Abstract: Conforming to the guideline that tectonism controls sedimentation,the study investigated the Early and Middle Cambrian paleogeography and depositional evolution of Tarim Basin based on fine interpretation of 2D seismic profile and analysis of the latest drilling geological data.In the Early Cambrian,the tectonic paleogeography in Tarim Basin was characterized by the "framework with one uplift located between a southern and a northern depressions":a nearly EW-trending synsedimentary palaeohigh occurring in Bachu and eastern Tazhong uplift areas,and transiting to depressions in both the north and southwest directions.During the sedimentary period of the Yurtusi Formation in the Early Cambrian,Tarim Basin was a ramp with the deepwater shelf being dominant,and the tidal flat,slope,deepwater basin facies were successively developed along both the south and north sides of the central palaeohigh.But during the sedimentary period of the Xiaorbulak Formation in the Early Cambrian,Tarim Basin was a carbonate ramp of certain platform characters;the inner,middle and outer ramp facies and basin facies were developed along both the south and north sides of the central palaeohigh;and the outer ramp facies shows typical reflectance signatures of progradation on seismic sections.This study confirmed the existence of the central paleo-continent of the Early Cambrian in Tarim Basin,and preliminarily revealed the distribution of the paleo-continent and the relevant sedimentary facies belts of the Early Cambrian Yurtusi Formation and Xiaorbulak Formation.Through tectonic and sedimentary evolution analysis,we were sure,for the first time,that the Early Cambrian Tarim Basin was a ramp controlled by a north-south differential tectonic pattern instead of a carbonate platform in the real sense of the term.The platform in the western-central Tarim Basin came into being until the Middle Cambrian.

Key words: depositional evolution, palaeogeography, Cambrian, Tarim Basin