ELSEVIER Palaeogeography, Palaeoclimatology, Palaeoecology 145 (1999) 303±337 Cenozoic palaeogeographic evolution of Sulawesi and Borneo Moyra E.J. Wilson Ł, Steve J. Moss 1 SE Asia Research Group, Department of Geology, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK Received 30 September 1997; revised version received 1 July 1998; accepted 6 July 1998 Abstract Sulawesi and Borneo are located in the middle of the Indonesian Archipelago, an area which has been extremely tectonically active throughout the Cenozoic. This paper compiles current knowledge on the geology and palaeogeography of this complex region and includes the ®rst attempt to synthesise palaeogeographic data onto plate tectonic reconstructions. Construction of palaeogeographic maps helped to identify some of the strengths and weaknesses of current plate tectonic models for the region, thereby highlighting areas where further geological research is required. Palaeogeographic maps presented, using plate tectonic reconstructions as a base, illustrate the evolution of Borneo and Sulawesi and highlight important changes in the environment during the Cenozoic. The Tertiary geological history of eastern Borneo and Sulawesi is inextricably linked to the progressive accretion of continental and oceanic material from the east, onto the eastern margin of Sundaland, and to the resultant development of volcanic arcs. Large tracts of western Sulawesi, eastern Borneo, the East Java Sea and the Makassar Straits formed an extensive basinal area throughout much of the Tertiary. Implications for plate tectonics, exploration for natural resources and biogeography are discussed from the palaeogeographic reconstructions of Sulawesi and Borneo. 1999 Elsevier Science B.V. All rights reserved. Keywords: palaeoenvironments; palaeogeography; tectonics; Cenozoic; Southeast Asia; biogeography; resources 1. Introduction neo are frontier exploration provinces for many nat- ural resources, such as hydrocarbons, minerals, coal, The islands of Borneo and Sulawesi lie in the material for use in the construction, agricultural or midst of an extremely complex tectonic region where pharmaceutical industries. A knowledge of the re- three major plates; the Indo-Australian, Philippine- gional variations in palaeogeography through time, Paci®c and Asian plates interact and collide (Fig. 1). when combined with information such as strati- The areas between these major plates is a compos- graphic thicknesses or nature of volcanism may ite domain of smaller microcontinental and oceanic provide a useful tool for the exploration of these fragments and a region where volcanism has been natural resources. An understanding of the evolution common throughout the Tertiary. Sulawesi and Bor- of this region is also of critical importance to bio- geographers, since Wallace's original faunal divide runs between the two islands, and is now taken to Ł Corresponding author. Tel.: C44-17844-43592; Fax: C44- 17844-34716; E-mail: [email protected] represent the eastern boundary of Asiatic biota. 1 Present address: Robertsons Research Australia Pty Ltd., 69 A range of geological information suggests that Outram Street, West Perth, W.A. 6005, Australia. large areas of Kalimantan and western Sulawesi had 0031-0182/99/$ ± see front matter c 1999 Elsevier Science B.V. All rights reserved. PII: S0031-0182(98)00127-8 304 M.E.J. Wilson, S.J. Moss / Palaeogeography, Palaeoclimatology, Palaeoecology 145 (1999) 303±337 Fig. 1. Regional tectonic setting of Sulawesi and Borneo and the distribution of pre-Mesozoic cratonic areas and Tertiary basinal area in Sulawesi and Borneo. Modi®ed after Hamilton (1979), Hutchison (1989), Daly et al. (1991), Parkinson (1991), Van de Weerd and Armin (1992) and Hall (1996). M.E.J. Wilson, S.J. Moss / Palaeogeography, Palaeoclimatology, Palaeoecology 145 (1999) 303±337 305 been juxtaposed and attached to southwestern Bor- thought to delineate regions of Asiatic and Aus- neo, part of the eastern margin of Sundaland, ªthe tralian ¯ora and fauna, runs through the Makassar stable core of SE Asiaº, by the Late Cretaceous Straits between the two islands and also between (Metcalfe, 1996). Tertiary subduction of the Indian Bali and Lombok. This original faunal divide is Ocean, Philippine Sea and Molucca Sea plates was now taken as the western boundary of Wallacea responsible for the progressive collision, accretion (Dickerson, 1928), which is best described as a bio- and assimilation of fragments of continental and geographic region with a high degree of endemism oceanic crust along the eastern margin of Sunda- situated between areas with Asiatic and Australian land. Around the eastern and southern margins of ¯oras and faunas (George, 1981; Whitten et al., Sundaland, within this overall compressional, sub- 1987). The Makassar Straits appears to have been a duction-related regime, various extensional episodes barrier to dispersal for many groups of animals, al- have resulted in the formation of extensive sedi- though the clear faunal contrast (Earl of Cranbrook, mentary basins and in some cases, marginal oceanic 1981; Briggs, 1987; Musser, 1987) is not re¯ected to basins developed (the South China, Sulu and Celebes the same extent by the ¯ora (George, 1981; Van Bal- seas; Fig. 1). gooy, 1987). Regional plate tectonic changes have During the last twenty years several Tertiary plate been related to biogeography by a number of au- tectonic reconstructions have been developed for thors (Audley-Charles et al., 1981; Audley-Charles, Southeast Asia (Carey, 1975; Hamilton, 1979; Ran- 1981, 1987; Burrett et al., 1991; Hall, 1998). This gin et al., 1990; Daly et al., 1991; Lee and Lawver, work concentrates on Borneo and Sulawesi and sum- 1994, 1995; Hall, 1996). There is now a growing marizes how the Cenozoic plate tectonic variations consensus over some of the main points of the plate and the changes in palaeoenvironment may have tectonic evolution of the area, although detailed el- affected past migrations=dispersals. A detailed dis- ements of the reconstructions and the mechanisms cussion of this topic can be found in Moss and driving plate tectonics are still under dispute. Com- Wilson (1998). paring local palaeogeographic information with re- The future potential economic growth of South- gional reconstructions is one way to test the validity east Asia is in part dependent on utilising its wealth of these reconstructions by highlighting matches or of natural resources. Borneo and Sulawesi are both discrepancies in the inferred tectonic setting and dis- areas of proven coal, hydrocarbon, minerals and tribution of depositional environments. However, un- building material accumulations and considerable til now for Borneo and Sulawesi, palaeogeographic effort is being put into exploration for further dis- reconstructions have only been drawn on a local coveries. The location and amounts of these natural scale and rarely within a plate tectonic context. Al- resources depends on the geological evolution of the though we are limited by the incomplete nature of area and the past distribution of environments, re- the geological record or by imperfections in our sulting in the formation of certain rock types and the knowledge of the geology, for areas where data are economic accumulation of natural resources. There- good a reliable test can be made. The ®rst and often fore constructing palaeogeographic maps is a useful most critical step in plate tectonic reconstructions is tool for furthering the exploration of natural re- to delimit which areas formed plate boundaries and sources, and particularly in the hydrocarbon industry to evaluate how the nature of these plate margins this method is routinely used. varied through time. A study of facies variations can help to evaluate discontinuities or possible connec- tions between regions. Comparing palaeogeographic 2. Data sources, quality and methodology data with plate tectonic reconstructions also high- lights gaps in the geological data base and suggests The bases for the plate tectonic template used key areas for future research. in this paper are the recent reconstructions of Hall Borneo and Sulawesi are of prime importance to (1996) which incorporate new data from eastern In- biogeography and palaeobiogeography of Southeast donesia to help constrain the motion of the Philippine Asia. The faunal divide of Wallace (1863), originally Sea Plate (Hall et al., 1995). Many reconstructions of 306 M.E.J. Wilson, S.J. Moss / Palaeogeography, Palaeoclimatology, Palaeoecology 145 (1999) 303±337 the region imply major strike-slip faulting following et al., 1990; Fuller et al., 1991, 1999; Sunyata and India's collision with the Eurasian margin (Peltzer Wahyono, 1991; Moss et al., 1997) for southern and Tapponnier, 1988; Rangin et al., 1990; Daly et Borneo and the South Arm of Sulawesi for the Ter- al., 1991; Lee and Lawver, 1994, 1995). The Indian tiary. Since different timing and amounts of rotation collision is seen in all these reconstructions as the would have affected the evolution and accretion of major driving force controlling Tertiary tectonics of material forming eastern Sulawesi and the nature Southeast Asia. The reconstruction of Hall (1996) of the change between northern mainland Borneo still recognizes the important in¯uence of major and the South China Sea, the 45ë counterclockwise strike-slip faulting in Southeast Asia (with displace- rotation of Hall (1996) remains in the palaeogeo- ments of about 500 km, after Briais et al., 1993). graphic reconstructions