Fractures of Gunung Ledang Granite: Insight to Post-Cretaceous Structural Event

Abstract

Based on the deformations in the Cretaceous rocks and also the results of the radiometric dating of the fault zones [Zaiton Harun, Late Mesozoic—Early Tertiary faults of Peninsular Malaysia, 9], it is proven that tectonics of onshore Peninsular Malaysia was still active during post-Cretaceous. These deformations may contribute to the basin formation/inversion during Tertiary period in Sundaland. The study area is Cretaceous granite, Gunung Ledang, which is situated in North Johor. The objective of this study is to determine the major fracture sets at regional scales and outcrop scales and reconstruct the structural events. In this study, the focus is on the negative lineaments of Gunung Ledang at a regional scale and the fractures of the Puteri Waterfall at outcrop scale. During site visit, the details of the fracture, e.g., infilling and sense of motions, are recorded. From the observations and analysis, there are 3 negative lineament sets at regional scale: N-S, NE-SW, and ESE-WNW; four fractures sets found at the outcrop scale: N-S, NE-SW, E-W, and NW-SE. The outcrop-scale fractures are all steeply dipping to almost vertically dipping. The crosscutting relationships show that the chronology of the fractures is N-S, NE-SW/E-W, and NW-SE, from oldest to youngest. NE-SW fracture displaces a N-S mega-crystal quartz dyke in left-lateral motion, which deduces a ~ N-S compression. Another possible Riedel system (right-lateral strike-slip) formed on the same NE-SW fractures, which deduce a ~ E-W compression. The chronology of these two events is hard to define because of lack of clear field evidences.