The Integrated Analysis of Basement Faults in North Bangka Island, Indonesia, Using Surface Lineament Density and Gravity Anomaly Enhancement

Abstract

Bangka Island was formed by the subduction and collision of the Gondwana-derived Sibumasu and East Malaya blocks in the Late Paleozoic. Its northern region comprises Permian metamorphic rocks of the Pemali Complex, Triassic sedimentary units from the Tanjunggenting Formation, and Late Triassic to Early Jurassic granites of the Klabat Formation. Despite multiple tectonic phases shaping Bangka Island, the structural configuration of basement faults and folds in the northern region remains poorly constrained. This uncertainty hampers the assessment of fractured basement reservoirs in the study area. To address this gap, this study integrates surface lineament extraction from DEMNAS with gravity anomaly data from GGMplus to investigate the basement structure of the northern Bangka. Fast Sigmoid Edge Detection (FSED) and Euler Deconvolution were applied to enhance structural interpretation and estimate basement depth. The dominant structural orientations of NW-SE and NE-SW identified at the surface were consistent with the subsurface features; however, FSED and Euler Deconvolution also revealed E-W and N-S trends. Moreover, the findings from the Euler Deconvolution indicated basement depths of 3000-4000 m below sea level. Field fracture measurements from granitic outcrops validate these orientations, confirming a strong correspondence between surface and subsurface structures. These findings offer new insight into the tectonic evolution of the northern region of Bangka Island and highlight fault orientations that may aid in identifying fractured basement reservoir zones in granitic terrains.