Jil. 21, No.3 (Vol. 21, No.3) May-Jun 1995 KANDUNGAN (Contents) K.R. Chakraborty and I. Metcalfe: Stmctural evidence for a probable Paleozoic unconfonnity at 141 Kg. Kuala Abang, Terengganu Basil' J asin and Taj Madira Taj Ahmad: Some Paleogene planktonic foraminifera from the Lubok 147 Antu Coml?lex, Sarawak Special Communication Nik Ramlan b. Nik Hassan: Geotechnical engineering investigations of the Highland Tower 153 Condominium collapse, Vlu Kelang, Selangor A.G. Gunn: Geochemical exploration for gold mineralisation in Malaysia 163 K . Fletcher: Exploration geochemistry in SE Asia: soils, sediments and potential for anthropogenic effects 165 Nik Ramlan b. Nik Hassan: Geotechnical engineering investigations of the Highland Tower 165 Condominium collapse, Vlu Kelang, Selangor Sian Evans: When is a bivalve not a bivalve?: Tube linings and accessory plates in boring lineages 166 Chow Weng Sum: On-the-job training at the Geotechnical Engineering Office, Hong Kong 169 Annual Geological Conference 1995 - Laporan (RepOlt) 171 Welcoming Speech by Dr. Khalid Ngah, President GSM 172 Ucapan Pembukaan Rasmi - YAB Ketua Menteri Melaka Dato' Mohd Zin Hj. Abdul Ghani 178 Programme 180 Abstracts of Papers 183 Keahlian (Membership) 218 Pertukaran Alamat (Change of Address) 218 Pertambahan Bam Perpustakaan (New Library Additions) 219 Local News 220 Kongres Sa ins dan Teknologi Malaysia 'fJ5 224 The 4th ASEAN Science and Technology Week 225 Strategic Management of Hazardous Waste in Malaysia 226 New Dates for Offshore South East Asia96 227 Underground Operators' Conference 227 5th Base Metals Concentrates Conference 228 New Generation Gold Mines: Case Histories of Discovery 229 The 19095 AAPG International Conference and Exhibition 230 AAPG Hedberg Research Conference - Lacustrine Basin Exploration in China, SE Asia & Indonesia 231 Australian Mineral Foundation - Career Path Development: Courses for Profession Staff 232 Kalendar (Calendar) 233 Majlis (Council) 1995/96 Presiden (President) KhalidNgah Naib Presiden (Vice-President) Ibrahim Komoo Setiausaha (Secretary) Ahmad Tajuddin Ibrahim Penolong Setiausaha (Asst. Secretary) Nik Ramli Nik Hassan Bendahari (Treasurer) LeeChai Peng Pengarang (Editor) TehGuanHoe Presiden Yang Dahulu (Immediate Past President) : Fateh Chand 1995-97 1995-96 Khoo Kay Khean Abd. Ghani Mohd Rafek Hoh Swee Chee Abdul Rahim Samsudin Ibrahim Abdullah Effendy Cheng Abdullah Mohd Shafeea Leman Tan Boon Kong Jawatankuasa Kecil Pengarang (Editorial Subcommittee) Teh Guan Hoe (PengerusilChairman) Fan Ah Kwai Ng Tham Fatt J.J. Pereira Lembaga Penasihat Pengarang (Editorial Advisory Board) AwPeckChin FooWahYang Mazlan Madon P.H. Stauffer Azhar Hj. Hussin C.A. Foss Ian Metcalfe Tan Boon Kong K.R. Chakraborty N.S. Haile S. Paramananthan Tan Teong Hing Choo Mun Keong C.S. Hutchison John Kuna Raj Teoh Lay Hock Chu Leng Heng Lee Chai Peng Senathi Rajah H.D. Tjia Denis N.K. Tan Leong Lap Sau Shu Yeoh Khoon Yeap Cheng Hock The Society was founded in 1967 with the aim of promoting the advancement of earth sciences particularly in Malaysia and the Southeast Asian region. The Society has a membership of about 600 earth scientists interested in Malaysia and other Southeast Asian regions. The membership is worldwide in distribution. Published by the Geological Society of Malaysia. Department of Geology. University of Malaya. 59100 Kuala Lumpur. Tel: 003-757 7036 Fax: 003-756 3900 Printed by Art Printing Works Sdn. Bhd.. 29 Jolon Riong. 59100 Kuala Lumpur. Structural evidence for a probable Paleozoic unconformity at Kg. Kuala Abang, Terengganu KR. CHAKRABORTY! AND 1. METCALFE2 IDepartment of Geology University of Malaya 59100 Kuala Lumpur 2Department of Geology and Geophysics The University of New England Armidale, NSW 2351, Australia Abstract: Variably deformed metasedimentary rocks (interbedded metaquartzite, phyllite, slate, etc.) of Paleozoic age exposed at Kg. Kuala Abang, Terengganu, are separable into two units on the basis of discernible differences in structural features. The lower unit exhibits two phases of folding; the earlier southeasterly plunging reclined fold (Fl) is refolded by a later southerly plunging upright fold (F2). The divergent axial trends indicate that the two phases offolding are not coaxial. The upper unit appears to have experienced only one phase offolding corresponding to the F2·fold of the lower unit. This is also evidenced by the marked differences in the occurrence of quartz veins in the two units. The lower unit displays two sets of quartz veins corresponding to the axial planes ofFl and F2, whereas quartz veins parallel to the F2 axial plane are only present in the upper unit. The difference in the structural features between the two units suggest that the deposition of the upper unit postdated the Fl folding phase implying the probable existence of an unconformity in the Paleozoic metasedimentary sequence. The age of this probable unconformity remains uncertain and can be resolved only when the ages of the metasediments at Kg. Kuala Abang are known. INTRODUCTION stratigraphic breaks cannot altogether be ignored. In this respect, the coastal exposures Deformed Paleozoic metasedimentary rocks of similar metasediments at Kg. Kuala Abang comprising metaquartzite, phyllite, slate, etc. are enlightening. In this paper we briefly discuss occur extensively from Kelantan to Johor in some structural features observed at Kg. Kuala the eastern belt of Peninsular Malaysia (Tjia, Abang that may have important implications 1974, 1978, 1989; Chand, 1978; Yap and Tan, for regional structure, stratigraphy and tectonics. 1980; Chakraborty and Metcalfe, 1984; Mohd. Pauzi, 1984). The age of these metasediments Kg. Kuala Abang is located in the Dungun is poorly constrained with only a few isolated district of Terengganu, and lies about 6 km localities yielding fossils, particularly plant northwest of Kuala Dungun and about 2 km fossils, indicating a late Lower Carboniferous northwest ofTg. Jara (Fig. 1). The exposures age (Asama, 1973; Jennings and Lee, 1985). in Kg. Kuala Abang mainly occur as a small Extensive tracts of these metasediments, hillock and as a sea stack in the beach (A and however, remain undated. They are also B in Fig. 2) and as a large road cut. The stratigraphically poorly known as systematic structural features observecl in the beach structural and stratigraphic analyses are largely exposures are the main concern of this paper. lacking. Consequently, the possibility of having These exposures were also noted by others (Tjia, metasediments of different ages with 1974; Mohd. Pauzi, 1984; Gostelow, 1990). We ISSN 0126-5539 Warta Geologi, Vol. 21, No.3, May-Iun 1995, pp.141-146 142 K.R. CHAKRABORTY AND 1. METCALFE have studied the outcrops on several occasions exist that permits the metasediments in the (in 1982 and 1983 by KRC and 1M, and in 1989 beach exposures to be divided into two - by KRC). We wish to record our observations upper and lower - units (Fig. 2). At the and interpretations as they differ from those of present level of erosion, the upper unit comprises other workers in many respects. the upper part of the sea stack exposure and perhaps the top portion of the hillock, whereas STRUCTURAL FEATURES the lower part of the sea stack and most of the hillock constitute the lower unit. The plane The beach outcrops at Kg. Kuala Abang separating the two units is southerly inclined. comprise an interbedded sequence of metaquartzite and meta-argillite (slate/phyllite, In the lower unit, particularly at the base often carbonaceous). The variably deformed of the small hillock outcrop, a refolded reclined metasediments display various types folds, axial fold can clearly be observed (Figs. 2 and 3). planar foliations, and a variety of linear The reclined fold is an earlier F1 structure structures including puckers, bedding-cleavage which has been refolded by an upright F2 fold. intersection, mullions, quartz rods. The The reclined fold axis (F1) plunges 140 towards 1480 as shown in the S-pole diagram constructed metasediments are also cut by a few faults. There are several structural features, discussed from the measured attitudes of the bedding planes around the reclined fold (Fig. 4). The below, that are suggestive of two phases of F1 axial plane dips southeasterly (055°/25°SE). folding, but what is intriguing is that the whole The upright F2 fold at the lower limb of the sequence of the metasediments does not seem reclined fold plunges 16° towards 173°, the to have been affected by these two phases of attitude of its axial plane being 354°/85°E (Fig. folding. The evidence of two-phase folding can only be seen in the lower part of the exposed 5). The F1 and F2 folds are evidently non­ coaxial as indicated by the divergence of their sections, and is apparently lacking in the upper part. A structural disparity thus seems to axial trends. Within the confme of the outcrops, the F1 reclined fold does not extend upto or involve the beds of the upper unit where only open F2 folds are observed. Also, the S-pole diagram prepared from the upper unit beds clearly defines a single fold axis with a plunge of 80 towards 1710 that closely corresponds to the F2 fold of the lower unit (Fig. 5). Evidently, the beds in the upper unit were not affected by two phases of folding. A few lineations that have been measured correspond either to F1 or F2 (Fig. 5). The structural discordance between the two units is further highlighted by the marked difference in the development of quartz veins in the two units that is particularly noticeable in the sea stack outcrop. The lower unit characteristically displays a set of fine quartz veins which are parallel to the F1 axial plane (Fig. 6). They show small scale folding with axial trends similar to F2. This F1 axial planar quartz veins are cut by a second set of quartz veins (quartz-filled fractures) that are parallel to the F2 axial plane. The lower unit thus contains two sets of axial planar quartz veins Figure 1.