ABSTRACT: Seismic Stratigraphy and Tectonic Evolution of Tungyintao Basin, Offshore Northern Taiwan
Lee Tung-Yi, Tang Chen-Hui
The Tungyintao basin, offshore northern Taiwan, is part of the East China Sea rift system. The basin is a half-graben, filled with lower Tertiary sediments derived principally from the Chinese mainland. This research used 1840 km of industrial seismic reflection sections and two exploration wells to investigate an area of about 10,000 km2.
Three syn-rift and two post-rift sequences are separated by an angular breakup unconformity. The early Paleocene initial rift phase was characterized by deposition of fan-delta systems in shallow structural lakes. During late Paleocene, with gradually rising base-level and subsidence, deep-water sedimentary facies were deposited. At the very end of the Paleocene, thin limestone was deposited on the ridges surrounding the basin, marking the first marine influence of this area. The final stage of the syn-rift basin was marked by deposition of Eocene and early Oligocene(?) delta systems. After the early Oligocene breakup, the basin became stabilized, with only gentle tilting toward the southeast. The principal depocenters shifted far to the east, where Miocene fluvial and delta systems w re deposited in the Okinawa Trough. During late Miocene to Quaternary, fluvial systems originating in East China continued to transport sediment to the Okinawa Trough.
This study also concludes that infill deposition was associated with listric normal faulting during the initial rift phase, and that syn-tectonic deposition was accompanied by planar normal faulting during the major rift phase. The rift basin is asymmetric not only in the transverse direction but also in the longitudinal cross section. An oceanic lithosphere, associated with the spreading of South China Sea, that extended from the East China Sea to the South China Sea, was consumed along the Malina Trench from late Oligocene to early Pliocene.
Inferred reservoir and source-rock conditions in Tungyintao basin indicate very favorable hydrocarbon potential.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990