Advokaat Eldert L, Marshall Nathan T, Li Shihu, Spakman Wim, Krijgsman Wout, van Hinsbergen Douwe J J
Department of Earth Sciences Utrecht University Utrecht Netherlands.
State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China.
Tectonics. 2018 Aug;37(8):2486-2512. doi: 10.1029/2018TC005010. Epub 2018 Aug 12.
SE Asia comprises a heterogeneous assemblage of fragments derived from Cathaysia (Eurasia) in the north and Gondwana in the south, separated by suture zones representing closed former ocean basins. The western part of the region comprises Sundaland, which was formed by Late Permian-Triassic amalgamation of continental and arc fragments now found in Indochina, the Thai Penisula, Peninsular Malaysia, and Sumatra. On Borneo, the Kuching Zone formed the eastern margin of Sundaland since the Triassic. To the SE of the Kuching Zone, the Gondwana-derived continental fragments of SW Borneo and East Kalimantan accreted in the Cretaceous. South China-derived fragments accreted to north of the Kuching Zone in the Miocene. Deciphering this complex geodynamic history of SE Asia requires restoration of its deformation history, but quantitative constraints are often sparse. Paleomagnetism may provide such constraints. Previous paleomagnetic studies demonstrated that Sundaland and fragments in Borneo underwent vertical axis rotations since the Cretaceous. We provide new paleomagnetic data from Eocene-Miocene sedimentary rocks in the Kutai Basin, east Borneo, and critically reevaluate the published database, omitting sites that do not pass widely used, up-to-date reliability criteria. We use the resulting database to develop an updated kinematic restoration. We test the regional or local nature of paleomagnetic rotations against fits between the restored orientation of the Sunda Trench and seismic tomography images of the associated slabs. Paleomagnetic data and mantle tomography of the Sunda slab indicate that Sundaland did not experience significant vertical axis rotations since the Late Jurassic. Paleomagnetic data show that Borneo underwent a ~35° counterclockwise rotation constrained to the Late Eocene and an additional ~10° counterclockwise rotation since the Early Miocene. How this rotation was accommodated relative to Sundaland is enigmatic but likely involved distributed extension in the West Java Sea between Borneo and Sumatra. This Late Eocene-Early Oligocene rotation is contemporaneous with and may have been driven by a marked change in motion of Australia relative to Eurasia, from eastward to northward, which also has led to the initiation of subduction along the eastern Sunda trench and the proto-South China Sea to the south and north of Borneo, respectively.
东南亚由北部源自华夏地块（欧亚大陆）和南部源自冈瓦纳大陆的不同碎块组合而成，这些碎块被代表已闭合古海洋盆地的缝合带分隔开来。该地区西部包括巽他大陆，它是由现今在印度支那、泰国半岛、马来半岛和苏门答腊发现的大陆和弧状碎块在二叠纪晚期至三叠纪合并而成。在婆罗洲，自三叠纪以来，古晋带构成了巽他大陆的东缘。在古晋带的东南部，婆罗洲西南部和东加里曼丹源自冈瓦纳大陆的大陆碎块在白垩纪发生增生。源自华南的碎块在中新世增生到古晋带以北。解读东南亚这一复杂的地球动力学历史需要恢复其变形历史，但定量约束往往很少。古地磁学可能提供这样的约束。以往的古地磁研究表明，自白垩纪以来，巽他大陆和婆罗洲的碎块经历了垂直轴旋转。我们提供了来自东婆罗洲库泰盆地始新世 - 中新世沉积岩的新古地磁数据，并严格重新评估已发表的数据库，剔除未通过广泛使用的最新可靠性标准的地点。我们利用所得数据库进行更新的运动学恢复。我们根据巽他海沟恢复方向与相关板块地震层析成像图像之间的拟合情况，检验古地磁旋转的区域或局部性质。巽他板块的古地磁数据和地幔层析成像表明，自晚侏罗世以来，巽他大陆没有经历显著的垂直轴旋转。古地磁数据显示，婆罗洲经历了约35°的逆时针旋转，该旋转局限于始新世晚期，自中新世早期以来又额外逆时针旋转了约10°。这种旋转相对于巽他大陆是如何实现的尚不清楚，但可能涉及婆罗洲和苏门答腊之间爪哇海的分布式伸展。这种始新世晚期 - 渐新世早期的旋转与澳大利亚相对于欧亚大陆运动的显著变化同时发生，且可能是由该变化驱动的，澳大利亚的运动从向东变为向北，这也分别导致了沿巽他海沟东部以及婆罗洲南部和北部原南海俯冲作用的开始。
