Trough Cross-bedding Research Articles

The Folster Lake Formation, Nunavut: remnant of a littoral to fluvio-deltaic source to the Paleoproterozoic-age Penrhyn basin

The Folster Lake Formation consists of Paleoproterozoic-age sedimentary cover units unconformably deposited on deeply weathered Archean basement of the Rae craton on Melville Peninsula, Nunavut. It comprises a lower member, formed of basal conglomerate, hematite-specularite iron-formation, mudstone, siltstone, silty limestone, and cross-bedded arkose, and an upper member dominated by arkose with planar and trough cross-beds, including giant (up to 10 m thick) compound cross-beds, overlain by quartz arenite with heavy mineral laminae. The entire succession has been historically interpreted as a near-shore, tide-dominated succession derived from a source to the southeast. Our field observations, supported by SHRIMP U–Pb analyses on detrital zircon, suggest that the Folster Lake Formation represents the remnants of a 1.91–1.88 Ga sand-dominated delta advancing on a tide-dominated shoreline, sourced by detritus eroded from the Thelon, Queen Maud, and Boothia-Somerset uplift to the west-northwest. This fluvio-deltaic system transported sediments to the Upper Penrhyn Group, which was contemporaneously being deposited in a basin opened to the southeast.

Geochemistry of the North Gondwana Paleozoic Araba and Naqus formation siliciclastics, Sinai: implications for provenance, paleoweathering, and tectonic setting

ABSTRACT The Araba and Naqus formations in Ras Milan, Sinai, constitute part of the major continuous Paleozoic clastic belt stretching across northern Gondwana. They are sandstone-dominated successions, resting on Precambrian granitic basement, with lowermost thin basal polymictic conglomerate deposits (1–2 m), marking the unconformity. The Araba Formation section is composed mainly of varicoloured violet to reddish brown, fine to coarse-grained laminated and planner and overturned cross-bedded sandstones, while the overlying Naqus Formation is characterized by chaotically distributed poorly sorted quartz pebbles to cobbles within a moderately-sorted coarse- to medium-grained quartz arenite and by abundance and variety of large-scale tabular and trough cross bedding. Modal QFL classification of Araba and Naqus formation sandstones revealed that they are merely quartzose sandstones (quartz arenites). Geochemistry of the succession shows extremely wide compositional ranges for almost all major elements, but the Araba Formation is relatively enriched in SiO2, TiO2, Fe2O3*, Na2O, P2O5, and depleted in Al2O3, MgO, CaO and K2O relative to Naqus Formation. Only the Araba Formation samples are depleted in the transition elements Ni, Cr and Co and oppositely possess extreme enrichment in the HFSEs (i.e. Zr, Hf, Y, Nb, Ta, Th, U), whereas both formations show variable depletion in the LILE Rb, K and Ba, and excessive REE abundances relative to the PAAS and UCC, and LREE-enriched patterns with marked negative Eu anomalies. The provenance of the Naqus and Araba formations could be an earlier felsic magmatic source, which has undergone extensive sedimentary recycling. They possess high compositional maturity and were subjected to intensive to moderate weathering during humid climatic conditions. Passive margin tectonic setting is implied which denotes the derivation of Araba and Naqus formation siliciclastics from stable continental regions or plate interiors and deposition in intracratonic basins.

Arthropleura trackway ( Diplichnites cuithensis ) from the Carboniferous, Serpukhovian, Limestone Coal Formation, Clackmannan Group, Linn Park, Glasgow

The arthropleurid trackway Diplichnites cuithensis has previously been described from Scotland from the Upper Carboniferous Serpukhovian Limestone Coal Formation on the Isle of Arran and the Lower Carboniferous Visean Pittenweem and Anstruther Formations on the East Fife coast. Here we describe a new west coast single trackway from the Serpukhovian Limestone Coal Formation of Glasgow's Linn Park. The trackway occurs associated with simple horizontal burrows assignable to Planolites? , vertical openings of Arenicolites , examples of Taenidium barretti (formerly Beaconites barretti ), and irregular large-scale bioturbation or possibly rootlet casts. The trace fossils and sedimentary structures (including trough cross-bedding and flaser bedding) indicate a fluvial sandbar or plain environment, possibly of estuarine origin, locally colonized by plants. Diplichnites cuithensis (and other Diplichnites species) commonly occur associated with the burrow Taenidium barretti . The latter is known to have been widespread globally throughout the Carboniferous, and is a common component of fluviatile sequences within the Lower Carboniferous succession of NW Ireland. This suggests that previously undocumented older Scottish Carboniferous examples of both Diplichnites ichnospecies and Taenidium barretti may also be present, assuming that suitable environments persisted and are currently adequately exposed.

High-resolution lithostratigraphy and reconnaissance sedimentology of Changotaung structure, Chittagong Tripura fold belt, Bengal Basin, Bangladesh

Unlike other structures in the vicinity of the Chittagong Tripura Fold Belt, the Changotaung anticline is one of Bangladesh's least explored structures. An attempt has been made for the first time to understand and document sedimentary deposits, environments, structure, and tectonic activity based on the high-resolution outcrop and reconnaissance study with the knowledge of broad-brush geology. We found that Changotaung is a symmetrical box-folded structure with an extensive western flank where the amount of dip varies between 11° and 45°. The exposed Cenozoic succession was categorized into three separate sedimentary sequences and correlated with the conventional stratigraphic unit. A first-order simple Markovian approach was presented for the exposed litho-section in an effort to illustrate vertical facies variations in the Upper Surma group. We quantified that heterolithic bed mostly overlies both trough cross-bedding ({P}_{ij}U = 0.706) and parallel laminated bed ({P}_{ij}U=0.955) according to the facies transition probability matrix. According to the results of the stationary distribution, there is a 40% chance of coming across heterolithic beds within the Upper Surma group during any given event that is completely random whereas trough cross-bedding, parallel laminated bed, cumulative sandstone facies, and cumulative shale facies shows around 10.8%, 15.2%, 20.6%, 13.4% probability. We hypothesized, based on the interpretive facies analysis, that the Chittagong Tripura fold belt region's Upper Surma Group underwent three interrelated depositional settings (wave-dominated shallow marine, tide-dominated shallow marine, and fluvio-deltaic distributary).

The cambrian gog quartzite and deadwood formations of alberta: lessons for subsurface carbon sequestration

Injecting carbon dioxide into reservoirs has been undertaken since the 1940s, mostly as a method to enhance oil recovery. With the recognition of the impact of climate change, interest in carbon sequestration has increased exponentially, with hundreds of projects in progress around the globe. Many of these projects focus on Cambrian quartzites, which meet the requirements for carbon dioxide injection (CCS). Several CCS projects in Alberta, Canada, currently focus on using these reservoirs, including the Basal Cambrian Sandstone and Deadwood Formations, for injection and storage.A series of spectacular outcrops of the Cambrian Gog Quartzite are available for study in the area around Lake Louise in the Canadian Rockies of Alberta. These outcrops provide compelling analogues to other clastic Cambrian formations in the province that have been utilized for CCS. As an example, the Gog Quartzite was used by Shell as a direct reservoir analogue when modeling CO2 injection into the Basal Cambrian Sandstone in the QUEST Project. The Gog Quartzite also has potential to act as a CCS reservoir in its own right and may reach 2 kilometres in thickness.Outcrops of the Gog Quartzite were studied at Sink Lake, Spiral Tunnels and in the vicinity of Lake Louise in Alberta. They include fluvial and shallow marine, high net:gross sandstone beds with stacked trough cross-bedded sandstones. These are commonly interbedded with thin mudstone beds. Sedimentary structures include planar and trough cross-beds, wave ripples and contorted horizons interpreted as seismites with associated dewatering. Some units of the Gog Quartzite are heavily bioturbated with burrows including Arenicolites and Skolithos as well as other marine traces such as trilobite related ichnofacies.The Cambrian Deadwood Formation is also a target for carbon dioxide sequestration and provides the main reservoir for the Aquistore Project in Saskatchewan. It has been targeted by exploration wells in eastern Alberta and a new core study has demonstrated its suitability as a CO2 reservoir. Facies ranging from regolith overlying igneous basement, through alluvial fan and tidal deposits, and out into shallow marine settings with well developed parasequences, are all seen in the cores.The outcrop and core studies provide new data on Cambrian reservoirs which can be applied directly to potential Cambrian CCS targets in the subsurface of Alberta. The data can also be used to identify other potential Cambrian CO2 sinks around the world.

Provenance, depositional process, and tectonic setting of gold placer from the Bétaré-Oya Gold District (East-Cameroon, Central Africa) along the Precambrian Sanaga fault

The Bétaré-Oya Gold District is one of the three gold districts in East Cameroon with varied types of mining. The study site is an open-cast mine located in an alluvial plain. The strata succession globally consists of two positive sequences represented by three facies associations and seven lithofacies: massive clast-supported (Gcm), massive trough-cross bedded (Gtm), and massive matrix-supported (Gmm) conglomerates; massive sands (Sm); and massive (Fm), heterolothic (Fhl), and convolute and heterolithic (Fhlc) clays. The facies analysis indicates deposition after a recent tectonic event creating a depression, followed by a rapid deposition of varied facies and energies of sedimentation with fluvial and gravity inputs. The deposits come from proximal to distal sources but more proximal. The identified heavy mineral or accompanying minerals reveal a plutonic source (tourmaline sometimes folded), a volcanic source (olivine or clino-pyroxene with cracks), and a metamorphic source (sillimanite, andalusite, and staurolite). In the pan concentrates of placer with high silver (Ag) concentration (100 ppm) are also associated with relative abundance of lead (Pb) (17.8 ppm), zinc (Zn) (27 ppm), and low levels of copper (Cu) (3.1 ppm). The concentration and distribution of some element ratios, such as thorium/scandium (Th/Sc), chromium/thorium (Cr/Th), and europium anomaly (Eu/Eu∗), rare earth elements (REEs) and aluminum oxide/titanium dioxide (Al2O3/TiO2) vs. silicon dioxide (SiO2) plots for the studied sediment indicate heterogeneous sources of rocks with dominance of felsic sources. The discriminant diagram reveals a recycled or sedimentary provenance of the deposited sediments. The tectonic setting plot indicates a collision tectonic setting which is consistent with the Precambrian history of the study area which belongs to the Pan-African North-Equatorial fold Belt. The gold deposits in the Bétaré-Oya area probably derive from several sources, such as a vein source (from magmatic and metamorphic processes of the Neoproterozoic age) and a sedimentary source (from remobilization of ante-Neoproterozoic rocks of Archean and Paleoproterozoic age), deposited during the Cenozoic period linked to the reactivation of the Precambrian Sanaga fault. These are likely associated with a supergene source as indicated by the presence of dissolution microstructures. The cases of detrital gold deposits from several sources has been reported for the Serpont gold deposits in South-East Belgium, and those associated with authigenic forms are known in Poland, New Zealand, and Tanzania.

Sedimentary Facies, Architectural Elements, and Depositional Environments of the Maastrichtian Pab Formation in the Rakhi Gorge, Eastern Sulaiman Ranges, Pakistan

An integrated study of sediments was conducted to examine the facies architecture and depositional environment of the Cretaceous Pab Formation, Rakhi Gorge, and Suleiman Ranges, Pakistan. This research focused on analyzing architectural elements and facies, which are not commonly studied in sedimentary basins in Pakistan. To identify lithofacies, outcrop analysis and section measurement were performed. The identified lithofacies were then categorized based on their depositional characteristics and facies associations, with a total of nine types identified within a stratigraphic thickness of approximately 480 m. These facies were mainly indicative of high-energy environments, although the specifics varied by location. Sedimentary structures such as planar and trough crossbedding, lamination, nodularity, load-casts, and fossil traces were found within these facies, indicating high-energy environments with a few exceptions in calm environments. The identified facies were grouped into seven architectural elements according to their depositional environments: delta-dominated elements, including laminated shale sheet elements (LS), fine sandstone elements (SF), planar cross-bedded sandstone elements (SCp), trace sandstone elements (ST), and paleosol elements (Pa); and river-dominated elements, including trough cross-bedded sandstone elements (SCt), channel deposit elements (CH), and paleosol elements (Pa). These architectural elements, along with their vertical and lateral relationships, indicate a transitional fluvio-deltaic environment within the Pab Formation. In conclusion, by interpreting facies and architectural elements, it is possible to gain a better understanding of the depositional history of the formation and the distribution of reservoir units.

Assessment of Reservoir Quality of the Cretaceous Yolde Sandstone: A Case Study of Doma Stream, Gongola Basin, Northern Benue Trough, Northeast Nigeria.

Sedimentology, petrography and petrophysical studies were applied to the Cretaceous Yolde Formation sediments along the Doma stream, to evaluate its reservoir quality. The Yolde Formation along the Doma Stream is composed of lithologies that are laterally extensive and have reached a thickness of about 80m. They are lithologically made of sandstones with dark grey mudstones, laminated shales and grey to pale yellow limestones. The Sandstones are structurally characterized by planar, tabular and trough cross-beds, convolute beds, and hummocky cross-stratifications with reactivation surfaces. Some of the sediments are bioturbated. The petrophysical evaluation indicated porosity values ranging from 6% to 26%, and permeability values between 12.7mD and 108mD. These values are comparable to the reservoir rocks of proven petroleum basins of the North Sea and Niger Delta. Therefore, the Yolde Sandstones of the study area can have great potential to serve as good reservoir rock in the Gongola Basin.

New insights into deep-lacustrine architectural elements: Examples from the upper Triassic Yanchang Formation, Ordos basin

Deep-lacustrine systems are considerably less studied than their marine counterparts, mostly due to the low number of large and continuous outcrops worldwide. This study details outcrops and cores from Chang 7, Ordos Basin, China, which are composed dominantly of fine-grained deposits interbedded with amalgamated sandstones. Thick sandstone deposits, previously described as massive sandstones and interpreted as sandy debrites, are here re-interpreted as amalgamated sandstones, deposited by high-density turbidity currents associated with deep-lacustrine slope channels. Two outcrops composed of these deposits, which form intervals ranging from 6 to 20 m thick, laterally ranging from 600 to 1200 m, preserving evidence of sediment bypass such as erosional features and abundant trough cross-bedding, have been interpreted as lacustrine slope channels. Deposits composed dominantly of interbedded thin-bedded normal-graded sandstone and mudstone, with common occurrences of ripple cross-lamination (>70% of the beds), interbedded with sporadic amalgamated medium-bedded sandstones have been interpreted as levee deposits. These deposits outcrop laterally to slope channel deposits, supporting the interpretation they are genetically and architecturally related. Similar deposits are also described in core, overlying channelised sand-prone deposits. Interbedded thin- to medium-bedded normal-graded sandstones and mudstones, which are not associated with a confining surface (non-channelised), nor an adjacent slope channel, have been interpreted as terminal splays. The re-interpretation of the sandstone-prone deposits of the Yanchang Formation as slope channel-levees to terminal splays provides a different approach to lateral and temporal distribution of architectural elements in intracratonic lacustrine basins, and therefore hydrocarbon exploration and production.

Fossil vertebrates of the early-middle Miocene Cerro Boleadoras Formation, northwestern Santa Cruz Province, Patagonia, Argentina

The early-middle Miocene continental Cerro Boleadoras Formation (CBF) crops out in the area of Cerro Boleadoras and Cerro Plomo on the western slope of the Meseta del Lago Buenos Aires, northwestern Santa Cruz Province, Argentina. The lower levels of the CBF consist of laterally extensive medium to pebbly sandstone beds with trough cross-bedding, interpreted as fluvial channel deposits, interbedded with tabular fine-grained floodplain deposits. Recent fieldwork provided fossil vertebrates from these levels with an estimated age between ~16.5 Ma and 15.1 Ma
 (late Burdigalian-early Langhian). The studied section temporally overlaps with the middle or upper sections of the Santa Cruz Formation (SCF) in the Austral-Magallanes Basin of southern Patagonia, the Río Frías Formation in Chile, and the lower Collón Curá Formation of northern Patagonia. We compile an integrated faunal list for this locality, including specimens from previous collections, and discuss its chronological and paleoenvironmental implications. The taxa list includes most of the groups recorded in the SCF: one anuran, three birds, and at least 33 mammals (metatherians, xenarthrans, litopterns, notoungulate typotheres and caviomorph rodents), indicating a Santacrucian age sensu lato. We also recorded a testudine, which constitutes the southernmost record of tortoises in South America and worldwide. Faunal dissimilarities between the vertebrate fossil content of the CBF and the mentioned sections of the Santa Cruz, Río Frías
 and Collón Curá formations may reflect ecologic, climatic and geographic differences rather than temporal ones. The co-occurrence of arboreal or semiarboreal, browsing, frugivorous, and grazing mammals suggests the presence of both forested and open environments for the area occupied by the CBF rocks. However, it is not possible to discern whether these two environments coexisted or alternated, and whether one environment predominated over the other. Marker taxa, such as the chinchillid rodents Prolagostomus and Pliolagostomus, and the typothere Pachyrukhos indicate a trend to aridification during the Miocene in southern Patagonia, as previously reported for the upper part of the SCF along the Río Santa Cruz and south to the Río Coyle, along the Atlantic coast and the Río Gallegos.

Microbial, tidal, and storm activity in a macrotidal to shallow marine shelf environment during the Paleoproterozoic era

The Gordon Lake Formation (GLF) of the Paleoproterozoic Huronian Supergroup is a siliciclastic-dominated succession ranging from 300 to 1100 m in thickness. Lithostratigraphic and sedimentological analyses of the formation in the Bruce Mines and Flack Lake areas, and Killarney and Lady Evelyn-Smoothwater provincial parks, Ontario, Canada, revealed seven lithofacies, which comprise three distinct lithofacies associations. The lithofacies associations are subtidal nearshore, subtidal to shallow shelf, and mixed intertidal flat. A variety of structures interpreted to be biogenic in nature, including microbially induced sedimentary structures (MISSs) and stromatolites, are preserved, which support local microbial colonization in a tidally influenced marine environment. Wave, current, and tide-generated sedimentary structures, including symmetrical ripples, trough cross-beds, flaser and lenticular bedding, and mudstone drapes, are abundant in all study areas. Storm influence is suggested by normally graded deposits, mudstone rip-up clasts, and soft-sediment deformation structures (SSDSs), including load casts, ball-and-pillow structures, convolute bedding, and pseudonodules. Interbedding and interlamination of sandstone and mudstone units are present throughout the GLF and represent fluctuations in water level and energy, related to tidal and storm processes. A lowermost carbonate-rich unit may represent a period of low clastic influx. The contacts with the underlying Lorrain and overlying Bar River formations appear gradational. The depositional environment can be visualized as an open coast, shallow marine shelf that was influenced by microbial mats, tides, and storms.

Provenance, tectonic setting and palaeoclimate of Proterozoic Jiran Sandstone, Southeastern Rajasthan, India: A petrographic approach

Proterozoic Jiran Sandstone rests unconformably on Binota Shale and Khori-Malan Conglomerate. The Jiran Sandstone is comprised mainly of fine to medium-grained, varicolored, thickly bedded sandstones, showing diverse primary sedimentary structures such as ripple marks, planar, and trough cross-bedding. Petrographically, Jiran Sandstone is of mainly quartzarenite which is composed of varieties of quartz with ultra-scarcity of feldspar, lithic fragments, micas, and heavy minerals. Quartz is more abundant mineral shown by X-ray Diffraction Analysis. The provenance, tectonic setting, and paleoclimatic condition of the Jiran sandstone were evaluated using integrated petrographic studies. Analysis pursuant, monocrystalline and polycrystalline quartz grains and heavy minerals are driven primarily from metamorphic and plutonic Precambrian basement source rocks of a craton interior setting with a minor quartzose recycled sedimentary source material. Intensive chemical weathering in warm and humid paleoclimate is indicated by lack of feldspar and rock fragments.

Ichnology and Sedimentology of the Lower Cretaceous Wabiskaw Member (Clearwater Formation) Alberta, Canada

Identifying facies and paleoenvironmental interpretation of the rock record is complicated due to the interplay of independent variables (i.e. wave-, river- and tidal-input) in marginal- and shallow-marine environments. This study integrates sedimentology and ichnology to characterize the depositional environments of the Lower Cretaceous Wabiskaw Member. The deltaic and strand plain shoreface-offshore deposits of Wabiskaw Member of Clearwater Formation of northeast Alberta provide an excellent case study to evaluate the ichnological and sedimentological characteristics associated with laterally and vertically variable stresses in wave-influenced nearshore settings. The Wabiskaw Member is studied using four sedimentary facies associations (Ten sedimentary facies). Facies association 1(FA-1) consists of massive, sharp-based mudstones and lenticular sandstone with small-scale soft-sediment deformation features, syneresis cracks and small-scale oscillation ripples. The ichnological suite mainly includes small grazing and deposit-feeding traces, representing the Phycosiphon Ichnofacies. Facies association 1(FA-1) is interpreted to record deposition in a prodeltaic setting. Facies association 2 (FA-2) is fine-to-medium-grained sandstone and thin mudstone with current, oscillation and combined flow ripples. The low angle and trough cross-beds, soft-sediment deformation structure, mud chips and coal debris are common. The trace fossil suite includes sporadically distributed deposit-feeding traces belonging to the Rosselia Ichnofacies. This facies association is interpreted to be deposited in the delta front to a mouth bar setting. Facies association 3 (FA-3) is gray to bluish-gray mudstone with minor sandstone interbeds (massive, planar parallel to hummocky cross-stratified). FA-3 is moderate to highly bioturbated. The ichnodiversity and abundance is high with dominant horizontal and subordinate vertical traces, including the dominance of deposit and detritus feeding traces representing the archetypal Cruziana Ichnofacies ichnological suite. Facies association 3 (FA-3) is interpreted as being deposited in a storm-influenced offshore environment. Facies association 4 (FA-4) is upper fine to fine-grained glauconitic sandstone with minor mudstone interbeds at the base. Physical sedimentary structures including massive and planar (horizontal and low angle), hummocky, and swaley crossing-stratification. FA-4 is heavily burrowed with a diverse suite of horizontal and vertical traces of deposit and detritus-feeding structures, representing a proximal expression of Cruziana Ichnofacies. Facies association 4 (FA-4) represents distal lower to middle shoreface deposition. The Wabiskaw Member deltaic (prodelta-delta front) deposits, producing characteristic sedimentological-ichnological signatures, distinguishing these deposits from related strand plains. In addition to characteristic deltaic traits (e.g. soft-sediment deformation structures, fluid mud and syneresis cracks), these deposits commonly contain comparably stressed low-diversity and diminutive trace-fossil suites. On the other hand, fully marine strand plain shoreface-offshore complexes are characterized by comparably robust trace fossils with high ichno-diversity and bioturbation intensities.

Evolution of a high latitude high-energy beach system (Maastrichtian–Eocene, Magallanes/Austral Basin, Chilean Patagonia)

Studies on the environmental dynamics of high energy beach systems have to deal with factors as diverse as wave energy, coastal currents and tidal amplitude. Their interaction produces complex and often poorly understood sedimentary architectures. As a rule, the results achieved do not allow us to understand the depositional architectures associated with each of these processes. In this article, we analyze a high-energy beach system describing geometries, textures, paleocurrents, ichnological associations and taphonomic aspects seeking to define the associated environmental parameters. Detailed analyses of sedimentary facies, and analyses of paleocurrents, ichnological and taphonomic associations were performed in a high resolution sequence stratigraphy. The integrated analyses demonstrate the evolution of a high-energy beach system with a general north-south direction in a meso- to macrotidal regime, built by waves from the northwest, generating longshore currents to the south. A subordinate pattern, with waves coming from the southeast, generating longshore currents to the north, was also interpreted. Due to the high wave energy, evidence of tide action is sporadic, but the wide dominance of upper shoreface deposits with low angle dips, indicating an extension in the continent-offshore section, are compatible with a meso- to macrotidal setting. Taphonomic analysis shows that skeletons of marine invertebrates and vertebrates were significantly reworked and redistributed by strong wave action and longshore currents marking high energy events related to scour surfaces. Changes in the pattern of ichnofauna and bioturbation intensity are associated with variations in environmental energy and probably in salinity. The ichnological data helps to indicate progressive environmental stress towards the Cretaceous/Paleogene (K/Pg) boundary. Paleocurrent data, measured in trough cross-bedding of the upper shoreface deposits, suggest a complex atmospheric circulation pattern and water circulation of an inland sea. The resultant climatic pattern is compatible with modern atmospheric circulation at a similar latitude. The excellent exposure and abundant fossil records at K-Pg interval make this region an important source for studies of environmental dynamics and their interaction with biota at middle-high latitudes.

Paleoarchean terrestrial to shallow marine sedimentation on Singhbhum Craton, eastern India (the Western Iron Ore Group)

Distinguishing shallow-marine and terrestrial (fluvial) sedimentary deposits is often difficult in the absence of fossils and challenging in deformed and metamorphosed early Precambrian terrains. Herein we report for the first time a > 3.4 Ga shallow marine to terrestrial deposit from the Western Iron Ore Group (WIOG), Singhbhum Craton, India. The WIOG sedimentary succession, lying below a ~ 3.4 Ga banded iron formation, has been divided into three facies associations: a lower alluvial fan-fluvial association, a middle shallow-marine association, and an upper fluvial association. The bottommost conglomerate–very coarse- to coarse-grained sandstone constitutes the alluvial fan-braided fluvial association. Sandstones of the facies association two bears mud drapes and herringbone cross-stratification and thus indicates tidal influence. These shallow-marine sandstones bear wave ripples, ladderback ripples, and adhesion structures and indicate an intertidal depositional environment. The overlying fluvial facies association is characterized by several fining-upward cycles of conglomerate–coarse- to medium-grained sandstones with large-scale trough cross beds, parallel lamination and penecontemporaneous deformation structures and minor shale, indicating the braided nature of the postulated river system. The WIOG succession indicates an overall shallowing-up trend because of sea level fall. The sedimentary structures and texture of the WIOG fluvial deposit are very similar to recent fluvial deposits and are likely to have formed by similar sediment transportation and depositional processes in a tectonically stable sedimentary basin.

Early Pennsylvanian fluvial - Aeolian interplay in the Amazonas Basin (central-western Gondwana) and its relation to marine transgression

The Monte Alegre Formation corresponds to the main reservoir rock in the Amazonas Basin petroleum system in Brazil and is correlated with the Pennsylvanian rocks of the Parnaíba and Solimões basins. Previous outcrop and well-based studies are concentrated on the southern edge of the basin and show that the Monte Alegre Formation basically represents an aeolian, deltaic and transitional marine succession. However, there is no published research that demonstrates the depositional system in the northern edge of Amazonas Basin. In this sense, outcrop-based facies and stratigraphic analysis is carried-out to understand the distal influence of marine incursion into the basin and its relationship with paleogeography in the Upper Carboniferous. The data show that the aeolian Monte Alegre system is represented by a braided fluvial system formed by five architectural elements: (i) sandy bedform, (ii) downstream-accretion macroform, (iii) gravel bars and bedforms, (iv) channel and (v) laminated sand sheets, pointing to a braided depositional system. The aeolian succession overlies the fluvial system and is represented by medium-scale trough cross-bedding and large-scale planar cross-bedded sandstones resulting from the accumulation and migration of transverse dunes toward the northwest that grade upward to dry interdunes and aeolian sand sheet deposits that are interbedded, consisting basically of translatent ripple cross-lamination and low-angle cross-stratified lamination sandstones related to water table raises. The stratigraphic record defines a wetting-upward stacking pattern of Monte Alegre Formation resulting from local sea level rise as a result the advance of the marine incursion that settled in the central-western region of Gondwana during the Late Carboniferous. Thus, in addition to corroborating the paleo wind directions predicted for the region during the Late Carboniferous, these deposits help to understand the paleoenvironmental relations between the northern and southern edges of the Amazonas Basin.

Tidal Channel Depositional Complex of the Cretaceous Yolde Formation of the Gongola Sub-Basin, Northern Benue Trough N. E. Nigeria

The facies analysis of the Cretaceous Yolde Formation at Gamajigo village in the Gongola Sub-basin of the Northern Benue Trough indicated fining upward a sequence characterized by the assemblages of five lithofacies that comprises of trough crossbeds, planar crossbeds, massive beds, ripple laminations, and mudstone. This fining upward architecture is defined by trough crossbedded sandstone with erosional contact at base overlain by interbedded sandstone and mudstones often displaying bi-direction paleocurrent patterns and growing mudstones content upwards moving into dominantly mudstones unit. This concurrently demonstrates dissipating energy intensity upwards as such reflecting a tide dominated system clearly of tidal channel depositional complex that most commonly develop in estuaries and tide dominated delta. Though on the account of the presences of Skolithos ichnofacies, a stressed hydrodynamic regime and indicating extension of tidal channel into the open sea may be very likely. This is generally indicative of a tide dominated oceanographic system in the advancing and inundating Cenomanian transgressive sea that define the coastal realm of the Gongola Sub-basin.

Regressive Shoreface Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-Basin Northern Benue trough N. E. Nigeria

The characterization of lithofacies of the Yolde Formation at Briyel town in the Gongola Sub-basin of the Northern Benue Trough indicated coarsening upwards cycles composed transitional succession of six lithofacies that comprises of trough cross-beds, planar cross-beds, massive beds, ripple laminations, parallel laminations and mudstone. This coarsening and thickening upward symmetry is defined by a densely bioturbated mud dominated lower part transitionally grading into heterolithic interval composed thinly bedded sandstone and mudstones both of which developed below fair-weather wave base. This is capped by a succession of moderately bioturbated trough-planar crossbedded sandstone with poly-directional paleocurrent system. These assemblages reflect shoreface deposits and devoid of hummocky cross-stratification therein may account for a moderate wave oceanographic system. Evolution of this setting in the Gongola Sub-basin is indicative of a scenario of a broaden coastline in the coastal palaeogeography of the Yolde Formation typically suppressing due to frictional damping.

Record of a nonbarred clastic shoreline

Abstract The morphology of wave-dominated clastic shorelines (i.e., foreshore and upper-shoreface sediments) can vary from barred to nonbarred, though the ancient record of nonbarred, sand-dominated shorelines has yet to be recognized. Here, a facies and quantitative architectural analysis of a clastic succession characterized by sandy inclined beds is presented and interpreted as the record of a high-gradient, nonbarred shoreline. Inclined beds dip seaward, have a tangential geometry (<3 m height, <40 m length, <11° dip), and are composed of planar lamination along the foresets and subordinate small-scale trough cross-bedding in the bottomsets. This facies distribution reflects a steep beach profile with a narrow surf zone and the development of plane beds both in foreshore and proximal upper-shoreface settings. Successive packages of inclined beds (a few tens of meters wide) are interpreted as the seaward accretion of this shoreline morphology, producing distinctive architectural elements (foresets and bottomsets). For the first time, we propose diagnostic criteria for identification in the rock record of the widely used modern nonbarred clastic shoreline model, and we contrast them with classical facies models of barred systems. Moreover, we discuss similarities and differences with radar-based Holocene coastal architectural elements, highlighting the need to incorporate detailed two-dimensional quantitative studies for refining the reconstruction of deep-time and recent clastic shorelines.

Facies and Architectural Element Analysis of Braided Fluvial Succession: The Tertiary Sawah tambang Sandstone, Sawahlunto, Indonesia

The Sawahtambang Sandstone Formation of Sawahlunto, Indonesia has hitherto never been studied in detail to ascertain its depositional processes and its palaeoenvironment. The Sawahtambang Sandstone has more than 394 m thickness which consists of conglomeratic sandstone, sandstone, and clay-silt intercalation within which six lithofacies types (St, Sp, Sh, Ss, Fl, and Fm) appear creating iterated fining upward sequence. Herewith, this paper aims to replenish the avantgarde sedimentological interpretation of the Sawahtambang Sandstone in the intermontane basin of Indonesia based on outcrops along the Trans-Sumatra Highway. The study is attained through facies identification based on stratigraphic measuring section or outcrop profile, studio analysis consists of log analysis and superposition reconstruction, and architectural element delineation according to facies association. Structures in clay-silt facies consist of lamination and fissile whereas in the sand grained include planar and trough cross-bedding, planar lamination and granule lag, which depicts a lower-flow-regime sand channel. The architectural elements that made from facies association are identified into five distinct elements (multi-storey channel, single storey channels, sand bedforms, laminated sand sheet, and floodplain fines), which present a fluvial environment. The relation of the architectural elements demonstrates that the Sawahtambang Sandstone uphold a record of the braided river system that flowed from southwest to northeast in the southwestern part of Ombilin Basin. The dominance of coarse-grained (channel and sandy bedform) element over clay-silt grained (laminated sand sheet and floodplain fines) element and the extensive appearance of thick amalgamated channel elements reinforce the interpretation of a low-sinuous braided fluvial system in which the stacking pattern shows the channel bodies accumulated both lateral via lateral accretion of point bar and via vertical amalgamated streams.