Preglacial Geomorphology of the Northern Baltic Lowland and the Valdai Hills, North-Western Russia
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Bulletin of the Geological Society of Finland, Vol. 84, 2012, pp 58–68 Preglacial geomorphology of the northern Baltic Lowland and the Valdai Hills, north-western Russia A.Y. KROTOVA-PUTINTSEVA AND V.R. VERBITSKIY A. P. Karpinsky Russian Geological Research Institute (VSEGEI), Sredny pr. 74, 199106 Saint-Petersburg, Russia Abstract The aim of the ongoing investigation is to reconstruct the development history of preglacial (including deeply-incised) river network of the northwestern East European Platform during the Cenozoic. This paper describes the orography of the region. The results of studying the structure of modern and preglacial (pre-Quaternary) geomorphology are given. This synthesis is based on the geological information that has been acquired as a result of systematic state geological surveying and scientific investigations and also on the analysis of published materials for the study area. The hypsometric map of the pre-Quaternary surface is presented. Generalization of the above mentioned materials on a unified basis and at regional level allowed a new reconstruction of the preglacial river network in the Ilmen Lowland area, drainage from which to our opinion was to the west. Analysis of the preglacial and modern topography correlation shows that the latter, in general, is inherited. This leads to the conclusion on a quiet tectonic regime in the study area at least since the Mesozoic. Therefore, the question on the causes of deeply incised valleys requires further study. Keywords (GeoRef Thesaurus, AGI): geomorphology, topography, paleorelief, preglacial environment, drainage patterns, rivers, Cenozoic, Novgorod Region, Russian Federation Corresponding author email: [email protected] Editorial handling: Pertti Sarala 1. Introduction During the Pre-Quaternary (preglacial) time, the interglacial deposits. Until now, there is no agree- north-western part of the East European Plain was ment on the formation time, initiation, and the exact drained by erosional channels, some of them below location of the paleovalleys because, due to a long the sea level. Later, these paleovalleys were comple- period of denudation since the Middle Mesozoic tely or partially filled with glacial, aqueoglacial, and (for the entire territory), traces of the bygone geo- Bulletin_vol84_1_2012.pmd 59 25.6.2012, 18:22 60 A.Y. Krotova-Putintseva and V.R. Verbitskiy logical epoch are lost or veiled. The main goal of dinates, altitude of the mouth, depth and sediment the ongoing research is to reconstruct the evolution characteristics, general and regional age. This data- of the drainage system of the north-western part of base was used during compilation of hypsometric the East European Platform during the Cenozoic map of the pre-Quaternary sediments surface with based on the geological structure of the territory. 25 m interval isolines. Existing schemes of the pre- Reconstruction of the ancient river network should Quaternary surface structure from the above men- involve a unified and regional approach to the net- tioned and published resources were considered work formation history. during compilation of this map and the preglacial This paper presents the results of studying the river network reconstruction (Malakhovsky & Mar- structure of the modern and pre-Quaternary topo- kov, 1969; Kvasov, 1975; Gibbard, 1988; Grigelis, graphy. Investigations were held in the framework 1991; Auslender, 1998; Vaher et al. 2010). of compilation of the State Geological Map at In process of research, the schemes of geomor- 1:1 000 000 scale (third generation), sheets 0-35 – phology, geomorphologic districts, glaciations, and Pskov (with N-35 part) and 0-36 – Saint Peters- glacial lakes were created. Publications of Markov burg. Works on compilation of the State Geologi- & Malakhovskiy (1969), Kvasov (1975), Goretskiy cal Map at 1:1 000 000 scale (third generation) were et al. (1982) etc., as well as the Quaternary geologi- started in 2002. Total number of sheets to be com- cal map of the study area (authors V. Kyamyarya piled in the framework of this program is 246, in- and V. Mokhov) were utilized. cluding land and continental shelf of the Russian Federation (Petrov et al., 2007). 4. Modern topography 2. Study area 4.1. Orography The study area is located in north-western Russia The study area is situated in the north-west part of within the East European Platform. It occupies the the Russian Plain. Sedimentary rocks have subho- north-western part of the Russian Plate, and bor- rizontal bedding and tectonic movements (if such ders on the southern edge of the Fennoscandian exist) are characterized by moderate amplitude that Crystalline Shield. Western part of the area belongs is commensurable with exogenic processes (Malak- to the Baltic Lowland, and the eastern part to the hovskiy, 1995). This causes flat topography charac- Valdai Hills that are 100 m to 346 m high (Fig. 1). ter. Major orographic elements of the Russian Plain 3. Materials and methods are the Baltic Lowland and the Valdai Hills (maxi- mum height is 346 m) (Fig. 1). The Baltic Lowland Principle of the State Geological Map compilation is a gently sloping to the north undulating plain, at 1:1 000 000 scale (third generation) requires crossed by a dense network of rivers, with isolated integration of the State Geological Maps at highlands up to 200–338 m high. Along the sout- 1:200 000 scale (first and second generation) and hern coast of the Gulf of Finland, the Neva River at 1:1 000 000 scale (second generation) (Petrov et and the southern shore of Lake Ladoga, there is a al., 2007; Burde et al., 2000). Therefore, all narrow strip of pre-glint or maritime part of the published sets of geological maps at 1:200 000 scale, Baltic Lowland with surface elevation from 15 to as well as a map at 1:1 000 000 scale (second 30 m. The flat lowland topography is in some pla- generation) for the study area and adjacent territories ces complicated by small island elevations (Koltus- were used (Kirikov & Yanovskiy 1989). hy – 80 m, Vsevolozhsk – 50 m, Semeisky – 96 m, A database containing description of 2 436 geo- Soikinsky – 137 m). The pre-glint lowland is boun- logical and hydrogeological boreholes was created. ded by the Baltic-Ladoga scarp or the Ordovician The database includes the borehole’s number, coor- glint from the south. The glint is well expressed in Bulletin_vol84_1_2012.pmd 60 25.6.2012, 18:22 Preglacial geomorphology of the northern Baltic Lowland and the Valdai Hills, north-western Russia 61 Fig. 1. Scheme of orography (compiled by Krotova-Putintseva A.Y.) the topography and extends from the Syas River to The Valdai Hills are separated from the Baltic the Narva River. It is composed of the Ordovician Lowland by Valdai-Onega (Carboniferous) scarp limestones and rises above the pre-glint lowland at with relative heights of 25–125 m, which extends 5–40 m; the absolute height of its upper edge reaches from the southern shore of Lake Onega (outside 100–120 m (Koporie village – Krasnoye Selo). the study area) to the headwaters of the Lovat Ri- South of glint, there are Izhora Highland and ver. The Valdai Hills consist of individual ridges and Volkhov Plateau from 25 to 168 m high. In the their massifs (Tikhvin, Ostashkov, Vyshnevolotsky western and central parts of the study area, an ridges, Toropets, Sherekhovichi heights, Vorobyovy, alternation of extensive lowlands (Volkhov-Lovat or Revenitsy, Svinie and Ilyi mountains, Okovsky Ilmen, Pskov-Chudskaya) with absolute heights Forest hills) and depressions among them. At from 20 to 120 m and isolated highlands of contrast Vyshnevolotsky ridge, in the interfluvial area of the hummocky-lacustrine morphology, rising above the Tsna (river Msta Basin) and Poved (river Tvertsa surrounding area at 100–220 m (Luga, Haanja, Basin) rivers near Repishche village, the highest Sudoma, and Bezhanitsy) is observed. point of the Valdai Hills and the whole study area, Bulletin_vol84_1_2012.pmd 61 25.6.2012, 18:22 62 A.Y. Krotova-Putintseva and V.R. Verbitskiy 346 m a.s.l., is situated. Southward and southeast- (major ice-marginal zone), (3) and distal (outer) ward, topography of the Valdai Hills gradually (Kirikov & Yanovskiy, 1989). flattens and is replaced by plains in the Tvertsa, The proximal zone occupies the largest part of Mologa, and Volga river basins. Lower parts of this the area. In the east, it is bordered by the major ice- plain known as the Volga-Shoshino, Middle Mologa, marginal belt, which is located on the western edge and Mologa-Sheksna lowlands with elevations of and at the foot of the Valdai Hills. This zone is cha- 125–170 m a.s.l. Areas of hummocky glacial relief racterized by widely spread till and glaciolacustrine are also present (Tver, Likhoslavl, Torzhok, Lesnoy plains developed in the course of degradation of the ridges etc.). Late Valdaian glacier and inflow of large amounts The territory has an extensive river network. of meltwaters hampered up by the dam of the ma- The Valdai Hills form the watershed between jor ice-marginal belt. Accumulative hummocky and catchment basins of the Baltic (Neva, Volkhov, Luga, hummocky-ridged glacial and aqueoglacial relief is Narva, Velikaya, Shelon, Lovat, Msta, and Western represented by both in the form of large interlobate Dvina rivers) and Caspian (Volga, Mologa, and highlands and small ridges and massifs. Three geo- Chagoda) seas. There are numerous lakes varied in morphological regions with a specific outlook of size, shape, and origin in the study area. The largest both modern and ancient topography are distin- of them are Ladoga, Chudskoye, Pskov, Ilmen. A guished within the proximal zone: Baltic-Ladoga large number of medium and small lakes is con- (accumulative and abrasion plains and isolated ac- centrated in the Lake District of the Valdai Hills cumulative highlands), Volkhov-Lovat (denudation (Lakes Seliger, Shlino, Piros), as well as on island plateau, abrasion-accumulative plains with linear highlands of the Baltic Lowland (Lake Zhizhitskoe accumulative formations), and Izhora-Bezhanitsy etc.).