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海洋有机碳的同位素特征比大多数陆生植物或陆源有机碳重,即富含~(13)C。因此,现代海洋沉积物中有机碳的δ~(13)C 值通常被用来说明保留在沉积物中有机质的陆源组份和洋海组份的相对含量。当用不同的地球化学方法研究白垩纪或更老的、主要含海洋有机碳的岩石中的有机物来源时,发现其δ~(13)C 值比那些主要含陆源的有机碳的轻,即δ~(13)C值更负。作者认为,中白垩世及更老的大洋中的光合作用通常形成较大的碳同位素分馏而造成δ~(13)C 值较轻的有机碳。现代海洋中的光合作可能正在一的反常的地质条件下进行,即大洋中陆原始繁殖半较高,Pco_2较低,只有有限的溶解二氧化碳可供光合作利用,从而降低了碳同位素的分馏作用。
The isotopic composition of marine organic carbon is heavier than most terrestrial or terrestrial organic carbon, ie rich in 13C. Therefore, δ ~ (13) C values of organic carbon in modern marine sediments are usually used to illustrate the relative content of terrigenous and oceanic components of organic matter retained in sediments. When using different geochemical methods to study organic sources in the Cretaceous or older rocks that mainly contain marine organic carbon, δ (13) C values were found to be lower than those of terrestrial-derived organic carbon, ie, δ ~ (13) C value is more negative. The authors suggest that photosynthesis in the Cretaceous and older oceans generally resulted in larger carbon isotope fractionations that resulted in lighter δ 13 C values. Photosynthesis in modern oceans may be under anomalous geological conditions, namely, that in the oceans, the original half-ground reproduction is higher and Pco_2 is lower, and only limited dissolved carbon dioxide is available for photosynthesis, thus reducing the fractionation of carbon isotopes .