作者: P. L. deBoer
DOI: 10.1007/978-3-642-75829-4_34
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摘要: Pelagic sediments of Middle Cretaceous age in Umbria (Italy) exhibit a rhythmic pattern lithological alternations. The most conspicuous feature these alternations is regular fluctuation the carbonate content. Sediment intervals which were deposited during periods with limited renewal oxygen deep water, are characterized by relatively high amounts organic carbon, signs anoxity deposition, and low This valid for shorter (104 – 105 yr) as well longer (106 107 time periods.