AAPG II/fertli/fumal Cu4ermc( d EYhibifum '94 AJ/g/l.lf21-24, 1994, KJ/ala Lumpur, Maltzy"iLl The Paleogene basins of Sabah, East Malaysia F. TONGKUL Earth Science Department Universiti Kebangsaan Malaysia, Sabah Campus Locked Bag No. 62, 88996 Kota Kinabalu, Sabah, Malaysia Abstract: The Paleogene basins of Sabah developed in two stages, represented by early and late Paleogene sediments, in association with NW-SE compressional deformation during the late Mesozoic and Middle Eocene. The earlier deformation produced a wide elongate basin trending NE-SW bordered by a continental block to the NW and an emergent oceanic basement to the SE. The basin became the depositional sites of shallow to deep water early Paleogene sediments. The later deformation divided the earlier basin into two parallel basins (Outer and Inner basins) also trending NE-SW. Both basins were independently filled by shallow to deep water late Paleogene sediments derived axially from the southwest and laterally from the northwest and southeast. These basins were finally closed during the early Miocene resulting in the Paleogene fold-thrust belt of Sabah. INTRODUCTION Sea oceanic crust in the SE (Fig. 1). The sediments covers most of western, northern and central Sabah The Paleogene basins of Sabah here refers to while in eastern Sabah the sediments are not clearly the depositional sites of thick Paleogene sediments mapped out due to the presence of extensive melange forming the mountainous belt of Sabah. Unlike deposits (Fig. 2). The Paleogene sediments continue most of the younger basins, the configuration of the southward onland into Sarawak and NE Paleogene basins were not preserved but greatly Kalimantan (Hamilton, 1979; Hutchison, 1989) and modified by compressional tectonics. The Paleogene northeastward offshore into Palawan (Rangin, sediments are characterised by severe folding and 1989). Paleogene sediments trending NE-SW thrusting. In western and southwestern Sabah the underlie much of the Neogene basins offshore sediments were mostly deposited by turbidity northwest Sabah (Bol and Hoorn, 1980; Hinz et al., currents and mass flows, and a northeast 1989). The continuation eastward offshore Sabah depositional direction has been established is still uncertain but is also thoughf to underlie (Stauffer, 1967; Tongkul, 1987). The elongate basin most of the Neogene sediments here. so-formed has been, informally referred to as the Rajang Basin or Crocker basin (Hamilton, 1979; STRATIGRAPHY Tongkul, 1987; Rangin, 1989; Hutchison, 1989). Detailed sedimentological, paleontological and The stratigraphy of Sabah, based on present structural informations on the sediments are still age determinations, is at best a general one (Fig. lacking in parts of western, northern, eastern and 3). The Paleogene sediments rest unconformably central Sabah. Therefore the overall nature and on Mesozoic oceanic crusts and overlain extent of the Paleogene basin is still unknown: unconformably by Neogene melange, pyroclastic and This paper presents additional information on clastic deposits. The precise age determination of the Paleogene sediments and proposes a model on most of the Paleogene sediments is still problematic the development of the Paleogene basins. due to lack of good fossil indicators. Therefore the relationship between some formations is still REGIONAL GEOLOGICAL SETTING uncertain and the tendency to lump them together is understandable. This, however, is not helpful in The Paleogene sediments form part of the NW understanding the depositional history of the Borneo subduction complex of Haile (1973) and sediments, because it is clear that the sediments Hamilton (1979) accreted during the Late Tertiary. were not deposited together as indicated by common These accreted sediments are bounded by the rifted facies variations within the sediments. southern continental margin of China presently Based on age differences, the Paleogene occupied by the Reed and Dangerous Grounds sediments can be broadly grouped into early and carbonate platforms in the NW and the Celebes late Paleogene deposits. The early Paleogene Ceo!. Soc. Malay.,ia, Bulletin 37, July 1995; pp. 301-308 c.v o I\) f- 1050 1100~:;:I EmI§ PRE-TERTIARY E§fE§ CONTINENTAL CRUST I:·:·:"::·:·' TERRANE ACCRETED 15 0 .. : ::. SINCE LATE CRET. INDOCHINA ACCRETED OR c=J EXTENDED CRUST BELOW SEA LEVEL 10 :n CONTINENTAL MARGIN rTml dz G> WJJ OF SOUTH CHINA . A I C I r- I \ \ ~ OCEANIC CRUST SUNDA \ 50 '- SHELF \ ( SUBDUCTION ZONES '\) !f;~ FOLD BELT 1/ , Sources: Hamilto!", 1979; Taylor &. Hayes, I 1050 1983; Hmz et.al., 1989; Hmz et.aL, II 1991. ttJ ;:: "- ~ ~S· ~----------------------------------------------------------------------------------------~ 1...1 Figure 1. Regional geological setting of Sabah. '1 116' liS' liS' Quarternary Alluvium If Lineaments Neogene-Quart. Igneous if/ Strike-Slip Fault RocJ<s Mid. Miocene Pyroclastics 7 7' .:x Synclinal Axis ~ Anticlinal Axis r:.:;~;] Mid. Miocene Melange /. Thrust Fault SULU SEA Neogene Sediments / Paleo flow Late Paleogene Sediments --l ::I: Early Paleogene Sediments m SOUTH CHINA SEA -C l> Mesozoic Ophiolitic .-m 0 Basement G) 6 m z 6' m tD ~ Z rn 0 "TI en l> tD l> _::I: m l> ~ s:: l> S rn» s' s' CELEBES SEA Sources : Wilford, 1967; Yin, 1986; Tongkul. 1990. SARAWAK Lineaments and faults based on Landsat images and SAR imageries interpretations. 19' Figure 2. Geological and structural map of Sabah. w ow . SOUTHWEST WEST & NORTH CENTRAL EAST SABAH SABAH SABAH SABAH PLIOCENE ~ ~. ,:, •.A LITHOLOGY Z ... : : :. '.: Go'7:-' ~.. t)~~ ·Sk~ .•~ ~ .... " ....... ."{:J:'.~ .. ... L ~ ....... ......... Sb~ ..... ~-~ ·······By~ "O Q • .... .. 0 t-- • .... J. ... Ii" Mudstone ~Kp~:':K~-=:, ~Tk ..To Kg~ 0 •..• :;;..-·c _ ili MIOCENE M .•-: 4~~ ~ t-- -=- --Se-- --=- -iif.Tifi.:~;::";· ...... Z E - - - -- .: ........~-;.& Sandstone '~ -:-.. ~.:- -;." UL~ ......... .. .... "''''6::I::: •••• - -~Me: .... .. ..!....!.~ PL <>'" OLIGOCENE :-:- Ks .. ~:.. Lb-'-'-' Conglomerate ~ :Tx-~WCr' 00 Z ..... -(' ..... " ~ L _ > ..... !::=>.~ LL TLB r--, .• Limestone 0 I- fuSCr:~"" BL EOCENE ?. ;~ TL 0 M PBL~"?~ Pyroclastics ~ I- :-n ~ E c; ~ECr~ z Melange G> ~ ;><; PALEOCENE KL :p" ....••..•. Cr Chert I LATE ~~ ~o Basalt ~~ EARLY UU Ultrabasic 111111111111111 I Metamorphic ~~ Cb I- FORMATIONS: Be-Belait, Me-Meligan, Se-Setap, Tx-Temburong, WCr-WestCrocker, SCr-South Crocker, NCr-North Crocker, ECr-East Crocker, By-Bongaya, Sb-South Banggi, Wr-Wariu, Kd-Kudat, Tr-Trusmadi, Um-Umas Umas, Kp-Kapilit, Tj-Tanjong, Kb-Kalabakan, Km-Kuamut, Ks-Kulapis, Lb-Labang, Sp-Sapulut, Cs-Chert-Spilite, Sk-Sandakan, Gn-Ganduman, Sb-Sebahat, Ay-Ayer, Gr-Garinono, Kg-Kalumpang, Tu-Tungku, Cb-Crystalline Basement LIMESTONES: lJL.U\u Lakutan, KL-Kalampunian, DL-Dampirit, SL-Suangpai, LWL-Liwagu, ML-Maringan, BPL-Batu Puteh, TLB-Telupid, BL-Banggi, LL-Lian, BRB-Bayayo, RLB-Rompun, PL-Punggul, PBL-Pun Batu, GL-Gomantong, LBB-Langusan, TL-Tingkayu, TLL­ Larei Larei. CONGLOMERATES: MC-Malubuk, SC-Sensiang; BC-Bidu-Bidu. SOURCES: Clennell, 1992; Jumit, 1992; Basir, 1991; Tating, 1991; Rangin et al., 1990; Tongku~ 1990; Lai, 1989: Basir & Se1varajah, 1988; James, 1984; Langai, 1983; Lasimbang, 1983; Leong, 1974; Newton-Smith, 1967; Collenetle, 1965 & 1958;Wilson & Wong, 1964;Wilson, 1960; Fitch, \958; Stephen, 1956. Figure 3. Generalised stratigraphy of Sabah. THE PALEOGENE BASINS OF SABAH, EAST MALAYSIA 305 sediments ranges in age from Late Cretaceous to STRUCTURE Early Eocene and includes formations such as the Sapulut, Trusmadi and East Crocker. The The Paleogene sediments which are commonly sediments assigned to the upper parts of the Chert­ folded and thrust-faulted exibits complex structural Spilite Formation has also been included here. The trends as a result of several episodes of deformation late Paleogene sediments ranges in age from Middle (Fig. 2). The major structural trend is shown by Eocene to Early Miocene and includes formation the sharp bend from NE-SW to NW -SE near Kota like the Temburong, Meligan, South Crocker, West Belud. The exact timing of bending is uncertain, Crocker, North Crocker, Kudat, Kulapis and Labang. but has been interpreted to have occurred sometimes during the Early Miocene (Tongkul, 1990, 1991, SEDIMENTOLOGY 1994). The bending has been related to the change in opening direction of the South China Sea basin The early Paleogene sediments consists mostly from NE-SW to N-S during this time (Taylor and of interbedded sandstones and mudstones deposited Hayes, 1983). Prior to the Early Miocene in deep water environments. Local occurrences of deformation, the sediments were deformed and limestones (Fitch, 1958; Collenette, 1965) and uplifted. The exact timing of deformation is also conglomerates (Newton-Smith, 1967; Leong, 1974) uncertain but is interpreted to have occurred suggests shallow water environments. The overall sometimes during the Middle Eocene (Tan & Lamy, depositional direction of the sediments is unclear 1990). This is indicated by the presence of an due to the scarcity of paleoflow indicators. The unconformity between the early and late Paleogene East Crocker sediments were derived from the south sediments in southwest Sabah. The early Paleogene and SE (Khor, 1994; Cheing, 1994). The occurrence sediments also experienced more intense of conglomerate in the Sapulut Formation deformation - some showing refolded folds and (Collenette, 1965) indicates a local source towards low grade regional metamorphisms (Langai, 1983; the SE. The thickness of the sediments is still James, 1984;