Changes in organic carbon stable isotope ratios across the K/T boundary: global or local control?
نویسنده
چکیده
Meyers, P.A., 1992. Changes in organic carbon stable isotope ratios across the K/T boundary: global or local control? In: S.A. Macko and M.H. Engel (Guest-Editors), Isotope Fractionations in Organic Matter: Biosynthetic and Diagenetic Processes. Chem. Geol. (Isot. Geosci. Sect. ), l 01: 283-29 I. A global shift in carbonate carbon j~3C-values from heavier values in the Maastrichtian to lighter values in the early Danian indicates recycling of isotopically light organic carbon to inorganic carbon reservoirs during a period of depressed marine productivity. Comparison of organic carbon t~3C-values from globally dispersed K/T sections does not show a similar, globally well-developed pattern. Several factors evidently overwhelm the potential impact of an isctopically lighter inorganic carbon source on organic matter isotopic signatures: ( 1 ) species changes in biological assemblages may modify the averaged isotopic fractionation of organic matter; and (2) shifts in the proportion of land/marine organic matter contributions to coastal marine locations may overprint the isotopic record. Local phenomena evidently outweigh global change in determining the isotope signature of organic carbon deposited in K/T boundary sections.
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