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The estimates of water flow in the paleorivers with known paleochannel morphometry was compared with basic hydrological and climatic indicators found by paleogeographic analogy in the regions-analogues, determined by fossil flora analysis from the Holocene (from the present to 10 thousand years ago), the Late Valday (17–18 thousand years ago) and before the Eemian (~140 thousand years ago) deposits. Comparison of annual runoff depth obtained by regime equations and equations of hydraulics and taken from the hydrological maps in the regions-analogues, showed quite satisfactory compliance. Relative error of comparison for the different objects is in the range of ±11–23%, which does not exceed the average error of water flow estimation by each of these techniques separately. However, the error of ±20% is significant and geomorphological approaches can be applied only for the cases of sufficient changes in the water flow of ancient rivers (twice or more) and for long-term periods. Nevertheless, the use of geomorphological approaches and the method of paleogeographic analogy is now one of the main ways to reconstruct water resources in the past and to construct water resources scenarios for possible future climate changes.

The hydrogeochemical processes and water quality index of Barak Valley of NE India has carried out to delineate the processes controlling the quality. 33 water samples representing river, pond, lake, paleochannel , groundwater were selected. Analyses using correlation matrix, scatter plots, Schoeller, Gibbs, Trilinear, Ternary diagrams and water quality index were examined. The water type is characterized by high HCO 3 (70% in SW and 66% in GW) and depleted SO4 (

The late Holocene histories of Walker Lake and the Carson Sink were reconstructed by synthesizing existing data in both basins along with new age constraints from key sites, supplemented with paleohydrologic modeling. The repeated diversions of the Walker River to the Carson Sink and then back to Walker Lake caused Walker Lake–level fluctuations spanning ± 50 m. Low lake levels at about 1000, 750, and 300 cal yr BP are time correlative to the ages of fluvial deposits along the Walker River paleochannel, when flow was directed toward the Carson Sink. The timing and duration of large lakes in the Carson Sink were further refined using moisture-sensitive tree-ring chronologies. The largest lakes required a fourfold to fivefold increase in discharge spanning decades. Addition of Walker River flow to the Carson Sink by itself is inadequate to account for the required discharge. Instead, increases in the runoff coefficient and larger areas of the drainage basin contributing surface runoff may explain the enhanced discharge required to create these large lakes.

Based on the interpretation of satellite data and fieldwork in Kishtwar and surrounding area some geomorphic signatures of active tectonics which include uplifted river terraces, palaeochannels and their causative faults have been identified. The technique used in this study to delineate these geomorphic features includes the generation of digital elevation model (DEM), hillshaded images and anaglyphs from high resolution satellite data Cartosat-1. The anaglyphs and hill-shaded images helped to identify the fault scarp and palaeochannel of Chenab river. The ground truth further confirmed the displacement in the Quaternary river terraces lying along these faults. The presence of Quaternary fluvial sediments throughout the palaeochannel of Chenab river and the presence of wind-gap further confirmed that the river was once flowing from this area and shifted toward west in the recent geological past. Based on the geological evidences the present study leads to identification of a N-S striking fault which is represented by a >10 km fault scarp where the fluvial and lacustrine sediments are uplifted upto an elevation of 350–400 m from present river bed and another E-W striking fault that caused upliftment in river terraces and shifting of the river channel. These faults show clear evidence of active tectonics indicated by the displacement and deformation in the river terraces. Beside the geomorphological and geological evidences the seismic data of last three years obtained from the seismic observatories installed in this area ascertained the active nature of this area.

Earth fissures are a geologic phenomenon that mainly affects the medium with shallow surface soil and mainly developed in the Quaternary sediment cover. In the Yellow River-Qinghe River - Zhanghe River shallow buried paleochannel Band (HQZ-Qh2-II Band) on the North China Plain, 93 earth fissures are developed. Among them, 29 fissures are evolved in the Daming zone in the upper reaches of the paleochannel band. Thus, the zone belongs to a densely grouped fissure area. This study, through a series of field trenching and surveying, revealed that these earth fissures have unique plane distribution rules and profile structure features of short length (several meters to several hundred meters), shallow depth (smaller than 10 m) and good correspondence to Daming paleochannels. These basic characteristics reveal that unlike other tectonic earth fissures, Daming earth fissures are a new and unknown type of fissures, i.e., paleochannel-controlled earth fissures. Theoretical analysis of their features showed that they were formed due to the actions of gravity, primary joint factors and groundwater pumping activities and controlled by ancient river factors including paleochannels, sediments and groundwater. Among them, the process of Mode I can be summed up as “self-gravity action - tensile cracks - surface water scouring - earth fissures”. The process of Mode II is “primary join - surface water infiltration - piping - cave in - earth fissures”. The process of Mode III is “groundwater extraction - aquifer compression - inhomogeneous ground subsidence - earth fissures”. These formation mechanisms of paleochannel-induced earth fissures can be used to predict the fine distribution of shallow buried paleochannels and the overall migration process of the rivers. Thus, this kind of earth fissures is of great significance for understanding the underground paleogeomorphology (buried paleochannel) of the North China Plain and other alluvial plains of the world.

Sedimentary systems associated with ore deposits may act as mechanical dispersion agents of pathfinder elements at local and regional scales. The DeGrussa Cu-Au Volcanogenic Massive Sulfide (VMS) deposit (12.4 Mt @ 4.7% Cu and 1.8 g/t Au) was discovered in a deeply weathered landscape in Western Australia. The DeGrussa deposit is geochemically characterized as being enriched in Cu, Zn, Au and Ag, as well as significant enrichments in In, Mo, Se, Te, Bi, As, Cd and Co, and depletions in Nb, Hf, Th, REE, Cr, Ni, V, Sc and Ba. The Cenozoic palaeochannel sedimentary package that overlies the DeGrussa deposit displays elevated Cu, Zn, Au, and Ag concentrations, as well as significant enrichments in Cr, Ni, V, Sc, In, Mo, Se, Te, Bi, As, Cd and Co, and a remarkable depletion in REE. The palaeochannel sedimentary package shows similarities in its chemical signature to the DeGrussa deposit and associated basement rocks. However, due to the complexity of the landscape evolution and weathering impacts, there is uncertainty regarding the source(s) of this anomalous signature. It may represent (1) the geochemical signature of the immediately underlying basement rocks and/or the DeGrussa deposit; (2) concentration related to the weathering intensity experienced by the sediments, (3) concentration related to the cannibalistic nature of the sedimentary system, resulting in the reworking of previous deposits, or (4) a combination of the above. The Cenozoic channel clay deposits display strikingly depleted values of total REE (TREE) content, which has been interpreted to indicate that the palaeochannel clay units were mostly derived from weathering of proximal dolerite, with no mixing with other weathering products. This, in combination with high Mo, In and Se, and elevated Cu, Zn, Au, and Ag concentrations, may represent the relics of the DeGrussa footprint. Chromium Ni, V, and Sc are interpreted as being sourced mainly from the mafic basement units. Despite the geochemical signatures reported, this study has discovered that the metal geochemical footprint observed in the palaeochannel sedimentary package represents the footprint of the DeGrussa deposit. Hence the geochemistry of the transported cover can be used as an efficient tool for mineral exploration in specific landscape contexts, since the cover can preserve key elemental vectors of the mineral deposit and the geochemical signature of the basement rocks.

Despite paleochannels play a key role in the evolution of aeolian dune patterns, little attention has been paid on the interactions between paleochannels and aeolian processes. The objective of this article is to analyze the interactions between paleochannels and aeolian processes and their implications on the aeolian dune patterns. One site in the Kuruk Tagh Desert in eastern margin of the Tarim Basin, northwestern China is selected as the case study area. We analyze the sedimentary environment of the aeolian dunes around paleochannels based on the grain-size parameters. Furthermore, we present spatial and temporal dynamics of the vegetation and aeolian dunes around the paleochannels. The results indicate that: (1) ground water determines the spatial distribution of the vegetation and controls the evolution of aeolian dune patterns indirectly; (2) aeolian dunes around the paleochannels are initially controlled by fluvial and aeolian processes collectively. Then, the aeolian processes always play a dominant role after the drying up of these paleochannels; (3) the paleochannels in aeolian processes dominated areas ultimately evolve into a belt sand source due to the deposition of aeolian sediments and the encroachment of aeolian dunes. The timescale of the paleochannels’vanishment depends not only on the depth and width of the channels, but also on the angle between bedform orientation and prevailing sand flux direction.

Recent exploration has revealed that deep-seated and large groundwater reservoirs in Africa’s intracontinental basins can be regarded as an additional strategic resource for supply of drinking water. The origin, genesis and recharge of these groundwater reservoirs, however, are still poorly understood. A multidisciplinary approach involving remote sensing, geophysical surveys and hydraulic investigations, as well as hydrochemical and isotope studies, was pursued to gain better insight into the genesis and the potential of a recently discovered lower Kalahari aquifer (LKA) located in the Zambezi Region (Namibia). The study shows that regional tectonic activity associated with the propagation of the Okavango Rift Zone had a tremendous impact on the drainage evolution and hydrogeological setting of the region. Furthermore, there is geomorphological evidence that the LKA—prior to tectonic subsidence and burial—was part of a paleochannel of the upper Zambezi River. Hydraulic continuity could be confirmed by geochemical evolution down the flow path. Cation exchange combined with dissolution of calcite progressively produces alkalinity and sodium and consumes calcium in the north–south direction. Comparison of stable isotope content of the LKA with modern rainfall indicates that the recharge occurred under cooler climate conditions. Analysis of 14C concentrations and 36Cl/Cl ratios show that the age of the groundwater exceeds 100 ka and is hence older than presumed. It is concluded that the assessment of the sedimentology, tectonic structures and geochemistry are key factors for understanding both the paleoclimatic and modern recharge processes of deep-seated aquifer systems.

Lowland multiple-channel rivers are characterised by floodplain-corridor heterogeneity, high ecological and heritage value, and can be in quasi-stable states. This holistic study of a surviving temperate zone example (Culm, UK) uses geomorphological mapping, 14C, direct sediment dating (OSL, fallout radionuclides), and palaeoecology. This reveals the evolution of a channel-floodplain system from an initial braided state in the Late Pleistocene to its late Holocene anastomosing state. After the Pleistocene-Holocene transition the reduced channel system incised into its braid-plain, only able to rework gravels locally due to reduced competence in relation to inherited bounding sediment calibre. This resulted in the creation of terrace islands, palaeochannels, and a stable anastomosing pattern dominated by channel junctions, bifurcations and palaeochannel intersections. Survey, coring and excavation reveal a persistence of mid-channel bars and riffles at channel junctions, and where channels crossed palaeochannel fills. In common with most other European lowland rivers this system evolves in the later Holocene due to both climate and catchment changes with a major hydrological critical transition in the mid-Holocene (c. 5300 BP). However, in the case of the Culm, the increase in fine sediment supply often seen in lowland catchments in the Middle-Late Holocene, occurred later, and was insufficient to convert the system to a single medium-low sinuosity channel-floodplain. This allowed the persistence of high heterogeneity and biodiversity (including the persistence of riffle beetles) as part of multiple-scales of non-uniformity. Indeed the pool-riffle persistence is an example of this system's non-uniformity, being due, at least in part, to the effects of previous channel history. This paper reveals why this river survived in a multichannel state, and by implication, why others did not. These results are being used in the bespoke eco-heritage management of the Culm, but could also inform the restoration of other former multi-channel lowland temperate river systems worldwide.

Long, J.H.; Hanebuth, T.J.J.; Alexander, C.R., and Wehmiller, J.F., 2021. Depositional environments and stratigraphy of Quaternary paleochannel systems offshore of the Georgia Bight, southeastern U.S.A. Journal of Coastal Research, 37(5), 883–905. Coconut Creek (Florida), ISSN 0749-0208. Paleochannels are common subsurface geological features beneath inner continental shelves and coastal plains and are important archives of ancient depositional environments. This study, focusing on a 450-km portion of the inner continental shelf of the SE United States, adds to understanding of the timing of paleochannel development, the paleoenvironments in which they formed, and the mechanisms that drove their formation. Integrated analysis of 1089 km of high-resolution seismic reflection data and 12 sediment cores reveals that (1) most paleochannels documented here formed in backbarrier environments (estuarine or lagoonal) and were subsequently filled during transgression or following avulsion, preserving mud-rich, tidally influenced deposits; (2) the preservation of nonmarine deposits is rare; (3) paleochannels are either solitary or amalgamated, forming paleochannel complexes within which they are arranged in multistory (vertically stacked) or multilateral (horizontally offset) configurations, a product of local hydrodynamic conditions, antecedent geology, glacioeustatic cycles, and regional isostatic adjustments; and (4) a general southerly increase in the overall degree of channelization is observed across the Georgia Bight, a function of long-term accommodation, interaction with underlying stratigraphy, and dominant coastal processes. The composition and spatiotemporal distribution of paleochannel systems has implications for understanding the long-term evolution and preservation of complex coastal systems and informing regional Quaternary sea-level reconstructions.

Quantitative reconstruction of palaeohydrology from fluvial stratigraphy provides sophisticated insights into the response, and relative impact, of tectonic and climatic drivers on ancient fluvial landscapes. Here, field measurements and a suite of quantitative approaches are used to develop a four-dimensional (space and time) reconstruction of palaeohydrology in Late Cretaceous palaeorivers of central Utah, USA — these rivers drained the Sevier mountains to the Western Interior Seaway. Field data include grain-size and cross-set measurements and span five parallel fluvial systems, two of which include up-dip to down-dip transects, across seven stratigraphic intervals through the Blackhawk Formation, Castlegate Sandstone and Price River Formation. Reconstructed palaeohydrological parameters include fluvial morphologies (flow depths, palaeoslopes, palaeorelief, and planform morphologies) and various hydrodynamic properties (flow velocities, water discharges, and sediment transport modes). Results suggest that fluvial morphologies were similar in space and time; median flow depths spanned 2–4 m with marginally greater flow depths in southerly systems. Meanwhile palaeoslopes spanned 10-3 to 10-4, decreasing downstream by an order of magnitude. The most prominent spatio-temporal change is an up to four-fold increase in palaeoslope at the Blackhawk–Castlegate transition; associated alluvial palaeorelief is tens of metres during Blackhawk deposition and >100 m during Castlegate Sandstone deposition. We observed no change in unit water discharges at the Blackhawk–Castlegate transition, which argues against a climatically driven increase in palaeoslope and channel steepness. These findings instead point to a tectonically driven palaeoslope increase, although one limitation in this study is uncertainty in palaeochannel widths, which directly influences total water discharges. These reconstructions complement and expand on extensive previous work in this region, which enables us to test the efficacy of quantitative reconstruction tools. Comparison of results with facies-based interpretations indicates that quantitative tools work well, but inconsistencies in more complex reconstructions (e.g. planform morphologies) highlight the need for further work.

The Alsatian Upper Rhine floodplain (northeastern France) is characterized by a complex anastomosing network of paleochannels inherited from Late Glacial braided fluvial pattern of the Rhine system. These paleochannels are filled by mixed or stratified clastic and organic sediments originating from different sediment sources. Identifying these sediments' provenance is critically important for understanding past surface processes and reconstructing the Upper Rhine Valley evolution in the course of the Holocene. This study employed mid-infrared spectroscopy to determine the source of sediments and, therefore, understand which rivers may have contributed to the paleochannel infilling and establish the main patterns of filling through time. Sediment samples with unknown sedimentary provenance were collected in 16 sites consisting of paleochannels and the Ill River's levees. Mid-Infrared spectroscopic analyses were carried out on powdered (< 2 mm) samples using a Frontier Spectrometer (PerkinElmer) equipped with Diffuse Reflectance Infrared Fourier Transform accessory. Statistical analysis (Discriminant Analysis - DA) was performed to compare the spectral signatures obtained from the samples and a previously established reference spectral dataset (Chapkanski et al. 2020) covering potential sediment sources in the Upper Rhine area (the Rhine, Ill, and Vosges tributaries). The results showed well-contrasted sediment sources, with multiple rivers contributing to the paleochannel infilling history. The sediments were found to originate from the Rhine and Ill River systems and, to a lesser extent, Vosges tributaries. Some channels have an exclusively Alpine Rhine catchment origin while others showed purely Ill signatures. However, for most of the channels, infilling sources changed over time, presenting a relatively complex mixture of multiple sediment sources, indicating the lateral shifting of the two rivers within the alluvial plain. The results confirm that Mid-infrared spectroscopy (MIRS), combined with discriminant analysis, can give highly-specific determinations to sediments' sources. Thus MIRS-DA technique shows the potential of its being applicable as a rapid, low-cost, and efficient alternative method for provenance analysis of fluvial deposits in large, complex floodplains.

The lower reaches of the River Ure, on the flanks of the Pennine Hills in northern England, contain sedimentary and erosional landforms that are a record of fluvial activity during deglaciation and valley-glacier retreat at the end of the last (Devensian) glacial period, and in the subsequent post-glacial Holocene. Terraces and channels, most of which are now relict features well above the altitude of the present river, attest to the impacts of massive meltwater discharge and deposition of sand and gravel outwash, and dynamic river regimes with rapid incision. Through field survey, we have created a detailed geomorphological map of these landforms and glacial and fluvioglacial surface deposits, as well as the terraces and palaeochannels that were abandoned by the river due to avulsion and incision-driven course changes. We have recorded the nature of the outwash gravels, now effectively terrace features, from exposed sections in working quarries, one of which we discuss here. The palaeochannels have accumulated sediment fills and we have examined several which lie within the range of 100 and 16 m above present sea level. The results of lithostratigraphic, palynological, and radiocarbon analyses at two main and three subsidiary sites indicate that palaeochannel ages range from almost 14,000 to approximately 4000 calibrated years ago in a clear altitudinal sequence. The oldest are probably caused by rapid incision due to deglaciation-driven isostatic uplift. The similarity in date of the three downstream sites suggests that a late Holocene combination of climatic deterioration and increased human activity in the catchment caused instability and entrenchment. Pollen data from the channel fills provide relative dating, and agree well with pollen records from other regional Lateglacial and Holocene sites. Non-pollen palynomorph (NPP) analysis at one of the sites allows reconstruction of the hydrological history of channel infill. This research shows that the application of an integrated suite of research techniques can yield a highly detailed understanding of fluvial evolution and landscape history.

The paleotopography of the city ofGadir-Gadesis a fundamental element for understanding the historical process that took place in this unique area of the Atlantic-Mediterranean environment. Recent archaeological and geo-archaeological activities in the central part of the ancient “Bahía-Caleta” paleochannel (Valcárcel Building, 2018) have demonstrated the existence of an active anchorage located between 20 and 40 mcircadepth below the current sea level, very fertile from an archaeological point of view; of whose interpretation it can be inferred that this natural channel was open between archaic Phoenician age and at least the Early Roman Empire. This singular finding affects the reinterpretation of the paleotopography of the gaditan islands and the urbanism of the ancient city, that was developed in an insular environment, in front of which it was thought until the date. This paper presents these new findings and reflects on the historical-archaeological implications derived from them, opening suggestive new lines of research for the future., La paleotopografía de la ciudad deGadir-Gadeses un elemento fundamental para la comprensión del proceso histórico acontecido en este ámbito tan singular del entorno atlántico-mediterráneo. Recientes actividades arqueológicas y geoarqueológicas en la parte central del antiguo canal “Bahía-Caleta” (Edificio Valcárcel, 2018) han demostrado la existencia de un activo fondeadero ubicado entre 20 y 40 mcircade profundidad bajo el actual nivel del mar, muy fértil desde un punto de vista arqueológico, de cuya interpretación se infiere que este canal natural estuvo abierto entre época fenicia arcaica y al menos el Alto Imperio. Este singular hallazgo afecta a la reinterpretación de la paleotopografía de las islas gaditanas y al urbanismo de la ciudad, que se desarrolló en un entorno insular, frente a lo que se pensaba hasta la fecha. En este trabajo se presentan estos nuevos hallazgos y se reflexiona sobre las implicaciones histórico-arqueológicas que se derivan del mismo, abriendo sugerentes líneas inéditas de investigación para el futuro.

Two stages of high-discharge fluvial deposition during the last phase of the Late Holocene are recorded in the infilling of a palaeochannel in the distal reach of the Pecora river, a small catchment along the Tyrrhenian coast of Tuscany (Central Italy). Facies analysis shows an abrupt change from high sinuosity gravelly-sandy river (III-I millennium BC) to shallow braided channel bars (VII-XII century AD). The second stage features the occurrence of very abundant sediments originated from the erosion of the upstream Calcareous Tufa environments, coupled with abundant fine- to coarse-sized charcoal fragments, derived by selective fires sequentially affecting the wetlands, the riparian vegetation, and the surrounding slopes. Geomorphological and stratigraphical analysis of the Pecora river catchment indicates that the widespread wetlands in which Calcareous Tufa were developing were already active around 4 ka cal BC and their formation ended permanently around the XIII century AD. The age of the decline of the tufa systems in the Pecora catchment seems to disagree with most of those recorded in Europe. Contrastingly, their inactivity is coeval with the occupational period of the medieval archaeological site of Vetricella, located in the surroundings of the palaeochannel, and the onset of upstream wetland reclamation and hydraulic works. These changes led to the reclamation of karst depressions, the capture of karst springs, the bypass of barrages and the deep downcutting of the tufa terraces and the drainage of the corresponding wet environments. This study discusses the anthropogenic factors that during the Early Middle Age affected the Pecora catchment and promoted a permanent change in its physical and biological environment with a new assessment of the river course and the reclamation of large portions of floodplains previously permanently flooded. This study provides new data regarding the decline of fluvial tufa in the Mediterranean area and emphasises the Early Medieval anthropogenic forcing mechanism tethered to agricultural practices and land management, contrasting with the classic historical model which suggests an almost complete abandonment of the alluvial and coastal plains.

In this chapter present results obtained from last-years studies uranium ores from seven paleochannel-type deposits of Khiagda Ore Field at Vitim uranium ore region, Russia. All deposits belong to sandstone economic type, basal channel subtype; in Russian it commonly called as paleovalley, paleo-riverbed or paleo-streambed. Here predominant ore component is ningyoite in crystalline and mineraloid form. These ores, little-known previously and unknown earlier in Russia, represent a new type of commercial uranium ores—phosphatic black’s one. The high dispersity of U-ore substance makes necessary choice of AEM (scanning and transmission) as the main mineralogical research method. Brief geological background and results of AEM investigation of uranium ores composition (uranium and associated mineralization) on Khiagda Ore Field deposits are given.

Palaeoecology, through the analysis of the interactions between environmental factors and ecosystems, refines the knowledge of the structuring process of plant communities and helps to understand the complexity of past environments. However, it is necessary to analyse the taphonomic phenomena (deposition, conservation, degradation) affecting plant macrofossil assemblages in order to perform relevant palaeoecological analyses. Indeed, plant macrofossils may be under or over-represented in carpological assemblages, depending on the resistance of their cell membranes and the sedimentary condition deposits. For this reason, it is necessary to estimate the representative quality of the conserved part as a source of information. Like all archaeological documents, the plant archives are distorted by the processes of formation of the sedimentary levels and, ignore the diagenetic history of the sedimentary layers could lead to wrong palaeoecological interpretations. To this aim, we analysed plant macrofossils contained in the wet sediments of a Meuse palaeochannel (Autrecourt-et-Pourron, Ardennes, France). This archaeobotanical study of an oxbow lake dated to the Preboreal (11.7–10.7 ka cal. BP), provides a reference of a taphonomic referential according to a hierarchy of organic remain preservations. This framework successfully helped the palaeoecological interpretations of the Autrecourt-et-Pourron off-site, and it has brought robustness to environmental history reconstruction of the early Holocene in the Ardennes Meuse.

Geological evaluation and groundwater assessment, especially in arid areas, are considerable targets for constructing recent and sustainable development communities. The current work aims to apply an integrated approach to acquire geologic structures and groundwater potentiality at highly deformed area. As a case study, remote sensing (RS), aeromagnetic, and geoelectrical data are conducted to delineate the subsurface structures and hydrogeological regime at Aswan City. Initially, remote sensing data with GIS software are utilized to delineate the surface structures and watershed configuration. Moreover, the reduced to magnetic pole (RTP) aeromagnetic data is processed and interpreted using appropriate filters. In an attempt to demonstrate the subsurface structures and basement relief maps, the RTP map was analyzed considering the RS data which was stated in previous stage. In the light of RTP aeromagnetic results and well logging data, the direct current resistivity (DCR) sounding is executed particularly along paleochannel and flood plain portion. Due to the inversion process problem of DCR field data, advanced solutions and algorithms are applied to improve the property of the results. Based upon overall results mentioned above, the correlation between subsurface structures and aquifer formation can be monitored. The present approach can be applied for groundwater exploration in this and other similar geological and hydrogeological environments around the world.

Natural metal background levels in sediments are critical to assess spatial and temporal trends of contamination in hydrosystems and to manage polluted sediments. This is even more sensitive that multi-factors such as geogenic basement, depositional context, and past or long-term pollution can affect the level of metals in sediments. This article provides natural metal background levels and ancillary data (location, chronology, grain-size, total organic carbon – TOC) in pre-industrial sediments along the Rhone River (France). Two distinct areas were selected to take into account the geological variability of the watershed: the Dauphine Lowlands (Upper Rhone River) and the Tricastin Floodplain (Middle Rhone River). On each area, the sediment cores were retrieved from palaeochannel sequences and the sampled sections were dated by radiocarbon from the Roman to the Modern Times (AD 3–1878). Regulatory metals (Al, Fe, Cd, Cr, Cu, Ni, Pb, and Zn) and other trace elements (Ba, Co, Li, Mg, Mn, Na, P, Sr, Ti, V) were analysed following both Aqua Regia (AR) and Total Extraction (TE) procedures. Classically, TE provides metal concentrations greater than AR because TE includes crystalline lattice, while AR is close to the potentially bio-accessible part of metals (used for ecotoxicological purposes). Due to the small number of samples and to the non-normal distribution of the results, a median-based approach was chosen to establish the geochemical background values and ranges (MGB) for each sample and area. These MGBs are valuable to identify pollution sources, to characterise a contamination (spread and timing), and to estimate the state of rivers regarding pollution legacy. Along the Rhone River, these two continental MGBs were used to reconstruct the metal geo-accumulation trajectories in river sediments from 1965 to 2018 [1].

В настоящее время для многих недропользователей юга России представляют интерес нефтегазоперспективные объекты неглубокого залегания в виду небольших по- тенциальных затрат на их освоение. Данная работа посвящена изучению подобного объекта, связанного с перспективами выявления неантиклинальных ловушек углеводородного сырья. Цель исследования. В ходе сейсморазведочных работ 2008‑2019 гг. на территории Каралатского лицензионного участка (Астраханская область, восток Каракульско-Смушковской зоны поднятий) по сейсмическим данным был выявлен уникальный по размерам и форме для данного района исследования палеорусловой объект, приуроченный к эрозионному врезу по кровле верхнемеловых отложений. Основным направлением ис- следования являлось изучение его строения, природы и перспектив освоения. Методы исследования. Изучение объекта проводилось на основе имеющихся данных сейсморазведки (метод общей глубинной точки, двумерная модификация). Выполнена обработка и интерпретация накопленного сейсмического материала, сделан расширенный анализ скоростей, проведены структурные построения. Проведено ис- следование динамики волновой картины на качественном уровне и путём атрибутного анализа. Получен- ные результаты. Палеорусло формировалось, предположительно, в неогене, в условиях наклона терри- тории с севера на юг. В ходе его изучения было уточнено строение, конфигурация, предварительно оце- нены особенности залегания слагающих пород. Протяжённость объекта по оси – 25,4 км, площадь – 65,4 кв. км, глубина – 750‑1050 м. Точную стратиграфическую принадлежность выполняющих врез осадков ещё предстоит уточнить в виду отсутствия соответствующих данных глубокого бурения на территории исследования. Результаты привязки к скважинам сопредельного Кирикилинского участка указывают, что вмещающие породы относятся к верхнему мелу, на отдельных участках врез достигает и нижнемеловых осадков. Изучение аналогичных объектов и история геологического развития района позволяют предпо- ложить, что выполняющие врез породы относятся к плиоцену. Исследования указывают на то, что объект приурочен к главному руслу древней дельты или нижнему течению реки, аналогичной современной р. Волга. Энергия волн, отраженных от горизонтов заполняющих пород, выше, чем от горизонтов вмеща- ющих, что нехарактерно для известных палеорусловых объектов сопредельных территорий. При ско- ростном анализе волнового поля отмечены аномально низкие значения эффективных скоростей в зоне объекта. В результате получено подтверждение палеорусловой природы объекта, установлено сложное и непостоянное залегание пород с признаками латеральной смены литологического состава, возможного наличия флюидов. Полученные данные позволили предварительно оценить перспективы нефтегазонос- ности палеоканала и наметить планы дальнейшего изучения геофизическими методами, а также поста- новки поискового бурения Today carbohydrates blocks holders in south of Russiatake an interest inoil and gas potential objects with superficial bedding because of its reasonableexplorationcosts. This research work is devoted to study of so object concerned with carbohydrates traps revelation prospective. Aim. The unique because of its size and shape paleo-channel object confinedwith erosive cut on the top of cretaceous sediments was discovered with seismic data as the result of seismic prospecting works in 2008‑2019 on the Karalatskiy block (Astrakhan region, East of Karakulsko-Smushkovskaya uplift zone). The main direction of the research was the studying of its structure, origin and exploration prospective. Methods. The study was based on available seismic data (common reflection point method, 2D modification). Processing and interpretation of total seismic data volume were realized, expanded velocity analysis was performed, structure mapping were carried out. The qualitative leveldynamic analysis and attribute analysiswere realized. Results. It is supposed that ancient riverbed were forming in Neogene in condition ofinclination of territory in south direction. The structure and configuration of this object were defined more precisely and bedding peculiarities were preliminary estimated during studying. The extension of the object is 25.4 kilometers, the area is 65,4 square kilometers, the depth is from 750 to 1050 meters. Exact stratigraphy of sediments filling up the cut, needs to be defined more exactly because of lackof boring data on the field. The results of matching with wells of neighbor Kirikilinskiy block show late cretaceous age of base rocks, some spans of the cut reach lower cretaceous sediments. The study of similar objects and geological history of the region allow supposingthat rocks filling up the cut belong to Pliocene. Research shows that the object isconfined to mainchannel of ancient delta or lowerpart of ancient river similar to present-day Volga River. Filling up rocks horizons reflected waves energyis higher than for base rocks, this occurrenceis not typical for paleo-channel objects of contiguous areas. Abnormally low values of RMS velocities were detectedduring the velocity analysisin the object area. The confirmation of paleo-river genesis of the object was achieved as the result, complex andinconstant structure of the rocks with lateral lithology changing andpotential presence of fluids was detected. The result data allowed to estimate preliminary perspectives of oil and gas content for the paleochannel and to outline the subsequent geophysical study and exploration drilling performance.

International audience; In this paper, we test the recent hypothesis of the occurrence of five to seven tsunami generations, that would have struck the ancient harbour basin of Ostia (Italy), and the lower channel of the Tiber River during the last three millennia. Because these steady disaster events would have deep implications on our knowledge of the history of Rome, we reviewed the pluridisciplinary data available at the Tiber River mouth. Considering sedimentological, geomorphological, micropalaeontological, geochemical, chronological and historical evidence, there is currently no conclusive palaeoenvironmental evidence to suggest past tsunami inundations near Ostia . River mouths are not the best context in which to identify tsunami deposits. High fluvial and coastal mobility generated by regular floods and storms hardly record single High-Energy Events (HEE) from floods, storms, or tsunamis. Sediments are regularly reworked at the river mouth both in the river channel and on the close shoreface. Mixed fluvial and marine influences and the seasonal formation of a salt wedge at the mouth of the Tiber create specific estuarine assemblages for micro- and macrofauna. The layer called High-Energy Event 1 (HEE-1) on the palaeo-shoreface close to the river mouth and HEE-4/5 in the point bars of the Tiber channel are most probably layers reworked several times by fluvio-coastal events (storms and/or floods). HEE-3 sealing the Republican harbour of Ostia is clearly related to flood deposits. Complementary analyses would be necessary to definitively identify the origins of the HEE-2 and HEE-7 in the harbour, and HEE-6 in the palaeochannel or floodplain. Based on the data available, we show how other processes than tsunami inundations could be just as accountable for these coarse-grained sediment layers (storm deposit, flood deposit, or riverbank deposit). This review puts into question the use of pluridisciplinary proxies to identify palaeotsunami deposits. In addition, we demonstrate how high Pb concentrations constitute a robust proxy to definitively refute the presence of palaeotsunami deposits. As such, this study will be beneficial to a large community of specialists in coastal research.

Over the past few millennia, meandering fluvial channels drained coastal landscapes accumulating sedimentary successions that today are permeable pathways. Propagation of pollutants, agricultural exploitation and sand liquefaction are the main processes of environmental interest affecting these sedimentary bodies. The characterization of these bodies is thus of utmost general interest. In this study, we particularly highlight the contribution of noninvasive (remote and ground-based) investigation techniques, and the case study focuses on a late Holocene meander bend of the southern Venetian Plain (Northeast Italy). Electromagnetic induction (EMI) investigations, conducted with great care in terms of sonde stability and positioning, allowed the reconstruction of the electrical conductivity 3D structure of the shallow subsurface, revealing that the paleochannel ranges in depth between 0.8 and 5.4 m, and defines an almost 260 m-wide point bar. The electrical conductivity maps derived from EMI at different depths define an arcuate morphology indicating that bar accretion started from an already sinuous channel. Sedimentary cores ensure local ground-truth and help define the evolution of the channel bend. This paper shows that the combination of well-conceived and carefully performed inverted geophysical surveys, remote sensing and direct investigations provides evidence of the evolution of recent shallow sedimentary structures with unprecedented detail.

Geoarchaeological cores were retrieved in the centre of the old “Bahia-Caleta” palaeochannel located between the Erytheia and Cotinusa islands in the former Cadiz archipelago, in present-day southern Spain. The unprecedented coring depth (~ 35–50 m) allowed us to identify the bottom of a Phoenician–Punic and Roman harbour. Located at 20–40 m b.s.l. in the sedimentary sequence, silty sand deposits reveal a deep semi-protected shelter with abundant ceramic and archaeobotanical findings. Based on these new results, the palaeotopography of the islands of Cadiz is reinterpreted, demonstrating the presence of a harbour accessible from the west and possibly from the east until (at least) the Roman period. This major discovery opens meaningful perspectives for archaeological, geomorphological and palaeoenvironmental research.

Buried channels are the subsurface geomorphic features, which illustrate the pattern and evolution of paleodrainage system in an area. Old topographical map (1967) of Kottumangalam coast of southwest Tamil Nadu, India, revealed that surface channel was directly drained into the sea, but in the present situation the same channel is not depicted on maps which indicate the channel has buried. The present study is focused to identify the location and architecture of modern buried channels through ground-penetrating radar (GPR) technology in study area. The study place is highly influenced by natural events (tsunami, high tide flood, and storm), southwest monsoon, and high waves. A 200-m-long subsurface profile was generated using GPR survey parallel to the coast. Geophysical (amplitude, attenuation, magnitude), geological (channel bed, channel bank, erosional surface, volume of sedimentation), and geographical (old topographical map) evidence were considered to identify and locate the paleochannels and to understand their developments at different stages. Two buried channels (at 120–136 m and 184–200 m in the GPR profile) were traced in between 0.5 and 3.2 m depth and it portrays three stages of evolution. High amplitude reflection and dipping of sedimentary beds in the channel banks are the notable signatures of paleochannel in the study area. Flat attenuation curves and velocity differences in the zone of the buried channels disclosed the presence of buried channels. The channels were buried due to changing conditions of marine, aeolian, and fluvial processes. Five distinct sedimentary layers, as shown by variance of reflections of radar wave from subsurface sand material at various depths are recognized as (i) saturated, (ii) semi-saturated, (iii) compact, (iv) transition, and (v) recent upper layer, besides that two erosional surfaces (around 0.8 and 1.5 m depth) were identified. The current study provides a better understating of mapping and identifying the occurrences of paleochannels in coastal environment using GPR technology.

Today, coastal cities worldwide are facing major changes resulting from climate change and anthropogenic forcing, which requires adaptation and mitigation strategies to be established. In this context, sedimentological archives in many Mediterranean cities record a multi-millennial history of environmental dynamics and human adaptation, revealing a long-lasting resilience. Founded by the Phoenicians around 3000 years ago, Cádiz (south-western Spain) is a key example of a coastal resilient city. This urban centre is considered to be one of the first cities of western Europe and has experienced major natural hazards during its long history, such as coastal erosion, storms, and also tsunamis (like the one in 1755 CE following the destructive Lisbon earthquake). In the framework of an international, joint archaeological and geoarchaeological project, three cores have been drilled in a marine palaeochannel that ran through the ancient city of Cádiz. These cores reveal a ≥50 m thick Holocene sedimentary sequence. Importantly, most of the deposits date from the 1st millennium BCE to the 1st millennium CE. This exceptional sedimentary archive will allow our scientific team to achieve its research goals, which are (1) to reconstruct the palaeogeographical evolution of this specific coastal area; (2) to trace the intensity of activities of the city of Cádiz based on archaeological data, as well as geochemical and palaeoecological indicators; and (3) to identify and date high-energy event deposits such as storms and tsunamis.

The need to predict accurately the volume, timing and location of sediments that are transported from an erosional source region into a basin-depocentre sink is important for many aspects of pure and applied sedimentological research. In this study, the results of three widely used methods to estimate sediment flux in ancient sediment routing systems are compared, using rich input datasets from two systems (Eocene South Pyrenean Foreland Basin, Spain and late-Pleistocene-to-Holocene Gulf of Corinth Rift Basin, Greece) for which mapped, dated sediment volumes provide an independent reference value of sediment accumulation rates. The three methods are: (1) the empirical BQART model, which uses values of drainage basin area, relief, temperature, lithology and water discharge; (2) empirical scaling relationships between characteristic geomorphological parameters of sediment-routing-system segments; and (3) the “fulcrum” model, which uses the palaeohydrological parameters of trunk river channels to estimate downsystem sediment discharge. The BQART model and empirical geomorphological scaling relationships were originally developed using modern sediment routing systems, and have subsequently been applied to ancient systems. In contrast, the “fulcrum” model uses hydrological scaling relationships from modern systems, but was developed principally for application in ancient systems. Our comparative analysis quantifies the sensitivity of the three methods to their input parameters, and identifies the data required to make plausible estimates of sediment flux for ancient sediment routing systems. All three methods can generate estimates of sediment flux that are comparable with each other, and are accurate to at least one order of magnitude relative to independent reference values. The BQART model uses palaeoclimatic and palaeocatchment input data, which are accurate for sub-modern systems but may be highly uncertain in deep-time systems. Corresponding estimates of sediment flux are most sensitive to the accuracy with which the palaeocatchment area is constrained and to palaeoclimatic parameters that reflect temperature and precipitation. The “fulcrum” model uses palaeohydrological input data; its sediment-flux estimates are sensitive to palaeochannel dimensions and, in particular, the duration of bankfull discharge, which is invariably difficult to constrain accurately in deep-time sediment routing systems. This uncertainty can give rise to large potential ranges of sediment-flux estimates. Geomorphological scaling relationships offer comparable, order-of-magnitude accuracy for both sub-modern and deep-time sediment routing systems in which geomorphological segments can be identified, but when used on relatively small sediment routing systems the ranges of sediment volumes deposited can vary greatly, limiting the utility of the technique. We suggest that methods to estimate sediment flux should be chosen for a particular sediment routing system based on the types and uncertainty of available data. Where input parameter values are highly uncertain, such as in deep-time systems, Monte Carlo simulation is an effective tool to calculate probability distributions of estimated sediment flux.

The Kuiseb River is one of the major ephemeral rivers of Western Namibia, setting the northern limit of the Namib Sand Sea and outflowing in the Atlantic Ocean at Walvis Bay. Such ephemeral rivers are of the highest importance for the country since they are related both to recent past climatic conditions and to potential water resources. Using high-resolution radar images from the Japanese ALOS-2 satellite, we mapped for the first time the numerous channels hidden under the surface aeolian sediments: while the non-permanent tributaries of the Kuiseb River appear north of its present-day bed, a wide paleochannel system running westward, assumed by previous studies, could be clearly observed in the interdune valleys in the south. Radar-detected channels were studied during fieldwork in May 2019, which produced both subsurface ground-penetrating radar profiles and high-resolution drone-generated digital elevation models. It allowed us to confirm the existence of the &ldquo, Paleo&ndash, Kuiseb&rdquo, drainage system, a remnant of the Holocene history of the Kuiseb River, moving northward under the progression of the Namib Sand Sea. Our observations also contribute to the explanation of the young age of the linear dunes at the northern edge of the Namib Sand Sea, which are currently active and are pushing the Kuiseb River course toward the north.

International audience; Sedimentation regimes on the Great Barrier Reef margin often do not conform to more conventional sequence stratigraphic models, presenting difficulties when attempting to identify key processes that control the margin's geomorphological evolution. By obstructing and modifying down‐shelf and down‐slope flows, carbonate platforms are thought to play a central role in altering the distribution and morphological presentation of common margin features. Using numerical simulations, we test the role of the carbonate platforms in reproducing several features (i.e., paleochannels, shelf‐confined fluvial sediment mounds, shelf‐edge deltas, canyons, and surface gravity flows) that have been described from observational data (seismic sections, multibeam bathymetry, sediment cores, and backscatter imagery). When carbonate platforms are present in model simulations, several notable geomorphological features appear, especially during lowstand. Upon exposure of the shelf, platforms reduce stream power, promoting mounding of fluvial sediments around platforms. On the outer shelf, rivers and streams are re‐routed and coalesce between platforms, depositing shelf‐edge deltas and incising paleochannels through knickpoint retreat. Additionally, steep platform topography triggers incision of slope canyons through turbidity currents, and platforms act as conduits for the localized delivery of land and shelf‐derived sediments to the continental slope and basin. When platforms are absent from the topographic surface, the model is unable to reproduce many of these features. Instead, a more typical “reciprocal‐type” sedimentation regime arises. Our results demonstrate the essential role of carbonate platform topography in modulating key bedload processes. Therefore, they exert direct control on the development of various geomorphological features within the shelf, slope, and basin environments.

Preserved remnants of fluvial activity in deserts constitute evidence for changing boundary conditions. The Atacama Desert of northern Chile is the global end-member for aridity, so the history of relict stream networks in this region is a record of how landscapes develop under extreme conditions. On Pampa de Tana in northern Chile (19.4°S), a series of channel forms that are presently inactive but in the past flowed westward are incised into the surface of a fault bounded, topographically elevated portion of the El Diablo Formation, a regionally extensive, relict pediment. We measure cosmic-ray produced 10Be, 26Al and 21Ne in fluvial deposits to date the timing of abandonment of three channels and couple this with topographic profile information from a SPOT-6 derived, 2 m resolution digital elevation model. We find two of the channels were abandoned approximately >5.6 Myr and 2.0 Myr ago. One channel is still capable of flow and has ages suggesting it was fluvially active within the last few hundred thousand years. Using the paleochannel ages measured here and published ages for the end of aggradation of the El Diablo Formation we estimate the rates of fluvial channel incision before channel abandonment, and uplift rates on the faults after channel abandonment. Maximum uplift rates of ~12 m/Myr over the last 2 Myr are found. In general, while rates of uplift are relatively low they are several-fold more rapid than the rates of fluvial incision prior to channel abandonment. This implies that westward channel flow was interrupted by uplift of topography above a blind NW-SE striking reverse fault that affects the Central Depression, an alluvial forearc basin. We consider also that shrinkage of the upstream catchment area by stream capture, promoted via headward erosion and lateral expansion of adjacent canyons (quebradas) could be a factor in the abandonment of the channels on Pampa de Tana. Our results highlight the polygenetic nature of this landscape and show that relatively minor amounts of fault displacement in hyperarid regions can have implications for stream network evolution. Even subtle topographic uplift upstream should be taken into account when fluvial deposits are used as proxies for long-term environmental conditions.

Charcoal analysis, applied in sediment facies analysis of the Pecora river palaeochannel (Tyrrhenian southern Tuscany, Italy), detected the occurrence of past fire events in two different fluvial landforms at 800–450 BC and again at AD 650–1300. Taking place in a central Mediterranean district adequately studied through palaeoenvironmental and archaeological research, the investigation determined land changes, time phases and socio-economic driving forces involved in dynamic processes of fire. The fire sequences had purely anthropogenic origins and were linked to forest opening and reduction by local communities. Introduced by the Etruscans, fires dated to 800–450 BC involved mainly the forest cover on the hilly slopes, ensuring agricultural exploitation. From AD 650, fires contributed to Medieval upstream reclamation and vegetation clearing of flat swamplands. From AD 850 to 1050, the use of fire spread over a wider area in the river valley, increasing arable lands. Between AD 1150 and 1300, fires belonged to a regional forest clearance phase. Medieval fire episodes had a paramount importance in shaping and determining the character of the Tuscan Mediterranean landscape. From AD 850, Medieval fire clearing influenced regional vegetation history contributing to the decline of the dominant deciduous Quercus woodland. Open habitats became the new form of a clearly detectable agricultural landscape from AD 950. The use of fire clearing and the resulting landscape changes in the Pecora river valley depended on the political strategies adopted by Medieval authorities and marked, in fact, the progression of a cultural landscape still characterizing central Tyrrhenian Italy.

Despite the importance of channel avulsion in constructing fluvial stratigraphy, it is unclear how contrasting avulsion processes are reflected in stratigraphic-stacking patterns of channelized fluvial sand bodies, as a proxy for how river depocenters shifted in time and space. Using an integrated, geospatially referenced, three-dimensional data set that includes outcrop, core, and lidar data, we identify, for the first time in an outcrop study, a predictive relationship between channelized sand body architecture, paleochannel mobility, and stratigraphic-stacking pattern. Single-story sand bodies tend to occur in vertically stacked clusters that are capped by a multilateral sand body, indicating an upward change from a fixed-channel system to a mobile-channel system in each cluster. Vertical sand body stacking in the clusters implies reoccupation of abandoned channels after “local” avulsion. Reoccupational avulsion may reflect channel confinement, location downstream of a nodal avulsion point that maintained its position during development of the sand body cluster, and/or aggradation and progradation of a backwater-mediated channel downstream of a nodal avulsion point. Sand body clusters and additional multilateral sand bodies are laterally offset or isolated from each other, implying compensational stacking due to “regional” switching of a nodal avulsion point to a new, topographically lower site on the floodplain. The predictive links between avulsion mechanisms, channel mobility, and resultant sand body distributions and stacking patterns shown in our findings have important implications for exploring and interpreting spatiotemporal patterns of stratigraphic organization in alluvial basins.

Furious floods have become an omnipresent reality with the dawn of climate change and its transition to adulthood. Since climate change has now become an accepted reality, analysing the factors that favour or disfavour floods are an urgent requirement. Here we showcase the role of paleochannels, a product of migrating rivers, in a catastrophic flood in the south-western part of the Indian Peninsula. This study exposes whether these geomorphic features facilitate or impede floods. For the purpose of extracting paleochannels and floodwater mapping, we utilized multiple satellite datasets and took advantage of diversified feature selection algorithms. Paleochannels were demarcated viz., initial identification of a few paleochannels from literature and confirmation through high-resolution Google Earth (GE) images, followed by Principal Component Analysis (PCA) of Sentinel-2 images using Google Earth Engine (GEE), and a supervised classification of the principal bands 1, 2, and 3. False-positives were eliminated using Object-Oriented Analysis (OOA), which reduced the 964,254 polygons to 23,254. These polygons were visually affirmed using GE images that resulted in 115 paleochannels as the final collection. A few locations were verified through Vertical Electrical Sounding (VES) using the Schlumberger method. The features were analysed with the floodwaters of the 2018 catastrophic flood, extracted from Synthetic Aperture Radar (SAR) data, which was delineated for different temporal limits including the day of peak flood of August 17, 2018. During the peak flood, the inundation of the study area extended to 534.86 km2 with all the paleochannels getting immersed in floodwater. After 44 days of peak flood, the post-flood analysis revealed that when the floodwater receded 50%, the paleochannels emptied 87.39%, with the midland paleochannels discharging more than those of lowlands. Thus, such geomorphic features can be flood hotspots, but can be considered for discharging floodwater to mitigate flood risk in case of unprecedented rain.

The paleochannel of the Wenhekou–Liudaokou reach of the Yihe River was investigated using electrical soundings along the Zhuyong and Chuanliujie cross sections and drilling at the Chuanliuj...

This study derives a new function describing the relationship of channel bankfull discharge (Qbf) to channel width in modern rivers of the Murray-Darling Basin (MDB) of southeastern Australia and applies this to dated palaeochannels of seven rivers to quantify late Quaternary discharge history in this important basin. All rivers show high MIS3 and MIS2 Qbf, declining in the Holocene. The Qbf of modern MDB rivers is correlated with total catchment precipitation but comparison with palaeochannel Qbf estimates shows that while enhanced runoff efficiency is necessary to account for much larger late Pleistocene palaeochannels, either lower or higher precipitation rates could have prevailed. A strong association between relative palaeo- Qbf enhancement and temperature suggests a temperature-mediated mechanism controlling river discharge, such as the fraction of precipitation stored as snow and thawing in spring, the enhancement of orographic rainfall, or CO2 feedbacks with vegetation cover. Significantly enhanced MIS3 Qbf requires an additional mechanism, such as increased rainfall. These findings are consistent with others that increased moisture availability was associated with past colder climates, although this was not necessarily the result of enhanced precipitation.

Palaeochannels of lowland rivers provide a means of investigating the sensitivity of river response to climate-driven hydrologic change. About 80 palaeochannels of the lower Macquarie River of southeastern Australia record the evolution of this distributive fluvial system. Six Macquarie palaeochannels were dated by single-grain optically stimulated luminescence. The largest of the palaeochannels (Quombothoo, median age 54 ka) was on average 284 m wide, 12 times wider than the modern river (24 m) and with 21 times greater meander wavelength. Palaeo-discharge then declined, resulting in a younger, narrower, group of palaeochannels, Bibbijibbery (125 m wide, 34 ka), Billybingbone (92 m, 20 ka), Milmiland (112 m, 22 ka), and Mundadoo (86 m, 5.6 ka). Yet these channels were still much larger than the modern river and were continuous downstream to the confluence with the Barwon-Darling River. At 5.5 ka, a further decrease in river discharge led to the formation of the narrow modern river, the ecologically important Macquarie Marshes, and Marra Creek palaeochannel (31 m, 2.1 ka) and diminished sediment delivery to the Barwon-Darling River as palaeo-discharge fell further. The hydrologic changes suggest precipitation was a driving forcing on catchment discharge in addition to a temperature-driven runoff response.

The Riverine Plain in south-eastern Australia contains numerous palaeochannels that are much larger than the present rivers and provide evidence about past hydrological conditions. Previous research suggested optima in fluvial activity both before and after the peak of the Last Glacial Maximum (LGM; 21 ± 3 ka), and, in some cases, throughout the LGM. In this study, we revisit palaeochannel remnants of the Gum Creek and Yanco palaeochannel systems along the Murrumbidgee River, which drains the high-elevation catchments of the Australian Alps in south-eastern Australia. We date fluvial and aeolian sediments using single-grain optically stimulated luminescence (OSL) and apply thermoluminescence (TL) dating to a subset of samples. We compare the OSL ages to new and previously published TL ages and investigate reasons for age discrepancies between these methods, possible effects of partial bleaching and other factors that may affect luminescence ages. We propose a new OSL-based chronology for the Gum Creek and Yanco palaeochannel systems and assign periods of enhanced fluvial activity for the Tombullen and Yanco phases to 41–29 and 29–18 ka, respectively. Importantly, we infer that conditions of increased sediment and water discharge persisted for the Murrumbidgee River at the time of the LGM.

The results of studies in the paleochannel of the Volga River, which was discovered earlier on the northwestern slope of the Derbent Basin, Caspian Sea, are presented. Seismoacoustic profiling in the paleochannel, combined with placement of submerged buoy stations equipped with current gauges, water temperature gauges, and sediment traps showed that the channel is not silted and cold heavy water is transported along it to the deep sea part of the sea, avoiding the general water transit along the western coast of the Central Caspian Sea. The preliminary calculations show that water discharge through the channel to the near-bottom part of the sea can be about 8–10 km3/yr.

This paper reports the first reconstruction of storm-generated late Holocene and historical river floods in the North Island of New Zealand. The sedimentary infills of nine palaeochannels were studied in the lower alluvial reaches of the Manawatu River. Floods in these palaeochannels were recorded as a series of sand-rich units set within finer-grained fills. Flood chronologies were constrained using a combination of radiocarbon dating, documentary sources, geochemical markers, and palynological information. Flood units were sedimentologically and geochemically characterised using high resolution ITRAX™ X-Ray Fluorescence (XRF) core scanning and laser diffraction grain-size analysis. The longest palaeoflood record extends back ca.3000 years. The temporal resolution and length of the Manawatu record reflects accommodation space for fluvial deposits, channel dynamics and mobility, and high sediment supply. Floods that occurred in the Manawatu during the mid-1800s at the time of European land clearance and in the first decade of the twentieth century appear to be among the largest recorded in the last 3000 years.

The start of Nile-type trans-Saharan drainage systems in NE Africa during the Cenozoic is disputed. Stratigraphical and sedimentological data in Egypt are partly in conflict with the uplift history of potential source areas of water and sediment in East Africa. Here, we investigate outcrops of the Wadi Awatib Conglomerate in Sudan that provide the first evidence of northerly flowing Neogene rivers in the region. Dimension and relief of basal erosion surfaces, overall geometry of deposits and palaeocurrent indicators demonstrate that the deposits represent the fill of northward-oriented incised valleys. The conglomerates were deposited in deep gravel-bed rivers, by hyperconcentrated flows, tractions carpets and gravel bars, primarily during heavily sediment-laden floods of probably monsoonal origin. Stratigraphical and geomorphological relationships show that the deposits are between Eocene and Pliocene in age. Considering the structural history of the region and periods in the Cenozoic with palaeoclimatic conditions suitable for the production and transport of gravels, we hypothesize that the dramatic base-level fall during the Late Miocene Messinian salinity crisis in combination with a favorable palaeoclimate caused the incision of valleys and their subsequent filling with conglomerates. Sea-level change in the Mediterranean Sea and headward erosion of streams that were connected to the Egyptian Nile might have been the primary cause of valley incision and deposition of conglomerates, despite a location far inland from the coastline. We suggest that the deposits document a relatively young Neogene (Messinian to early Pliocene) trans-Saharan river system unrelated to uplift of the Ethiopian Plateau.

The Waikaia alluvial gold mine is hosted in a Pleistocene paleochannel that is buried beneath younger sediments beside the Waikaia River. The paleochannel sediments were derived primarily from loca...

The measurement data on the Kamchatka Canyon, including the block diagram, a set of echograms, the longitudinal profile of the canyon, and the bathymetric map, and the continuous seismoacoustic profiling data (CSP) has been reinterpreted. The study covers the shelf and the upper and middle parts of the continental slope. Regional gas-saturated strata have been discovered in the Cenozoic cover of the shelf and the continental slope, as well as in the block landslides of the sedimentary cover on the left (~55 km long, the western slope of the Kamchatka Cape) and right (more than 25 km long, the Kamchatka river delta front) sides of the canyon. Hanging landslides on the left side are associated with a 100–150 m increase in the depth of the canyon. On the middle slope, there is a large (28 km long) block landslide and its almost compensated paleochannel. The sub-latitudinal turn and the displacement of the canyon mouth to the north by 70 km is related to uplifting of the ridge-barrier in the Middle Pleistocene – Holocene. Based on the measurement and CSP data, it becomes possible to contour landslides on the sides of the Kamchatka Canyon, select the most hazardous locations (hanging landslides on the upper slope) for numerical modeling of potential landslide-related tsunami, and develop recommendations pertaining to construction of a new international sea port in the town of Ust-Kamchatsk.

Drowning of the coast was initiated by a marine inundation after the Last Glacial Maximum (marine isotope stage (MIS) 2) and has continued during the mid-Holocene and highstand (MIS 1). Detailed analyses of two previously examined core stratigraphy and seismic profiles combined with new grain-size and detailed diatom analyses are used to study the history of the Barra Falsa paleochannel over the last 11,000 years BP and to document the peculiar deposition within the channel fill. A rapid sea-level rise was responsible for flooding the coast in 11,180–10,780, 8420–7930, 8150–7870, and 7640–7430 cal years BP, infilling a low topographic back-barrier region. High deposition rates suggest a rapid filling of the channel, which coincides with an accelerated period of sea-level rise, closely linked to the global 8.2-ka event. The morphology of the channel is recognized by facies units in the underlying strata related to one episode of cut and fill during a single cycle of base-level fall and rise. An overall transgressive sequence above the regional surface is related to marine and marine-brackish sediments, which corresponds to a seaward/central basil fill of a wave-dominated estuary.

Changes in Martian fluvial geomorphology with time-stratigraphic age, including decreases in paleochannel widths, suggest waning paleodischarges through time. Where fluvial landforms do not preserve paleochannel widths (e.g., meander deposits), other landform dimensions (i.e., radius of curvature) may be used to estimate paleodischarges. In the Aeolis Dorsa region, topographically inverted and stacked fluvial deposits – wide meander point bars overlain by thin channel fills – preserve ostensible evidence of decreasing paleodischarges through time. However, a robust paleohydraulic analysis of these distinct deposits requires knowledge of the accuracy of a terrestrial-based empirical relationship that estimates channel width from point-bar radius of curvature. We assess the accuracy of this radius-width relationship by applying it to a well-studied terrestrial analog, the Quinn River, Nevada. We find that radii of curvature from the Quinn River exceed the values predicted from the empirical relationship. These anomalously high radii are associated with greater resistance in the channel cut banks, indicating that bank strength is a confounding factor in the radius-width relationship. Some deposits in the Aeolis Dorsa include irregular meander morphologies, suggesting variably resistant channel banks and overestimates of both paleochannel widths and paleodischarges. Furthermore, the morphometry of the overlying thin channel fills suggests their widths have been eroded, such that their paleodischarges are underestimates. These overestimates and underestimates, when considered together, suggest little change in paleodischarge during the stratigraphic transition from meander deposits to channel fills. This work demonstrates the importance of terrestrial analog studies for revealing confounding factors in Martian fluvial systems and cautions against simplistic interpretations of Martian fluvial history. The discovered inaccuracies of paleodischarge estimates expose sources of uncertainty in the extant paleodischarge data that bias inferences toward waning hydrologic activity through time.