کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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6430912 | 1634850 | 2010 | 9 صفحه PDF | دانلود رایگان |
For the first time we report δD of kerogen (δDkerogen) for three Permian-Triassic (P-Tr) sequences (Hovea#3, Perth Basin, Western Australia; Jameson Land, East Greenland and Lusitaniadalen, Spitsbergen). We have compared δDkerogen with δ13C of kerogen (δ13Ckerogen) and δ34S of total reduced inorganic sulfur (TRIS, essentially pyrite; δ34Spyrite) of all the sections and for one sample set with δ13C of carbonate (δ13Ccarbonate) to establish (i) similarities between the sections and (ii) evaluate whether these signals are local and/or global. Stable isotope shifts occur for all three sample sets either at the P-Tr transition (Western Australia) or coinciding with the marine ecosystem collapse (Spitsbergen and East Greenland). δDkerogen reflects organic matter (OM)/ kerogen type and is not sensitive to the low level of thermal maturation. Reliable palaeoenvironmental information in terms of the use of δD can therefore only be obtained for the P-Tr transition from hydrogen compound-specific isotope analyses (CSIA) of biomarkers (Nabbefeld et al., 2010b). The negative shifts in δ13Ccarbonate (primary) and δ13Ckerogen are attributed to the release of 13C-depleted carbon into the atmosphere, whereas the isotopic excursions in δ34Spyrite relate to palaeoredox changes. However, the global coincidence in timing of the shifts in δDkerogen, δ34Spyrite and δ13Ckerogen suggests a relation between the sulfur, carbon and hydrogen cycles. The negative shifts in δ13Ccarbonate (primary) are in general attributed to the release of 13C-depleted source of carbon into the oceans and atmosphere, whereas δ13Ckerogen can reflect the latter in certain cases, but can also be superimposed by varying sources of OM/kerogen type. Isotopic excursions in δ34Spyrite relate to global changes in the palaeoredox conditions that affect sulfur cycling in the ancient seas.
Journal: Earth and Planetary Science Letters - Volume 295, Issues 1â2, 15 June 2010, Pages 21-29