scholarly journals Uranium distribution as a proxy for basin-scale fluid flow in distributive fluvial systems

2016 ◽  
Vol 173 (4) ◽  
pp. 569-572 ◽  
Author(s):  
A. Owen ◽  
A. J. Hartley ◽  
G. S. Weissmann ◽  
G. J. Nichols
Keyword(s):  
Fluid Flow ◽  
Fluvial Systems ◽  
Basin Scale ◽  
Uranium Distribution

Sediment slugs: large-scale fluctuations in fluvial sediment transport rates and storage volumes

1995 ◽  
Vol 19 (4) ◽  
pp. 500-519 ◽  
Author(s):  
A.P. Nicholas ◽  
P.J. Ashworth ◽  
M.J. Kirkby ◽  
M.G. Macklin ◽  
T. Murray
Keyword(s):  
Sediment Transport ◽  
Sediment Supply ◽  
Fluvial Systems ◽  
Event Scale ◽  
Fluvial Sediment ◽  
Sediment Routing ◽  
Basin Scale ◽  
Wide Range ◽  
And Storage ◽  
Fluvial Sediment Transport

Variations in fluvial sediment transport rates and storage volumes have been described previously as sediment waves or pulses. These features have been identified over a wide range of temporal and spatial scales and have been categorized using existing bedform classifications. Here we describe the factors controlling the generation and propagation of what we term sediment slugs. These can be defined as bodies of clastic material associated with disequilibrium conditions in fluvial systems over time periods above the event scale. Slugs range in magnitude from unit bars (Smith, 1974) up to sedimentary features generated by basin-scale sediment supply disturbances (Trimble, 1981). At lower slug magnitudes, perturbations in sediment transport are generated by local riverbank and/or bed erosion. Larger-scale features result from the occurrence of rare high- magnitude geomorphic events, and the impacts on water and sediment production of tectonics, glaciation, climate change and anthropogenic influences. Simple sediment routing functions are presented which may be used to describe the propagation of sediment slugs in fluvial systems. Attention is drawn to components of the fluvial system where future research is urgently required to improve our quantitative understanding of drainage-basin sediment dynamics.

scholarly journals Efficacy of bedrock erosion by subglacial water flow

2015 ◽  
Vol 3 (3) ◽  
pp. 849-908 ◽  
Author(s):  
F. Beaud ◽  
G. E. Flowers ◽  
J. G. Venditti
Keyword(s):  
Water Flow ◽  
Water Pressure ◽  
Water Discharge ◽  
Sediment Supply ◽  
Fluvial Systems ◽  
Glacial Meltwater ◽  
Erosion Rates ◽  
Subglacial Environment ◽  
Basin Scale ◽  
Bedrock Erosion

Abstract. Bedrock erosion by sediment-bearing subglacial water remains little-studied, however the process is thought to contribute to bedrock erosion rates in glaciated landscapes and is implicated in the excavation of tunnel valleys and the incision of inner gorges. We adapt physics-based models of fluvial abrasion to the subglacial environment, assembling the first model designed to quantify bedrock erosion caused by transient subglacial water flow. The subglacial drainage model consists of a one-dimensional network of cavities dynamically coupled to one or several Röthlisberger channels (R-channels). The bedrock erosion model is based on the tools and cover effect, whereby particles entrained by the flow impact exposed bedrock. We explore the dependency of glacial meltwater erosion on the structure and magnitude of water input to the system, the ice geometry and the sediment supply. We find that erosion is not a function of water discharge alone, but also depends on channel size, water pressure and on sediment supply, as in fluvial systems. Modelled glacial meltwater erosion rates are one to two orders of magnitude lower than the expected rates of total glacial erosion required to produce the sediment supply rates we impose, suggesting that glacial meltwater erosion is negligible at the basin scale. Nevertheless, due to the extreme localization of glacial meltwater erosion (at the base of R-channels), this process can carve bedrock (Nye) channels. In fact, our simulations suggest that the incision of bedrock channels several centimetres deep and a few meters wide can occur in a single year. Modelled incision rates indicate that subglacial water flow can gradually carve a tunnel valley and enhance the relief or even initiate the carving of an inner gorge.

Paleohydraulic investigation of the Ebro Basin: Implications for Mars

2021 ◽  
Author(s):  
Heath Geil-Haggerty
Keyword(s):  
Water Discharge ◽  
Sedimentary Basins ◽  
Mass Conservation ◽  
Sediment Supply ◽  
Sediment Flux ◽  
River Channels ◽  
Ebro Basin ◽  
Fluvial Systems ◽  
Sediment Size ◽  
Basin Scale

<p>The stratigraphy preserved in Earth’s sedimentary basins offers a record of how landscapes have evolved with time.  This stratigraphy provides insights into the dynamic processes that shaped the surface of the earth.  Fluvial stratigraphy contains many elements that can be used to recreate past conditions in ancient river channels.  Paleohydraulic reconstruction uses measurements of fluvial stratigraphy to model the conditions in the system that created them.  This allows us to answer questions related to water discharge, sediment flux, and duration of fluvial activity.  These are key questions when investigated in the context of Mars.  Paleohydraulic models can be used as compelling analogs for similar systems on Earth as well as Mars and other rocky planets.           </p><p>This study examines what the record of Oligocene-Miocene fluvial stratigraphy in northeastern Spain’s Ebro Basin can tell us about water discharge and sediment flux across distributive fluvial systems at a basin scale.  The Cenozoic stratigraphy of northeastern Spain’s triangular shaped Ebro Basin embodies a classic example of the formation of a closed sedimentary basin.  The Ebro Basin contains a number of remarkably well exposed fluvial sedimentary deposits.  These deposits outcrop as distinctive laterally contiguous channel sand bodies.  Clastic sediment supply in the Ebro Basin is largely governed by tectonic uplift and basin subsidence related to the Pyrenean orogen with peripheral contributions from the Catalan Coast and Iberian Ranges.  We test the idea that the record of conditions in the fluvial systems should reflect the record of lacustrine chemical sediments through sediment mass conservation.  In order to test this hypothesis measurements of bedform height, barform height, sediment size, and paleochannel dimensions were collected in the field.  Our paleohydraulic model uses previously derived theoretical and empirical relationships to recreate the conditions in these ancient fluvial systems.  These results are scaled up by accounting for drainage density and intermittency in order to address the principal question at a basin scale.  Paleodischarges from the fluvial sediments are comparable to those from river chemistry calculations for the lacustrine facies. </p>

3D basin-scale groundwater flow modeling as a tool for geothermal prospection of the Geneva Basin, Switzerland-France

2020 ◽  
Author(s):  
Marion Alcanie ◽  
Marine Collignon ◽  
Olav Møyner ◽  
Matteo Lupi
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Pure Water ◽  
Flow In Porous Media ◽  
Gravity Inversion ◽  
Tectonic Structures ◽  
Large Dataset ◽  
Heterogeneous Model ◽  
Flux Approximation ◽  
Basin Scale

<p>Switzerland supports the energetic transition by promoting the development of geothermal energy among other renewable energies. In particular, the Canton of Geneva is actively prospecting the Geneva Basin, generating a large dataset of geophysical and geological information. This large dataset of the Geneva Basin is used here to constrain geologically complex numerical models of fluid flow. Previous and ongoing projects demonstrated the geothermal potential of the Geneva Basin but a consistent basin-scale fluid flow model of the area has yet to be defined.</p><p>We use MRST (Matlab Reservoir Simulation Toolbox) for which we recently developed a geothermal module. The module is available with the last MRST release (2019b) and it is used to build up a 3D basin-scale dynamic model of the Geneva Basin. The goal of our numerical study is to investigate the large-scale control of tectonic structures and lithological hetherogeneities on fluid flow in the basin.</p><p>The static model is derived from active seismic and gravity inversion data. Petrophysical data and geo-location of faults are obtained from the existing literature. The resulting heterogeneous model takes into account the main geological facies, observed in the basin. We define a reference simulation with standard initial conditions (geothermal gradient and hydrostatic pressure topographically corrected) and a basal incoming heat flux. We consider a single-phase pure water compressible laminar flow in porous media. The geothermal module solves the mass and energy conservation equations using a fully implicit finite-volume discretisation with two-point flux approximation and single-point upstream mobility weighting.</p><p>We design a parametric study along three main axis: tectonic structures (i.e. faults), petrophysical and thermal properties and perform twenty three simulations running for 500 000 years to reach an equilibrium flow (steady-state). Our results show that fluid flow is driven by the hydraulic head of the topographic highs bounding the basin. Hotter fluids are found in the centre of the basin where we propose to focus geothermal exploitation in the future. Our results represent, to our knowledge, the first example of 3D basin-scale fluid flow modelling used as a preliminary prospection method for the assessment of geothermal resources.</p>

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