Sedimentary facies analysis and depositional model of the Palaeogene West Crocker submarine fan system, NW Borneo Abdullah Adli Zakaria a,b,⇑ , Howard D. Johnson b , Christopher A.-L. Jackson b , Felix Tongkul c a Technical Geoscience Department, Technical Services Division, PETRONAS Carigali Sdn. Bhd., Level 16, Tower 2, PETRONAS Twin Towers, KLCC, 50088 K. Lumpur, Malaysia b Department of Earth Science and Engineering, Imperial College, Prince Consort Road, London SW7 2BP, UK c Universiti Malaysia Sabah, Beg Berkunci No. 2073, 88999 Kota Kinabalu, Sabah, Malaysia article info Article history: Available online 23 May 2013 Keywords: West Crocker formation Sand-rich submarine fan Fold-thrust system Sedimentological analysis Sedimentary facies Facies associations Channel-levee Lobes Mass-transport deposits abstract This study outlines a sedimentological analysis of the Palaeogene West Crocker Formation (WCF) around the Kota Kinabalu area of SW Sabah, which represents a large submarine fan depositional system within part of what was the complex and tectonically active margin of NW Borneo. The newly acquired and often extensive outcrop data summarised in this study has resulted in a more complete synthesis of the Crocker fan depositional system than has been previously possible. Seven facies (F1–F7) have been identified which constitute three main facies groups: (1) sand-dominated facies (F1–F3), comprise high- to low- density turbidites and form the dominant part of the WCF, (2) debris flow-dominated facies (F4–F6) com- prises mud- and sand-dominant debris flows and mass transport deposits (MTD), which form a secondary but highly distinctive part of the WCF, and (3) mudstone-dominated facies (F7), represent a subordinate part of the WCF. Analysis of the vertical facies successions (from proximal to distal), has resulted in recognition of five major genetic units: (1) channel-levee complex; characterised by thick (30–60 m) thinning and fining upward facies succession, which are dominated in their lower part by thick-bedded (1–6 m), amalgam- ated high-density (Lowe-type) turbidites with rare debrite beds; the upper part is dominated low-density (Bouma-type) turbidites, without associated debrite beds. (2) Channelised lobes; characterised by 2– 10 m thick, coarsening upward, which are overlain by 5–20 m thick fining upward facies successions; these successions are dominated by high-density turbidites (c. 0.5–1 m thick) and linked co-genetic tur- bidite–debrite beds (0.1–0.5 m thick), with subordinate mudstone facies. (3) Non-channelised lobes; comprise 5–20 m thick coarsening upward facies successions; these start with mudstone facies, which pass gradually upwards into linked co-genetic turbidite–debrite beds; sandstone bed thickness increases upwards, while the debrite caps tend to become thinner upwards; high-density turbidites (2–3 m thick beds) form amalgamated units at the top of these successions. (4) Distal lobes; represented mudstone- dominated intervals with mainly thin (1–10 cm thick) low-density turbidites and occasional muddy debrites. (5) Mass transport complexes (MTCs); characterised by highly deformed slumped units (up to 2.5–5 m thick). It is inferred that the five genetic units were deposited within four proposed laterally contiguous depo- sitional environments are: (1) inner fan channel-levee complex; (2) mid-fan channelised lobes; (3) mid- fan non-channelised lobes; and (4) outer fan distal lobes. The West Crocker submarine fan is interpreted as a multiple-sourced, shelf-fed, Type II, low-efficiency, sand-rich depositional system. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The Oligocene to Early Miocene West Crocker Formation (WCF) is a major sand-dominated basin-floor fan complex that was deposited in an accretionary foredeep basin and forms part of the Crocker-Rajang fold-thrust belt, NW Sabah (Fig. 1). This sandstone-dominated succession is several kilometres thick, more than 25,000 sq. km in extent (250 km long by 100 km wide), and is exposed over a large part of the coastal ranges of NW Sabah, north- ern Borneo. Its SW–NE structural trend controls the present day shoreline orientation (Fig. 1B; Stauffer, 1967; Tongkul, 1987; Hutchison, 1996; Crevello et al., 2007). Regional palaeographic reconstructions and a provenance analysis of constituent sand- stones suggest sediment derivation from a continental source area to the south and south-west of Borneo (including the Schwaner Mountains), located ca. 400 km to the SW of the present study area 1367-9120/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jseaes.2013.05.002 ⇑ Corresponding author. E-mail address: abdulad@petronas.com.my (A.A. Zakaria). Journal of Asian Earth Sciences 76 (2013) 283–300 Contents lists available at SciVerse ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes