The Devonian Lower Carboniferous succession in Northwest Peninsular Malaysia

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1 Journal of Asian Earth Sciences 24 (2005) The Devonian Lower Carboniferous succession in Northwest Peninsular Malaysia Hakif Hassan Meor*, Chai Peng Lee Geology Department, University of Malaya, Kuala Lumpur 50603, Malaysia Received 1 March 2003; accepted 18 September 2004 Abstract A new stratigraphic nomenclature is proposed for the approximately 600 m thick, mainly clastic transitional sequence between the underlying Mempelam Limestone and overlying Kubang Pasu/Singa Formation in northwest Peninsular Malaysia. This sequence represents shallow marine deposits of the continental margin of the Sibumasu Terrane during the Middle Palaeozoic (Devonian Carboniferous). It is separated into several formations. The Timah Tasoh Formation is an approximately 76 m sequence consisting of 40 m of laminated tentaculitid shales at the base, containing Monograptus yukonensis Jackson and Lenz and Nowakia (Turkestanella) acuaria Alberti, giving an Early Devonian (Pragian Emsian) age, and about 36 m of rhythmically interbedded, light coloured argillo-arenites. The Chepor Formation is about 90 m thick and consists mainly of thick red mudstone interbedded with sandstone beds, of Middle to Late Devonian age. A new limestone unit is recognized and named the Sanai Limestone, which contains conodonts of Famennian age. The Binjal Formation consists of red and white mudstone interbedded with sandstone beds showing Bouma sequences. The Telaga Jatoh Formation is 9 m thick and consists mainly of radiolarian chert. The Wang Kelian Formation is composed of thick red mudstone beds interbedded with silty sandstone, and contain fossils indicative of an Early Carboniferous (Visean) age. The succession was deposited on the outer shelf, with depositional environments vertically fluctuating from prodelta to basinal marine. The Devonian Carboniferous boundary is exposed at Hutan Aji and Kampung Guar Jentik, and indicates a major regressive event during the latest Devonian. q 2004 Elsevier Ltd. All rights reserved. Keywords: Sibumasu; Continental margin sequence; Unconformities; Transgression/regression; Hangenberg event 1. Introduction Early work on the Devonian of Peninsular Malaysia focused mainly on well exposed coastal outcrops on the islands of Langkawi. However, these outcrops are structurally complex, and stratigraphic relationships between certain units confusing. Recently, several new outcrops of equivalent rocks exposed in the mainland state of Perlis have been discovered and reported (Lee and Azhar, 1991; Meor and Lee, 2002). The new findings are used here to propose a new stratigraphic nomenclature for the Devonian Carboniferous succession of northwest Peninsular Malaysia, and to further resolve the Devonian Carboniferous history of the Sibumasu Terrane. * Corresponding author. address: hakif23@yahoo.com (H.H. Meor). 2. History of stratigraphic nomenclature Jones (1966) was the first to make a detailed map of the Palaeozoic rocks in the northwestern part of what was then called Malaya. He recognized four Palaeozoic formations exposed on the islands of Langkawi; the Cambrian Machinchang Formation, the Ordovician to Silurian Setul Formation, the Carbo-Permian Singa Formation (and its equivalent on the mainland, the Kubang Pasu Formation) and the Chuping Limestone. The scarcity of Devonian rocks was explained by a regional unconformity proposed between the Setul Formation and Singa Formation (Jones, 1981). The unconformity was said to be between the arenoargillites of the Upper Detrital Member of the Setul Formation, and the red pebbly mudstone of the Langgun Red Beds, considered as the base of the Singa Formation. This unconformity was never observed, but was inferred /$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi: /j.jseaes

2 720 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) based on angular strike relations and the occurrence of red pebbly mudstones interpreted as a basal conglomerate. The presence of this unconformity was, however, later refuted (Ahmad Jantan, 1973; Yancey, 1975). The contact between the Upper Detrital Member and the Langgun Red Beds was demonstrated to be conformable. The two once separate Devonian units were now continuous, and this led to suggestions by Yancey (1975) of a single Devonian unit. Gobbett (1972) proposed the name Rebanggun Beds (combination of the names Rebak and Langgun Island, where outcrops of the unit were found) for the Langgun Red Beds. The Upper Detrital Member was also clearly different from the main Setul Formation, as the Setul Formation was predominantly bedded limestone, while the Upper Detrital Member was composed of siliciclastics. Yancey (1975) was the first to propose the melding of the Upper Detrital Member and the Langgun Red Beds into one continuous Devonian unit, which, unfortunately, he left unnamed. A new stratigraphic nomenclature has been proposed by Cocks et al. (2005), in which separate formations were erected for the Upper Setul Limestone and Lower and Upper Detrital Members of the former Setul Formation. Recently, new exposures in the state of Perlis show the presence of a sedimentary succession equivalent to the Devonian and Carboniferous rocks of Langkawi, but relatively less deformed, giving us a clearer view of the middle Palaeozoic stratigraphy of northwest Peninsular Malaysia. 3. Study area The study focused on isolated outcrops throughout Perlis and north Kedah, in northwest Peninsular Malaysia (Fig. 1). Four main outcrops were recognized and studied in detail: 1. Kampung Guar Jentik 2. Hutan Aji 3. Kampung Wang Kelian 4. Teluk Mempelam, Pulau Langgun Kampung Guar Jentik The first locality is Kampung Guar Jentik (KampungZvillage), in the Beseri District of Perlis ( N; E). Middle Palaeozoic rocks are exposed as a hilly ridge trending roughly north south along the R121 road linking Kangar and Kaki Bukit, just south of the Timah-Tasoh Dam. The ridge is locally called Guar Sanai, and is separated into three small hills, here referred to as Hills A, B and C from south to north (Fig. 2). The outcrop is completely isolated as a faulted block, and is surrounded by lowland developed into paddy fields. It is bounded by the Setul Boundary Range on the west, and karstic hills of the Chuping Limestone far towards the east. The rocks were exposed due to quarrying. Fig. 1. Locality map of outcrops of the Middle Palaeozoic succession in northwest Peninsular Malaysia. (1) Guar Sanai ridge, Kampung Guar Jentik, Beseri District, Perlis; (2) Hutan Aji, Kangar District, Perlis; (3) Teluk Mempelam, Pulau Langgun, Langkawi; (4) Kampung Wang Kelian, north Perlis; and (5) Kampung Jelutong, north Kedah.

3 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 2. Geological outcrop map of the Kampung Guar Jentik, Perlis, exposure. Location of the map in Fig Hutan Aji There is a quarry site, called the Bumita Quarry, at Kampung Binjal, Hutan Aji ( N; E), just 5 km south of Kangar, the capital of Perlis state. The quarry is situated around a hill, encompassing an area of roughly 300 km square, at Kampung Binjal and adjacent Kampung Behor Chepor (Fig. 3). Similar to Kampung Guar Jentik, the exposure is also a large, isolated, faulted block, this time surrounded by villages. This area was studied by Kobayashi and Hamada (1973) and Jones (1981) Teluk Mempelam, Pulau Langgun The most famous exposure of Devonian rocks in Peninsular Malaysia, Teluk Mempelam is on the northwestern coast of Langgun Island (PulauZIsland), offshore of the west coast, and just northeast of Langkawi Island ( N; E). The type section for the Upper Detrital Member is located here. The exposure on Pulau Langgun is in the form of low cliffs, promontories and boulders along the northwest coast. The rocks are not well exposed farther inland due to thick vegetation Kampung Wang Kelian The Kampung Wang Kelian outcrop was briefly described by Lee and Azhar (1991). It is located south of Kampung Wang Kelian ( N; E) on hilly terrain, at an elevation of roughly m above sealevel. The exposures are in the form of roadcuts along the road connecting Kaki Bukit and Kampung Wang Kelian. 4. Stratigraphic nomenclature A preliminary description of newly exposed Devonian Carboniferous rocks in Perlis state was published in Meor and Lee (2002), in which the authors proposed a single stratigraphic unit for rocks of the transitional sequence

4 722 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 3. Geological outcrop map of the Hutan Aji, Perlis, exposure. Location of the map in Fig. 1. between the Upper Setul Limestone and the Singa/Kubang Pasu Formation, called the Jentik Formation. The Jentik Formation was defined as a mainly siliciclastic unit consisting predominantly of pure, massive, grey, red, yellow or brown coloured mudstone and shale, clean quartz sandstone, with minor black laminated shales, cherts and bedded limestone. An unconformity was inferred to be present between the Jentik Formation and Kubang Pasu Formation. The Jentik Formation was divided into six separate subunits at that time. However, continuing work has shown that the subunits are sufficiently distinct lithologically to form separate formations. A major paraconformity has also been identified lower in the Jentik Formation type section, increasing the complexity. The authors here discard the stratigraphic nomenclature proposed in Meor and Lee (2002), and reject the notion of a single, Jentik Formation, due to the influx of new data. A new nomenclature is erected, with the subunits of the former Jentik Formation upgraded to formation status. Six formations are recognized from oldest to youngest: the Timah Tasoh, the Chepor, the Binjal, the Sanai Limestone, the Telaga Jatoh and the Wang Kelian formations (Fig. 4) Timah Tasoh Formation The name Timah Tasoh Formation is proposed by Cocks et al. (2005) for the siliciclastic sequence formerly known as the Upper Detrital Member of the Setul Formation (Jones, 1981). The name is derived from the Timah Tasoh Reservoir, just north of the type section, in north Perlis. The exposure on Pulau Langgun, Langkawi, reaches 170 m

5 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 4. Proposed stratigraphic nomenclature for the Middle Palaeozoic succession in northwest Peninsular Malaysia. in thickness, but mainland outcrops show a thickness of about 76 m. The Timah Tasoh Formation is further divided into two separate members Lalang Member This subunit is exposed in Kampung Guar Jentik and Hutan Aji, and Pulau Langgun, and overlies the Upper Setul Limestone (renamed as the Mempelam Limestone Formation in Cocks et al., 2005 their nomenclature is used here). The name Lalang Member is derived from the village of Kampung Behor Lalang, which is just southwest of Kampung Binjal, Hutan Aji area, and is closer to the outcrop of the unit. The Lalang Member encompasses the basal beds of the former Upper Detrital Member of Jones (1981), and is the name proposed for Unit 1 of the former Jentik Formation (sensu Meor and Lee, 2002). The unit is observed to be conformably underlain by the Mempelam Limestone at Teluk Mempelam, Pulau Langgun, while the contact is faulted at Kampung Guar Jentik and Hutan Aji. The Lalang Member is overlain by areno-argillites of the Bukit Raja Member (Fig. 5a). The exposed thickness in Hutan Aji is estimated to be about 40 m (Fig. 6). The unit is almost wholly argillaceous, made up mainly of black, grey and brown, laminated, tentaculitid shale and siltstone. The lower boundary of the Lalang Member is earliest Devonian (Lochkovian) in age, based on the occurrence of Lochkovian aged conodonts in the uppermost beds of the Mempelam Limestone on Pulau Langgun (Igo and Koike, 1973) and scyphocrinoid loboliths (Lee, 2001). But the upper parts of the unit range into the Pragian and earliest Emsian. The shales are highly fossiliferous, with abundant dacryoconarid remains, including Nowakia (Turkestanella)

6 724 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 5. Representative lithologies of the Middle Palaeozoic succession in northwest Peninsular Malaysia. (a) Black shales of the Lalang Member (at bottom) underlying sandstone and mudstone of the Bukit Raja Member, Timah Tasoh Formation. Hill C, Kampung Guar Jentik, Perlis. (b) Distal turbidites with scoured bottoms of the Chepor Formation, at Hill C, Kampung Guar Jentik, Perlis. (c) Devonian Carboniferous boundary section at Hill B, Kampung Guar Jentik. The Sanai Limestone is paraconformably overlain by cherts of the Telaga Jatoh Formation. Paraconformity marked by stippled line. (d) Turbidite sandstone showing Bouma sequence, Binjal Formation. Fig. 6. Stratigraphic columns and correlation of main exposures of the Lalang Member and Bukit Raja Member, Timah Tasoh Formation. N. (T) a, Nowakia (Turkestanella) acuaria; N (A), genus Nowakia (Alaina); M, genus Monograptus; y, species yukonensis.

7 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 7. Representative fossils of the Lalang Member, Timah Tasoh Formation (Early Emsian) in Perlis. (a) and (b) Plectodonta (Plectodonta) forteyi Boucot and Cocks. (a) Pedicle valve. Hill C, Kampung Guar Jentik. GSCU1012a. (b) Brachial valve. Hill C, Kampung Guar Jentik. GSCU1003. (c) Plagiolaria poothai Kobayashi and Hamada, partial cephalon. Hill A, Kampung Guar Jentik. GSCU1007. (d) and (e) Nowakia (Alaina) matlockiensis Alberti. (d) Hill C, Kampung Guar Jentik. GSCU1014. (e) Hill C, Kampung Guar Jentik. GSCU (f) Nowakia (Turkestanella) acuaria posterior Alberti. Hill C, Kampung Guar Jentik. GSCU (g) Monograptus langgunensis Jones. Bumita Quarry, Hutan Aji. Mal/Bum/001b. (h) Monograptus yukonensis fangensis Jaeger, Stein and Wolfart. Bumita Quarry, Hutan Aji. Mal/Bum/001. Scale barz1 mm. acuaria acuaria Richter, Nowakia (Turkestanella) acuaria posterior Alberti, Nowakia (Alaina) matlockiensis Chapman, Metastyliolina sp. and Styliolina sp. (Fig. 7). Also present in lesser numbers are the brachiopods Plectodonta (Plectodonta) forteyi Boucot and Cocks, Lissatrypa? sp. Boucot, Cocks and Racheboeuf and Orbiculoidea sp. (Fig. 7), and unidentified pelecypods. Some horizons contain monograptid fossils. Several specimens of Monograptus langgunensis Jones and Monograptus yukonensis fangensis Jaeger, Stein and Wolfart were found in the exposure at Hutan Aji (Fig. 7), and remains of Monograptus aequabilis? associated with a fragmentary rhabdosome probably belonging to M. yukonensis fangensis Jaeger, Stein and Wolfart were collected from the exposure at Hill C, Kampung Guar Jentik. Monograptus langgunensis Jones was first reported from the black tentaculitid shales of Teluk Mempelam, Pulau Langgun, by Jones (1973a). The occurrence of M. yukonensis is indicative of the M. yukonensis Zone (Jaeger, 1988), which gives an Early Devonian (Early Emsian) age. The tentaculitids Nowakia (Turkestanella) acuaria posterior Alberti and Nowakia (Alaina) matlockiensis Chapman are also characteristic of the Early Emsian (Alberti, 1997). The abundance of pelagic tentaculitids are indicative of Boucot s (1975) Benthic Assemblages 4 5, which suggest relatively deep waters, between 50 and 200 m in depth (Brett et al., 1993). Carbonaceous, laminated shale and sparse benthic fauna suggests a dysoxic environment. Lack of coarse grained siliciclastics and current structures show a low energy setting. The overall interpretation is that of a basin starved of sediment with sluggish circulation Bukit Raja Member This represents the remainder of the Upper Detrital Member, also known as Unit 2 of the former Jentik Formation. The unit is about 18 m thick at Kampung Guar Jentik (Fig. 5a) and Hutan Aji, but the exposures are tectonically controlled. The name is derived from the local name of a small hill being actively quarried at Hutan Aji, where the thickest section is exposed. The observed thickness of the unit on Pulau Langgun is 130 m, but there are repetition and deletion of beds due to the complex folding and faulting. The unit is predominantly made up of light coloured sandstone beds interbedded with shales. The unit is barren of body fossils, but contains abundant trace fossils in the form of short, vertical to oblique burrows, identified as Psilonichnus? and Macanopsis (Fig. 8). The predominance of arenaceous deposits and vertical burrows indicate a shallower, moderate to high energy environment compared to the underlying Lalang Member. The trace fossils are characteristic of the Psilonichnus ichnofacies, indicative of a supralittoral, moderate to high

8 726 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 8. Trace fossils in the Bukit Raja Member, Timah Tasoh Formation (Emsian-Eifielian?) of Kampung Guar Jentik, Perlis. (a) Macanopsis. GSCU2001. (b) and (c) Psilonichnus?. (b) Top view of bedding surface showing paired burrows. GSCU2002. (c) Side view of single burrow. GSCU2001. Scale barz1 cm. energy environment (e.g. beach-backshore, dune areas and supratidal flats on the coast). Exposures of this unit in Pulau Langgun are highly folded, but also show a predominance of quartzites, and limonitisation Chepor Formation The name Chepor Formation is used for the red beds exposed in the Bumita Quarry of Hutan Aji and at Hill A and C, Kampung Guar Jentik. The most complete section, at Bumita Quarry, shows a maximum thickness reaching 90 m (Fig. 3). The name is derived from Kampung Behor Chepor, which is located just east of the Bumita Quarry. The lithology is mainly thick, red and grey coloured fossiliferous mudstone interbedded with quartz sandstone (Fig. 9). The Chepor Formation can be divided further into two smaller subunits, i.e. member CF-1 and member CF-2. Member CF-1 represents the bottom half of the Chepor Formation, and is exposed at Kampung Guar Jentik (65 m thick) and Hutan Aji (40 m thick). The lithology is predominantly thick red, fossiliferous mudstone interbedded with thin quartz sandstone. The beds in the bottom half of the unit show thin, normal grading from fine sandstone to mudstone, with scoured bases (Fig. 5b). These beds are interpreted as turbidites. Abundant fossils of brachiopods, bivalves, trilobites, gastropods, crinoids and Fig. 9. Representative sections of the Chepor Formation. Location of the logged sections shown in Fig. 2 (C1, C2, C3) and Fig. 3 (C4, C5, C6).

9 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) corals are found in concentrated assemblages. Ambocoeliid brachiopods are characteristic of the Chepor Formation. The occurrence of Emanuella malayensis Hamada gives a Middle-Late Devonian age for member CF-1. Member CF-2 is exposed only at Hutan Aji, conformably overlying member CF-1. This subunit, consists mainly of grey mudstone interbedded with thin siltstone, thin to medium thick beds of laminated, pebbly or massive sandstone, and minor red mudstone, with a 9 m black mudstone facies forming the boundary between the Chepor Formation and the Binjal Formation. The maximum exposed thickness at the Bumita Quarry is about 49 m, but a large thrust fault runs through the middle of the exposure (Fig. 3). The trilobite Waribole perlisensis Kobayashi and Hamada is found in the unit. Waribole ranges from the Middle Famennian to the Visean. The brachiopod Chonetipustula Paeckelmann, which is represented by a single valve in member CF-2 (Fig. 10c), also ranges from the Late Devonian into the Early Carboniferous. The age of member CF-2 is more likely to be Late Devonian, based on the occurrence of the gastropod Australonema Tassel associated with the trilobites in the same rocks (Fig. 10a and b). Based on all the evidence, it is considered that the age of the Chepor Formation is Middle-Late Devonian (Givetian or Frasnian Famennian). The depositional environment of the Chepor Formation is interpreted as a marine prodelta, based on the predominance of mud, abundance of shell accumulations and the abundance of ambocoeliid brachiopods. Turbidites were deposited by turbidity currents moving down the delta slope. The facies association in the Chepor Formation shows all the characteristics of a marine prodelta environment. Prodelta environments are usually predominated by fine grained siliciclastics, with a maximum grain size of very fine sand, with beds showing planar and cross laminations, and abundance of shell accumulations (Allen, 1964). The Chepor Formation differs only in having a coarser grained element, up to medium sand, but generally fits well with a prodelta depositional model. The peculiar ambocoeliid brachiopods Echinocoeliopsis sculpta Hamada and Emanuella malayensis Hamada are characteristic of the red beds. The ambocoeliids provide the biofacial evidence of a prodelta to delta front interpretation, as they are often associated with such deposits (Bowen et al., 1974; Goldman and Mitchell, 1990). A 9 m thick black to dark grey mudstone layer forms the top boundary of the Chepor Formation with the overlying Binjal Formation at the Bumita Quarry. The layer does not contain any benthic fossils, except for monospecific assemblages of large Posidonia bivalves. The only fossils present are unidentified ammonoids. Finely dispersed pyrite is abundant. The position of this black mudstone layer between Late Devonian red beds of the Chepor Formation and the overlying Early Carboniferous (Tournaisian) beds of the Binjal Formation is intriguing, as it might be possible to correlate it with the global Hangenberg Anoxic Event, which is marked worldwide by black shale deposition just before the end of the Famennian Binjal Formation There is an upper red bed unit exposed in Hutan Aji, Perlis and north Kedah which is not observed in Kampung Guar Jentik, Perlis. This unit is named the Binjal Formation, after the type locality Kampung Binjal, Hutan Aji, Perlis. The boundary between the Binjal Formation and the underlying Chepor Formation is marked by a sequence boundary, in the form of a paraconformity, at Bumita Quarry, Hutan Aji, Perlis (Fig. 11). The unit is observed to be in fault contact with the Bukit Raja Formation at Teluk Mempelam, Pulau Langgun. The sandstone beds of the Binjal Formation are thicker and coarser grained, and beds are more grey than red (Fig. 12). The sequence also shows alternating deposition of graded sandstone and pebbly sandstone beds showing Bouma sequences, with fossiliferous mudstone (Fig. 5d). Fossils are abundant, especially brachiopods, including ambocoeliids. The brachiopod Tournquistia burtonae Hamada is common in this unit. The genus Tournquistia is known from the Early Carboniferous of Europe. The bivalve Posidonia intermedia Sarkar is restricted only to the Binjal Formation in vertical distribution. Comparisons with other members of the genus Fig. 10. Representative fossils of member CF-2, Chepor Formation (Famennian), at Bumita Quarry, Hutan Aji, Perlis. (a) and (b) Australonema sp. (a) FL5002a. (b) FL5002b. (c) Chonetipustula sp. FL8001. Scale barz1 mm.

10 728 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 11. Comparison of the Devonian Carboniferous boundary exposed at Bumita Quarry, Hutan Aji, and Kampung Guar Jentik, both in Perlis. Posidonia indicate that the Perlis species is indistinguishable from Posidonia becheri Bronn, which is characteristic of the Carboniferous. The fossils indicate an Early Carboniferous age for the Binjal Formation. The fact that the unit is overlain by Late Tournaisian chert beds (Telaga Jatoh Formation) further restricts the age to Earliest Carboniferous (Tournaisian). The predominance of mud, shell accumulations and ambocoeliid brachiopods indicate a prodelta depositional environment similar to the Chepor Formation, but the Binjal Formation is sandier, with more numerous and thicker sandstone beds. Perhaps the Binjal Formation represents the transition between the delta slope and the prodelta, i.e. the delta front. The Binjal Formation may be correlated to the Langgun Red Beds on Pulau Langgun, but the Pulau Langgun exposure is very small, and a detailed restudy of the palaeontology is needed to confirm their relationship Sanai Limestone Meor and Lee (2003) reported a Late Devonian limestone unit exposed at Kampung Guar Jentik. This unit was named the Sanai Limestone Member, and was considered part of the former Jentik Formation. It is here upgraded to formation status, with the name Sanai Limestone. It is located stratigraphically above the Chepor Formation red beds at Kampung Guar Jentik, but is laterally equivalent to the upper half of the Chepor Formation sequence at Hutan Aji (member CF-2). The unit is faulted, but is at least 20 m thick. The lower boundary with member CF-1, Chepor Formation is not exposed, but the upper boundary is clearly observed at Hill B, Kampung Guar Jentik. The lithology changes abruptly at the upper boundary from carbonates of the Sanai Limestone to shales and cherts of the Telaga Jatoh Formation (Figs. 5c and 15). The lithology is mainly grey coloured, bedded micritic limestone, with shaley partings and stylolites. Polygonal surface marks are interpreted as synaeresis cracks. The Sanai Limestone contains abundant pelagic fossils, including tentaculitids, conodonts and straight-coned nautiloids. Also found are ostracod remains and trilobites. The occurrence of the conodonts Palmatolepis glabra Ulrich and Bassler and Palmatolepis quadrantinodosalobata Sannemann give a Late Devonian (Lower Famennian) age for the limestone (Fig. 13), which makes it roughly equivalent to the Famennian aged Waribole bearing beds of the upper half (member CF-2) of the Chepor Formation exposed at Hutan Aji. Planar bedding, micritic texture and predominance of pelagic fossils is characteristic of pelagic limestone deposited in relatively deep water. The conodonts are mostly palmatolepids and polygnathids (Meor and Lee, 2003), which are characteristic of biofacies II of Sandberg and Dreesen (1984), interpreted as slope to basinal facies. The Sanai Limestone is interpreted as pelagic limestone deposited near the continental margin, either on the outer shelf region, slope or even in a basinal environment Telaga Jatoh Formation The unit is exposed at Hill B, Kampung Guar Jentik in Perlis, and at Bukit Telaga Jatoh, Bukit Beringin and Kampung Jelutong in north Kedah (Basir Jasin, 1995). Early Carboniferous chert beds exposed in northwest Peninsular Malaysia were previously considered to be part of the base of the Kubang Pasu Formation (Basir Jasin, 1995; Basir Jasin and Zaiton Harun, 2001). However, the beds are lithologically distinct enough to form their own stratigraphic

11 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 12. Representative sections of the Binjal Formation. Location of the logged sections shown in Fig. 3 (C7, C8, C9, C10, C11). Fig. 13. Conodonts from the Sanai Limestone (Famennian) of Kampung Guar Jentik, Perlis. (a) Palmatolepis quadrantinodosalobata Sannemann. GSBU4S0-7. (b) and (c) Palmatolepis glabra Ulrich and Bassler. (b) GSBU4S002. (c) GSBU4S001. (d) Palmatolepis minuta Branson and Mehl. GSBU4S0-2. Scale barz200 mm.

12 730 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) unit, here named the Telaga Jatoh Formation, derived from Bukit Telaga Jatoh, a hill exposing the thickest sequence of the unit in the Pokok Sena area, north Kedah. The thickness at Kampung Guar Jentik is only about 10 m. The lithology consists mainly of rhythmically alternating, planar beds of grey coloured chert and black shale. Slump structures are common. Basir Jasin and Zaiton Harun (2001) reported Early Carboniferous (Late Tournaisian) radiolaria from the chert beds. The bedded chert was deposited in deep water during high plankton productivity, and is considered to be a relatively deep water, continental margin chert by Basir Jasin et al. (2003) Wang Kelian Formation The name Wang Kelian Red Beds, proposed for the red bed unit at Wang Kelian, northernmost Perlis, by Lee and Azhar (1991) is preserved here, but changed from bed to formation status. This red mudstone unit is stratigraphically younger in age compared to the Chepor Formation and Binjal Formation. Exposures of the unit are found at the type locality in Kampung Guar Jentik, Kampung Wang Kelian and also in Kampung Jelutong, north Kedah (Kobayashi and Hamada, 1973). The exposed thickness at Kampung Guar Jentik is about 35 m, but the unit is in fault contact with the overlying and underlying rocks. Geologic mapping at Kampung Wang Kelian indicates a possible thickness of 300 m. The lower boundary with the underlying Telaga Jatoh Formation at Kampung Guar Jentik is faulted. The contact at Kampung Jelutong is gradual, with the lithology gradually changing from bedded chert, to black shale, followed by red mudstone of the Wang Kelian Formation. The predominant lithology of the Wang Kelian Formation is thick, brownish red to purple mudstone interbedded with medium thick, muddy sandstone beds (Fig. 14). Some of the beds show channel-like structures. At Kampung Guar Jentik the Wang Kelian Formation is observed to be overlain unconformably by dark pebbly siltstone and greywackes of the Kubang Pasu Formation. Meanwhile, in Kampung Wang Kelian, the red mudstone passes into black pebbly siltstones of the Singa Formation. The exact contact between the units is not observed, due to thick vegetation Fig. 14. Representative sections of the Wang Kelian Formation, in Kampung Wang Kelian and Hill B, Kampung Guar Jentik.

13 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) and soil cover, but the dip angle and direction do not change between the two units. Fossils are sparse in the Wang Kelian Formation. Most of these are ambocoeliid brachiopods, pelecypods and the trilobite Macrobole kedahensis Kobayashi and Hamada. The age of the unit is most probably Early Carboniferous (Visean), based on the occurrence of Macrobole (Famennian to Visean) and the stratigraphic position of the unit overlying Late Tournaisian chert beds. The sedimentology is very similar to that of the Chepor Formation and Binjal Formation. Concave upwards, erosive bases of some sandstone beds are here interpreted as bowl-shaped slump scars. The Wang Kelian Formation is also characterized by the occurrence of ambocoeliid brachiopods. Ambocoeliids are characteristic of marine, delta front to prodelta environments, and Boucot (1975) puts them in Benthic Assemblages 4 5. Overall, the deposits of the Wang Kelian Formation are interpreted as sediments of a marine, prodelta to delta front facies, strongly influenced by tidal currents. 5. Correlation The stratigraphic correlation of Middle Palaeozoic rocks on the Sibumasu Terrane is summarized in Fig Mempelam Limestone Formation (formerly upper Setul Limestone) Homologous to the Silurian-Earliest Devonian aged Mempelam Limestone (Cocks et al. (2005) is the Kuan Tung Formation (Wongwanich et al., 1990), also known as part of the Thung Song Limestone (Brown et al., 1951), in Satun, southernmost Thailand. This unit is the northern extension of the Mempelam Limestone and is similar in lithology and faunal composition. The Linwe Formation (Myint Lwin Thein, 1973) of Myanmar is a 550 m argillaceous limestone unit with phacoidal texture similar to the Mempelam Limestone, and it contains graptolites of Silurian age. The Mempelam Limestone is replaced eastwards by rocks of the basinal facies, i.e. the Mahang Formation in Kedah, which contains Upper Silurian (Wenlock) aged graptolites (Jones, 1973a) and the Baling Group in north Perak (Upper Llandovery graptolites reported from Sungai Rui Valley, north Perak; Gobbett and Hutchison, 1973). Limestone deposition was widespread in parts of present day southern Perak and Kuala Lumpur during the Upper Silurian, represented by the Kim Loong No. 1 Beds at Kampar (of possible Silurian to Lower Devonian age; Suntharalingam, 1968), and the Kuala Lumpur Limestone (Upper or Middle Silurian in age, based on fossils described in Thomas, 1963; Boucot et al., 1966). Fig. 15. Stratigraphic correlation of the Middle Palaeozoic successions on the Sibumasu Terrane. Map on the right showing location of stratigraphic columns.

14 732 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Lalang Member, Timah Tasoh Formation The Lower Devonian (Emsian) is represented in Perlis by the basinal facies of the Lalang Member of the Timah Tasoh Formation. Homologous to this unit in the north are black tentaculitid shales of Member 1 of the Pa Samed Formation in Satun Province (Wongwanich et al., 1990), which contains dacryoconarids indicative of the Early Emsian (Boucot et al., 1999). The Pa Samed Formation is actually the northern extension of the mid-palaeozoic succession in Perlis. Both these units are likely to be extensions of the basinal facies which were still being deposited in the east as black shales of the Mahang Formation and Bendang Riang Formation of the Baling Group, exposed in parts of Penang, south and central Kedah, and northwest Perak. Dacryoconarid tentaculitids including Nowakia acuaria Richter, monograptids, brachiopods and trilobites of Early Emsian age are found in all of these units (Burton, 1967a,b). Monograptus cf. yukonensis was found associated with tentaculitids in the Mahang Formation of central Kedah (Jones, 1973a). Farther north, in Myanmar, a 60 m sequence of black shales and grey limestone called the Zebingyi Beds also contains a similar fauna. Monograptus atopus Boucek has been reported from the rocks (Anderson et al., 1969; Berry and Boucot, 1972), associated with tentaculitids identified as Tentaculites elegans, a species now regarded as Nowakia acuaria s.l. (Boucek, 1964). The first author has had the opportunity to personally analyze some of the Myanmar material in the Jaeger collection (Museum fur Naturkunde) and they do resemble Nowakia acuaria s.l. The occurrence of M. atopus clearly indicates an Emsian age. The Kanthan limestone in the north Kinta Valley ranges from the Early Devonian to the Permian (Lane et al., 1979; Metcalfe, 1979, 1981, 2002) and the dolomites of the Kim Loong No. 1 Beds in Kampar may also be Early Devonian (Suntharalingam, 1968) Bukit Raja Member, Timah Tasoh Formation and member CF-1, Chepor Formation The age of the Bukit Raja Member is not known, as no body fossils have been found. But it is most probably Middle Devonian in age. The Chepor Formation probably ranges from the Givetian, or Frasnian, to the Early Famennian. Sandstone and red mudstone beds in Satun Province, known as Member 2 of the Pa Samed Formation, are probably the lateral equivalent of the Chepor Formation and Bukit Raja Member. Wongwanich et al. (1990) suspect a Mid-Devonian age for the whole Pa Samed Formation, but no faunal data has been published. The Chepor Formation extends into northern Kedah. Alexander and Muller (1963) reported Late Devonian conodonts from the Kanthan Limestone. Mid-Late Devonian limestone at Kampar have been named the Thye On Beds (Suntharalingam,1968). The shales of the Wetwin Member of the Maymyo Dolomite Formation (Amos, 1975) in Myanmar contains Givetian to Frasnian aged fossils. The Middle and Late Devonian of Yunnan is represented by several facies, including dolomitic limestone interbedded with shale and ribbon-bedded cherts in the Changning Menglian Suture Zone (Metcalfe, personal communication) Sanai Limestone and member CF-2, Chepor Formation An extension of the Early Mid Famennian Sanai Limestone may be represented by Member 3 of the Pa Samed Formation, which is also made up of bedded limestone. The limestone overlies Mid-Devonian red beds in Satun Province, but the fossil composition and age have yet to be described. The Sanai Limestone is replaced in south Perlis and Kedah by Famennian-aged grey, red and black mudstone beds of the Chepor Formation. It can be roughly correlated to the Kanthan Limestone and the Thye On Beds of central and south Perak Telaga Jatoh Formation and Binjal Formation The Binjal Formation is Tournaisian in age. Unfortunately bedded cherts are not exposed near the Binjal Formation outcrop in Bumita Quarry, but white mudstone and sandstone is observed to underlie the Telaga Jatoh Formation in Kampung Jelutong, north Kedah. These mudstone and sandstone beds may be extensions of the Binjal Formation in north Kedah. The Langgun Red Beds of Langkawi maybe the lateral equivalent to the Binjal Formation. The rocks of the Langgun Red Beds lie paraconformably above the Timah Tasoh Formation on Pulau Langgun (Cocks et al. (2005). No Early Carboniferous bedded cherts have been observed in the Pa Samed Formation. Instead, massive fine sandstone (Member 4) is seen to be overlying Member 3. Unfortunately, this unit has not been dated yet. The Telaga Jatoh Formation extends into north Kedah, where the rocks were previously classified as part of the basal Kubang Pasu Formation (Basir Jasin, 1995). The bottom part of the Kuan On Beds in Kampar might be a correlative of the unit (Suntharalingam, 1968). Tournaisian aged radiolaria have also been reported from cherts of the Dengkil Beds in Dengkil, Selangor (Zaiton Harun and Basir Jasin, 2003), which might be a part of the Kenny Hill Formation Wang Kelian Formation Red mudstone of the Wang Kelian Formation, probably of Visean age, extends into north Kedah. The unit might be represented by red shales of Member 5 of the Pa Samed Formation. Unfortunately, this unit also has not been dated. The Kuan On Beds of Kampar can be correlated to the Wang Kelian Formation, where the occurrence of Siphonophyllia indicates a Visean age (Suntharalingam, 1968).

15 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) It is also possible that part of the Kenny Hill Formation in Kuala Lumpur is of the same age. 6. The Devonian Carboniferous boundary and Mid-Palaeozoic paraconformity Two of the studied localities are observed to expose sequences which pass from the Late Devonian into the Early Carboniferous, i.e. Bumita Quarry, at Hutan Aji, and Kampung Guar Jentik (Fig. 11) Sanai limestone-telaga Jatoh formation boundary The boundary between the underlying Sanai Limestone and the Telaga Jatoh Formation, exposed at Kampung Guar Jentik, is abrupt, with the lithology sharply changing from limestone to light coloured, friable mudstone. The lithology then gradually changes into black mudstone and chert, before being abruptly overlain by brownish red mudstone of the Wang Kelian Formation. Conodont data indicate an Early to Mid Famennian age for the top of the Sanai Limestone, while radiolarian data from the Telaga Jatoh Formation give an Early Carboniferous (Late Tournaisian) age (Basir Jasin and Zaiton Harun, 2001). The record for the Latest Devonian and Earliest Carboniferous is absent from the Kampung Guar Jentik section. The abrupt change in lithology, sharp contact (with the uppermost limestone bed having an even and mineralized surface), and significant biostratigraphic age gap between the Sanai Limestone and the Telaga Jatoh Formation is interpreted here as a paraconformity, representing a period of non-deposition or erosion, which would explain the lack of a Late Famennian and Early Tournaisian record Chepor Formation Binjal Formation boundary The Chepor Formation is dated by fossils as Late Devonian (Frasnian Famennian) in age, while the Binjal Formation is Tournaisian in age. Therefore the Devonian Carboniferous boundary should be somewhere near the boundary of the two units. A thin black mudstone facies forms the upper boundary of the Chepor Formation. This facies is barren of benthic fossils, except for accumulations of large Posidonia shells. Ammonoids are occasionally found in the black mudstone. Black shale deposits in uppermost Famennian beds have been reported throughout the world, where they are interpreted to indicate a mass extinction during the end-famennian, called the Hangenberg Event, and is associated with a major transgressive episode, followed by a major regression, forming unconformities in numerous Devonian Carboniferous boundary sequences throughout the world (for a review of the event, see Hallam and Wignall, 1997, chapter 4). The black mudstone at the top of member CF-2 can be correlated with the Hangenberg Shale of Germany, which is slightly below the D/C boundary. Therefore, the Devonian Carboniferous boundary would be somewhere above the black mudstone facies, in the lower part of the Binjal Formation, possibly in the interval m of the Hutan Aji composite section. The sharp contact between the black mudstone facies of the Chepor Formation and the overlying red beds of the Binjal Formation is interpreted as a paraconformity representing the major regression that occurred after the Hangenberg Anoxic Event. A major stratigraphic break cutting out the latest Devonian and most of the Tournaisian is also observed in the Kanthan Limestone of north Kinta Valley, where Metcalfe (2002) reports a paraconformity based on conodont evidence. He also reports a second paraconformity of Early Visean age in the Kanthan Limestone Implications of a Mid-Palaeozoic paraconformity in northwest peninsular Malaysia A Mid-Palaeozoic orogeny has been suggested for the rock succession of the Shan-Thai/Sibumasu Terrane by numerous authors. Koopmans (1965) interpreted a Mid- Palaeozoic orogeny (Langkawi Folding Phase) based on differences in deformation, regional metamorphism and granite intrusion between the lower and upper Palaeozoic successions in northwest Peninsular Malaysia, but this interpretation was rebutted by Yancey (1975). A Devonian unconformity between Early Devonian tentaculitid shales (Unit 1, Jentik Formation, basal Upper Detrital Member), and Late Devonian-Early Carboniferous red beds in northwest Peninsular Malaysia was suggested by Jones (1973b), which was interpreted as an uplifting event (Hutchison, 1996, p. 236). Again this interpretation has proved to be erroneous (Ahmad Jantan, 1973; Yancey, 1975; Meor and Lee, 2002). The interpretation of the red beds in this paper as deeper water, outer shelf, prodelta deposits further weakens the Mid-Palaeozoic orogeny hypothesis. But the idea persists, due to the scanty distribution of Devonian aged sedimentary rocks. Wongwanich (in preparation, cited in Boucot, 2002) reports the occurrence of a possible major disconformity between Early Devonian tentaculitid shales and Namurian aged shales. Meanwhile, Bunopas (1981) and Metcalfe (1999) suggested that the regional unconformity at the Devonian Carboniferous boundary detected in the Southeast Asian terranes was caused by Devonian rifting of South China, Indochina, East Malaya and Southwest Borneo from Gondwanaland. The paraconformity near the Devonian Carboniferous boundary at the Kampung Guar Jentik and Hutan Aji sequences represents the depositional hiatus on the Sibumasu/Shan-Thai terrane during the Mid- Palaeozoic, previously suggested by Baum et al. (1970) and Metcalfe (2002). There are no observed structural differences between the sections underlying the paraconformity and the sections overlying it, implying that the depositional hiatus was not associated with tectonic movement. The possible correlation of the black mudstone facies of the Chepor Formation, which lies just below the paraconformity

16 734 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) surface, with the global Hangenberg Anoxic Event indicates that the cause of the depositional hiatus is most probably the global regression occurring near the end of the Famennian, just after the transgressive episode which marked the Hangenberg Anoxic Event (Schonlaub, 1986; Xu et al., 1986; Bai and Ning, 1988; Chlupac, 1988; Krstic et al., 1988; Ulmishek, 1988; Feist, 1990; Klemme and Ulmishek, 1991; Paproth et al., 1991; Wang et al., 1993). 7. Sea level fluctuations A generalized sea-level curve for the Middle Palaeozoic succession in northwest Peninsular Malaysia is reconstructed using sedimentological and palaeontological data presented here (Fig. 16). Several trends are observed. Comparisons are made with sea-level curves for Euramerica (Johnson et al., 1985) and Australia (Talent, 1989) Pragian Emsian transgression A major transgression occurred on the Sibumasu Terrane during the Late Pragian Early Emsian, marked by gradual vertical transition from pelagic limestone of the Mempelam Limestone to Lalang Member, deeper water tentaculitid shales. Water depth is estimated to be between 150 and 200 m. No transgressive episode during this period has been observed in Euramerica (Johnson et al., 1985). A major regressive episode was taking place in Euramerica, and sealevels remained low up to the Late Emsian. Mid-Palaeozoic sea-level records for Australia are sketchy, but a regression is recorded during the Pragian (Fig. 17), followed by a transgression from the Late Pragian to the Early Emsian (Buchan Caves Limestone transgression). A marine transgression occurred in the southern part of the South China Block, starting in the Lochkovian and persisting into the Pragian (Zhao et al., 1996). The Palaeo Tethys Ocean was forming during the Devonian, due to rifting of several terranes (Indochina, Tarim, South China Block and North China Block) from north Gondwana (Metcalfe, 1999). The Early Devonian transgressive event of the Sibumasu Terrane (marked by the Lalang Member) can be correlated to the contemporaneous transgression occurring on the southern part of the South China Block. The South China transgression is interpreted as marking the initial rifting of the terrane from Gondwana (Zhao et al., 1996), which led to opening of the Palaeo Tethys Ocean (Wu et al., 1994; Metcalfe, 1999). The Lalang Member transgression also marks this rifting, but on the side of Gondwanaland, as the Sibumasu Terrane was probably still attached to Gondwanaland during the Early Devonian (Bunopas, 1981; Sengör et al., 1988; Metcalfe, 1988, 1999, 2000) Late Famennian transgressive episode A major flooding event is marked by an abrupt transition from relatively shallow water red mudstone to a thin band of black, pyritic mudstone in the Chepor Formation. As has been discussed earlier, this probably marks the Hangenberg Event, a transgressive episode recorded worldwide, and was contemporaneous with a major extinction event (Fig. 17) Latest Famennian paraconformity A major paraconformity marks the boundary between the Mid-Famennian aged Sanai Limestone and Early Carboniferous cherts of the Telaga Jatoh Formation, exposed at Kampung Guar Jentik. The Late Famennian record is absent Fig. 16. Reconstructed sea level curves for the Middle Palaeozoic succession in northwest Peninsular Malaysia.

17 H.H. Meor, C.P. Lee / Journal of Asian Earth Sciences 24 (2005) Fig. 17. Comparison of reconstructed sea level curve for the Middle Palaeozoic succession of northwest Peninsular Malaysia with eustatic sea level curves for Euramerica (Johnson et al., 1985; Ross and Ross, 1988) and Australia (Talent, 1989). here. This same regressive episode is marked by the abrupt transition from deep water black mudstones at the top of the Chepor Formation, to shallower prodelta to delta front deposits of the Binjal Formation. The paraconformity may have been caused by the global regression occurring during the End Famennian, just below the D C boundary (praesulcata Zone), and just after the Hangenberg Event (Fig. 17) Late Tournaisian transgression Bedded chert and black shale deposition during the Late Tournaisian marks a major transgressive episode, where Late Devonian shallow water mudstone is replaced by deepwater radiolarian chert. This event correlates well with the global Burlington Cycle transgressive event (Ross and Ross, 1988) 8. Geological history The geological history of northwest Peninsular Malaysia during the Middle Palaeozoic (Silurian-Early Carboniferous) is summarized here Early Devonian Black shale deposition (Lalang Member) gradually replaced the pelagic limestone deposits of The Mempelam Limestone during the Lochkovian. This transition marks a transgressive stage during the Late Silurian to Early Devonian. The basin was already gradually deepening in the Silurian, with deepwater pelagic limestone slowly being replaced by siliciclastics. The basin was deep during the Emsian, as indicated by fauna of Benthic Assemblage 4 5 (Boucot et al., 1999), which would give a water depth of about m. Sluggish circulation (probably a result of a tropical climate) resulted in dysoxic and periodically anoxic waters. But the basin was still connected to the open sea, as evidenced by abundant pelagic dacryoconarid tentaculitids and monograptids. This deepening of the present day eastern margin of Sibumasu was tectonically controlled, indicating subsidence probably due to block faulting caused by rifting of the Indochina, Tarim, South China Block and North China Block, which initiated the formation of the Palaeo Tethys Ocean (Metcalfe, 1999). Later, possibly in the Eifelian, the basin started to be filled with thick coarse grained siliciclastics, and benthic fauna thrived, as evidenced by trace fossils in the Bukit Raja Member. This marks a regressive phase, as the Bukit Raja Member has the characteristics of a shallow water deposit Mid-Late Devonian The start of a regressive event during the Mid-Devonian is indicated by transition from basinal black shale to prodelta siliciclastic deposition during the Mid-Late Devonian. Thick mud of the Chepor Formation was being deposited on the prodelta of an offshore delta fan. The water depth of modern day prodeltas ranges from 10 to 30 m (Sutton et al., 1970), and the Devonian basin prodelta was probably similar in depth. Occasional turbidity currents transported coarser grained material onto the prodelta. The sea bottom was teeming with benthic life. The basin was