Evaluating Eastern Equatorial Pacific Export Production over the Middle Miocene, 18-13 Ma, Using Time Series Analyses and Barite Mass Accumulation from IODP Sites U1335, U1337, U1338
Abstract
Barite mass accumulation rates (BAR) in marine pelagic sediments have been established as a useful proxy for past export production, an important flux of carbon out of the surface ocean during the Middle Miocene. Previous work by the coauthors using a high-resolution BAR proxy record of export production spanning the Middle Miocene Climate Transition (MMCT; 14.02 - 13.43 Ma) from Integrated Ocean Drilling Program (IODP) Site U1337 showed a very large BAR peak (~40 mg cm-2 k.y.-1) relative to an already elevated baseline (5.9 mg cm-2 k.y.-1), corresponding to an increase in export production during the CM6 excursion, one of the high-frequency maxima events superimposed on the long positive δ13C excursion called the "Monterey event." During this time interval, it was suggested that a more efficient biological pump, sustained by an increased supply of limiting nutrients due to changing ocean circulation, resulted in increased carbon burial via export from the euphotic zone, which could have contributed to global cooling during the MMCT. However, important questions remain regarding the role of export production in the carbon cycle during the larger period of Middle Miocene climate change from 18-13 Ma. Using time series analysis of XRF core scans from IODP Sites U1335, U1337, and U1338, in combination with existing records of biogenic silica, δ18O, δ13C, and CaCO3, we will interpret changes in export production over this larger interval and examine the contribution of orbital cycles such as long eccentricity (400 k.y.). These new analyses will help to determine if changes to the biological pump were isolated to the CM6 event or speak to longer-term changes in the carbon cycle of the eastern equatorial Pacific during the Middle Miocene. Conclusions from these analyses may help resolve whether the eastern equatorial Pacific acted as a carbon sink driving cooling or if it was responding to changes elsewhere in the Earth system.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMPP0010007B
- Keywords:
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- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY;
- 4930 Greenhouse gases;
- PALEOCEANOGRAPHY;
- 4950 Paleoecology;
- PALEOCEANOGRAPHY;
- 4954 Sea surface temperature;
- PALEOCEANOGRAPHY