STRATIGRAPHIC DIVISION,CORRELATION AND DISTRIBUTION OF THE CARBONIFEROUS SYSTEM IN THE JUNGGAR BASIN

Integrating outcrop,drill core,zircon SHRIMP U-Pb geochronometric,seismic,gravimetric, and magnetic data,we establish a stratigraphic framework for the Carboniferous System in the Kalamaili area.This stratigraphic framework allows stratigraphic correlation and spatial characterization of the Carboniferous System in the Junggar Basin.The Lower Carboniferous of the Junggar Basin can be generally divided into three units,corresponding to the early Tournaisian,late Tournaisian,and Visean-Serpuchov stages,respectively.The Upper Carboniferous can be divided into Batamayineishan and Shiqiantan formations.Drill core data of the Upper Carboniferous are far more abundant than the Lower Carboniferous in this region.Seismic reflection features of the Upper Carboniferous are thus more easily recognizable than the Lower Carboniferous.At present,oil and gas exploration in the Junggar basin mainly focuses on the Upper Carboniferous.Seismic reflections of the Lower Carboniferous are not easily recognizable.Upper Carboniferous strata are widely distributed in the margin of the Junggar Basin and thin toward the center. Thickness centers exist in Karamay,Shawan,and Dajing areas.The distribution of the Upper Carboniferous inside the basin was controlled by uplifts and depressions.