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Bradley D. Ritts1
(1) Utah State University, Logan, UT

Abstract: Mesozoic tectonic evolution of the Altun Shan, NW China: implications for petroleum prospects in the SE Tarim Basin

During the Mesozoic, accretionary tectonics in Tibet influenced intracontinental orogenesis and basin formation throughout NW China. It is important to understand how this activity influenced the structural geology and paleogeography of the Altun Shan and adjacent regions in order to evaluate the petroleum potential of SE Tarim; particularly in light of documented Mesozoic petroleum systems across the Altun Shan in the northern Qaidam basin. Paleocurrent, facies, and provenance data indicate that the Altun Shan was not a significant mountain range through the Jurassic and Cretaceous. Furthermore, comparison of Mesozoic facies and geohistory in NW Qaidam and SE Tarim suggest that the NW Qaidam-SE Tarim region acted as a single foreland-style basin, spanning the present Altun Shan, and was primarily controlled by contractional loading in the Kunlun Shan. Thermochronologic and stratigraphic data suggest that this foreland-style basin was partially segmented by basement-involved foreland uplifts. However, the extent of segmentation cannot be evaluated without good subsurface control. During the Cenozoic, the Mesozoic basin was offset by approximately 400 km of strike-slip on the left-lateral Altyn Tagh fault system. These observations and the resultant basin model suggest that exploration prospects in the Mesozoic of SE Tarim are limited relative to the once-contiguous northern Qaidam basin, due to less favorable source rock deposition and burial during the Mesozoic, and subsequent Cenozoic dislocation of SE Tarim from potential source kitchens in northern Qaidam.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana