Fluvial Deposits Research Articles

Facies partitioning of fluvial, wave, and tidal influences across the shoreline-to-shelf architecture in the Western Interior Campanian Seaway, USA

Abstract The influence of bottom currents and tectonic activity on shelf sedimentary processes and sand distribution remains poorly constrained. A growing body of research highlights the importance and variability of the shelf sandstone bodies. To explore the roles of fluvial, wave and bottom current-controlled sediment distribution in the Western Interior Seaway, 21 marine sandstone outcrops in Wyoming and Colorado were analysed. Recurring facies associations include: paralic, tide-influenced coastal margins; mainly east and SE prograding, wave-dominated delta-fronts and shorefaces; heavily bioturbated, glauconitic sandstones; and traction current-dominated, tidally influenced, open-marine subaqueous delta and shelf deposits, with southward palaeocurrent directions. Intense reworking by a moderately diverse ichnofauna occurs in wave-dominated and glauconitic facies. Minimal burrowing occurs in cross-stratified subaqueous delta and shelf deposits. Lithofacies associations are interpreted to change basinward with increasing water depth. Ichnoassociations reflect the proximity of river mouths. Widespread, southward palaeocurrent directions, not restricted to a narrow longshore zone, on the shallow-marine shelf indicate the persistence of strong, along-shelf sand-transport which has not been previously documented in detail. Palaeobathymetric complexity caused by uplift of Laramide structures amplified and accelerated bottom and tidal currents and facilitated the erosion, transport and deposition of older sediments.

Effects of soil and water conservation measures on sediment delivery processes in a hilly and gully watershed

China has implemented a series of ambitious soil and water conservation (SWC) projects on the Chinese Loess Plateau, which have significantly changed the erosion, transport, and deposition of sediment. As a result, the sediment flux of the Yellow River, once the largest carrier of fluvial sediment worldwide, has been reduced by approximately 85 % in the past 60 years. However, the effects of SWC measures on erosion, transport, and deposition of sediment are still difficult to quantify, which greatly limits the further planning and adjustment of SWC measures. Here, we determined soil erosion, sediment deposition, and sediment yield at different historical stages in a 187 km2 hilly and gully watershed on the Chinese Loess Plateau using the unmanned aerial vehicle (UAV) photogrammetry technology combined with check dam surveying and hydrologic monitoring. The results show that the construction of check dams and vegetation restoration significantly reduced the soil erosion rate, from 21,144 t km−2 yr−1 at Stage-1 (1960–1969) to 13,819 ± 3,622 t km−2 yr−1 at Stage-2 (1970–1999) and further to 4,723 ± 1,278 t km−2 yr−1 at Stage-3 (2000–2018). The sediment deposition rate was estimated to be 5,989 and 2,582 ± 351 t km−2 yr−1 at Stage-2 and Stage-3, respectively. The variation in the erosion and deposition of sediment led to a significant change in the sediment delivery ratio, from 1 at Stage-1 to 0.57 at Stage-2 and 0.45 at Stage-3. Our research results provide an important reference for further SWC planning.

Holocene molluscan succession and paleoenvironmental reconstruction of the upper Moulouya basin: New data from the Sidi Bouramdan site (Morocco)

This work focuses on litho-stratigraphic and malacological studies of the fluvial deposits of the Middle Moulouya, which are used to reconstruct the paleoenvironments and paleoclimates of Morocco during the Holocene. The objectives were to deduce environmental and climatic changes from the study of fluvial deposits known for their richness in paleontological remains and their spatial and temporal variations. The chronostratigraphic framework of the fluvial record is based on the radiocarbon dating of a dozen charcoal assemblages.Sidi Bouramdan is located in the Midelt region in the Ksabi basin (the Middle Moulouya) of Morocco. The Holocene plain morphodynamics are characterised by a cut-and-fill terrace system associated with a progressive deepening of the riverbed. At the level of Sidi Bouramdan, a geomorphological and lithological study identified five Holocene nested terraces of over 10-m sedimentary thickness, dated to between 10248 and 10649 cal BP and 782–921 cal BP. These show a strong chronostratigraphic discontinuity with formations of the middle Holocene period being locally absent, probably because they were destroyed by the evolution of the alluvial plain.Forty-four mollusc species were identified in the malacological study of this fluvial Holocene sequence, with changes in the malacological communities reflecting environmental variations in the fluvial system. The Upper Holocene terrace T0 was characterized by marshland-preferring species, thereby revealing a wet environment. In the other three lower Late Holocene terraces, aquatic species tended to disappear, and terrestrial species predominated, indicating the appearance and development of a dry environment in phase with paleoenvironmental data from various regional marine and continental sedimentary archives.

Turbidity maxima in estuarine networks: Dependence on fluvial sediment input and local deepening/narrowing with an exploratory model

An estuarine turbidity maximum (ETM) results from various subtidal sediment transport mechanisms related to, e.g., river, tides, and density gradients, which have been extensively analysed in single-channel estuaries. However, ETMs have also been found in estuaries composed of multiple interconnected tidal channels, where the water and suspended fine sediments are exchanged at the junctions with possible occurrence of sediment overspill. The overall aim of this study is to understand the processes that determine the ETM dynamics in such channel networks. Specifically, focusing on the ETMs formation due to sediment transport by river flow and density-driven flow, the dependence of ETM locations in an idealised three-channel network on fluvial sediment input and the local deepening and narrowing of a seaward channel is investigated. It is found that the ETM dynamics in channels of a network is coupled, and hence, changes in one channel affect the ETM pattern in all channels. Sensitivity results show that, keeping river discharge fixed, a larger fluvial sediment input leads to the upstream shift of ETMs and an increase in the overall sediment concentration. Both deepening or narrowing of a seaward channel may influence the ETMs in the entire network. Furthermore, the effect of either deepening or narrowing of a seaward channel on the ETM locations in the network depends on the system geometry and the dominant hydrodynamic conditions. Therefore, the response of the ETM location to local geometric changes is explained by analysing the dominant sediment transport mechanisms. In addition to the convergence of sediment transport mechanisms in single-estuarine channels, ETM dynamics in networks is found to be strongly affected by net exchange of sediment between the branches of a network. We find that considering the sensitivity of net sediment transport to geometric changes is needed to understand the changing ETM dynamics observed in a real estuarine network.

Tidal Sediment Supply Maintains Marsh Accretion on the Yangtze Delta despite Rising Sea Levels and Falling Fluvial Sediment Input

Tidal marshes are among the world’s most valuable ecosystems; however, they are increasingly threatened by rising sea levels and a decline in fluvial sediment supply. The survival of a tidal marsh under these twin threats depends upon the net input of tidal sediments, because this will determine the deposition rate. The rate of relative sea level rise currently affecting the Yangtze Delta is rapid (~4 mm/a), and the sediment discharge from the Yangtze River has decreased by >70% over recent decades. In order to improve our understanding of the response of the marshes in the turbid zone of the Yangtze Estuary to these changing environmental conditions, we measured sediment transport in and out of a tidal basin and calculated the deposition rate over eight tidal cycles covering different tidal ranges during the summer and winter seasons. The suspended sediment concentration (SSC) during the flood phase of the tidal cycle (average = 0.395 kg/m3) was markedly higher than that during the ebb (average = 0.164 kg/m3), although water transport during the flood tide was almost equivalent to that during the ebb. As a result, ~40% of the sediment inflow during the flood phase was retained within the marsh. This reason is mainly attributable to the dense marsh vegetation, which attenuates waves and currents and to which the sediments adhere. The annual deposition rate in the marsh was approximately 6.7 mm/a. These findings indicate that under the combined influence of sea level rise and river sediment supply reduction, the sediment transport through the turbidity maximum zone of the Yangtze River estuary could maintain the relative stability of the marsh area to a certain extent.

Performance of a sediment microbial fuel cell for bioenergy production: Comparison of fluvial and marine sediments|

Bioenergy production from sediment microbial fuel cells has gained special attention for its application as a power source for environmental sensors. A sediment microbial fuel cell is a device capable of generating energy from sediments and electrolytes present in water bodies. Numerous factors must be considered to improve cell efficiency. However, a little considered factor is the quality of the sediment that is used to feed a SMFC. This research focused on the study of sediment quality and the influence of hydrological season on the production of electrical energy. A non-divided SMFC was designed with Unidirectional Carbon Fiber as electrodes. Four SMFC were prepared for the experimental work. Two cells were fed with marine and fluvial sediments collected in the rainy season and two others with sediments, of the same origins, collected in the dry season. The electrical energy of each cell was quantified during a period of 30 days. The results showed that the season influences the production of electricity. In the rainy season, the marine sediments produce greater energy with an average of 407.83 mV. In the dry season highlighted the fluvial sediments with 700.7 mV. Power densities of 141 and 70 mW cm−2 were achieved for marine and fluvial sediments, respectively. A preliminary identification of the microbial communities was carried out for both sediments. Correlation studies showed that electrical conductivity and salinity have a positive influence on the voltage, while temperature and dissolved oxygen have no significance.

The Paraná River in the argentine plain: A review of its evolution and contemporary characteristics

This paper discusses the geological evolution of the Paraná River in Corrientes Province, located inside the Mesopotamic Argentine region, and reviews the principal geomorphological and hydro-sedimentological characteristics of this outstanding fluvial system.Active lateral migration of the Paraná River inside its large alluvial fan, which covers the north-western portion of Corrientes Province, reveals a structural control related to the separation and breakup of Gondwana. The lowlands now present in this region receive only pluvial input and constitute one of the largest wetlands in South America, the Esteros del Iberá.The best exposed geological units in Corrientes Province are the Ituzaingó Formation (Plio-Pleistocene) that is a fluvial deposit associated with evolution of the Paraná River, and the Toropí-Yupoí Formation (Pleistocene), a younger palustrine fill generated by deposition of aeolian sediment over the underlying fluvial sands.The present planform pattern of the Paraná River in Corrientes Province is anabranching with several types of bar that occupy more than 30% of the channel surface. The bed sediment is predominantly medium to fine sand with the dominant bedform being dunes, which thus also dominate its subsurface sedimentary architecture.The suspended sediment concentration of the Paraná River downstream from its confluence with the Paraguay River (its main tributary) is asymmetric across the channel width, with higher concentrations towards the west due to the much higher input of sediment from the Paraguay River, which in turn receives most of its suspended sediment from the Bermejo River. At Corrientes City, suspended sediment concentration shows extremes ranging from 1 to 616 mg L−1 on the eastern margin and from 8 to 1271 mg L−1 on the western margin. Mixing between the Paraná and Paraguay rivers flows may take more than 600 km downstream before full mixing is achieved, with the mixing processes at the junction being determined by the discharge (momentum) ratio between the two confluent rivers, topographically-driven flows and the possible influence of density driven underflows at their interface. The confluence area between the Paraná and Paraguay rivers is characterized by a large scour that is ∼30 m deep, with its deepest location being at the mouth of the Paraguay River where the channel narrows due to local bedrock control.Due to the different elevation of the Paraná River margins in the region downstream of the confluence, the contemporary floodplain is developed extensively only on the western margin. This floodplain can also be considered as proximal (flooded yearly) or distal (flooded only during extraordinary events) in its geomorphic character. Most of the headwaters of small tributaries in this part of the Paraná River basin are located in wetlands. In these wetlands, the channel beds are characterized by fine sediment consisting of silt and cohesive clays, and where the suspended sediment has a high proportion of organic matter.

Does the Threshold of Sediment Motion Constrain the Width of an Incising Laboratory River?

AbstractA physically rational model for river width is critical to predict macroscopic landscape evolution driven by fluvial sediment transport. Growing evidence suggests that rivers widen until the stress exerted by the fluid on the bed surface is close to the critical entrainment stress of the bank material. In this study, we test the limits of this model as a closure assumption in dynamically evolving river systems. We consider a simple laboratory channel with a fixed water discharge, monodisperse bed material, no sediment supply, and an initial relief that was sufficiently large to guarantee a finite transport capacity. Over time, the transport capacity approaches zero through changes in channel morphology. Concurrent measurements of width and sediment load illustrate how theory developed for equilibrium rivers fails to predict transient channel processes. Similarity to first order trends in natural rivers suggest that many rivers could be far from equilibrium.

Assessment of Shoreline Change Along The Sandy Beach of Ellembelle District of Ghana

Sandy beaches are most popular tourists and fish landing sites, and serve as habitat for several endangered species. However, sandy beaches more vulnerable to coastal erosion, particularly those along open oceans. Assessment of shoreline change using reliable dataset aid in understanding the morphology of coastal landforms, the processes associated with their occurrence and support decision making. This paper analysed available multi-temporal spatial dataset and field observations using GNSS techniques to assess the shoreline change along the study area. The shoreline features were extracted from 1974 topographic map and 2005 orthophotographs using the High Water Line (HWL) in conjunction with 2020 spatial data. Shoreline change statistics were computed using DSAS. A geodatabase was created, transects were cast and the shoreline change rates computed using EPR, LRR and WLR methods. Both accretion and erosion were recorded with mean erosion rate of 0.97 m/year. It was observed that sections of the shoreline nourished by Ankobra and Amunzuri rivers were experiencing some accretion, particularly the mouth of the Amuzuri river. The estuary of Amunzuri river was found to be drifting eastwards at a rate of 5.4m/year possibly due to tides, waves and currents. The study concludes that in spite of the littoral drift eastwards, fluvial sediment supplied by coastal rivers accounts for the relative stability of shoreline in the area. Policy formulation regarding possible damming of coastal rivers by government under the ‘one district one dam’ agenda must be carefully considered to avert high levels of erosion along the western coast of Ghana.

Single-grain K-feldspar pIRIR dating of the Shalongka archeological site revealed the relationship between monsoon, overbank flooding, and human occupation during the Holocene on the northeastern Tibetan Plateau

The increased frequency of flooding on the Tibetan Plateau as a result of global warming has affected the lives of millions of people along the river valleys. The relationship between human settlement, climate change, and the frequency of flooding at long time scales is still unclear primarily due to the lack of a robust chronology for flooding deposits. In this study, AMS 14C dating, single-grain quartz OSL dating, and single-grain K-feldspar pIRIR dating using pIR50IR170 and pIR200IR290 signals were applied to the fluvial-paleosol sequence at the archaeology site Shalongka (SLK20) in the upper Yellow River valley on the northeastern Tibetan Plateau, where Paleolithic, Neolithic, and Bronze Age cultural layers were found. Utilizing luminescence characteristics analysis and a comparison of quartz OSL ages, K-feldspar pIRIR ages, and charcoal 14C ages, the reliability of single-grain quartz OSL and K-feldspar pIRIR ages was tested. Our results indicate that single-grain K-feldspar pIRIR170 dating with the minimum age model (MAM) can be used to date Holocene fluvial deposit that have been poorly bleached. Based on the age-depth model, proxy data of the SLK20 grain size and magnetic susceptibility demonstrate that Yellow River overbank flooding increased during the periods 9.9–9.1, ∼8.0, 7.6–6.3 and 5.0-3.4 kyr BP; during the intervals between these periods, Yellow River overbank decreased and paleosols developed. Human occupations, as indicated by the appearance of cultural layers at the SLK20 site during the ∼8.1, ∼7.8, 6.3–5.0 and 3.4–2.0 kyr BP periods, occurred when paleosol developed. The variation in East Asian summer monsoon (EASM) intensities caused a moist and warm mid-Holocene climate at the SLK20 site, which was conducive to human settlement. Flood events caused by EASM precipitation changes during the mid-Holocene significantly influenced human settlement at the SLK20 site. During the middle to late Holocene, as EASM decreased in the region, the improvement of subsistence strategies likely dominated human settlement on the northeastern Tibetan Plateau.

The largest Quaternary inland eolian system in Brazil: Eolian landforms and activation/stabilization phases of the Xique-Xique dune field

Eolian systems are sensitive to vegetation and climate changes, but also to the sediment supplied by neighbor depositional systems. This sensitivity is manifested in the alternation between periods of sand dune mobility and stability. In the Xique-Xique eolian system, the largest Quaternary interior dune field in Brazil (∼8000 km2), the neighboring depositional system responsible for the sand supply is the São Francisco River. We interpreted periods of dune activity and stabilization by mapping eolian landforms of this system, describing depositional facies under them and dating by optically stimulated luminescence (OSL-SAR). The stabilized parabolic landforms characterized and mapped (all formed by SE to E winds) were simple megadunes (25.5 ± 4.4 to 5.8 ± 2.0 ka), compound dunes (15.8 ± 1.2 to 5.2 ± 1.4 ka) and perched dunes (14.0 ± 1.0 and 1.2 ± 0.1 ka). We also recognized eolian plains (14.0 ± 2.1 to 6.5 ± 0.7 ka) and active parabolic dunes. Eolian deposits of undifferentiated landforms have also been described and dated (253.8 ± 19.0 to 8.2 ± 1.3 ka). The ages obtained allowed identification of two main phases of dune activity (∼60 to 18 ka and ∼16 to 5 ka) separated by a short period of stabilization marked by a paleosol (∼18 ka). The main periods of eolian activity are associated with phases of fluvial aggradation and high sediment supply, whereas dune stabilization since 5 ka is correlated with low sediment supply during the Late Holocene fluvial incision phase. The periods of eolian activity and stabilization respond not only to climate changes in the area occupied by the eolian system but mainly to local fluvial sediment supply by the river, which in turn can respond to more regional climatic controls. The Xique-Xique eolian system results from the coupling of abundant sediment supply from the fluvial system, high eastern wind speeds, and a significant wind deceleration caused by mountains on the western border of the dune field.

Valorization of Fluvial Sediments Treated with Hydraulic Binders and Influence of the Particle Size Distribution of the Incorporated Correctors on Their Properties

Valorization of Fluvial Sediments Treated with Hydraulic Binders and Influence of the Particle Size Distribution of the Incorporated Correctors on Their Properties

ESR chronology of the fluvial sequence of Cueva del Silo (Sierra de Atapuerca, Spain)

The Cueva del Silo is part of the lower karst level of the Cueva Mayor-Cueva del Silo karst system (Sierra de Atapuerca, Burgos, Spain), whose evolution has preserved an impressive archeo-paleoanthropological sequence since the Early Pleistocene. Cueva del Silo is remarkable for the presence of fluvial deposits that record the entry of the Arlanzón River water in the cave system, providing a key sequence to investigate the fluvio-karstic relationships that give rise to this endokarst system. In order to provide a chronological framework to these fluvial deposits, six sediment samples were dated by Electron Spin Resonance and 16 samples by paleomagnetism, collected from two outcrops: Galería de las Arenas and Sala del Caos. Our results provide maximum mean age of around 1600 ka and a minimum age of 916 ± 136 ka for the deposits in Sala del Caos. The younger date from Sala del Caos might represent the last fluvial input from Arlanzón River in the lower karst level. In contrast, ESR ages estimates of 1268 ± 133 ka and 1262 ± 108 ka were obtained for Galería de las Arenas sequence, which could indicate re-sedimentation processes from the intermediate karst level where similar ages were published. The annual dose might be wrongly assessed due to the re-sedimentation processes inside the karst, hence, ESR ages for these facies should be treated with extreme caution. • We date allochthonous fluvial sediments preserved in Cueva del Silo in the Sierra de Atapuerca lower cave level. • For that, we applied ESR and paleomagnetism techniques to two Cueva del Silo sequences. • Results suggest the last fluvial inputs around 900 ka and possible re-sedimentation processes from the intermediate level.

Sedimentation, tectonics and climate in Ladakh, NW Trans-Himalaya-with a special reference to Late Quaternary Period

Ladakh, the newly formed Union Territory of India, is a cold arid high altitude desert lying in the Trans-Himalaya and is an important region for geographers and geologists, because of its lunar/martian landscapes, exposures of sedimentary, metamorphic and igneous rock types, glacial, fluvial lacustrine sediments and active tectonic and climatic processes. This paper sums up the sedimentary characteristics, tectonic and climatic history with examples from the variety of sediment exposures along the Indus River. The overall geomorphological evolution of Ladakh is basically governed by two sets of geological processes—the continental scale geological processes that have primarily provided the basic framework for the landscape and second the regional/local scale geological processes in which the role of tectonics and climate which has been significant in determining the glacial, fluvial, lacustrine and aeolian processes. The transient topography of the region is attributed to (a) the movement along active Stok thrust, along the Indus Suture Zone; (b) long term steady state perturbed by climate change; (c) location in orographic rain shadow zone; and (d) the landscape being not in cosmogenic steady state due to topographic effect and methodological uncertainties of data.

Longitudinal scour-bar pattern in large convergent estuaries on low-lying coastal plains

A seaward decrease–increase–decrease trend in the longitudinal bed level, defined as scour-bar pattern, is observed in several large estuaries on low-lying coastal plains such as the Amazon, Yangtze and Fly. Why this pattern forms has not yet been well explained. The mechanism for the formation of this pattern is explored here using a one-dimensional morphodynamic model, with varied geometry, fluvial water discharge, sediment flux and tide. Results show that for those estuaries with bed slopes in the order of 10−5 and sediment concentration in the order of 0.1 kg m−3, bars are likely to occur for channels with relatively weak convergence and wide mouth, while scours are nearly ubiquitous. Scours are classified as fluvial and tidal based on the relative strength of river and tide, which can be distinguished by bed slope and water depth. A balance between river and tide can lead to no scours or bars. Sediment reduction and sea level rise enhances the relative strength of tide, and transition of a fluvial scour to a tidal scour may occur.

Dating of megaflood deposits in the Russian Altai using rock surface luminescence

Catastrophic drainage of ice-dammed lakes in the Altai Mountains has been inferred from geomorphological evidence in the Katun Valley (Russia), and is presumed to have occurred during the Pleistocene. The sedimentary features have been difficult to date directly, due to the absence of organic carbon, and the improbability that luminescence signals in sand grains would be reset during transport. However, the development of rock-surface luminescence dating provides a new opportunity to date the features: clasts have a different transport history to sand grains, and their luminescence depth profiles can be inspected for evidence of bleaching before burial. Here we investigate two sites in the Altai Mountains, and use rock-surface luminescence burial dating to constrain the age of the megaflood deposits. In the Katun Valley, we sampled granite cobbles from a frozen sediment clast emplaced as a dropstone within a massive megaflood gravel terrace. Burial ages for the clasts range from 16.7 to 21.4 ka, with a mean age of 19.8 ± 1.5 ka. This represents the depositional age of the fluvial sediments that preceded the lake outburst flood, (and hence places a maximum age on the catastrophic flood). Clasts sampled from mega-ripples in the Kurai Basin are shown to have a mid-to-late Holocene burial age, which is not consistent with the possible origin of these features during a catastrophic drainage of a glacier-dammed lake. Instead, the burial age of the Kurai Basin sediments may reflect local-scale periglacial or seismic processes along the Kurai Fault Zone.

Facies analysis, diagenesis, and petrophysical controls on the reservoir quality of the low porosity fluvial sandstone of the Nubian formation, east Sirt Basin, Libya: Insights into the role of fractures in fluid migration, fluid flow, and enhancing the permeability of low porous reservoirs

A better understanding of the factors controlling reservoir quality in low-porous heterogeneous reservoirs is very important for petroleum exploration and production. This study investigates the depositional and post-depositional factors that control the sandstone reservoir quality of the Upper Nubian Member, North Gialo Field, East Sirt Basin, Libya, using an integrated facies analysis, diagenesis, and petrophysical analysis. To investigate the relationship between facies and petrophysical parameters and identify the role of fractures in the pore system enhancement of low-porous reservoirs, we incorporate core analysis, petrography analysis, and petrophysical measurements. The study revealed that the Upper Nubian Member is a very heterogeneous reservoir with major lateral and vertical quality variations, and has low porosity and fair permeability. The reservoir can be subdivided into seven lithofacies and grouped into four dominant facies associations (FAs) (i.e., flood plain, crevasse splay, meandering channel, and braided channel) based on sedimentological analysis. Comparison among different FAs of the fluvial setting shows that the fluvial meandering and braided channel sandstones have the best reservoir quality, while the crevasse splay FAs display moderate reservoir quality, and the flood plain FA, as expected, has the lowest reservoir quality due to the high detrital clay content. The sedimentological analysis reveals that the primary textural characteristics of the lithofacies (i.e., grain size, sorting, and detrital clay content) have a medium effect on the distribution of porosity and permeability in the fluvial reservoir, while diagenetic events may have a large effect, contributing to the delivery of a heterogeneous reservoir. The facies analysis, petrographic analysis, and routine core analysis (RCAL) results revealed that the main factors controlling the degradation of reservoir quality are mechanical compaction, quartz overgrowth, and clay cement precipitation, while the feldspar and anhydrite dissolution and fractures resulted in enhanced reservoir quality. The fracture characterization and image log analysis revealed that fractures play a significant role in the reservoir permeability of low porous fluvial sediments, with five types of fractures dominating the fracture network in the studied reservoir. The research defines the fractures' origin and their role in fluid migration, fluid flow and reservoir quality enhancement, as well as demonstrates how the fractures work as conduits across the low porous sand units. Furthermore, it can provide a reference and direction for reservoir development in the search for the high-quality sweet spot in low-porosity fluvial reservoirs.

Tracing sediment provenance in the Yellow River, China: Insights from weathering, recycling, and rock compositions

Geochemical investigations of fluvial sediment help understand the provenance of sediment and surface processes taking place on the Earth at the watershed scale. This study is aimed at identifying the weathering and sedimentary recycling of the surface sediment of the Yellow River using the Chemical Index of Alteration (CIA), Weathering Index of Parker (WIP), Index of Compositional Variability (ICV), Mafic-Felsic-Weathering (MFW) ternary diagram, and Al-Ti-Zr ternary diagram. Source rocks compositions were clarified using Al2O3-CaO⁎+Na2O-K2O (A-CN-K), MFW, discriminant function, and Cr/V vs Y/Ni diagrams. The results demonstrated that the surface sediment of the Yellow River has experienced an overall low intensity of weathering and recycling. However, significant differences were observed in the characteristics of weathering and recycling among the upper, middle, and lower reaches, which is in turn associated with the differences in climatic conditions and tectonic settings. Source rocks manifested a typically mixed type composition, including felsic igneous rocks, intermediate igneous rocks, quartzose sedimentary rocks, and mafic components. Moreover, the sediment in the source area of the Yellow River may have originated from the clastics produced by the abrading of mountain glaciers. Sediment in the area in which the Yellow River flows through the Chinese Loess Plateau primarily originates from loess in the desert in Northwestern China. Sediment in the lower reaches does not only include the sorted sediment flowing down from the upper and middle reaches, but also that imported from regional rivers. This study can furnish a sound scientific basis for the reconstruction of the paleoclimatic and paleoenvironmental changes that affected large watersheds in arid and semi-arid areas.

Multi-scale, multi-style soft-sediment deformation structures preserved in Cenozoic fluvial deposits, southeastern Brazil: Evidence of impact shaking?

Soft-sediment deformation (SSD) structures preserved in sedimentary successions can record significant seismic events which occurred during or right after deposition. The integrated analysis of sedimentary facies, depositional architecture, and SSD data can determine the relative temporal relationship between deposition and deformational events, and reveal the origin and mechanisms involved in the deformation and the resulting structures. The São Paulo Formation in southeastern Brazil preserves Cenozoic alluvial deposits which characterize most of the geology of the homonymous metropolis area. This succession preserves fluvial channel and floodplain deposits, with associated debris-flow dominated alluvial fan deposits, and preserves abundant SSD structures in a wide range of dimensions and morphologies. These deformation structures include small- and large-scale folds, multi-scale vents of varied geometries, ball-and-pillow structures, and clastic dykes. Here we provide an integrated analysis of sedimentary facies, depositional architecture data, and SSD data from the São Paulo Formation, in order to discuss the deformation mechanisms and plausible triggering mechanisms responsible for the development of such structures. Our interpretation is that SSD structures in the São Paulo Formation were likely triggered by a Cenozoic meteor impact recorded by a crater near the study area.

Middle and Late Pleistocene evolution of the Ardèche Valley archaeological landscapes (France)

Most archaeological and palaeo-environmental archives are preserved in specific environments (buried sediments, rock shelters, cave environments). Hence, the information we can obtain is usually incomplete, and lacking spatial and morphological significance. Studying landscape evolution can help us to understand the location and distribution of past societies and their relation to Quaternary environments. In the Ardèche Valley, most Middle and Late Palaeolithic sites are preserved in caves and rock-shelters and in rare cases in fluvial sediments. Here we apply an integrated geomorphological approach to the study of the evolution of the Ardèche Valley combining multi-method dating, geomorphological mapping and surveys of cave and fluvial formations. We review chronological results obtained through multi-method dating (electron spin resonance (ESR), infrared stimulated luminescence (IRSL), uranium-series (U-series), combined electron spin resonance/uranium-series (ESR/U-series)) on cave and riverine objects and combine them with topographic and stratigraphic observations in an integrated Bayesian hierarchical model. The results are in agreement with those obtained from other rivers in mountainous environment around the Mediterranean Sea and show sedimentation/incision phases that match the 100 ka glacial/interglacial cycles. The mean rate of river incision deduced from the established chronology for the Middle and Late Pleistocene period, 76 ± 7 m.Ma−1, shows adjustments to a moderate uplifting dynamic that shaped the main topographical features seen today in the landscape of the Ardèche Gorge. The spatially reconstructed alluvial features provide a palaeogeographic framework that can be used directly as a chronological and topographical constraint for archaeological research in the Ardèche catchment.