Sedimentary facies of Paleogene Lulehe Formation in western segment of northern margin of Qaidam Basin

Based on outcrop observation,core description,well logging and seismic data,the sedimentary facies of Paleogene Lulehe Formation in northern margin Qaidam Basin is analyzed.Five types of seidimentary facies are identified:alluvial fan facies,fan delta facies,braided stream facies,braided delta facies,lacustrine facies,of which the sedimentarycharacteristics are studied.The lithologyand paleogeographyin Paleogene Lulehe Formation indicates that there mainlydeveloped twosets of depositional system assemblages.Depositional environment attributes to alluvial fan-fan delta-lacustrine environment system in Erboliang-Lenghu zone of northwestern Qaidam Basin and alluvial fan-braided stream-braided delta-lacustrine environment systemin Mahai-Nanbaxian zone ofsoutheastern QaidamBasin.