Cenozoic Rotation History of Borneo and Sundaland, SE Asia Revealed by Paleomagnetism, Seismic Tomography, and Kinematic Reconstruction

Abstract

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.

Burma Terrane part of the Trans-Tethyan arc during collision with India according to palaeomagnetic data

“…From this template, we modified the tectonic history of the BT to reflect our paleomagnetic results. Furthermore, the positions and paleogeography of Greater India, Indochina, Kohistan, Lhasa, Sumatra and Woyla were configured to better reflect more recent studies 8,67,68 . In Figure 1b, the global reconstruction with the Greater India basin hypothesis is based on a different set of poles of rotations 5 .…”

Cretaceous–Palaeogene sedimentary evolution of the South China Sea region: A preliminary synthesis

“…The extrusion model generally assumes that the Palawan Continental Terrane and Borneo were attached to Indochina as a single block that was extruded to the southeast with clockwise rotation due to the India‐Eurasia collision (Figure a; Briais et al, ; Leloup et al, ; Tapponnier et al, ). However, most of the geological observations do not support this model: (a) The direction and magnitude of strike‐slip displacement along the line of the Red River Fault Zone‐East Vietnam Boundary Fault are not consistent and fail to explain such large‐scale lithospheric extension and oceanic spreading in the western South China Sea region (Clift et al, ; Fyhn et al, ; Morley, ); (b) the newly acquired palaeomagnetic data from Borneo suggested a counterclockwise rotation during the Cenozoic, although the timing and magnitude of rotation are still debated (Advokaat et al, ; Fuller et al, ; Schmidtke, Fuller, & Haston, ); (c) while the collision between India and Eurasia occurred as early as in the Early Cenozoic, it was not until the Oligocene that the significant sinistral motion along the Red River Fault Zone‐East Vietnam Boundary Fault initiated, clearly too late to explain the widespread rifting extension of the region during the Late Palaeocene–Eocene.…”

Growth of triangle zone fold-thrusts within the NW Borneo deep-water fold belt, offshore Sabah, southern South China Sea

“…It is generally agreed that proto-South China Sea subduction and South China Sea seafloor spreading were significant regional tectonic events (e.g., Hall, 2002;Cullen, 2010;Zahirovic et al, 2014;Wu and Suppe, 2018). Borneo rotated up to ~45° counterclockwise after the late Eocene (Advokaat et al, 2018). From the early Cenozoic to the mid-Miocene, NW Borneo was apparently an active margin due to southward proto-South China Sea subduction under Borneo ( Fig.…”

“…Three-dimensional (3-D) seismic survey location is shown by the bold black box. Deep-water fold belt anticlines were interpreted from time structure maps in Grant (2004) and Gee et al (2007) reconstructions of NW Borneo and the surrounding region are highly debated (e.g., Hall, 2002;Cullen, 2010;Zahirovic et al, 2014;Advokaat et al, 2018;Wu and Suppe, 2018). It is generally agreed that proto-South China Sea subduction and South China Sea seafloor spreading were significant regional tectonic events (e.g., Hall, 2002;Cullen, 2010;Zahirovic et al, 2014;Wu and Suppe, 2018).…”