Residual Hills Research Articles

Field survey and analysis of hillslopes on tower karst in Guilin, southern China

Limestone dissolution in tropical and subtropical humid southern China created residual hills with steep slopes, a landform that is referred to as tower karst. Two types of tower karst landform feature, fenglin or peak forest (isolated towers) and fengcong or peak cluster (linked-base towers), were identified in Guilin. Previous studies proposed two hypotheses regarding their origin and evolution. One is the sequential evolution model from peak cluster to peak forest. The other is a parallel development model, which postulates that both peak cluster and peak forest have developed simultaneously. Through detailed field survey and analysis of slope forms on tower karst in Guilin, it was found that the mean slope angle of the towers is very high (62·4°) and ranges from 60° to 75°. There is no significant difference in mean slope angle and slope angle distribution between towers in the peak cluster basin and peak forest floodplain areas. Mean slope angle increases with intensified fluvial dissection. Three levels of caves in the towers of the peak forest in Guilin were identified in previous research. The isolated towers of the peak forest as well as scattered residuals of peak cluster are generally distributed in the centre of the Guilin syncline. Favourable circumstances of allogenic water concentration indicate that development of the peak forest resulted from the combined effects of subcutaneous and subterranean dissolution as well as subsequent collapse and recession by fluvial erosion after uplifting. By contrast, peak clusters generally occur on the limbs of the syncline or at the periphery of the Guilin basin with relatively higher elevations. The thick vadose zone and predominantly vertical flow suggests that peak clusters are mainly formed by the combination of intensive uplifting and the enhancement of original dolines. The evidence of slope survey and slope analysis suggests that both isolated towers and linked-base towers developed simultaneously but by different mechanisms of formation and different combinations of development processes. Copyright © 2000 John Wiley & Sons, Ltd.

Exposure age and erosional history of an upland planation surface in the US Atlantic Piedmont

The upland planation surface in the Piedmont of central New Jersey consists of summit flats, as much as 130 km2 in area, that truncate bedding and structure in diabase, basalt, sandstone, mudstone and gneiss. These flats define a low-relief regional surface that corresponds in elevation to residual hills in the adjacent Coastal Plain capped by a fluvial gravel of late Miocene age. A Pliocene fluvial sand is inset 50 m below the upland features. These associations suggest a late Miocene or early Pliocene age for the surface. To assess exposure age and erosional history, a 4·4 m core of clayey diabase saprolite on a 3 km2 remnant of the surface was sampled at six depths for atmospherically produced cosmogenic 10Be. The measured inventory, assuming a deposition rate of 1·3 × 106 atoms cm−2 a−1, yields a minimum exposure age of 227 000 years, or, assuming continuous surface erosion, a constant erosion rate of 10 m Ma−1. Because the sample site lies about 60 m above the aggradation surface of the Pliocene fluvial deposit, and itself supports a pre-Pliocene fluvial gravel lag, this erosion rate is too high. Rather, episodic surface erosion and runoff bypassing probably have produced an inventory deficit. Reasonable estimates of surface erosion (up to 10 m) and bypassing (up to 50 per cent of total precipitation) yield exposure ages of as much as 6·4 Ma. These results indicate that (1) the surface is probably of pre-Pleistocene age and has been modified by Pleistocene erosion, and (2) exposure ages based on 10Be inventories are highly sensitive to surface erosion and runoff bypassing. Copyright © 2000 John Wiley & Sons, Ltd.

Uplift histories revealed by landforms of the Scandinavian domes

Abstract It has long been recognized that the Scandes (Scandinavian Mountains) consist of one dome in southern Norway and one in northern Scandinavia. In this paper a low dome is also identified in southern Sweden. The latter is associated with remains of sedimentary covers of different ages, which makes it possible to date different topographies with associated saprolites and to understand the denudational and uplift history of the dome. The eastern flanks of the two domes in the Scandes show distinctly different topographies. The flank of the southern dome is characterized by an undulating hilly relief similar to exhumed Cretaceous surfaces in south Sweden, while the flank of the northern dome is characterized by a stepped sequence of plains with residual hills similar to Tertiary surfaces in the south. The difference in relief probably indicates different uplift histories for the two domes.

Hydromorphogeological investigations in a typical khondalitic terrain using remote sensing data

In order to examine the influence of tectonic and morphological characteristics on the occurrence and movement of ground water in Khondalitic (garnetiferrous sillimanite gneiss) suite of rocks, hydromorphogeological studies were carried out in a typical Khondalitic terrain situated in Viziangaram district of Andhra Pradesh, India. Different land forms have been identified with the aid of visual interpretation of Landsat imagery together with ground truth data in order to prepare hydromorphogeological and lineament maps. Drainage map and topographic slope map have been prepared using toposheets. These maps and other collateral data like well yields and geophysical data have been analysed to evaluate the ground water prospective geomorphic units. Ground water prospect areas are located in shallow buried pediplains and wash plains in such a way that they are identified on gently sloping uplands situated between the lineaments. Non potential areas are those, which are, low-lying areas near the streams and high slope areas near the residual hills. It is found near low lying areas i.e., beneath the streams that the khondalite must have transformed itself into kaoline and acting as barrier evidently preventing lateral movement of ground water forcing it to accumulate in flat upland areas between two streams or lineaments. From the lithologic cross sections it is found that there are four distinct subsurface layers namely (1) top soil, (2) highly weathered khondalite (kaolinised layer), (3) moderately weathered and fractured khondalite (aquifer layer) and (4) basement of granitic gneiss.

Hydromorphogeological Mapping for Groundwater Prospecting Using Landsat-MSS Images — A Case Study of Part of Dhanbad District, Bihar

The Dhanbad district in Bihar, feces acate water scareity and is chronically drought prone. The groundwater resources in the area have not been fully exploited. The present study was undertaken to evaluate the groundwater prospective zones, Landsat-5 MSS data of band-2 and band-4 and false colour composite of band 2, 3, 4 were interpreted visually to differentiate different hydromarphogeological units and to delineate the major trends of lineaments. The different geomorphic features identified are linear ridges, residual hills, pediplain, buried pedtment and dissected pediplain, besides lineaments. The study shows that the pediplain and buried pediments are promising zones for groundwater prospecting.

Glaciofluvial erosional morphology and sediments of the Coronation–Spondin Scabland, east-central Alberta

Spatially discontinuous meltwater channel networks on the Canadian Prairies are usually interpreted as having formed subaerially in front of the retreating Laurentide ice sheet. Evidence in the Coronation–Spondin scabland, east-central Alberta, supports an alternative formation by progressive channelization of a subglacial sheetflow of water. The scabland is an integrated channel network with varying degrees of anabranching, the channels having highly variable sizes, shapes, and orientations. Enhanced scour at some channel confluences reflects contemporaneous channel utilization. Channels also display convex-up, concave-up, and undulatory along-channel profiles, with some junctions at the same elevations. Longitudinal grooves in large-scale channels are associated with numerous boulder deposits. Residual hills, demarcated by channels, display composite and streamlined forms. Superimposed on residuals are erosional transverse bedforms, longitudinal grooves, and undulating surfaces that indicate submergence for all but the last phase of channelization. Glaciofluvial deposits are found as pendant bars on the distal end of some large, flat-topped residuals, or as mantles superimposed on some residuals. The scabland is interpreted to have formed as a waning, subglacial sheetflood diverted around hummocky terrain to the southwest. A rapidly subsiding ice roof, and instability in the flow, eventually concentrated meltwater into discrete channels. Abrupt cessation of flow left discontinuous gravel–boulder deposits, and ice sheet loading formed small-scale glaciotectonic features as the ice recoupled to its bed. Subsequent deglaciation barely modified the scabland, leaving it straddling part of the modern topographic divide between the Battle and Red Deer river basins.

Geomorphology in the tropics: a study of weathering and denudation in low latitudes

Geomorphology from a Tropical Perspective. PROCESSES AND PRODUCTS OF WEATHERING. The Alteration of Rocks Under Tropical Conditions. Weathering Profiles and Saprolites. Laterites, Bauxites and Duricrusts. DENUDATION PROCESSES. Surface Processes in Tropical Climates. Landsliding and Other Mass Movement. QUATERNARY ENVIRONMENTAL CHANGE AND LANDFORM DEVELOPMENT. Quaternary Environmental Change in the Tropics. Landforms and Deposits Associated with Environmental Change. THE EVOLUTION OF TROPICAL LANDSCAPES. Etching Processes and Landform Development. Erosional Terrain and Residual Hills. Long-Term Landform Evolution. References. Indexes.

Tertiary palaeoclimatic history of the southeastern Colorado Plateau

On the southeastern Colorado Plateau Tertiary erosion surfaces have been preserved below the cover of the Eocene Chuska Sandstone and the late Tertiary Bidahochi Formation. Investigations of the geomorphological attributes of the erosion surfaces and laboratory analyses of the soils and weathering materials as well as the sediments on the surfaces gave substantial information on the climate and the relief-forming processes which were responsible for their formation. In some places the surfaces cut across the underlying Mesozoic sedimentary rocks with a marked angular unconformity, but these truncating reaches are restricted to areas where soft material crops out. Resistant rocks from lithologically controlled cuestas, hogbacks and residual hills below the Tertiary cover. X-ray analysis of the clay minerals shows that the surfaces have not been subject to intensive chemical weathering and soil-forming processes. There is no change in the mineral content from the bedrock to the weathered material. These results apply to the (early) Eocene to Palaeocene Tsaile surface (underlying the Chuska Sandstone) and the Miocene Hopi Buttes surface (underlying the Bidahochi Formation). The results demonstrate that the climatic conditions have not changed decisively during the Cenozoic and were much the same as today. It is concluded that the Colorado Plateau has been dominated by a dry climate since the Laramide orogeny with the possible exception of the early Palaeocene. Thus the Colorado Plateau is out of phase with the general palaeoclimatic situation in western North America in the early Tertiary where at that time warm and moist conditions prevailed. The Colorado Plateau, before its separation from the Basin and Range province, was situated in a topographically lower position in the rain shadow of the southern Rocky Mountains and the Central Arizona Highlands, which at that time formed a barrier stretching from western Arizona to New Mexico.

Contribuição geomorfológica ao estudo de escarpas da serra do mar

Autores têm-se referido à definição geomorfológica de escarpa, ou vertente escarpada, sem levar em conta as características topomorfológicas de comprimento, declividade e amplitude topográfica, básicas para o entendimento de sua evolução. No litoral norte do Estado de São Paulo, a serra do Mar, caracterizada por um conjunto de escarpas que marcam a borda oriental dos terrenos pré-cambrianos do Planalto Atlântico, apresenta dois compartimentos distintos. O primeiro, a montante, possui vertentes escarpadas, com segmentos retilíneos alongados e declivosos, entalhados por vales e anfiteatros de fortes amplitudes topográficas. Seu recuo faz-se paralelo, guiado por linhas litotectônicas de fraqueza, ou em alvéolos; processos de alteração e pedogênese produzem materiais levados para jusante por movimentos de massa em prancha ou por coluviação, preferencialmente durante episódios pluviais intensos. Num segundo compartimento, a jusante, nas médias e baixas encostas, as vertentes escarpadas são degradadas ou rebaixadas em diferentes níveis topográficos, que se desenvolvem sobre esporões secundários, rampas erosivas e coluviais, morros residuais e alvéolos, governados pelo traçado estrutural. Mamelonizadas por processos de intemperismo e pedogênese, escoamento pluvial superficial, fluxos internos e freáticos, estas formas sofrem ainda movimentos de massa, principalmente rotacionais; rampas coluviais e taludes de detritos formam por entre os esporões e morros rebaixados. Foram observadas relações estreitas entre os mapeamentos de declividades, cicatrizes de escorregamentos e isopletas. Nas vizinhanças de Caraguatatuba, duas áreas com grande ocorrência de cicatrizes apresentaram isopletas acima de 30, coincidindo com as vertentes de grande comprimento e alta declividade nas zonas de maiores amplitudes topográficas.

Soil-landscape relationships in the Udi-Nsukka plateau, Nigeria

A simple hillslope representative of soils in the Udi-Nsukka plateau was studied in order to establish relationships between landscape positions and soils and also to determine the pedological processes which have acted jointly with geological processes to produce the landscape. Pedons were located in the summit, footslope and toeslope positions to correspond with the mapped soil series which are Uvuru, Nsukka, and Nkpologu series respectively. Data on the morphological, physical and chemical properties indicate that there was lateral movement of materials from the summit to the toeslope. This initial movement helped in the evolution of the cuesta landscape. However, presently not much erosion is going on in the summit due to the gravelly nature of the soil and the presence of laterite. This has resulted in the dome shaped and flat topped residual hills. Pedogenic processes are active in the footslope and toeslope positions because of the stability of that portion of the landscape. The pedological processes of clay and iron translocation, colluviation and leaching and the geological processes of water erosion and lateral movement of particles have interacted leading to the evolution of the landscape.

Mineralization, origin and age classification of ferruginized sandstone in the Bahariya Oasis, Western Desert, Egypt: A contribution to the origin of red beds

The Bahariya Oasis is a depression and the topography of it is mainly controlled by anticlines. It lies in the Egyptian Western Desert and is characterized by isolated, cone-shaped residual hills which are aligned parallel to anticline axes in the southern part of the depression. These hills are capped by ferruginized sandstone of nearly black colour with an average iron content of 20 wt.%. The existence of a humid, warm climate with heavy rainfalls and a strong influence of vegetation during the Cretaceous-Tertiary transition provided reducing and weakly acid conditions. They enabled the mobilization of Fe and Mn out of manganese-bearing ilmenite and magnetite, primarily present in the sandstone. The existence of an oxidation barrier accompanied by an increase in pH value resulted in the precipitation of these elements. There is a definite correlation between the position of iron enrichment and tectonics in that area. The fracture planes, formed in the crestal region of the anticlines, exposed the deeper parts of the sandstone. As a consequence the oxygen of the air gained access to the subjacent sandstone strata, resulting in the formation of oxidation barriers in relatively deep-seated parts of the sandstone. The enrichment of iron and manganese was furthermore controlled by: 1. (1)The process of up-arching during the formation of the anticlines, the thick sedimentary sequences in the crestal region of the fold, thus facilitating the penetration of supergene solutions. 2. (2)Apart from the predominant supergene nature of the iron enrichment, a lateral one, though on a subordinate scale, also took place. 3. (3)The oxidation barrier is supposed to be coincident partly with an evaporation barrier. The iron horizons therefore constitute an epigenetically mineralized sandstone of the Bahariya Formation. The former term Radwan Formation for this type of ferruginized sandstone, now preserved in the form of residual hills, is therefore invalid.

Geomorphic inheritance and the development of tower karst

AbstractFour genetic types of tower karst are identified, the most typical consisting of residual hills protruding from a planed carbonate surface veneered by alluvium. Two extreme possibilities for tower karst evolution are recognized: a direct development that is independent of any previous morphology and a sequential development that depends explicitly on the morphological characteristics of a previous cockpit karst phase. Examples of both are described, although the latter appears the more common. South China tower karst is examined in this light. Palaeomagnetic analysis of cave deposits in a tower near Guilin indicate the feature to be a time‐transgressive landform. Four principal controls of tower development are discussed and a model of tower evolution is presented.

Some Working Hypotheses on the Geomorphology of Sweden in the Light of a New Relief Map

AbstractA relief map of Sweden has been constructed by the Land Survey on the basis of an elevation data base. The relief developed in the Precambrian bedrock is analysed and interpreted with the aid of weathering remnants and outliers of cover rocks of various ages. The following conclusions can be drawn. The different bedrock units have characteristic fracture patterns which reflect old, mainly Precambrian tectonics. The fracture pattern is more or less well expressed in the topography due to differences in the denudational history. In the Early Cambrian most of the basement surface was denuded to an almost level plain with only few residual hills. Cambro-Silurian strata were deposited on this primary planation surface. In Mesozoic time the Palaeozoic cover was stripped from elevated areas in southwestern and northern Sweden, where weathering penetrated deep along old fracture zones creating an uneven weathering front. The resulting undulating hilly land is still a significant component in the topograph...

Some Working Hypotheses on the Geomorphology of Sweden in the Light of a New Relief Map

A relief map of Sweden has been constructed by the Land Survey on the basis of an elevation data base. The relief developed in the Precambrian bedrock is analysed and interpreted with the aid of weathering remnants and outliers of cover rocks of various ages. The following conclusions can be drawn. The different bedrock units have characteristic fracture patterns which reflect old, mainly Precambrian tectonics. The fracture pattern is more or less well expressed in the topography due to differences in the denudational history. In the Early Cambrian most of the basement surface was denuded to an almost level plain with only few residual hills. Cambro-Silurian strata were deposited on this primary planation surface. In Mesozoic time the Palaeozoic cover was stripped from elevated areas in southwestern and northern Sweden, where weathering penetrated deep along old fracture zones creating an uneven weathering front. The resulting undulating hilly land is still a significant component in the topography of southern Sweden (now exhumed from Jurassic and Cretaceous covers) and within large parts of the Norrland Terrain. Other areas, for instance the fissure valley landscape in the Stockholm region, where the sub-Cambrian surface is close to the plateau surfaces between the shallow and narrow valleys, were exhumed much later. The weathered fractures of the Mesozoic etchsurface have been emphasized in the topography of southern Norrland, probably due to unstable tectonic conditions in the Tertiary and later times. As the South Småland Peneplain in southern Sweden large areas in northern Norrland were flattened in the Early Tertiary due to stable tectonic conditions in combination with alternating arid and humid climates prohibiting the evolution of deep saprolites. In other parts of the Norrland Terrain the Mesozoic etchsurface seems to have been preserved, though the causes for preservation is unclear.

Geomorphic features of a part of Cuddapah and Nellore districts, Andhra Pradesh — Using remote sensing techniques

An area of about 1000 square kilometres in Cuddapah and Nellore districts of Andhra Pradesh is studied to bring out the different landforms and other geomorphic features, their material content and distribution, the processes that have acted and are acting in the evolution of landscape and ultimately to get an idea of the geomorphic history of the area. The data obtained during the present study is mainly through remote sensing-techniques (Landsat image and airphoto interpretation) with field checks. The study area forms a part of southeastern Cuddapah Basin and consists of structurally disturbed and deformed sedimentary sequence of varied lithology. The impor-tant rock types in the area are granites, gneisses, quartzites, shales, phyllites, limestones and dolomites. The area presently comes under semi-arid climatic zone. The different landforms recognised and mapped in the area are hog-back ridges, piedmont fans, valley fills, river built plain, abandoned channels, point bars, ’ V‘ shaped valleys, piedmont zone, colluvial plain, residual hills, besides lineaments.

The pre‐glacial evolution of Wales

AbstractThe classical explanation of the development of the Welsh landscape by the effects of a pulsed ‘eustatic’ uplift during the Cenozoic times is challenged by new data on the geology and geomorphology of Wales and the adjacent regions.The post‐Caledonian surface developed over most of Wales in the upper Westphalian plays a major role in landform development. Since its emergence before mid‐Cretaceous times, the Welsh Massif has suffered a long subaerial evolution which favoured a powerful chemical weathering. In Anglesey and St. David's Land, residual hills were formed by a process of differential weathering, and downwearing in saprolites. The Millstone Grit quartzites have been deeply weathered and dolines or flat‐bottomed basins have been developed.From Cretaceous to Miocene times, a morphotectonic equilibrium has existed between uplift and denudation, so that, in the major part of Wales, the original planation surface was constantly maintained by lowering on itself and in some places it is possible to prove that no more than a few dozen metres of rock thickness disappeared during that period. Several main escarpments were produced by the warping of the planation surface along sharp flexures, during Neogene times. The Cenozoic vertical movements were controlled by the Caledonian or pre‐Caledonian tectonic pattern which has divided the continental crust into major structural units.Welsh tectonic development is related to the opening of the North Atlantic, associated stresses reactivating ancient lines of weakness in the heterogeneous lower crust or upper mantle.

The nature of slope profiles on some residual hills in the Jamalpur-Kiul Hills, Monghyr, India

The nature of slope profiles on some residual hills in the Jamalpur-Kiul Hills, Monghyr, India

Morphology and distribution of residual limestone hills (mogotes) in the karst of northern Puerto Rico: Discussion and reply

No Abstract Available. The article discussed was published in the Bulletin , v., 426–432.

Morphology and distribution of residual limestone hills (mogotes) in the karst of northern Puerto Rico: Discussion and reply

Morphology and distribution of residual limestone hills (mogotes) in the karst of northern Puerto Rico: Discussion and reply

Morphodynamics and Morphogenesis of Pediments in the Deserts of Iran

The present semiarid to arid climatic conditions in Iran lead to morphodynamics that form pediments. Study of fossil weathering profiles and correlative sediments provides evidence that processes similar to those of today were also active in Neogene and Pleistocene times. The pediments in Iran have no savannah type planation surfaces as precursors. However, small scale climatic variations and/or tectonic movements led to the development of several pediment levels and different kinds of pediment dissection. Pediments are formed not only by the retreat of mountain fronts, as some authors have claimed, but also by the planation of the mountains from drainage lines within them. Autochthonous slope development in Iran is capable of steepening slopes without lateral undercutting. Fluvial flattening of slopes of small residual hills can also be observed. Pediments are not only plains of transportation, but are lowered and flattened by autochthonous denudational processes. This degradation results largely from the so-called 'exchange of components', which is effective because of intensive weathering during the long intervals between floods. The morphogenesis of pediments is considered to embrace four stages, here styled: the mountain-bahada stage, the pediment stage, the pediplain stage and the desert dome stage.