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The abnormal distribution of the molecular fossils in the pre-Cambrian and Cambrian: its biological significance |
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| Authors: | |
| Institution: | 1. Research Institute of Petroleum Exploration and Development of China, Beijing 100083, China;Key Laboratory of Petroleum Geochemistry, China National Petroleum Corporation, Beijing 100083, China 2. Department of Geological and Environment Sciences, Stanford University, Stanford, CA 94305-2115, USA 3. Geological Survey of Canada, 3303-33St. NW Calgary, Alberta, Canada, T2L 2A7 4. Department of Earth Sciences, Nanjing University, Nanjing 210093, China 5. Research Institute of Petroleum Exploration and Development of China, Beijing 100083, China 6. Department of Earth Sciences, Petroleum University, Beijing 102200, China |
| Abstract: | Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference. |
| Keywords: | dinosteranes triaromatic dinosteroids 24-norcholestane dinoflagellate diatom Cambrian Tarim Basin |
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