Ancient River Channels Research Articles

Degradation of the River Channel Righ by Sewage and Contamination of Groundwater Nearby: Decline of Palm in the East Northern Sahara of Algeria

About 150 km along the ancient river channel Righ evacuates water leaching to chott Melghir 50 oasis. Since the eighties, water surpluses caused by discharges of urban wastewater and drainage water, caused the rise of the water table, causing an imbalance in the valley until sterilization of agricultural soils surrounding palm. Our study has shown that the waters of the collecting duct are of very poor quality, very hard , very high salinity ( C5 class ) , electrical conductivity up to 26300 ms / cm, SAR > 28 (S4 class ), a value of TDS(Total Disolved Sodium) up to 20 g / l , levels of high COD (Chemical oxygen demand)and suspended solids TSS . So mostly canal water is of very poor quality, loaded with minerals, it is a brackish facies chlorinated sodium.

A guide to the bedrock geology of Range Creek Canyon, Book Cliffs, Utah

Range Creek Canyon, located within the Book Cliffs of eastern Utah, contains some of the most abundant and well-preserved archaeological sites in North America. Its cliffs and landscapes provide a canvas for rock art panels and a foundation for granaries, ruins, and artifacts of the prehistoric Fremont Indians. In order to place these Range Creek sites within a geologic context, an illustrated geologic field guide was created for the general public. The guide focuses on the major bedrock formations that crop out in the canyon, as well as many indicators that facilitate geologic interpretation of these rocks. Outcrops of the Paleogene Flagstaff and Colton Formations (~58 to 48 million years old) in Range Creek Canyon were investigated in order to interpret their depositional environments. The lacustrine Flagstaff Limestone contains limestone beds and fossils of freshwater gastropods, oysters, and turtles indicative of lake environments. The unit coarsens upward with an increase of interbedded sandstone, which was deposited in and near ancient river channels. This trend suggests dynamic levels of the ancient lake, with overall encroachment of river systems near the contact with the Colton Formation. The fluvial Colton Formation is characterized by discontinuous, stacked beds of sandstone, representing a succession of migrating river channels and floodplain deposits. The Colton Formation exhibits a general upward trend of increased grain size and increased channel belt (continuous sandstone beds) frequency and lateral extent, implying a transition to higher energy river systems through time. These dynamic, ancient rivers may have been flowing generally northward into Eocene Lake Uinta, recorded in deposits of the Green River Formation north of Range Creek Canyon.

A guide to the bedrock geology of Range Creek Canyon, Book Cliffs, Utah

Range Creek Canyon, located within the Book Cliffs of eastern Utah, contains some of the most abundant and well-preserved archaeological sites in North America. Its cliffs and landscapes provide a canvas for rock art panels and a foundation for granaries, ruins, and artifacts of the prehistoric Fremont Indians. In order to place these Range Creek sites within a geologic context, an illustrated geologic field guide was created for the general public. The guide focuses on the major bedrock formations that crop out in the canyon, as well as many indicators that facilitate geologic interpretation of these rocks. Outcrops of the Paleogene Flagstaff and Colton Formations (~58 to 48 million years old) in Range Creek Canyon were investigated in order to interpret their depositional environments. The lacustrine Flagstaff Limestone contains limestone beds and fossils of freshwater gastropods, oysters, and turtles indicative of lake environments. The unit coarsens upward with an increase of interbedded sandstone, which was deposited in and near ancient river channels. This trend suggests dynamic levels of the ancient lake, with overall encroachment of river systems near the contact with the Colton Formation. The fluvial Colton Formation is characterized by discontinuous, stacked beds of sandstone, representing a succession of migrating river channels and floodplain deposits. The Colton Formation exhibits a general upward trend of increased grain size and increased channel belt (continuous sandstone beds) frequency and lateral extent, implying a transition to higher energy river systems through time. These dynamic, ancient rivers may have been flowing generally northward into Eocene Lake Uinta, recorded in deposits of the Green River Formation north of Range Creek Canyon.

English

A total of thirty-two (32) vertical electrical sounding (VES) data were acquired using R 50 d.c. Resistivity meter within the Precambrian basement geology of part of Akure metropolis southwestern Nigeria.  The VES data were interpreted; eight type curves were identified, from the geoelectric section the subsurface was characterized into four lithologies namely topsoil, weathered layer (clay /lateritic clay), weathered / fractured basement and bedrock. Thus, two major aquifers were mapped these are weathered/partially weathered layer and weathered basement/fractured basement aquifers. These aquifers are characterized by thick overburden, found within basement depressions and exhibit moderate to relatively high values of coefficient of anisotropy, λ, (0.97-1.11) with depth. Also, ancient river channel trending approximately NE-SW was mapped. The assessment of the materials above the aquifers showed that longitudinal conductance (S), values ranged from 0.0035 to 0.17 mhos; thus the S values are generally low suggesting that the materials above the aquifers are loose and porous thus having less capacity to protect  aquifers in the study area. Thus the aquifers  are poorly protected, and by implication vulnerable to infiltration.   Key words: Basement aquifer, Dar-Zarrouk parameters, Protective capacity Aquifer Risk.

Metodología para la definición de unidades hidroestratigráficas: caso del acuífero del valle del río Yaqui, Sonora, México

A method for defining hydrostratigraphic units is herein proposed, and various definitions of hydrostratigraphic units previously proposed are analyzed. Nevertheless, none of the definitions are widely accepted; therefore, the hydrostratigraphic units proposed here are defined using the lithologic characteristics of the sediments along with the values of hydraulic conductivity. A methodology to define hydrostratigraphic units in granular aquifers is proposed. The case of the Yaqui River aquifer is analyzed here and the hydrostratigraphic units are defined based on the characteristics of the sediments filling the basin, which correspond to fluvial sedimentary environments. Five hydrostratigraphic units were identified in the aquifer. Also, with the interpretation of the hydrostratigraphy, it was possible to determine the kind sediments present at different depths, thereby recognizing the presence of the ancient river channel of the Yaqui River.

Imaging a shallow aquitard with seismic reflection data in Memphis, Tennessee, USA. Part II: data analysis, interpretation and traveltime tomography

ABSTRACTWe collected P‐wave seismic reflection data to image suspected breaches in the confining unit (aquitard) above the Memphis aquifer in Memphis, Tennessee, USA, where previous studies of water quality have suggested potential contamination. A 1‐km‐long reflection line was acquired across depressions of the water table that have been interpreted to reflect a breach in the aquitard. Although raw data are dominated by surface waves, after frequency filtering, shot static correction and filtering, consistent reflections can be observed. Integration of constant velocity analysis (CVS) and super gather semblance analysis was used to determine the RMS velocity field. The stack section shows a set of shallow reflectors interpreted to correspond to the top and bottom of the confining unit. The aquitard thins by about half from the north end to the south end along the reflection line. The continuity of the top and bottom of the aquitard was disrupted by a few faults interpreted along the line. None of these faults juxtapose the surficial aquifer against the Memphis aquifer but it is possible that the faults themselves may act as a hydraulic connection between the surficial aquifer and the Memphis aquifer and thus serve as pathways for a potential leakage. The refraction tomography technique was applied to the first arrival data and it revealed three depressions that are interpreted as paleochannels on the upper part of the confining unit, which is consistent with the background geology of the area. These inferred paleochannels may suggest that ancient river channel erosion may contribute to the process responsible for the formation of aquitard breaches in this area.

Radioactivity in fossils at the Hagerman Fossil Beds National Monument

Since 1996, higher than background levels of naturally occurring radioactivity have been documented in both fossil and mineral deposits at Hagerman Fossil Beds National Monument in south-central Idaho. Radioactive fossil sites occur primarily within an elevation zone of 900–1000 m above sea level and are most commonly found associated with ancient river channels filled with sand. Fossils found in clay rich deposits do not exhibit discernable levels of radioactivity. Out of 300 randomly selected fossils, approximately three-fourths exhibit detectable levels of natural radioactivity ranging from 1 to 2 orders of magnitude above ambient background levels when surveyed with a portable hand held Geiger-Muller survey instrument. Mineral deposits in geologic strata also show above ambient background levels of radioactivity. Radiochemical lab analysis has documented the presence of numerous natural radioactive isotopes. It is postulated that ancient groundwater transported radioactive elements through sand bodies containing fossils which precipitated out of solution during the fossilization process. The elevated levels of natural radioactivity in fossils may require special precautions to ensure that exposures to personnel from stored or displayed items are kept as low as reasonably achievable (ALARA).

Geoelectric resistivity sounding of riverside alluvial aquifer in an agricultural area at Buyeo, Geum River watershed, Korea: an application to groundwater contamination study

Twenty profiles of vertical electric soundings (VES) were obtained in a riverside alluvium at the Buyeo area, South Korea, to examine the variations of subsurface geology and associated groundwater chemistry. The combination of the VES data with the borehole data provided useful information on subsurface hydrogeologic conditions. The vestige of an ancient river channel (e.g. oxbow lake) was identified on the resistivity profiles by the lateral continuation of a near-surface perched aquifer parallel to the river. Such a perched aquifer is typically developed in the area with a clay-rich silty surface alluvium which prohibits the infiltration of oxygen. Therefore, groundwater below the oxbow lake shows a very low nitrate concentration and Eh values under the strong anoxic condition. The distribution of water resistivity is correlated with that of measured total dissolved solids concentration in groundwater, while the earth resistivity of the aquifer shows a significant spatial variation. It is interpreted that the earth resistivity of the aquifer is mainly controlled by the soil type rather than by the water chemistry in the study area.

Insect faunas associated with palaeolithic industries from five sites of pre-Anglian age in central England

Fossil insect faunas are described from five sites where organic silts fill ancient river channels. Two of the sites (Waverley Wood and Brooksby) are in the English Midlands and the other three of them (High Lodge, Happisburgh and Pakefield) are in East Anglia. Their stratigraphical contexts can be shown to pre-date the Anglian (Elsterian) Glaciation. All these localities are associated with palaeolithic implements. Three of them, Waverley Wood, Brooksby and High Lodge, are riverine deposits related to the pre-glacial Bytham River valley. The channel at Happisburgh probably dates from the same period though it was probably not part of the main Bytham River valley. The insect fauna from the pre-glacial channel at Pakefield suggests that it is not of the same age as the others. The insect assemblages include exotic species that enable stratigraphical correlations to be made with other sites in central England. They provide detailed information on the local environment and regional climate at the time when palaeolithic peoples were living in central England.

Ancient Changjiang channel system in the East China Sea continental shelf during the last glaciation

Based on the data of high-resolution seismic profiles, an ancient river channel system of the last glaciation occurred along the Zhedong and Xihu depression in the southeast of Hupijiao rise. The distribution of the channel fill system shows that the ancient Changjiang River went through the Changjiang depression into the low land plain of the outside continental shelf during the low sea level cycle of the last glaciation. The big channel fill into Okinawa Trough is not found due to the depletion of the river kinetic energy in the low land plain. The river discharge dispersal was of an important role to the dilution of the northern Okinawa Trough sea at that time Six ancient river channel systems (A-F), which are main distributaries of ancient Changjiang in the East China Sea continental shelf during the last glaciation, may be buried off the modern Changjiang estuary. The distribution of these channels coincides with the zonal elevations in the sea floor.

Electromagnetic detection of deep freshwater lenses in a hyper-arid limestone terrain

In the hyper-arid desert of Central Oman, freshwater lenses are found lying on a regional saline water table. These lenses have developed where recharge from infrequent cyclonic rainfall has collected in shallow depressions on the Tertiary limestones of the Central Plateau and in the catchments of ancient river channels draining the Plateau. Central-loop time-domain electromagnetic (TDEM) sounding was applied as a method of reconnaissance exploration for these lenses at two sites, a shallow depression extending over an area of 60 km 2 and a wadi gorge draining a catchment of 3400 km 2. These results were subsequently tested by drilling. In the case of the shallow depression, drilling intersected a freshwater lens up to 18 m thick at a depth of 92 m. TDEM resistivity-depth inversion showed that the corresponding high resistivity zone included both the lens and overlying unsaturated rocks, and that the depth to the saline interface could be accurately predicted. Where drilling failed to intersect a lens, TDEM inversion resulted in a consistently low resistivity zone in which the water table could not be resolved. By invoking the Archie formula modified for the presence of clays, it is thought that the higher resistivity of the vadose zone observed over the lens may be explained by a reduction in the clay conductivity factor resulting from higher pore-water resistivity. In the case of the wadi gorge, low regional resistivities were also recorded over the limestones on the survey margins, and high resistivity anomalies over the freshwater lens within and extending away from the gorge. Again, TDEM was found to be useful as a reconnaissance method and for mapping the depth to the underlying saline aquifer, but not for predicting the thickness of the overlying freshwater lens.

Characteristics, evolution and distribution of Quaternary channel calcretes, southern Jordan

AbstractCemented and calcretized conglomerates of Quaternary age are found within ancient river channels exposed at various heights (between +1 and +125 m) above the current bed of the Wadi Dana in southern Jordan. In cross‐section, the calcrete deposits are typically lensoid in shape and are found infilling palaeochannels cut into the bedrock. The fossilized channel sediments preserve evidence of past river conditions, sediment loads, source areas, phases of river down‐cutting and sediment accretion, as well as post‐depositional alteration processes.Samples have been analysed in thin section and under the scanning electron microscope in order to determine the calcrete micromorphology, cement types and crystal sizes. The results show that the river deposits have undergone significant displacement and replacement of the detrital grains by CaCO3, and this has resulted in the cementation in places of over 4 m of river material. The cements display an alpha‐type fabric with no evidence of biogenic activity. The nature of the cement fabric within and between deposits differs as a function of two key variables: (i) the specific location within the channel and (ii) height above the modern wadi floor. Firstly, in many of the deposits cement crystal size varies, with sparite dominating at depth within impermeable palaeowadi channels, whereas on the flanks of the channels and near the top of the channels micrite is the main type of cement. These variations are thought to be a result of differences in the length of residence time of calcium carbonate‐rich fluids in different parts of the channel and the spatially varying influence of evaporation. Secondly, distinct changes in cement fabric can be seen in channels of different ages with a reduction in the amount of micrite and an increase in the amount of secondary recrystallized pore‐filling spar over time. Copyright © 2004 John Wiley & Sons, Ltd.

An ancient river channel system incised on the Precambrian–Cambrian unconformity beneath Jackson County, Ohio

We analyzed a migrated three-dimensional (3-D) seismic reflection data set collected from Jackson County, Ohio, using volume-based voxel visualization technology. Adjusting the opacities of voxels in a time slab centered on the Precambrian reflector revealed a drainage channel system incised on the Ohio Precambrian surface, approximately 1460 m (4800 ft) below sea level. Formation sculpting of the Precambrian surface produced an image of 100-m (330-ft)-wide tributaries on the Precambrian unconformity joining to produce a 400-m (1320-ft)-wide channel roughly parallel to the subsurface trend of the Grenville front beneath Ohio. Broadening and splitting of the zero-phase seismic wavelet that defines the Precambrian reflector reveals the channels. The seismic signature is caused by thin-bed interference effects caused by reflections at the boundary between the channel fill with the overlying Mount Simon Formation and the boundary with the underlying Precambrian surface. The seismic images, therefore, locate a new lithologic unit in the Ohio subsurface. The channels are older than the overlying Mount Simon Formation and so must be at of least Middle Cambrian age. The channel morphology indicates flow in the direction of the Rome trough, approximately 60 km (37 mi) to the south, likely transporting sediment to that basin. Given the tiny volume of Ohio sampled by 3-D seismic methods, such buried channels must be common on the Precambrian surface.

Laboratory and field measurements of the modification of radar backscatter by sand

Over the last two decades, the use of synthetic aperture radar (SAR) to address geologic problems has expanded as new applications for radar have been developed. One of the earliest and perhaps most surprising results from orbital SAR images of the Sahara was that, under certain conditions, radar signals penetrated up to several meters of sand to reveal subsurface features such as ancient river channels. Subsequent studies of radar penetration of arid sand deposits have dealt with factors that govern the ability of radar to penetrate a sand cover. This paper presents results from a laboratory experiment in which radar backscatter from a surface of rocks was measured under controlled conditions as a function of frequency, polarization, incidence angle, and sand cover thickness. The sand used in the experiment had a moisture content of 0.28 vol.% and caused calculated average attenuations of 4.2±1 dB/m for C-band and ∼11±2 dB/m for X-band. Results from the experiment were compared to field measurements of sand thickness during acquisition of airborne radar images. In AIRSAR images, the extent of dry sand in a dune field appears best in C-band because longer wavelength L- and P-band signals penetrate thinner sand deposits. Images of wet sand (4.9 vol.%) suggest that L-band was able to penetrate thin sand even though that sand was wet. Together, these laboratory and field measurements contribute towards a better understanding of how a sand cover modifies the radar backscatter of a surface.

Observing earthquake‐related dewatering using MISR/Terra satellite data

On 26 January 2001, at 8:46 am, the Gujarat province of India (see Figure 1A) was hit by destructive earthquake.This earthquake, considered one of the two most damaging seismic events in Indian recorded history, caused the death of about 20,000 people and affected 16 million individuals. Both local residents and post‐earthquake survey teams reported the fountaining of water and sediments on the ground, especially in the Rann of Kachchh, which formed deposits known as sand and silt blows [e.g., Bendick et al., 2001; Jain and Lettis, 2001; Tuttle et al., 2002]. The water flow was significant enough to reactivate ancient river channels and to form shallow lakes. (Extensive information concerning the Gujarat earthquake can be found on the following Web sites: http://geoinfo.usc.edu/, http://cires.colorado.edu/, http://www.ceri. memphis.edu/, http://home. hiroshima‐u‐ac.jp/.)

Strombolian and effusive activity as precursors to phreatomagmatism: eruptive sequence at maars of the Pinacate volcanic field, Sonora, Mexico

The Pinacate volcanic field, Sonora, Mexico, contains 400 cinder cones and eight maars. It is noteworthy that most of the maar-forming, phreatomagmatic eruptions were immediately preceded by effusive and Strombolian activity rather than occurring when magma first approached the surface. The Strombolian activity may have facilitated access of groundwater to the conduits in this arid region. The field evidence suggests that phreatomagmatism is inhibited unless the magma flux is low relative to the rate of water supply and unless the top of the magma column has subsided, probably below the water table. The latter condition is difficult to prove in the absence of direct observation, and alternative hypotheses involving disturbance of the conduit system are considered. The spatial distribution of maars in the Pinacate and the lithology of their associated tuffaceous ejecta both may reflect the course of an ancient river channel whose permeable gravels were pierced by the magmatic conduits.

Late Quaternary depositional history of the Reuss delta, Switzerland: constraints from high‐resolution seismic reflection and georadar surveys

AbstractGlacial erosion has caused overdeepening of many alpine valleys. After retreat of the ice, they were filled with heterogeneous deposits of glacial, lacustrine and fluvial sediments. A typical example of such a valley segment and its infill is the Reuss delta on the southern shore of Lake Lucerne in Switzerland. To obtain a detailed three‐dimensional image of this valley segment, the ETH Institute of Geophysics has acquired several two‐dimensional, high‐resolution seismic and georadar profiles, and conducted a three‐dimensional georadar survey. Interpretations of these geophysical data were constrained by a geological core extracted from a borehole 300 m deep near the investigation site. The seismic profiles imaged ca. 600 m of sediment infill above bedrock. Based on their reflection characteristics, five different deposition units were distinguished. These units were interpreted as a succession of clay/silt at the base, followed by different sand units with variable but generally increasing amounts of gravel. This succession represented a prograding delta that filled the southern part of Lake Lucerne. The latest fluvial development of the region is best represented by the georadar data. In particular, the three‐dimensional georadar data set provides a detailed view of an ancient braided river channel Copyright © 2002 John Wiley & Sons, Ltd.

Sedimentary Features of Shallow Ancient River Channels on the Northern Shelf of the South China Sea1

Abstract Quaternary buried ancient river channels are widespread in the shallow‐level sediments of the northern shelf of the South China Sea. The sedimentary sequence mainly of fluvial deposits comprise an important component part of the low‐stand system tract and transgressive system tract in the study region. The plannar variation and spatial association of the sedimentary features such as incised valley fillings, deltaic foreset wedges and block slides of shelf‐marginal fans reflect the palaeogeographic environment during the fall of the regional sea level in the northern part of the South China Sea. Based on the high‐resolution seismic reflection data and gelogical data from boreholes, the present paper makes an integrated interpretation of the Quaternary ancient river channels in the shallow sediments of the study area, studies the sedimentary features of the ancient channels such as their spatial distribution, seismic facies reflection indicators, sedimentary facies and sand‐body types, and discusses their formational setting and evolutionary model, with the main purpose to render a service to the hydrocarbon resources exploration and development and marine engineering in the northern shelf of the South China Sea.

The Efficiency of Vertical Drains Piercing Flat-Lying Beds at Piedra Del Aguila Dam

This paper analyzes the problem of determining the pattern of flow to expect through a sequence of flat-lying beds of varying permeability which are pierced by a series of equally spaced vertical drains. A single permeable bed is assumed to be bounded by two impermeable beds from above and below and the influence of a reduction in screen efficiency is evaluated. This work arose from design work associated with the Piedra del Aguila hydroelectric project in Argentina in which the left abutment of the dam consisted of an ancient buried river channel filled with a sequence of sand and gravel sediments of varying clay content mixed with layers of volcanic tuff. The outcome of the study is that a practical limit of intercepting 80% of the flow is feasible and that this limit depends strongly upon the efficiency of the drains. All suspected aquifer beds must be drained and drain efficiency should be monitored over time.

Coast-parallel palaeochannels off southern Namibia

Boomer and airgun seismic data revealed ancient river channels incised into the middle shelf between Kerbehuk and Chameis Bay, Namibia. This palaeochannel complex, some 15 to 20 metres deep and often several hundred metres wide, cuts into Upper Cretaceous strata and is frequently deeply buried by sediment of Late Quaternary age. The channels were obviously formed during a sea-level regression to below — 100 metres as the channels' banks lie at — 90 metres off Kerbehuk and at — 105 metres west of Chameis Bay. An acoustic blanketing layer south of Kerbehuk and inadequate data prevent knowledge of their true extent, but it is surmised that these channels parallel the present-day coast, perhaps for more than 50 kilometres. The reason for their strange course is not known.