Deciphering the boron proxy records of the Paleocene-Eocene Thermal Maximum

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Author(s): Hoenisch, Baerbel; Haynes, Laura; Harper, Dustin T.; Penman, Donald E.; Holland, Katherine; Rosenthal, Yair; Zachos, James C.
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Columbia University of New York, United States
University of California-Santa Cruz, United States
Yale University, United States
Australian National University, Australia
Rutgers University, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Rapid surface ocean acidification at the PETM has been documented by pronounced decreases in the boron isotope and B/Ca proxies measured in surface dwelling planktic foraminifera (Babila et al., 2016; Penman et al., 2014). However, translating these geochemical signatures to past seawater carbonate chemistry is challenging due to the different-from-modern elemental and isotopic composition of seawater, in addition to the lack of constraints on vital effects in foraminifer species that are now extinct. While the pH decrease can be reasonably quantified from boron isotopes, the application of modern laboratory calibrations to translate the B/Ca signal yields unfeasible estimates, thus raising questions about how well we understand fundamental proxy systematics. Here we present a possible solution to this conundrum from laboratory culture experiments performed under simulated Paleocene seawater conditions, with lower [B] and [Mg], higher [Ca] and across a range of dissolved inorganic carbon and pH. These experiments suggest that raising DIC in addition to acidification amplifies the B/Ca decrease recorded in planktic foraminifera shells, thus providing an opportunity to deconvolve the B/Ca record into pH and DIC signals. Using the boron proxy records in ODP 1209 from Shatsky Rise in the Pacific Ocean as a case study, we will perform a series of sensitivity studies to better constrain the carbon perturbation at the PETM, and the long-term evolution of surface ocean chemistry from the Paleocene into the Eocene. Our results will be compared to LOSCAR model estimates of different carbon input scenarios at the PETM.
Year of Publication: 2016
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Boron; Cenozoic; Leg 198; North Pacific; Northwest Pacific; ODP Site 1209; Ocean Drilling Program; Pacific Ocean; Paleocene-Eocene Thermal Maximum; Paleoclimatology; Paleoecology; Paleogene; Shatsky Rise; Tertiary; West Pacific
Coordinates: N323900 N324000 E1583100 E1583000
Record ID: 2018006121
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