Dynamic, large-magnitude CCD changes in the Atlantic during the middle Eocene climatic optimum

Author(s): Kordesch, Wendy; Bohaty, Steven M.; Palike, Heiko; Wilson, Paul A.; Edgar, Kirsty M.; Agnini, Claudia; Westerhold, Thomas; Roehl, Ursula
Author Affiliation(s): Primary:
National Oceanography Centre, Southampton, United Kingdom
Other:
University of Southampton, United Kingdom
MARUM, Germany
Cardiff University, United Kingdom
University of Padua, Italy
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Middle Eocene Climatic Optimum (MECO; ∼40.1 Ma) is a transient global warming event that abruptly reversed the long-term Eocene cooling trend. The primary driving mechanism(s) must be linked to a CO2 increase; however, geochemical modeling experiments show that prevailing hypotheses are incompatible with the paleoclimate record. To further examine changes in deep-sea carbonate burial, we identify the MECO for the first time at ODP Site 929 (quatorial Atlantic; ∼3935 m paleodepth) and present new lithological and geochemical data for this site, including benthic foraminiferal stable isotopes (δ18O and δ13C), XRF scanning data, and an orbitally tuned age model. We combine these records with data from a suite of Atlantic sites to form a depth transect between ∼2-4 km (DSDP Site 523, ODP Site 1260 and 1263, IODP Site U1404) representing the first detailed record of carbonate dissolution in the Atlantic spanning the MECO. This compilation reveals dissolution at water depths as shallow as ∼2 km (>1 km shallower than previous estimates) with multiple and discrete short-lived (<100 kyr) phases of carbonate compensation depth (CCD) shoaling during and after the event. Careful reevaluation of the Pacific CCD records combined with new results suggests similar short-term variability and magnitude of shoaling globally. These data provide new constraints on carbon release history during the MECO and, potentially, the forcing mechanisms for warming. The transient CCD shoaling events indicate multiple pulses of carbon input and acidification decoupled from deep-sea δ18O and δ13C records, indicating that these events must not have been driven directly by changes in temperature or carbon burial/storage--potentially reconciling some of the data-model discrepancies.
Year of Publication: 2015
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Angola Basin; Atlantic Ocean; Carbonate compensation depth; Ceara Rise; Cenozoic; Cores; DSDP Site 523; Deep Sea Drilling Project; Demerara Rise; Eocene; Equatorial Atlantic; IPOD; Leg 154; Leg 207; Leg 208; Leg 73; Marine sediments; Middle Eocene; North Atlantic; Northwest Atlantic; ODP Site 1260; ODP Site 1263; ODP Site 929; Ocean Drilling Program; Paleogene; Sediments; South Atlantic; Tertiary; Walvis Ridge; West Atlantic
Coordinates: N055834 N055834 W0434423 W0434423
S283308 S283307 W0021504 W0021505
N091600 N091600 W0543300 W0543300
Record ID: 2016060044
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