Geomorphological Phenomena Research Articles

Altitudinal Zonation of Selected Geomorphological Phenomena in an Alpine Periglacial Area (Abisko, Northern Sweden)

It is common knowledge that an altitudinal zonation of geomorphological phenomena exists on a large scale, but will this theory also be applicable to a small alpine, periglacial area? A sample of data is obtained by qualitatively describing 286 squares of 500 × 500 m each in a study area of 700 km2 near Abisko, northern Sweden. For each gridcell data on altitude, aspect, slope, geology and geomorphology are gathered. The representativeness of the sampled altitude, aspect and slope data is investigated for the entire study area, using a Geographical Information System and the Chisquared test. The altitudinal frequency distributions of geomorphological features are analysed through means and standard deviation values. Finally, groups of forms often occurring together (TWINSPAN groups) are described with respect to their altitudinal zonation. Specific forms and groups of process related forms show a distinct altitudinal zonation. Several phenomena show an altitudinal frequency distribution resembling the normal curve. This indicates that even in the investigated small area, some form occurrences might be directly related to climate variables.

Tipología y cartografía por fotointerpretación de los humedales de las cuencas del Duero y del Tajo

In recent years, the concept of wetlands has broadened, as have the factors contributing to their genesis and maintenance, especially those related to groundwater. Photointerpretation, aided by field observations, permits their classification and typification according to dominant characteristics. The present paper describes the differences between groundwater discharge and recharge areas in the wetlands under study according to their morphology, distribution, associated vegetation, presence or absence of salt-bed enclaves, geomorphological phenomena such as hummock-hollow complexes and gilgai microrelief, etc. The conclusions distinguish four large groups of wetlands: recharge ponds, local lineal discharges, intermediate diffuse discharges, and regional diffuse discharges.

Closed basins and Vertisol formation in the rincon lagoon (Andalusia, Spain)

A study was made of the genetic relationship between the geomorphological phenomenon of closed basins and Vertisol formation in an area of Southern Spain. The lithology of the area, the low erosive power of the drainage system and the semi-arid climate are factors which favour the seasonal hydromorphism responsible for the evolution of original material into Vertisols. Depth dissolution of Keuper saline materials gives rise to the creation of basins, where water accumulates, forming laggons. Although El Rincón lagoon is now a closed basin, in the past it formed part of a larger lacustrine area which to a great extent gave rise to the blackening of the soils.

Remote sensing of sediment transfer processes in playa basins

Summary Landsat Thematic Mapper and Multispectral Scanner data have been used to detect changes in the spectral reflectance and absorption of three playas in south-central Tunisia. Change detection images have been used to analyse changes between wet and dry seasons and between different years. Changes in geomorphological phenomena are interpreted from changes in soil and foliar moisture levels, differences in reflectance between different salts and sediments, and the spatial expression of geomorphological features. The intra-annual changes that can be detected from multidate imagery include surface moisture, texture and chemical composition, vegetation cover and the extent of aeolian activity. Detected inter-annual changes are divisible into those restricted to playa margins—sedimentation from sheetwash and alluvial fans, erosion from surface runoff, and cliff retreat—and those found at central playa locations which are related to the redistribution of water, salt and sediment.

A preliminary study of tidal current ridges

Tidal current ridges, widely distributed geomorphological phenomena over the continental shelf of the world, are studied. They are formed by tidal current and the trend of their sand bodies runs parallel to the direction of tidal current. There are two types of the plane shapes: the parallel and the fingered. Conditions of forming tidal current ridges are the velocities of tidal current ranging from 1 to 3.5 knots and the supply of abundant sediments. Tidal current ridges often develop in following morphological locations: the bays, estuaries, the mouths of channels, as well as the offshore area with strong tidal current. Tidal current ridges occur generally at a water depth of less than 35 metres.

Coriolis Force and Baer Law

According to the Baer law - often applied in geomorphology - what we call the Coriolis force causes the shifting of water flows regardless of their speed and direction. The author pays attention to the fact that many geomorphological phenomena remain quantitatively unexplained (with the aid of modern mathemathical-physical methods). On many examples he shows that in comparison with other agents (wind, oscillations of the streamline, tectonics) the Coriolis force is very small to be of any importance.

MODEL EXPERIMENT IN GEOMORPHOLOGY

For an appropriate explanation of geomorphological features, it is necessary to study both the characters of materials which constitute the features and the transformation of the features. Model experiments dealt in this paper offer one effective method to analyze the latter i. e., to examine the laws on the transformation of the features and their fundamental equations. If the experiment is to be considered from the point of view of investigating the fundamen-tal equations, numerical experiments operated by computor today have the similar meaning with model experiments. In either case the features in the prototype should be reproduced in the experiment. Numerical experiments are often useful when proper controlling factors and the laws of their working mechanism are well known. On the other hand, model experiments are sometimes operated in cases where their laws are not well known, because they can be operated with some knowledge on controlling factors in the trial and error steps. As to geomorphological phenomena, generally it is difficult to obtain proper equations for them, and then model experiments may be used to estimate the basic relations among them. The first problem in carrying out the model experiments on geomorphological pheno-mena is that the appropriate dynamic similarity conditions should be observed. The fundamental conditions for satisfying the similarity laws are P1/m1=P2/m2=……=Pn/mn (1) or Pi/Pj=mi/mj (i, j=1, 2, …, n) (2) Setting Pi/Pj=πp, mi/mj=πm we obtain πp=πm (3) where p is a physical factor in the prototype, and m that in the model. Eq. (3) indicates that pr-numbers in the prototype must be equal to those in the model for the phenomenon to reappear in the model. But it is seldom possible that all π-numbers in the model are in conformity with those in the prototype. This is the limitation of the model experiment. In some cases, however, it is possible to operate the experiment by easing the similarity law i. e., dividing a pheno-menon into some local regions in space and time. In the model experiment on gully morphology, the eroding force by surface runoff was assumed to be a dominant factor. The fundamental equation of surface erosion is given by Horton (1945), which may be written as follows dmp/dtp=kepApτep (4) with m: eroded mass, t: time, ke: erosion proportionality factor, A:area, τe: eroding force per unit area, and suffix p: prototype. The scaling relations are developed simply by postulating that the fundamental equation be valid in the prototype as well as in the model. Hence Eq. (4) becomes dmm/dtm=kemAmτem (5) in the model. Here the suffix m indicates the model. As the physical factors in the model and those corresponding in the prototype are related by scaling ratios, the ratio of Eq. (4) to Eq. (5) may be written as follows dmp/dmm dtm/dtp=kep/kem Ap/Am τep/τem (6) Using m ∝ ρ8l3, A ∝ l2 and τe ∝ ρwV2, Eq. (6)become s ρwp/ρsp kevp=ρwm/ρsm kemVm (7) with ρs: the density of soil, l: length, ρw: the density of water, and v: velocity. Here, all variables are expressed by representative quantity.

レバノン山脈の気候地形

Lebanese Mountains running along the eastern coast of Mediterranean Sea are about 3000 m high and consist of jurasic and cretaceous limestones. Several geomorphological phenomena derived from lithology and climatic conditions develop in these mountains.Several undulated erosional surfaces which are strikingly contrast of deep valleys with high cliffs are well reserved. The limestone composing the Mountains is weak enough to be cut into deeply by water erosion but it resists to mechanical weathering, so the erosion is restricted only along the streams and the slopes and erosional surfaces are apt to be reserved.At the head of the streams there are great cirque-like landforms, represented with “Cirque de Cedres” and have been regarded as glacial cirques by several authors. These landforms, however, are also ones derived from lithology and it is impossible to think them glacial cirques. These landforms seem to have been created by the landslides occured frequently under the different climatic conditions in the past.Small hollows, distributing generally on the erosional surfaces above 2000 m high, have been often considered as nivation hollows. But these hollows seem to be karst landforms and their distribution is controlled with the underground water system. Therefore it is not correct to relate these hollows with firns.Patterned grounds develop widely on the gentle slopes in the alpine zone of Lebanese Mts. For the formation of these landforms intensive destruction of bedrocks and productions of gravels and small particles are needed at first. The grain size composition under the present climate is favourable to the formation of patterned grounds.In this Mountain tree limit altitude is estimated to about 2500 m high, though it is not clear at the present time. Astragalus and perrenial herbs (Vicia canescene) distribute instead of trees. Judging from this, the lower periglacial limit is estimated to have been at 2600-2700 m high. On the area above this lime debris production and movement were vivid, and the area below this line soil formation was predominant and patterned grounds occur only as extrazonal phenomena here.Periglacial deposits belong Riss and Würm ice ages are observed around Qornet es Saouda and other places. These old deposits are consolidated. Riss deposits are coarser than Wurm deposits. And both deposits are coarser than the deposits on the present slopes.

SYMPOSIUM: QUANTITATIVE METHODS IN GEOGRAPHY-THEIR HARD- AND SOFT-WARES

It is well-known that quantitative methods have made a remarkable progress in many disciplines and have brought the diversification of their study objects and the expansion of their applications. These tendencies have clearly appeared in geography. In this field it has been vigorously done to develop various kinds of techniques and appliances for obtaining geographic numerical data, to apply some of quantitative methods to them and to present the findings by these efforts in a form of model. The study along this line was made an accelerative progress by the quantitative revolution in the beginning of 1960's, so that it has greatly contributed toward the development of geography. On the other hand, this progress has met with some problems involving the limitation of quantitative techniques or methods. In addition, it has offered many important and basic themes to the discussion of geographical nature, for the techniques or methods twine closely with the geographical methodology. These themes are idiographic versus nomothetic approaches, quantitative nature as opposed to qualitative one of geographic phenomena, individual versus aggregative approaches, the distinction between correlation and causation, and the possibility for building geographic theory. Although none of these themes have been given adequate answers, it is obvious that they have set a new guideline to both fields of physical and human geography. The quantitative works which were called Chorometry appeared in the geographical studies in Japan in 1930's. Some of these studies have continuously been done in the field of physical geography, wheares in the field of human geography they were ceased due to the insufficient research for data and the method of analysis. In the recent quantitative studies, however, this shortcoming is fairly but not completely swept off. The aim of this symposium is to discuss the three questions described below. (1) What kind of efficiency and limitation the quantitative methods have in terms of geographic studies? (2) How should the study concerning methods to solve various geographical problems be located in the field of geography? (3) How could the study mentioned above be related with the nature of geography? The members of the symposium consisted of twenty-four reporters and commentators, four chairmen, two organizers and a great number of participants. Although there had been some discussions concerning with three questions through the session, there were much left to be discussed. Twelve papers presented were in the following: (1) K. Kashiwaya pointed out that model experiment was of much efficient in the case of being difficult to obtain the data of landform development, and he showed the model of gully evolution, which was characterized by considering two parameters, such as the inertial force of water and the resistant force of soil. (2) M. Pukuda reviewed some applications of harmonic analysis to the landform studies and offered the results obtained in analyzing the spectral power densities of landforms in Hokkaido. He pointed out the relations of estimated spectrum to the interval of sample dots in topographic maps. (3) M. Hirano and S. Yokota explained some possibilities of numerical analysis for geomorphological phenomena. They indicated the necessity to publish topographic digital maps and to establish a geomorphological data bank. (4) I. Tsuchiya's concern was directed to suggest the advantages and weaknesses of measuring the surface temperature by the infrared radiation thermometer as a technique of remote sensing. He explained this direction by showing an example of measurements of snow surface temperature in the eastern slope of Mt. Hoken in Nagano Prefecture. (5) K. Yamabe first showed a hydraulic model to evaluate the fluidity of sea water on the basis of the residence time of fresh water.

Paleogeomorphology and its Application to Exploration for Oil and Gas (With Examples From Western Canada)

Under the term paleogeomorphology are grouped all geomorphological phenomena which are recognizable in the subsurface. Buried relief features with a marked three-dimensional geometry are of importance to the petroleum geologist whenever they lead to the trapping of hydrocarbons. Paleogeomorphic traps form a third and distinct group which ranks in importance with stratigraphic and structural traps as a major mechanism for localizing hydrocarbon occurrences. They are not simply another type of stratigraphic trap, but form by themselves a category of considerable economic significance. Paleogeomorphic traps can not be analyzed, nor can their occurrence be predicted, by stratigraphic or structural methods of study, but must be treated as a geomorphological problem. Of the man types of buried relief features, some are of greater interest to the petroleum geologist than others. In this paper, the morphology of buried erosional landscapes is discussed in greater detail. Other types of buried relief features are fossil reefs, barrier beaches, and submarine canyons. Hydrocarbons may be trapped either directly or indirectly as a result of paleogeomorphological processes. In either case, the traps may occur below or above (against) the morphological surface. Numerous examples of the effects of erosion are known from the Paleozoic and Mesozoic buried landscapes of western Canada and the Mid-Continent area of the United States. Hydrocarbon traps occur below the highs on such erosional surfaces as well as in sandstone bodies deposited in the lows on these surfaces. The rules which govern the formation of ancient landscape forms are worked out in detail, with particular emphasis on the application of quantitative geomorphology to the pattern of the ancient drainage system and on such features as summit levels and the influence of geological factors (er sion-resistant levels, influence of faults and fractures, etc.). Weathering and underground solution also play a role in providing both reservoirs and buried traps for oil and gas. The method of analysis must take into account (1) the structural attitude of the strata below and above the erosional surface, (2) the lithology of the formation overlying the unconformity (if used for isopachous mapping), (3, 4) synsedimentary structural movements and the compaction factor in the formation overlying the unconformity, (5) problems of correlation, (6) reservoir development, (7) presence of a seat seal, and (8) other factors. Paleogeomorphology provides an interesting evaluation of modern geomorphological thinking. The fossil relief forms frozen by the transgression of younger rocks neither disprove the validity of the classical peneplain concept, nor do they support fully the newer ideas regarding slope retreat. The actual conditions found are described by a re-definition of the old term paleoplain. The summit level is an intrinsic part of this feature, and not a dissected earlier peneplain. A new geomorphological concept introduced here concerns the alternation of obsequent and resequent interfluve spurs. Buried landscapes should provide a high percentage of the future oil and gas fields yet to be discovered in North America. The most important stratigraphic levels at which buried landscapes occur are those that formed after major periods of orogenesis. Their geographical locus corresponds to the broad belts of subsequent transgressions.

Application of Paleogeomorphology to Exploration for Oil and Gas: ABSTRACT

Hydrocarbon traps are customarily subdivided into two main classes: structural and stratigraphic. A third important class, hitherto not considered separately, includes hydrocarbons trapped in buried hills, ancient sandstone-filled valleys, fossil reefs, and other primarily geomorphological phenomena. These are termed as paleogeomorphic traps. The analysis of and prospecting for this type of trap must proceed along purely geomorphological lines of reasoning. These include both form and process: the form creates the trap, but the process shapes the form. Trapping may be below or above the paleogeomorphological surface, and be either direct or indirect. Paleogeomorphology includes all geomorphic phenomena recognized in subsurface geology, i.e., all buried-relief features, whether formed on land or under water. Geomorphic processes may be divided into constructive and destructive. Constructive forms of interest to petroleum geologists are dunes, barrier beaches, organic reefs, etc. Destructive processes create hills and valleys, underground drainage in carbonates, submarine canyons, etc., and create or destroy porosity by weathering. End_Page 1567------------------------------ Fossil organic reefs have a multitude of morphological characteristics which may be explained in terms of hydraulics, rate of subsidence, influence of deep-seated faulting, and other factors not of a strictly stratigraphical nature. The interpretation of buried landscapes presents many problems still unresolved among geomorphologists and also high lights several lesser-known geomorphological phenomena. Subsurface data reveal that many landscapes exposed for millions of years, although technically peneplains, still have sufficient relief for the accumulation of sizable hydrocarbon reserves. The solution of paleogeomorphological problems is aided greatly by applying quantitative geomorphological principles. The geological aspects of paleogeomorphology concern primarily the identification of erosion-resistant and less resistant horizons and the influence of structure (folding and faulting) on ancient drainage systems. Sandstone bodies filling buried valleys commonly are dissected by river meanders and thus exhibit shapes that are different from the shape of the valley. The analysis of a drainage system from headwaters to delta can help to relate sandstone reservoirs to source areas. End_of_Article - Last_Page 1568------------

Techniques of Exploration for Buried Landscapes: ABSTRACT

Hydrocarbon traps are customarily subdivided into two main classes: structural and stratigraphic. A third important class, hitherto not considered separately, includes hydrocarbons trapped in buried hills, ancient valleys, fossil reefs, and other primarily geomorphological phenomena. These are referred to as paleogeomorphic traps. The analysis of and prospecting for this type of trap must proceed along purely geomorphological lines of reasoning. Paleogeomorphology covers all geomorphic phenomena recognized in subsurface geology; i.e., all End_Page 536------------------------------ buried relief features, whether formed on land or under water. Geomorphic processes may be divided into constructive and destructive. Constructive forms of interest to petroleum geologists are dunes, barrier beaches, organic reefs, etc. Destructive processes create hills and valleys, underground drainage in carbonates, submarine canyons, etc., and create or destroy porosity by weathering. The interpretation of buried landscapes presents many problems still unresolved among geomorphologists and also highlights several lesser known geomorphological phenomena. Subsurface data reveal that many landscapes exposed for millions of years were not peneplains but still showed considerable relief. The presence of well-developed slopes favors the theory of scarp retreat. Summit levels may also be related to contemporaneous erosional processes. The solution of paleogeomorphological problems is greatly aided by applying quantitative geomorphological principles. The geological aspects of paleogeomorphology concern primarily the identification of erosion-resistant and less resistant horizons and the influence of structure (folding and faulting) on ancient drainage systems. End_of_Article - Last_Page 537------------