Towards establishing decadal-timescale atmospheric CO2 records during the Middle Miocene Climate Optimum
Abstract
The middle Miocene Clarkia Lake deposit (ca. 15 Ma) registers a carbon cycle perturbation and climate change triggered by the volcanism form ing the Columbia River Basalt in the northwest USA. The initial formation of the lake was attributed to the flood basalt flow that dammed a local drainage. Presumably, t herapid atmospheric CO2release and subsequent consumption through a variety of processes provide a unique opportunity to examine the fate of a CO2pulse, with important implications for our future . Interleaved varve-like laminated successions may represent seasonal deposition changes. Petrographic analysis strengths this hypothesis as the difference in mineral assemblage between the organic-rich, dark, very fine-grained, and quartz-rich, light, coarse-grained layers is only given by particle size and fossil content. Such a pattern strongly suggests changes in transportation energy rather than sedimentary sourcing. Similar results are obtained via X-Ray Fluorescence scanning (XRF), in which elemental ratios of S/Rb delineate differences into grain-size and fossil abundance throughout the lake deposit. Abundant and exquisitely preserved fossil leaves of warm-temperate species, found in the very fine-grained layers, were employed to reconstruct the CO2changes on decadal to centennial timescales . Preliminary results based on δ13C of several drought-intolerant conifer species (δ13Cleaf) show increases of isotopic values from the bottom towards the top of the section, which would suggest a drawdown of the CO2according to the C3 plant Δ13C proxy. This notion is supported by initial stomatal analyses also employed for reconstructing pCO2.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A21N2762H
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE