PERGAMON Journal of Asian Earth Sciences 17 (1999) 183±201 Cenozoic carbonates in Borneo: case studies from northeast Kalimantan M.E.J. Wilson a, *, J.L.C. Chambers b, 1, M.J. Evans c, 2, S.J. Moss a, 3, D.S. Nas d aSE Asia Research Group University of London, Dept of Geology, Royal Holloway, Egham, Surrey TW20 0EX, UK bLASMO Runtu Ltd, Jakarta, Indonesia cMaersk Oil Indonesia Maratua AS, Jakarta, Indonesia dGeological Research and Development Centre, Bandung, Indonesia Received 4 September 1997; received in revised form 20 July 1998; accepted 12 August 1998 Abstract Modern and Tertiary carbonate production is, and was, extensive and diverse in the seas surrounding Borneo, and mirrors the variety of carbonate depositional systems seen in SE Asia. The availability of favourable conditions for carbonate sedimentation around Borneo was related to a combination of factors, including tectonic setting, the formation of large basinal areas, dierential subsidence providing shallow marine areas, a tropical climate and a range of local factors, such as currents or limited clastic input. A detailed sedimentological and diagenetic study was undertaken of middle Eocene to Plio±Pleistocene carbonates which developed in the north Kutai Basin and the Mangkalihat Peninsula, northeast Kalimantan. Carbonate sedimentation in this area occurred in a range of depositional environments, from mixed carbonate clastic shelves, localised and transient shoals or reefs, a variety of platform top settings to deep water redeposited carbonates. An understanding of carbonate depositional environments, spatial facies relationships, and diagenesis is essential in order to develop models for these carbonates which can be used as predictive tools in the subsurface. This study also helps to evaluate tropical carbonate development in SE Asia and the evolution of sedimentary environments in Borneo during the Cenozoic. # 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction developed from more commonly studied areas, such as the Bahamas, Persian Gulf or Red Sea, which are not Cenozoic carbonates are extremely varied and wide- directly applicable. Carbonates in SE Asia are mainly spread throughout SE Asia, and those found in and produced by organisms, therefore it is important to around Borneo (Fig. 1) are no exception. These car- consider the role of the various carbonate producers bonates are rarely associated with evaporites and are and how these may have varied through time. Corals mostly formed from the skeletal remains of shallow are uncommon in Paleogene carbonates, perhaps due marine organisms. Chemical precipitates, such as to a combination of evolutionary, biogeographical and ooids, are extremely rare. In order to interpret past environmental factors, and reefal frameworks have not depositional environments a model is needed which been identi®ed for this time period in SE Asian car- compares Cenozoic carbonates in SE Asia with their bonates (Wilson and Rosen, 1998). Also, Buxton and modern regional counterparts, rather than with models Pedley (1989) noted that there may have been some down slope displacement of shallow water larger benthic foraminifera by other shallow marine biota or * Corresponding author. Tel.: 017-84443592; fax: +017-84434716; foraminifera through the Cenozoic. e-mail: [email protected]. 1 SE Asia has been an extremely active tectonic area Now at LASMO, Venezuela throughout the Cenozoic and many of the carbonate successions are syntectonic or located on basement 2 Now at Anadarko Algeria Corporation, PO Box 576, Uxbridge, Middlesex, UB8 1YH, UK highs related to earlier structures. Borneo formed the eastern margin of Sundaland, the stable cratonic mar- 3 Now at Robertson Research Pty Ltd., W. Perth, Australia, 6005 gin of SE Asia, throughout much of the Tertiary 1367-9120/99 $ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0743-9547(98)00045-2 184 M.E.J. Wilson et al. / Journal of Asian Earth Sciences 17 (1999) 183±201 Fig. 1. Simpli®ed geological map of Borneo, showing outcrops and some subcrops of Cenozoic carbonates and modern carbonate depositional systems. (Hall, 1996). Widespread basinal development occurred therefore occurred in a range of marine settings, where around the margins of Sundaland during the early conditions were suitable, over large parts of eastern Paleogene, and basins along the southeastern margin Borneo (Fig. 1), the Makassar Straits, the east Java rapidly became marine. Carbonate sedimentation Sea and western Sulawesi. M.E.J. Wilson et al. / Journal of Asian Earth Sciences 17 (1999) 183±201 185 Fig. 2. Maps showing the Tertiary carbonate depositional environments studied in the north Kutai Basin and on the Mangkalihat Peninsula. 186 M.E.J. Wilson et al. / Journal of Asian Earth Sciences 17 (1999) 183±201 Table 1 Summary of carbonate outcrops, their ages, constituent components and depositional environments in Borneo. The reader is referred to the prin- cipal references for more information Formation Name Location Age Depositional setting Lithologies Biota Principal references Terumbu Limestone Oshore NE Miocene Isolated carbonate Grainstones, Corals, coralline May and Eyles, 1985; (TL) Natuna platforms and packstones, algae and some Rudolph and Lehmann, buildups mudstones and foraminifera 1989; Dunn et al., 1996 rudstones Luconia (LS) Luconia, Middle Carbonate buildups Mudstones, Corals, larger Epting, 1980 oshore Miocene on faulted highs. wackestones, benthic foraminifera Sarawak Four growth phases, framestones, and coralline algae some protected rudstones areas Melinau Limestone Sarawak Late Eocene Carbonate platform, Packstones, Larger benthic Adams, 1965 (ML) (Tb) to early some marginal grainstones, some foraminifera Miocene (Te) deposits, coral patch redeposited beds. dominate reef only noted in Some dolomitization Miocene Batu Gading (BG) Sarawak Late Eocene Platform or shoal Packstones, Larger benthic Adams and Haak, (Tb) and late deposits (Tb) wackestones and foraminifera 1962; Adams, 1965; Oligocene karsti®ed and limestone breccias dominate Abdullah and Yaw, (Te1-4)/early overlain by (Te1-4) 1993 Miocene? redeposited facies (Te) (Te1-4) Keramit (KR) and Sarawak Late Eocene Probably slope or Marls and breccias Planktonic Adams, 1965 Selidong (SL) (Tb) some basinal deposits of foraminifera and Limestones reworked and Melinau Limestone larger benthic late (ML) foraminifera Oligocene (Te1-4)/early Miocene (Te) Bukit Sarang Sarawak Oligocene Shallow marine Probably packstones Larger benthic Adams, 1964, 1965 Limestone (S) (Tc) shelf foraminifera Tujoh-Siman Sarawak Palaeocene to Deep marine (Ta) Wackestones and Planktonic Adams, 1965 Limestone (TS) early Eocene and some conglomerates foraminifera and (Ta) and late conglomerates (Te) radiolaria in Ta Oligocene deposits and larger (Te1-4)/early benthic foraminifera Miocene (Te) and some corals Subis (SB) and Sarawak Early Not given Not described Larger benthic Adams, 1965 Bekuyat (BY) Miocene foraminifera Limestones (Te5) Balambangan/ Oshore west Late Miocene Shallow marine and Sandy limestone Foraminifera, Ali, 1992 Tigapapan Sabah to Plio± some redeposited coralline algae, Limestone (BT) Pleistocene carbonate on echinoids dominantly clastic shelf Gomantong/ Sabah Late Shallow marine Framestones, Abundant larger Adams, 1970; Noad, Kinabatangan Oligocene to shelf, some clastic rudstones, benthic foraminifera 1996 Limestone (GL) early input packstones and and corals and Miocene (Te) mudstones coralline algae Minor limestone in Sabah Middle Isolated and Not given Not given Heng, 1985 Sebahat Formation Miocene± transient localised (SB) Pliocene carbonates in clastic successions M.E.J. Wilson et al. / Journal of Asian Earth Sciences 17 (1999) 183±201 187 Minor limestone in Sabah Oligocene to Isolated and Not given Not given Heng, 1985 Labang/Tanjong middle transient localised Formations (LT) Miocene carbonates in clastic successions Vanda Limestone Oshore Pliocene Delta front or shelf Framestones, Corals dominate Netherwood and Wight, (V) Tarakan edge shallow marine ¯oatstones, and larger benthic 1992 basin, NE carbonates framestones, some foraminifera and Kalimantan argillaceous some coralline algae and Halimeda Seilor (SO) and Mangkalihat Late Eocene Extensive carbonate Framestones, Larger benthic Suessli, 1976; Buchan et Taballar (TB), Peninsula (Tb) to Mio± platform and some rudstones, foraminifera al., 1971; Achmad and Tende Hantu (TH) and Maratua Pliocene isolated buildups, packstones, dominate much of Samuel, 1984; Wilson, and Domaring ridge reworking along grainstones, platform, also corals this paper (DM) Formations margin wackestones and and coralline algae. some dolomites Corals common on margins in Oligo± Miocene Kedango/Lebak N Kutai Late Eocene Carbonate platforms Packstones, Larger benthic This paper Limestone (KO) margin, E (Tb) to early and surrounding wackestones, foraminifera Kalimantan Miocene slope and deeper rudstones dominate and some (Te5) water facies conglomerates and corals marls Ritan Limestone N Kutai Late Eocene Isolated Packstones, Larger benthic Moss, 1994; Moss et member (RT) and margin, E (Tb) foraminiferal shoals grainstones and foraminifera al., 1997 limestone in Batu Kalimantan wackestones dominate Kelau Formation Bebulu/Dian East Oligocene to Delta front or shelf Framestones, Corals dominate Alam et al., this Carbonates (BB) Kalimantan late Miocene edge shallow marine ¯oatstones, and larger benthic volume; Roberts and and in carbonates framestones, some foraminifera and Sydow, 1996a