| dc.description.abstract | Sumatra, the world’s sixth-largest island, is located in the western part of Indonesia. It extends across the equator for 1760 km with an NW-SE orientation. The Central Sumatra Basin is one of the 3 back-arc basins on the northeastern side of the island. The subsurface temperature distribution of the Central Sumatra Basin is estimated with the primary objective to get a better understanding of the thermal characterization and the presence of a high-temperature anomaly in the area. Two research steps were taken to answer these questions, including the 3D geological modeling and temperature modeling. The first step involves the 3D geological modeling of the area. The modeling is based on the geological information from 185 exploration wells and uses the geospatial interpolation method. The results are presented as five top structure maps for each sedimentary unit, including the Minas, Petani, Telisa, Sihapas, and Pematang Group, and one map for the basement. The second step involves the 3D temperature modeling using a thermal-tectonic forward modeling method, constraining the subsurface temperature measurements in the Central Sumatra Basin. The temperature measurements consist of 122 temperature data in total, including 118 uncorrected BHTs and 4 DSTs. The AAPG statistical method was used for the correction of the BHT and resulted in a set of 118 corrected BHTs with better reliability. From this whole dataset, the average thermal gradient is 52.2⁰C/km, with a surface temperature of 29⁰C. From the 3D temperature models, the best thermal model corresponds to the lithospheric thickness of 90 km and an old (>500 Ma) upper crust of granitic composition, with relatively high radiogenic heat production. Both the relatively thin lithosphere and the enhanced heat production contributes to the high-temperature anomaly in the area. The increased upper crust heat production might have been caused by the partial melting and crustal reworking due to major tectonic events such as block separation from the East Gondwana, crustal accretion of the Sibumasu and Cathaysia block, and Sumatran orogenesis within the extended time range of Pre-Devonian to Early Tertiary. The pattern distribution of temperature anomalies in the area is also affected by the basin structure of the Central Sumatra Basin. | |
