100 E1583000
S271100 S271100 E0013500 E0013400
S283200 S283200 E0024700 E0024700
Record ID: 2018093730
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