Modelling changes of the Paleogene Ca budget using benthic Foraminifera

Author(s): Pabich, Stephanie; Gussone, Nikolaus C.; Vollmer, Christian; Palike, H.; Rabe, K.; Teichert, Barbara M.
Author Affiliation(s): Primary:
Universitat Muenster, Muenster, Germany
MARUM, Germany
Leibniz University of Hannover, Germany
Volume Title: AGU 2014 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2014; American Geophysical Union 2014 fall meeting, San Francisco, CA, Dec. 15-19, 2014. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Understanding the Earth's climate as well as the oceanic chemical and isotopic evolution in the past is one of the main aims in earth science. Ca as one of the major elements in the ocean is especially important. Its variation in concentration are controlled by different factors including the CO2 concentration of the atmosphere, continental weathering and Ca carbonate sedimentation. We used samples from IODP Exp. 320/321 to establish a δ44/40Ca paleo-seawater record between 45 and 25 Ma and model changes in the Ca budget through time. Our results show differences in the Eocene and Oligocene Ca isotope record of benthic foraminifers. The δ44/40Ca values during the Eocene are relatively constant with no significant fluctuations during phases of large short term CCD fluctuations. The Oligocene is characterized by sediments with uniformly high carbonate content and increasing δ44/40Ca towards the late Oligocene. Past seawater δ44/40Ca values were calculated from the measured benthic foraminifer record applying the calibration for Gyroidinoides spp. The Ca budget during the Eocene is relatively constant and not affected by short term CCD fluctuations, indicating that they are too small to alter the isotopic Ca budget. The Oligocene, in contrast is characterized by a general increase in δ44/40Ca seawater values and a continuously deep CCD. This is consistent with a massive long term (>1 Ma) CaCO3 deposition and decreasing Ca concentration in the ocean water. To examine the preservation (dissolution and recrystallization) of the foraminifer test through time, we studied additionally the changes in the crystallographic orientations trough time by Electron Backscatter Diffraction (EBSD) analysis and Raman spectroscopy. As a final step we use our δ44/40Ca seawater record to run a combined Ca and C model showing the effect of Ca weathering input, carbonate remobilization and dolomitization on the Ca and carbonate system of seawater.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; East Pacific; Expedition 320; Expeditions 320/321; Foraminifera; Integrated Ocean Drilling Program; Invertebrata; Microfossils; North Pacific; Northeast Pacific; Pacific Ocean; Paleogene; Protista; Tertiary
Coordinates: N051844 N120405 W1261700 W1420942
Record ID: 2015117274
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