FACIES ANALYSIS AND PALAEODEPOSITIONAL ENVIRONMENT OF THE TANJONG FORMATION IN THE KALABAKAN AREA, SOUTHEAST SABAH

Abstract

An integrated approach is adopted to study the sedimentary deposits of the well-exposed Early to Middle Miocene Tanjong Formation in the Southeastern part of Sabah. The integrated sedimentological and palynological data will provide a better insight into the depositional architecture of the area. This work presents the first detailed sedimentological facies analysis of the Tanjong Formation within the Kalabakan area. The integration of facies analysis, ichnological and palynological data provide a better evaluation of the organic matter (OM) origin and the reconstruction of the palaeodepositional model. An extensive outcrop-based sedimentological facies analysis was performed on eight (8) well-exposed outcrops with studied stratigraphic sections. Seven facies associations are classified in the Tanjong Formation from twelve lithofacies elements which have been interpreted from the fluvialdeltaic to shallow marine environment: FA1 - Floodplain facies association; FA2 – Fluvial channel facies association; FA3 - Coastal swamps facies association; FA4 – Tidal flat facies association; FA5 – Delta front facies association; FA6 – Mouth bar facies association; FA7 - Upper shoreface facies association. The palynomorphs of the studied coal samples yielded abundant mangrove and freshwater types of pollen assemblage, while the analysed mudstone samples suggest deposition within a lower coastal plain setting with proximity to the marine environment. The presence of Florschuetzia levipoli (Sonneratia caseolaris) and Florschuetzia trilobata suggest an age not older than the Early Miocene and/or younger. The reconstructed palaeodepositional environment model is essential in improving the predictability of the petroleum system mechanisms and the hydrocarbon potential for conventional petroleum exploration.Keywords: Sedimentology, facies association, fluvial-deltaic, shallow marine, geochemical, palynology