The sedimentary records of Taiwan foreland basin
Shao-Ping Chiang
Abstract
According to the stratigraphic model of foreland basins, there is a regional unconformity, basal foreland unconformity, which delimits the base of foreland sequence.This unconformity is also found in the Taiwan foreland basin. Taiwan foreland basin was initiatedin late Miocene, and has accumulated a deepening followed by a shallowing-upward sequence of up to ~5 km-thick in central Taiwan. In central Taiwan, the lower deepening upward succession consists of the Kueichulin Formation and the Chinshui Shale; the upper shallowing-upward sequence is comprised of the Chinshui Shale, Cholan Formation and the Toukoshan Formation. The foreland basin deposits of Taiwan may be divided into three scales of stratigraphic sequences: small-scale, intermediate-scale and large-scale stratigraphic packages, in central and southern Taiwan. Small-scale (20 to 150-m thick) stratigraphic sequences, also called parasequences, contain shallowing-upward succession that are bracket by thin coquina sandstones. Intermediate-scale (150 to 1000 m thick) sequences are bounded by unconformities that clearly identified in seismic profiles and outcrops, the Chen et al. (2001) interpreted these sequences as ¡§sequences¡¨ in the classic model of sequence stratigraphy. The large-scale succession consists of the whole deposits of the Pliocene-Pleistocene, showing coarsening- and shallowing-upward (offshore sandstone to fluvial conglomerate) trends. The rates of basin subsidence and sedimentation increase progressively as the foreland basin evolves, indicating the growth of the orogenic loads coupled by an increase in sediment supply.
References
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