New age for ferromanganese crust 109D-C and implications for isotopic records of lead, neodymium, hafnium, and thallium in the Pliocene Indian Ocean

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doi: 10.1029/2010PA002003
Author(s): Nielsen, Sune G.; Gannoun, Abdelmouhcine; Marnham, Charles; Burton, Kevin W.; Halliday, Alex N.; Hein, James R.
Author Affiliation(s): Primary:
University of Oxford, Department of Earth Sciences, Oxford, United Kingdom
U. S. Geological Survey, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 26(2). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 80 refs.; illus., incl. 2 tables
Summary: This study presents a high-resolution record of osmium and thallium isotopes in a ferro-manganese (Fe-Mn) crust from the Indian Ocean, Antipode 109D-C. These results, when combined with additional new Os isotope data from ODP Hole 756B in the southeast Indian Ocean, define a new best estimate for the age at the base of this crust of ∼6.5 Ma, which is significantly different from a previous estimate of ∼15 Ma based on Co-flux modeling. The Tl isotope record obtained for the Indian Ocean resembles that for the Pacific Ocean with a small but well-defined increase occurring over the last ∼5 Myr. This contrasts with two records from the Atlantic Ocean which do not have resolvable variations. Ocean basin-scale Tl isotope variation may be inconsistent with the inferred modern marine residence time for Tl of ∼20 kyr but could be explained by an increase in ocean crust production rates in the Pacific and Indian oceans since ∼10 Ma. The improved age model for 109D-C reveals that the Hf isotope composition of Indian Ocean bottom waters has remained homogenous over the last ∼6 Myr. Thus, this isotope system does not bear any evidence that the influence of North Atlantic Deep Water in the formation of Indian Ocean bottom waters has changed during that time. However, because of the lack of knowledge about Hf isotopes as a tracer of ocean circulation, we cannot conclude that export of NADW decreased over the last 6 Myr.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Age; Cenozoic; Ferromanganese crusts; Geochemistry; Hafnium; Hf-177/Hf-176; Indian Ocean; Isotope ratios; Isotopes; Lead; Leg 121; Metals; Miocene; Nd-144/Nd-143; Neodymium; Neogene; Ninetyeast Ridge; ODP Site 756; Ocean Drilling Program; Os-188/Os-187; Osmium; Paleo-oceanography; Pb-206/Pb-204; Pb-208/Pb-206; Platinum group; Pliocene; Radioactive isotopes; Rare earths; Southwestern Indian Ocean; Stable isotopes; Tertiary; Thallium; Tl-205/Tl-203; Upper Miocene
Coordinates: S272120 S272115 E0873554 E0873548
S275800 S275800 E0604800 E0604800
Record ID: 2013035826
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