Tectonics, topography, and river system transition in East Tibet: Insights from the sedimentary record in Taiwan
Tectonics, topography, and river system transition in East Tibet: Insights from the sedimentary record in Taiwan
复制标题
DOI：
10.1002/2014gc005310
复制
发表时间：
2014-09
期刊：
影响因子：
3.7
通讯作者：
Qing Lan;Yi Yan;Chi‐Yue Huang;P. Clift;Xuejie Li;Wenhuang Chen;Xingchang Zhang;Mengming Yu
中科院分区：
文献类型：
--
作者：
Qing Lan;Yi Yan;Chi‐Yue Huang;P. Clift;Xuejie Li;Wenhuang Chen;Xingchang Zhang;Mengming Yu
东亚新生代的特点是构造、地貌和河流系统发生重大变化，尽管这些变化的时间和性质仍然存在争议。我们研究了台湾西部山麓破碎不整合面新生代泥岩的地球化学和钕同位素特征，以限制南海开放期间华南地区的侵蚀和排水发展。这些岩石中的 La/Lu、Eu/Eu*、Th/Sc、Th/La、Cr/Th 和 εNd 值在~31 和 25 Ma 之间显示出突变。一般而言，31 Ma 之前沉积物中较高的 εNd 值表明受到华南沿海显生宙花岗岩源的侵蚀，而较低的 εNd 值表明主要源在约 25 Ma 时已演化至中国南方内陆。凝灰岩锆石的 SHRIMP U-Pb 年龄以及生物地层学数据将破裂不整合面限制在~39 Ma 和 33 Ma 之间，表明南海海底扩张在~33 Ma 之前就开始了。这比盆地深处保存的大部分洋壳要古老得多。破碎不整合面的历时西年轻化和盆地物源变化与海底扩张自东向西传播一致。南海在~33 Ma之前的初始扩张对应于东亚的构造调整，包括印度支那地块的挤压和俯冲太平洋板块的旋转和东退。
The Cenozoic in East Asia is marked by major changes in tectonics, landscapes, and river systems, although the timing and nature of such changes remains disputed. We investigate the geochemistry and neodymium isotope character of Cenozoic mudstones spanning the breakup unconformity in the Western Foothills of Taiwan in order to constrain erosion and drainage development in southern China during the opening of the South China Sea. The La/Lu, Eu/Eu*, Th/Sc, Th/La, Cr/Th, and εNd values in these rocks show an abrupt change between ∼31 and 25 Ma. Generally the higher εNd values in sediments deposited prior to 31 Ma indicate erosion from Phanerozoic granitic sources exposed in coastal South China, whereas the lower εNd values suggest that the main sources had evolved to inland southern China by ∼25 Ma. The SHRIMP U‐Pb ages of zircons from a tuff, together with biostratigraphy data constrain the breakup unconformity to be between ∼39 and 33 Ma, suggesting that the seafloor spreading in the South China Sea commenced before ∼33 Ma. This is significantly older than most of the oceanic crust preserved in the deeper part of the basin. Diachronous westward younging of the breakup unconformities and provenance changes of basins are consistent with seafloor spreading propagating from east to west. Initial spreading of the South China Sea prior to ∼33 Ma corresponds to tectonic adjustment in East Asia, including extrusion of the Indochina block and the rotation and eastward retreat of the subducting Pacific Plate.