Introduction

Problems of geomorphology, tectonics and structural geology in process of their historical development were raised and solved at different levels, depending upon recent arsenal of available methods and range of their use. Achievements in related geologic sciences made it possible to establish close correlation between the surface relief and its depth structure, which stimulated development of structural-geomorphologic investigations. Significant progress in solution of the geomorphology, tectonics, structural geology problems has been achieved due to use of aerial survey methods, and satellite imaging made it possible to see big geostructures of the crust, about existence of which experts in tectonics could only guess. So, every new method of investigation allows to the best of its ability confirming or raising a doubt in relation to the problems, which seemed to be solved, or suggest their more wide solution or, at last, establish new facts and suggest new hypotheses.

Study of the crust by means of satellite images caused creation of cosmogeological maps and simultaneously raised the issue of so-called photolineaments, i.e. linear, arc and other forms of lines of approximately the same photo-tone. As far as the most important element of photolineaments are river valleys, taking into account their good evidence on geographic maps (practically for the whole Earth surface and within wide range of scales) exactly this sign has been selected in this investigation for deep study.

It is known since long that river valleys may be often confined to tectonic distortions. At the same time till recently not a single representative structural or tectonic map, based on analysis of the river network pattern, has been drawn. It was tempting and very promising to introduce into geologic production this huge array of information.

For approbation of this methodology, Pamir and adjacent territories were selected. There are few such nodal areas within high-mountainous and high-seismic region of Central Asia which would attract attention of researchers and cause such serious contradictions in opinions as this region. Acuteness of many tectonics problems of this region preserves until nowadays. Present tectonic structure of the region, its tectonic activity that manifests itself in young dislocations, high speeds and big amplitudes of vertical and horizontal movements against high seismicity background are result of long and very complex structural evolution of the crust in greater part of the Asian mainland territory. On materials of this and neighboring regions regional concepts of “fixists” and “mobilists” were developed and checked. In addition, taking into account the fact that subject of the investigation is erosion-structural analysis, territory of Pamir and adjacent territories fit it more than any other territory, because it is characterized by presence of widely developed river network, which is well pronounced on geographic maps of different scale. Taking into account listed factors, it becomes clear, why exactly Pamir and adjacent territories were selected by us for substantiation of the method of detection and investigation of geometric regularities in structure of the river network and proving the tectonic origin of its occurrence. For achievement of this goal, we carried out a number of works and solved following problems: analysis of the Pamir and the adjacent territory river network pattern on different scales, beginning from 1:30 000 000 and bigger; compared detected erosion systems with the tectonics data; carried out erosion-structural zoning of Pamir in scale 1:2 500 000; showed on example of Pamir possibility of using the erosion-structural analysis data for improvement of the metallogenic map tectonic basis (Khetagurova V.S., 2014). In addition, we have drawn the most representative classification of erosion system consisting of 10 types, 22 classes and 48 kinds.

Obtained investigation results show that the erosion-structural analysis data of this region are both of scientific and practical significance. Example of Pamir shows possibility of using the erosion-structural analysis data for improvement of the metallogenic map tectonic basis, and this method may be used as auxiliary method of investigation during search of mineral deposits.

Methodology

Methodology of erosion-structural analysis is divided into several methods of the river network investigation, methods that give unambiguous and stable results, have good convergence and structural-tectonic sense. This is confirmed on basis of experience of the authors, accumulated during analysis of river network on many hundreds of geographic maps of different scale in different regions. In this work investigations of erosion systems of Pamir and adjacent territories are based on method of gradual detection and method of different-scale maps, which are put into basis of the erosion-structural analysis methodology (Khetagurova V.S., Umaraliev R.A., Bryukhanova G.A., 2015).

Classification of erosion systems, models, structures

Сombination of the exhumed valleys-cracks, belonging to the unified geometric system, will be hereinafter called erosion system. The most general signs put into basis of singling out of the erosion systems types for the purpose of their further classification are systemacy, consistency, prevalence, and isolation.

Systemacy in the river network pattern assumes possibility of singling out from it of geometrically characteristic erosion system. At the same time, exactly this property – systemacy – allows avoiding mistakes at decoding and classification, because even 25 – 30 % irrelevant elements, erroneously included into the erosion system, or the same amount of not taken into account elements do not influence on final result.

Consistency of the erosion system assumes such its property, when in scale of the studied map geometric elements of the erosion system are clearly traced at distance more than 2 cm over their stretching or in the area more than 4 см². Choice of these values is explained by the fact that a geological map is considered representative, when each its centimeter is confirmed by the primary documentation, and as far as erosion-structural maps are derivatives of photographic maps, requirements to them reduce two-fold.

Prevalence of certain erosion system over other geometric elements of the same territory is ensured in majority of cases by the natural processes themselves. In rare cases of equal representativeness of two erosion systems their prevalence depends upon the solved task and is ensured by the researcher.

Isolation of the erosion system proceeds from prevalence and allows using the erosion system as a unit of investigation. This property, however, does not exclude junction of erosion systems and their characteristic transitions; place of the latter is determined by areas of equal representativeness.

As far as each erosion system bears certain, only for it peculiar characteristic features, it seemed rational to constitute classification of erosion systems with stepwise subordination, having taken as initial unit kind of the erosion system which jointly with the related kinds forms a class, and the classes group into the types. Suggested classification was already checked during erosion-structural analysis of several other regions and does not seem cumbersome, because name of the erosion system, depending upon the need, may be brought to two or even one term. This classification of erosion systems is result of generalization of long experience of investigations of the authors in this field.

At present this classification consists of 48 kinds of erosion systems grouped into 22 classes and 10 types. As shows practice, the classification covers practically all kinds of existing erosion systems. It was composed in the form of “Atlas of erosion system types”, which significantly facilitates performing of erosion-structural analysis. As far as this classification incorporated experience of investigation of hundreds of maps, it itself turns out to be strong tool in carrying out the erosion-structural analysis.

Singled out 10 types of erosion systems (linear, latticed, comb, bordered, round, oval, arc, block, radial, and mosaic) characterize, mainly, majority of structural formations on land surface. Exactly this practical directedness stipulated introduction into the classification of a certain number of geologic-geomorphologic terms, like comb, bordering, block, which correspond to structures with feather joint, horst-like rise and separate blocks of crust. Linear type corresponds to linear distortions of various genesis; latticed – to known systems of cracks, mainly of magmatic rocks; round, oval and radial types correspond, as a rule, to volcanic structures and astrolabes; and arc types – mainly to edge structures, etc.

Number 22 relating to classes is, approximately, 2.5 times bigger than number of types, which is stipulated by the fact that the characteristic contains contradictory and mutually exclusive definitions (rectangular-bent, rectangular-oblique, centrifugal-centripetal, etc.). Such semantic subordination is practically convenient, because after establishment of the most general image of the erosion system the next step is made in direction of singling out of internal, diametrically opposite properties of the erosion system. Characteristic of the erosion system kind mainly makes accent on the details, which are interesting in structure of exactly this object, allowing in a number of cases estimating degree of the erosion system development and its relative age. So, for example, simple radial-centrifugal erosion system occurs, as a rule, at beginning of diapir formation, then it transfers into radial-centrifugal complex system, and development of such erosion systems terminates by the stage of round-concentric centrifugal erosion system known under name of a “broken plate”.

Method of Gradual Detection

Considered above classification of erosion systems is basis, knowledge of which is prerequisite for successful decoding of river network in any region. Just first sight at the map of a river network convinces us that it is not monotonous, predetermined only by flow of water in direction from top to bottom over the shortest lines. On the contrary, the river network turns out to be diversified by its pattern, which may be noted even by unexperienced researcher. Having glanced over the river network, we can get down to its analysis, i.e. detection of geometrically characteristic systems.

In any river network, even in the network developing on the substrate with very complex tectonic structure, always exists dominating erosion system with sufficiently clearly pronounced numerous geometric elements of this system. Singling out of such most eye-catching and noticeable erosion system, as a rule, does not cause special difficulties, and its contouring on a map by lines of double thickness (or a color) marks first from the sought erosion systems of the region. In practice, it turns out that such eye-catching and geometrically clear erosion systems are singled out at once in several places of the map. At the same time the rest river network, marked by thin lines, is simplified, and in such residual pattern, in its turn, eye-catching systems are detected, which are contoured.

Analysis at slowed down rate is carried out in several stages till the rest fragments loose sufficiently clearly pronounced geometricity. Such residual network relates to the mosaic type and should be viewed on larger scale. Having reviewed over and over the rest non-geometrized river network and compared it with “Atlas of erosion system types”, the researcher, finally, will make conclusion about exhaustion of the erosion-structural analysis data for the studied territory. In this case, it is necessary to transfer the detected erosion system on a separate drawing and get down to structural-tectonic comprehension of the results obtained. The obtained erosion-structural characteristic is described in such way, as in tectonic sense understands it the researcher which, of course, has certain knowledge about general structure of the region. Final stage of the investigation is comparison of the erosion-structural analysis data with data of previous investigations reflected on geologic maps of the same scale. It is necessary to emphasize the condition of scale equality for the compared documents, because in this case correspondence of the ranks of the compared structures is, to a certain degree, observed, while it is frequently violated at drawing of small scale maps by transformation of large scale maps when, for example, ore irregularities are transferred from one scale to the other scale despite their tectonic rank.

On the preliminarily interpreted erosion-structural map all lines of tectonic disturbances are transferred from geologic map of the same scale. It frequently turns out that significant part of tectonic disturbances either fully coincides or goes in parallel, or is placed on continuation of the erosion structures making impression of identity. If one measures length of the tectonic disturbance lines and length of their parts which lie on continuation of the erosion structures or in parallel to them, then it would be possible to determine degree of their coincidence or, and this is the same, degree of authenticity of the erosion-structural analysis data. Value of this coincidence is sufficiently high for a number of mountainous regions and constitutes, approximately, 70 % (Khetagurova V.S. et al., 2015), which convicts us in authenticity of the erosion-structural analysis method. If one compares length of the tectonic disturbance lines taken from the geologic map with length of detected erosion disturbances, it will turn out that the latter are more distributed and hence information content of the erosion-structural map concerning study of the structures is higher.

Method of different-scale maps

Detection of geometric regularities in the river network structure and further interpretation of the data obtained for the purpose of detection of the tectonic structure regularities in the studied territory is sufficiently accurately carried out using the described method. However, detection of main featureы of the territory structure does not ensure detection of all reasons and conditions of its formation and, especially, history of tectonic development, kinematics of the system and dynamic situation. For solution of this kind of problems in each separate case it is desirable to obtain information about situation in a wider region in which this territory plays role of just comparatively small part that depends upon surrounding situation. The issue of determining scale of the maps, which would be necessary and sufficient to study for getting authentic information about structure of the territory, which is of interest for us, hardly may be considered successfully solved. Some scientists (Borsuk О.А.,1974) in general consider that “analysis of a river network … should be based not on a single characteristic…, but on the general structure”, which, in relation to investigation of the erosion systems, acquired clearly pronounced structural-tectonic sense. Number of researchers note that in structure of a river network and in tectonic structures one may single out integrated morphologic regularities, which may be useful also for study of a specific territory.

Before carrying out erosion-structural analysis on maps of different scale in direction from a smaller scale to the larger one it is necessary to make sure that they meet specifications, because the maps created by mechanical enlargement do not contain higher information content. As small-scale maps, used for initial stage of the analysis, fit physical-geographic maps from general regional atlases irrespective of the projection system, because the latter, while distorting the system as a whole, does not significantly change its image and does not affect results of recognition. For the most successful construction of the erosion-structural maps, it is necessary to have sufficiently variable set of the map scales. The study has to be started from the maps of a smaller scale, on which it is possible to detect the most general features of the regularity in structure of river valleys of the region and determine position of the area at larger-scale investigations. Map scales larger than 1:1 500 000 practically are not used, because elements of river systems on them a kind of “fade away”.

Results

Tectonic Structure of Pamir

Pamir, located at connection of the biggest mountainous ridges of our planet, represents a unique geologic structure. It is peculiar for its geologic history and formations; it is characterized by big crustal thickness (more than 70 km), wide development of young granites and metamorphic rocks.

Our task is to prove by using new material, based on data of erosion-structural analysis of Pamir, tectonic origin of occurrence of river networks in this territory and carry out erosion-structural zoning of Pamir.

Summarizing studied by us regional material, collected by researchers of several generations who had different viewpoint, it is possible to characterize present state of Pamir in the following way. Pamir belongs to the segment of Alpine-Himalayan fold belt. Structure of Pamir formed eventually due to collision with Eurasia of Indian continent. Pamir mountainous nod belongs to eastern sector of interaction of late systems of Eurasia and Gondwana, and specifically it is located in zone of collision of South-Kazakh microcontinent with rigid Indian plate. In this respect, Pamir is similar to Himalayas and South Tibet. Folded structures appeared here in the place of the widest part of Tethys Ocean (up to 6 000 km according to polyspastic reconstructions of Legler V.A. and Przhiyalgovskaya I.Y. (Zonenshine L.P., 1990). At present width of folded structure of Pamir between Tien-Shan and northern edge of Indian platform is only 400 km. So, in its geologic history main place belongs to absorption of 5 000-5 500 km of oceanic crust of Tethys ocean and subsequent collision of India with Eurasia.

Structure of Pamir has at present an arc directed by its convexity to North. The arc is located at the top of so-called Pamir piling up, located above the most northern protrusion of Indian continent. Bazhenov M.L. and Burtman V.S. presented convincing paleomagnetic data, according to which they consider that this arc is secondary, it appeared at post-Paleogene time (Bazhenov M.L. et al., 1982). Its formation was connected with movement of Punjab protrusion of Indian continent in direction of Eurasia, indenting of structures of Pamir in the same direction, whereby it is assumed that this invasion of rigid die could be accompanied by slipping of crust masses to North in direction of Allay valley.

On East Pamir is separated from Kunlun Shan by Karakorum by right-lateral fault of north-western spread with shift amplitude not less than 300 km (Zonenshine L.P., 1990). In West Pamir borders with Tajik depression over narrow shift-thrust zone of river Pyandj having sub-meridian stretch. Main structural zones of Pamir are shown on the scheme (Figure 1) drawn on basis of published materials of a number of researchers (Pashkov B.R., 1979, Belov A.A., 1981, Ruzhentsev S.V., 1983, Zonenshine L.P., 1990). Usually Pamir is divided into Northern, Central and Southern parts with clear manifestation of Hercynian deformations in Northern Pamir and their absence in Central and Southern Pamir. The most principle division passes between Northern and Central Pamir over Tanymass fault, which passes in West into Hindu Kush fault, and in East into Jung Tang zone of Central Tibet. To North from this suture mantles containing geologic complexes present in late Paleozoic and Mesozoic near northern periphery of Tethys are distributed, and mantles to South from this suture contain complexes of Gondwana origin.

Figure 1: Scheme of main structural units of Pamir (drawn on basis of materials published by Pashkov B.R., Belov А.А., Shvolman V.А., Ruzhentzev S.V.,Zonenshine L.P.) Click here to view full figure

1 – outcropping of Precambrian base; 2 – Hercynian oceanic and island arc complexes; 3 – Mesozoic Rushat-Pshart zone; 4 – Mesozoic ophiolites of Bashbumbez window; 5 – geologic complexes of Gondwana origin; 6 – Triassic calc-alkaline vulcanite; 7 – Lower Jurassic granites of Karakul complex; 8 – cretaceous granites of South Pamir; 9 –main sutures-thrusts; 10 – continuation of sutures.

Listed zones of Pamir, evidently, were interconnected in first have of Cretaceous, and since then started new stage in development of this territory (Shvolman V.А., 1977). Since early Cretaceous on one hand red and variegated detrital deposits and on the other hand subaerial vulcanites of acid and medium composition were widely distributed in Pamir. They are broken through by big batholiths of subporphyritic granites and granodiorites. Radiologic age of granitoids varies from 100 to 130 mln years corresponding to young Cretaceous, although it is quite possible that exist younger, upper Cretaceous vulcanites. Possibly in Cretaceous and beginning of Paleogene Pamir was closely integrated with magmatic arc Kohistan-Ladak in Himalayas, under which subduction of Tethys ocean crust occurred. Stage of deformation connected with continental collision of India with Eurasia started in Oligocene (Shvolman V.А., 1977). At newest stage present configuration of tectonic mantles and protuberant to North Pamir arc have formed.

So, Pamir represents accretionary folded structure assembled from polytypic continental, oceanic, island arc and other complexes integrated during the period from mid-Carbon till Cretaceous and subjected to new deformations in post-Oligocene time.

Comparison of Erosion Systems and Tectonics of Pamir

As one may see from presented material, opinions of researchers about general structure of Pamir are rather contradictory, especially in the field of actual data interpretation, but at the same time, actual data are in good convergence with the erosion-structural analysis data, which represent non-distorted reflection of natural processes. For assessment of reality of existence of rupture structures, detected by methods of erosion-structural method, it is desirable to compare the results obtained with independent data of other researchers of these structures. For identification of rupture structures of the area, corresponding to the selected scale rank, we will use investigations of Suvorov A.I. devoted to faults of platforms and geosynclinals (Suvorov А.I., 1963). Comparison of erosion structures with location of deep faults (Figure 2) shows that exists rather good coincidence of the erosion system elements with deep faults. In northern part on border of Pamir with arcs of Tien Shan the noted deep fault (Figure 2, D-2 and other) bends around by wide arc the structure of Pamir and spreads into the area of piedmont valleys. Fragments of comb-double-side straight erosion system, coinciding with a deep fault, continue in middle part eastward (Figure 2, H-2), forming a band system. Evidently, according to the erosion-structural analysis data, deep fault not just bends around Pamir, but bifurcates (Figure 2, B-2) and continues in western direction where identical comb erosion systems are located. The nearer are deep faults to the central forming “die” of Pamir, the more steeply they bend coinciding with bent to the same degree valleys-cracks. The next deep fault (Figure 2, G-2) terminates exactly in the place where, according to the erosion-structural analysis data, latticed-rectangular erosion system, typical for the areas of magmatic rocks development, is located. Moving to south-west through the system of valleys, another termination of this fault (Figure 2, D-4) is noted in the place of round erosion systems location, which often coincide with volcanic apparatuses. Two next deep faults, adjacent to the central block, bend it around from West, are traced along the erosion system and unexpectedly terminate in middle part of the region (Figure 2, F-3) as well as confined to them valleys. Central elevation – “die” of Pamir – is contoured by deep faults (in understanding of Suvorov A.I.) from South, West and North, clearly follows valleys of rivers, interrupts in South-West (Figure 2, E-5), where it should be continued as show the erosion-structural analysis data. Eastern border of elevation of Pamir proper coincides with extended deep fault spreading North-West (Figure 2, I-4), which outcrops in the area of the latticed-rectangular erosion system distribution (Figure 2, H-3). Inside of Pamir elevation, deep faults are oriented in latitude direction, coincide with valleys of the same name and, in general, fall out from general structural plan of Pamir, representing fragments of possibly more ancient structures fixed in rigid rocks of foundation. In South (Figure 2, G-5) deep fault partially coincides with arc valley and then transits into edge part of Pamir elevation. Evidently, here also bifurcation (or confluence) of two deep faults takes place, and their probable position is marked on the map.

Figure 2: Erosion systems and deep faults of Pamir (faults according to Suvorov A.I. 1963). 1 – erosion systems; 2 – deep faults. Click here to view full figure

So, comparison of erosion structures with location of deep faults shows that exists rather good coincidence estimated at the level of 75-80% with significantly higher information content of erosion structures. Not less interesting, is comparison of erosion systems of Pamir with bearing of relatively small disturbances – zones of disintegration, dikes, lodes, etc. Comparison made for Central part and to somewhat larger scale (Figure 3) shows that exists very good coincidence of the position and bearing of small structural elements with main features of erosion systems (more than 60%). One should pay attention at two peculiarities of the structure detected during mentioned comparison. Firstly, part of ore-bearing structures of Pamir turned out to be oriented in north-western direction, i.e. the direction, which was obtained during erosion-structural analysis on scale 1:5 000 000, and, secondly, sufficiently representative data for confirmation of existence of the meridional structures were absent. Their number does not exceed the limits of usual norm of meridional structures occurring everywhere under influence of rotational forces of rotating Earth.

Figure 3: Erosion systems of Pamir (1) and location of interaction of linear structural elements within Pamir and in adjacent mountainous structures (according to Arkhipov I.V., 1965) Click here to view full figure

Erosion-structural zoning of Pamir on scale 1:2 500 000

Three groups of facts were put into the basis during drawing of the map of erosion-structural zoning of Pamir on scale 1:2 500 000. First group of facts represents the erosion-structural analysis data according to location of the cracks reflected in present relief and to great degree (up to 80%) inherited from previous tectonic plan. Second group of facts represents data of a geologic map as a witness of historic development of the region, and third group of facts represents to great degree contradictive data of the researchers who used different methods with non-strict interpretation of the results. Opinions of different researchers, results of their interrelation with the erosion-structural analysis data will be partially presented below in Section 3 (discussions). But it is necessary to note here that when studying history of development of vertical tectonic movements of Pamir in Pleistocene and Holocene, Belousov V.V. drew conclusion that in Pleistocene and Holocene tectonic movements of Pamir had stable ascending character. “Determining factor in Pleistocene is division of the territory, for which inherent is sub-lateral structural plan inherited from Paleozoic, into West Pamir and East Pamir meridional tectonic zones (Belousov V.V., 1975). Such extreme opinion is, evidently, based on analysis of the material relating only to Pamir elevation proper without using the data of wider mapping and structure of the region. Studying problem of thrust block of Pamir, Kukhtikov M.M. stated that materials relating to geologic structure of Pamir, obtained during investigations in 50-60^th, allowed making opinion about wide development of thrust blocks in territory of this folded structure (Kukhtikov M.M., 1981). The newest data relating to geology and tectonics of this region allow making conclusion that many quite representative structures of this kind were constructed on erroneous or insufficient actual basis. Priority in determination of tectonic style of Pamir belongs to vertical movements. At the same time Baratov R.B., Bezuglyi M.M., Ishanov M.H., and Pashkov B.R. who studied annular structures of Pamir in connection with their metallogeny, in conclusive part of their work state that “one cannot exclude that appearance of a number of annular structures is stipulated … by movement of continental plates above heated focuses of crust…ˮ (Baratov R.B., et al., 1981).

Summarizing presented and generally known ideas about structure of Pamir region, it is possible to make conclusion, with certain reservations, that during its formation stages of intensive horizontal compressions took place caused by invasion of Indian plate, which alternated with periods of repose and prevalence of vertical movements connected with preceding compression. The geologic map data are sufficiently objective reflection of reality, i.e. the most ancient rocks get exposed in South, that system of tectonic limitations has arc outline and that on this basis it is possible to assume stepwise-descending structure of Pamir.

Using analysis of even more objective geographic map, and, in particular, the erosion-structural analysis for analyzing pattern of river network, it is possible to draw conclusion that territory of Pamir disintegrates into several objectively existing parts (Figure 4).

Figure 4: Scheme of erosion-structural zoning of Pamir in scale Click here to view full figure

1. Elevation proper of Pamir of trapezoidal form (Figure 4, G-5 and other) is composed of the most ancient rocks and, possibly, experiences periodic heaves.
2. First, partially buried, continuation of stepwise foundation of Pamir covered by ancient rocks (Figure 4, E-4 and other).
3. Second buried stepwise continuation of Pamir limited by tectonic valleys of rivers Obiminyon and Obihingo (Figure 4, E-3 and other).
4. Third buried stepwise continuation of Pamir, abruptly upstanding in northern part (Figure 4, C-3 and other).
5. Fourth buried continuation of Pamir (Figure 4, B-4 and other).

These are main features of Pamir structure detected by methods of erosion-structural analysis on 1:2 500 000 .

6. Roundish moderately heaving areas in West (Figure 4, B-6 , B-5) and North-West (Figure 4, D-4).
7. Diagonal zone of disturbances of northwestern bearing (Figure 4, G-5 and other).
8. Block-quadrangular rigid structure in North-West (Figure 4 , I-2 and other).
9. Diagonal zone of disturbances of rocks of northwestern bearing (zone of western Kunlun Shan) (Figure 4, K-5 and other).
10. Sub-lateral zone of Tien-Shan arcs in North (Figure 4, J-1 and other).
11. Arc system of Hindu Kush disturbances (Figure 4, G-8 and other).

As a whole, erosion-structural zoning of Pamir and adjacent areas shows its stepwise-pyramidal structure upheaving in southeastern direction and raised along northern edge. Main tectonic factor of Pamir nod formation is pressure in northwestern direction on side of Indian plate, which is the reason of horizontal and vertical movements of Pamir.

Discussion

Majority of works dealing with analysis of river systems relates to 1960–1970. As ago as by end of 1980^th investigations in this field in Russia were practically curtailed mainly because of absence of adequate information and technological basis. In the course of geomorphological investigations, great number of works relating to study of structure and genesis of river valleys were fulfilled. It was established that hydrographic network is often connected with borders of geologic structures and selectively dissects polytypic lithofacies complexes of deposits, quickly, but ambiguously responds to manifestations of contemporary tectonics (Sladkopevtsev S.A., 1973). In 1990 the term “structural geography” was suggested (Korytnyi L.M. et al., 1990). Reviews in this field include monographies: “River systems (on example of Far East (Karasyov М.S. et al., 1984) and “Basin concept in environmental managementˮ (Korytnyi L.M. 2001).

The most precisely and clearly said about tasks of establishment of the connection between the relief forms and the tectonic structure Soviet geomorphologist Piotrovskiy M.V. who considered the morphometric mapping the burning advanced direction in geologic-geomorphological investigations. He considered that geologic-geomorphological mapping entered new stage – much more full reflection of Earth structure than previously (Piotrovskiy M.V. 1966). Lack of structural data, especially of latticed systems of planetary faults and presence of their non-revealed links, made geological maps of that time not quite high-grade, not allowing establishing entire systems of the tectonomorphogenesis phenomena. Morphotectonic mapping on basis of satellite images and topographic maps made by means of “rigid drawing” is proposed at present as quick efficient method, which will play important role in development of new systemic mapping. Also, one can’t but note here work of Pfilosophov V.P. “Fundamentals of morphometric method for search of tectonic structures” (Pfilosophov V.P., 1975).

As we see, everything mentioned above fully relates to the method of erosion-structural analysis, which found itself “at the cutting edge” of morphostructural, according to the method, and tectonic, according to the results, investigations. As long ago as in 1966, Piotrovskiy M.V. considered that morphotectonic mapping will enrich study of the relief and will create more accurate basis for mapping of tectonically predetermined landscapes. Plans of latticed systems of rupture disturbances, connected with them valley networks and morphological structures and their interrelation with crust and mantle levels represent real basis for programming the tasks on a computer.

Not just stated previously forecasts and suggestions about development of the science allow determining place of erosion-structural analysis and solved by it problems. In system of geologic knowledge the whole number of solved practical problems in related fields are closely connected with the field of investigation, which is of interest to us. Being involved in issues of planetary fissuring, Shults S.S. drew conclusion that with bearing of planetary fissuring many elements of the relief and hydrographic network are connected (Shults S.S. 1964). It is quite evident that use by him at that time of the erosion-structural analysis methods would allow obtaining more full information for different continents as well.

Even more acute and definite task formulated Rusanov A.B. who developed tectonic-geomorphological methods for forecasting mineral deposits. He raised issue of introduction into geologic practice and terminology of the concept of ore indicators, i.e. different objects of geologic, geomorphologic and geographic character, most frequently linear ones, which mark direction at an ore district or a deposit (Rusanov A.B., 1981). The latter, occupying right-flank position in relation to the ore indicators, are “aimed” from aside at the areas of the mineral products localization. One may consider that the material about connection of erosion systems of Pamir and adjacent territories with metallogeny is contemporary answer to previously raised issue (Khetagurova V.Sh., 2014).

It is expedient and timely to list some investigations standing on brink of using the erosion-structural analysis method. For example, Rozanov A.N., when carrying out oil exploration works, paid attention at the fact that location of ancient valleys well matched hydrographic network: “Almost all rivers have their ancient analogues – noted the author – big tectonomorphism of ancient relief…ˮ(Rozanov A.N., 1964). But anyway, he used for search of ancient valleys not developments of the erosion-structural analysis type, but expensive geophysical methods of exploration. Ananiev G.S. investigated degree of the relief dissection for the purpose of developing criteria for search of hydrothermal metallization. He noted that tectonic fissuring predetermines location of both river valleys and hydrothermal deposits (Ananiev G.S., 1973). He developed criterion of the dissection density and said that for controlling analysis of dissection one should use at the same time other methods of structural geomorphology, but they were not developed. Almost precisely the issue of connection of ore deposits with river valleys was formulated in investigations of Khripkov A.V. and Volkov E.L. in their work “Some peculiarities of valleys as geomorphological exploration criteria of ore deposits”. The authors state: “Reasons of erosion abnormalities … may be disturbances, … that’s why exploration of ore deposits should be carried out in valleys”. “The problem is formulated, possible solution is presented, but methodology of the investigation does not exist” – noted the authors (Khripkov A.V et al., 1973). In collective investigation under auspices of Favorskaya М.А. “Global regularities of big ore deposits location” (Favorskaya М.А., 1971) and in work of Volchanskaya I.K., Kochneva N.T. and Sapozhnikova E.N., in which morphostructural analysis in geologic and metallogenic investigations is considered, separate kinds of river network are presented as indicators of the structures (Volchanskaya I.K., et al.), while method of their identification, extraction and interpretation does not exist. Exist special generalizing works in which river basins are considered both from positions of the runoff and its energetics formation and in interaction with processes of relief formation (Schumm S.A., 1977). In course of the investigations high and variable information content of different river system characteristics in relation to morphostructures and contemporary tectonics was shown. However, their main shortcomings always were the theoretical base level, high subjectivity and high laboriousness of the analysis.

At the end of last century new direction has appeared – structural hydrography as section of hydrology of land – the direction was rather new, if to take into account not its origin, but period of its active development and appearance of the most significant results. Crisis of 90^th touched scientific sphere as well, and, as it was already noted, investigations in this direction were practically frozen in Russia, while at the same time abroad, where digital models of relief and computer technologies started to be widely used much earlier than in Russia, this direction successfully and actively developed. At present within the framework of structural hydrography models of new generation, oriented at solution of both fundamental and applied problems of hydrology, are developed (Chernova Y.I., 2010).

Rapid development of geoinformation technologies and remote probing facilities in recent decades caused formation of new reality stipulated by appearance of digital relief models in the form of available for all global coverage of medium scale and high quality. Due to this, almost any fragment of land becomes equally accessible for morphometric analysis with application of automated and semi-automated algorithms of transformation of high field with construction of derivative surfaces, thulwegs, search of assigned geometric images, calculation of trend surfaces, abnormalities, etc. (Gartsman B.I. et al., 2008). Digital models of relief of various scales represent special processing of the digital space survey and have important advantage – generalization and obviousness of the image of many geomorphological objects making them accessible for direct perception by a wide range of specialists. Important quality of digital models of the relief is that they, in contrast to topographic maps, contain primary information. Scanning method of data organization in digital models of relief together with obviousness provides huge advantage during computer processing. Wide introduction of digital models of relief causes appearance of qualitatively new possibilities in a whole number of sciences about Earth – geology, geomorphology, geography, hydrology, etc. (Gartsman B.I. et al., 2011). Experience of using digital models of relief in erosion-structural analysis may by next step in development of presented by us method of investigation.

So, mentioned above allows drawing conclusion that new developed by us method, called erosion-structural analysis and put into basis of investigations of Pamir and adjacent territories, the results of which are presented in this work, is called to make one step forward in solution of the problem of cognition of between forms of a relief, geologic structure and tectonics. This is the place of erosion-structural analysis among the problems connected with tectonic structure of crust and geomorphology. In addition, it may be used as auxiliary method in solution of a number of practical problems.

Conclusion

Presented above techniques and methods of the river network pattern analysis at observance of their sequence and principles will allow sufficiently confident and unambiguous singling out of certain amount of erosion systems having consistent geometric properties. As far as erosion systems are derivatives from existing systems of tectonic disturbances, this creates possibility to solve tectonic problems. Stated above allows drawing conclusion that erosion systems reflect tectonic structure of crust.

Carried out erosion-structural analysis of Pamir and adjacent territories allows drawing following main conclusions:

1. For the first time for this territory new methodology, called erosion-structural analysis and consisting of two methods – method of gradual detection and method of maps of different scale – was used.
2. On basis of the carried out analysis of the river network pattern and comparison of the detected erosions systems with tectonics the erosion-structural maps of Pamir and adjacent territories have been drawn in different scales. The erosion-structural maps, characterized by good convergence with tectonic elements taken from geologic maps of the same scale, are 3-4 times more informative, which allows solving on basis of new and obtained by independent method actual material, a number of practical problems.
3. As a result of detection of geometric regularities in structure of river networks during analysis of a vast cartographic material and generalization of data of other researchers in this field, the most representative classification of erosion systems with stepwise subordination, consisting of 48 kinds, 22 classes, 10 types, mas made.
4. For the first time erosion-structural zoning war carried out for territory of Pamir on scale 1:2 500 000. On basis of the erosion-structural analysis of Pamir, the geologic map data and data of the investigations based on different methodologies for the first time the map of erosion-structural zoning of Pamir on scale 1:2 500 000 was drawn.

The next stage of investigations on basis of the erosion-structural analysis will be carrying out of works for the purpose of demonstration of possibility of using the erosion-structural analysis data for improvement of tectonic basis of the metallogenic maps, for substantiation of the issue about its use as auxiliary method of investigations during search of mineral deposits.

In addition, it should be noted that the directions, which appeared rather long ago and were based on idea of structural, morphometric, geosystemic analysis, significantly lagged behind first of all in the issue of information-methodologic support and, as a result, in the issue of theoretic development and application value. This placed them into position of the studies, which accompanied key investigations. First decade of 21^st century principally changed the situation. Appearance of digital medium-scale global data about land surface and development of generally accessible software for their processing makes topical transition from functional to structural-functioning modelling as basic tool of hydrology of land. At present, this transition has already started and actively develops. On the other hand, developed in classic morphology concepts about energy of relief, structure of river basins and their interrelation with the newest tectonics may be checked on vast statistic material and make next step forward on basis of introduction of digital models of relief and new algorithms of their processing. No doubt, classification and mapping of the relief and all its subordinate elements should have information-energetic approach, which, certainly, will give new impetus to development of theoretic and applied basis of geomorphology and geography.

That is why in future investigations it is planned to use digital methods of relief for improvement of the erosion-structural analysis methodology. As shows analysis of the literature and own experience, development of reliable and efficient method of the river network digitization represents a complex problem, which is yet far from solution. One of the most complex problems that did not draw serious attention in publications, is possibility of transfer of the methodology and parameters of digitization, which will be calibrated on a limited territory, to the regional level and other regions.

Reference

1. Ananiev G.S., (1973). Analysis of degree of the relief dissection during search of hydrothermal metallization. (Vol. 92, pp. 132-142). Issues of geography.
2. Bazhenov M.L. and Burtman V.S. (1982). Kinematics of Pamir arc. (# 4, pp.54-65). Geotectonics.
3. Baratov R.B., Bezuglyi M.M., Ishanov M.H., Pashkov B.R. (1981). Experience of forecasting endogenic metallization in Pamir on basis of space survey materials. (# 1, pp.31-36). Investigation of Earth from space.
4. Belov А.А., Gatinsky Y.G., Mossakovskiy А.А. (1981). Indochinides of Pamir, Afghanistan and South-East Asia and significance of late Triassic epoch of folding in formation of Eurasian continent. (pp.27-31). In col.: Regularities of tectonic structure of Middle Asia. Dushanbe.
5. Belousov V.V. (1975). Quantitative assessment of Pleistocene tectonic movements of mountainous countries on example of Pamir. (# 3, pp.22-26). Geomorphology.
6. Borsuk О.А. (1974). Systemic approach to analysis of river systems. (pp. 107-113). Issues of geography, col. 93. М.: Science.
7. Chernova Y.I., Nugmanova I.I., Dautov А.N. (2010). Use of GOS analytic functions for improvement and development of structural-geomorphologic methods of neotectonics study. (# 4, pp. 9–22). Geoinformatics.
8. Favorskaya М.А. (1971). Global regularities of location of big ore deposits. (# 11, pp. 19-26). Sov. Geology.
9. Gartsman B.I., Bugayets А. N., Tegai N. D., Krasnopeyev S. М. (2008). Analysis of river system structures and prospects of hydrologic process modeling. (# 2, pp. 116–123). Geography and natural resources.
10. Gartsman B.I., Galanin А.А. (2011). Structural-hydrographic and morphometric analysis of river systems: theoretic aspects. (# 3, pp. 27-37). Geography and natural resources.
11. Karasyov М.S. Khudiakov G.I (1984). River systems (on axample of Far East). (p. 143). М.: Nauka.
12. Khetagurova V.Sh. (2014). Erosion-structural analysis as auxiliary method during search of mineral deposits. (pp. 629-634). Theoretical and practical investigations of XXI century. Works of international scientific-practical conference. М.: IPD MSOU.
13. Khetagurova V.S., Umaraliev R.A., Bryukhanova G.A. (2015). The use of erosion-structural analysis on the example of mountainous territory. (pp. 35-39). The First European Conference on Earth Sciences. Proceedings of the Congress (February 25, 2015). “East Westˮ Association for Advanced Studies and Higher Education GmbH. Vienna.
14. Khripkov A.V., Volkov Е.L. (1973). Some peculiarities of valleys as geomorphologic exploration signs of ore deposits. (pp. 18-28). Publ. of Dnepropetrovsk Geogr. Society of Ukraine.
15. Korytnyi L.M (2001). Basin concept in environmental management. (p. 163). Irkutsk: Issue of Institute of geography of SD RAS.
16. Korytnyi L.M. Bezrukov L.А. (1990). Water resources of Angara-Yenisei region. (pp. 214). Novosibirsk: Nauka.
17. Kukhtikov M.M. (1981). On thrust blocks of Pamir (To the issue of priority of horizontal or vertical tectonic movements). (V.56, issue.1, pp.3-15). Bull. MSNT, dep. Geol.
18. Pashkov B.R., Shvolman V.А. (1979). Rift outskirts of Tethys on Pamir. (# 6, pp.58-70). Geotectonics.
19. Pfilosophov V.P.(1975). Fundamentals of morphometric methods of tectonic structures search. (pp. 232). Saratov: Publ. of Saratove University.
20. Piotrovskiy M.V (1966). Some regularities of arch-block morphotectonics. In book: Problems of neotectonic movements and newest structures of crust. (pp. 248). М.: Nauka.
21. Rozanov A.N. (1964). On geologic nature of photon on space images. (# 1, pp. 100-106). Soviet geology.
22. Rusanov А.B. (1981). Geomorphologic methods of ore field structure detection. – In collection: Works of NCMMI, Ordzhonikidze, 1981, pp.10-11.
23. Ruzhentsev S.V., Shvolman V.A., Pashkov B.R., Pospelov I.I. (1983). Tectonic development of Pamir-Himalayas sector of Alpine fold belt. (pp.167-175). In col.: Tectonics of Tien-Shan and Pamir. М.: Nauka.
24. Schumm S.A. (1977). The Fluvial System. (pp. 338). New York: John Wiley and Sons.
25. Shults S.S. (1964). Geo-structural areas and position in structure of Earth of orogeny areas according to the newest tectonics data of the USSR. – In book: Activated zones of crust, newest tectonic movements and seismicity. (p.47). М.: Nauka.
26. Shvolman V.А. (1977). Tectonic development of Pamir in Cretaceous and Paleogene periods. (p.176). М.: Nauka.
27. Sladkopevtsev S.A. (1973). Development of river valleys and neotectonics. (p. 132). М.: Nedra.
28. Suvorov А.I. (1963). Faults and horizontal movement of crust. (pp.173-237). М.: Publ. AS USSR.
29. Volchanskaya I.K., Kochneva N.T. and Sapozhnikova E.N (1975). Morphostructural analysis in geologic and metallogenic investigations. (p. 211). М.: Science.
30. Zonenshine L.P. (1990). Tectonics of lithospheric plates. (pp.184-185). Bk.2. М.: Nedra.