Karakteristik dan Mekanisme Keterbentukan Batuan Pra-Tersier Daerah Simpang, Kabupaten Ogan Komering Ulu Selatan, Sumatera Selatan

Abstrak

The Simpang area, located in South Ogan Komering Ulu Regency, lies within the Pre-Tertiary region of Sumatra, recording a complex tectonic and magmatic history from the Paleozoic to Mesozoic. The region hosts metamorphic, sedimentary, volcanic, and granitoid rocks, reflecting the influence of subduction, collision, and accretion processes. In particular, the exposed Pre-Tertiary rocks result from the collision between the Woyla Arc and the West Sumatra Block, offering insight into their formation mechanisms and characteristics. Previous studies have outlined the Woyla Arc’s geological structure within the Garba Complex; this study aims to reconstruct the sequence of formation processes and define the properties of Pre-Tertiary rocks through detailed geological mapping and petrographic analysis. Our research indicates that the evolution of these rocks was controlled by multistage convergent tectonics from the Carboniferous–Permian to the Late Cretaceous. The early phase involved Paleotethys subduction, causing regional metamorphism and forming the Tarap Formation (PCt) basement. Subsequent Mesotethys subduction and accretion produced schists and island-arc andesites in the Garba Formation’s Situlanglalang (Kjgs) and Insu (Kjgv) members. Intense deformation within an accretionary prism generated the Mélange Complex (Km), followed by arc magmatism that intruded the Garba Granite (Kgr). These findings illustrate how subduction, accretion, deformation, and magmatism interacted dynamically to produce a complex, continuous regional geological framework in the Simpang area.

Kata kunci

• Karakteristik
• Sejarah
• evolusi
• petrografi
• simpang
• tektonik