Shallow Seismics of Recent Sediments Deposited in the Miaoli-Hsinchu Offshore Area, Taiwan

Abstract

Uniboom seismic data acquired in the Miaoli-Hsinchu offshore area were analyzed in terms of seismic sequence and seismic fades. A gas chimney and an anticlinal structure were discovered in Sequence I of the shallow marine area off Miaoli. This gas chimney is probably the first one ever discovered offshore Taiwan. Transgressive basal sands of Sequence I were then deposited on the unconformity which separates Sequences I & II. Slope front fill facies and slump facies of Sequence III dominate the recent sediments off Tunghsiao and Paishatun. A visible broad deltaic lobe facies was deposited in the Houlung and Chuwei offshore areas. The apex of the lobe does not directly face the estuaries of the Houlung Hsi or the Chungkang Hsi Rivers indicating the deposition of the lobe was a ected by the topography of the sea floor and the longshore currents. Paleostorm sand bars and lagoonal seismic facies are recognized in the Chiting and Hsiangshan offshore areas.
Uniboom seismic stratigraphy proved useful in the research subjects of Quaternary paleoenvironmental evolution, sea level change, shallow structure, gas chimney and the stability of the sea floor in the Taiwan area.

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