Variation in Cenozoic tectonic subsidence in Luconia-Balingian provinces, Sarawak Basin, Malaysia: influence of extensional and compressional tectonics

The Luconia-Balingan Provinces are sedimentary basins in Sarawak, Malaysia that presently extends from offshore to onshore, along major NW-SE faults on both sides of the basins. It was formed by several rifting episodes of the Southern China Block, followed by spreading since Eocene. The rifting coeval with the closure of an ancient oceanic crust that induced compression and major uplift in the southern part of the basins. The basins are filled by up to more than 10 km of Cenozoic sediments overlying the Cathaysian derived crystalline basement. Since the Upper Eocene-Oligocene to Upper Miocene, warm-water to tropical carbonate sedimentation has been dominating the stratigraphy mainly in Luconia. To understand the sediment and tectonic subsidence evolution of the Luconia-Balingian Provinces this study analysed data from exploration wells using a Matlab-based open-source tool, the BasinVis 2.0. Updated compaction trend from three different wells to represent the southern-central-north regions of the provinces are adopted. The subsidence history for Luconia-Balingian provinces can be divided into five stages; (i) 37 to 23 Ma: Steadily increase in subsidence is recorded with higher tectonic subsidence rate in the central and west of Luconia-Balingian and moderate tectonic subsidence in the north and south. (ii) 23-18 Ma: Increase in tectonic subsidence for most parts of Luconia-Balingian with slight decrease in total tectonic subsidence recorded in some of the wells. (iii) 18 to 15.5 Ma: Delayed subsidence within the central and northern parts of Luconia-Balingian, coincide with the diachronous timing of Middle Miocene Unconformity. There was minor uplift in the northern section. However, the southern part experienced increased in the total and tectonic subsidence rates. (iv) 15.5 to 11.8 Ma: Overall decrease in tectonic subsidence rate, coinciding with the prolific growth of Middle to Upper Miocene carbonate build-ups. (v) 11.8 to 0 Ma: Increase in tectonic subsidence rate particularly in the wells within the southern part of Luconia-Balingian. Stretching factors ranges between 1.3 to 1.95 are recorded, indicative for foreland basin setting with a very strong influence from the syn- and post-rift phases. It directly related to the effect of extensional tectonics during the South China Sea opening and compressional tectonics during the closure of the proto-South China Sea during the Cretaceous-Eocene, until Middle Miocene. Through this study, accurate subsidence rates are deduced and allows specific characterization of tectonic influences in different parts of Luconia-Balingian at different stages of basin development.