History Woyla Arc of the Garba Complex: Implications for Tectonic Evolution of the South Sumatra Region, Indonesia

Abstract

Studies on outcrop-scale structures have been conducted at the Garba complex. This study aims to add the high-resolution of the South Sumatra region to reconstruct the structural geology and implications of tectonics for the region. The study area is commonly referred to as crystalline basement highs forming the southwestern boundary of the Paleogene South Sumatra basin. The structures commonly show the NW-SE, NNW-SSE, and ENE-WSW trends. The methodology used includes field mapping, analysis of Digital Elevation Model (DEM), petrography, and X-ray fluorescence (XRF). The major fractures include wrench slip, reverse, and normal faults, while the observable microstructures comprise pull-apart calcite veins, shear joints, boudins, parasitic folds, and the augens. The earlier structuring episode was probably related to crustal extension, perhaps associated with the Paleogene rifting that occurred along the western margin of Sundaland. In the Late Neogene, tectonic compression took place in the entire region, allowing inversion of the Pre-Tertiary sequence. As compression waned in the Pleistocene, extension commenced, and a number of the ENE-WSW tensional block faulting developed and intersected the older NNW-SSE alignments. It is important to note that the latest tectonic event in conjunction with deep erosional denudation had likely exhumed the terrain and eventually shaped the present-day fractured and rough landforms in the study area.