| Autor: |
Jan Pašava, Heinrich Taubald, Kerstin Drost, Martin Wille, Daniel Schoeckle, Florian Kurzweil, Ronny Schoenberg |
| Rok vydání: |
2015 |
| Předmět: |
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| Zdroj: |
Geochimica et Cosmochimica Acta. 171:121-142 |
| ISSN: |
0016-7037 |
| DOI: |
10.1016/j.gca.2015.08.022 |
| Popis: |
The Earth’s atmosphere and hydrosphere changed from an Archean anoxic to a modern oxygenated world in two major steps, the Paleoproterozoic Great Oxidation Event (2.4–2.3 billion years ago) and the Neoproterozoic Oxidation Event (0.8–0.5 billion years ago). Both events had a strong influence on the availability of redox sensitive and bio-essential metals within the ocean and are, thus, strongly linked to fundamental biological innovations and diversification. Biological diversification during the Precambrian–Cambrian transition between 555 and 540 million years ago may have been driven by ocean–atmosphere oxygenation. The exact timing and the extent of (deep) ocean oxygenation within this time period remains unresolved though. Here we present major and trace element compositions as well as Mo, S and Fe isotopic data of organic-rich black shales from the Tepla-Barrandian unit, Czech Republic. New in situ zircon U–Pb ages provide a maximum depositional age of 559.8 ± 3.8 million years. Black shales with strong metal enrichment show low δ56Fe values due to the dominance of authigenic pyrite-Fe with δ56Fe values around −0.6‰ over detrital Fe with δ56Fe values around 0.1‰. Samples with lower authigenic metal enrichment show relatively low Mo/TOC ratios and increasing δ34S values, which is interpreted to reflect basinal restriction and longer seawater renewal times. In analogy to the modern Black Sea, the accompanied depletion of basinal Moaq due to near quantitative Mo removal might have led to the preservation of the seawater δ98Mo in the respective black shales. Our best estimate for this seawater Mo isotopic composition |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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