Thrust in the Semanggol Formation, Kuala Ketil, Kedah


Author : Zaiton Harun, Basir Jasin, Norshida Mohsin & Azrelawati AzamiPublication : Bulletin of the Geological Society of MalaysiaVolume : 55Page : 61-66Year : 2009DOI : https://doi.org/10.7186/bgsm55200910


Description

Bulletin of the Geological Society of Malaysia, Volume 55, November 2009, pp. 61-66

 

Thrust in the Semanggol Formation, Kuala Ketil, Kedah

Zaiton Harun, Basir Jasin, Norshida Mohsin & Azrelawati Azami

Program Geologi, Pusat Pengajian Sains Sekitaran dan Sumber Alam, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

 

Abstract— An excavation of a small hill, Bukit Kukus in the vicinity of Kuala Ketil town exposed the chert unit of the Semanggol Formation which comprises black mudstone, sandstone, tuffaceous sandstone, tuff, paraconglomerate, siliceous shale and chert. The chert contains radiolarians indicating late Early Permian to Middle Triassic of age. These rocks are generally thrusted northward. The thrust and the normal faults occupy the same orientation of fault planes. The dextral faults also occupy the same orientation as the Bok Bak fault which is of sinistral. As the result of transpressional deformation northward thrusts occupy fault planes which were formally the normal faults. The normal faults are the extensional faults resulting from the sinistral movement of the Bok Bak fault. The northward thrust is generated from the dextral movements along the northwest and west-northwestern faults, and is interpreted to be the youngest fault movement onshore. 

Keywords: thrust faults, chert unit, Semanggol Formation, mylonite

 

Abstrak— Tarahan Bukit Kukus berhampiran dengan pekan Kuala Ketil mendedahkan unit rijang Formasi Semanggol yang terdiri daripada batu lumpur hitam, batu pasir, batu pasir bertuf, tuf, parakonglomerat, syal bersilika dan rijang. Rijang mengandungi radiolarian yang berusia akhir Perm Awal hingga Trias Tengah. Batuan tersebut secara umum tersungkup ke utara. Sesar sungkup dan sesar normal mempunyai orientasi yang serupa. Sesar dekstral pula juga menunjukkan orientasi yang serupa dengan sesar Bok Bak iaitu sesar sinistral. Sungkupan ke utara berupa hasil daripada keadaan transpresi yang dialami oleh satah sesar yang sebelumnya ialah sesar normal. Sesar-sesar normal tersebut ialah sesar ekstensi hasil daripada pergerakan sinistral sesar Bok Bak. Sungkupan ke utara terjana oleh pergerakan dekstral sesar-sesar berjurus baratlaut dan barat-baratlaut, dan ini berupa pergerakan yang terakhir dapat dikesan.

https://doi.org/10.7186/bgsm55200910