H. Achyuthan

Several terms have been used to understand the formation of highly indurated calcretes, such as hardpan, Stage VI calcretes and hardpan calcretes. In this paper, calcretes formed over the parent rock with distinct contact and underlying the aeolian/fluvial sediments have been termed as hardpan calcretes with no genetic connotations. They are important lithological units as they are forming a distinct element of the Quaternary landscape. These calcretes remain undated due to the paucity of dateable material and unsuitable dating methods. The purpose of this study is to determine the processes governing the development of hardpan calcretes and evaluate the local and regional controls on their formation.

The study area is located within the Nagaur-Churu-Jaipur tract. Hardpan calcretes have been mapped for their spatial extent and thickness over the bedrock both, in the field and using bore hole lithologs. They are nearly a meter thick formed over the bedrock with a sharp contact. Hardpan calcretes consists of 0.3 to 0.5 mm thick laminated carbonate zones forming rims around the detrital grains and nodules of calcium carbonate and siderite. They are distinct from the calcretes in aeolian dunes in being formed directly upon Precambrian bedrock and beneath 1 to 1.5 m of unconsolidated aeolian sand in low lying areas. They occur over the Precambrian hornblende -chlorite schist, rhyolite and carboneous phyllite. Along the Kataoti-Jayal tract, hardpan calcrete occur as boulders and gravel over the ferricretes of Late Neogene-Early Quaternary age. The calcretes around Narena, Churu, Talchappar, Ladnun Kataoti, Jayal, Didwana were studied in detail for their mineralogy, geochemical composition and stable isotope content. Micromorphology revealed thickening of calcite laminae downward and tapering at the sideward edges around the unweathered minerals of quartz and feldspars which indicate downward movement of carbonate solution and pore water. These solutions were probably derived from the upper horizons or surfaces bringing about the process of dissolution and recementation of individual laminae. Occurrence of fibrous attapulgite as coatings around the detrital grains and siderite (oolitic and pisolitic in shape) points to an subalkaline - subacidic process of pedogenesis. Attapulgite has formed due to the dissolution of silica grains. Lamination of calcite rim around the quartz grain indicates cumulative and compound pedogenesis, which probably occurred locally. Exfoliation of biotite grains in the primary calcium carbonate nodules is common. Spatial distribution, mineralogy and geochemical composition of the calcretes indicate that they have formed under poorly drained conditions probably within the capillary fringe in topographic lows. Stable isotope data of the hardpan calcrete laminae vary between -5.9l to -1.7l indicating their formation at - near surface (capillary fringe), probably supporting a thin column of soil. The source of most of the calcite was groundwater; however calcite nodule formation was largely dependent on pedogenic processes associated with evaporation, evapotranspiration and/or microenvironmental changes in pH and CO₂ partial pressure. However, dust is also a major source for the carbonate precipitation. It is commonly assumed that the powdery calcretes are younger in age compared to the more complex forms. However, occurrence of Middle Palaeolithic tools below the hardpan calcrete at Roopangarh and Dayalpura, and above the hardpan calcretes at Mitri, Genana and Rol, indicate that the morphology of calcretes is not a reliable indicator of age. Hardpan calcrete distribution is therefore, not merely a reflection of local topography but host material, sediment, time and rates of accretion, vegetation soil microenvironment and carbonate source.

A.L. Alexandrovsky¹, M.P. Glasko¹, S.N. Sedov³, N.A. Krenke², B.A. Folomeev², E.A. Kuznetsova²

The floodplains of rivers are characterised by a higher dynamics of all elements of landscape, including soils. During the Holocene the processes of river valley development, accumulation of alluvium, changes of flood levels and intensity resulted in periodical destruction of older soils and development of new ones.

In the floodplains of larger rivers as well as their smaller tributaries in the basins of Upper and Middle Volga, Oka, Moskva River, Upper Dnepr the sequences of buried soils were found. Their age, determined by ¹⁴C dating and archaeological findings, reaches 5000 ò?? 6000 BP. Soils were formed during the periods of low floods, when alluvial sedimentation stopped. Numerous ¹⁴C and archaeological dates indicate the following intervals of intensive soil formation on the floodplains of Russian Plain: 6500-4500, 4000-3000, 2200-900 BP (non-calibrated age).

Because of progressive accumulation of alluvium many floodplains were not flooded any longer in the late, sometimes in the middle Holocene. In consequence soils of zonal types ò?? Chernozems and Luvisols were formed on the floodplains. The periods of activisation of alluvial sedimentation, which resulted in the burial of soils, are induced by climatic changes, which occurred within the Holocene as well as increasing human impact. Deforestation and land cultivation in the river basins, which enhanced in the last 700 ò?? 900 years, caused the increase of intensity and level of floods. Because of this on many floodplains of Central Russian Plain Luvisols (Grey Forest Soils and Albeluvisols) were buried under recent alluvium, on top of which weakly developed Fluvisols are formed.

L.A. Alexandrovsky, I.A. Matyukhina

Texture differentiated soils (TDS) (Luvisols, Albeluvisols) were formed in the Russian Plain soon after the beginning of development of the Holocene soil and plant cover. Before, during Valday (WÓÌrm) glaciation sedimentation and cryogenic processes hampered soil formation, especially development of TDS. Buried paleosols of the last glacial maximum and Pleistocene-Holocene transition, found within contemporary forest zone, are presented by weak humus or gleyic horizons often with cryogenic deformations.

There are indirect evidences that first TDS were formed already in the early Holocene. However weak leaching of parent materials and still active geomorphic processes constrained their development. Soils with humus-accumulative profiles were spread much more extensively.

In the Atlantic period mature TDS occupied vast areas in the Russian Plain. However the relict second humus horizons (SHH) in some TDS profiles indicate, that the boundaries between Chernozems, Grey Forest Soils (Eutric Luvisols) and Sod-Podzolic Soils (Albeluvisols) were located to the north of present position. ¹⁴C dates of SHH range from 8000 to 3000 BP the differences being related to the rate of reworking of humus of these horizons, which are often on shallow depth.

In Subboreal and Subatlantic periods with forest advancing towards steppe zone and tundra ò?? towards forest zone the area of TDS grew considerably. In the profiles of TDS formed during this time SHH ò?? the relicts of earlier pedogenesis ò?? are present. SHH are better preserved in less drained positions and on more clayey parent materials. TDS which evolved from the middle Holocene humus-accumulative soils (Chernozems, Phaeozems) in the late Holocene do not differ from older TDS formed in persistent forest ecosystems regarding the degree of eluvial-illuvial differentiation.

We evaluated the rate of TDS development, studying soils on archaeological landsurfaces and river terraces of different age. Profiles without or with weak clay differentiation dominate on the landsurfaces with the age n´ 10 ò?? n´ 100 years. However clay differentiation develops sometimes on such landsurfaces when formed by leached loamy sediments. We found well developed Luvisol profile on the 1000 years old rampart of settlement Rzhaventsi (basin of river Dnestr). On the 2500-4000 years old landsurfaces TDS do not differ considerably from surrounding soils regarding the degree of clay differentiation.

J. BerÓ?nyi-Ó?veges, Z. HorvÓÅth, E. MichÓ?li, A. Mindszenty, T. NÓ?meth

Besides field observations, mineralogical and chemical analyses, micromorphological and scanning electronmicroscope studies were carried out in order to reconstruct soil forming processes in paleosol profiles in an open lignite mine located in North Central Hungary (Visonta, pediment of the MÓÅtra mountains).

Based on the results of the investigations, the recent soil and the paleosols have different parent materials and they were developed under different conditions. The present day soil is a Luvic Chernozem formed on calcareous loess. Under it, a red colored paleosol show evidences of both redeposition and in situ soil formation. The parent material is a weathered andesitic saprolite and red clays transported by mass movement to the pediment during the Pleistocene. In this epoch the MÓÅtra mountains were intensively uplifted that enhanced the intensity of this process. The prismatic and wedge shaped structural units with stress cutans indicate Vertisol formation which is supported by the high clay content and smectitic mineralogy. Bioturbation in different scale, shrinking swelling, leaching, CaCO₃ and Fe-oxide precipitation, erosion-sedimentation, weathering, clay mineral formation and transformation, clay movement, organic matter accummulation, reduction and oxidation and frost action were processes showing evidences of changing environment during the formation of the sequence.

The Zahvizdja profile is exposed at 310 m a.s.l. in a large open pit of several working levels, in which loam is exploited for a brick-field. Zahvizdja is situated in the East Carpathian Foreland, in the catchment of the Bystrycja Solotvinsò??ka river – Carpathian tributary of the Dniester river. This profile is connected with a terrace surface rising about 80 m above the valley floor. This terrace was formed as a result of dissection of the planation level reaching 360-380 m a.s.l., which is called the Lojova surface (Villafranchien). It is the lower one of two planation levels found in the East Carpathian Foreland.

Erosion rock socle built of the Tortonian marine clays is covered with the Quaternary deposits 22 m thick, which consist of three main units: lower one (19.0-20.5 m) – alluvial gravelly-sandy-silty, middle one (14.5-19.0 m) – clayey-silty, and upper one (0.0-14.5 m) – loessy. Eight interglacial paleosols occur in the profile of the Quaternary deposits.

Especially interesting in this profile is the middle unit containing four soils of the intergalcial rank. All these soils are of forest type, gleyed, with distinct Bt horizons, and in places also the Eet and A horizons; the younger the soil, the more intensive gleying. In the whole unit the soils are made conspicuous by the occurrence of the following cryogenic deformational structures formed in the periglacial environment: pseudomorphs of segregated ground ice structures, ice wedge casts and diapiric convolutions – plastic density deformations of amplitude over 1 m, which disrupt the A and Eet horizons. They form a distinct polygonal pattern in the horizontal plane, which can be related to spotted tundra. The youngest soil was partially destructed by solifluction.

Therefore, in the discussed part of the Zahvizdja profile four warmings and four coolings were recorded. Warm phases were characterized by temperate, wet climate warmer than during the Mesopleistocene interglacials. Periglacial climate occurred in cold phases; signs of cooling became gradually more intense. We relate these climatic phases to the lower part of the Pleistocene.

Investigations are partially supported by Grant 6 PO4 E 031 15 from KBN.

A.Bronger¹, S.N.Sedov²

Terrae rossae (Rhodoxeralfs) derived from calcarenites of Mid-Quaternary age occur in the relatively moist Rabat-Casablanca area on the Atlantic coast of Morocco. They show considerable development of clay minerals, including disordered and poorly crystalline kaolinites, which have formed by weathering of primary feldspars and to a lesser extent smectites and other phyllosilicates in the calcarenites. Some profiles are pedocomplexes with clear evidence that soil formation was interrupted by deposition of eolian materials. The amounts of weatherable minerals in the C horizons are not sufficient to explain the increase of clay content in the B_t horizons by weathering in situ alone. However, there are two reasons why the increased clay content is also difficult to explain by illuviation. First, older well-developed argillans are rare in most of the terrae rossae. Argillans occur mainly as coats covering carbonates in some BC_k horizons on unstable surfaces. These would be the most recent generation of argillans, so we suggest that as the leaching front became deeper former illuviation argillans were destroyed by argillipedoturbation and bioturbation. Both processes are documented micromorphologically. Another problem is that eluvial horizons are mostly absent. This can be explained by soil erosion resulting from human activities (deforestation, over-grazing), which would also explain the patchy distribution of terrae rossae and the local occurrence of thick red (rubefied) pedosediments. In this area the effects of human activities have hitherto been under-estimated compared with Quaternary climatic change. Weathering and masking of argillans can therefore explain the clay content of these soils, including the presence of kaolinites in a typic xeric soil moisture regime, with a small moisture surplus in the first three months of the year. On the younger calcarenites (<100,000 years old) the soils are Rendzinas or weakly developed terrae rossae with only slight formation of clay minerals (mainly illites). Earlier workers have suggested that a mediterranean climate with only minor fluctuations (e.g. mean annual temperature in glacial stages was only 2-3 degrees C less than today's, and rainfall was only slightly greater) persisted in the Rabat-Casablanca area throughout the Quaternary. As the terrae rossae containing large amounts of clay (including some kaolinites) must have formed over a period of several hundred thousand years in this fairly uniform climate, they should be termed vetusols. We extend Cremaschi's (1987) definition of vetusol as follows: "a surface soil which has undergone the same or very similar processes of formation under the same constellation of soil-forming factors, especially climate, over a long period of time, including at least some part of the Pleistocene; the pedogenetic clay minerals differ quantitatively and qualitatively from those in nearby Holocene soils because of the much longer period of soil formation".

In southwestern Morocco between El-Jadida and Agadir the soil moisture regime is dry xeric to aridic and terrae rossae occur only in small areas, mostly in depressions. However, they show similar or even greater amounts of clay formation to those in the Rabat-Casablanca area, but contain little or no kaolinite. The weathering and clay illuviation must have been preceded by decalcification, implying a distinctly moister climate here in the past. However, micromorphological features of recent recalcification are common in these terrae rossae, suggesting that they are not in equilibrium with the present climate and must be regarded as non-buried paleosols (relict soils).

V.A. Demkin, T.S. Demkina

Paleosoil studying of about 250 archaeological monuments (kurgans) of Bronze, Early Iron and Middle Ages was carried out in steppes of the Lower Volga and South Ural. The objects under investigation include such places of kurgan groups as: "Abganerovo", "Aksai", "Bakhtiyarovka", "El'ton", "Petrunino" and others in Volgograd region, "Djangar", "Tsagan-Nur" in Kalmykiya, "Pokrovka" in Orenburg region. Dynamics of paleoecological conditions has been reconstructed for the last 50 centuries on a basis of comparative analysis made on the properties of burried paleosoils of different ages. It has been established that Bronze Age (III-II millennia BC) in Volga-Ural steppes was characterized by substantial variability of paleoenvironment. Relatively favorable climatic conditions of the 1st half of the III millennia BC changed on aridization. Its maximum was at the joint of the III-II millennia BC. At that time soil-geographical borders shifted to the North. Chestnut soils, in particular, evolutionized into the light chestnut ones; ordinary chernozems developed into the south chernozems etc. Mass appearance of the solonets soils was marked, as well as formation of complex soil cover was observed. Factual data revealed give grounds to consider Bronze Age as crisis from paleoecological viewpoint. In the 2^nd half of the II millennia BC moderation of continental climate with increasing atmospheric humidity occurred. This led to shift of natural borders to the South with formation of modern system of soil zonality.

The interval of existence of Srubnaya culture can be considered as the period of climatic optimum. Microbilogical data allow us to consider the paleoecological conditions of IV-III centuries BC as more auspicious in comparison to those of XIX-XVII centuries BC. At the same time the correlation of microorganisms, using easily available organic substance and humus is indicative of the growth of vegetation fall. The growth of phytomass can be explained by climate's humidisation. This process began in the second quarter of the II century BC in Low Volga steppe and reached its apex during the period of the Srubnaya culture communities. Early Iron Age (I millennia BC - IV century AD) was characterized by alternating of arid and relatively humid periods that did not result in noticeable shifts of the borders of natural zones. Nevertheless, Savromatian (VI-V centuries BC) and Late Sarmatian (II-IV centuries AD) periods were marked by more favorable paleoecological conditions as compared to Early and Middle Sarmatian time (IV century BC - I century AD). Following paleoecological data it was revealed first Medieval climatic optimum, dated to approximately XI-XIV centuries. It was noted by us in Volga-Don region, Zavolzh'e and South Ural. Increased atmospheric humidity at that period led to local shift of soil-geographical borders to the South. This natural process manifested itself most vividly on the territory of Ergeninskaya Upland (Lower Povolzh'e).

The work was supported by the Russian Foundation for Basic Researches and Federal Purpose Program "Integration".

C.G. Dlussky

The Oka river drainage basin (from 52ÒÀN to 56ÒÀN and from 36ÒÀE to 44ÒÀE) is situated in the northern part of the loess area on the East European Plain. The thick loess-like silt of Dnieper (Saale) age occurs below complete Upper Pleistocene loess-soil series in the region. The Middle Pleistocene fossil soils underlie the Dnieper loess-like silt. They compose a series which includes 3 paleosols close to each other: Romny interstadial soil, Upper and Lower Kamenka interglacial soils (by chronostratigraphic scheme published by Velichko et al., 1997).

The uppermost Middle Pleistocene fossil soil of this series is the Romny soil. The soil has weakly differentiated gleyed profile (A1G-G). Micromorphologically, there are the evidences of weak humus forming in its profile. The profile is heavily cracked and turbated by cryogenic deformations. Amongst the deformations, solifluction dominates in the north and west of region, but small polygon cracking dominated in the south and southeast of the region. The nearest modern analogues of this fossil soil are likely tundra gley cryomorphic and taiga gley-cryomorphic soils. Therefore it could be an interstadial soil.

The older fossil soil is Upper Kamenka one. The paleosol has bleached horizon only in the northernmost part of the region. On the rest territory, the paleosoil has a profile A1'-A1''-B_t-BC and can be compared with modern brunizems or meadow-chernozem soils. The following processes took part in its forming: active humus forming, active lessivage, sialitization and humus illuviation. In the north of the region humus forming was less intensive, but the role of eluvial-illuvial processes increased. The fossil soil can be compared with modern gray forest or pseudopodzolic soils in the north of the region. Upper and Lower Kamenka paleosoils were formed during two separate epochs of soil formation.

The oldest soil is Lower Kamenka one. It has bleached eluvial horizon over the whole territory of investigations (profile A1'-(A1'')-A2-B_tf(B_t)-BC(BC_g)). Leading soil-forming processes were pseudogley one with the participation of humus forming in the NW part of the region under study. The soils were similar to modern pseudogley (distric planosol). Lessivage, Fe- and humus illuviation took part in forming of the Lower Kamenka fossil soil in the central and southern parts of the region. Lessivage played the leading role and soils were similar to modern pseudopodzolic soils (lessive, luvisols) in many cases.

The study is a part of investigations carried out in the Laboratory of Evolutionary Geography IG RAS.

I. Fedeneva, M. Dergacheva

The evolution of the environment has been studied by now rather well for flat territories as concerns decoding its main laws as well as prediction of possible development of natural compounds in varying conditions. There with the ascertained regularities unfortunately cannot be extrapolated to mountainous areas where provincial and zonal distribution of the landscapes is complicated by the processes of vertical redistribution of heat and moisture, these processes have not been revealed to completion yet. Moreover, different exogenic processes developed in the mountains cause bad conservation of soil profiles that does not permit to use traditional methods of paleopedology to diagnosticate the conditions of ancient environment.

The approaches proposed in the present paper are based on:

Detail studying of late Pleistocene-Holocene paleosols and/or pedogenesis signs of different Gornyi Altai regions sediments permitted to reveal peculiarities of climatic fluctuations in depending on territories location. So, Central Altai was characterized with more continental climate than North-West Altai though amplitude of landscape conditions changes on the whole was close for different Altai regions.

Landscape changes in Central Altai didn't exceed the limits of dry steppe, from one side, and cryoarid steppe ò?? from the other. There were no conditions for development of forest plant associations here in that period. In North-West Altai, on the contrary, forest associations often prevailed in landscapes. Here there were distinguished some stages of broad-leaved trees development, while in Central Altai their occurrence was limited by climatic continentality.

New approach permitted to suggest schematic map of the reconstructed mountainous landscapes of South-Eastern, Central and North-Western regions of the Altai Mountains not only for the main developmental stages of the environment throughout the past 130 thousand years, but also to reveal the special features within each of them. The periods of maximum glacial were found to be characterized by the simpler scheme of high-altitude sequence when cryoarid steppes expanded up to glacial border. At interglacial and interstadial periods the number of landscape zones is maximum and the structure of soil cover is more complex.

A. Golyeva, O. Chichagova

Modern and buried soils beneath gully sediments have been compared on the Southern Russian