Using Helium Isotopes in marine sediments as tracers of continental inputs, provenance, and accumulation over the last 7Ma
Abstract
Linking changes in Northern Hemisphere ice sheet growth and ocean circulation to 7 to 8Ma long Chinese Loess records are critical for understanding potential impacts of monsoon development, westerly circulation, aridity, and Tibetan Plateau uplift (e.g. Sun, et al. 2008). Here, we use the helium isotopic composition of marine sediments at two sites, IODP Site 1313 (41N, 32W at location of DSDP Site 607) from the North Atlantic and ODP Site 885/886 over the last 6.2 and 7 Ma, respectively. Helium isotope analyses provide estimates of detrital inputs from 4He (Patterson and Farley, 1999), MAR from 3He derived from interplanetary dust (Higgins, 2001, Marcantonio et al., 1996), and provenance changes from 3He/4He ratios. The distal eolian record of Rea et al. (1998) at ODP Site 885/886 (45N, 168E) suggests a large step-wise increase in dust at 3.6Ma that marked a change in aridity and plateau uplift. He isotope analyses by Higgins (2001 and this study) confirmed the quantity of eolian materials but proposed a more gradual rise in eolian accumulations at Site 885/886 since 7Ma. IODP Site 1313 stratigraphy can be tied directly to global benthic isotope records (Lisiecki and Raymo, 2005) for the last 6Ma and provides a distal view of detrital inputs from the N. hemisphere ice sheets via formation/overflow of NADW linked to glacier growth and sea level. 4He isotope and 3He/4He ratios results at Site 1313 (this study and Farley,1995) indicate a dramatic swing from a predominantly basaltic end member to one increasingly continental at 3.6 Ma. The 6 Ma record is punctuated by increases in continental sources at 4.8 to 5.2 Ma, 2.5 to 2.7 Ma, 1.8Ma, 1 to 1.2Ma, 0.5 to 0.6 Ma. K/Ar analyses on select samples supports these 3He/4He results. The timing and pattern of detrital sources/MAR to 885/886 and 1313 are very similar for the last 6 Ma. Combining atmospheric records from distal N. Pacific with this distal sediment transport record from N. Atlantic suggests a very tight coupling of N. Hemisphere glacier growth, sea level changes, ocean circulation and atmospheric changes with little time for significant lead/lags with identified periods of Tibetan uplift.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP13A1431H
- Keywords:
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- 1029 Composition of aerosols and dust particles;
- 1105 Quaternary geochronology;
- 2129 Interplanetary dust;
- 4870 Stable isotopes (0454;
- 1041);
- 4924 Geochemical tracers