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PP 188/12190 ISSN 0126·5539 PERSATUAN GEOLOGI MALAYSIA NEWSLETTER OF THE GEOLOGICAL SOCIETY OF MALAYSIA Jil. 17, No.6 (Vol. 17, No.6) Nov-Dec 1991 UNGAN (Contents) Basir Jasin: The Sabah Complex - A lithodemic unit (a new name for the Chert-Spilite 253 Formation and its ultramafic association) Petroleum Geology Seminar 1991 - Laporan (Report) 260 Welcoming Speech by the President, Geological Society of Malaysia 263 Opening Address by Deputy Minister in the Prime Ministers Department 265 Programme 267 Abstracts of Papers 270 W.K. Fletcher: Behavior of gold in stream sediments 293 Keahlian (Membership) 295 Pertukaran Alamat (Change of Address) 296 Pertambahan Baru Perpustakaan (New Library Additions) 296 Mountain Scientific Expedition Service, Institute of Geology, Academia Sinica 297 Kursus-kursus Latihan dan Bengkel-bengkel (Training Courses and Workshops) 299 Kalendar (Calendar) 300 DIKELUARKAN DWIBULANAN ISSUED BIMONTHLY Majlis (Council) 1991/92 Presiden (President) Ahmad Said Naib Presiden (Vice-President) KhalidNgah Setiausaha Kehormat (Hon, Secretary) Jimmy Khoo Kay Khean Penolong Setiausaha Kehormat (Asst. Hon. Secretary) : Ahmad Tajuddin Ibrahim Bendahari Kehormat (Hon. Treasurer) Lee Chai Peng Pengarang Kehormat (Hon. Editor) TehGuanHoe Presiden Yang Dahulu (Immediate Past President) : Hamzah Mohamad Juruodit Kerhormat (Honorary Auditor) Peter Chew 1991-93 1991-92 Abdul Ghani Mohd. Rafek Andrew Spykerman Mazlan Madon Cheang Kok Keong Nik Ramli Nik Hassan Chin Lik Suan Tan Teong Ring Fateh Chand Teh Guan Hoe (PengerusilChairman) Lee Chai Peng Ng Tham Fatt Lili Sulastri Tan Boon Kong Mazlan Madon Tan Teong Ring Lembaga Penasihat Pengarang (Editorial Advisory Board) AwPeckChin C.A Foss Senathi Rajah Azhar Hj. Hussin N.S. Haile Shu Yeoh Khoon K.R. Chakraborty K.F.G. Hosking P.H.8tauffer Cheang Kok Keong C.S. Hutchison Tan Boon Kong Choo Mun Keong Ian Metcalfe H.D. 'fjia Chu Leng Heng John Kuna Raj Yeap Cheng Hock Dennis N.K. Tan Leong Lap Sau Yin EeHeng 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: fiJ3..757 7036 Fax: fiJ3..756 3900 Printed by Art PrInting Works Sdn. 8hd .• 29 Jolon RJong. 59700 Kuala Lumpur. The Sabah Complex - Alithodemic unit ( a new name for the Chert-Spilite Formation and its ultramafic association) BASIRJASIN Jabatan Geologi, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan. Abstrak: Formasi Rijang-Spilit telah lama digunakan sebagai unit litostratigrafi formal. Penamaan formasi ini sangatlah mengelirukan. Kajian geologi singkapan barn formasi tersebut telah menghasilkan banyak maklumat penting. Di sini dicadangkan Kompleks Sabah sebagai satu unit litodem menggantikan Formasi Rijang-Spilit. Kompleks Sabah ini bukan sahaja menggantikan nama formasi tersebut tetapi merangkumi batuan ultramafik yang berasosiasi dengannya. Kompleks Sabah terdiri daripada batuan peridotit, serpentinit, basalt, spilit, lava banta} danjujukan rijang. Kewujudanradiolaria dalam rijang membolehkan penentuan usia batuan itu denganlebih tepat. Usiajujukan rijangialah Kapur Awal. Batuan volkano mafik-ultramafik dianggap berusia lebih tua daripada Kapur Awal kemungkinannya Jura Akhir. Abstract: The Chert-Spilite Formation has been used as a formal lithostratigraphic unit for a long time. The naming ofthis formation has resul ted in some confusion. Geological investigation ofseveral new outcrops provides new information. Here, I would like to propose Sabah Complex as a lithodemic unit to replace the Chert-Spilite Formation. This complex is not only to replace the Chert-Spilite Formation but to include its ultramafic association. The Sabah Complex is composed of peridotite, serpentinite, basalt, spilite, pillow lava and chert sequence. The occurrence of radiolaria in the chert enable more precise age determination. The age ofthe chert is Early Cretaceous. The mafic-ultramafic volcanic rocks must be older than Early Cretaceous, most probably Late Jurassic. INTRODUCTION stratigraphic code (North American Commission on Stratigraphic Nomenclature, 1983). The Chert-Spilite Formation was introduced by Fitch (1955) for a sequence of COMMENT ON THE TERMINOLOGY OF rocks consisting of chert, shale, sandstone, THE CHERT·SPILITE FORMATION calcareous siltstone, limestone, marl, porcelanite and conglomerate associated with basic volcanic The term Chert-Spilite Formation has rocks comprising pillow lava, basalt, spilite resulted in some confusion. A "Formation" is a and diabase. Eversince then the term has formal lithostratigrahic unit which is usually been used as a formal lithostratigraphic unit. applied to sedimentary, low-grade metamorphic This formation has been reviewed by Wilson and volcanic rocks which were deposited in (1963) but he retained the term Chert-Spilite accordance with the Law of Superposition. Since Formation. the Chert-Spilite Formation is composed of two genetically different classes of rocks viz. The aims of this paper are to revise this formation and to propose a new appropriate sediments and mafic igneous rocks, the word name in accordance with the present "Formation" is not applicable here. Therefore, this unit is not a lithostratigraphic unit. ISSN 0126-5539 Warta Geologi, Vol.17, No.6, Nov-Dec 1991 254 BASIRJASIN The terminology of the Chert-Spilite other rock types such as sandstone, siltstone, Formation is incorrect. A formation name limestone and conglomerate which were consists of a geographic name followed by a previously considered as a part ofthe formation lithic designation or by the word "Formation". (Fitch, 1955; Wilson, 1963) are of younger age The word "Chert-Spilite" cannot be used as a and are therefore excluded from this complex. name of a formation. In order to avoid further The chert is thinly bedded and contains confusion the term Chert-Spilite Formation numerous skeletons of radiolaria of various should be abandoned. shapes and sizes. The chert is made up of Sanudin Hj. Tahir and Tan (1986) have biogenic silica (radiolarite). The chert is suggested that the Chert-Spilite Formation interbedded with siliceous shale. The shale is should be included in a stratigraphic unit called highly weathered and soft. This rhythmic the Sabah Melange. I disagree with this idea bedding is called ribbon chert. This chert because not all the Chert-Spilite Formation sequence overlies comformably the mafic- occurred as olistholiths in chaotic deposits ultramafic rocks. This type of chert is usually (melange), but only some boulders or blocks of found in the deep water environment. the formation might have been transported Mafic-ultramafic volcanic rocks consist of into younger formation viz. the Ayer Formation, pillow lava, basalt, spilite, serpentinite, the Garinono Formation and the Kuamut serpentinised peridotite, and peridotite. These Formation. In other places such as in Kudat, rocks are slightly sheared. The boundaries of Taritipan, Telupid, and Banggi Island the Chert- these rocks are not clear. Serpentinite and Spilite Formation is not associated with chaotic peridotite are usually found in the upper layer deposits. The term melange is neither a of the outer mantle (Nicolas, 1989). They lithostratigraphic nor a lithodemic unit. The probably crystallised during the early phase of age of the melange is very much younger than seafloor rifting or spreading. Spilite, basalt, the actual age of the Chert-Spilite Formation. and pillow lava were formed from the cooling According to North American Commission ofmolten liquid which escaped through fissures on Stratigraphic Nomenclature (1983), two or or fractures particularly in oceanic crust. This more genetically different classes ofrocks which rock association represents the initial oceanic are found together and cannot be differentiated crust. This mafic-ultramafic rock association should be grouped as a complex. A complex is was actually a part ofinitial oceaniccrust formed a lithodemic unit consisting of a mixture or during the early period of rifting prior to the assemblage of rock belonging to two or more deposition of the chert sequence. classes of rocks, that is igneous, sedimentary and metamorphic rocks. The term complex is DISTRIBUTION OF THE SABAH more appropriate for naming this rock COMPLEX association. Here, I would like to propose the The distribution of the Sabah Complex is word "Sabah Complex". The Sabah Complexis more or less similar to those of the Chert- not only to replace the Chert-Spilite Formation . Spilite Formation but it includes the ultramafic but to include its ultramafic association. rocks. The Sabah Complex is mainly found in Banggi Island, Kudat, Taritipan, Telupid, LITHOLOGY OF SABAH COMPLEX Segama valley, and Pulau Timbun Mata (Fig. 1.). Smaller outcrops may be found in Ranau The Sabah Complex is mainly composed and Sandakan areas. Fragments of the Sabah of two classes of rocks, that is sedimentary Complex are found as olistoliths in the younger rocks which consists of thinly bedded chert chaotic formations viz. Kuamut, Garinono, and interbeds with siliceous shale and mafic- Ayer formations. ultramafic igneous rocks, which comprises basalts, spilite, pillow lava, serpentinite, serpentinised peridotite and peridotite. This AGE OF THE SABAH