--> Abstract: Determining Amounts of Basin Inversion, by T. Song; #90937 (1998).

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Abstract: Determining Amounts of Basin Inversion

SONG, TINGGUANG, TSRC, Curtin University

Summary

The inversion ratio of a fault is defined as the value of reverse displacement resulting from compression during basin inversion divided by the normal displacement caused by initial extension within the basin, both measured along the fault plane. The amount of displacement is best measured either within basement or at the basement-cover interface, as basement is unlikely to accommodate significant flexural displacement during deformation. A fault inversion ratio of 1 implies that the basin has undergone total inversion. Values greater than 1 require the amount of shortening within the basin to be greater than the amount of extension. However such a value does not require a large absolute amount of shortening if the initial amount of extension was small. Alternatively a small reverse displacement along a fault plane during inversion may produce a total inversion of the basin in cases where the normal separation prior to inversion is also small. In contrast, a large amount of shortening by inversion may result in only moderate or even mild inversion where initial normal displacement was large. Moreover the horizontal inversion ratio, which represents the cumulative amount of inversion across a number of faults within the basin, can provide important information on overall degree of inversion within a basin. Application of this technique to the Late Jurassic to Cretaceous Songliao Basin of northeastern China, the main petroleum basin in China, reveal a close association between degree of inversion and petroleum accumulation. Basin inversion occurred in the late Cretaceous and increases in intensity from mild inversion in the west to total inversion in the east. The central parts of the basin show moderate and mild degrees of inversion and correspond with the main sites for petroleum accumulation.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah