Fossil Valley Research Articles

Hydrodynamic, hydrochemical and isotopic characterization of the waters of the quaternary aquifer of Bahr-El-Ghazal, north central Chad.

Located in the middle of the Sahel, the study area is an integral part of the Bahr-El-Ghazal region. It is crossed by a fossil valley, which has a geological history similar to that of rivers that disappeared under the influence of climate change where evaporation phenomena were intense. From the hydrogeological point of view, the free water table of this region is housed in sedimentary geological formations of different natures. It passes from the sand tablecloth to that of the fluviolacustrine clays. In some cases, the latter confer particularly bad chemical qualities to the water, even though groundwater is the main source of drinking water for the local population. For this reason, a study aimed at understanding the different mechanisms that govern the chemical functioning of the aquifer of the Bahar-El-Ghazal region has been carried out. It is with this in mind that a piezometric study is being carried out in the first instance. This reveals the presence of some hydrodynamic anomalies. Thus, a shallow depth of the body of water is observed in the Harr and in the sandy formations of the extreme West. However, underground flows oriented from these two zones towards the central part characterize a deepening of the water level. Subsequently, a hydro-chemical study was undertaken. As regards the chemical facies, they also show an evolutionary character. They pass from calcium and magnesian bicarbonate facies to chloride or sodium and potassium sulphate facies in the piezometric depression. The values of the isotopic composition of the studied groundwater vary from -4.86 to 4.04‰ and -35.60 to 14.50‰ and delta 2H respectively.

Importance Ethnobotanique Et Des Menaces Sur Le Délice Du Boboye, Neocarya Macrophylla (Sabine) Prance, (Chrysobalanaceae) Dans La Vallée Fossile Du Dallol Bosso (Niger)

The present study conducted in the Dallol Bosso fossil valley aims to know the local perception of the level of threat on the Neocarya macrophylla species in order to provide indicators of sustainable management of the natural stand. To do this, surveys were conducted in two agro-ecological zones.The collection of information was carried out through a simple questionnaire based on the woody stand, the sources of supply and the part of the plant taken from the woody food species, as well as the threats they suffer and their causes. It appears that the most dominant species is Neocarya macrophylla ; a multipurpose species among others, used for food, medicine and wood.The survey also reveals the presence of twenty four (24) ligneous foods species among which eighteen (18) are common to both zones. Analyses showed, the excessive cutting of the wood and the unfavorable climatic conditions as the main factors resulting on potential threat of these species. At the same time, threats on Neocarya macrophylla, a characteristic species of Dallol Bosso valley were identified on the field.

GEOLOGY OF THE AQUIFER AREAS OF AN INDUCED INFILTRATION INTAKE IN THE CITY OF WROCŁAW

The paper presents the results of geological research in the area of induced infiltration aquifer in the city of Wrocław. Based on drilling and geophysical prospection (GPR) data, a 3D model of the aquifer has been developed, showing the architecture of the aquifer-forming sediments. The best hydrogeological and spatial-related parameters are displayed by gravels directly overlying the impermeable basement represented most likely by pre-Odra River sediments and filling fossil valley structures. A geological-physiographic map, compiled based on the LiDAR digital elevation model, revealed two youngest sedimentary valley systems related to the recent channels of the Odra and Oława rivers. The structure of these deposits is typical of meandering river cyclothems. The use of its anisotropy can significantly improve the efficiency of infiltration of surface water into the water-bearing and conducting gravels that constitute the main usable aquifer.

Analysis of the relationships between the spatial arrangement of palaeovalleys and contemporary valleys of Central Poland in the light of GIS methods

The article presents an example of application of selected GIS methods for showing connections between the course of palaeovalleys and contemporary valleys in Central Poland. The analysed area was shaped in the conditions of environment as early as the Palaeogene and Neogene, but the greatest impact on the present-day landscape came from the morphogenetic processes which operated in the Quaternary.Palaeogeographic studies of the analysed area often point to the possible dependencies between the contemporary landscape and its substrate, particularly as regards the valley system. In order to verify this hypothesis, on the basis of archival cartographic materials and a Digital Elevation Model of the current terrain, a procedure for conducting analyses with the use of commonly available GIS tools was proposed. Results of the conducted analysis allow for stating that the major river valleys of Central Poland in large part correspond to the arrangement of the fossil valley system, and the relationships are most easily noticeable for the largest valleys.

Depositional environment of the glacigenic deposits from the Holy Cross Mountains (Poland) – interpretation based on macro- and microstructure analyses

In this paper an attempt is made to identify the depositional environment of glacigenic deposits from the central part of the Holy Cross Mountains (Kielce-Łagów Valley). In this area, the primary glacial relief is very poorly visible, mainly due to its modification by subsequent denudation processes. The study is based on detailed sedimentological (macro- and microstructural) analysis of the deposits. The bottom part of the deposits consists of gravelly and sandy facies. They are overlain by diamicton facies, with a small proportion of sandy facies. Clayey/silty facies occur in minor quantities. The investigations indicate that these deposits represent an ice-marginal environment. Local stagnation of the ice sheet lobe was controlled by the geological structure of bedrock (karstified and faulted limestones) and the features of a fossil valley. The ice-marginal depositional environment is indicated by the predominance of sediment-gravity flow deposits, a low proportion of sorted deposits, as well as the interfingering/alternating of mass flow deposits and waterlain deposits. Deformation occurring in the deposits is of gravitational origin. They also show traces of periglacial processes. The deposits constituted an ice-marginal moraine (dry end moraine with limited topographic expression). Micromorphological analyses provided data for genetic identification of the deposits, and allowed the inference about rheology of deposition and deformation processes. However, in some cases, they did not allow unequivocal genetic classification of the deposits. The results of presented investigations confirm the opinion that detailed and complete explanation of deposit origin requires both micromorphological analyses and macroscopic field sedimentological and structural studies.

How to resolve Pleistocene stratigraphic problems by different methods? A case study from eastern Poland

Different methods have been used to determine the stratigraphic position of Pleistocene alluvial deposits, particularly fluvial interglacial deposits. Near-surface deposits of a meandering river, developed in point-bar and oxbow lake facies, in the Samica River valley (near Łukow, eastern Poland) have been investigated. The fossil valley is incised into the till plain and the outwash. The fluvial succession is locally overlain by solifluction deposits. All the deposits underwent sedimentological analysis. The petrographic composition of basal till occurring in the vicinity of a fossil valley was determined with the method of indicator erratics. Fluvial deposits were examined by pollen analysis and plant macrofossil analysis of oxbow lake facies. Absolute dating methods were applied to the deposits (thermoluminescence methods: TL and additionally IRSL). Lithological differences between fluvial and the surrounding glaciofluvial deposits were identified and their lithostratigraphic position assigned. Petrographic analysis of till and palaeobotanical analyses of oxbow lake facies gave compatible results. Fluvial deposits were formed after the Sanian 2/Elsterian Glaciation, during the Mazovian/Holsteinian Interglacial. Luminescence dating of the fluvial deposits by the TL MAX method yielded the most relevant results (412-445 ka), which indicate that these deposits were formed during the end of the MIS 12 and beginning of the MIS 11 stage.

Water level fluctuations in selected Wielkopolski National Park lakes in 2012 against changes noted in 2007-2008

AbstractThe results presented in this paper of water level fluctuations in selected lakes of Wielkopolski National Park have a preliminary character, contributing new information to the knowledge on this area. Five lakes situated in three distinct tunnel valleys were selected for research: Jarosławieckie, Góreckie, Budzyńskie, Witobelskie and Łódzko-Dymaczewskie. The water level was measured from December 2006 till January 2008 and from January till December of 2012 with ca. monthly frequency. An increase in the water stage was noted in the autumn-winter period, which was rather unusual. The comparison of years 2007 and 2012 indicated higher water levels in the latter. The amplitude of the water level was higher in flow-through lakes due to the reaction to precipitation in early spring as well as different catchment features. Specific water level fluctuations in Lake Góreckie are probably related to the influence of groundwater of the Wielkopolska fossil valley.

Land-use and land-cover change detection in a semi-arid area of Niger using multi-temporal analysis of Landsat images

Recent studies using low-resolution satellite time series show that the Sahelian belt of West Africa is witnessing an increase in vegetation cover/biomass, called re-greening. However, detailed information on local processing and changes is rare or lacking. A multi-temporal set of Landsat images was used to produce land-cover maps for the years 2000 and 2007 in a semi-arid region of Niger, where an anomalous vegetation trend was previously detected. Several supervised classification approaches were tested: spectral classification of single Landsat data, temporal classification of normalized difference vegetation index time series from Landsat images, and two-step classification integrating both these approaches. The accuracy of the land-cover maps obtained ranges between 80% and 90% overall for the two-step classification approach. Comparison of the maps between the two years indicates a stable semi-arid region, where some change in hot spots exists despite a generally constant level of rainfall in the area during this period. In particular, the Dallol Bosso fossil valley highlights an increase in cultivated land, while a decrease in herbaceous vegetation was observed outside the valley where rangeland is the predominant natural landscape.

Bacterial diversity of the rock-water interface in an East Antarctic freshwater ecosystem, Lake Tawani(P)†

Schirmacher Oasis is one of the few ice-free plateaus in East Antarctica that maintains a unique distribution of over 120 microbial-rich, dynamic freshwater lakes, most of which are unexplored. In this study, we describe the bacterial diversity of the rock-water interface in Lake Tawani(P) using culture-independent Bacterial Tag Encoded FLX Amplicon Pyrosequencing (bTEFAP), clone library construction, and culture-based analysis targeting the eubacterial 16S rRNA gene. Lake Tawani(P)was formed in a fossil valley by the accumulation of snow and glacial melt through surface channels into a low-catchment depression. Overall this lake exhibited thirteen bacterial phyla and one-hundred and twelve genera. The Qiime bioinformatics analysis on the bTEFAP alone exhibited higher coverage of the bacterial composition in Lake Tawani(P) than the clone library construction or culture-based methodology. Particularly due to the higher sensitivity of the bTEFAP approach, we detected and differentiated members of the phyla: Chloroflexi, Gemmatimonadetes, Planctomycetes, Nitrospira, and Candidate Division TM7 that other methods were unable to reveal. Nevertheless we found that the use of multiple approaches identified a more complete bacterial community than by using any single approach. Investigating the bacterial diversity of the Schirmacher Oasis lakes, especially those connected through surface channels and encompassed by valleys, will help unravel the dynamic nature of these unique seasonal, freshwater lakes, which potentially harbors highly adapted bacterial taxa with defined ecological functions.

Constraining the origin of clacretes in Letlhakeng valley Botswana: physico-chemical and stable isotopes (O, C) studies

This paper details the mineralogical, chemical and stable isotope abundances of calcrete in the Letlhakeng fossil valley. The stable isotope abundances (O and C) of calcretes yielded some values which were tested against the nature of the calcretes – pedogenic or groundwater type. The Kgalagadi (Kalahari) is a vast terrain, mantled by duricrusts (in valleys, pans). This study assessed calcrete formation criteria in the Letlhakeng valley. The oxygen and carbon isotopic values point to calcretes in this valley as being of groundwater type. The vegetation that coincides with the calcrete formation is dominated by C4 vegetation. The mineralogy of the duricrusts is dominated by carbonate (calcite, dolomite) and quartz. The carbonate material has pH values of about 8, with TDS of 89 to 217mg/L.Key words: calcrete; mineralogy; stable isotopes; Kalahari; palaeo-environment.

Sedimentary architecture of the Loire River drowned valleys of the French Atlantic shelf

AbstractThe analysis of a dense grid of high resolution seismic profiles collected offshore the present day Loire River estuary indicates the presence of a thick and complex Pleistocene coastal wedge between the coast and 50 meters water depth. Most of this coastal wedge is preserved in a fossil valley network starting 10 km off the coast on the “Precontinent Breton” topographies and wedging out progressively 50 km in the offshore where the shelf flattens. This system is comprised of three main valleys 30 km long, 40–60 m deep and 0.7 to 4 km wide each, in average, with a northern valley incompletely filled by sediment. These valleys are incised into Eocene (Ypresian-Bartonian) sedimentary rocks lying unconformably on the metamorphic and magmatic rocks of the South Armorican Massif basement. The coastal wedge is comprised of six seismic units. From the base of the valleys to the seafloor, these units are successively interpreted as (1) colluvial (U1) and braided river deposits (U2), overlain by restricted marine to estuarine sediments (U3), and (2) straight to meandering fluvial deposits (U4) giving rise vertically to floodout marine sediments (U5). The whole sediment pile is capped by open marine bioturbated mudstones (U6).This succession of seismic units is organised in two depositional sequences bounded by an unconformity of regional extent, which corresponds to a drastic change in the paleovalley fill architecture. The lower sequence fills up the southern and central valleys when the upper sequence fills up the northern valley network. Both sequences are sharply truncated by a ravinement surface at the base of the offshore shales formed during the Holocene marine transgression. The correlation of the observed depth of the incisions and transgression surfaces with the global sea-level curve provides an indirect estimate of the ages of the depositional sequences. The lower sequence is probably Saalian (130–200 Ka, MIS 6) and the upper one Weischelian (110–12 Ka, MIS 2–4 and 5a–d). The ages and the infill of these valleys are very close to the ones observed in the largest paleovalleys of the inner French Atlantic shelf (Gironde, English Channel) and consistent with the sedimentary record of the continental Loire River (stepped terraces). In the later case, the Saalian period corresponds to a sharp increase on the incision of the river that shaped the morphology and determined the location of the present-day Loire valley.

Water Resources in the Sahel Region and Its Storage System

The desertification of Sahel region along the southern Sahara desert result in the most serious environmental problems in west Africa. One of the proposed countermeasures against the desertification is afforestation in this area.We, authers, set up the anti-desertification project in this region, utilizing undeveloped subsurface water resources and solar energy which are used for the irrigation of tree-plantation and agriculture.Two years research and field survey on the underground water involved in the fossil valley of the Sahel region clarified the feasibility of construction of subsurface dam.In this paper, some characteristics of the water resources and of the proposed afforestation project in this region are summerized in view point of utilization of water. Hydrological characteristics of fossil valley are also described in relating with the construction of underground dam.The fossil valley distributing in the Sahel region cut the basement rocks downward and are filled with sand and grabel which are most suitable container for the storage ofsubsurface water. This type of water which is not developed for the present is supplied by rain fall in the corresponding area.Subsurface water stored in the fill materials of the fossil valley can be supplied enough in the dry season for the plantation, even if it is in the draught continuing a few years.The subsurface water storage system described in this paper is the most effective method for utilizing water in the Sahel region where the evaporation rate exceed some thousand millimeter a year.

A STUDY OF THE TERRACES AND THE FOSSIL VALLEY ALONG THE LOWER COURSE OF THE TOKACHI RIVER

Along the lower course of the Tokachi River, Hokkaido, one can find six terraces, as well as a buried terrace and a fossil valley by means of the electric resistivity method and test boring. These terraces are named I, II, III, IV, V, the buried terrace, and VI from upper to lower. Terrace I to V are covered by Pleistocene (or older) volcanic ashes, but terrace VI is not. It is estimated from the observations of terrace deposits that terrace V was formed at about the time of the fall of the “Erimo Volcanic Ash, ” one of Pleistocene volcanic ashes, and that terrace VI was formed at the beginning of the Holocene. The time of formation of the buried terrace is not ascertained, because data could not be obtained in the buried terrace area. Nevertheless, it seems that the buried terrace was formed soon after the formation of terrace V. It is certain from the results of electric resistivity methods and test borings that the depth of the fossil valley reached 60m. below sea level, and that it is filled with sand and gravel beds 15m. thick. The composition of terrace gravels shows that the ratio of andesite is much higher in the gravels of terraces IV, V and VI, than in those of terraces I, II and III, and that the ratio of andesite in the buried gravels in the fossil valley is also higher. Accordingly, after the formation of terrace III, volcanic activity near the upper coerce of the Tokachi River became stronger. The profile of the fossil valley bottom seems to continue to intersect the submarine shelf surface, the margin of which exists at 60m. below sea level, 14km. off the sea shore. So, one can imagine that the old shore-line was there.

PROBLEMS ON THE STREAM-PIRACY BETWEEN THE TENRYU AND THE TOYO RIVERS IN CENTRAL JAPAN

It has long been believed by many geographers in Japan that the Tenryu River beheaded the Toyo River along its middle course near Nakappe town, and then the Ochise River, a tributary of the former, encroached through the wind gap into a fossil valley of the previous main stream of the latter, having remained a valley watershed (Talw asserscheide in German) at Ikeba village. This valley watersched has a length of about 500 meters, sloping gently to eastward. Its west end is terminated by the valley-head of the Shimano-kawa, one of the source streams of the present Toyo River ; and the eastern margin slopes gently into the stream of Tero-sawa, one of the source streams of the Ochise River in the Tenryu drainage basin, forming several alluvial cones. Through his observations, the writer cannot approve of the opinion of stream-piracy above mentioned. The reasons are as follows:—1) The breadth of the Ikeba valley watershed is too narrow to assume that it was the previous main stream of the Toyo River.2) Both sides of the valley watershed show concave slopes with no terrace landforms.3) The outcrops along the valley floor are all composed of angular and ill-sorted talus deposits without water worn gravels. So the Ikeba valley watershed cannot be assumed to be the fossil valley of the Toyo River. On one hand, some geologists presumed a fault-line along this valley watershed, the pioneer of whom was B. Naumann, who found the “Medianlinie”, the main geotectonic line in southwestern Japan. Though the writer could not find any actual evidence of a fault, it is rather probable that the valley watershed here was originally formed as a fault valley.

THE SOUTH AUSTRALIAN CONTINENTAL SHELF AS A HABITAT FOR PETROLEUM

The Continental Shelf off South Australia is predicted to be a preferred habitat of petroleum. Non-metamorphosed sediments which are known or presumed to extend onto this shelf include Permian, Cretaceous and Cainozoic sediments. A single presumed Permian trough lying seaward of, and sub-parallel to, the Coorong is interpreted (aeromagnetic data) to extend to possibly 4,000 feet. As part of the Permian fossil valley system of central-eastern South Australia is is predicted to be filled by shales and sands with limited marine facies, and by glacigene sediments. The north-south orientation of the trough would require a landmass to the south from which the Permian glaciers originated. Some form of continental drift may be required to satisfy this requirement.An east-west graben or geosyncline (Gambier-Otway Basin) choked with Cretaceous mudstones and sub-greywackes projects across the shelf in the extreme south-east. Landward dips at depth extending well out beneath the shelf, may suggest a southerly boundary to the basin consistent with a pre-existing landmass in this direction.Extensive erosion at the close of Lower Cretaceous times accords with major geological change at least in more southerly shelf areas. Marine sedimentary onlap and overlap become conspicuous elements, and the accumulation of oceanward thickening sedimentary deposits is more in keeping with outbuilding terrace development. A major structural break accordingly is indicated at the end of the Lower Cretaceous, at which time development of the modern continental shelf began.The Murray River had its principal outlets in the extreme south-east zone during mid-Cretaceous to early Tertiary times, but shifted to its present position during late Cainozoic at which time its sediments were swept across the developing shelf south of Kangaroo Island. Thick sedimentary developments in each of these areas provide promising environment for petroleum generation. These are areas of extensive coastal bitumen activity.Principal petroleum prospects are to be expected within the Middle Cretaceous to Tertiary developments, but older Cretaceous and Permian deposits are potentially prospective.

BEYPAZARI GÜNEYİNDE BİR FOSİL VADİ VE JEOMORFOLOJİK ÖNEMİ

The valley of “Cetin Bogaz (Strait)”, located in the 12 km south of Beypazari, near Tahirkoy, was formed as a result of the erosion of loose filling material in the Quaternary period, following the hard inner eruptive rock which it was carved into and the Pliocenic river-lake sediments which it was then filled with. Cetin Strait is a deep valley, formed through the re-erosion of the loose clayey sand sediments of a fossil valley. The study provides a brief description of the forming process of this valley near Beypazari, along with a survey of its characteristics.

SOME EXAMPLES OF THE UNDERGROUND STRUCTURES OF ALLUVIAL PLAINS DISCOVERED BY THE SEISMIC PROSPECTING

The seismic method is the best way to recognize clearly the under ground structures of alluvial plains. This report shows the results of our investigations on the three alluvial plains as follows: 1. Ofunato plain: This plain is the small delta that was construct ed in the drowned valley. We set 4 lines of measurement as shown in Fig. 1. Fig. 2-3 are the results of this investigation along the lines. The layers, in which the velocity of the longitudinal wave are 5.0 & 5.7km/sec, are palaeozoic and 6.0 & 4.2km/sec are granit. The surface of these rocks is the fossil valley before it drowned. The layer of 2.4 km/sec is the diluvial gravel bed, and the others are alluvial. Under the delta, several faults were discovered. 2. Joganji plain: This is the alluvial fan which was made by River Joganji. Fig. 4-11 are the results. The layers of 2.8, 3.0 and a part of the 2.6km/sec are Tertiary, and the others are the gravel beds. At the middle of the fan, it became clear that a buried hill exsists under the gravel beds, and the ancient river course ran more west than now. E line was set at near the coast, and the altitude of the surface of the bed rock on the east end of the line was 450m high. The old river would run more east and deeper than this point. 3. Upper part of Nobi plain: This part of the plain is the fan made by River Kiso. The positions of the lines and results of the in-vestigation are shown in Fig. 12-14. The layers of 4.5km/sec is ther pre-tertiary rock. The others are all gravel beds from Tertiary to, alluvial. We can read the geological history of this area from these-geological sections.