Organic matter accumulation in the oil shale- and coal-bearing Huadian Basin (Eocene; NE China)

• Published in: International journal of coal geology 2013-01, Vol.105, p.1-15
• Main Authors: Sun, Pingchang, Sachsenhofer, Reinhard F., Liu, Zhaojun, Strobl, Susanne A.I., Meng, Qingtao, Liu, Rong, Zhen, Zhen
• Format: Article
• Language: English
• Subjects: Basin evolution; China; Coal; Earth sciences; Earth, ocean, space; Eocene; Exact sciences and technology; Kerogen type; Lacustrine environment; Oil shale; Pull-part basin; Sedimentary rocks; Sequence stratigraphy; Stratigraphy
• ISSN: 0166-5162; 1872-7840
• DOI: 10.1016/j.coal.2012.11.009

The Huadian Basin, located in northeastern China, is a fault-controlled basin filled by Eocene non-marine sediments assigned to the Huadian Formation. The formation is subdivided from bottom to top into three members: Pyrite Member, Oil Shale Member, and Carbonaceous Shale Member. Using bulk geochemical data from borehole Hd3 and core descriptions from a high number of wells, the factors controlling organic matter accumulation have been evaluated. The organic matter content of the Pyrite Member is relatively low (average TOC: 0.9wt.%). Mudstones deposited in shallow lacustrine environments contain between 1 and 2wt.% TOC (max. 6wt.%) and a kerogen Type II (HI 400–600mg HC/g TOC). An arid climate prevented the accumulation of thick coal. The overlying Oil Shale Member contains 13 oil shale layers, which are mined underground. The Oil Shale Member has been interpreted as a 3rd order sequence. Significant differences exist between oil shales deposited in different systems tracts: 2-m-thick coaly oil shale of low-quality (oil yield 3.5wt.%) developed in the lowstand systems tract. Oil shale, up to 7m thick, of moderate quality (oil yield 4.1–8.0wt.%) was deposited during the transgressive systems tract (TST). Thinner (