Organic petrology and geochemistry of Eocene Suzak bituminous marl, north-central Afghanistan: Depositional environment and source rock potential
| Autor: | John R. SanFilipo, Paul C. Hackley |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
020209 energy
Stratigraphy Geochemistry 02 engineering and technology 010502 geochemistry & geophysics Oceanography 01 natural sciences Sedimentary depositional environment Foraminifera Paleontology Sterane chemistry.chemical_compound Marl Organic geochemistry 0202 electrical engineering electronic engineering information engineering Vitrinite Petrology 0105 earth and related environmental sciences biology Geology biology.organism_classification Hopanoids Geophysics Source rock chemistry Economic Geology |
| Zdroj: | Marine and Petroleum Geology. 73:572-589 |
| ISSN: | 0264-8172 |
| DOI: | 10.1016/j.marpetgeo.2016.02.029 |
| Popis: | Organic geochemistry and petrology of Eocene Suzak bituminous marl outcrop samples from Madr village in north-central Afghanistan were characterized via an integrated analytical approach to evaluate depositional environment and source rock potential. Multiple proxies suggest the organic-rich (TOC ∼6 wt.%) bituminous marls are ‘immature’ for oil generation (e.g., vitrinite Ro 1) indicating organic input from marine algae and/or bacterial biomass, and sterane/hopane ratios are low (0.12–0.14). Monoaromatic steroids are dominated by C28 clearly indicating a marine setting. High gammacerane index values (∼0.9) are consistent with anoxia stratification and may indicate intermittent saline-hypersaline conditions. Stable C isotope ratios also suggest a marine depositional scenario for the Suzak samples, consistent with the presence of marine foraminifera including abundant planktic globigerinida(?) and rare benthic discocyclina(?) and nummulites(?). Biomarker 2α-methylhopane for photosynthetic cyanobacteria implies shallow photic zone deposition of Madr marls and 3β-methylhopane indicates presence of methanotrophic archaea in the microbial consortium. The data presented herein are consistent with deposition of Suzak bituminous marls in shallow stratified waters of a restricted marine basin associated with the southeastern incipient or proto-Paratethys. Geochemical proxies from Suzak rock extracts (S content, high polar content, C isotopes, normal (αααR) C27–29 steranes, and C29/C30 and C26/C25 hopane ratios) are similar to extant data from Paleogene oils produced to the north in the Afghan-Tajik Basin. This observation may indicate laterally equivalent strata are effective source rocks as suggested by previous workers; however, further work is needed to strengthen oil-source correlations. |
| Databáze: | OpenAIRE |
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