On the presence of pre-Carboniferous metasediments in the Eastern Belt: A structural view


Author : Ibrahim AbdullahPublication : Bulletin of the Geological Society of MalaysiaVolume : 49Page : 79-84Year : 2004


Description

Bulletin of the Geological Society of Malaysia, Volume 49, April 2004, pp. 79 - 84

 

On the presence of pre-Carboniferous metasediments in the Eastern Belt: A structural view

IBRAHIM ABDULLAH

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

 

Abstract: The geological map of Peninsular Malaysia shows that the oldest rocks formation in the Eastern Belt is Carboniferous in age and consist of mainly clastic sedimentary rocks. The rocks had been subjected to low grade regional metamorphism to become metaquartzite and phyllite and generally known as metasediments. The metasediments are unconformably overlain by the Jurassic-Cretaceous continental deposits. Recent finds of plant fossils from the continental deposits in the Bukit Keluang area, Terengganu indicate a Late Permian age. The area was intruded by the Permo-Carboniferous mafic to intermediate igneous rocks, followed by the Late Permian-Early Triassic biotite granite and the Late Triassic granite and finally by the Jurassic-Cretaceous dolerite dykes. Most of the interpreted Carboniferous metasediments show at least two episodes of folding trending towards north-northwest (NNW) or south-southeast (SSE) and north-south (N-S) directions. However, in certain areas, these rocks indicate more complex structures with three generations of folding with the earliest trending east-northeast (ENE), followed by NNW trending folds. From structural point of view, it is suggested that the more complicated metasediments with three generations of folds are of older (pre-Carboniferous) age. The earliest ENE trending folds were probably developed during the mid- Devonian orogeny that was interpreted based on the structural studies in other areas within Peninsular Malaysia.

 

Abstrak: Peta geologi Semenanjung Malaysia menunjukkan formasi batuan yang tertua yang terdapat di Jalur Timur adalah berusia Karbon terdiri terutamanya daripada batuan sediment klastik. Batuan ini telah mengalami metamorfisme rantau bergred rendah menjadi metakuarzit dan filit dan umumnya dipanggil metasedimen. Metasedimen ini ditindih secara tidak selaras oleh endapan daratan berusia Jura-Kapur. Penemuan terbaru fosil tumbuhan dalam endapan daratan di kawasan Bukit Keluang, Terengganu menunjukkan usia Perm Lewat. Kawasan ini telah direjahi oleh igneus mafik hingga pertengahan berusia Karbon-Lewat, diikuti oleh granit biotit Permian-Lewat-Trias Awal, granit Trias Lewat dan akhirnya oleh daik dolerit Jura-Kapur. Kebanyakan batuan yang ditafsirkan berusia Karbon menunjukkan telah mengalami dua episod perlipatan mengarah ke utara-baratlaut (UBL) atau selatan-tenggara (STG) dan utara-selatan (U-S). Walau bagaimanapun, di kawasan tertentu, batuan ini menunjukkan struktur yang lebih rencam dengan tiga generasi perlipatan, yang paling awal mengarah ke timur-timurlaut (TTL) diikuti oleh lipatan berarah BL atau (TG) dan UBL atau STG. Daripada sudut struktur, dicadangkan bahawa metasedimen yang lebih rencam dengan tiga generasi perlipatan adalah berusia lebih tua (pra-Karbon). Pembentukan lipatan berarah TTL mungkin boleh dikaitkan dengan orogeni Devon-Tengah yang ditafsirkan berdasarkan kajian struktur di kawasan-kawasan lain di Semenanjung Malaysia.