Fracture model and structural history of Gunung Keriang, Kedah

Gunung Keriang is a limestone hill in Kedah, northwest Peninsular Malaysia, with well-bedded limestones that gently dip towards the SW and SE, forming N-S trending gentle folds. Fractures are prevalent at both regional and local scales, with three major fracture sets identified: NW-SE, N-S, and NE-SW, all of which are steep to vertically dipping. These fracture sets and their characteristics have been thoroughly analyzed and summarized in this study. The NW-SE fractures have an average length of 137.2 m with a spacing of 92.3 m, the N-S fractures average 120 m in length with 81.3 m spacing, and the NE-SW fractures average 101.6 m in length with 72.7 m spacing. The limestone deposits in Gunung Keriang were formed in a partially unstable shallow marine environment during the Early Permian to Early Triassic period. Subsequently, the Late Triassic collision between the Sibumasu and Indochina terranes led to the formation of N-S trending gentle folds, N-S tension gashes, and potential conjugate fracture sets (NW-SE and NE-SW direction) due to E-W compression. The ensuing uplift exposed the Gunung Keriang limestone and caused extensive dissolution, particularly along fractures.