APPLICATION OF GROUND PENETRATING RADAR IN OUTCROP GEOLOGICAL STUDY——AN EXAMPLE OF THE ORDOVICIAN CARBONATE OUTCROPS IN THE TARIM BASIN

Ground penetrating radar (GPR) is a high-resolution electromagnetic method to inspect the shallow subsurface features.Foreign geologists have used GPR in many fields of outcrop geological studies such as 3D reservoir molding,sedimentary facies analysis,high-resolution sequence stratigraphy,3D fracture imaging,shallow-fault finding,paleokarst study and so on.The Ordovician carbonate outcrops of Bachu Dawuzitage hills in the Tarim Basin are well developed and present abundant geological phenomena including bioherm-beach assemblages,intrusion of igneous rocks,karst features and so on.Ground penetrating radar experimental survey with frequency of 32-500 MHz has been conducted in this area.The results indicated that the penetrating depth can be up to 20 m with the maximum resolution of decimeter.Many geological features,such as reefs,channels in the reef,small-scale faults and karst caves,have typical responses in the high-resolution GPR profiles and can be corresponded well with outcrops.This provides a new associate approach for the outcrop study of carbonate rocks.