ISSN 01458752, Moscow University Geology Bulletin, 2014, Vol. 69, No. 1, pp. 11–16. © Allerton Press, Inc., 2014. Original Russian Text © L.V. Panina, V.A. Zaitsev, 2014, published in Vestnik Moskovskogo Universiteta. Geologiya, 2014, No. 1, pp. 17–23.

The Recent Tectonics of the Caspian Sea Region L. V. Panina and V. A. Zaitsev Department of Geology, Moscow State University, Moscow, Russia email: [email protected] Received May 28, 2013

Abstract—Recent uplifts and depressions complicated by lineaments, many of which are faults, were found within the Caspian depression using complex structural and geomorphological studies, which included visual interpretation of differentscale topographic maps, as well as an analysis and computer processing of radar satellite images. In many respects, the latest dislocations correlate with the structures and sedimentary cover of the basement and are also determined by salt tectonics. Their formation is substantially influenced by the Ural Orogen and the Scythian plate is involved in the entire uplift at the latest stage.

Keywords: recent tectonics, structural and geomorphological analysis, radar image, lineament, fault DOI: 10.3103/S0145875214010074

INTRODUCTION most elevated structure (with occurrence depths down to –8 km) in the tectonic map of the basement (Inter The Caspian depression, which is located in the national map…, 2003) is the Astrakhan–Aktyubinsk southeast of the Russian plate, is part of the entire system of block uplifts, which is confined to the Cas Caspian megadepression, which also includes the pian Sea and further extends along the eastern periph depressions in the Middle and Southern Caspian. Tec ery of the Caspian depression. The most subsided por tonically it corresponds to the East European platform tions are the Central Caspian depression and the syneclise of the same name, which is the structure with Sarpin downwarp with basement occurrence depths the most subsided basement. The area under study down to –22 km. The thick sedimentary cover formed covers the Caspian Sea region that is traditionally during the long–term downwarping of the Caspian called the Caspian lowland; it underwent negative Sea region consists of the presalt Paleozoic–Early movements during the entire Phanerozoic. Its recent Permian, saliferous Kungurian and abovesalt Upper relief is a poorly broken plain with the dominant abso Permian–Cainozoic complexes. These rocks form lute marks of <100 m down to negative values of –28 m rootless folds complicated by diapirs and ruptures that increasing to the eastern periphery to 200 m and frequently inherit the basement faults. greater in the area of the Underural plateau. In the The recent structure of the Caspian depression has north and northwest, the boundary structures are the been studied by many scientists, including I.P. Gerasi recent uplifts that develop on the slopes of the Volga– mov, Yu.A. Meshcheryakov, V.S. Zhuravlev, and Ural and Voronezh anticlises, in the west and southwest L.B. Aristarkhova. Many dislocations of the Caspian they are the structures of the Scythian plate, such as the Sea region are not shown at the 1 : 5000000scale neo Yergeninskoye uplift and the zone of subsidence of the tectonic maps edited by N.I. Nikolayev and Karpinsky ridge, and in the northwest, the near Volga A.A. Naimark (1979), and by A.F. Grachev (1998) due uplift. The northeastern margin is the Obshchiy Syrt to their small scale. The latest geological–geophysical uplift, and the eastern one is the structures of the pied data and the materials of the satellite images, in partic mont downwarp of the Ural Mountains. In the south, ular, radar images, and the procedures of their pro the lowland is bounded by the Caspian Sea depression. cessing, created a necessity for new studies that would According to the recent studies, the occurrence substantially expand the concept of the regional tec depth of the basement in the Caspian depression tonics. The purpose of this work is to study the recent reaches 22 km and the basement itself is a series of tectonics of the Caspian depression using the latest blocks of continental crust that were consolidated at materials and procedures for their processing. different times and separated by the zones of long Procedures of studies. It is always difficult to carry existing faults (Astrakhanskii…, 2008). The Archean– out a structural and geomorphological analysis under Proterozoic, the oldest age of the basement, is identi conditions of flat and poorly broken relief. Developing fied for the Central–Caspian block; southward within structures are traditionally discovered by indirect geo the Eastern Caspian geoblock the basement is morphological features, such as contouring of uplifts younger, viz., the Late Proterozoic–Riphean. The by river valleys and erosion depressions, a typical radi

11 12 PANINA, ZAITSEV ally divergent pattern of a hydrographic network, a Ink submontane trough in the east, which is developed change in the slopes and elevations of a relief, a reduc by the valley of the Ink river. Located in the east, the tion in lake areas, etc., which are not always shown in Orenburg uplift (12) is confined by the Sakmara and the topographic maps and ordinary spectrozonal satel Ural nearfault troughs in the north and south, respec lite images. The use of radar images significantly tively (Naumov, 1981). Partial dislocations are identi expands the possibilities for interpreting a flat relief. fied within these first rank structures, which tend to The Global Mapper software makes it possible to rise in general. identify an erosion network via radar images; when The Caspian depression itself is also complicated generalized, it provides a better view of the structures by uplifts of different ranks and amplitudes. Among that are weakly reflected in the relief. Therefore, the them there are highamplitude uplifts with the abso structural and geomorphological interpretation of the lute marks of 100–250 m; lowamplitude uplifts, topographic maps and Landsat7 spectrozonal satellite whose relief altitudes are no more than 100 m, as well images is supplemented by a visual analysis of detailed as buried uplifts that are not reflected in the relief. The radar images that allow detection of buried structures highamplitude uplifts are confined to the northern in the areas that have negative values of the relief’s and eastern peripheries of the Caspian depression. As absolute marks. This especially concerns the central a rule, they are structures that are somewhat elongated part of the Caspian depression, which has been sub in the sublateral and submeridional directions, are jected to substantial downwarping in the latest period separated by narrow valleylike troughs, and corre from the Oligocene until recently. spond to the relatively elevated zones of the basement: the Astrakhan–Aktyubinsk system of uplifts and the ASTER GDEM radar images were also automati TransVolga PreUral fault zone in the east and south cally processed by the LESSA and Global Mapper east, respectively, as well as the northwestern flank in software. The LESSA software, which was developed the north. The occurrence depth of the basement roof by A.A. Zlatopolskii (Zlatopolskii, 1998), automati ranges here from –4 to –10 km. It is important to indi cally detects watersheds and valleys as socalled dashes cate the increase in the contours of the recent uplifts as and calculates their statistical characteristics in a slid compared to the structures of the basement of the ing window. As well, it can determine the general den same name (Ashchikolskoye, Enbekskoye, and sity of dashes, the density of dashes of different direc Karaulkel’dinskoye). tions, create rose diagrams of the distribution of Lowamplitude (up to 100 m) and buried uplifts are dashes by their directions, and obtain the degree and confined to the central western and southern parts of direction of the elongation of rose diagrams and other the Caspian depression (Fig. 1). A few of them, viz., parameters. A pattern of lines of elongation in the rose Munailinskoye (44) and Opornoye (45), are located in diagrams was constructed for the relief elements with the southeast. The uplifts, as a rule, have an isometric an averaging window of 135 km, which was further shape that may be determined by salt diaperism. compared to the results of the structural and geomor Among them there are the Chkalovskoye (47), Yustin phological interpretation and dislocations of deep skoye (49), Oktyabrskoye (52), Bulukhtinskoye (53), structural plans, mainly of the basement surface. The and Eltonskoye (54), which develop on the western data that were obtained as a result of such complex and northwestern Caspian slopes, and the structural and geomorphological studies were com Yulayevskoye (61), Shalkarskoye (62), and Buldyrtin pared to the geological and geophysical materials. skoye (63), which are confined to the central part of Recent tectonics. The structural and geomorpho the depression. logical studies showed that the Caspian depression The Azhbaiskoye (56), Taldykudukskoye (57), bounds a series of the recent first rank uplifts with an Satybaldukskoye (58), Kozhantaiskoye (59), Mokrin amplitude ranging from 150 to 400 m (Fig. 1). Some of skoye (60), and other uplifts are developed within the them develop on the young Scythian and Turanian Central Caspian depression, which is the most sub plates (Yergeninskoye, Donyztausskoye, Turushskoye, sided with respect to the basement (down to –22 km) et al.); the others develop on the slopes of the Voron and are inversion structures. The radar images in the ezh and VolgoUral anticlises of the ancient East south of the Caspian depression revealed a series of European platform (nearVolga, Mokrousskoye, Pere buried uplifts, which in general correspond to the lyubskoye, Sorochinskoye, Nazykskoye, and Oren uplifts of the Astrakhan–Aktyubinsk system base burgskoye) and some form a system of uplifts within ment. The buried uplifts located there, viz., Astra the PreUral foredeep (Chebogarovskoye, Kuvandyk khanskoye (73), Northern Caspian (74), and skoye, and Poltavskoye). These uplifts are separated Sagizskoye (75), indicate positive structures of the base from each other by the narrow troughs to which the ment in the relief that lie at depths of –7.5 to –8 km. valleys of the large rivers are confined. For example, in They are bounded by salt diapirs. 1 the northeast, the Nazykskoye uplift (13) borders the We also interpreted the lineaments, which are con sidered to have a tectonic origin in most cases. The 1 In what follows the bracketed numbers correspond to those in dominant ones are lineaments of northwestern, north Figure 1. eastern, and submeridional strike. The latter tend

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 69 No. 1 2014 THE RECENT TECTONICS OF THE CASPIAN SEA REGION 13

45°0′0″ E 47°30′0″ E 50°0′0″ E 52°30′0″ E 55°0′0″ E 57°30′0″ E

77 N 13 7 10 14 18 12 17 5 8 9 15 33 16 4 6 31 19 32 34 30 50°0′0″ N 3 62 57 61 63 35 36 71 2 56 55 58 64 65 59 20 53 39 38 54 60 52 66 37 40 22 70 72 67 69 51 23 ° ′ ″ 41 47 30 0 N 76 75 42 50 68

74 1 44 25 47 49 73 27 26 48 CASPIAN SEA 45 29 28

km 0 50 100 200 300 400 12345678

Fig. 1. The structural and geomorphological pattern and margins of the Caspian depression: 1 boundaries of the firstrank struc tures: 2–5 recent uplifts: 2 of the first rank, 3 highamplitude, 4 lowamplitude, 5 buried; 6 recent faults; 7 lineaments coinciding with the basement faults; 8 lineaments. The recent uplifts are designated by numbers: the structures of the Caspian depression mar gins: the first rank margins: on the west: 1 Yergeninskoye, 2 near Volga; on the northwest: 3 Dono–Medveditskoye, 4 Rtishchev skoye, 5 Saratovskoye, 6 Mokrousskoye, 77 Kamenskoye; on the north 7 Syrtovskoye, 8 Perelyubskoye, 9 Rostashinskoye, 10 Sorochinskoye, 12 Orenburgskoye, 13 Nazykskoye; on the northeast and east: PreUral foredeep region: 14 Chebogarovskoye, 15 Kuvandykskoye, 16 Poltavskoye; the region of the southern tip of the Urals: 17 Novotroitskoye, 18 Irendykskoye, 19 Alimbe tovskoye; Primugodzharskii slope of the Turanian plate: 20 Kumzharganskoye, 22 Dzhurunskoye; on the southeast: 23 Shoshka kol’skoye; 25 Aktumsyk, 26 Donyztausskoye, 27 Zheltausskoye, 28 Turushskoye, 29 Korkol’skoye. Uplifts bounding the Caspian depression: the northern slope: 30 Akhmatovskoye, 31 Ozinkinskoye, 32 Dolinnoye, 33 Pervo maiskoye: the eastern slope: 34 Novomikhailovskoye, 35 Ashchikol’skoye, 36 Akshatausskoye, 37 Yenbekskoye, 38 Karaulkel’din skoye, 39 Sorkol’skoye, 40 Koskol’skoye; the southeastern slope: 41 Aktolagal’skoye; 42 Zharkamysskoye, 44 Munailinskoye, 45 Opornoye; the western and northwestern slope: 47 Chkalovskoye, 48 Krasnopeschanoye, 49 Yustinskoye, 50 Dzhangarskoye, 51 Turgaiskoye, 52 Oktyabr’skoye, 53 Bulukhtinskoye, 54 El’tonskoye, 55 Dzhanybekskoye, 71 Inderskoye; the central part: 56 Azhbaiskoye, 57 Taldykuldukskoye, 58 Satybaldykskoye, 59 Kozhantaiskoye, 60 Mokrinskoye, 61 Yulayevskoye, 62 Shalkarkoye, 63 Buldyrtinskoye, 64 Kaldygaitinskoye, 65 Kamyskol’skoye, 66 Aralsorskoye, 67 Akkolskoye, 68 Azgirskoye, 69 Kusainskoye, 70 Eleusinskoye, 72 Karabau, 73 Astrakhanskoye, 74 Northern Caspian, 75 Sagizskoye, 76 Baksaiskoye. towards the Eastern Caspian, the socalled Subural researchers: Azgirskii, Zholdybaiskii, and Embenskii, plateau. The sublatitudinal lineaments occur compar et al. (Geologiya SSSR..., 1970). atively less frequently, as they occur in the southern The comparison of the recent structures and the and central parts of the depression. In the east, the deep dislocations indicate that they correlate quite submeridional lineaments are dominant. Some of well. This is especially seen in the correlation of the them fragmentarily inherit the basement faults and are salt diapirs, which are well developed in the Caspian recent faults that were discovered by previous Sea region. The areas of saltdome tectonics are often

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 69 No. 1 2014 14 PANINA, ZAITSEV reflected in the relief by the recent uplifts and some periphery of the Caspian depression. All the orienta diapirs mark extended lineaments and recent faults. tions of the lineaments are shown by the strikes of the The salt domes point to the recent Azgirskii rupture, deep faults; this is submeridional in the east, north which strikes in a westnorthwest direction in the western in the southwest and northwest, sublatitudinal south of the Caspian depression, as well as many in the central part, and northeastern in the west and northwestern lineaments that partially coincide with northeast. Some extended lineaments fragmentarily the recent ruptures. The salt domes are also confined coincide with the zones of the basement faults to the system of the extended sublatitutdinal linea recorded by the geophysical methods and serve as the ments in the central part of the Caspian Sea region. We boundaries of the large structural units. For example, note that this system fragmentarily inherits the deep the northern border of the Caspian depression with the fault of the basement. The northeastern lineaments are East European platform goes along the lineament of also marked by salt domes, especially in the east of the the eastnortheastern strike. The relief southward and region. parallel to it reflects a basement fault that separates a There is a connection between the salt diapirs and steep northern slope of the Caspian depression from the recent uplifts. Almost all highamplitude recent the more subsided Volgograd–Orenburg system of uplifts in the eastern periphery of the Caspian Sea monoclines. The relief also exhibits a fault of north region are located in the area of the development of western strike that separates the Caspian depression saltdome tectonics. Some of them partially inherit from the Karpinsky ridge in the southwest. An positive structures of the basement, for example, Ash extended lineament along the section of the Volga river chikol’skoye, Enbekskoye, Karaulkel’dinskoye, and is recorded towards the northeast and in parallel to it. Koskol’skoye. The lowamplitude uplifts in the cen Its fragment is also inherited from the basement. tral part of the Caspian Sea region are directly related The river valleys have developed submeridional to the manifestation of diapirism. They are inversion faults of the basement that separate the Caspian structures with respect to the basement. Among them depression from the PreUral foredeep and there are the Shalkarskoye, Yulayevskoye, Inderskoye, Primugodzharskii slope of the Turanian plate in the Sagizskoye, and Eltonskoye (Fig. 1). east. Some of the recorded uplifts are shown in the struc The results of the computer processing of radar tural maps of deep horizons of Paleozoic complexes images using the LESSA software also showed a good (Upper Devonian, Visean, and Bashkirian) at depths correlation with the data of visual interpretation. of –5 to –6 km and correlate well with the basement Many uplifts of the relief are underlined by elongated structures. The good correlation of the recent disloca lines that either contour them or have a radially diver tions with the older structures, namely with the Devo gent pattern. These features are used to reveal low nian complex, is observed within the northern part of amplitude and buried structures that are not easily rec the Caspian depression. Located in the north, the ognized in the ordinary topographic maps and images recent Dolinnoye uplift (32) inherits the positive (Manuilinskoye, Astrakhanskoye, Northern Caspian, structural surface elements of the following Devonian etc.) The lines of elongation also go along the deposits: the Karpov structural nose, the Iletskii ridge, extended lineaments and the change in the strike may and the Ural–Koblandin uplift zone. indicate the occurrence of a lineament. The relationships between the recent uplifts and There is also a good correlation between the lines of the basements are different. As a rule, there is a trend elongation and structural elements of the foundation, to the expansion of the contours of the recent uplifts as isohypses, and faults. The lines of elongation often go compared to the basement structures. For example, along the basement isohypses and sharply change their the recent Sorochinskoye uplift, which bounds the strikes in the fault zones. In the basement maps, for Caspian depression on the north, inherits the East example, in the International tectonic map (2003) it is Orenburg structural basement bench in the northern clearly seen that the lines of elongation change their part, while in the south it is an inversion structure with strikes in the zones of basement faults or are oriented respect to the Buzuluk trough. A similar picture is seen along them (Fig. 2). The largest structures of the base in the east of the Caspian Sea region, where the Ash ment, such as the Karpinsky ridge, which bounds the chikol’skoye, Karaulkel’dinskoye, and Koskol’skoye Caspian depression in the southwest, are underlined uplifts, which are reflected in the relief with the abso by northwesttrending lines of elongation. These lines lute marks of 325–100 m, show the positive basement exhibit the extended basement faults striking north structures of the same name located at the 7–8 km west that intersect the depression in the northwest, in negative marks only in the central parts. A good corre the boundary region with the ancient Pachelmsky aul lation with the basement is traced in the south, where acogen. One of them is a fault that coincides with a the Astrakhanskoye and Northern Caspian buried section of the Volga river. The lines of elongation have uplifts directly reflect the basement dislocations of the a radially divergent pattern within the Astrakhanskii same name. arch, the largest Caspian structure, thus underlining it Some of the lineaments partially correspond to the (Panina and Zaitsev, 2011). The shape of the elongation basement faults. This is especially well seen at the lines represents the Northern Caspian, Karaulkel’din

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 69 No. 1 2014 THE RECENT TECTONICS OF THE CASPIAN SEA REGION 15

45°0′0″ E 47°30′0″ E 50°0′0″ E 52°30′0″ E 55°0′0″ E 57°30′0″ E N

50°0′0″ N

47°30′0″ N

CASPIAN SEA

km 0 50 100 200 300 400

12 3

Fig. 2. The correlation pattern for the lines of elongation of the rose diagrams and the basement faults: 1 the boundaries of the firstrank structures, 2 the basement faults, 3 the lines of elongation of the rose diagrams. sky, and other uplifts of the basement. The sudden blocks. The highamplitude uplifts are confined to the changes in the strike of the lines of elongation in the eastern periphery of the Caspian Sea region and the central part of the Caspian depression are confined to lowamplitude and buried positive structures are the zone of the sublateral fault that separates the Cen developed in the central region that underwent long tral Caspian downwarp of the basement from the subsidence. Northern Atyraus system of monoclines located towards the south. The growth of these uplifts is accompanied by the formation of lineaments, many of which are faults, Comparison to the gravitational and magnetic fracture zones, and zones of rock shattering, etc. that fields showed that a few extended lineaments or their are recognized badly in the relief, i.e., they have a tec fragments are reflected in the magnetic and gravita tonic origin. The lineaments strike dominantly north tional anomalies. west, northeast, and submeridionally (mainly in the east). The northwestern lineaments are developed in CONCLUSIONS the south, northwest, and the west of the region. The sublatitudinal lineaments that are confined mainly to Here, the recent structure of the Caspian Sea the central part of the depression occur comparatively region was determined by many methods. In general, less frequently. The most extended of them inherit the the Caspian lowland, which has a direct relationship basement faults and are partially reflected in the grav with the basement relief, is complicated by partial ity and magnetic anomalies. uplifts of different ranks and amplitudes that develop against the background of salt diapirism, which, as a The recently discovered structures correlate differ rule, is caused by tectonic movements of the basement ently with the deep dislocations. As a rule, the surface

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 69 No. 1 2014 16 PANINA, ZAITSEV structures partially inherit the ancient complexes. An Mezhdunarodnaya tektonicheskaya karta Kaspiiskogo morya especially good correlation is recorded in the periph i ego obramleniya, masshtab 1 : 2500000 (International eral parts, in the areas of the junction with the Ural Tectonic Map of the Caspian Sea and its Framework. orogen and the Scythian plate. There is a typical ten Scale 1 : 25000000), Khain, V.E. and Bogdanov, N.A., dency for the recent uplifts to extend as compared to Eds., Moscow: Inst. Litosf. Okrain. Vnutren. Morei, the deep dislocations. 2003 [in Russian]. Naumov, A.D., Penepleny. Ikh Geologicheskoe znachenie The recent structures of the Caspian depression kak osoboi geneticheskoi kategorii rel’efa materikov were formed under the influence of the basement (Peneplains. Their Geological Significance as a Spe strains and activated bounding structures of the Ural cific Genetic Type of the Continental Relief), Saratov: orogen and the Scythian plate. The activation of these Izd. SGU, 1981 [in Russian]. large systems started in the late Miocene (pre Panina, L.V., Modern structural pattern of the Scythian Pliocene phase) and led to the formation of the latest Plate, Vestn. Mosk. Univ., Ser. 4: Geol., 2009, no. 1, structural plan of the Caspian Sea region. This is espe pp. 23–31. cially typical of the eastern periphery, where the Panina, L.V. and Zaitsev, V.A., The relief of northern Cas depression borders the PreUral foredeep and its pian Sea Region as a reflection of deformation in the southern continuation. The highamplitude uplifts, basement, in Teoreticheskie Problemy sovremennoi geo which have been steadily developing since the morfologii. teoriya i praktika izucheniya geomorfolog Miocene, are located exactly there. The Scythian plate, icheskikh sistem: Mat. XXXI Plenuma Geomorfol. Kom. especially its main structure, the Karpinsky ridge, which RAN 5–9 oktyabrya 2011 g. (Proc. XXXI Plenary Secc. was drawn in the uplift in the late Miocene and is Geomorphol. Com.“Theoretical Problems of Modern developing under the action of the Caucasian orogen, Geomorphology. Theory and Practice in Study of Geo influences the development of the Caspian Sea region morphologic Systems”. October 5–9, 2011), Astra (Panina, 2009; Zaitsev and Panina, 2011). khan’: Tekhnograd, 2011, pp. 41–45. Zaitsev, V.A. and Panina, L.V., Neotectonics and geody namics of the Scythian Plate, Vestn. Mosk. Univ., Ser. 4: REFERENCES Geol., 2011, no, 1, pp. 3–7. Astrakhanskii karbonatnyi massiv: stroenie i neftegazonos Zlatopol’skii, A.A., Software package of applied programs nost’ (The Astrakhan Carbonate Massif: Structure and for selection and analysis of linear elements on aero OilandGas Potential), Volozh, Yu.A. and space images, in Avtomatizirovannyi lineamentnyi analiz Parasyna, V.S., Eds., Moscow: Nauchnyi mir, 2008 (in pri strukturnogeologicheskikh i metallogenicheskikh Russian). issledovaniya (Automated Lineament Analysis at Struc turalGeological and Metallogenic Research), Mos Geologiya SSSR. T. XXI. Zapadnyi Kazakhstan. Ch. 1. Geo cow: Nedra, 1988, pp. 14–28. logicheskoe opisanie. Kn. 2 (Geology of the USSR. Vol. XXI. Western Kazakhstan. Part 1. Geological Description. Book 2), Moscow: Nedra, 1970 [in Russian]. Translated by L. Mukhortova

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 69 No. 1 2014