نتایج جستجو برای: dolostone

تعداد نتایج: 108  

2003
John A. Higgins Daniel P. Schrag

[1] Using a simple 3-box model of the ocean-atmosphere system, we simulate the cycling of carbon and strontium in the aftermath of a global glaciation. Model simulations include the delivery of alkalinity to seawater from intense carbonate and silicate weathering under high pCO2 conditions as well as ocean mixing, air-sea gas exchange, and biological productivity. The dC of the first carbonate ...

Journal: :Scientific Journal of Riga Technical University. Environmental and Climate Technologies 2012

Journal: :Communications earth & environment 2023

Abstract The lithium isotope composition (δ 7 Li) of seawater records important information on the evolution carbon and silicon cycles over geologic time. Here we report δ Li values in a suite Neogene dolostones (23–3.4 Ma, n = 39) from South China Sea. Over Neogene, dolostone have increased 24.9‰ to 30.1‰, overlapping previously published foraminifera documenting without applying any isotopic ...

2004
Shuhai Xiao Huiming Bao Haifeng Wang Alan J. Kaufman Chuanming Zhou Guoxiang Li Xunlai Yuan Hongfei Ling

The Neoproterozoic Quruqtagh Group in eastern Chinese Tianshan consists of, in ascending order, the Bayisi, Zhaobishan, Altungol, Tereeken, Zhamoketi, Yukkengol, Shuiquan, and Hankalchough Formations. Diamictite units occur in the Bayisi–Altungol, Tereeken, and Hankalchough Formations. Our field observations confirm the glacial origin of the Tereeken and Hankalchough diamictites, but the glacia...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2013
Bryan A Killingsworth Justin A Hayles Chuanming Zhou Huiming Bao

The ~635 Ma Marinoan glaciation is marked by dramatic Earth system perturbations. Deposition of nonmass-dependently (17)O-depleted sulfate (SO4(2-)) in worldwide postglacial sediments is, thus far, unique to this glaciation. It is proposed that an extremely high-pCO2 atmosphere can result in highly (17)O-depleted atmospheric O2, or the Marinoan Oxygen-17 Depletion (MOSD) event. This anomalous (...

2004
Galen P. Halverson Adam C. Maloof Paul F. Hoffman

Two separate and distinct diamictite-rich units occur in the mixed carbonate-siliciclastic PolarisbreenGroup, which comprises the top kilometer of47 km of Neoproterozoic strata in the northeast of the Svalbard archipelago.The platformal succession accumulated on the windward, tropical to subtropical margin of Laurentia.The older PetrovbreenMember is a thin glacimarine diamictite that lacks a ca...

2014
Matthew S. Fantle John Higgins

The Ca, Mg, O, and C isotopic and trace elemental compositions of marine limestones and dolostones from ODP Site 1196A, which range in depth ( 58 to 627 mbsf) and in depositional age ( 5 and 23 Ma), are presented. The objectives of the study are to explore the potential for non-traditional isotope systems to fingerprint diagenesis, to quantify the extent to which geochemical proxies are altered...

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