- 责任者：Cao Changqun (State Key Laboratory of Paleobiology and Stratigraphy ; Nanjing Institute of Geology and Palaeontology ; CAS ; Nanjing 210008 ; China) ; Zhang Mingyuan
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(10)
- 关键词：白云岩 ; dolostone ; 泥质结构 ; argillaceous texture ; 湖南 ; Hunan Province
- 页码：p.3649-3657
- 图表：4 illus., 1 table, 39 refs.
- 分类号：0803
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
The Rencunping （RCP） section in Sangzhi of Hunan Province is a typical location developing a set of organic-rich siliceous deposits in the middle part of Maokou Formation, significantly, which is intermitted with several dolomite beds. Micromorphologic features of dolomitic crystallites present poorly-ordered and aphanitic textures in the form of anhedral clusters, which is distinctly different from the rhomboidal textures formed in diagenesis. These features might evidently indicate that organogenic dolomitization occurred in the environment of oxidation of burial organic matters by bacterial sulfate reduction in sedimentary pore water. In addition, negative relationship of δ^13C vs. δ^180 values has been detected in the entire siliceous-rock interval. We infer that should be the results also from the enhanced influences of SRB processes of burial organic matters. The occurrence with relatively high δ^18O values in the bioclastic dolomites might track the O-isotopic compositions back in the shallow-water environments indicating unique fractionating pathway on degradations of organic matters after reworking. The abnormalities with relatively low δ^13 C values occurred distinctively in the dolomite beds at sampling positions of 4. 5m and 5.9m, which should mark the dominance of anoxic oxidation of methane （AOM） releasing from the underlying layers. Due to poor conditions in terms of porosities and availabilities of precipitated carbonates in the rocks of marls and calcareous mudstone, inwhere it prevented the activities of SRB to form the organogenic dolomite, alternatively, to be replaced by methanogensis in deep burial depth to derive^ 13 C-enriched DIC in alkaline pore fluids. Therefore, the consistent evidence mentioned above inferred that the depositional environment of the siliceous-rock set in Rencunping section was preferably in the slope facies in cases of enhanced supplies and deposits of organic matters.