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.

MICROFACIES AND DEPOSITIONAL ENVIRONMENT OF TERTIARY LIMESTONE, GORONTALO PROVINCE, INDONESIA

The research area is located in northern Limboto Lake in Gorontalo Province, which has complex geological characteristics. The geological complexities include stratigraphy and tectonics which influence the formation of the Limboto Basin. Limestone research in the Late Tertiary Limboto Basin is very intriguing to be done because of the lack of research in limestone. Gorontalo limestone outcrops, which become the focus of the research, have a total thickness of 30 meters. The research objective is to analyze facies, microfacies, and depositional environment of tertiary limestone. These two research objectives are attained by using two research methods, namely measurd section and petrography analysis. The research result exhibits that there are four Gorontalo limestones facies, including coralline rudstone intercalated with thin mudstone facies, sandy micrite intercession facies, coralline rudstone intercession facies and sandy allochem limestone intercession facies. According to the limestone micro- facies standard, the depositional environment of Gorontalo limestone is platform interior restricted (facies zone 8).

FLUVIO-DELTAIC DEPOSITIONAL COMPLEX OF THE CAMPANO-MAASTRICHTIAN GOMBE FORMATION OF THE GONGOLA SUB-BASIN, NORTHERN BENUE TROUGH, N.E. NIGERIA

Evaluation of the stratigraphic architecture of the Gombe Formation of the Gongola Sub-basin in the Northern Benue Trough indicated a build-up from six facies assemblage that consist of trough crossbedded sandstone, planar crossbedded sandstone, massive bedded sandstone, ripple laminated sandstone, parallel laminated sandstone and mudstones. These units were packaged into three facies association that constitutes of bedded sandstone facies association (FAgI), interbedded sandstone and mudstone facies association (FAgII) and amalgamated trough crossbedded sandstone facies association (FAgIII). These reflects mouth-bars, pro-delta and delta slope deposits and upper delta plain respectively. This deltaic prism is characterized by unidirectional current system devoid of signatures of tide and waves hydrodynamics in the subaqueous delta regions, thus indicating that the delta system of the Gombe Formation is a fluvial dominated delta.

Tidal Flat Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue trough N. E. Nigeria: Implication for Macro-Tidal Coastline

This research aims to evaluate the facies and facies association of the Yolde Formation at Kware stream in the Gongola Sub-basin of the Northern Benue Trough with objective of characterizing its paleodepositional environment. Six lithofacies consisting of trough crossbedded sandstone facies (St), massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel sandstone facies (Sl) and mudstone facies (Fm) defining its stratal packages were skewed into distinctive assemblages of flaser, wavy and lenticular bedding. This present a fining upward signature with facies association typical of tidal flat system. This is evident of a coastal progradation with sequences reflecting migration of a supra-tidal mudflat over intertidal mixed-flat zone which progressively superposed subtidal sandflats. This is indicative of a coastal shoreline with a relatively progradational phase within the net transgressive regional framework of the Cretaceous Yolde Formation.

Tidal Rhythmites Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue Trough N. E. Nigeria

Facies evaluation carried out on the Yolde Formation at Gabukka locality in the Gongola Sub-basin of the Northern Benue Trough was aimed at enacting its paleo-depositional environment. The formation at this locality revealed an intercalated succession of massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel laminated sandstone facies (Sl) and mudstone facies (Fm). These successions developed a thinning and thickening stratigraphic profile depicting periodic rhythmic signatures indicating deposits of tidal rhythmites. Thickening rhythmic packages are reflective of a spring tide whereas thinning phases are indicative of neap tide. These depositional sequences are genetic to intense tides conditions, thus an indexing a tide dominated oceanographic within the course of development of the Cretaceous Yolde Formation.

Facies heterogeneity and source potential of carbonate-mudstone-dominated distal ramp deposits, Agrio Formation, Neuquén Basin, Argentina

ABSTRACT The carbonate-mudstone-dominated Lower Cretaceous Agrio Formation is the youngest marine source rock of the hydrocarbon-prolific Neuquén Basin in Argentina, yet its facies variability and unconventional hydrocarbon potential remains relatively understudied. Detailed studies of mudstone facies variability in thick, carbonate mudstone successions deposited largely below storm wave base (i.e., chalk–marl, black shale, limestone), like the Agrio Formation, are rare and instead commonly focus on biostratigraphy or organic geochemistry alone. A continuous northern section of the Agrio Formation and a southern composite section of the lower Pilmatué and middle Avilé members, totaling ∼ 1,200 m of outcrop, were measured. From these measured sections, programmed pyrolysis (n = 339 samples), X-ray diffraction (XRD; n = 69), and thin sections (n = 69) were used to develop a high-resolution integrated macrofacies and microfacies scheme. The four most volumetrically abundant facies include detrital-quartz-silt-bearing fine mudstone (facies 1), radiolarian-bearing calcareous fine mudstone (facies 2), detrital-quartz-silt- and shell-bearing calcareous fine mudstone (facies 3), and calcareous wackestone (facies 4). All four facies are volumetrically dominated by carbonate mud matrix (i.e., micrite) that represents either 1) original pelagic coccolithophore deposition modified by diagenesis, 2) transported carbonate mud (i.e., bottom currents like contour currents or sediment gravity flows), or 3) a combination of both. Outcrop observations, XRD mineralogic trends, and petrographic variations in grain composition between detrital quartz silt, radiolarian and microfossil to macrofossil content (mainly benthic foraminifera and bivalves) distinguish the four mudstone facies. The facies scheme indicates distinctly more heterogeneous and current-influenced sedimentation in the downdip sub-storm wave base than previously described in the Agrio and in carbonate-dominated basinal settings in general. A depositional model is proposed for further testing that may prove valuable towards re-evaluating basinal carbonate mudstone successions worldwide. Utilizing TOC, S2, and HI value cutoffs, this study defines five discrete stratigraphic packages in the Agrio Formation that have the highest source potential, collectively totaling ∼ 140 m thick. The novel integration of macrofacies and microfacies analysis, stratigraphy, and a geochemical analysis allow both depositional insights and the assessment of a potential source rock. The study adds to a growing body of literature on 1) carbonate ramp (or slope) to basinal processes and 2) facies models for organic-rich, carbonate-dominated mudstone successions that are unconventional hydrocarbon systems.

Mud deposition and diagenesis within an Early Palaeozoic clinothem: Power Steps Formation, Newfoundland, Canada

The early Ordovician (∼385 Ma) Power Steps Formation, Newfoundland, Canada, exposes a well-preserved mudstone-dominated clinothem that serves as an excellent archive for understanding how mud has been produced, transported and converted into mudstone prior to the evolution of globally widespread, deep soil horizons. Sedimentological analysis of four sandstone and five mudstone facies, along the Ochre Cove clinothem, reveal that mud and sand were delivered by unidirectional currents and experienced episodic reworking by storm waves. Petrographic examination and X-ray diffraction from described mudstone facies reveal significant variability in the distribution of illite versus chlorite between the lower and upper part of the Ochre Cove clinothem. This research highlights that in the present-day clay mineral fraction, illite is often detrital whereas chlorite originated via the alteration of silt-sized, highly unstable, mafic (volcanoclastic?) grains. Throughout all sedimentologic facies, albeit in different proportions, these mafic lithic grains were diagenetically altered via in situ weathering before significant compaction occurred, resulting in the precipitation of significant volumes of pore-bridging, silica- and iron-rich chlorite cement. Compositional, diagenetic and textural attributes across the Ochre Cove mud clinothem vary as a function of starting composition, hydrodynamic sorting and grain density. Given that a significant proportion of clay minerals has been generated via in situ transformation of a mafic, non-stable precursor assemblage, we recommend future studies to incorporate detailed petrographic description along with X-ray diffraction analyses when aiming to employ trends in whole-rock clay mineral data as a proxy in provenance and palaeoclimate studies of very old (pre-Devonian) mudstones and sandstones.

Upper Karoo vertebrate assemblages (Late Triassic/Early Jurassic) of the Lake Kariba region, Zimbabwe

Southern Africa provides critical information on Late Triassic–Early Jurassic terrestrial tetrapod faunas. Most of the localities in this region are in South Africa and Lesotho, but preliminary work in Zimbabwe has revealed significant potential. Early Jurassic Zimbabwean localities have yielded the basal sauropodomorph Massospondylus, the early sauropod Vulcanodon and theropod material. Late Triassic localities are also known, but have yielded only fragmentary specimens thus far. In early 2017, a joint South African-Zimbabwean-UK team conducted fieldwork in the upper Karoo-aged deposits along the shores of Lake Kariba, northern Zimbabwe (Mid-Zambesi Basin). We relocated the Vulcanodon type locality on Island 126/127 and found that, contrary to previous reports suggesting a Toarcian age, the quarry was in a horizon pre-dating the onset of Drakensburg volcanism (= Batoka Basalts). It is situated instead within the earlier Lower Jurassic Forest Sandstone. This indicates that Vulcanodon is 10–15 million years older than thought previously, recalibrating several nodes within Sauropoda and indicating extensive overlap between true sauropods and 'prosauropods'. Other new vertebrate localities show that sauropodomorphs are present in the Forest Sandstone and upper Tashinga (Late Triassic) formations, but a grey mudstone facies within the Pebbly Arkose Member of the latter unit yields a more aquatic fauna, including lungfish and phytosaurs, but lacking sauropodomorphs. The phytosaur occurrence is the first in Africa south of the Sahara. Faunal and sedimentological evidence indicates that the Late Triassic and Early Jurassic sites in this region were deposited under more mesic environments than their lateral equivalents in South Africa.

Upper Karoo vertebrate assemblages (Late Triassic/Early Jurassic) of the Lake Kariba region, Zimbabwe

Southern Africa provides critical information on Late Triassic–Early Jurassic terrestrial tetrapod faunas. Most of the localities in this region are in South Africa and Lesotho, but preliminary work in Zimbabwe has revealed significant potential. Early Jurassic Zimbabwean localities have yielded the basal sauropodomorph Massospondylus, the early sauropod Vulcanodon and theropod material. Late Triassic localities are also known, but have yielded only fragmentary specimens thus far. In early 2017, a joint South African-Zimbabwean-UK team conducted fieldwork in the upper Karoo-aged deposits along the shores of Lake Kariba, northern Zimbabwe (Mid-Zambesi Basin). We relocated the Vulcanodon type locality on Island 126/127 and found that, contrary to previous reports suggesting a Toarcian age, the quarry was in a horizon pre-dating the onset of Drakensburg volcanism (= Batoka Basalts). It is situated instead within the earlier Lower Jurassic Forest Sandstone. This indicates that Vulcanodon is 10–15 million years older than thought previously, recalibrating several nodes within Sauropoda and indicating extensive overlap between true sauropods and 'prosauropods'. Other new vertebrate localities show that sauropodomorphs are present in the Forest Sandstone and upper Tashinga (Late Triassic) formations, but a grey mudstone facies within the Pebbly Arkose Member of the latter unit yields a more aquatic fauna, including lungfish and phytosaurs, but lacking sauropodomorphs. The phytosaur occurrence is the first in Africa south of the Sahara. Faunal and sedimentological evidence indicates that the Late Triassic and Early Jurassic sites in this region were deposited under more mesic environments than their lateral equivalents in South Africa.