Synsedimentary deformation of the Kapas Conglomerate, Pulau Kapas, Terengganu


Author : Mustaffa Kamal ShuibPublication : Bulletin of the Geological Society of MalaysiaVolume : 48Page : 103-109Year : 2004


Description

Bulletin of the Geological Society of Malaysia, Volume 48, June 2004, pp. 103-109

 

Synsedimentary deformation of the Kapas Conglomerate, Pulau Kapas, Terengganu

MUSTAFFA KAMAL SHUIB

Geology Department, University of Malaya, 50603 Kuala Lumpur

 

Abstract: Late Paleozoic continental conglomerates are widely distributed in the Eastern Belt of Peninsular Malaysia. In Terengganu, it primarily occurs in Pulau Kapas as a wedge shaped basin, thought to be formed within a strike slip fault system. A structural and sedimentological study of the Kapas Conglomerate provides insight into its sedimentary tectonic history. The initial tectonic activity in the basin can be traced to movement along two major splaying strike-slip faults, the dextral NS Kapas Fault Zone and a sinistral NNW fault, which enclose the Kapas Conglomerate. When these faults were concurrently active, a region of compression and uplift developed where they converged. Correspondingly, extension and subsidence occurred where they diverged. This setting produced a major source area, which supplied relatively constant detritus to the adjacent fault-wedge basin. In the Late Palaeozoic, a braided alluvial fan developed in the region, as represented by the Kapas Conglomerate. The fan evolved in a semi-arid climate, and flows were generally from the west. The development of the fan is coeval with synsedimentary volcanism. The overall trend of the sedimentary sequence is the result of the strike slip faulting along the active margin of the subsiding basin. Active faulting activities continued during the deposition leading to synsedimentary deformation of the conglomerate. A NS dextral strike slip fault system at the western margin of the Kapas Conglomerate provides clear evidence for this tectonic phase. The influence of this tectonic phase is recorded in the coarsening upward cycles of the sedimentation. Due to ongoing synsedimentary strike slip deformation, the sediments show sets of small-scale conjugate normal faults creating a pattern of horst and graben structures, internally progressive tilting of the strata and an internal angular unconformity. This Late Palaeozoic dextral transpressive deformation, and rapid uplift followed deposition of continental sediment coeval with volcanism, in a tectonically active strike slip basin is a major orogenic event which can be considered as part of a large scale deformation in the Eastern Belt that may have accommodated the oblique convergence of the two tectonic blocks of Peninsular Malaysia.

 

Abstrak: Konglomerat benua banyak terdapat tertabur di jalur Timur Semenanjung Malaysia. Di Terengganu ia terdapat di Pulau Kapas dalam satu lembangan berbentuk baji, yang dipercayai terbentuk akibat sistem sesar gelinciran jurus. Satu kajian struktur dan enapan Konglomerat Kapas dapat menyingkap sejarah tektoniknya. Aktiviti tektonik awal lembangan ini boleh dikaitkan dengan pergerakkan sepanjang dua sesar gelinciran jurus yang besar, iaitu Zon Sesar Kapas (dekstral, U-S) dan satu sesar sinistral yang menjurus B-BL, yang membendung Konglomerat Kapas. Apabila sesar-sesar ini aktif serentak, satu kawasan mampatan dan terangkat terbentuk. Apabila mereka mencapah, berlaku pula keadaan ekstensi dan penurunan. Keadaan ini menghasilkan kawasan sumber yang membekalkan detritus kepada lembangan tersebut. Pada Paleozoik Lewat, satu kipas lanar terbentuk yang diwakili oleh Konglomerat Kapas. Kipas lanar ini terbentuk pada kawasan separa kering dan aliran secara umumnya ke arah barat. Pembentukan kipas ini berlaku semasa dengan aktiviti volkanisma. Corak keseluruhan turutan enapan yang terhasil adalah hasil sesaran gelinciran jurus sepanjang tepian aktif lembangan yang sedang menurun itu. Aktiviti sesaran berlanjutan semasa dengan pengenapan menyebabkan canggaan syn-sedimen konglomerat tersebut. Kehadiran satu sistem sesar gelinciran jurus dekstral pada sempadan barat Koglomerat Kapas adalah bukti untuk fasa tektonik ini. Pengaruh fasa tektonik ini direkodkan dalam bentuk kitaran enapan yang bercorak mengasar keatas. Disebabkan oleh aktiviti canggaan gelinciran jurus syn-sedimen yang berterusan, enapan ini menunjukkan beberapa set sesar normal konjugat, penyegetan progresif strata dan satu ketakselarasan dalam. Canggaan transpresi dekstral ini diikuti dengan pengenapan enapan benua semasa dengan volkanisma, dalam suatu lembangan gelinciran jurus boleh dikaitkan dengan canggaan rantau di jalur Timur yang terhasil akibat penumpuan serong kedua-dua bungkah tektonik Semenanjung Malaysia.

https://doi.org/10.7186/bgsm48200420