Osmium-isotope evidence for volcanism, weathering, and ocean mixing during the early Aptian OAE 1a

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doi: 10.1130/G33140.1
Author(s): Bottini, Cinzia; Cohen, Anthony S.; Erba, Elisabetta; Jenkyns, Hugh C.; Coe, Angela L.
Author Affiliation(s): Primary:
Universita di Milano, Dipartimento di Scienze della Terra Ardito Desio, Milan, Italy
Open University, United Kingdom
University of Oxford, United Kingdom
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 40(7), p.583-586. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. With GSA Data Repository Item 2012176; accessed on July 26, 2012. 29 refs.; illus., incl. strat. col.
Summary: The early Aptian Oceanic Anoxic Event (OAE 1a) resulted from an exceptional set of interactions between the geosphere, the biosphere, and the ocean-atmosphere system. We present new Re-Os data from two sites spanning OAE 1a in the Tethys and Pacific Oceans. The patterns of variation in the seawater Os-isotope composition from both sites are very similar, and together they constrain the timing and duration of continental weathering in relation to the large-scale volcanic activity of the Ontong Java Plateau. The dominant feature through the OAE is an interval of ∼880 k.y. when the Os-isotope composition of the global ocean was exceptionally unradiogenic, implicating unambiguously the Ontong Java Plateau as the trigger and sustaining mechanism for OAE 1a. A relatively short-lived (∼100 k.y.) Os-isotope excursion to radiogenic compositions in the Tethyan record is clearly linked to an abrupt perturbation to the global carbon cycle, and is fully consistent with the Pacific record. These highly distinctive features of seawater Os in contemporaneous samples from three high-resolution sections, two of which were very remote from the Ontong Java Plateau, indicate that ocean mixing at that time was very efficient. The results suggest that OAE 1a was also related to rapid global warming and elevated rates of silicate weathering both on the continents and in the oceans.
Year of Publication: 2012
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Aptian; Carbon; Carbon cycle; Chemostratigraphy; Cismon del Grappa Italy; Climate change; Cretaceous; DSDP Site 463; Deep Sea Drilling Project; Europe; Geochemical cycle; Geochemistry; Global change; Global warming; High-resolution methods; IPOD; Isotope ratios; Isotopes; Italy; Leg 62; Lower Aptian; Lower Cretaceous; Marine environment; Mesozoic; Metals; Mid-Pacific Mountains; Mixing; North Pacific; Northwest Pacific; OAE 1a; Oceanic anoxic events; Ontong Java Plateau; Os-188/Os-187; Osmium; Pacific Ocean; Paleo-oceanography; Paleocirculation; Paleoclimatology; Platinum group; Re/Os; Southern Europe; Stable isotopes; Tethys; Veneto Italy; Volcanism; Weathering; West Pacific
Coordinates: N212101 N212101 E1744004 E1744004
N455500 N455500 E0114400 E0114400
Record ID: 2012073116
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