Facies Heterogeneity and Lobe Facies Multiscale Analysis of Deep-Marine Sand-Shale Complexity in the West Crocker Formation of Sabah Basin, NW Borneo  
[PERSON]  
1 Department of Geosciences, Universiti Teknologi PETRONAS, Seri Iskandar 32610, Malaysia;  
[EMAIL_ADDRESS] (N.A.S. ); [EMAIL_ADDRESS] (A.H.B.A.R. );  
[EMAIL_ADDRESS] (N.A.I. ); [EMAIL_ADDRESS] (M.S.B. ); [EMAIL_ADDRESS] (N.A. ); [EMAIL_ADDRESS] (M.U. ); [EMAIL_ADDRESS] (Z.C. ); gaaz.t2. geometry, internal architecture and vertical and lateral distribution [6; 7; 8]. A range of processes related to sediment transportation and accumulation control the overall depositional characteristics of deep-marine sediments. Gravity-driven flows are one of the major sediment transport processes in a submarine depositional environment [9; 10]. These flows principally encompass two endmembers: turbidity currents (frictional flow) and debris flow (cohesive flow) [9; 11; 12]. Such sedimentary processes and gravity flows result in the development of submarine fan and lobe systems. The classification of deep-marine fan and lobe deposits, with respect to sedimentary processes, requires the spatial distribution, thickness of individual units, sedimentary structures and variation in grain size [13; 14]. Deep-marine lobes are considered a vital component of submarine fans [15; 16; 17], and they are radial features with thin apexes but distribute laterally like a fan toward the distal end [18; 19]. However, the lobe deposition is more complex in terms of internal heterogeneity and the distribution of facies [20; 21; 22]. Various subenvironments (the lobe axis, off-axis, lobe fringe and distal lobe fringe) have been assigned to these lobe deposits with respect to their thicknesses and facies associations [19; 23]. The excessive input of siliciclastic sediments from a shallow marine environment result in the significant internal heterogeneity and complex distribution of sediments in deep-marine lobes [20; 21; 22; 24]. Later, because of substantial uplift and denudation, these gigantic sand deposits are exposed on the surface [25]. The study area selected for this project is present in the Malaysian part of Borneo, named Sabah, which contains extensive exposures of deep-marine fan deposits stratigraphically termed as the West Crocker Formation. In the case of our study area, with recent infrastructure development (Pan Borneo Highway construction in East Malaysia), numerous new outcrop sections were exposed as fresh roadcuts, which paved the way for the detailed analysis of facies heterogeneity and the distribution of various lobe elements in the West Crocker submarine fan. The recent literature suggests that the sedimentary facies of deep-marine deposition are significantly diverse and complex when compared with the previous classic Bouma model [26]. Late Paleogene deep-marine sediments of the West Crocker Formation along the Pan Borneo Highway in West Sabah are mainly comprised of thin to thick and massive bedded sandstones, with some siltstone and shale units [27]. Although the previous studies describe Late Paleogene sediments in terms of several components of a submarine fan based on individual outcrops [27; 28; 29; 30], this study highlights the multiscale heterogeneity to interpret the distribution of deep-marine lobe complex systems in the West Sabah Basin. The study area included five studied locations of the Crocker fan, representing the sand-shale complex in West Sabah and having a total vertical thickness of more than 300 m, principally on the roadsides from Kota Kinabalu to Telipok/Tuaran (Figure 1). The key objectives of the study included (1) analyzing the facies and facies distribution of several outcrop sections of the West Crocker Formation; (2) interpreting the differences in stacking patterns and architectural elements of the studied sections; and (3) evaluating the characteristics of various components of the submarine lobe complex.