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To better understand the sedimentary facies of tide‐dominated deltas, a core dataset from the Ba Lai palaeochannel in the Mekong River Delta was obtained and studied. Nine sedimentary facies were identified and interpreted as representing the Late Holocene evolution of the Ba Lai palaeochannel, including its pre‐abandonment and post‐abandonment phases, as well as pre‐channel phases. The channel formed at 2.6 ka as a distributary channel connected to the deltaic network and was abruptly abandoned and rapidly infilled with sediment at 0.7 ka. The channel deposits are up to ca 11 m thick and overlie shelfal shell layers, which, in turn, overlie Mid‐Holocene and Pleistocene deposits. The active‐channel fill and mouth‐bar deposits consist of sand and mud with cyclical patterns, bidirectional lenses and abundant mud layers, suggesting deposition mainly driven by river and tidal processes. The abandoned‐channel fill consists entirely of organic‐rich mud, suggesting a predominance of tidal processes. Other sedimentary facies include tidal‐flat and marsh deposits; they mostly consist of mud and formed in shallow to subaerial areas near the channel margins or on barforms. Depending on the exact location of the core in this depositional setting, three possible stratigraphic successions and facies models are presented herein. Near channel margins, the deposits show an upward gradual change from heterolithic to mud with a well‐developed fining‐upward trend. Away from the channel margins, the deposits show an upward sharp change from heterolithic to mud due to the channel abandonment. The mouth‐bar‐area facies model shows an upward gradual change from heterolithic to heterolithic/sand to mud deposits with a coarsening‐upward to fining‐upward trend. Although differences among systems likely exist, the authors suggest that the sedimentary facies described in this study and the resulting facies models should be used to better understand tide‐dominated deltaic systems and to improve their interpretation in the geological record. [ABSTRACT FROM AUTHOR]

Lake‐delta deposits in low‐accommodation conditions are only a few metres thick and in some cases non‐existent. Fluvial channels occur in many cases directly on top of fine‐grained lacustrine deposits with delta deposits apparently missing. The geomorphology and stratigraphy of modern deltas in Lake Eyre, Australia, and Lake Chad in Africa indicate that delta shorelines can develop in lakes, but in many cases build out into low‐accommodation settings due to highly dynamic lake‐water levels. This work suggests that low‐accommodation is critical in the development of lacustrine delta deposits and that high (frequency and magnitude) rates of lake‐level change result in 'telescoping' deltas, the deposits of which are thin but extensive. The telescopic deltas have conformable beds, but with abrupt vertical facies changes; this apparent stratigraphic contradiction is the result of long horizontal distance translation of the depositional system. Details of two lacustrine units, in Uinta Basin in the USA and Junggar Basin in China, both of which show characteristics of telescoping, are used to develop a process based stratigraphic model for the deposits of such lake deltas. Lacustrine facies comprise cross‐stratified, ripple cross‐laminated, structureless or graded and sharp‐based sandstone beds, mudstone (structureless, laminated, rippled, rich in organic content), carbonate mudstone, ooid packstone and stromatolites. Three facies associations are critical for lake delta stratigraphy: channelized distributary deposits that occur in the delta topset; lake plain deposits that represent the fluvial overbank deposits and the subaerially exposed (at low lake level) lake deposits; and fine‐grained, lacustrine deposits. A key corollary of the proposed low‐gradient, telescoping lacustrine delta model is that broad and shallow channels dominate the system, but that decimetre to metre thick, gently dipping delta‐front beds form subtle deposits along the margins of the lakes. These delta depocentres migrate basinward and landward at high rates (tens of kilometres each year), building thin (metres) but laterally extensive (tens of kilometres) sandstone units through multiple transgression–regression cycles. [ABSTRACT FROM AUTHOR]

Ephemeral fluvial systems are commonly associated with arid to semi‐arid climates. Although their complex sedimentology and depositional settings have been described in much detail, depositional models depicting detailed lateral and vertical relationships, and interactions with coeval depositional environments, are lacking compared to well‐recognized meandering and braided fluvial systems. This study critically evaluates the applicability of current models for ephemeral fluvial systems to an ancient arid fluvial example of the Lower Jurassic Kayenta Formation of the Colorado Plateau, USA. The study employs detailed sedimentary logging, palaeocurrent analysis and photogrammetric panels across the regional extent of the Kayenta. A generic model that accounts for the detailed sedimentology of a sandy arid ephemeral fluvial system (drawing upon both ancient and geomorphological studies) is developed, along with analysis of the spatial and temporal interactions with the aeolian setting. Results show that the ephemeral system is dominated by laterally and vertically amalgamated, poorly channelized to sheet‐like elements, with abundant upper flow regime flat beds and high sediment load structures formed between periods of lower flow regime conditions. Through interaction with a coeval aeolian system, most of the fluvial deposits are dominated by sand‐grade sediment, unlike many modern ephemeral fluvial systems that contain a high proportion of conglomeratic and/or finer grained mudstone and siltstone deposits. During dominantly fluvial deposition, high width to thickness ratios are observed for channelized and sheet‐like elements. However, with increasing aridity, the aeolian environment becomes dominant and fluvial deposition is restricted to interdune corridors, resulting in lower width to thickness ratio channels dominated by flash‐flood and debris‐flow facies. The data presented here, coupled with modern examples of ephemeral systems and flood regimes, suggest that ephemeral flow produces and preserves distinctive sedimentological traits that can not only be recognized in outcrops, but also within core. [ABSTRACT FROM AUTHOR]

Depositional facies have been hypothesized to be linked to sequence stratigraphic positions. Also, shoreline systems are built by mixed processes, including rivers, storms, fair‐weather waves and tides. Resolving the complexity of shoreline deposition requires detailed quantitative facies analysis with particular attention to heterolithic successions. In this study, 71 sections in a 130 km long outcrop belt of the Cretaceous Gallup Formation in the north‐west of the San Juan Basin were measured. Five major facies associations were identified using sedimentological and iconological interpretations, including offshore shelf, non‐deltaic shoreline sandstones, deltas, coastal bayline and fluvial. Each facies association also comprises subordinate facies. Depositional facies interpretations are placed in a high‐resolution sequence stratigraphic framework that allows for reconstructions of the palaeogeography of individual parasequence sets that demonstrate temporal and spatial evolution of facies associations and depositional processes. The results show that the Gallup is a mixed‐process‐controlled depositional system with fair‐weather and storm‐wave dominance, river influence and tide‐effect, contrasting with previous interpretations of a solely fair‐weather wave‐dominated environment. Depositional processes and the resultant facies change with sequence stratigraphic positions in response to relative sea‐level changes – particular facies are only deposited in certain systems tracts. Distinction and transition between non‐deltaic shorefaces and wave‐dominated deltas have also been documented in this study. Non‐deltaic shorefaces are characterized by homogeneous sandstones with a wide‐range bioturbation index and the absence of mudstones. Wave‐dominated deltas are subject to river influence and contain prodelta facies. This study shows the importance of detailed facies analysis with high‐resolution sequence stratigraphic control using outcrops for documenting sedimentary processes of shallow marine shoreline systems. [ABSTRACT FROM AUTHOR]

The interaction of river and marine processes in the fluvial to marine transition zone fundamentally impacts delta plain morphology and sedimentary dynamics. This study aims to improve existing models of the facies distribution, stratigraphic architecture and preservation in the fluvial to marine transition zone of mixed‐process deltas, using a comprehensive sedimentological and stratigraphic dataset from the Middle Miocene Lambir Formation, Baram Delta Province, north‐west Borneo. Eleven facies associations are identified and interpreted to preserve the interaction of fluvial and marine processes in a mixed‐energy delta, where fluvial, wave and tidal processes display spatially and temporally variable interactions. Stratigraphic successions in axial areas associated with active distributary channels are sandstone‐rich, comprising fluvial‐dominated and wave‐dominated units. Successions in lateral areas, which lack active distributary channels, are mudstone‐rich, comprising fluvial‐dominated, tide‐dominated and wave‐dominated units, including mangrove swamps. Widespread mudstone preservation in axial and lateral areas suggests well‐developed turbidity maximum zones, a consequence of high suspended‐sediment concentrations resulting from tropical weathering of a mudstone‐rich hinterland. Within the fluvial to marine transition zone of distributary channels, interpreted proximal–distal sedimentological and stratigraphic trends suggest: (i) a proximal fluvial‐dominated, tide‐influenced subzone; (ii) a distal fluvial‐dominated to wave‐dominated subzone; and (iii) a conspicuously absent tide‐dominated subzone. Lateral areas preserve a more diverse spectrum of facies and stratigraphic elements reflecting combined storm, tidal and subordinate river processes. During coupled storm and river floods, fluvial processes dominated the fluvial to marine transition zone along major and minor distributary channels and channel mouths, causing significant overprinting of preceding interflood deposits. Despite interpreted fluvial–tidal channel units and mangrove influence implying tidal processes, there is a paucity of unequivocal tidal indicators (for example, cyclical heterolithic layering). This suggests that process preservation in the fluvial to marine transition zone preserved in the Lambir Formation primarily records episodic (flashy) river discharge, river flood and storm overprinting of tidal processes, and possible backwater dynamics. [ABSTRACT FROM AUTHOR]

Due to difficulties in correlating aeolian deposits with coeval marine facies, sequence stratigraphic interpretations for arid coastal successions are debated and lack a unifying model. The Pennsylvanian record of northern Wyoming, USA, consisting of mixed siliciclastic-carbonate sequences deposited in arid, subtropical conditions, provides an ideal opportunity to study linkages between such environments. Detailed facies models and sequence stratigraphic frameworks were developed for the Ranchester Limestone Member (Amsden Formation) and Tensleep Formation by integrating data from 16 measured sections across the eastern side of the Bighorn Basin with new conodont biostratigraphic data. The basal Ranchester Limestone Member consists of dolomite interbedded with thin shale layers, interpreted to represent alternating deposition in shallow marine (fossiliferous dolomite) and supratidal (cherty dolomite) settings, interspersed with periods of exposure (pedogenically modified dolomites and shales). The upper Ranchester Limestone Member consists of purple shales, siltstones, dolomicrites and bimodally cross-bedded sandstones in the northern part of the basin, interpreted as deposits of mixed siliciclastic-carbonate tidal flats. The Tensleep Formation is characterized by thick (3 to 15 m) aeolian sandstones interbedded with peritidal heteroliths and marine dolomites, indicating cycles of erg accumulation, preservation and flooding. Marine carbonates are unconformably overlain by peritidal deposits and/or aeolian sandstones interpreted as lowstand systems tract deposits. Marine transgression was often accompanied by the generation of sharp supersurfaces. Lags and peritidal heteroliths were deposited during early stages of transgression. Late transgressive systems tract fossiliferous carbonates overlie supersurfaces. Highstand systems tract deposits are lacking, either due to non-deposition or post-depositional erosion. The magnitude of inferred relative sea-level fluctuations (>19 m), estimated by comparison with analogous modern settings, is similar to estimates from coeval palaeotropical records. This study demonstrates that sequence stratigraphic terminology can be extended to coastal ergs interacting with marine environments, and offers insights into the dynamics of subtropical environments. [ABSTRACT FROM AUTHOR]

Extant models predict delta front environments down-drift of river mouths as unfavourable for organisms because of the physico-chemical stresses caused by sediment and fresh water influx. This study, however, finds evidence for near-optimal living conditions down-drift of contemporaneous mouth bars and distributary channels, as well as at the tops of abandoned lobes, in part of the asymmetrical 'Notom Delta' complex of the Ferron Sandstone (Turonian, south-eastern Utah, USA). Presented herein is a sedimentological and ichnological model using thirty-two detailed measured sections along a 16 km transect through two continuously exposed, ca 10 m thick allomembers containing delta front, mouth bar and distributary channel facies. Azimuths from sedimentary structures show south-eastward deflection of near-shore palaeocurrents relative to the inferred north-south shoreline, as well as minor reversal of flow. Two end-member trace fossil suites are recognized in delta front sandstones: (i) a stressed suite of low abundance, low diversity, diminutive traces reflecting mobile deposit feeding, resting and locomotion behaviours; and (ii) a comparatively unstressed, high abundance, moderate diversity suite with a regular, heterogeneous distribution of deep, vertical or U-shaped suspension-feeding burrows which, in places, thoroughly homogenize the sandstones. The down-drift side of the delta was colonized by suspension feeders during seasonal reversal of the seaway gyre when mud plumes were swept northward or when riverderived nutrients were sufficiently concentrated relative to fresh water and sediment input. During normal seaway circulation, very high sedimentation rates and mud-laden, wave-dampened waters down-drift of the river mouths heightened the preservation potential of the pervasively bioturbated facies. Up-drift of the river mouths, these bioturbated facies were either not preserved or not developed until the lobe was abandoned. This alternative model for delta planform asymmetry contributes to the refinement of facies models for deltaic systems and provides a framework for predicting the distribution of bioturbation-enhanced porosity and permeability in lobe-deflected deltas. [ABSTRACT FROM AUTHOR]

Tectonic forcing of stratigraphic architecture is likely in foreland basins. Tectonic driving forces are increasingly being invoked to explain stratigraphic patterns in the Cretaceous Western Interior Seaway Basin of North America, yet the evidence is largely circumstantial, and the details of driving forces remain elusive. In this paper I show direct stratigraphic evidence for syndepositional growth of a structural arch with at least 50 m of relief during accumulation of the upper Turonian Ferron Sandstone in south-central Utah, United States. Progressive growth of the arch was superimposed on several high-frequency stratal cycles that were driven by a more regionally extensive process (geodynamic or eustatic) and that produced laterally amalgamated sandstone bodies in a depositional strike-parallel orientation (north-south). All of this stratigraphy was then truncated by a more or less planar erosion surface (sequence boundary) that can be traced physically over at least 67 km north-south. This surface was later tilted northward, such that the upper member of the Ferron Sandstone thins progressively southward from 50 to 10 m over 67 km. The facies juxtapositions revealed by the Ferron Sandstone could, if seen in exposure of limited lateral extent, be wrongly interpreted as recording regionally extensive relative sea-level drops and potentially used in error as evidence for substantial eustatic sea-level falls during the Turonian. The folding and tilting documented in this study can be clearly attributed to geodynamic and/or tectonic driving forces, likely related to migration of a forebulge. [ABSTRACT FROM AUTHOR]

Abstract: Recent research in eastern Australia has established that rather than being a single, long-lived epoch, the late Palaeozoic Ice Age comprised a series of glacial intervals each 1–8million years in duration, separated by non-glacial intervals of comparable duration. In order to test whether the glacial events recognized in New South Wales and Queensland have broader extent, we conducted a reappraisal of the Parmeener Supergroup of Tasmania, southeast Australia. A facies analysis of the Pennsylvanian to Permian section was carried out, allowing rationalization of the succession into four recurrent facies associations: a) glacigenic facies association, restricted to the basal Pennsylvanian/earliest Permian Wynyard Formation and correlatives, b) glacially/cold climate-influenced to open marine shelf facies association, which accounts for large parts of the Permian succession, c) deltaic facies association, which specifically describes the Lower Permian “Lower Freshwater Sequence” interval, and d) fluvial to estuarine facies association, which specifically addresses the Upper Permian Cygnet Coal Measures and correlatives. Indicators of sediment accumulation under glacial influence and cold climate are restricted to four discrete stratigraphic intervals, all of which indicate that glaciation was temperate in nature. The lowermost of these, incorporating the basal Wynyard Formation and its correlatives, and overlying Woody Island Formation, shows evidence of proximal glacial influence (subglacial, grounding-line fan and ?fjordal facies), and is likely a composite of one or more Pennsylvanian glacial event(s) and an earliest Permian (Asselian) glacial. The second, of late Sakmarian to early Artinskian age, comprises an initial more proximal ice-influenced section and an overlying more distal ice-influenced interval. The third (Kungurian to Roadian) and fourth (Capitanian) intervals are both distal glacimarine records. The four intervals are of comparable age to glacials P1–P4, respectively, recognized in New South Wales and Queensland (notwithstanding apparent discrepancies of <2million years in age), and display similar facies characteristics and vertical contrasts to those intervals. Accordingly, it is concluded that the late Palaeozoic stratigraphy of Tasmania preserves a glacial/cold climate record correlatable to that of mainland eastern Australia, lending support to the hypothesis that these events were widespread across this portion of Gondwana. [Copyright &y& Elsevier]

The Lower Permian Wasp Head Formation (early to middle Sakmarian) is a ∼95 m thick unit that was deposited during the transition to a non-glacial period following the late Asselian to early Sakmarian glacial event in eastern Australia. This shallow marine, sandstone-dominated unit can be subdivided into six facies associations. (i) The marine sediment gravity flow facies association consists of breccias and conglomerates deposited in upper shoreface water depths. (ii) Upper shoreface deposits consist of cross-stratified, conglomeratic sandstones with an impoverished expression of the Skolithos Ichnofacies. (iii) Middle shoreface deposits consist of hummocky cross-stratified sandstones with a trace fossil assemblage that represents the Skolithos Ichnofacies. (iv) Lower shoreface deposits are similar to middle shoreface deposits, but contain more pervasive bioturbation and a distal expression of the Skolithos Ichnofacies to a proximal expression of the Cruziana Ichnofacies. (v) Delta-influenced, lower shoreface-offshore transition deposits are distinguished by sparsely bioturbated carbonaceous mudstone drapes within a variety of shoreface and offshore deposits. Trace fossil assemblages represent distal expressions of the Skolithos Ichnofacies to stressed, proximal expressions of the Cruziana Ichnofacies. Impoverished trace fossil assemblages record variable and episodic environmental stresses possibly caused by fluctuations in sedimentation rates, substrate consistencies, salinity, oxygen levels, turbidity and other physio-chemical stresses characteristic of deltaic conditions. (vi) The offshore transition-offshore facies association consists of mudstone and admixed sandstone and mudstone with pervasive bioturbation and an archetypal to distal expression of the Cruziana Ichnofacies. The lowermost ∼50 m of the formation consists of a single deepening upward cycle formed as the basin transitioned from glacioisostatic rebound following the Asselian to early Sakmarian glacial to a regime dominated by regional extensional subsidence without significant glacial influence. The upper ∼45 m of the formation can be subdivided into three shallowing upward cycles (parasequences) that formed in the aftermath of rapid, possibly glacioeustatic, rises in relative sea-level or due to autocyclic progradation patterns. The shift to a parasequence-dominated architecture and progressive decrease in ice-rafted debris upwards through the succession records the release from glacioisostatic rebound and amelioration of climate that accompanied the transition to broadly non-glacial conditions. [ABSTRACT FROM AUTHOR]

Recent work on the Late Palaeozoic Ice Age in eastern Australia has shown the Joe Joe Group in the eastern Galilee Basin, Queensland, to be of critical importance as it is one of few records of Pennsylvanian glacial activity outside South America. This paper presents detailed sedimentological data, from which the Late Palaeozoic environment of the region is reconstructed and which, consequently, allows for robust comment on the broader Gondwanan glaciation. The Jericho Formation, in the lower Joe Joe Group, was deposited in an active extensional basin in lacustrine to fluvial environments, during the mid-Namurian to early Stephanian. The region experienced a cool climate during this time, and polythermal mountain or valley-type glaciers periodically advanced into the area from highlands to the north-east. The Jericho Formation preserves a suite of proglacial to terminal glacial facies that is characterized by massive and stratified diamictites deposited from debris flows, massive and horizontally laminated conglomerates and sandstones deposited from hyperconcentrated density flows, laminated siltstones with outsized clasts and interlaminated siltstone/conglomerate deposited through ice-rafting into lakes, and sedimentary dykes and breccias deposited through overpressurization of groundwater beneath permafrost. Non-glacial facies are dominated by fluvial sandstones and lacustrine/overbank siltstones. The glacigenic rocks of the Jericho Formation are confined to discrete packages, recording three separate glacial advances during the latest Namurian to late Westphalian. This arrangement is consistent with the temporal distribution of glacigenic rocks from around the remainder of Australia and Gondwana, which supports the theory that glacial deposits occurred in discrete intervals. The Joe Joe Group is a key succession in the world in this context as, at this time, eastern Australia provides the only unequivocal evidence of a Namurian/Westphalian glaciation outside South America. The continuous record of sedimentation through the Pennsylvanian and Early Permian is indicative of significant warming between glacial intervals, which is difficult to reconcile with the development of long-lived, cold-based ice sheets across the supercontinent. [ABSTRACT FROM AUTHOR]

Abstract: The Late Permian Betts Creek Beds form a succession of coal-bearing alluvial-coastal plain sediments in a basin marginal setting within the northeastern Galilee Basin, Queensland, Australia. The unit is ∼50–60 m in thickness at Porcupine Creek National Park where outcrop is laterally continuous for several kilometers. Eight facies have been identified within the formation and can be grouped into 2 facies associations: (A) channel deposits and (B) floodbasin deposits. The channel association consists of conglomerate (A1) and trough cross-bedded multistorey sandstone facies (A2), both interpreted as deposits of low-sinuosity river systems, tidally influenced fluvial channels (A3), interbedded sandstone and siltstone (A4) interpreted as the abandonment fill of the alluvial systems, and diamictite (A5) interpreted as debris flows. The floodbasin facies association is composed of sandy siltstone (B1; proximal–distal floodbasin), carbonaceous siltstone (B2; mire), and bioturbated siltstone (B3; estuarine) facies. The overall sediment body architecture can be resolved into 6 unconformity-bounded cycles interpreted as sequences in the genetic sense, which are sheet-like in geometry and, in general, consist of amalgamated multistorey, multilateral braided fluvial deposits at the base overlain by extensive sheet-like overbank mudstones, carbonaceous shales, and coals. Sea-level change is interpreted as the primary control on the sequence architecture of the formation, while the internal stratigraphic architecture, however, varies between sequences and is a function of a combination of sea level, tectonic, and autogenic controls. [Copyright &y& Elsevier]

The term "cyclothem" was coined by Wanless and Weller (1932) to characterize a repetitive stratigraphic motif in the Pennsylvanian succession of the Illinois Basin, central USA, and it subsequently became popular among geologists as a general term for similarly repetitive successions worldwide. Although use of the term has become somewhat indiscriminate in the interim, it is here considered best reserved for the distinctive stratal rhythms characteristic of the late Palaeozoic in the palaeotropical realm of Laurussia, recording repeated alternation of marine and nonmarine depositional conditions. Cyclothems comprise arrays of terrigenous clastic, organic, and chemical/biochemical lithologies that record accumulation mainly on slowly-subsiding platforms and ramps, under limited accommodation and limited sediment supply, often strongly seasonal tropical and subtropical climates, and forcing by repeated, large-magnitude excursions of sea level. A spectrum of variation is recognized, from carbonate-mudrock-dominated variants at one extreme to coarse clastic-dominated styles at the other. Cyclothems can be rationalized as depositional sequences which are thin (metres to a few tens of metres), condensed, incomplete in terms of systems tracts, and top-truncated. Given their demonstrated widespread extent, cyclothems have been attributed by many researchers to forcing by eustatic sea-level fluctuations, and a variety of evidence suggests they correlate to 100 kyr glacial cycles on Gondwana. By analogy with Quaternary 100 kyr glacial cycles, much of the time in a cycle was taken up by a protracted, complex drawdown of sea-level, during which valleys and channels were excavated and interfluves were pedogenically modified. Most of the depositional record of cyclothems probably formed in the relatively short interval following lowstand/glacial maximum when sea-level rose to its interglacial maximum. Analysis of cyclothemic successions can contribute to a fuller understanding of the magnitude of sea-level excursions and palaeoclimatic changes during the late Palaeozoic, and can help to pinpoint the timing of key events such as the main onset of the late Palaeozoic Ice Age. • Cyclothems are best considered as repeated alternations of facies representing marine submergence and nonmarine exposure • Cyclothems formed under limited accommodation and coarse sediment supply on palaeotropical shelves and ramps under strong forcing from fluctuating sea level • Most of the time (~80%) encompassed in a cyclothem was likely non-depositional, by analogy with Quaternary 100 kyr glacial cycles • Cyclothems can be useful for elucidating ancient palaeoenvironmental changes such as the onset and termination of ice ages. [ABSTRACT FROM AUTHOR]

The late Permian Bainmerdart Coal Measure form part of the Permo-Triassic Amery Group, which crops out in the Beaver Lake area of the Northern Prince Charles Mountains, MacRobertson Land, Antarctica. The exposed strata are believed to have formed in graben or half-graben sub-basins on the western edge of the Lambert Graben, a major failed rift system. Sedmentological analysis has revealed that these rocks formed in alluvial environments in which swiftly flowing rivers of low sinuousity (represented by Facies A1 and A2) flowed northward down the axis of the basin, and were associated with water logged floodbasin and peat-forming wetlands (Facies B1-B4). A third Facies Association (comprising Facies C1-C3), interpreted as the deposits of lake floor and delta environments, is exclusively developed within a distinctive, fine-grained interval here named the Dragon's Teeth Member. The proportion of Association B facies within the succession increases markedly above the level of the Dragon's Teeth Member (at about 300 m above the base of the formation). Flat, low-angle and undulatory bedding structures preserved within channel deposits are suggestive of sediment deposition in flow conditions which were often critical or supercritical. Presence of massive and chaotic intervals of sandstone further implies some deposition from high-concentration aqueous flows. Alluvial channel bodies show evidence of incision into underlying substates, both during inititation and at laster stages in channel belt construction. The lack of interfingering between channel deposits and coals suggests that thick peats formed only in areas and at times of minimal clastic sediment supply. Analysis of well-developed cyclicity within the coal measures suggests that the dominant control on sequence architecture was climatic, related to precessional Milankovitch fluctuations of c. 19-kyr prediocity. Cycles began abruptly with the deposition of coarse-grained material in high-energy alluvial... [ABSTRACT FROM AUTHOR]

To study the stratal stacking patterns and controls on coal accumulation in a lowland alluvial plain, coastal plain, and shallow-marine setting, the depositional facies, sequence stratigraphy, and paleogeography of the Carboniferous–Permian strata in the Anyang-Hebi (Anhe) coalfield, Henan Province, northern China were analyzed based on borehole cores. Ten facies were grouped into four facies associations, which represent alluvial plain, delta plain, delta front and prodelta, and offshore marine depositional environments. Ten sequences (S1 to S10, in ascending order) were defined on the basis of vertical facies stacking patterns. Sequences S1–S3, of Moscovian to early Asselian age, are composed mainly of offshore marine carbonate and mudstone, prodelta and delta front mudstone and sandstone, and delta plain sandstone, mudstone and coal. Sequences S4–S9, late Asselian to Wuchiapingian in age, consist of delta plain sandstone, mudstone and coal. Sequence S10, corresponding to the Changhsingian stage, is composed mainly of alluvial plain sandstone and mudstone. From S1 to S10, the Anhe coalfield experienced an environmental evolution from offshore marine, prodelta and delta front through delta plain to alluvial plain environments, an evolution from a low-accommodation to a high-accommodation setting, and a paleoclimatic change from humid to semi-arid conditions. Coal accumulation was controlled by a combination of relative sea-level fluctuation, paleoclimate and paleogeography. The cyclothemic nature of S2, including presence of parasequences, and the significant sea-level fall interpreted at the base of S4 may be related to Gondwanan ice dynamics in the late Carboniferous–early Permian. The thick coals are concentrated in the transgressive systems tracts of S2 and S4. The results of this study provide new insights into the environmental evolution of Carboniferous–Permian lowland alluvial plain, coastal plain and shallow-marine successions of the northern subtropical paleolatitudes and the controls on coal deposits in North China. • The Anhe coalfield is preserved with Carboniferous-Permian successions. • The paleoenvironment changes from offshore marine through delta to alluvial plain. • From S1 to S10, the paleoclimate changes from humid to semi-arid condition. • The S2 and S4 are related to two episodes of glaciations of the Late Paleozoic. • The sea-level fluctuations related to Gondwanan glaciations controls coal deposits. [ABSTRACT FROM AUTHOR]