Morphology and Geologic Implications of Penghu Channel off southwest Taiwan

Abstract

Penghu Channel shows submarine valley morphology characterized by relatively shallow and wide elongate depression with gently sloping sides and a continuous bottom gradient. The possibility of being a river valley of the Penghu Channel during Late Pleistocene can not be ruled out. But, modern currents completely overprint the signature of inherited paleo-geo­morphology of a river valley. At present, Penghu Channel is considered as a scour furrow of probably erosion origin, mainly by northward tidal currents. It serves as a sediment pathway transporting shelf sediment along­shore and northward on the tide-dominated Taiwan Strait shelf. Penghu channel together with Yunchang Ridge to the north may be considered parts of a modern tidal erosion and deposition system.

Bathymetric data indicate that Penghu Channel may not extend sea­ward into Penghu Canyon. The head and main course of Penghu Canyon are not aligned with Penghu Channel. They are two different undersea features, not a continuous sea valley. The hypothesis of an ancient Minchiang River flowing from China and extending southward to the sea through a sinuous valley on the exposed Taiwan Strait during Late Pleistocene is not supported by evidence of newly generated bathymetric chart and modern hydrodynamics.

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