Journal
INTERNATIONAL JOURNAL OF COAL GEOLOGY
Volume 141, Issue -, Pages 23-32Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.coal.2015.03.003
Keywords
Songliao Basin; Biomarker; Organic petrography; High resolution; Organic matter accumulation; Oil shale
Categories
Funding
- Unconventional Energy and Mineral Resources Evaluation project of China Geological Survey [1212011220800-02]
- Strategic Area Selection and Evaluation of China Petroleum Resource [1211302108025-5-1]
- Specialized Nonprofit Industry and Research Fund from the Ministry of Land and Resources of China [20121105104]
- National Natural Science Foundation of China [41402123]
- Austrian Exchange Service (OeAD)
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In the well-known continental Songliao Basin, the oil shale successions of the Cretaceous Qingshankou Formation are excellent source rocks for oil. The oil shale layers with high TOC (total organic carbon) contents developed at the bottom of the formation. They are divided into the lower oil shale (TOC up to 183%) and the upper oil shale layer (TOC up to 14.4%). The oil shale layers and accompanying mudstones are investigated by high resolution analyses of drill cores by pyrolysis, organic petrology, organic and inorganic geochemistry. The results demonstrate the predominance of type-I kerogen derived from algal-microbial mats (i.e. lamalginite). However, increased proportions of plant-derived organic matter are indicated by Rock-Eval parameters and the presence of vitrinite in the upper oil shale. As evidenced from lower concentrations of hopanes, higher sinking rates of organic matter (OM) are suggested to have been responsible for a lower extent of microbial degradation during accumulation of the lower oil shale unit. The environmental conditions are characterized by anoxic saline bottom water overlain by an extended zone of freshwater, favorable for OM production and preservation. Under these preconditions, oil shale thickness and quality are governed by primary productivity, related to accommodation space and nutrient supply. Redox conditions within the water column are the key factor controlling organic matter preservation. (C) 2015 Elsevier B.V. All rights reserved.
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