Provenance Analysis And Sedimentary Characteristics Of Paleogene Xiaganchaigou Formation In Ganchaigou Area, Western Margin Of Qaidam Basin

The lower member of the Palaeogene Xiaganchaigou Formation,as the majoy oil-produce layer of oil field in the Qaidam Basin,has a great potential for exploitation.It will be of great significance for the research of Spatial distribution of sand body to study material source and distribution of sedimentary facies.Based on digesting the research result of predecessors,combined comprehensive analysis of field geological of outcrops,observation and description of core,and Laboratory analysis test,by means of statistical information and contrastive analysis, the characteristics of Sedimentary and source of Lower Ganchaigou Formation in West of Qaidam Basin were discussed, in addition,the source direction,tectonic setting and the nature of source rock of Lower Ganchaigou Formation in West of Qaidam Basin were also clear.That the sedimentary facies and facies distribution pattern were indicated from the macroscopic point of view,provide the basis for the distribution of sand bodies of Lower Ganchaigou Formation in study area.The Lower Ganchaigou Formation is sedimentary clastic sequence in study area. The main types of the sandstone are feldspar debris sandstone, debris feldspar sandstone, and debris sandstone.Detrital component of rocks are main lithic fragment that account for 23%-57%. The psephicity of detrital grain is mainly Angular-Subangular,the sorted is poorly and the compositional maturity and texture maturity of clastic rock are both low.Research on provenances indicates the Altyn Tagh Range direction is the majoy sediment resources of the Lower Ganchaigou Formation.The lithic fragments come from metamorphic rocks of Proterozoic and Ordovician,which are exposed in Altun Mountain.The structural setting of provenance is Transitional archipelagic oceanic basin,The source rock is manly from Granite in the earth’s crust、felsic volcanic rocks and Medium and basite,That the sedimentary environment is weak oxidation – reduction, is conducive to gathering and preserving for organic material.The lithological characteristics,sedimentary structure and well log characteristics of the Lower Ganchaigou Formation, Indicates the types of sedimentary facies are a set of alluvial fan facies,fan delta and lacustrine facie and so on in the Lower Ganchaigou Formation. The Lower Ganchaigou Formation of Facies profile is retrogradtional fan deltas under the background of lake invasion.The sedimentary faces of single well and joint well Indicates The study area was surrounded by alluvial fans of Altun Mountains and Qimantag Mountains,while the sedimentary center was lacustrine. The sedimentary mode of fan-fan delta-lacustrine in period of Lower Ganchaigou Formation had been established on this.