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Kenn-Ming Yang1, Jong-Chang Wu1, Wen-Rong Chi1
(1) Chinese Petroleum Corporation, Miaoli, Taiwan

Abstract: The tectonic implication of stratigraphy architecture in the foreland basin, western Taiwan

The foreland basin in the western Taiwan, which is bordered by a westward moving fold-and-thrust belt to its east, has been developing on a previously uplifted margin of an extensional basin, of which the width and extension increase toward the east. Rapid subsidence following the uplifting indicates the onset of development of the foreland basin. The characteristics of stratigraphy architecture are: 1) westward onlapping of the sequences in the distal part of the basin, associated with initial rapid subsidence stepwise younging toward the craton, 2) unconformities that punctuate the onlapping of the sequences and also are younging to the west, 3) several later phases of rapid subsidence recognized across the entire area and immediately succeeding the unconformities to the west, and 4) submarine truncation followed by deposition of coarsening-upward sequences during each phase of the rapid subsidence. The stratigraphic features cannot be explained by eustatic sea-level fluctuation but rather should be related to eastward migration of forebulge during episodic westward movement of the fold-and-thrust belt and lateral progradation of deposition toward the craton.

Migration rate of the distal part of the foreland basin was slower in the early stage but higher in the final stage than that derived from the previously proposed kinematic model for the steady migration of the orogenic belt. This implies that the pre-collision extensional tectonics might have caused weaker lithosphere beneath the foreland basin and that once the foreland basin migrated onto the less stretched lithosphere the basin would expand rapidly into the craton.

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