Helium isotopes in marine sediments as tracers of continental input, accumulation and provenance over the last 6 Ma
Abstract
The Miocene to Pleistocene marks a transition from warm, humid, low orbital frequency driven climate regime to cooler, more arid, northern glaciation driven climate regime, with marked change occurring between the late Pliocene through the early Pleistocene. In this study, we use helium isotopes at IODP site U1313 in the sub-polar North Atlantic Ocean to reconstruct a record of input, accumulation and provenance of detrital material over the last 6 Ma. Our record indicates a gradual increase in terrigenous flux concomitant with the cooling climatic regime from the late Pliocene that culminated into northern glaciation through the Marine Isotope Stage (MIS) 8 in the late Pleistocene. The increased accumulation of terrestrial material resulted in a switch from a carbonate controlled to a more clay controlled sedimentation pattern at site U1313 ~ 1 Ma. There is an abrupt increase in terrigenous flux ~ 2.4 Ma followed by at least four such instances through the late Pleistocene. The dramatic increase in terrigenous flux starting at 2.4 Ma and temporal evolution of 4He henceforth is concomitant with the onset and periodic growth of ice sheets in the northern hemisphere. The composition of detrital sediments that is have eroded and been deposited at site U1313 is reflects reorganization of ocean circulation in the sub-polar North Atlantic that in turn is related to expansion of the ice sheets in the northern hemisphere.; Co-variation of 4He flux and 4He normalized to the clay fraction [4HeTerr]N over the last 6 Ma (age model of Lissecki and Raymo, 2005). Onset of northern glaciation during the Pleistocene (∂18O of Lissecki and Raymo, 2005) is accompanied by high 4He fluxes
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP51B2116B
- Keywords:
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- 4863 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Sedimentation;
- 4926 PALEOCEANOGRAPHY / Glacial;
- 4936 PALEOCEANOGRAPHY / Interglacial;
- 4940 PALEOCEANOGRAPHY / Isotopic stage