Griffith, Elizabeth M.; Paytan, Adina; Eisenhauer, Anton; Bullen, Thomas D.; Thomas, Ellen (2011): Seawater calcium isotope ratios across the Eocene-Oligocene transition. Geological Society of America (GSA), Boulder, CO, United States, Geology (Boulder), 39 (7), 683-686, georefid:2011-064708

Abstract:
During the Eocene-Oligocene transition (EOT, ca. 34 Ma), Earth's climate cooled significantly from a greenhouse to an icehouse climate, while the calcite (CaCO (sub 3) ) compensation depth (CCD) in the Pacific Ocean increased rapidly. Fluctuations in the CCD could result from various processes that create an imbalance between calcium (Ca) sources to, and sinks from, the ocean (e.g., weathering and CaCO (sub 3) deposition), with different effects on the isotopic composition of dissolved Ca in the oceans due to differences in the Ca isotopic composition of various inputs and outputs. We used Ca isotope ratios (delta (super 44/40) Ca) of coeval pelagic marine barite and bulk carbonate to evaluate changes in the marine Ca cycle across the EOT. We show that the permanent deepening of the CCD was not accompanied by a pronounced change in seawater delta (super 44/40) Ca, whereas time intervals in the Neogene with smaller carbonate depositional changes are characterized by seawater delta (super 44/40) Ca shifts. This suggests that the response of seawater delta (super 44/40) Ca to changes in weathering fluxes and to imbalances in the oceanic alkalinity budget depends on the chemical composition of seawater. A minor and transient fluctuation in the Ca isotope ratio of bulk carbonate may reflect a change in isotopic fractionation associated with CaCO (sub 3) precipitation from seawater due to a combination of factors, including changes in temperature and/or in the assemblages of calcifying organisms.
Coverage:
West: -135.2200 East: -133.1948 North: 8.5300 South: 4.1231
Relations:
Expedition: 199
Site: 199-1218
Expedition: 85
Site: 85-574
Supplemental Information:
With GSA Data Repository Item 2011210
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.1130/G31872.1 (c.f. for more detailed metadata)
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