A foraminiferal study on Middle Eocene-Oligocene break-up nconformity in northern Taiwan and its correlation with IODP Site U1435 to constrain the onset event of South China Sea opening
A foraminiferal study on Middle Eocene-Oligocene break-up nconformity in northern Taiwan and its correlation with IODP Site U1435 to constrain the onset event of South China Sea opening
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台湾北部中始新世-渐新世破碎不整合面有孔虫研究及其与IODP站点U1435的相关性以制约南海开口的爆发事件
DOI：
10.1016/j.jseaes.2016.09.014
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发表时间：
2017
影响因子：
3
通讯作者：
Qianyu Li
中科院分区：
文献类型：
--
作者：
Chi-Yue Huang;Kai-Hsuan Shea;Qianyu Li
台湾位于东南亚大陆边缘，下新生代地层发育。其地质构造背景为研究南海裂陷不整合的时间约束提供了独特的机会。摘要对台湾北部hs<s:1>山山脉上、下乌来群界线上的4个陆地剖面和深部岩心进行了详细的有孔虫学研究。结果表明，下乌来群沉积环境和岩性发生了显著变化，从中始新统河流优势砂岩（>2000 m）到上乌来群渐新统内浅海泥页岩和粉砂岩（>2000 m）。综合沉积学和有孔虫学资料进一步表明，在山北缘上乌莱群坎口组与下乌莱群色冷砂岩的交界处，存在32~33 ~ 40 Ma的沉积间断。台湾山带的这种地层断陷标志着南海东北部中始新统同裂谷地层与上覆渐新统后裂谷层序之间的区域性破碎不整合。该破碎不整合与珠江口盆地地震剖面和南海北部陆架坡U1435勘探点（349考察队）钻探中常见的不整合相关联。断裂不整合的时间上限为32 Ma，标志着早渐新世（~33 Ma）古近系亚洲大陆边缘由裂谷向坳陷的构造转变，最终导致南海深部的打开。
Taiwan is situated in the SE Asian continental margin where lower Cenozoic strata are well exposed. Its geological and tectonic setting provides a unique opportunity to study the time constraint of the break-up unconformity relevant to the opening of the South China Sea. A detailed foraminiferal study on four land sections and a deep core across the boundary between the Upper and Lower Wulai Groups in the Hsüehshan Range, northern Taiwan, was conducted. Results show remarkable changes of depositional environment and lithology from the amalgamated fluvial dominant sandstones (>2000 m) of Middle Eocene in the Lower Wulai Group to the overlying inner neritic shales and siltstones (>2000 m) of Oligocene in the Upper Wulai Group. Integrated sedimentological and foraminiferal data further suggest an occurrence of a depositional hiatus between 32~33 and 40 Ma across the boundary between the Kankou Formation of the Upper Wulai Group and the Szeleng Sandstone of the Lower Wulai Group in the northern Hsüehshan Range, as same as the scenario seen in the Western Foothills (25-39 Ma) of central Taiwan and the Penghu Basin (25-40 Ma) in the Taiwan Strait..This stratigraphic hiatus in the Taiwan mountain belt marks a regional break-up unconformity between the Middle Eocene syn-rift strata and the overlying Oligocene post-rift sequences in the NE South China Sea. The break-up unconformity can be correlated with those commonly recognizedin the seismic profiles of the Pearl River Mouth Basin and drilling of the IODP site U1435 (Expedition 349) in the northern shelf-slope of the South China Sea. The upper time limit of the breakup unconformity 32 Ma could mark the tectonic change from rifting to depression in the Paleogene Asian continental margin which eventually led to opening of the deep South China Sea in the Early Oligocene (~33 Ma)..