Distributive Fluvial System Research Articles

Testing the fidelity of zircon as a provenance indicator in fluvial‐fan successions: An example from the Palaeogene Colton Formation, Central Utah, USA

AbstractThe stratigraphic, spatial and temporal variability of detrital zircon age populations in continental sedimentary successions is a critical tool in understanding palaeodrainage networks and how these systems distributed detritus within sedimentary basins. However, multiple factors, such as variations in sediment‐transport processes, the scale of the depositional environment and the architecture of the sedimentary succession are often overlooked in detrital zircon studies. This article presents detrital zircon U–Pb geochronology from the fluvial‐dominated Colton Formation in the western Uinta Basin (Utah, USA) to assess the system's provenance and evolution. Significant differences in zircon age populations between the Colton Formation and the overlying Green River Formation suggest a reorganisation of the source‐to‐sink system during the transition between the two lithostratigraphic units. Notably, detrital zircon age spectra are not homogeneous across the Colton Formation, therefore physical morphometric parameters were used to verify the possible influence of selective bias during sediment transport. These data reveal that a relatively finer‐grained population of Precambrian, and to a less extent Mesozoic, zircon grains were affected by hydraulic sorting during transport, resulting in a greater relative abundance of older zircon grains in the distal reaches of the distributive fluvial system, whose basinward decrease in competence would have increased the relative proportion of finer zircon fractions in sandstones. Furthermore, there are different trends in the distributions of zircon age populations relative to their stratigraphic position, highlighting the complex architecture of the fluvial palaeo‐fan. The spatial and stratigraphic variability of provenance signals in fluvial‐fan successions must be carefully evaluated to improve the reliability of source‐to‐sink models and palaeodrainage reconstructions, as autogenically controlled noise can be generated during the dispersal of detrital zircon in fluvial sedimentary systems.

Fluvial fan sedimentary characteristics of distributive fluvial system

The characteristics of fan sediment in the distributive fluvial system are evaluated based on a thorough analysis of modern silt in the Guertu river distributive fluvial system, as well as data obtained from UAV aerial photography and satellite remote sensing. The Guertu River Distributive Fluvial System (DFS) is classified into three stages, namely "proximal," "middle," and "distal," based on the examination of river morphology, sediment variations, sedimentary attributes, and other relevant aspects throughout different sections of its tributaries, from the source to the mouth. At the upstream section of the downstream fining sequence, the slope is the steepest and the hydrodynamic conditions are intense, resulting in the formation of a predominantly big gravel braided river. The river bed section has a morphology resembling a combination of a "V" and a "U" shape. It is characterized by a narrow and deep configuration, with a relatively short breadth. The sediment primarily consists of medium to large-sized gravel with minimal sand content. The gravel exhibits good roundness and displays a considerable degree of orientation. The primary microfacies present are braided channel and flood plain. The slope of the central area is decreased in comparison to the nearby end, primarily due to the presence of extensive braided rivers. The river bed has a greater width, with minor eolian dunes visible in the river channel. The gravel particles are predominantly fine to medium in size, and there is an increased amount of sand present. The predominant microfacies are braided channels, floodplains, and eolian dunes. At the distal end, the slope is minimal, the landscape is level, the braided river transitions into a meandering river, the sediment consists primarily of sand, and the signs of bioturbation are clearly visible. The primary microfacies consist of braided channels, meandering channels, floodplains, eolian dunes, lakes, and swamps.

A reinterpretation of the Jelm and Popo Agie formations (Triassic Wyoming) and distributive fluvial system (DFS) and the role of the accommodation/sedimentation ration in DFS Deposition

A reinterpretation of the Jelm and Popo Agie formations (Triassic Wyoming) and distributive fluvial system (DFS) and the role of the accommodation/sedimentation ration in DFS Deposition

Characterization and Modernization of the Depositional System in Modern Ebinur Lake Basin, Northwest China

The Ebinur Lake Basin is a typical terrestrial sedimentary Basin in Northwest China that has developed a piedmont distributive fluvial system (DFS) sedimentary environment, lake sedimentary environment, and desert sedimentary environment. The Ebinur Lake receives the sediments carried by the rivers in the basin and is the regional sedimentary center. In this study, a division scheme of modern sedimentary system tracts in the Ebinur Lake Basin was proposed. According to the landform, sedimentary environment, structure, and sedimentary system types, the Ebinur Lake Basin was divided into five system tracts. The area with high altitude and steep gradients mainly develops the rapid sedimentary system DFS, and the area with the lowest altitude in the region develops the lake sedimentary system. The main action area of climate drought and wind field is the dune sedimentary area. The wind field under the influence of hydrological climate and geomorphology has an important influence on the distribution of the sedimentary system tract. The structure determines the development of different types of sedimentary systems by controlling the topographic fluctuation and sedimentary space. Hydroclimate and geomorphology affect the development of sedimentary systems by controlling the sediment source rate in the sedimentary area. Based on the analysis of the characteristics and distribution of the modern sedimentary system in the Ebinur Lake Basin, a method for determining the level of the sedimentary system of the Ebinur Lake was established together with a plane model of the sedimentary system of the Ebinur Lake, which provides a reference for the study of the sedimentary system of continental basins.

Earth's earliest forest: fossilized trees and vegetation-induced sedimentary structures from the Middle Devonian (Eifelian) Hangman Sandstone Formation, Somerset and Devon, SW England

The evolution of trees and forests through the Devonian Period fundamentally changed the Earth's land biosphere, as well as impacting physical environments and geomorphology by stabilizing sediments and interacting with flowing air and water. From the mid-Givetian Age onwards, lignophyte flora are known to have been key parts of the machinery in the so-called Devonian landscape factory, but the impact of earlier forests, dominated by less woody cladoxylopsids, are not as well understood. We report here evidence for a previously unrecognized cladoxylopsid forest landscape, archived within the Eifelian Hangman Sandstone Formation of Somerset and Devon, SW England. This unit has previously been considered palaeobotanically depauperate, but is here shown to contain the earliest fossil evidence for such trees in the British record, as well as the oldest known evidence globally for the relative position of standing trees: in common parlance, a fossil forest. In addition to abundant fossil material attributable to the cladoxylopsid tree Calamophyton , and other early Mid-Devonian flora, the sedimentary context of the plant remains sheds light on the biogeomorphic impacts of these earliest forests. The trees colonized a sizeable distributive fluvial system that was prone to seasonal disturbance events. The nature of the sedimentary system has created a bias to those facies where biogeomorphic signatures are most frequently recorded (from the distal parts of the system), but across the whole system there is evidence of plant–sediment interactions in the form of vegetation-induced sedimentary structures, rooting features and accumulations of plant debris. Plant remains are also found in nearshore facies adjacent to the distributive fluvial system, attesting to the development of a novel non-marine/marine teleconnection from the production and export of new biological sedimentary particles. The Hangman Sandstone Formation is illustrative of the revolutionary power of cladoxylopsid trees as biogeomorphic agents, forming densely spaced forests and shedding exceptionally abundant plant debris, while also impacting local landforms and sediment accumulations and profoundly changing landform resilience against flood disturbance events. These findings provide evidence that the Eifelian Stage (393.3–387.7 Ma) marks the onset of tree-driven changes to physical environments that would forever change Earth's non-marine landscapes and biosphere. Supplementary material: Details of sedimentary facies and additional images of plant fossils are available at https://doi.org/10.6084/m9.figshare.c.7084873

Quantitative facies analysis of a fluvio-aeolian system: Lower Triassic Buntsandstein Group, eastern France

Understanding the factors that control the temporal and spatial evolution of the Lower Triassic Buntsandstein Group, eastern France, is important not just for palaeoenvironmental reconstruction but also because it is an important reservoir for the lithium-rich geothermal brines in the Upper Rhine Graben region. The interval of interest in this study, the Lower Grès Vosgien Formation (LGV), is made up of c. 200 m of clastic deposits of mixed fluvial and aeolian origin. Given the proximity between the outcrops and the areas of mineral and heat exploration, this region offers a unique opportunity for quantitative analysis and correlation between outcrops and reservoirs. The LGV is the thickest Formation in the Buntsandstein Group. However, hitherto, no detailed architectural analysis has been published to reveal the controlling factors of its depositional elements. In this study, high-resolution facies analysis was applied to thirteen outcrops, and a core, to quantify fluvial and aeolian depositional architectures, and to comprehend palaeoenvironmental conditions during their deposition. Two facies associations were identified. The fluvial channel facies association, composed mainly of sandstones deposited in poorly confined, occasionally ephemeral channels, corresponds to 93 % of the total thickness. The analysis of >800 sets of strata characterised by lower-, transitional-, and upper-flow regime sedimentary structures, distributed within different architectural elements, enabled the distinction of temporal and spatial variabilities, and an estimate of fluvial palaeohydraulic characteristics. The wind- and water-laid facies association, which accounts for 7 % of the total thickness, records an architecture controlled by a fluctuating water-table level, and ephemeral floods. Results revealed that aeolian dunes and sand sheets accumulated in distinct temporal moments. The vertical trends, recorded in the core, indicate an upward increase in the frequency of intercalations between the two facies associations, and a decrease in the occurrences of thicker cross-bedded sandstone sets of fluvial origin, which, associated with the overall retrogradational stacking pattern of the LGV, is interpreted as the preserved record of a large distributive fluvial system (DFS). The occurrence of laterally extensive aeolian deposits, overlying fluvial deposits, is often associated by authors with periods of relatively more arid conditions at a regional scale. However, evidence indicates channel belt avulsion as an alternative interpretation for the establishment of the two facies associations. The findings enhance the knowledge about the depositional controlling factors in braided fluvial and aeolian systems, and improve predictive models that account for reservoir heterogeneity in accumulated successions of this type.

Paleosol distribution and morphology along a late Cretaceous distributive fluvial system in the Bauru Basin, Brazil

Distributive Fluvial Systems (DFS) are fan-shaped landforms constituted by a radial system of channels that diverge downstream from an active apex, where the drainage emerges from the confinement valley. In such landforms, elevation, distance from fluvial channels, sedimentation rates, surface stability, and plant cover control weathering processes and soil development, but these features are obliterated within geological time. Thus, the micromorphological analysis of paleosols can be helpful for paleoenvironmental reconstruction of ancient DFS, improving the knowledge of soil genesis in these depositional landforms. Here, we describe macro and micromorphological features of twenty paleosols developed under arid to semiarid climates along the proximal to the medial zone of an Upper Cretaceous DFS in the Marília Formation, Bauru Basin, Brazil. Paleosols on the proximal zone typically showed features consistent with poor drainage, namely Bg, Btg and Bss horizons, and reddish Bt horizons in higher positions. Conversely, paleosols on the medial zone commonly showed reddish colours and pronounced secondary carbonate accumulation, consistent with a predominantly arid climate. Based on this distribution, we elaborated an evolution landscape model for the proximal and medial zone of the Bauru DFS, including allogenic and authigenic controls of soil development during the Campanian to the Maastrichtian epochs of southeastern Brazil.

Study on the sedimentary characteristics of braided fluvial fan

As a typical tight sandstone gas reservoir in the Ordos Basin, the second member of the Shanxi Formation in the XQ gas field in the Ordos Basin has had rich gas reservoirs and good development effects in the past. On the basis of previous studies, this paper brings new understanding to the sedimentary model of this area. Nine kinds of single lithofacies and seven kinds of lithofacies combinations are determined. Braided fluvial fan deposits in distributive fluvial systems likely developed in this area. The study area is part of the middle subfacies of this sedimentary facies, and five kinds of sedimentary microfacies environments developed. Finally, establishing sedimentary model based on sedimentary characteristics. The braided fluvial fan sedimentary model based on DFS is of great significance for deepening the understanding of terrestrial sedimentary systems and providing guidance for the exploration and development of oil and gas bearing basins.

Stratigraphy, sedimentology, and paleoclimatic proxies of the Upper Jurassic Morrison Formation of central Montana: Geology of the Intermountain West

Since the discovery of dinosaurs in the late 19th century, the Upper Jurassic Morrison Formation has received considerable scholarly attention. However, the formation in central Montana needed to be sufficiently investigated. Recent dinosaur excavations from exposed Morrison strata on the southern flank of Spindletop dome near the town of Grass Range, Montana, prompted a review of the formation’s geology, paleobotany, and paleoclimate. A review of historical stratigraphic measurements of the formation in Montana reveals a considerable variance in measured thicknesses. Stratigraphic measurements and regional log data indicate that the formation averages 71 m thick across central Montana. A new regional isopach map of the formation from well-log data illustrates a broad distributive fluvial system that migrated from the southwest toward the northeast. The formation is divided into two informal facies in the study area: lower and upper depositional facies. The lower depositional beds represent the mud-rich distal-most distributive fluvial facies that overlies the stranded muddy tidal flat of the Swift Formation. An increased sandstone:mudstone ratio and small isolated fluvial channel and crevasse splay beds indicate that the upper depositional beds represent the slow progression of the distributive fluvial system. However, a review of the regional field stratigraphy and well-log data did not provide a regional correlatable facies change to warrant subdividing the formation into members.The stratigraphic positions and climatic interpretations for lithologic, faunal, and floral paleoclimatic proxies are specified. The compilation of climate proxy data from central Montana demonstrates that the climate in this region was wetter than in southern parts of the Morrison foreland basin. The climatic proxies signify that the environmental conditions were variable during the Late Jurassic in central Montana, displaying changing temperatures with mesic and xeric intervals of unknown duration.

Quantifying the sensitivity of distributive fluvial systems to changes in sediment supply and lake level using stratigraphic forward modelling

ABSTRACTStratigraphic forward modelling has been used to quantify the sensitivity of sandbody connectivity in a distributive fluvial system to changes in sediment supply and lake level. Recent stratigraphic forward modelling using SedsimX from StrataMod Pty Limited of the Oligocene to Miocene Huesca distributive fluvial system in northern Spain was used as a base‐case for this sensitivity analysis. Based on literature research and initial modelling, a sediment supply sensitivity range of 0.22 to 21.85 km3/kyr and lake‐level sensitivity range of −1000 to 1000 mm/kyr were used. Results show that the stratigraphic architecture of the modelled distributive fluvial system is more sensitive to changes in sediment supply than to changes in lake level. While an increase in the rate of sediment supply results in an increase in preserved average grain size, aggradation rates and sandbody connectivity at the same distance from the apex, the average grain size, aggradation rate and sandbody connectivity all decrease with increasing distance from fan apex. The main difference in the stratigraphic architecture can be found in the proximal zones. Only oversupplied models, with much higher sediment supply than the base‐case, deposited fully amalgamated channelized deposits with laterally continuous, tabular beds with occasional scoured surfaces. Models with base‐case sediment supply contain channelized sandy deposits within a fine‐grained floodplain environment. Models with sediment supply much lower than the base‐case had no deposition in the proximal zone. Lake‐level rise leads to reduced distal erosion of sediments, concentration of silts close to the lake shore, and higher aggradation rates and thicker sandbodies in the proximal zone. The sensitivity analysis highlights that the parameters governing the formation of distributive fluvial systems have different weightings but are ultimately all interconnected and interdependent. This quantitative framework can be used as a predictive tool for subsurface exploration in distributive fluvial systems.

Anatomy of a fluvial paleo-fan: sedimentological and architectural trends of the Paleocene–Eocene Wasatch–Colton System (western Uinta Basin, Utah, U.S.A.)

ABSTRACT Recent developments in fluvial geomorphology and sedimentology suggest that fluvial fans (also known as distributive fluvial systems) could be responsible for the accumulation of great volumes of clastic successions in continental basins. A general depositional model based on sedimentological and architectural trends has been formulated for these fluvial systems, however, their recognition in the stratigraphic record often relies on partially preserved, discontinuous successions. This study provides a sedimentological and architectural characterization of Paleogene alluvial strata of the Wasatch and Colton formations in the southwestern Uinta Basin, central Utah (U.S.A.), following an ∼ 120-km-long outcrop belt which records deposition from an alluvial wedge that prograded to the north and northwest, from the basin margin to distal lake-dominated environments, preceding the onset of ancient Lake Uinta. Lateral and vertical distribution of facies associations are presented from a dataset of field observations (thirteen logged stratigraphic sections, for a total of ∼ 2400 m) and virtual outcrop models along the proximal-to-distal extent of the Wasatch–Colton alluvial system. Four sectors are defined (proximal, medial, distal, and terminal) to mark the longitudinal heterogeneity of alluvial stratigraphy. Noteworthy trends comprise a downstream decrease in the overall thickness of the alluvial stratigraphic column, a reduction in the relative volume, architectural complexity, and amalgamation of fluvial-channel bodies away from the apex, a weak downstream-fining trend in channel sandstones, and a down-system increase in preserved overbank and floodplain deposits accompanied by increasing volume and facies complexity of preserved lacustrine and palustrine facies associations. A proximal-to-distal change in fluvial-channel architecture is noted, with proximal sections characterized by vertically and laterally amalgamated sheet-like channel fills, transitioning to a lesser degree of amalgamation towards the medial sector, whereas distal and terminal sections are dominated by floodplain fines enveloping a subordinate volume of isolated, ribbon-shaped channel-sandstone bodies. The temporal development of the stratigraphic succession is observed in its entirety throughout the field area and, albeit localized, channel-scale erosion and potential depositional hiatuses punctuate the stratigraphy. Two major system-scale trends have been described in the Wasatch–Colton System (WCS). A first-order, long-term progradational trend, especially evident in proximal and medial sections, encompasses the large-scale vertical patterns in facies and architecture vertically through most of the stratigraphy of the WCS. In contrast, the uppermost part of the stratigraphic succession is characterized by a reverse, retrogradational trend, possibly associated with the early transgression of Lake Uinta's southern margin, marking the base of the overlying Green River Formation. Albeit expressed by different vertical succession of facies, proximal-to-distal processes, and stratal patterns documented along a longitudinal transect of the WCS mirror substantially identical vertical trends through the stratigraphy, which are interpreted as Waltherian superposition of distinct depositional domains during fluvial-fan progradation. Analyses of sandstone petrography and zircon geochronology suggest a unified source for the fluvial system, also supporting an interpretation as a distributive, rather than a tributive, fluvial system. This study enhances our understanding of the current depositional model for extensive fluvial-fan successions via a regional-scale stratigraphic analysis of a fluvial paleo-fan based on integrated characterization of both vertical and down-system patterns in facies distribution and fluvial architecture, providing key insights on useful criteria for recognizing fluvial-fan successions from the rock record.

Distal fluvial to lacustrine/palustrine carbonate facies of the El-Ris Formation (Late Miocene?) at the Bahariya Depression, Western Desert, Egypt: Depositional model and controls

This article aims to discuss the distal fluvial to lacustrine/palustrine carbonate facies of the El-Ris Formation (Late Miocene?) in the Bahariya Depression (Western Desert, Egypt), in terms of their depositional evolution and factors (base-level, climate, tectonics) controlling deposition. The El-Ris Formation disconformably overlies the Lower Cenomanian Bahariya Formation. It is up to 11 m thick, and includes siliciclastic facies, followed upward by carbonate facies. The siliciclastic facies consist of greenish-white, fine-grained calcareous sandstones interbedded with subordinate yellowish-brown mudrocks having insects ichnofossils reflecting deposition in a distal fluvial distributary system. The carbonate facies include the fossiliferous (mostly ostracods and a few dispersed gastropods, Lanistes carinatus,) fine crystalline lacustrine/palustrine carbonates, and calcretes-dolocretes. The lacustrine/palustrine beds are grey to pale-yellow colored massive dolomitic beds, with exposure features, reflecting deposition in a shallow, low-gradient (marginal) lake with frequent base-level changes. Calcretes-dolocretes are nodular to massive orange beds, developed at the expense of siliciclastic facies, that formed a fringe between the distal alluvial and central lacustrine-palustrine environments. Palustrine carbonate and duricrust (calcrete/dolocrete) facies increase progressively toward the top of the studied rock unit. The development of silica nodules in the palustrine facies is a result of intense evaporation just above the water table. Silica could have been released by silicate dissolution from the host alluvial deposits into the groundwater. δ13C and δ18O data indicate a hydrologically closed palustrine/lacustrine environment fed by meteoric waters, that originally precipitated calcite. Progressive evaporation of freshwater in this closed system led to dolomitization. The upward increase of carbonates in the El-Ris Formation reflects a progressive decrease of a terrigenous clastic supply in the source area and a dominance of carbonate development in the study area. During the deposition of the El-Ris Formation, the climate had marked more arid seasons with fewer intermittent humid periods. Also, the tectonic influence cannot be ruled out, since tectonic instability led to the creation of the basin depression and subsequent accommodation space that made the deposition of the El-Ris Formation.

Analysis of the Sedimentary Characteristics of a Modern Distributive Fluvial System: A Case Study of the Great Halten River in the Sugan Lake Basin, Qinghai, China

Analysis of the Sedimentary Characteristics of a Modern Distributive Fluvial System: A Case Study of the Great Halten River in the Sugan Lake Basin, Qinghai, China

Ichnology of a Middle Devonian regression: Environment, terrestrialization and true substrate controls on trace fossils of the Hangman Sandstone Formation, SW England

The Eifelian-aged Hangman Sandstone Formation of southwest England is a unit of the ‘Old Red Sandstone’ that has traditionally been considered relatively barren of trace fossils. Following recent investigations, we here show it to contain the most diverse Middle Devonian non-marine ichnofauna known globally. The fluvial-lacustrine facies of its constituent Trentishoe Member contain representatives of 21 ichnogenera including Archaeonassa, Arenicolites, Beaconites, Bifungites, Circulichnis, Cruziana, Diplichnites,?Gluckstadella, Gordia,?Halimededes,?Lockeia, Merostomichnites, Palmichnium, Petalichnus, Planolites, Polarichnus, Rusophycus, Siskemia, Spirophyton, Steinsfjordichnus, and Taenidium, as well as several microbially induced sedimentary structures. The transitional marine-influenced facies of the underlying Hollowbrook Member are less extensively exposed but contain four additional unique ichnogenera in the form of Cochlichnus, Halopoa, Phycodes, and Teichichnus, as well as further examples of Cruziana, Planolites and Taenidium. A revised ichnological assessment of the unit reveals several notable features, including the youngest known example of the arthropod refugia trace, Polarichnus, as well as a transitional trace fossil form of Diplichnites-Beaconites, demonstrating that the latter was produced by arthropods. As the Hangman Sandstone Formation records the culmination of a marine regression, its ichnofauna can be compared with that of the conformably underlying Lynton Formation, which was deposited in a sandy marine shelf setting. The ichnological differences between these units are acute, with 88% of the Hangman Sandstone Formation trace fossils being exclusive to non-marine or transitional facies. This observation sheds light on the terrestrialization process and indicates that the segregation of marine and non-marine trace fossil communities had accelerated by the Middle Devonian. Internal variability in ichnological signatures within the Hangman Sandstone Formation is also pronounced, with greater ichnodiversity and ichnodisparity in distal fluvio-lacustrine facies than in proximal fluvial facies. By viewing the depositional environment of the unit as a regionally extensive distributive fluvial system, this variability can be partly explained by a bias arising from the distribution of true substrates (bedding planes that demonstrably preserve an ancient sediment-air interface) in the unit, with such phenomena being more readily preserved in the lower energy outer reaches of the depositional system.

Gzhelian cyclothem development in the western North China cratonic basin and its glacioeustatic, tectonic, climatic and autogenic implications

The Gzhelian Ximing Sandstone–to–No. 8 Coal succession of the Taiyuan Formation in the Linxing gas field and adjacent areas records the complex nested architecture of the Palougou Cyclothem and component cyclothems 2–10 developed in the western North China underfilled cratonic basin. Integrated facies and sequence stratigraphic analysis of core, well log, outcrop, and seismic data reveals architectural variation of the Palougou Cyclothem in the study area from southwestward retrograding incised-valley estuary and lagoon (TST) through upward and northeastward prograding coastal plain to epeiric shelf (HST) into downward and eastward prograding open-coast tidal flat and epeiric shelf with aggrading distributive fluvial system (FSST). The component cyclothems vary in the internal architecture through the Palougou Cyclothem from mixed retrogradational–progradational (R–P; R/P > 1) cyclothems 2–4 in the early TST to retrogradation-dominated (R/P ≫1) cyclothems 5–7 in the late TST, progradation-dominated (R/P ≪1) Cyclothem 8 in the HST, and fluvial aggradation-dominated cyclothems 9 and 10 in the FSST. The Palougou Cyclothem and component cyclothems constrained by conodont-bearing limestone marker beds and radiometric dating have been observed to be substantially synchronized with the Gzhelian interglacial–glacial cyclothem and nested 400-kyr cyclothems in the North American Midcontinent and Donets Basin. The cyclic change in accommodation at the scale of the Palougou Cyclothem and component cyclothems has been ascribed to the third-order interglacial–glacial cycle and fourth-order, long eccentricity (ca. 400 kyr)-driven glacioeustatic fluctuations coupled with the tectonically driven source–to–sink reorganization. The progressively decreasing siliciclastic flux and increasing vegetation through both the Palougou Cyclothem and individual component cyclothems have been ascribed to the third- and fourth-order equatorial seasonally dry–wet climatic cycles coupled with the tectonically driven source–to–sink reorganization, in concert with the Gzhelian third- and fourth-order interglacial–glacial eustatic cycles. Both the transgressive fluvial degradation and the falling-stage fluvial aggradation have been ascribed to a higher-gradient fluvial profile relative to the gradient of the receiving North China epeiric shelf. The autogenic shoreline retreat, advance and channel migration modified the depositional response to the third- and fourth-order sea level rise through time. The termination of the falling-stage fluvial channel belts in the lateral and distal floodplain mires has been ascribed to the sustained fluvial aggradation and autodetachment of the fluvial fan from the syn-depositional shoreline in response to steady fall of relative sea level. This study contributes to a proper understanding of the Gzhelian North China intracratonic cyclothem development in response to the coupled glacioeustatic, tectonic, climatic, and autogenic processes at the third- and fourth-order scales, but also provides a context within which to interpret the symbiotic relationship, and predict the distribution, of superimposed coal–sandstone–shale gas reservoirs, and to investigate the impact of depositional heterogeneities on hydrocarbon generation and migration pathways.

Obliquity‐driven mountain permafrost‐related fluvial magnetic susceptibility cycles in the Quaternary mid‐latitude long‐term (2.5 Ma) fluvial Maros Fan in the Pannonian Basin

Magnetic susceptibility (MS) of the Quaternary long‐term mid‐latitude Maros fluvial fan (Pannonian Basin) was recorded to understand the stratigraphical features of source‐proximal fluvial depositional settings. Three fully cored 500‐m‐deep boreholes were sampled at 0.5‐m intervals; low‐field and frequency dependent MS were measured, and complementary hysteresis and SEM‐EDAX investigations were performed on selected samples. Logged susceptibility data were also used to log correlations established by a simultaneous comparison of wireline log and laboratory measurements. Time‐series analyses of the susceptibility records reveal a ~41‐ka and ~100‐ka cyclicity. Towards the source‐distal sections the intensity of the ~41‐ka cycles decreases, while that of the ~100‐ka cycles remains strong. Stratigraphical and spectral similarities were observed between the Maros fluvial fan and Chinese loess records; however, based on complementary magnetic data, the magnetic phase of the Maros Fan sections is related to the detrital magnetite that originates from the catchment during early postglacial permafrost degradations. The amplification of the ~41‐ka cycles can be attributed to the very high susceptibility values in source‐proximal settings and to the special stratigraphical feature of the distributive fluvial systems. This comprises the increased avulsion frequency on the fluvial fans in ‘glacial recession periods’, in concert with the ‘early postglacial’ occurrence of the permafrost‐related magnetite originating from the catchment. As a local phenomenon, this is significant since it records the obliquity‐driven variations in permafrost development in a catchment. However, fluvial and alluvial fans are widespread depositional landforms within the Eurasian mountain range and were possibly the same during the Quaternary deglaciations. Thus, obliquity‐driven magnetic susceptibility variations in source‐proximal fan deposits attached or adjacent to regions of loess deposition should also be considered when scanning for potential source material of aeolian deposits.

Palaeosols as stratigraphic proxies and palaeosurface markers in distributive fluvial systems

Palaeosols can be used as stratigraphic proxies, palaeosurface indicators, and palaeorelief reconstitution tools, as they reflect a complex interrelationship between sedimentation, erosion, non-deposition, and pedogenesis. The objective of the article was to estimate the relative time of formation of palaeosols of the Marília Formation, to determine the periods of non-deposition and non-erosion, indicative of stabilities on the surfaces, and to interpret the profiles as markers of palaeosurfaces in distributive fluvial systems (DFS) of the Late Cretaceous of Brazil. Eleven sections of the Marília Formation (S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, and S11) were described, comprising forty-three profiles. The pedotypes classification (polygenic, compound, and cumulative) and the determination of palaeosols' relative formation time and residence time were based on the specialized literature. The reconstitution of pedosedimentary cycles considered the dynamics of sedimentation, erosion, and pedogenesis. Eight sedimentary cycles and 45 pedosedimentary cycles were interpreted. All the Maastrichtian pedosedimentary cycles of the Bauru Basin corresponded to depositional cycles interspersed with erosive and pedogenic processes. Palaeosols with argillic (Btk, Bt, Bss) and calcic (Bkm) horizons, developed from fluvial sandstones, evolved in processes predominantly after the deposits, with later erosive processes. However, although most of the profiles developed in periods between deposits and erosion, pedogenic processes also occurred concomitantly with the sedimentary cycles, favouring the formation of polygenetic profiles, which presented the longest pedogenic cycles in chronological terms. Palaeosols with argillic horizons can be important stratigraphic landmarks. They represent stopping moments in erosion and sedimentation of up to 1.374 My, thus consisting of the closing of high-frequency depositional cycles. Although palaeosols can demonstrate relief inversion and pedotypes with Bt-horizons can indicate ancient regional surfaces, the complete reconstitution of the topography becomes more possible at the local level, in a palaeoslope approach, due to the variability of pedofacies.

Fluvial reservoir architecture, directional heterogeneity and continuity, recognizing incised valley fills, and the case for nodal avulsion on a distributive fluvial system: Kern River field, California

Fluvial reservoir architecture, directional heterogeneity and continuity, recognizing incised valley fills, and the case for nodal avulsion on a distributive fluvial system: Kern River field, California

Use of Remote-Sensing to Quantify the Distribution of Progradation/erosion Along a Forced-Regressive Modern Coastline: Driving Factors and Impact on the Stratigraphic Record

The long-term development of ancient and modern coastal distributive fluvial systems (DFSs) during periods of relative sea-level highstand or fall usually drives net-progradation of shorelines. Such systems often develop in periods of relative sea-level highstand or fall and typically record annual to millennial-scale deviations in coastal trajectories. A new continental dataset (Digital Earth Australia Coastlines: DEA Coastlines) provides an opportunity to examine such variations in coastal behaviour over annual to decadal scales (1988-2019) at local to continental spatial scales. This dataset is herein applied to the 655 km coastline fronting Australia’s largest amalgamated coastal distributive fluvial systems, which is situated in the epicontinental seaway of the Gulf of Carpentaria in the north of the continent. Despite the overall forced regressive conditions (i.e. progradation during relative sea-level fall), only 54% of this coastlines length net-prograded, whereas 47% was eroded. Though temporal cyclicity in progradation and erosion is evident along segments of this coast, these patterns could not be correlated with either the Southern Oscillation Index (R2 = -0.20) or rainfall (R2 = 0.24). Instead, short-term coastline dynamics appear to be the result of complex interactions between fluvial, wave, longshore current, and tidal processes. The high-resolution DEA Coastlines dataset highlights the diachronous, heterochronous, composite, and amalgamated nature of net-progradational stratigraphic strata that can develop in shallow-marine environments where hinge-points between prograding and retrograding coastal segments are dynamic features that migrate with time. Our conclusions show that shorelines display granular temporal and spatial deviations in coastal trajectory, with contemporaneous progradation and erosion occurring over 1-100 km length scales. This is significantly more heterogeneity than previously envisaged, thereby suggesting the need for updating models of coastal systems.

Application of remote sensing in the description of fluvial system in dryland: A case study of Golmud distributive fluvial system, Qaidam Basin, NW China

Distributive fluvial systems (DFS) are widespread in drylands in the northwestern China. Analyzing differences in fluvial morphology in drylands is beneficial for studying ancient rock records and the extra-terrestrial surface environment. The remote sensing image, characterized by real-time and possibility of repeated observations, is a vital tool for recording and comparing fluvial systems in drylands. Satellite remote sensing technology is a method of investigating fluvial morphologies. Due to the limited accuracy of satellite imagery, there are few reports on the detailed description of the fluvial system in drylands of NW China. We analyze the pattern of fluvial morphology changes in the Golmud distributive fluvial system (DFS) in the Qaidam Basin, northwestern China, using satellite remote sensing and unmanned aerial vehicles (UAV). Firstly, we use Google Earth real-time image data, historical image data, and radar digital elevation data to extract geomorphological information; then the UAV remote sensing image data were used to interpret fluvial network information; finally, we use the gray-scale differential vector method to describe the fluvial morphologies. Three zones have been identified in the Golmud DFS: the proximal, the medial, and the distal, by comparing the differences in topographic and geomorphic characteristics, fluvial morphologies, and sedimentary characteristics of the Golmud DFS. The proximal slope is higher than the other two zones, and the geomorphic features are mainly gravel gobi. The proximal fluvial morphologies are mainly large braided rivers, and sediments are more gravelly and less sandy. The medial slope is relatively small, and the geomorphic features are mostly oasis plains. The medial fluvial morphologies are mainly meandering rivers associating with braided rivers, and sediments are more sandy and less gravelly. The distal slope is the lowest, and the geomorphic features are mostly oasis plains, lakes, and marsh plains. The distal fluvial morphologies are mainly meandering rivers, and sediments are sandy and muddy. Comparison of the DFS from proximal to medial to distal in Golmud confirmed the potential of remote sensing image technology in identifying the fluvial morphologies and sedimentary facies distribution in dryland.