West Crocker Formation Research Articles

Sedimentological Analysis of Thin-Bedded Sequence of Eastern Part of West Crocker Formation, Northwest Sabah, Malaysia

Sedimentological Analysis of Thin-Bedded Sequence of Eastern Part of West Crocker Formation, Northwest Sabah, Malaysia

Sedimentological Analysis of the Turbidite Sequence in the Northern Part of the West Crocker Formation, Northwest Sabah

Gravity-flow deposits form the northern part of the Crocker Formation (Oligocene–Early Miocene), with the most significant interpretation as a sand-rich system in the proximal and a mud-rich system in the distal area of the deep-water turbidite depositional setting. Seven outcrop localities in the northern-part area were selected for mapping and sampling, starting from Kota Kinabalu up to the Telipok area to evaluate the sedimentary sequence. This study used mapping, field observation, and log sketches in the field, as well as extensive analysis and interpretation of sedimentological methods to investigate the sequence of sediment outcrops in the Crocker Formation area of northwest Sabah. During the fieldwork, five main facies were found, namely, massive sandstone facies (f1), graded sandstone facies (f2), laminated sandstone facies (f3), interbedded sandstone and mudstone facies (f4), and mudstone facies (f5). These northern-part outcrops are interpreted as being deposited from the highest to the lowest turbidity currents and the actuality of pelagic mudstone deposition, based on their fining-coarsening-upward pattern. The five geometrical bodies were proposed as laterally contiguous depositional environments, namely, (1) inner fan channel, (2) inner fan channel–levee complex, (3) mid-fan channelized lobes, (4) non-channelized lobes/distal lobes, and (5) basin plains. The facies interpretation shows that the study area consists of lobes, channel–levee complexes, and levees formed in a fan of a deep-water basin setting, with the basinal plain enveloped by thick mudstone deposits. This northern part of the Crocker Formation is interpreted as a multiple-sourced sediment, shelf-fed, Type II, low-efficiency, and sand-rich turbidite depositional system.

Insights on deepwater turbidite sedimentary features from outcrops in onshore Northwest Sabah, Malaysia

This paper discusses findings of sedimentary features observed from deepwater outcrops in Northwest Sabah. The observations were based on 7 outcrop localities of Lower Oligocene – Upper Oligocene sections around Klias and Kudat Peninsulas, and Kota Kinabalu, covering Temburong, Belait, West Crocker, and Kudat formations. Temburong Formation (Lower Oligocene-Lower Miocene) was observed at Menumbok (Stop 1) and Tanjung Aru (Stop 2). It comprises interbedded shale and sandstone turbidite sequence representing deposition in deepwater setting. At Batu Luang (Stop 3) the deepwater turbidite Temburong Formation is observed overlain unconformably by stacked fluvial channel deposits of Belait Formation (Middle to Upper Miocene). Here, the overlying fluvial deposits comprise predominantly conglomerates which are believed to represent basal Belait Formation lies over regional unconformable surface correlatatable to Deep Regional Unconformity (DRU). Deepwater West Crocker Formation (Lower Oligocene-Lower Miocene) was observed at King Fisher-Sulaman, Kota Kinabalu (Stop 4), composed of predominantly thick sandstone interbedded with shale. Meanwhile, Sikuati Member of the Kudat Formation (Lower Miocene) was observed at Pantai Sikuati (Stop 5) and Bukit ‘V’ (Stop 6) outcrops. It consists of interbedded sandstone and shale of turbidite successions. At Tanjung Simpang Mengayau (Stop 7) thick sandstone interbedded with thin shales of Kudat Formation was observed. In general, the Temburong Formation at Stops 1 and 2 show Bouma sequence of Ta-Tb-Te successions, but relatively thicker Te at Stop 1 suggesting a prolonged mud suspension deposit compared to Stop 2. At Stop 3, the deepwater Temburong Formation was subjected to a substantial tectonic uplift and massive erosion associated with DRU. Further northwards at Stop 4 West Crocker Formation exhibits thicker Ta successions which implies deposition within a slightly higher energy regime as compared to that of Temburong Formation at Stop 3. Meanwhile, at Stops 5 and 6 different depositional energy levels are shown in the lower and upper stratigraphic intervals. In the lower interval deposition took place within a higher energy condition as shown by thick Ta. It was followed by gradual decreasing depositional energy regime in the upper interval as shown by predominance Tc-Td-Te. Meanwhile, at Stop 7 a thick massive graded sandstone overlain by thin mudstone bed was observed which implies a prolonged Ta succession followed by short-term Te of mud suspension deposits.

Aseismic and seismic impact on development of soft-sediment deformation structures in deep-marine sand-shaly Crocker fan in Sabah, NW Borneo

Soft-sediment deformation structures are present within the deep-marine fan of the West Crocker Formation, Sabah Basin, NW Borneo. Focus of this study is to highlight the impact of seismic and aseismic activities on the development of these structures and their distribution in deep-marine fan. Twenty-nine types of deformation structures were identified during the study of twelve exposed sections. These structures were grouped into five categories: i) water-escape structures, ii) sole marks, iii) clastic intrusions, iv) deformed laminations, and v) syn-depositional brittle and ductile deformation structures. The sediment deformation is interpreted to be caused either by aseismic processes like slope failure, gravity collapse, sediment overloading, density gradient, seismic induced mechanisms such as earthquakes, tectonic uplift, or combined effect of seismic and aseismic events. These structures are classified based on type of features developed during semi-consolidated phase of rock deposition. The seismite structures i.e., clastic intrusions, deformed laminations, and syn-depositional structures are correlated with active collisional tectonics during the Late Paleogene times in the Sabah Basin. In the present work, a generalized conceptual model has also been proposed for the development of soft-sediment deformation structures in a submarine fan environment. Dewatering structurers and rapid sedimentation features are associated with inner fan, load and flame structures are present within middle fan, while contorted layers, slumps and mass-transport deposits are linked with distal fan settings.

Facies Heterogeneity and Lobe Facies Multiscale Analysis of Deep-Marine Sand-Shale Complexity in the West Crocker Formation of Sabah Basin, NW Borneo

Deepwater lobes constitute a significant volume of submarine fans and are primarily believed to exhibit a simple sheet geometry. However, recent studies interpret the geometries of these deep-marine lobes as distinct with respect to the complexity of the facies and their distribution. Hence, a conceptual model of deep-marine sediments is essential to discuss the deep-marine sediments associated with the fan and lobe architecture. The present study highlights the facies heterogeneity and distribution of various lobe elements at a multiscale level by considering a case study of the West Crocker Formation of Sabah in northwest Borneo. The formation was logged on a bed-to-bed scale from recently well-exposed sections, with a total vertical thickness of more than 300 m. The lithological characteristics, bed geometry, sedimentary textures and structures of individual beds were used to categorize the rock units into nine sedimentary lithofacies: five sandstone lithofacies (S1–S5), one hybrid bed facies (H), two siltstone facies (Si1 and Si2) and one shale or mudstone facies (M). These facies were grouped into four facies associations (FA1–FA4), which were interpreted as lobe axis (FA1), lobe off-axis (FA2), lobe fringe (FA3) and distal fringe to interlobe (FA4) facies associations. This study is applicable for the distribution of lobes and their subseismic, multiscale complexities to characterize the potential of hydrocarbon intervals in deep-marine sand-shale system around the globe.

Deep-Sea Trace Fossils In The West Crocker Formation, Sabah (Malaysia), And Their Palaeoenvironmental Significance

In the “flysch” series of the West Crocker Formation (Eocene–Oligocene), Kota Kinabalu, Sabah, trace fossils are fairly common although not ubiquitous. The trace fossils commonly occur as hypichnial semi- or full-reliefs on the sole of thin turbiditic sandstone beds (mainly Bouma Tc division) in the thinly bedded heterolithic sandstone-mudstone facies interpreted as submarine fan lobe deposits. Their presence in mainly the thinly bedded facies of the fan system suggests preferential production and preservation in the fine-grained “distal” parts of the Crocker submarine fan system. Trace fossil assemblages characteristic of the Nereites ichnofacies indicate sedimentary environments mainly in bathyal to abyssal water depths (>2000 m). This ichnofacies is dominated by horizontal grazing, farming and feeding traces, ranging from solitary to branching tubular burrows (Ophiomorpha, Palaeophycus and Planolites) to meandering trails and tunnels (Nereites, Cosmorhaphe, Helminthopsis), as well as the spiriform burrows Spirophycus. Graphoglyptids are the most diagnostic of the Nereites ichnofacies, produced by sediment grazers and farmers (agrichnia) and often displaying intricate networks of mainly horizontal tunnels preserved as hypichnial semi-reliefs. They include the delicate spiral traces of Spirorhaphe, as well as the enigmatic hexagonal network burrow Paleodictyon. Other ichnogenera include Planolites, Thalassinoides and Ophiomorpha which are facies-crossing and not environment specific. Detailed observations of the trace fossil assemblages and the degree of bioturbation enabled different sub-ichnofacies of the Nereites ichnofacies to be distinguished. Ophiomorpha is more common in sandy “proximal” facies and tend to penetrate deeply into pre-existing turbidite beds, its presence suggests a well-oxygenated newly deposited turbidite substrate, probably in the axial region of the fan lobes. Hence, channel axis and proximal fan deposits tend to be dominated by the Ophiomorpha rudis sub-ichnofacies. The Paleodictyon sub-ichnofacies is more typical of the lower energy lobe/fan fringe subenvironments. Proximal but off-axis areas are characterized by a mixture of the Ophiomorpha rudis and Paleodictyon sub-ichnofacies.

Hydrocarbon source potential of Eocene-Miocene sequence of Western Sabah, Malaysia

An evaluation of the petroleum generating potential of onshore Eocene-Miocene sequences of Western Sabah, Malaysia was performed based on organic petrological and geochemical methods. The sequences analysed are the Belait, Meligan, Temburong and West Crocker formations of western Sabah. The Belait Formation which is Stage IV equivalent in the offshore represents one of the major source rock/reservoirs of the petroleum-bearing Sabah Basin. The Eocene-Early Miocene West Crocker and Temburong formations are deepwater turbidites whilst the Miocene Meligan and Belait formations are shallow marine fluvio-deltaic deposits. The vitrinite reflectance and pyrolysis Tmax values show that the Belait samples are generally immature for hydrocarbon generation, whereas the Meligan, Temburong and West Crocker samples are in the mature to late maturity stage of hydrocarbon generation. The overall bulk source rock properties of the Belait and Meligan show fair to good petroleum source rock potential with TOC more than 1 wt %, hydrocarbon yield in the range of 400–1300 ppm and moderately high HI for many of the samples. Most of the samples representing the Temburong and West Crocker formations have TOC less than 1 wt% and have no to fair hydrocarbon generating potential. Interestingly, the samples collected in the West Crocker Formation characterized by slump deposits (MTD) have TOC>2 and possess good to excellent hydrocarbon generating potential. The organic matter present in all of the studied formations is mainly of terrigenous origin based on the abundance of woody plant materials observed under the microscope. Consequently, the analysed sequences are predominantly gas prone, dominated by Type III and Type III-IV kerogen except for minor occurrence of mixed oil-gas prone Type II-III kerogen in the Belait Formation and in the slump mass transport deposits (MTD) of the West Crocker Formation.

Sedimentary Facies of the West Crocker Formation North Kota Kinabalu-Tuaran Area, Sabah, Malaysia

Newly outcrops exposed in the West Crocker Formation have led to the detail sedimentolgical analysis of the formation. Eight sedimentary facies have been recognised in which it was divided into three main groups: (1) sand-dominated facies (F1-F2), (2) poorly- sorted unit mixed sand and mud-dominated facies (F3), and (3) mud-dominated facies (F4-F5). These are: F1- graded sandstone (massive to planar laminated), F2-ripple-cross laminated, wavy and convolute lamination sandstone, F3-chaotic beds of mixed sandstone and mudstone blocks and clasts, F4-lenticular bedded of sandstone, and F5-shale. The studies of the formation has come out that it was deposited in a sand-rich submarine fan with specific location located at (1) inner fan channel-levee complex; (2) mid-fan channelised lobes, and (3) outer fan.

Coal-bearing strata of Labuan: Mode of occurrences, organic petrographic characteristics and stratigraphic associations

The current study describes the mode of occurrences of Labuan Cenozoic coals as observed in the field and identifies the coal macerals based on their organic petrographic characteristics as observed under reflected white light and blue light excitation. In this study some sedimentological aspects such as the depositional environment were correlated with the organic petrological characteristics of the coals. Based on the organic petrographic features and the thermal maturity as determined by vitrinite reflectance some new stratigraphic associations have been identified. Similarities in sedimentological and organic petrological characteristics suggest that the shaly strata associated with carbonaceous sandstones exposed on the north-western part of Labuan Island and the outcrop exposed in the south within the east Kiam Sam Peninsula belong to the same sequence within the Setap Shale Formation. Based on petrographic characteristics described and vitrinite reflectance values obtained from this study, at least four distinct units that are associated with coal-bearing sediments can be recognized. Strata with vitrinite reflectance (VR, %Ro) in the range of approximately 0.4–0.5% is the youngest and belongs to the Belait Formation which include the Tg. Layang-Layangan unit. The oldest sequence outcropping at Tg. Punei near the Labuan Crude Oil Terminal (Shell Terminal) belongs to the West Crocker Formation, possesses vitrinite reflectance in the range of 0.8–0.9%, whereas the intermediate unit is the Setap Shale Formation which possesses VR of 0.55–0.6% (including the East Kiam Sam sandstone unit) and Temburong Formation which possesses VR in the range of 0.65–0.75%.It ought to be noted that the differences in the thermal maturity variations within the Cenozoic sediments of Labuan reported here does not form the fundamental basis of the stratigraphic subdivision of Labuan, but an attempt to associate it with what appear to be the still unresolved stratigraphic issues of Labuan. These VR values suggest the Belait Formation is immature, Setap Shale Formation is early mature, while the Temburong and West Crocker Formations are at peak maturity for liquid hydrocarbon generation. The analysed coals are predominantly mangrove-derived and considered to be oil-prone as suggested by the common occurrences of oil haze, suberinite, bituminite, exsudatinite and perhydrous vitrinite.

Sedimentary facies analysis and depositional model of the Palaeogene West Crocker submarine fan system, NW Borneo

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) comprises 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 (30–60m) thinning and fining upward facies succession, which are dominated in their lower part by thick-bedded (1–6m), amalgamated 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 2–10m thick, coarsening upward, which are overlain by 5–20m thick fining upward facies successions; these successions are dominated by high-density turbidites (c. 0.5–1m thick) and linked co-genetic turbidite–debrite beds (0.1–0.5m thick), with subordinate mudstone facies. (3) Non-channelised lobes; comprise 5–20m 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 (2–3m thick beds) form amalgamated units at the top of these successions. (4) Distal lobes; represented mudstone-dominated intervals with mainly thin (1–10cm thick) low-density turbidites and occasional muddy debrites. (5) Mass transport complexes (MTCs); characterised by highly deformed slumped units (up to 2.5–5m thick).It is inferred that the five genetic units were deposited within four proposed laterally contiguous depositional 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.

Sedimentology, stratigraphic occurrence and origin of linked debrites in the West Crocker Formation (Oligo-Miocene), Sabah, NW Borneo

The West Crocker Formation (Oligocene–Early Miocene), NW Borneo, consists of a large (>20 000 km 2) submarine fan deposited as part of an accretionary complex. A range of gravity-flow deposits are observed, the most significant of which are mud-poor, massive sandstones interpreted as turbidites and clast-rich, muddy sandstones and sandy mudstones interpreted as debrites. An upward transition from turbidite to debrite is commonly observed, with the contact being either gradational and planar, or sharp and highly erosive. Based on their repeated vertical relationship and the nature of the contact between them, these intervals are interpreted as being deposited from one flow event which consisted of two distinct flow phases: fully turbulent turbidity current and weakly turbulent to laminar debris flow. The associated bed is called a co-genetic turbidite– debrite, with the upper debrite interval termed a linked debrite. Linked debrites are best developed in the non-channellised parts of the fan system, and are absent to poorly-developed in the proximal channel-levee and distal basin floor environments. Due to outcrop limitations, the genesis of linked debrites within the West Crocker Formation is unclear. Based on clast size and type, it seems likely that a weakly turbulent to laminar debris-flow flow phase was present when the flow event entered the basin. A change in flow behaviour may have led to deposition of a sand-rich unit with ‘turbidite’ characteristics, which was subsequently overlain by a mud-rich unit with ‘debrite’ characteristics. Flow transformation may have been enhanced by the disintegration and incorporation into the flow of muddy clasts derived from the upstream channel floor, channel mouth or from channel-levee collapse. Lack of preservation of this debrite in proximal areas may indicate either bypass of this flow phase or that the available outcrops fail to capture the debris flow entry point. Establishing robust sedimentological criteria from a variety of datasets may lead to the increasing recognition of co-genetic turbidite-debrite beds, and an increased appreciation of the importance of bipartite flows in the transport and deposition of sediments in deepwater environments.

Sedimentology of the Jalan Salaiman and Bukit Melinsung outcrops, western Sabah: is the West Crocker Formation an analogue for Neogene turbidites offshore?

Outcrops of the West Crocker Formation in western Sabah are dominated by coarse-grained sandstones interbedded with shale, although numerous bedding-plane thrust faults that form preferentially in the shales and weathering that favours exposure of sandstone suggest that the actual sand-shale ratio may be significantly lower. The sandstones occur as amalgamated units with individual beds that are generally 1-6m thick within 25-65 m thick parasequences. Most sandstones are massive and display partial Bouma sequences. The sands are texturally immature with a high proportion of rock fragments and poorly sorted. Their sedimentary structures and texture are consistent with a short transport path down a relatively steep slope and then rapid deposition from collapse fall-out in high density turbidity currents. In the outcrops studied in detail, comprising nearly 500 m of succession some of which is laterally continuous up to 500 m, most beds are sheet sands and a few are lobate and there is no evidence of channeling. The bed geometries, texture and depositional mechanism all suggest relatively small lobes that coalesced to form a sand-rich slope apron. Palaeocurrent directions are consistently to the north, indicating a transport direction that is oblique to the northeast-southwest marginal basin. This suggests that the West Crocker strata were derived from nearby Rajang Group sediment, possibly in response to the initial phase of the uplift that formed the Deep Regional Unconformity. The tectonic setting, facies distribution, stratigraphic architecture, sand body orientation, texture and sorting of the West Crocker turbidites are all significantly different from those of the Neogene turbidites offshore and, therefore, they are a poor analogue for the younger sands.

The ‘Rajang accretionary prism’ and ‘Lupar Line’ problem of Borneo

Abstract The Rajang Group, composed of the Belaga and Lupar Formations of Sarawak and the Embaluh Group and Selangkai Formation (in part) in Kalimantan, had a turbidite sedimentation history from Early Cretaceous to Late Eocene. These rocks generally young northwards. Inliers within the eastern Miri Zone have been mapped as the Kelalan and Mulu Formations. The Rajang Group was compressed into a steeply dipping quartz-veined phyllite-quartzite complex by the Sarawak orogeny and unconformably overlain locally in the north by the Upper Eocene continental to neritic Tatau Formation, extensively in the south by Middle to Upper Eocene basal continental sequences of the Ketungau, Mandai and Melawi basins, and widely in the north by the Upper Oligocene coastal to marine Nyalau Formation. In Sabah and East Kalimantan, the Upper Cretaceous to Upper Eocene Mentarang, Sapulut, Trusmadi, and possibly the East Crocker Formations, also belong to the Rajang Group. The West Crocker Formation demonstrates rapid facies changes into the more shaly Temburong Formation, and was deposited as sandy turbidites throughout the Oligocene. To the south their equivalents are the nearshore Kelabit and Long Bawang Formations. The West Crocker Formation was folded and uplifted in several Miocene pulses, resulting in regional unconformities and igneous events at Mount Kinabalu. The West Crocker Formation has not been metamorphosed, and dips are shallower than in the Belaga and Trusmadi Formations. Its provenance probably was from the uplifted Upper Cretaceous to Eocene Lurah and Kelalan formations of NE Kalimantan and East Sarawak. It is therefore proposed that the West Crocker and Temburong formations be excluded from the Rajang Group. Middle to Late Miocene Crocker Formation uplift and deformation, herein called the Sabah orogeny, was synchronous with spectacular basin inversion throughout the South China Sea and in the Meratus Mountains of Kalimantan. Uplift ceased in the Late Miocene and undeformed post-inversion formations unconformably overlie inverted folded structures. The Rajang Group flysch-belt may be interpreted as a north-facing accretionary prism. The Schwaner Mountains represent a subduction-related Lower to Upper Cretaceous volcanoplutonic arc. Scattered Eocene volcanism, Miocene Sintang intrusives and Pliocene Metalung volcanics in Central Kalimantan and Sarawak post-date subduction. The Rajang Basin (Danau Sea) rapidly narrowed and by Eocene time subduction was transformed to collision as the Rajang Group was compressed between the Schwaner Mountain Zone and the Luconia-Balingian-Miri block. The Ketungau Basin is in sharp contact with the Rajang Group along the bounding Lupar Fault, which can be traced northwards into the East Natuna region. Palaeocurrents show that the Upper Eocene basal sandstones have a provenance in the metamorphosed Sibu Zone. The Melawi and Mandai basins of Kalimantan also unconformably overlie the flysch-belt. The basins are not forearc and were formed after transformation of the accretionary prism to a landmass formed of a collisional orogenic complex.