Cyclicity of Sedimentary Facies, Process Controls and Gravity Flow Deposits in West Crocker Formation, NW Sabah, Borneo

Abstract

Summary The West Crocker Formation of Oligocene age, exposes gravity flow deposits ranging from turbidity currents to debris flows, mixed flows in high dipping beds in thirteen exposures along depositional strike. This study focuses on defining the vertical facies association, their cyclicity and lateral facies spread of a sand rich, gravity flow deposits. Sedimentary facies association includes a primary sand rich facies, by high density turbidity currents. Subordinate presence of fine grained, current ripple laminated, thin sandstones, heterolithics, formed by low density turbidity currents also observed. Debris flow facies include sand rich, mud rich and mass transport complexes in rare presence. Subordinate hemipelagic mudstones, linked debrites and sand clastic injections in a muddy debrite are observed. Primary depositional facies include shallow channel and channelized lobes, non-channelized lobes, deep channel fill, distal lobes, major slump and mass transport processes. Vertical facies associations show a vertical cyclicity of channelized lobe with non-channelized lobes, both overlain by hemipelagic mudstones or channel levee facies in between. A distal lobe facies, debrite facies and slump facies are minor in occurence. The intimate vertical association of channelized lobe facies with non-channelized lobe facies is indicative of a sand rich, mid fan association.