JOHNSON, CARI L., Stanford University, Dept. of Geological and Environmental Sciences, Stanford, CA

ABSTRACT: Age, Style, and Regional Significance of Late Mesozoic Extension, Yinshan Mountains, China: Implications for Petroleum Systems in Northern Ordos Basin

The proposed research will determine whether a sequence of sedimentary and metamorphic rocks exposed in the Yinshan mountains, China, represent an Early Cretaceous extensional regime. In addition to interpretation of these rocks at outcrop and local scales, this project will further elucidate the complex history of intracontinental deformation and associated sedimentary response in the China-Mongolia border region during the late Mesozoic. Finally, this research will address the prospectivity of a late Mesozoic hydrocarbon-bearing rift system in the subsurface of northern Ordos basin.

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Reconnaissance fieldwork indicates that a sequence of siliciclastic sedimentary rocks was deposited in a half graben along the northern margin of Ordos basin during the late Mesozoic. In addition, preliminary study of a series of mylonites and gneisses exposed nearby suggests that these rocks may represent a metamorphic core complex, possibly formed during Early Cretaceous extension. The specific questions that will be answered by this research are: 1) Do the sedimentary and metamorphic rocks record an extensional event (or multiple events)? If so, when did this event occur and what was the overall extensional stress orientation? 2) What is the significance of these rocks considering the geologic history of the Yinshan area in which multiple episodes of thrusting, extension, and strike-slip faulting have been documented throughout the Jura-Cretaceous? 3) How do these outcrops relate to the documented Jura-Cretaceous petroliferous rift systems in central Asia, and what is the potential for an analogous rift system in the Ordos subbasin?

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid