Characteristics and sedimentary environment of fine-grained sedimentary rocks in continental rift-subsidence saline lacustrine basin:a case study of H3Ⅲ submember of Hetaoyuan Formation in Biyang Sag
Fine-grained sedimentary rocks widely developed in the third Member of Paleogene Hetaoyuan Formation in Biyang Sag,a typical continental rift-subsidence saline lacustrine basin in China.With the use of continuous core data of long well sections,thin section observation,two-dimensional XRF scanning,XRD analysis,scanning electron microscopy and geochemical testing data,this paper divided the fine-grained sedimentary rocks of H3 Ⅲ submember in Biyang Sag into nine lithofacies types on the main basis of mineral composition,sedimentary structure and grain size.Among them,laminated mixed shale and laminated felsic shale are the most developed types of fine-grained sedimentary rocks.The evolutionary characteristics of sedimentary environment are analyzed through the vertical changes of geochemical indexes such as Mg/Ca,Al content,Ti content,(Fe+Al)/(Ca+Mg),P/Ti,Sr/Ba,and V/(V+Ni)and the lithofacies combination.The sedimentary environment of H3 Ⅲ submember of Biyang Sag is a semi-deep lake to deep lake environment,with its salinity being semi-saline to saline water.The terrestrial inputs are strong in general,and the climate change is relatively large.From bottom to top,it has undergone climate changes of drought,drought-wetting alternation,wetting,and drought.The vertical change of lithofacies is influenced by climate,terrestrial inputs,water depth and water salinity.The climate,terrestrial inputs and water depth determine the contents of felsic minerals and clay minerals,and the content of carbonate minerals is mainly influenced by water salinity and climate.
fine-grained sedimentary rocksmixed shalefelsic shaleHetaoyuan FormationBiyang Sag
NETL
NSTL
万方数据
