Oligocene to Pleistocene basin development and sequence stratigraphy in northwest Taiwan

• Main Authors: Wei-Yi Chiu, 邱維毅
• Other Authors: Andrew Tien-Shun Lin
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/y728gj

碩士 === 國立中央大學 === 地球物理研究所 === 97 === The tectonic environment in NW Taiwan and its vicinity is a latest Miocene ~ Recent foreland basin developing on top of mid-Oligocene to Miocene passive-margin sequences. This study integrated reflection seismic and well-log data to reveal the stratigraphic development in the study area since the Oligocene by combined analysis on well-log sequences and mapping of sediment thickness. Seismic data show that all the stratigraphic units deepen toward the east due to orogenic loading. Stratigraphic units deposited during Oligocene to Miocene passive-margin stage show no distinct thickness variation in the east-west direction with the exception of the Nanchuang Formation. This formation abruptly terminates against the offshore Kuanyin basement high in the west, interpreted as extensional fault-controlled deposition. Stratigraphic units of the foreland basin thicken toward the Taiwan orogen and thin westward toward the Kuanyin basement high. Seismic mapping show that the depositional strike of the foreland basin changes from NE-direction in the west to NEE-direction in the east and southeast. This indicates that the pre-existing NEE-striking extensional basin center during the deposition of the Nanchuang Formation has facilitated later foreland subsidence. Analysis on wireline log facies identifies 8 types of paleo-environments ranging from offshore to fluvial environments. The vertical change of paleo-environments indicates that there are 9 types of parasequences in the Oligocene-Pleistocene succession. This study recognizes 20 sequences through the study of stacking patterns for individual parasequence and identifications for major stratal surfaces. Our results indicate that the passive-margin succession consists of a few offshore-coastal sedimentary cycles and those cycles roughly correspond to eustatic sea-level changes. By contrast, the foreland basin succession is floored by a deepening-upward succession (i.e. from Kueichulin Formation to Chinshui Shale) followed by an overall shallowing-upward trend (i.e. from Cholan Formation to Toukoshan Formation). The later shallowing-upward trend is apparently controlled by the growth and encroachment of Taiwan orogenic belt east of the study area.