The age and depositional environments of the lower Karoo Moatize Coalfield of Mozambique: insights into the postglacial history of central Gondwana

A regional review and new insights into SE Asian Cenozoic coal-bearing sediments: Why does Indonesia have such extensive coal deposits?

Facies analysis and tectonic significance of lacustrine fan-deltaic successions in the Pliocene–Pleistocene Mugello Basin, Central Italy

The Upper Cretaceous Rock Springs Formation of the Green River basin ranges from marine strata of prodelta origin to marginal marine and nonmarine equivalents of delta-front and delta-plain-fluvial strata. Coal exploration drill holes, measured sections, and underground mine data have been analyzed to reconstruct the depositional setting of the Rock Springs Formation. Extensive sheet sandstones are inferred to be delta-front deposits reflecting the cuspate to arcuate geometry of wave-dominated deltaic deposits. Extensive coal deposits up to 22 ft (6.7 m) thick that developed on top of delta-front sandstones extend for 15 mi (24.1 km) along depositional dip, and 36 mi (58 km) along depositional strike. These coal deposits are referred to as type A coal seams. Coal deposits 1-17 ft (0.3-5.2 m) thick that developed in upper delta-plain-fluvial environments are less than 20 mi (32.2 km) in length. These deposits are referred to as type B coal seams. Type C seams are persistent, thin coal deposits 1-8 ft (0.3-2.4 m) thick, developed on top of delta-plain-fluvial deposits less than 25 mi (40.2 km) in length, and they mark the delta-lobe abandonment phase. Approximately 15 major coal zones exist in the Rock Springs Formation. The geometry of types A, B, and C reflects a genetic relationship to both deltaic and fluvial units in the marginal marine and nonmarine components of the Rock Springs Formation. A model for predicting coal-seam thickness and continuity is believed to be applicable to additional exploration in the Green River basin and in other Cretaceous coal-bearing basins in the Western Interior.

The eastern margin of the Kechika Graben in the vicinity of Muncho and Moose lakes, northeastern British Columbia, contains Middle Cambrian rift-related strata herein named the Mount Roosevelt Formation. The formation conformably overlies a quartzite package equivalent to the uppermost clastic unit of the informal late Early Cambrian Gataga group ( Bonnia – Olenellus zone) and is conformably overlain by a thick, unnamed carbonate sequence of Middle Cambrian age ( Plagiura – Poliella zone). The Mount Roosevelt Formation is subdivided into three members. The lowermost member is characterized by oöid-bearing siltstone and sandstone, interbedded with dolostone, limestone, and hematitic conglomerate. Conformably above this, the middle member is a thick sequence of polymict cobbly pebble conglomerate. The upper member includes karstified dolostone, calcareous-cemented conglomerate and sandstone, and limestone. Collectively the Mount Roosevelt Formation reflects alluvial fan delta progradation into a transgressive marine environment. Deposition occurred in an active fault-controlled basin, located on the eastern margin of the Kechika Graben adjacent to the Muskwa High. Basin initiation in the late Early Cambrian coincided with the reactivation of pre-existing regional faults. High rates of subsidence during the initial phase of extension were accommodated on these faults, which provided a locus for fan delta deposition. Continuing high rates of subsidence limited basinward fan delta development. Deposition of the formation ended with base-level transgression in the early Middle Cambrian that drowned the fan deltas and the adjacent Muskwa High and allowed development of the Kechika Trough above the older graben system.

Controls and evolution of fan delta systems in the Miocene Pohang Basin, SE Korea

An array of modern wetlands, including swamps, marshes, bogs, etc exists on nearly every continent. The wetlands range from essentially dry upland shrub-moss communities to forests which exist on a constantly submerged substrate. Some wetlands are common to arctic regions, others are found only in the tropics. Each wetland has developed a variable and fascinating assemblage of plant species that have adapted to the peculiar physical and chemical properties of their environment. The great variety of wetlands provides us with an opportunity to study an assortment of depositional settings, some of which are suitable analogs to ancient, coal-forming environments. Some wetlands, such as kettle swamps and bogs, or karst swamps and marshes may have occurred so infrequently in the past as to have been unimportant in coal formation. Other wetlands, such as back-barrier lagoon swamps, deltaic swamps, and inland river swamps have unquestionably been responsible for deposition of our most extensive coal deposits. An overview of modern wetlands illustrates the tremendous complexity of these plant communities, and dispells the idea that modern swamp/marsh deposits (i.e., peats) and, hence, coal deposits are simple. The physical and chemical compositions of peats and coal beds have changed with time, as different environments have dominated areas of the globe and plants have evolved in response to those environmental changes. The study of modern wetlands is receiving increased emphasis as End_Page 1682------------------------------ further comparison of modern and ancient deposits improves our means of mining and utilizing coal. End_of_Article - Last_Page 1683------------

This study aims to identify favorable oil–gas reservoir facies in the Chishan group of the Wubao fault zone (Gaoyou sag, Subei basin, China) using the methods of outcrops and cores observation, granularity analysis, scanning electron microscope, log data, etc. The results suggest that the Chishan group in the studied area mainly develops desert sedimentary system, and contains five kinds of facies from bottom to top, namely dry salt lake, aeolian sand, intermittent river, fan delta, and salt lake facies; the Chishan group was divided two members according to the lithology and a sedimentary cycle of base-level. The lower member of the Chishan group in the Wubao fault zone contained dry salt lake, intermittent river, and aeolian sand facies. The upper member of the Chishan group in the Chenbao area consisted mainly of aeolian sand. The southwestern Zhousong area contained (from east to west) a succession of aeolian sand, intermittent river, fan delta, and salt lake facies. Among these facies, aeolian sand was divided into aeolian sand dune, interdune, and aeolian sand sheet three sub-lithofacies. In the aeolian sand dune, the sand dune was a typical micro-lithofacies and had a scattered distribution. The fan delta had a bead-like distribution along the main fault, in which mainly underwater distributary channel and sand bank were developed. The sand bodies of the sand dune, underwater distributary channel, and sand bank were all well developed, and had average porosity values of >20%, meaning that they were favorable oil–gas reservoirs. The interdune sediments were fine-grained and had low porosity and permeability. Hence the reservoir properties of the interdune sediments were poor, and they could represent either fluid interlayers of reservoirs or source beds.

Based on the analysis of three-dimensional seismic data in Hongqi sag, it is clear that the structure of the depression is controlled by volcanic mechanism, controlled subsidence fault and secondary fault. The structure is complex. The structural framework of the residual basin changed greatly due to the multi-stage tectonic movements. It is not conducive to the understanding of the prototype and lithofacies paleogeography of the depression. Through the study of the recovery of the prototype basin in the key period, the basin prototype of different construction and transformation periods is constructed. The paleogeographic characteristics of lithofacies in different periods are determined. Then, combined with the analysis of single well facies, lake water advance and retreat and sediment supply conditions, the lithofacies paleogeographic characteristics of different periods are determined. The sedimentary period of Tamulangou formation developed a lithofacies paleogeographic pattern of coexistence of volcanic rocks, fan delta and lakes. During the sedimentary period of Tongbomiao formation, the lake basin develops. But the water body is shallow. The material source is sufficient. The fan delta shallow lake sedimentary assemblage is developed. During the deposition period of Nantun formation, the lake basin further expanded rapidly. The water body became deeper. The lake basin became larger. The fan delta shrank. It is fan delta lacustrine sedimentary assemblage. The sedimentary period of Damoguaihe - Yimin formation is a fan delta lacustrine sedimentary assemblage dominated by lacustrine deposits.

The palynology of ODP site 1165, Prydz Bay, East Antarctica: A record of Miocene glacial advance and retreat

The identification of metallic elements in airborne particulate matter derived from fossil fuels at Puertollano, Spain

Coal deposition in the Noric Depression (Eastern Alps): raised and low-lying mires in Miocene pull-apart basins

Peloidal and oolitic limestones on Cablac Mountain in East Timor contain small calcite-cemented agglutinated and porcelaneous foraminifera that place these limestones in the Triassic or Lower Jurassic, in contrast to the Lower Miocene as previously mapped. An Early Jurassic (Sinemurian-Pliensbachian) age is indicated for some of the limestone by the presence of Meandrovoluta asiagoensis Fugagnoli and Rettori, Everticyclammina praevirguliana Fugagnoli and a palynomorph assemblage. The age of other limestones on the mountain is identified broadly as Late Triassic to Early Jurassic, based on the occurrence of Duotaxis metula Kristan. In basinal facies of the nearby Wai Luli Valley, Gsollbergella spiroloculiformis (Oraveczne Scheffer), palynomorphs, a brachiopod and halobiid bivalves indicate a Late Triassic (Carnian) age for a transported foraminiferal assemblage associated with peloids, ooids and Duotaxis and Siphovalvulina characteristic of carbonate-bank deposits. This occurrence suggests that carbonate banks were developed locally on submerged topographic highs in seas that flooded interior-rift basins in this part of Gondwana and that a complex facies array of deep-water muds, deltaic sands, and carbonate shoals were present in the basins. Taxonomic assessment of Triassic and Early Jurassic species previously placed in Tetrataxis suggests that these are better accommodated in Duotaxis , and some species placed in Trochammina are transferred to Siphovalvulina . The distinction between Duotaxis and Siphovalvulina , as now understood, rests on the shape of adult chambers.

Summary Lacustrine carbonates are dominantly biogenic or bio-induced precipitates. While lake basinal carbonates may be modelled in terms of hydrological factors, marginal lacustrine carbonate facies show great variability. At low-energy lake margins, bioturbated micrites dominate. At high-energy margins, lenticular carbonate sands and coated grains are developed. Lakes with low-gradient (‘ramp’-type) margins show dominantly marginal lacustrine facies; lakes with high-gradient (‘bench’-type) margins display greater development of basinal facies. Progradation of lake margins commonly leads to the deposition of regressive sequences, which may be modelled in four categories according to the morphology and energy of lake margins. These categories are: low-energy ‘bench’; high-energy ‘bench’; low-energy ‘ramp’; high-energy ‘ramp’. Carbonate deposition in lakes is sensitive to climatic and tectonic influences and dependent upon lake hydrology and morphology. Climate controls the rate and nature of biogenic productivity, influences chemical weathering, erosion, and runoff rates in the catchment area, and thus determines carbonate supply. Lake carbonates may form in a variety of structural settings, especially where the catchment area geology is dominated by carbonates or calcic basement rocks. Tectonic controls determine the rate of subsidence and thus influence sedimentation rates. High-gradient, bench-type lake margins commonly occur at faulted boundaries of rapidly subsiding rift basins where subsidence exceeds sedimentation. At more slowly subsiding rift borders, in larger strike-slip basins, in foreland settings, and in sag basins, low-gradient, ramp-type lake margins dominate. Tectonic factors also influence patterns of continental drainage and the location of clastic sediment input, each of which condition facies distributions within lake basins. Carbonate facies are deposited in areas of low alluvial clastic supply, either in central basin areas away from major bounding faults or prograding thrust fronts, or at basin margins starved of clastic input. Carbonate lacustrine systems may have hydrocarbon potential. Good source rock prospects occur in deeper, stratified lakes, where anoxic bottom conditions and low detrital input permit the deposition of laminated organic-rich sediments. Reservoirs are more problematic; although reservoirs with primary and secondary porosity may occur in lake marginal bioherms and shoals, most reservoir potential is likely to occur in intercalated alluvial or sublacustrine clastic facies. The extreme lateral variability of lacustrine systems, particularly in rift and strike-slip basins and in high-energy settings, may make accurate prediction of source rock and reservoir facies distributions difficult.

A relatively small range of lacustrine-facies associations record the complexly contingent interactions of a wide range of physical, chemical, and biological processes (climate, tectonics, sediment supply, vegetation, landscape evolution). Each lacustrine-facies association contains fluvial, lake-plain, lake margin, and lake center strata with characteristic hydrocarbon reservoir potential. The accumulation of these lacustrine-facies associations and their potential hydrocarbon reservoirs arise from interactions of typical ranges of rates of potential accommodation and sediment plus water supply and can be interpreted genetically as overfilled, balanced-filled, and underfilled lake-basin types. Fluvial-lacustrine lacustrine-facies associations (interpreted as forming in overfilled lake basins) generally contain reservoirs that are best developed in aggradationally stacked highstand clastic shoreline strata and occasionally in skeletal carbonate or charophytic algal lithosomes or in lowstand incised valley fills and lake floor fans (basinally restricted turbidite and mass flow deposits). These reservoirs tend to have low vertical permeability (Kv) because flooding surfaces are generally marked by decreased input of coarse sediment and increased subsidence. They have the lowest average net reservoir:gross interval of the three lacustrine-facies associations. They do, however, have the highest average porosity and permeability and contain the largest overall reserves, mainly in lake-plain fluvial strata. Fluctuating profundal lacustrine-facies association (balanced-filled lake basins) have reservoir facies that include lake floor fans, incised valley fills, and shoreline clastics or carbonates deposited during transgressions and highstands. These reservoirs tend to have the smallest lateral extent and lowest average recovery factor of the three lacustrine-facies associations; (based on reservoir and fluid properties), but do have good vertical and horizontal permeability (Kh) in highstand and transgressive systems tracts and the best Kv of all the lake-basin types. Evaporative lacustrine-facies associations (underfilled lake basins) contain reservoir facies that are best developed in transgressive sheetflood clastics, early highstand fluvial channels, and late highstand shoreline carbonate grainstones. Early carbonate and evaporite cements are common in these reservoirs, and there tends to be a wide lateral displacement of highstand from lowstand systems tracts. They do, however, have the best Kh (because of common erosion that enhances lateral connectivity) as well as the thickest net pay of all the lake-basin-type reservoirs (as they tend to occur at relatively large potential accommodation rates). Associated fluvial styles among the lacustrine-facies associations (lake-basin types) appear to vary systematically, as a function of sediment plus water supply relative to potential accommodation rates: perennial, high sinuosity streams are most common in overfilled lake basins, intermittent to perennial low-sinuosity streams in balanced fill, and a wide range from ephemeral sheetflood or multithread braided streams to perennial high-sinuosity streams in underfilled lake basins. Observations indicate that these associations of hydrocarbon reservoir and seal play elements occur in a wide variety of tectonic settings and ages, from continental rift to convergent foreland basins of the Cambrian to Holocene. Continued success in economic discovery and efficient recovery depend upon continued testing and elaboration of these concepts and a deeper understanding of the essential processes controlling deposition of lacustrine strata.

A detailed chronostratigraphic framework established by the mapping of tephra key beds and application of oxygen isotopic data allows assessment of the synchroneity and diachroneity of depositional systems formed in coastal and deep-water environments. This framework also allows estimation of the timing of active delivery of coarse-grained sediments beyond the shelf margin in relation to relative sea-level changes. The depositional processes of deep-water massive sandstones (DWMSs) are still enigmatic; their formation is a result of active delivery of sands in association with the supply of organic carbon into deep-water environments. DWMSs are also important as reservoirs for hydrocarbon explorations. This study investigated the origins of DWMSs in the upper Umegase, Kokumoto, and Chonan formations (in ascending order) of the Pleistocene Kazusa Group on the Boso Peninsula, central Japan. Each formation contains several packets of DWMSs that are interpreted to have formed in response to the progradation of gravelly shelf-margin deltas or fan deltas during the falling and lowstand stages of relative sea-level changes controlled primarily by glacioeustasy. The development of DWMSs and associated sandstone beds is interpreted to have been induced by hyperpycnal flows, in association with sediment gravity flows that were initiated by breaching and/or collapse of sandy substrates on the shelf-margin deltas or fan deltas. The timings of the initial and final deposition of the packets vary within and between the formations, and are considered to have been controlled by the interaction between allogenic and autogenic processes operating in the gravelly shelf-margin deltas or fan deltas. A muddy horizon that contains the Lower–Middle Pleistocene Subseries boundary (the base of the Chibanian Stage) in the Kokumoto Formation is also underlain and overlain by the packets and represents a deposit formed in a condensed section in an upper slope environment. This depositional setting may have favored the development of the Global Boundary Stratotype Section and Point (GSSP) for the Lower–Middle Pleistocene Subseries boundary in the formation.