Evolution Of Fluvial Systems Research Articles

Interaction between the controls on fluvial system development: tectonics, climate, base level and river capture – Rio Alias, Southeast Spain

ABSTRACTFluvial systems in uplifting terrain respond to tectonic, climatic, eustatic and local base‐level controls modified by specific local factors, such as river capture. The Rio Alias in southeast Spain is an ephemeral, transverse‐to‐structure fluvial system. The river drains two interconnected Neogene sedimentary basins, the Sorbas and Almeria basins, and crosses two major geological structures, the Sierras de Alhamilla/Cabrera and the Carboneras Fault Zone. Regional epeirogenic uplift resulted in sustained fluvial incision during the Quaternary, punctuated by major climatically driven periods of aggradation and dissection, which created a suite of five river terraces. The river terrace sequence was radically modified in the late Pleistocene by a major river capture (itself a response to regional tectonics), localized tectonic activity and eustatic base‐level change. The Rio Alias is defined by four reaches; within each the climatically‐generated, region‐wide, fluvial response was modified by tectonics, base‐level change or river capture to varying degrees. In the upper part of the basin (Lucainena reach), climate was the dominant control on river development, with limited modification of the sequence by uplift of the Sierra Alhamilla and local drainage reorganization by a local river capture. Downstream of the Sierra Alhamilla in the Polopus reach, the climatic signal is dominant, but its expression is radically modified by the response to a major river capture whereby the Alias system lost up to 70% of its pre‐capture drainage area. In the reach adjacent to the Carboneras Fault Zone (Argamason reach), modification of the terrace sequence by local tectonic activity and a resultant local base‐level fall led to a major local incisional event (propagating c. 3–4 km upstream from the area of tectonic disturbance). At the seaward end of the system (El Saltador reach) Quaternary sea‐level changes modified the patterns of erosion and incision and have resulted in steep incisional terrace profiles. The signals generated by regional tectonics and the Quaternary climate change can be identified throughout the basin but those generated by ongoing local tectonics, river capture and sea‐level change are spatially restricted and define the four reaches. The connectivity of the system from the headwaters to the coast decreased through time as incision progressed, resulting in changes in local coupling characteristics. Copyright © 2012 John Wiley & Sons, Ltd.

Managing clastic reservoir heterogeneity I: Sedimentology and sequence stratigraphy of the Late Triassic Minjur Sandstone at the Khashm al Khalta type locality, Central Saudi Arabia

ABSTRACT The Late Triassic (Norian–Rhaetian) Minjur Sandstone provides a remarkable case study for understanding and modelling the spatial distribution of sand bodies in a fluvial-deltaic system. As such it has been studied in connection with the geological storage of CO2 in complex heterogeneous formations. Detailed sedimentological mapping of the formation’s vertical and lateral variations in and around the type section at Khashm al Khalta (Khashm al Minjur), which is the area of interpreted maximum inlet/outlet activity, has provided a relatively detailed picture of the sequence stratigraphy. As originally described, shallow-marine flooding with the development of tidal mud flats and carbonate facies occurred near the middle of the formation, splitting it into a lower member dominated by subtidal, brackish and scattered fluvial environments, and an upper member marked by the appearance of meandering point bars capped upward by very proximal deposits forming thick (20 m) coarse-grained sandstone bars that can be followed over several kilometers. The general trend at formation scale is thus upward thickening and coarsening sedimentation related to an increasing clastic influx and the development of fluvial systems, with the fluvial upper member being dominated by amalgamated sand bars. The sequence stratigraphy indicates nine depositional sequences involving four depositional environments: sabkha, tidal, estuarine and fluvial-continental. The lower Minjur is a transgressive tract of four sequences of which Sequence 4 reflects maximum flooding and correlates with maximum flooding surface (MFS) Middle Norian Tr80. Sequence 5 corresponds to a meander system at the base of the upper Minjur, and is followed by sequences 6 to 9 reflecting an increasing clastic influx generating amalgamated coarse-grained bars. The upper Minjur thus represents a highstand systems tract.

A influência da geodiversidade da região da Serra do Cabral (norte de MG) na variabilidade morfossedimentar do Córrego da Gameleira

In order to find sediment storage zones into Jequitai hydrographic basin, 3D SRTM slope models were analyzed. These provided the identification of an anomalous drainage site located at Jequitai basin`s eastern portion between Espinhaco and Cabral ranges. Some contrasts of sedimentation pattern and valley cross-section along a short segment of Gameleira stream are good examples of these anomalies. Regional litho-structural analysis, including Cenozoic deformations, suggests that local variations of the Paraopeba Subgroup components is the main responsible for the observed fluvial system evolution. In addition, the northward tilting of Jequitai basin`s southern portion, in the Jequitai graben direction, increase the anomalous litho-structural effects. Log profiles suggest that alluvial fans coming probably from Espinhaco range covered the research sites. This work shows that some non-erosive fluvial segments are mistakenly explained as agradational when the investigation is supported only by geomorphological data obtained by remote sensing techniques. The studied segment presents morpho-sedimentary attributes that reflect the local geodiversity framework.

A influência da geodiversidade da região da Serra do Cabral (norte de MG) na variabilidade morfossedimentar do Córrego da Gameleira

In order to find sediment storage zones into Jequitai hydrographic basin, 3D SRTM slope models were analyzed. These provided the identification of an anomalous drainage site located at Jequitai basin`s eastern portion between Espinhaco and Cabral ranges. Some contrasts of sedimentation pattern and valley cross-section along a short segment of Gameleira stream are good examples of these anomalies. Regional litho-structural analysis, including Cenozoic deformations, suggests that local variations of the Paraopeba Subgroup components is the main responsible for the observed fluvial system evolution. In addition, the northward tilting of Jequitai basin`s southern portion, in the Jequitai graben direction, increase the anomalous litho-structural effects. Log profiles suggest that alluvial fans coming probably from Espinhaco range covered the research sites. This work shows that some non-erosive fluvial segments are mistakenly explained as agradational when the investigation is supported only by geomorphological data obtained by remote sensing techniques. The studied segment presents morpho-sedimentary attributes that reflect the local geodiversity framework.

Paleovalley morphology and fluvial system evolution of Eocene-Oligocene sediments ("auriferous gravels"), northern Sierra Nevada, California: Implications for climate, tectonics, and topography

Research Article| September 01, 2011 Paleovalley morphology and fluvial system evolution of Eocene–Oligocene sediments (“auriferous gravels”), northern Sierra Nevada, California: Implications for climate, tectonics, and topography Elizabeth J. Cassel; Elizabeth J. Cassel † 1Department of Earth and Environment, Franklin and Marshall College, Lancaster, Pennsylvania 17604, USA †E-mail: ejcassel@gmail.com Search for other works by this author on: GSW Google Scholar Stephan A. Graham Stephan A. Graham 2Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Elizabeth J. Cassel † 1Department of Earth and Environment, Franklin and Marshall College, Lancaster, Pennsylvania 17604, USA Stephan A. Graham 2Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA †E-mail: ejcassel@gmail.com Publisher: Geological Society of America Received: 21 Jun 2010 Revision Received: 03 Oct 2010 Accepted: 09 Nov 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (9-10): 1699–1719. https://doi.org/10.1130/B30356.1 Article history Received: 21 Jun 2010 Revision Received: 03 Oct 2010 Accepted: 09 Nov 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Elizabeth J. Cassel, Stephan A. Graham; Paleovalley morphology and fluvial system evolution of Eocene–Oligocene sediments (“auriferous gravels”), northern Sierra Nevada, California: Implications for climate, tectonics, and topography. GSA Bulletin 2011;; 123 (9-10): 1699–1719. doi: https://doi.org/10.1130/B30356.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract In the northern Sierra Nevada, California, Eocene–Oligocene fluvial sediments (the “auriferous gravels”) rest unconformably in well-defined basement-incised paleovalleys, providing a record of paleolandscape geomorphology and drainage system evolution. Paleovalley surface mapping shows that local topography and bedrock lithology controlled the location of broad, terraced paleovalley segments, which formed in the central and eastern metamorphic bedrock belts and subsequently became areas of significant fluvial deposition. High-gradient, high-energy deposits are present near the edges of these areas, suggesting that tributaries and outlets resided in steeper, narrow paleovalleys. Multiple strath terraces are common in broad paleovalleys, indicating that incision events occurred both before deposition and during paleovalley widening, followed by periods of aggradation. Broad paleovalley deposits contain predominantly braided stream facies deposited in an energetically variable system. Multiple upward-fining cycles, bounded by erosional surfaces, are composed of alternating coarse-grained channel-belt and fine-grained floodplain packages. An overall upward-fining succession suggests that the locus of fluvial deposition shifted and depositional energy waned over time as the system backfilled successive broad paleovalleys.Paleochannel slope estimates of 0.004–0.055 were obtained based on average grain sizes of coarse channel fills. Anomalously thick (up to 11 m), laterally continuous (1–3 km) floodplain units, containing kaolinite-rich clay and Oxisol intervals, record high fine-grained sediment supply, driven by high rates of chemical weathering in the warm Eocene climate. Based on sedimentary characteristics, combined with floral and detrital zircon data, braided stream deposition within the basin occurred from the late early Eocene through late Eocene, and aggradation primarily occurred in broad, lower-gradient reaches behind a major bedrock knickpoint, created in the late Mesozoic–early Cenozoic, possibly due to asymmetric batholith unroofing. The diachronous, localized nature of paleovalley incision and braided stream aggradation within the northern Sierra Nevada invalidates previous estimates of the timing and amount of range uplift based on paleochannel reconstructions and gradients. Both internal and external drivers influenced the evolution of the fluvial system through (1) the pattern of basin filling, as the locus of deposition migrated east to west, (2) the warm Eocene climate, which increased chemical weathering and contributed a high sediment supply, and (3) changes in base level due to eustasy and/or Laramide tectonism. This record of Laramide tectonics in the Sierra Nevada and Basin and Range is important for the timing of Sierra Nevada uplift, for tectonic reconstructions of western North America, and for studies of landscape evolution in tectonically active orogens. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The construction of a palaeodischarge time series for use in a study of fluvial system development of the Middle to Late Pleistocene Upper Thames

AbstractRecently many studies have attempted to model fluvial system development over a variety of geographical and temporal scales. It is generally recognised that one of the main problems, especially in studies over longer timescales (>100 ka), is the reconstruction of a robust palaeodischarge time series. Over such extended timescales discharge can only be reconstructed using proxy data, i.e. either field‐based (sediment) palaeodischarge estimates or transformation of reconstructed palaeoclimate data series (e.g. ice core data), with only the latter method allowing the reconstruction of a continuous time series. In this study of the Upper Thames catchment, UK, we have developed a new palaeodischarge time series. A sea surface temperature record (ODP 980) from the North Atlantic (off the west coast of Ireland) is used as a proxy for precipitation across the Upper Thames catchment. A vegetation filter, based on pollen data, is then applied to this precipitation record in order to create a runoff model. Finally, this runoff model is transformed to a discharge model via the use of a climate change function which attempts to reflect probable changes in the frequency and magnitude of discharge events. Using our new palaeodischarge model, we present output from the FLUVER2 model of longitudinal profile development for the Middle to Late Pleistocene Upper Thames Valley. This model simulates the possible timing and magnitude of sediment aggradation/degradation events on the floodplain as well as the timing of floodplain abandonment due to tectonic uplift, resulting in terrace formation. Copyright © 2010 John Wiley & Sons, Ltd.

Cambrian intra-oceanic arc accretion to the austral Gondwana margin: constraints on the location of proto-New Zealand

Data from New Zealand and northern Victoria Land, Antarctica, indicate that the Cambrian Takaka Terrane intra-oceanic arc/backarc assemblage and the Bowers Terrane intra-oceanic arc/back-arc assemblage were accreted to the Gondwana margin by the Late Cambrian. Compelling similarities between the arc rocks and the immediate post-arc sediments firmly place the two regions in the same tectonic framework and imply close paleogeographic proximity. Currently, the Ross Orogen is thought to be the result of sinistral oblique convergence with west-directed subduction, and accretion of the arc assemblages is attributed to closure of backarc basins. Syntectonic fluvial conglomerates in both regions attest to the development of fluvial systems draining both the accreted arc and the contemporaneous continental margin arc. Trilobite faunas indicate that fluvial sedimentation commenced earlier in New Zealand than in northern Victoria Land. In the context of the widely accepted sinistral oblique convergence model, these data suggest an original position for New Zealand to the south of northern Victoria Land, probably in the region of the southern Ross Sea.

ESR chronology of alluvial deposits and first human settlements of the Middle Loire Basin (Region Centre, France)

Since 1970, many prehistoric sites have been discovered in the alluvial terraces of several rivers of the Middle Loire River basin (France). During the last decade, the stepped-terraces systems of three of the Loire tributaries, the Creuse, the Cher and the Loir Rivers, were the focus of multidisciplinary studies, involving Quaternary geology, prehistory and geochronology. The geochronological data now available for these systems were mainly obtained by electron spin resonance (ESR) method applied to optically bleached fluvial quartz. These results provide a chronological framework for the evolution of fluvial systems and the human settlements of this area during Lower and Middle Pleistocene. Two phases of human settlement could be distinguished, around 1.1 Ma (Early Palaeolithic – Mode 1) and around 0.7 Ma ago (Acheulean – Mode II).

Active crustal deformation beyond the SE margin of the Tibetan Plateau: Constraints from the evolution of fluvial systems

An integrated explanation is proposed for the Late Cenozoic crustal deformation in Yunnan, SW China, using sedimentary and geomorphological evidence from the Yangtze and Red River systems. The observed fluvial incision indicates up to ~ 15 km of crustal thickening, associated with ~ 3 km of uplift, apparently triggered at ~ 8 Ma by monsoon-induced erosion drawing mobile lower crust from beneath Tibet to the northwest. The mobile lower-crustal layer beneath Yunnan was initially very thin, but a positive feedback loop developed, whereby each incremental influx of lower-crust widened and heated this layer, facilitating the next increment. At ~ 5 Ma, the shear tractions exerted on the brittle upper-crust by this flowing lower crust became sufficient to reactivate pre-existing lines of weakness, dragging blocks of the brittle layer southward and creating the region′s modern active fault systems. This region thus provides a dramatic example of crustal deformation induced by Late Cenozoic climate change, notwithstanding its location adjoining the India–Eurasia plate boundary.

Estuarine–fluvial floodplain formation in the Holocene Lower Tagus valley (Central Portugal) and implications for Quaternary fluvial system evolution

We present a brief synthesis of the Quaternary fluvial record in the Lower Tagus Basin (central Portugal), concentrating on factors controlling infill and incision. The Holocene part of the record forms the focus of this paper and guides the questioning of the basic assumptions of the established Quaternary fluvial evolution model, in particular the link between sea-level change and fluvial incision-deposition. We suggest that several incision-aggradation phases may have occurred during glacial periods. Major aggradation events may overlap with cold episodes, while incision appears to concentrate on the warming limb of climate transitions. The complex stratigraphy of the Quaternary record in the Lower Tagus valley is influenced by repeated base-level and climate changes.This paper submits the first chronostratigraphic framework for valley fill deposits in the Lower Tagus area. Sea-level rise forced aggradation and controlled deposition of the fine-grained sedimentary wedge underlying the low-gradient Lower Tagus floodplain. Investigations have focused on the lower Muge tributary, where rapidly aggrading estuarine and fluvial environments were abruptly established (∼8150calBP) as sea level rose. Base level at the valley mouth controlled the upstream extent of the fine-grained backfill. Tidal environments disappeared abruptly (∼5800calBP) when the open estuary at the Muge confluence was infilled by the Tagus River. The decrease and final still stand of sea-level rise led to floodplain stabilisation with peat (∼6400–5200calBP) and soil formation (∼5200–2200calBP). Localised renewed sedimentation (∼2200–200calBP) is linked to human activity.

Fluvial system evolution and environmental changes during the Holocene in the Mue valley (Western France)

Geomorphological and palaeoenvironmental research on Holocene sedimentation in the Mue valley provides evidence for fluvial system changes related to climate and human activities in Normandy, a poorly studied area of the Paris basin. The 24-km long valley bottom has been investigated through a systematic survey. It shows an original longitudinal sedimentary pattern in relation with valley morphology and local geological controls. Minerogenic, tufaceous and peaty deposits provide opportunities for multi-proxy analyses and radiocarbon dating control. Sedimentation began around 9500 14C BP with silt deposition in a meandering system. The Boreal and the Lower Atlantic periods (8500–6000 14C BP) were mainly characterized by unlithified calcareous tufa. Locally, these deposits are very thick (7 to 13 m). The tufa formed barrages across the valley bottom, providing an autogenic control on upstream sedimentation. During the Upper Atlantic period (6000–4700 14C BP), the valley experienced a decrease in calcareous sedimentation and the development of organic deposits. At the beginning of the Subboreal (4700–3500 14C BP), peat deposits expanded, especially behind the tufa barrages. The valley bottom was characterized by large marshy areas whereas the regional vegetation was progressively modified by human activities. At the end of the Subboreal (3300–3000 14C BP) the infilling of the valley by calcareous silt was caused by an increase of river activity related to climatic and land use changes. From the Iron Age and Gallo-Roman periods (2800–1700 14C BP), the valley bottom was filled by silty overbank deposits related to an increase of soil erosion. The slopes and river system were once again coupled and the fluvial system functioned as a continuum from upstream to downstream. The alluvial record of the Mue valley reflects a broad regional pattern of environmental changes but presents particular features, which highlight the need of longitudinal studies to take into account spatial and temporal discontinuities of Holocene hydro-sedimentary systems, even in small order valleys.

Lower Triassic sequence stratigraphy of the western part of the Germanic Basin (west of Black Forest): Fluvial system evolution through time and space

The aim of this paper is to analyse the fluvial evolution of the Lower Triassic in the western part of the Germanic Basin through time and space, as well as the impact of the geodynamic and climatic setting on the preservation of fluvial deposits. The Lower Triassic crops out only in the Vosges Massif and the Black Forest, so well-log studies are required to realise sequence stratigraphy correlations and establish comparisons with others parts of the Germanic Basin. In a first step, we use well-log data analyses to characterise the electrofacies associations in the Triassic and then define the well-log signatures of each formation. In a second step, the characterisation and recognition of genetic sequences and their stacking pattern allow us to define seven minor cycles integrated into two major cycles. Finally, the quantification of the lithologies at different stages of basin evolution leads to the reconstruction of paleoenvironmental maps to illustrate facies evolution through space and time. A comparison with cycles defined in the Germanic Basin allows us to propose correlations of the Lower Triassic on either side of the Rhine Graben and leads to a discussion of the evolution of fluvial systems through time and space. During the Scythian, the fluvial style is characterised by braided fluvial systems evolving laterally into lake deposits towards the central part of the Germanic Basin. During this stage, the basin was a huge depression with very few marine connections in its extreme eastern part. The stratigraphic cycles represent rhythmic fluctuations in relative lake level that could be attributed to sediment supply and/or lake level variations in an arid setting. Four minor stratigraphic cycles are observed that are integrated within a single major stratigraphic cycle. During the period of the stratigraphic base-level rise of the major cycle, a maximum of 233 m of sediment would represent a duration of sedimentation in the Paris Basin of at least 1.8 m.y. During the period of the stratigraphic base-level fall of the major cycle, a maximum of 65 m of sediment would have accumulated over 2.5 m.y. On the western edge of the Germanic Basin, the top of the Scythian is marked by a major sedimentary break characterised by a planation surface, with preservation of the first paleosols, followed by the Hardegsen unconformity. This unconformity is tectonically deformed, leading to the development of a new sedimentation area in the west of the basin. The fluvial sedimentation above this discontinuity shows a trend towards enhanced development of floodplain or lacustrine-type environments at its western margin, with the formation of paleosols. The fluvial systems are linked with sabkhas, and then with a shallow sea connected to the Tethys Ocean. In this context, the stratigraphic cycles are caused by variations in relative sea level and/or sediment supply. The fluvial deposits are preserved in an exoreic basin.

Review of Rivers and Floodplains, by M. John S. BridgeRivers and FloodplainsBlackwell Publishing0632064897US$ 84.95

The author states that this book is concerned with the origin, geometry, water flow, sediment transport, erosion, and deposition associated with modern alluvial rivers and floodplains, how they vary in time and space, and how this information is used to interpret deposits of ancient rivers and floodplains. There is specific reference to the types and lifestyles of organisms associated with fluvial environments, human interaction with rivers and floodplains, associated environmental and engineering concerns, as well as the economic aspects of fluvial deposits, particularly the modeling of fluvial hydrocarbon reservoirs and aquifers. Methods of studying rivers and floodplains and their deposits are also discussed. Although basic principles are emphasized, many examples are detailed. Rivers and Floodplains is designed as a core text for senior undergraduate and graduate students studying modern or ancient fluvial environments, particularly in earth sciences, environmental sciences, and physical geography, but also in civil and agricultural engineering; college professors, researchers, and practicing professionals will also find the book an invaluable reference. John Bridge is a professor of Geological Sciences at the State University of New York at Binghamton, where he teaches and undertakes research in earth surface processes and sedimentology. This substantial monograph has been subdivided into ten chapters. The first chapter presents an overview of fluvial systems; the second and third chapters are on fundamentals of water flow and sediment transport respectively; Chapter 4 deals with bed forms and sedimentary structures; Chapter 5 focuses on alluvial channels and bars; Chapter 6 focuses on floodplains; Chapter 7 details along-valley variations in channels and floodplains; Chapter 8 is on channel-belt movements across floodplains; Chapter 9 is on long-term large-scale evolution of fluvial systems; and chapter 10 deals with fossils in fluvial deposits. In general, the material is very well presented, extremely well illustrated and very well suited to the intended audience. What this text does so well is a comprehensive integration of geomor-

Pleistocene geochronologies for fluvial sedimentary sequences: an archaeologist's perspective

AbstractCurrent models of Pleistocene fluvial system development and dynamics are assessed from the perspective of European Lower and Middle Palaeolithic stone tool assemblages recovered from fluvial secondary contexts. Fluvial activity is reviewed both in terms of Milankovitch‐scale processes across the glacial/interglacial cycles of the Middle and Late Pleistocene, and in response to sub‐Milankovitch scale, high‐frequency, low‐magnitude climatic oscillations. The chronological magnitude of individual phases of fluvial activity is explored in terms of radiocarbon‐dated sequences from the Late Glacial and early Holocene periods.It is apparent that fluvial activity is associated with periods of climatic transition, both high and low magnitude, although system response is far more universal in the case of the high magnitude glacial/interglacial transitions. Current geochronological tools do not permit the development of high‐resolution sequences for Middle Pleistocene sediments, while localised erosion and variable system responses do not facilitate direct comparison with the ice core records. However, Late Glacial and early Holocene sequences indicate that individual fluvial activity phases are relatively brief in duration (e.g. 102 and 103 yr). From an archaeological perspective, secondary context assemblages can only be interpreted in terms of a floating geochronology, although the data also permit a reinvestigation of the problems of artefact reworking. Copyright © 2005 John Wiley & Sons, Ltd.

Weathering, geomorphic work, and karst landscape evolution in the Cave City groundwater basin, Mammoth Cave, Kentucky

Following the pioneering work of Wolman and Miller [Wolman, M.G., Miller, J.P., 1960. Magnitude and frequency of forces in geomorphic processes. J. Geol., 68, 54–74.] in evaluation of geomorphic work and the frequencies and magnitudes of forces that drive it, a large number of quantitative studies have focused on the evolution of fluvial systems and transport of clastic sediment. Less attention has been given to understanding frequencies and magnitudes of processes in rock weathering, including investigation of rates at which solutes are removed from landscapes under various flow distributions as an analog to Wolman and Miller's [Wolman, M.G., Miller, J.P., 1960. Magnitude and frequency of forces in geomorphic processes. J. Geol., 68, 54–74.] concept of geomorphic work.In this work, we use 1 year of high-resolution flow and chemical data to examine the work done in landscape evolution within and at the outlet of Kentucky's Cave City Basin, a well-developed karst landscape/aquifer system that drains about 25 km2. We consider both removal of solutes contributing to landscape denudation based on calcium mass flux as well as predicted dissolution rates of the conduit walls at the outlet of this basin based on limestone dissolution kinetics.Intense, short-duration events dominate. Storms that filled the Logsdon River conduit occurred <5% of the year but were responsible for 38% of the dissolved load leaving the system and from 63% to 100% of conduit growth for various scenarios of sediment influence. Landscape denudation is a linear function of the amount of water moving through the system, but conduit growth rates, and thus rates of recharge area evolution from fluvial to karst surface landscapes, depend both on the amount of water available and the distribution of precipitation.

Evolution of fluvial system in Siwalik Group of Chatara-Barahakshetra area, east Nepal Himalaya

Four facies associations (i.e., FA1 to FA4) are recognised in the Siwalik molasse of the Chatara-Barahakshetra area in east Nepal. They are classified based on the proportion of sandstone and mudstone, individual bed thickness, and bedform types. The facies associations are intimately related to the lithostratigraphic units of the Siwalik Group. The lower and upper members of the Lower Siwaliks (FA1- and FA2-facies associations, respectively) are inferred to be the products of fine-grained meandering and flood flow-dominated meandering fluvial systems, respectively. Similarly, the lower and middle members or the Middle Siwaliks (FA3- and FA4-facies associations, respectively) are interpreted as the deposits of sandy meandering and sandy braided fluvial systems, respectively.

Evolution of the fluvial system of the Prypiat, Desna and Dnieper during the Late Middle - Late Pleistocene [ Evolution des systèmes fluviatiles des rivières Prypiat, Desna et Dniepr au cours du Pléistocène moyen récent et du Pléistocène supérieur.

A hypothesis that envisages Late Pleistocene braided rivers with enlarged meanders, unlike the present rivers of the European plains, anses from a tentative model for the development of the Prypiat-Dnieper-Desna alluvial plain in the late Middle - Late Pleistocene. This plain (local relief - 30-60 m) consists of a staircase of six river terraces and corresponding alluvial suites that have been forming since the Dnieper (Saale) Glaciation. Each terrace occupies a definite altitudinal step in this staircase and has a unique position within the plain as well as characteristic relief features related to terrace boundary shapes, longitudinal and cross profiles, primary fluvial and superimposed aeohan, cryogenic and erosional landforms. The alluvial suites have a cut-and-fill framework and noticeable differences in faciès composition expressed by sedimentary structures and other hthological features. Data inferred from the relief and from geological structures indicate complex fluvial system development with six main stages of varying duration and significance. These comprised one accumulative phase and five erosion-accumulation cycles, associated with weak pulsating tectonic uplift, expressed as 7-20 m of incision. The direct influence of the decay of the Dnieper ice sheet, alternations of glacial -interglacial runoff and stream load, significant fluctuations of precipitation, displacement of vegetation zones as well as permafrost thaw, all caused changes in the fluvial erosion-sedimentation regime. Glacially-fed suspended load streams, sandy meandering and braided streams, as well as sandy bedload braided and low sinuosity streams succeeded each other following the Dnieper Glaciation. These changes were accompanied by remarkable transformations of the river network general westward displacement, downstream displacement during the latest stages, abandonment of tributaries and inner fan formation. Proof of the existence of discontinuous permafrost or deep seasonal frost penetration has been obtained for the first time in the Late Pleistocene fluvial deposits of the area. Relying on the evidence of cryogenic and aeohan activity, the final phases of accumulation of the 1st Terrace Suite presumably correlate with the maximum of the Last Glaciation and the formation of the Peripheral Terrace Suite with permafrost degradation at the end of the Late Pleistocene.

Rivers and floodplains: forms, processes, and sedimentary record

1. Introduction. 2. Overview of River Systems. 3. Fundamentals of Water Flow. 4. Fundamentals of Sediment Transport. 5. Bed forms and Sedimentary Structures. 6. Alluvial Channels and Bars. 7. Floodplains. 8. Along--valley Variations in Channels and Floodplains. 9. Channel--belt movements across floodplains. 10. Long--term, Large--scale Evolution of Fluvial Systems. 11. Fossils in Fluvial Deposits. Appendix 1. Methods of Measuring Bed Topography, Water flow, Sediment Transport, Erosion and Deposition in Rivers. Appendix 2. Methods of Describing and Interpreting Sedimentary Strata. References

Climate forcing of fluvial system development: an evolution of ideas

Starting from traditional ideas on the climatic steering of fluvial system dynamics, it appears that there are different kinds of climatic influences on system dynamics. They vary from direct climatic forcing (like peak precipitation) to indirect (like permafrost) and partial forcing (like vegetation). Vegetation (or its absence), and not directly climate, is considered as the main cause of fluvial incision (or deposition) during temperate (or cold) periods. However, other external factors than climate and non-climatic factors, such as local basin characteristics (like subsoil lithology and relief), express their effects on the fluvial systems by their role in the energy balance of the river catchment. Finally, internal factors in fluvial system evolution (like thresholds and response time) should not be neglected.

Geomorphological and sedimentological features in Quaternary fluvial systems affected by solution-induced subsidence (Ebro Basin, NE-Spain)

The Quaternary evolution and the morpho-sedimentary features of some of the most important rivers in Spain (Ebro and Tagus rivers among others) have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock. The subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending. In the Ebro Basin, the mechanisms and processes involved in karstic subsidence were studied through the analysis of present-day closed depressions as well as through old subsidence depressions (palaeocollapses and solution-induced basins) and associated deformations recorded in the Quaternary alluvial sediments. The Gállego–Ebro river system is presented as a case study of channel adjustments and geomorphic and sedimentary evolution of fluvial systems in dissolution-induced subsidence areas. In this fluvial system, evaporite dissolution during particular Quaternary time intervals (namely early and middle Pleistocene) have lead to the development of a solution-induced basin, approximately 30 km-long by 8 km-wide, filled by Quaternary deposits with a total thickness in excess of 190 m. The main river response to balance the subsidence in the alluvial plain was aggradation in the central reach of the subsiding area, and degradation both in the upstream reach and in the valley sides where alluvial fans and covered pediments may prograde over the fluvial sediments. The main sinking areas are recognized in the sedimentary record by anomalous thickenings in the alluvial deposits and fine-grained sediments deposited in backswamp and ponded areas.