Sequence stratigraphy and lake basin-filling model on the Altun slope in the Qaidam basin

Four types of isochronous or quasiisochronous boundaries,i.e.tactonic erosion urconformity,condensed surface overlopped by the local tectonic movement,facies transition surface and lake-flooding surface,are developed in the Paleogene and Neogene System on the Altun slope of the Qaidam basin.They may divide the Paleogene and Neogene lake basin-filling system into three tectonic sequences and four genetic sequences,and an isochronous stratigraphic framencrk and three sequence types,i.e.the initial rifting type,extensional rifting type and highstand type are established.Each sequence type is controlled by a specific sedimentary-paleotectonic setting and exhibits its own internal structure,thus forming the lake basin -filling model of continuous eastward migration of the depocenter of the Paleogene and Neogene Qaidam Lake basin and generaly upward-fining lake basin-filling.