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V.M. Alifanov, L.A. Gugalinskaya, Institute of Soil Science and Photosynthesis RAS, Pushchino, Moscow oblast
Paleocryogenesis existed during the whole Pleistocene, and was studied most thoroughly in soils of Mikulino interglacial (140-110 000 years ago) of the Briansk warm epoch (25 000 years ago) and of the final stage of the Valday Glaciation (Late Glacial, 15-10 000 years ago).
The Late Pleistocene loess-like loams sequence in the centre of the Russian Plain comprises two distinct paleosols: Mikulino interglacial (Mezen, Eems, Sangamon) and Briansk interstadial (Middle Valday, Denekampf, Farmdale). Both soils preserved the majority of morphological, micromorphological, chemical and other properties, f.i. clay and humus content, CEC, pH, etc. Well preserved were also features of soil cryomorphism.
Macromorphological paleocryogenic features of Mikulino and Bryansk paleosols were categorised into destructive (evidences of cracking, solifluction) and constructive (cryogenic aggregation).
Micromorphological evidences of paleocryogenesis are the following:
During the final stage of Valday glaciation the paleocryogenic processes were active, so that in recent soils their imprints are recognised. These are:
Paleocryogenesis features are extremely diverse in age as well. The analysis of paleocryogenesis in soils facilitated the solution of soil-historical, soil-evolutionary, soil-environmental problems concerning the nature evolution.
Becze-Deak J. and R. Langohr, International Training Centre for Post-Graduate Soil Scientists, University of Gent, Krijgslaan 281/S8, B-9000 Gent, Belgium
The Last Interglacial soil-sedimentary complex of the Wallertheim site is famous for it's rich Middle Palaeolithic bone and artefact finds. The section is situated at the contact between the alluvial plain and the neighbouring hills and it is composed of alternating more clayey and more silty sediments reflecting the complexity of processes acting at the edge of an alluvial plain. The soil-sedimentary complex studied here shows evidences of an aggradating alluvial plain with vegetation cover.
Careful field observations showed that close to the end of the alluvial sedimentation the soil-sedimentary complex has undergone a very severe frost action, including most probably a short lasting permafrost. The freezing in these fine textured material resulted in a structuration that deleted many of the former soil characteristics, such as the original structure and bioporosity.
The macro-, meso- and micromorphological study shows that there are 3 types of accumulations which can be related to the frost action in this studied complex: 1. Iron hypocoatings occur on the ped faces created by the frost in the upper part of the complex. EDXRA (energy dispersive X-ray analyses) studies show that these hypocoatings have high phosphorus content. In the iron depleted soil matrix no measurable amount of phosphorus could be detected. In the studied complex, known as an important Neanderthal butchering site and with evidences of animal puddling, the source of phosphorus is most probably related with animal excrements. Deeper in the complex similar iron hypocoatings and coatings have been observed along the horizontal frost fissures and pores preserved from before the frost action. 2. Manganese coatings are common in the deeper, but still frost affected part of the soil-sedimentary complex. They are associated with the above mentioned iron accumulations and show a framboidal morphology. 3. In the Eastern part of the excavation 1-2 cm thick vertical cracks filled with CaCO3 are present. In horizontal section these cracks show a polygonal pattern. According to the pedochronostratigraphy these cracks are subsequent to the above described frost action. At the microscale these accumulations are composed of micritic hypocoatings and infillings of several parallel microfissures. The fact that the CaCO3 accumulation in this noncalcareous part of the soil-sedimentary complex is only associated with these cracks indicates that most probably the precipitation occurred along the repeated ice segregation planes now represented by the microfissures.
The described accumulations being related to the pedality and porosity created by frost it is concluded that possibly they have been precipitated at the moment when the soil solution was freezing.
* Research funded by the SC-004 Project of the Federal Services for Scientific matters, Belgian State Science Policy Programming and the Belgian National Science Foundation.
Becze-Deak J., Langohr R., International Training Centre for Post-Graduate Soil Scientists, Univ. of Gent, Krijgslaan 281/S8, B-9000 Gent, Belgium
The seondary carbonates studied here belong to the Last Interglacial and Early Glacial soil-sedimentary complexes of the Wallertheim site.
The Last Interglacial soil-sedimentary complex of the Wallertheim site is situated at the contact between the alluvial plain and the neighbouring hills. The sediments of the alluvial plain consist of an alternation of more clayey, non-calcareous and more silty, calcareous sediments, reflecting the complexity of the processes at the edge of the alluvial plain. In this sequence several morphological forms of secondary carbonates ranging from weak hypocoatings to rough up to 10 cm large nodules have been recorded and sampled in the field. According to the field observations there is a gradient in the vertical and lateral distribution of the various forms of carbonates. The accumulations are composed of micritic impregnation of the matrix and of micritic coatings and infillings of the pores. They all show a rather similar orange red cathodoluminescence, with more brighter orange colours towards the pores and in the younger chronostratigraphical units. It is concluded that the various accumulations are precipitated from the fluctuating calcareous ground water table, in a climate with alternation of pronounced wet and dry season. Moreover their vertical and lateral distribution can be used as indicators of the geomorphological dynamics of the alluvial plain and of the intensity of the water table fluctuation.
The Early Glacial soil-sedimentary complex of the Wallertheim site consists of 2-2.5 meter humiferous material with several levels of 2-3 cm thick CaCO3 cemented, hard layers. Beside the cemented layers common, irregular, 2-10 cm large, hard, CaCO3 cemented nodules have been observed all through the complex. Some of these accumulations clearly resemble fauna galleries. The macro-, meso- and micromorphology combined with the cathodoluminescence observations suggest that the calcium carbonate cemented plates correspond to levels of higher calcareous fragments concentration. Moreover the micromorphological study indicates that the irregular nodules are very similar to the cemented plates. It is concluded that the CaCO3 cemented layers and irregular nodules are syngenetic with the evolution of the soil-sedimentary complex. They formed at the surface during a climate with pronounced and prolonged dry season, when the very little available moisture was only able for local redistribution of the CaCO3. This is also confirmed by the pores resembling gypsum rosettes infilled by subsequent sparitic crystals. While the cemented layers could be formed due to the exceptional concentration of the CaCO3 rich fragments, the irregular nodules are most probably representing fauna galleries, where animals were concentrating calcareous fragments.
The presented examples are clear evidences that the study of the morphological forms of secondary carbonates and the associated soil characteristics, as well as the study of the presence-absence of these items is a potential tool for environmental reconstruction.
* Research funded by the SC-004 Project of the Federal Services for Scientific matters, Belgian State Science Policy Programming and the Belgian National Science Foundation.
Ye. K. Bobrova, A.A. Bobrov, Faculty of Soil Science, Moscow State University
As a result of investigations of phytoliths in 72 plant species in Russia and Ukraine, more than 40 specific morphologic forms of silica were identified in plant cells. More individual in terms of their phytoliths spectra are sedges, cereals and coniferous species. Diagnostic importance of phytoliths in nemoral vegetation proved to be insignificant. The comparison of phytoliths morphology and data of cluster analysis permitted to specify several groups of sedges and cereals with similar phytoliths spectra. They may be recognised at both intra- and inter-genera levels.
In the sequence of soils on various soil forming rocks with different amounts of phytoliths the brown forest and dark coloured soils (Cambisols and Phaeozems) of Sikhote-Alin' mountains were the first (12% of the fine earth weight). The last were sandy soils - 0.6% of phytoliths.
The content of phytoliths in 0-2cm layer of the rehabilitated soils on mantle loams approaches that in sod-podzolic (Podzoluvisols) under primary southern taiga spruce forests already in the first 20-30 years. Most active is the process of phytoliths accumulation in semi-hydromorphic soils under artificial meadows, formed in the course of phyto-rehabilitation of lands.
Cluster Analysis of Phytoliths Spectra in Soils with Buried Horizons Indicates Shifts in Biogeocenoses Pattern During the Evolution History of Sikhote-Alin' Mountainous Soils. The Development of Recently Buried Horizon Proceeded Under the Canopy of Mixed Forest.
Paleosols in burial mounds in Samara-Orel' interfluve (Ukraine), formed at the boundary of Atlantic and Subboreal periods, correspond to ordinary and southern chernozems (Haplic and Calcic Chernozems, respectively) in terms of their phytoliths characteristics (data of comparative analysis with the cluster analysis applied). The second humus horizons of grey forest soils (Greyzems) of Vladimir opol'ie are conspicuous by their high amount of phytoliths (more than 5% of the fine earth) and by their broad spectrum (above 20 forms of sedges and cereals forms). Hence, we assume that the phytolith characteristics of these soils is one more argument in favour of the semi-hydromorphic stage (cereal-herbaceous vegetation) in their long history.
A.BRONGER1 AND S.N.SEDOV2, 1 Department of Geography, University of Kiel, Germany, 2 Department of Soil Science, Moscow Lomonosov University
Selected Terrae rossae of Rhodoxeralfs from calcarenites in all probability of Mid-Pleistocene age along Atlantic coast of Morocco show a considerable to extensive formation of clay minerals especially of kaolinites. Main sources of pedogenic formed kaolinites, mostly of disordered structure and poor crystallinity, are primary feldspars (> 2 m) and smectites (2-0.2 and <0.2 m) inherited from the calcarenites as the parent material although some eolian input is not excluded.
However, there are not enough weatherable minerals in sand and silt fractions including inherited smectites in the clay fractions to explain quantitatively the rate of clay increase by weathering in situ only. To explain the differences in clay mineral content by clay illuviation meet some difficulties; first, almost no well developed or aged illuviation argillans are visible in the Bt horizons of the majority of profiles. However, illuviation argillans are visible in the Bck horizons covering carbonates as unstable surfaces in the "typic xeric" soil moisture regime with still some water surplus in the first 3-3,5 months of the year (station Rabat). With deepening of the leaching front former illuviation argillans might be destroyed, only the "youngest" generation in present Bck horizon is visible. Additional possibilities of destruction of illuviation argillans are argilli pedoturbation, indicated by stress cutans and bioturbation seen e.g. by areas with crescent striated fabric (1). Second, an eluvial horizon is mostly absent. For this soil erosion seems to be responsible, as well as for patchy distribution of Terrae Rossae, as a result of land degradation mainly due to human activity which is still grossly underestimated in comparison with climatic variations in this area.
In areas more to the southwest with a "dry xeric" if not already "aridic" soil moisture regime only very few illuviation argillans can be seen in upper part of Terrae Rossae if any, but never in Bck horizons. Secondary carbonates can be seen already in rubefied Bt horizons.
(1) Stoops, G. 1983. Micromorphology of the oxic horizon. In: Bullock, P. and Murphy, C.P.
(Ed.) Soil Micromorphology, v.2, Soil Genesis, A B Academic Publishers, p. 419-440.
Richard T. BUSH AB and Leigh A. SULLIVAN B, A School of Geography, University of New South Wales, Sydney NSW 2052, Australia, B Resource Science and Management, Southern Cross University, Lismore NSW 2480, Australia
The mineral pyrite (FeS2) is common in coastal floodplain sediments deposited under estuarine conditions. Waterlogged pyrite remains stable, but when pyritic sediments are drained or excavated, it rapidly oxidises liberating sulfuric acid and iron. Once oxidized these sediments remain extremely acidic (ie. pH<3) for tens of years, affecting crop and pasture production and providing a source of toxic leachate, which has caused catastrophic fish kills along the east coast of Australia and elsewhere. An important consideration in the management and amelioration of pyritic sediments is the likely rate of oxidation, where drainage is required. Models describing the oxidation of pyrite exist, yet information about distribution and morphology of the pyrite mineral required in these models is limited.
In these study of the distribution, mineralogy and morphology of pyrite, we collected samples from three buried sediments with different textures, a sand, a clay and a sandy clay. A freeze drier was used to minimize deformation and oxidation. We used both reflected light microscopy on polished impregnated blocks, and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray microprobe (EDX) on fractured surfaces of specimens to assess pyrite distribution. EDX enabled the elemental analysis of individual crystals with different morphologies, to compare sulfur : iron ratios. The main mineral phases were identified by x-ray diffraction (XRD).
Pyrite although concentrated in organic remnants as reported elsewhere, is abundant also along fissure planes, pores and is finely dispersed throughout the clay fraction of the soil matrices. Pyrite occurs as framboids (ie. spherical clusters of individual crystal) and loosely arranged individual crystals. Most framboids ranged in diameter from 4 to 15, while crystal diameter ranged from 0.1 to 2. Crystals exhibited a range of morphologies including those with clearly defined facets including octahedral and pyritohedral habit, to globular forms with no defined facets. Coatings described as pseudo-skins by other researchers are evident on many framboids. These results and their implication on pyrite formation and the likely process of oxidation are discussed.
Buysschaert X., Langohr R. and J. Becze-Deak, International Training Centre for Post-Graduate Soil Scientists, University of Gent, Krijgslaan 281/S8, B-9000 Gent, Belgium
The craters of the East Eifel volcanic province have been important sediment traps during their geological history and are known as very valuable sites, where records of the past are often well preserved. The Tnchesberg site is known for it's important Middle Palaeolithic find horizons preserved in the loess soil-sedimentary complexes accumulated during the Pleistocene. Among the thick soil-sedimentary units present in the Tnchesberg 2 crater, the Last Interglacial sequence has been selected for more detailed study.
The sequence studied here includes a well preserved soil with a 60 cm thick non-calcareous humiferous surface horizon (A), a weakly developed eluvial horizon (E) and textural B (Bt) horizon developed in a 250 cm deep decalcified loess and the overlying soil-sedimentary units described in the literature as "colluvial" deposits. The 21 pedo-lithostarigraphical horizons (H) studied revealed the following soil characteristics and soil forming processes. - At the micromorphological study the upper part of the "colluvial" horizons (down to H6) shows clear evidences of stratification and minor bioturbation. The sediment is very heterometric. This horizons in the field present very abrupt boundaries. - The rest of the "colluvial" horizons (down to H9) have no traces of stratification, neither in the field nor under the microscope. These horizons on the contrary show clear evidences of bioturbation, indicating a more stable environment with continuously vegetated surface - The whole sequence of "colluvial" horizons present a few isolated limpid and dusty clay coatings which probably are of diagenetic origin. - The thick humiferous A horizon (H10-12) is very homogeneous and strongly bioturbated. Based on morphology there are no arguments pro or contra that the upper part of these horizons would correspond to redeposited sediments from an A horizon situated higher in the landscape. Except a few frost fissures no other freeze-thaw evidences could be detected. If the climate at some moment of the evolution was very cold than the soil most have been very dry. - Clay coatings are already common in the weakly expressed E horizon (H13-14). - The Bt (H15-19) shows in the upper half clear evidences of intensive swelling and shrinking with clay coatings incorporated inside the peds and with a striated b-fabric. This is related with a relatively high clay content, with smectites present in the clay fraction and alternating wet and dry seasons. The lower half of the Bt is indicating a much more stable environment with clay coatings only along the larger planes and channels. The b-fabric of the fine material is undifferentiated, indicating the possible presence of some amorphous colloidal fraction. - The carbonate nodules present in this Bt horizon are of diagenetic origin and most probably are the result of a lateral subsurface water flow.
Beside the clarification of the chronosequence of the pedogenetic processes, the main contribution of the micromorphological study is the detection and characterisation of a "special" facies of loess and the particular dynamics of the processes that have been acting in the upper half of the Bt horizon of the Last Interglacial soil.
* Research funded by the SC-004 Project of the Federal Services for Scientific matters, Belgian State Science Policy Programming and the Belgian National Science Foundation.
D.A. Cherniakhovskiy, Ye.M. Naumov, Dokuchaev Soil Institute, Moscow
Investigations of a soil series in cold cryomesomorphi landscapes permitted to make the following statements:
1. The cryometamorphic horizon, located at the depth 5-20 cm, and more subjected to soil weathering than other horizons, may be the source of silt both in present-day and past deflation-accumulative landscapes.
2. Size and shape of aggregates in this horizon depends primarily on parent rock, which may be rather reliably characterised by the bulk chemical composition. Soil moisture is also very important. The finest concretionary aggregates, with high deflation hazard, are proper to cruoxeromorphic soils on almost pure quartz materials with low Fe and Al concentrations (sandstones, f.i.)
3. In soils with elevated Al and Fe content the aggregation process is advanced and the size of aggregates increases.
4. Silt accumulations in recent soils and paleosols consist of 0.01-0.001mm aggregates, enriched in Al and Fe.
5. The following image of Late Pleistocene deflational landscapes may be proposed: a) dry (moisture/field capacity ratio is below 7); b)rich in silica (its total amount is above 70%, Al203 not surpassing 15%, Fe203 - below 4%).
The regularities revealed may be presented by the following scheme:
oxides concentrations landscapes xeromorphic mesomorphic Fe, high saturated Gelic Cambisol fine nodules Distric Leptosols non saturated Gelic Cambisol (non-compact spongy segregations) Al, Fe, low Distric Leptosols saturated Gelic Cambisol Mollic Leptosol fine nodules Al, Fe, highGelic Cambisol (loose flaky) Gelic Regosols (coarse nudules)
M.-A.COURTY, C.N.R.S., C.R.A. Lab. de Science des Sols et Hydrologie, INA P-G, 78850 Grignon, FRANCE
In the recent years, soil micromorphology research in archaeology has broadened from a systematic inventory of microscopic anthropic features to more comprehensive studies of anthropogenic and natural factor interactions. geared toward both cultural and environmental issues. Ancient living surfaces have been specifically investigated by studying distribution of human-derived microscopic residues and anthropogenic micro-fabrics, such as structuration due to human tramping. Results from a wide diversity of geographical contexts now demonstrate how integrity of the archaeological record, evident from the spatial artefact distribution alone, can be fully confirmed by soil micromorphology. Spatial archaeology has, also, benefited from improvement of the micromorphological anthropic facies classification aimed not only to identify well preserved settlements, but also residual traces of habitation areas, and discriminate them from intentional human-refuse dumpings that might characterize ancient cultivated fields.
The challenge of micromorphological research in off-site archaeology concerns our ability to identify anthropogenically induced soil-landscape transformations which differ only in formation rate from natural processes. For example, the micromorphological record of ancient burnt soils suggests that human-induced firing practices, aimed to prepare and maintain agricultural landscapes, had a different impact on the soil ecosystems than the ones of exceptional wildfires associated with climatically unstable short periods. Beyond cultural implication on ancient landscape management, this is an important environmental concern that legitimizes studies of the past soil record to better monitor catastrophic situations in the future.
In urban sites that display evident achitectural lay-out, soil micromorphology has been used to test attribution of a space to one category or another (streets, courtyards, walled-rooms, domestic and public areas) and to further elucidate variations through time in the use and maintenance of space. Analysis of the soil-sedimentary micromorphological signatures, specific of micro-climate conditions, provide distinctive evidence between roofed space from areas open to weather, Research effort has also focused on physical transformations of clay-rich materials, such as bricks, mud floors, owen and ceramics, that contribute to improve the knowledge of ancient earth-technology. Comparative studies of habitation areas in widely excavated sites has considerably stimulated adoption of sequential analysis to refine the archaeological time scale, and improve the precision of spatial micro-stratigraphic correlation. This issue oversteps archaeologist expectations not trained to appreciate the potential of the sedimentary matrix to document everyday use of the space. Our present position should be reinforced by improving the communication of our research products and maintain fascination of archaeologists for soil micromorphology.
Soil micromorphologists of the International Soil Science Society should be keen to provide full support to the increasing number of young geoarchaeologists, now engaged in soil micromorphological research. Publications in international journals should be stimulated, in order not to ruin patient research efforts by storing the golden mine as "shelf" reports. We should also claim that one collected, the micromorphological thin sections are an invaluable record, endlessly refreshed by our continuous progress, and therefore, are not museum objects.
G.A. Demidenko
The buried Holocene paleosols occur on river terraces and on interfluves in a wide zonal spectrum - from southern taiga to the steppe, they occur both as single paleosols and in soil associations. Chernozem-like paleosols (Mollisols or Phaeozems) are more distinct in terms of their morphology when they are found under steppe vegetation. Micromorphologically, chernozem-like paleosols have much in common, although they are encountered now in different zones and they originated in different periods of the Holocene; they are sufficiently well studied. We assume that horizons of similar genesis have the same micromorphological properties.
The Ah (mollic) horizon is blackish-brown in thin sections, it is clay-silty, rather compact, its plasma is humus-clay by composition, anisotropic, with scaly b-fabric dominant, there are also dendritic and granostriated b-fabric types, clay coatings. Moderate pedality: rounded, humus-impregnated aggregates. Intra- and interpedal voids are common. Biopores contain plant residues (with plant tissues preserved to a different extent) and organic castings. Bh horizon is peculiar by its combination of dark coloured and yellowish-brown microzones. Clay plasma has a striated (fibrous) b-fabric and displays mobility features. The parent material has a less compact fabric; the proportion of coarse silty grains increases, there are aggregates-ooids and few clay-humus inclusions.
The Holocene paleosols of the study area are peculiar by the absence of carbonates in Ah horizons, whereas there are carbonates in plasma and calcitic micropseudomorphoses in the subsoil.
M.I. Dergacheva, Institute of Soil Science and Agrochemistry, Novosibirsk, T.V. Tursina, Dokuchaev Soil Institute, Moscow
To diagnose the sediments in the high-mountainous Denisova cave in the Altay kray a new complex of methods has been applied: micromorphological analysis, determination of magnetic susceptibility, elemental composition of humus.
Sediments of Denisova cave comprise two different sequences: the Holocene layers about 2m deep are underlain by the Pleistocene series 5 m deep.
The Holocene sediments are presented by fine subparallel laminae 1-3 cm thick and contrasting in colour and composition: colours range from white or very light grey to dark brown and black, the composition may be either purely organic (dark organic or peaty) or mineral.
The light coloured layers are composed by loosely packed isotropic irregular star-like shape particles, they were diagnosed (by microchemical and micromorphological methods) as ash particles impregnated by different substances - humus, iron compounds, carbonates. Brown laminae are the most complicated in fabric and composition, they are basically organic, they were subjected to specific fermentation processes and to heating, they contain mineral admixtures. Black humus-organic laminae rich in plant tissues residues, are rather compact, extremely heterogeneous in terms of admixtures, lose their mineral ingredients when treated with acid and even water. There are many layers in the lower part of the Holocene stratified depth similar to the humus horizon of chernozems. Inclusions like remnants of osseous tissues, excreta of animals, litho- and pedo-relics are encountered in all the laminae. All of them, the only exception being chernozemic laminae, display subhorizontal pores-planes (Schlieren).
The Pleistocene deposits do not have stratification, except for local sets of fine laminae, glosses, infillings, fan-like patterns are common. Inclusions are abundant, these are: bright ochreous bones, black charcoals, stones, artifacts. However, against the background of this random orientation of these bright-coloured natural (soil and lithogenic) and anthropogenic ingredients we managed to guess "soil profiles".
Soil formation revealed micromorphologically is operative on 2 types of material: 1 - sandy-silty-clayey with loessic aggregation and low carbonates content, 2 - clayey highly calcareous. In both cases soil profiles start with highly pedal and strongly zoogenically reworked humus horizon. Humus microforms, faunal excreta, porosity and pedality indicate pedogenesis of the temperate brown forest type. Data on humus composition and magnetic susceptibility confirm the results of micromorphological studies.
N.FEDOROFF1 AND V.A. DEMKIN2, 1 Science des Sols et Hudrologie, INA P-G, 78850 Thiverval-Grignon, France, 2 Genesis and Evolution of Soils, Institute of Soil Science and Photosynthesis, RAS, 142292, Pushchino, Russia
At first, paleopedologists were attracted by some very broad, pedogenic characters of paleosols as reddening, primary mineral weathering which led them to consider that the soil development during the Quaternary period was linear, only time dependent. Their environmental significance was acknowledged when soil micromorphology started to be systematically used in paleopedology in the 1970s. The relationships existing between Milankovitch cycles and soil genesis were then established which led to concepts like pedological phase and cycle. Current developments in paleopedology mainly supported by soil micromorphology are focusing on:
(1) The close relationships existing between erosional, sedimentary and pedogeological processes in paleosols. Microscopic studies of loess-paleosols sequences, e.g. in China, have revealed that the typic loess exhibit in most cases a pedological fabric which has completely erased depositional features while it has been demonstrated that dust continued to deposit pedological; features, fabrics as well as of horizons, e.g. those resulting of clay translocation.
(2) The great sensitivity of soil systems to environmental conditions and consequently the great potential of soils to reconstruct paleo-landscapes with short time spans, e.i. - 100 to 1,000 years, have been recognized mainly through multidisciplinary researches conducted on and around archaeological sites. A soil chrono-sequence with a few centuries time span has been established in southern Russia by studying virgin soils buried under funeral mounds, age of which extends from Early Bronze Age to Middle Ages. These investigations led to revise our ideas of soil development during Holocene and more generally to refine some general concepts of soil genesis, e.g. the steady state as well as our knowledge of some soil forming processes, e.g. carbonate redistribution in soils.
(3) Impact on soils of abrupt events. The abrupt climate changes and more generally the great climatic instability during the Last Glacial period recently evidenced by paleoclimatologists on stimulation for interpreting paleosols dated from this period. The classical concept of a progressive soil evolution induced by orbital forcing cannot stand anymore which leads to reinterpret most of the features and fabrics of paleosols formed during the Last Glacial period. Stable isotopes are also contributing to improve our knowledge of paleosols.
Further development of paleopedology could be oriented towards an improvement of signature interpretations in soils of sedimentary processes versus pedological ones one hand and of abrupt events versus progressive ones on the other hand. The precision in regional stratigraphic and if possible global correlation of paleosols must also be increased. Progress has also to be achieve in order to quantify the time span required for main soil forming processes to reach a significant development. Paleopedology has to bring in the future a large set of data in multidisplinary, global-scale studies of the history of the earth. The results of these studies will have wide application to many problems, including the past history of global climate change and other environmental concerns.
E.I. Gagarina, St-Petersburg State University.
The territory is dominated by soil forming rocks of glacial provenance, nevertheless, in areas with shallow Quaternary mantle the effect of pre-Quaternary sediments on pedogenesis is conspicuous; such are soils on local till, in particular.
Micromorphological research has been done for soils on local moraines with admixture of Devonian rocks (red sandstones and clays) and of Ordovician limestones. These inherited materials are subjected to strong transformations: argillaceous lithorelics become intersected by fissures, so they get comminuted, mobilised and redistributed: they may be discovered as iron-clay coatings in the subsoil.
Carbonate containing particles undergo dissolution, ferrigination, locally - metasomatic argillification. The former presence of carbonates in the topsoils may be recognised by the properties of iron-clay aggregates with a specific vesicular or lattiform structures, in which cells the remnants of calcitic grains may be encountered, as well as siliceous neoformations proper to calcareous sediments, or light coloured clusters of terrigenic material.
Very distinct are lithorelics in profiles of soils on varved clays, where they occur as fragments with stratified fabric, or individual silty or clayey inclusions. Most stable are argillaceous lithorelics occurring in all the soil horizons. Pedogenetic processes cause their cracking, erosion of the surface, re-orientation of clay particles, re-distribution of substances. Such lithorelics are usually absent in the topsoils of mature soils on lacustrine-glacial clays ("poddubitsa").
The abundance of lithorelics increases in man-affected soils: in young soils of rehabilitated landscapes, in artificially drained soils. In the former case the admixture of pre-Quaternary rocks in tailings material strongly increases, and in this way the soil-forming substrate seems to be less "mature". Soil formation progresses quickly, being accompanied by physical weathering, carbonates removal, leaching, fersiallitization and humus accumulation. Drainage with subsequent agromeliorative reclamation of soddy podzolic surface-gleyed soils on varved clays is accompanied by the development of contrasting redox regimes, accelerated agrogenic oxydogenesis, deep transformation of the mineral micromass, enhanced eluviation. All this results in transformations of initial soil fabric, destruction of lothorelics and formation of more differentiated soil profile.
Givi J.1, E. Van Ranst2 and G. Stoops2, 1 Agricultural College, Shahrekord University, P.O. Box 115, Shahrekord, Iran, 2 International Training Centre for Post-Graduate Soil Scientists, University of Ghent, Krijgslaan 281/S8, 9000 Ghent, Belgium
Many regions that are arid today have known a more humid climate in the past. Several studies have shown that fundamental changes in sedimentation regimes and pedogenetic processes have occurred in the present-day arid lands, as a result of comparatively minor changes in climatic conditions in the last 20,000 years.
In order to study paleo-environmental changes in the Iranian central desert, a micromorphological investigation of alluvial soils in the Isfahan area has been carried out. The studied soils belong to different physiographic units : old and recent terraces of the Zayanderud river; alluvial fans formed at the foot of cal-careous (limestone and marl) mountains by enhanced run-off; and playa lowlands, located in between the fans and the recent terraces. The Zayanderud river debouchs into the Gavkhouni lake, actually situated in the eastern part of the study area. During the transitional stage between the glacial and the interglacial period, this lake was much bigger than today, and covered a large part of the Isfahan area. It is believed that the lake ex-pansion was caused by an enhanced run-off, resulting from ice-melting, and by low evaporation conditions (1).
Microscopic features observed in the studied soils (gypsum pendants in the soils on the old terraces; carbonate pendants, weathered marl fragments, and clay coatings on limestone fragments, in the soils on the alluvial fans; lithological discontinuities, charcoal fragments, and indications of the former lake floor in the soils of the playa lowlands) suggesting paleoenvironmental changes, including the lake expansion, will be discussed in detail.
These observations allowed to conclude that the climate of the Iranian central desert was dry during the late glacial maximum, which is in contradiction with former opinions.
Literature Cited (1) Krinsley, D.B., 1970. A geomorphological and paleo-climatological study of the playas of Iran. Part 1, U.S. Geol. Survey, Washington, D.C. 20242, 329 p.
S.V. Gubin, O.S. Khokhlova, Institute of Soil Science and Photosynthesis RAS, Pushchino Moscow oblast
The micromorphological method has been recently applied in archaeological research to solve problems concerning the technology of burial mounds construction and the time of their existence in the steppe and semidesert zones, it was also helpful for argumenting probable reconstructions and landfillings. The method of the embankment constructing - by extensive or local digging may be substantiated, the initial depth of the ditch and the duration of the old burial mounds exposure were determined. A detailed analysis of pedality and aggregates shape, size, fabric can provide information even on the season when the burial mound was constructed and people buried.
Micromorphological studies of samples taken from sediments adjacent to the burial hill and from infillings of Late Bronze and Early Iron graves permitted to re-evaluate data on the burial ceremonies, to investigate the composition of litters, ceilings in graves, of some mineral compounds used as ritual substances. Remnants of very fine charcoals, fusing rate of phytoliths, changes in upper soil horizons fabric in the area affected by burial activities were interpreted in terms of use of fire by ancient people both for cooking and burial ceremonies.
Micromorphology of samples from ceramic vessels found in burial mounds permitted to recognise the organic matter stored in them - differentiate the plant and animal remains, in some cases the former may be even identified in terms of systematics.
Literature and authors' data prove that application of micromorphology to studies of archaeological objects and historical monuments gives new information and reliably arguments the existing one, so this method is thought to be expedient when carrying out integrated research.
B.A. Ilychev, A.A. Golyeva, Institute of Geography, RAS, Moscow
Microbiomorphological analysis presumes a microscopic investigation of plant tissues, detritus, charcoals, phytoliths, pollen and spores, cuticula imprints, sponge spiculas, diatoms, etc. It contributes to reconstructing ancient pedogenetic conditions, evolution of soils and of soil mantle, natural and anthropogenic pedosediments.
The micromorphobiological analysis was used for explaining the unusual occurrence of a black vertisol in the topographic pattern of Eastern Georgia foothills. Small areas of these soils are often encountered in the upper parts of slopes under subtropical dry sparse forests and shrubs. The middle part of the humus horizon of a black vertisol with the C-14 age above 11 000 years was studied. The catena with this soil is located on the southern macroslope of Jalno ridge.
Microbiomorphs are presented by few phytoliths of silvatic Graminaea, pollen of Briophyta and Polypodiophyta, as well as by abundant pollen of Cyperaceae, Chenopodiaceae, Alismataceae, Caryophyllaceae and two hydrophyte families: Nymphaceae, Lemnaceae. Plant residues embedded in the black mineral mass are composed of partly mineralised Carex peat. Similar boggy-lacustrine associations are unknown in this region.
Fragments of red fersialitic soils have been encountered in the upper part of the catena above the vertisol area. Hence, the black vertisol, being a lower catenary member, may be regarded as a result of transformations of a mixture composed of red smectitic deluvium with the drying peaty material; the red smectitic soil occupies a higher position in the catena. Reconstruction of the evolution of relief presumes the existence of advanced denudation, that has cut the soil and translocated the black vertisol to an unusual (in terms of soil origin) position on the slope.
P.A. IMBELLONE AND J.E. GIMENEZ, Instituto de Geomorfologia y Suelos. Universidad de La Plata. 3 N 584.1900 La Plata. Argentina
Soils developed in highly calcareous Holocene parent materials are common in the littoral region of NE Buenos Aires province. Redistribution of CaCO3 has been observed in many profiles; however, there are few investigations concerning the processes of its dissolution and recrystalization. The objective of the paper is to describe the micromorphology and discuss the genesis of pedogenic calcite of carbonate-rich soils.
The region is a coastal plain, about 1-50 km wide and 500 km long, with features related to marine actions such as shell and sandy beach ridges, mud flats, tidal flats, dunes, etc. originated mainly by sea transgressions and regressions (1). The inner border of the coastal plain limits with a high plain, located at an altitude of more than 5 m, it is constituted by eolian and fluvial continental sediments, which underlie the marine deposits at variable depths. The climate is humid and temperate, with mean annual rainfall of 900-1000 mm and mean annual temperature of 15-16o C. The main plant communities are wet and salt-grass meadows and, especially in shell ridges, tree and shrub communities (mainly Celtis tala).
Representative soils were studied in shell ridges (Rendzic Leptosols - FAO/UNESCO - or Calciudolls - Soil Taxonomy) and sandy ridges (Calcaric Regosols or Udipsamments). CaCO3 redistribution is found in the whole sequences, in the marine and continental loessic sections.
Lithogenic calcium carbonate consists of bioclasts, calcrete nodules and sparite fragments. Dissolution occurs on pelecypod shells or their fragments both in the biogenic deposits and the underlying sediments. Recrystalization phenomena are observed in continental and marine deposits and form colorless calcitans with a fibrous fabric arranged as coatings or bridges between skeletal grains or infilling inter- and intrapedal voids. Acicular calcite is the neoformed pedogenic mineral. It forms a dense network of acicular fibers, 30-120 m long and 4 m wide. The crystal abundance in voids ranges from a few needles to a tight self-supporting network where voids are nearly absent. There are also tangential needles on microfissure walls with the c axis parallel to deposition surfaces.
Acicular calcite is formed by quick evaporation in summer (mean temperature 22o C, mean rainfall 300 mm, mean potential evapotranspiration 350 mm). There is also a strong influence of marine salts and smectite clays. In the sequences studied, the main source of CaCO3 is bioclastic. Acicular calcite is formed in situ or following a short mobilization and represent an early pedogenic cement which infills cavities in biogenic deposits. CaCO3 enrichment in loessic paleohorizons agrees with the classical model of calcic horizons originated by translocation.
Literature Cited:
(10 Fidalgo, F. 1979. Upper Pleistocene-Recent marine deposits in NE Buenos Aires province, Argentina. Proceedings International Symposium on Coastal Evolution in the Quaternary. K. Suguio et al (Ed.). IGCP Project-INQUA. Sao Paulo, Brazil. 384-404.
A.V. Ivanov, Yaroslavl' State Technical University, V.F. Babanin, S.A. Shoba, Moscow State University
Magnetism of soil forming rocks depends on the contents of magnetite and hematite minerals (and their substituted variants) and is regarded as a paramount agent responsible for the average magnetic susceptibility of the soil profile. Hypergenic weathering of massive crystalline rocks, operative under high partial concentration of free oxygen and high humidity, causes the decrease of magnetic susceptibility and magnetic saturation of loose sediments due to magnetite oxydation and decomposition of unstable magghemite.
The contribution of silty fallout is regarded as the agent of secondary importance. Its magnetic effect is superficial: silty accumulations contribute to soil magnetism increase via soil surface. The cosmogenic or technogenic source of soil magnetism is proved by the occurrence of spherules in the topsoils. Both technogenic and volcanic deposits strongly depend on the distance of their local source, whereas technogenic, volcanic and cosmogenic fallout depend on time. Thus, the input of the latter category is assumed to be regular during the whole period of soil formation on the Earth, volcanic deposits are clearly periodical, technogenic input started approximately two centuries ago.
The synthesis of magnetic minerals in solutions within the zone of hypergenesis has many limitations, and seems to be local. It is realised within the framework of soil spatial heterogeneity under reductive conditions and oxygen deficit.
The biogenic synthesis of magnetic minerals is probable in soil oprganogenic horizons, and this hypothesis is supported by the discovery of bacteria with magnetite in their cells or surfaces.
In humus horizons of buried soils the prerequisites for magnetic minerals synthesis and decomposition change. Conservation of magnetic spherules and, partially, of magnetic soil profile for a long time is possible only in automophic sites. Thus, magnetic spherules were discovered in 40-50 years old peatbogs above and below Carboniferous coal strata. Presence of spherules in paleosols of Dnestr region, Stavropol kray correlates with elevated magnetic susceptibility of buried humus horizons. There is also a dependence between the weakening of magnetic susceptibility and duration of soil burial under mound hills and banks in steppe areas.
F.S. JONES, N.E.SMECK, AND J.M.BIGHAM, School of Natural Resources, The Ohio State University, Columbus, OH 43210 USA
Paleosols mantled by loess occur on Illinoian-age terraces in southern Ohio, USA. A dense, loamy zone of questionable age and origin is interposed between the surficial, Wisconsin-age loess mantle and the underlying truncated Sangomon paleosol formed in glacial outwash. One pedon is deep loess (178 cm) at the bluff and two pedons 9.3 km east of the bluff (84 cm of loess) were examined to better understand the stratigraphy of these soils.
Micromorphological evidence of frost activity (Mermut and St.Arnaud, 1981) was present at all three sites. Horizontally banded distributions of vesicles and dark isotopic plasma were present in the basal section of loess at the bluff site. Banded distributions of skeletal grains and voids in the loamy zone occurred at all three sites and were expressed macromorphologically as weak fine platy structure. Skeletal grains set into a dense groundmass of fine sand and silt with low void ratio and high bulk density (1,95 Mg m-3)and moist brittle consistence in the loamy zone suggest that a densification process has influenced this material (Bryant, 1985). Embedded papules and embedded grain stress ferriargillans in the truncated paleosol suggest mechanical reorganization of fabric (Brewer, 1976). The micromorphological features evident in this investigation together with involution features (Everett et al., 1971) and banded fabric (Thompson and Smeck, 1983) reported in similar strata elsewhere in east-central and southern Ohio suggest that periglacial processes influences the loamy zone and Sangomon paleosol immediately preceding the deposition of Wisconsin-age loess.
Literature Cited.
Brewer, R. 1976. Fabric and Mineral Analysis of Soils. Robert F. Krieger Publ. Co., Huntington, NY. 482 p.
Bryant, R.B. 1989. Physical properties of fragipan formation. In N.E.Smeck and E.J.Ciolkosz (Eds.) Fragipans: Their Occurrence, Classification, and Genesis. Soil Sci.Soc.AmSpec.Publ.No.24. SSSA, Madison, WI. p. 141-150.
Everett K.R., G.F.Hall, and L.P,Wilding. 1971. Wisconsin-age cryoturbation features in central Ohio. Geol.Soc.Am.Bull. 82: 1407-1410.
Mermut, A.R. and R.J.St.Arnaud. 1981. Microband fabric in seasonally frozen soils. Soil Sci.Soc.Am. J.45: 578-586.
Thompson, M.L. and N.E.Smeck. 1983. Micromorphology of polygenetic soils in the Teays River Valley, Ohio. Soil Sci.Soc.Am. J.47: 734-742.
Tang KELI, He XIUBIN, State Key Lab. of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, CAS. Yangling, Shaanxi 712100, China
Paleosols of Loess Plateau in Quaternary are characterized by accretionary pedogenesis, welded profiles, superimposed climatic intensities and deposition gradient (1). Unfortunately, many secondary or accretionary phenomena are indiscriminately taken as original or inherent features, thus, the paleosol forming process and associated paleo-environment reconstruction will be confused and wrong conclusion will be draw. Micromorphological investigation shows that secondary changes occurred in paleosols after buried by latter depositional loess. The coexistence of carbonate and argillic processes; the optical oriented clay and weak alkaline conditions were widely identified in paleosol thin sections. A great deal of reddish-brown optical orientation clay over pores or cracks in sinter, fluid or shell form was found in the soil-matrix of paleosols in the Middle Pleistocene and Late Pleistocene. And concentrated secondary microcrystalline of needle crystalline calcite can frequently be detected in the pores above the oriented clay.
As far as the paleo-climate was concerned, the climate related to paleosol forming was more humid and warmer than the present climate. The paleosol must be showed lower pH value and higher mineral weathering and leaching processes than present day. The loess-paleosol series reflected the alternation of landscape-climate, as well as revealed the various genesis of paleosols connected with the changes and transition of paleo-ecological environment in space and in time.
Further more, based on micromorphological investigation, we recognized that the so-called present-day soils - Heilutu (calcium black soil) and Lutu (cinnamon soil) (2) were buried paleosols, which consisted of one paleosol formed in the Middle Holocene and one loess cover layer (30-70 cm) by natural loess deposition and human's inputs. And the cover layer seems that the Loess Plateau has entered a new loess depositional cycle since 3,000 years ago.
Literature Cited.
(1) Tang Keli, 1981. Micromorphological characteristic of Wugong paleosols. Sci. Bulletin. Vol. 98, 56 p.
(2) Zhu Xianmo, 1962, Lutu Soil. Chinese agricultural publish house, Beijing. 3 p.
Rob A. KEMP, Edward DERBYSHIRE, Meng XINGMIN, Department of Geography, Royal Holloway, University of London, Egham , Surrey TW20 OEX, United Kingdom.
The thick sequence of interstratified loess and paleosols that comprises the Loess Plateau of China represents an indirect record of changing monsoonal dominance over the last 2,5 million years. Rapid accumulation and minimal pedogenic alteration of loess occurred during periods when the winter monsoon circulation strengthened, whilst soil development was favoured during intervening phases of reduced aeolian inputs and increased precipitation associated with change to summer monsoonal dominance. The S1 pedocomplex, correlated with Oxygen Isotope Stage 5 of the ocean cores, varies considerably in its form and character as it is traced in a southeast-northwest direction across a climatic and depositional gradient. In the west and northwest, where loess accumulation rates were high and pedogenic processes restricted to shallow leaching and limited bioturbation by the low rainfall, the pedocomplex comprises a series of discrete weakly- developed paleosol units separated by less-pedogenically altered layers of loess. In contrast, at sites farther away from the loess source area in the more humid southeast, the S1 paleosol is a thinner, welded and more pedogenically-developed unit dominated by the effects of extensive leaching , bioturbation and clay translocation processes.
It has been difficult to separate out and link the sequence of sedimentary and pedogenic phases responsible for the development of the pedocomplex across the Loess Plateau using traditional field techniques or even bulk analytical procedures (such as magnetic susceptibility of particle size). A micromorphological approach, based upon sets of closely-spaced thin sections taken throughout S1 at four sites located at strategic locations along the climatic and depositional gradient, has been utilized to reconstruct the sequence of different pedogenic and sedimentary events leading to the development of the pedocomplex. Correlation of the reconstructed pedosedimentary stages between each of the sites allows a better appreciation of the regional extent of palaeomonsoonal variations during this crucial period of the Quaternary.
Kulinskaya, E.V., Makeev A.O., Dokuchaev Soil Institute, Moscow,
Soil microstructure on loesses reflects stages of soil profile formation, related to parent rock sedimentation as well as transformation by various syngenetic and epigenetic, including soil (relic and modern), processes.
I. A group of inherited features.
1. The features, that had been formed during parent rock sedimentation and common for various loess sediments are the predominance of skeleton grains of coarse silt size, quartz/feldspar composition and mean roundness. These features are generally inherited in all horizons of the solum. Variability of these features in soil horizons of a given profile is a result of initial heterogeneity of parent rock material.
2. The features, that had resulted from different stages of parent rock transformation may be syngenetic as well as epigenetic (including relic soil properties). A group of these features includes distribution pattern of skeleton grains in the matrix (ring-shaped, clustered, fluidal, subparallel), microaggregation of plasma and type of it's orientation, presence of ooids, structural pattern of Bt horizons of Podzolic (Podsoluvisols, Luvisols) and Grey Forest soils (Luvisols), the major part of texture pedological features. The features of this group may considerably differ in various loess sediments. E.g., soils on loesses in the central part of loess area (South-West part of Russia, Central Ukraine) are characterised by loose packing of skeleton and plasma, high porosity of the whole matrix together with it's weakly expressed structure pattern, high plasma microaggregation and it's low optical orientation , small amount of texture pedological features . While parent rocks in the northern part of loess area (mantles loams) are characterised by compact packing of skeleton and plasma and low inner pedal porosity together with well expressed structure pattern and abundant texture pedological features (cutans and subcutans). Plasma of mantle loams has high birefrigence and well expressed optical orientation. Inherited features of loess transformation are mostly preserved in the heavy-textured part of texture-differentiated profiles (argic horizons). Dark-coloured subsurface humus horizons and their fragments are relics of cryo-hydromorphic stage of soil formation, simultaneous to final sedimentation.
II. A group of modern soil features.
The following microstructure features demonstrates correlation with modern bioclimatic factors: colour of plasma in the upper soil horizons, determined by it's composition (humus, clay, iron ), structure pattern of upper soil horizons, amount of plant residues, degree of their transformation, amount of fecal material of soil fauna, type of humus, pedological features (Fe-Mn concretions, soil cutans).
Langohr R. and J. Mikkelsen, International Training Centre for Post-Graduate Soil Scientists, University of Gent, Krijgslaan 281/S8, B-9000-Gent, Belgium.
Two profiles developed in Tertiary sands and situated at 5 m distance from each other, are studied. Profile 1 (P1) is a very well preserved Iron Podzol soil buried under a silty earth wall of Hallstatt Age. Such soils, considered to have developed originally under natural forest conditions ("Forest Podzols") are absent today in Belgium. Although Iron Podzols have previously been recorded on a few archaeological excavations in Belgium, they have never been studied in detail in this area.
The absence of Iron Podzols at present is attributed to the influence of man. Clearing of the forest by fire and the following extensive sheep grazing, with concomitant development of a heather vegetation, have generated the development of the Humus/Iron Podzols ("Heath Podzols") represented by P2. Also here the podzolization process can be considered to be relict as a result of the later spreading of a 20-30 cm thick silty layer, probably in order to increase the fertility of these sandy soils. After the development of a 2-4 cm thick humiferous A horizon on this silty layer, the soil has been spaded one single time, mixing again the surface horizons. Since then there are no more traces of any agricultural or anthropogenic activities.
Both profiles have been sampled and described in detail in the field and in the laboratory (meso- and micromorphology). None of both soils shows clear monomorphic coatings. The Bir horizon of the Iron Podzol has a brown pelletty microstructure, with aggregates that are to some degree fused together (incomplete pedality). The upper part of this horizon shows a clear clay illuviation from the overlying silty material. In P2, the humiferous accumulations of the Bh horizon are largely composed of dark grey polymorphic pellets. The Bir horizon is very similar to the one described in P1. In the transition horizon both the individual humiferous and the fused ferruginous pellets occur one besides the other, with no evidences of transitional pellet types, pointing to a chronosequence, with first the development of a Bir horizon, and later, related to changes in the environment, the development of a Bh on top of the Bir horizon. Also P2 shows evidences of clay illuviation from the silty material that was added on top of the Humus/Iron Podzol profile.
The presence in both profiles of clay illuviation from the added silty material (excavated from nearby soils developed in loess), shows that clay migration can occur in relatively acid conditions (pH 5.0). Possibly the mixing of the soil material when dumping the earth has some influence on the clay migration process.
Research funded by the Danish Research Academy, Aarhus, Denmark.
Lomov S.P.1, T.V. Tursina2, L.P. Zkhou1, 1 Agricultural Institute, Penza; 2 Dokuchaev Soil Institute, Moscow
The correlations between magnetic susceptibility (MS) values for recent soils and climate permitted to use the data obtained for paleoclimate reconstructions.
Soil-loess sequences in Tadjikistan are distinctly differentiated in terms of MS values: 20-30 for soils and 60-220 for loess, with the upper three soil-loess complexes (pedocomplexes) displaying the highest values - 100-220. There is a decrease to 60 beginning with the fourth pedocomplex, although neither morphology, nor chemical and granulometric compositions do not substantiate this differentiation. To solve the problem micromorphological method was applied.
Micromorphological studies of paleosols and enclosing loesses revealed particular features of loess sedimentation and pedogenic alteration of loessic material.
The subparallel orientation of mica and other elongated skeleton grains testifies to the water transportation and lacustrine sedimentation, and this may be a reason for a drastic decrease of MS values.
Paleosols are conspicuous by their higher humus content (as compared to loess), specific biogenic porosity, depletion of carbonates and weak insular plasmic fabric. Thus, the upper soil of the fourth pedocomplex may be diagnosed as a leached cinnamonic soil.
Other paleosols have many coatings and subcoatings in the complicated system of voids. Carbonate neoformations may be regarded as polygenetic or diagenetic features. In the lower part of the fourth pedocomplex a typical serozem has been identified; it didn't have strong redistribution of carbonates and had high biopedoturbation.
For the purposes of paleoclimate reconstruction the correlative data were superimposed upon the climatogram of soil distribution. Low MS values coincided with the serozems areas, intermediate values - with calcareous and typical cinnamonic soils, the highest values - with leached cinnamonic and brown forest soils. The following assumptions were accepted: the validity of an actualistic model and the carbonate content in loesses equal to 15-20%.
The reconstruction indicated the existence of arid periods of loess accumulation with the decrease in rainfall by 250-300 mm, and mean annual temperature being the same as during the Holocene or by 2-3o higher. The existing hypothesis of a cold model contradicts to the presence of carbonates in loesses, since decalcification would take place in colder climate. Carbonates content is thought to be an ephemeral soil property sensitive to climate changes. Therefore, the content of carbonates 15-20% is an indicator of rather stable paleoclimate. Contrary to sedimentation phases, those of pedogenesis occurred under climatic conditions similar the that in the Holocene with prominent fluctuations in Early, Middle and Late sections.
Vitric Andosols Typic Andosols Clayey mollic Andosols Profiles Lag1rs;Lag3rs; Lom1; Rib2; Cha1 ps N.2; Lix1, ps N.3,4,7,9,10,11,12 Lag1ps; Lag3ps; Lag2, San1rs; Cha 1 ps N.1: Lix 1, ps N. 1,8 San 1 ps, Lix 1 ps N. 5, 6 Structure single grains and granular granular and subangular blocky angular and subangular blocky Pores and pore space +++ +++ + Bulk density 0.6-1 0.4-0.8 1.1-1.4 pH 5.9-6.5 5.5-6.5 6.8-7.1 Acid oxalate extraction (Al+1/2 Fe); USDA method 1.0-1.5 2.0-3.0 0.6-0.7 Clay coatings - -(+) ++ Fe segregations - -(+) +++ Matrix optical anisotropism - - +(+) Pumice: degree of weathering + ++ ++++
Table. Some of the mean results of the analysis. Abbr.rs.: recent soil, ps: paleosol, N. number, - absent, + relative degree of frequency.
The vitric and typic Andosols refer to a pedoclimate, alike to the present day, moist in the whole year while the clayey mollic Andosols refers to a past condition, older than 5000 B.P., characterized by a strong seasonal pedoclimate.
Hans Mestdagh1, Roger Langohr2, Nicolas Drozdov3, Paul Haesaerts1 & Vitale Tjecha1, 1IRSNB-KBIN, Vautierstraat 29, B-1040 Brussel, Belgium, 2Soil Science Univ. Gent, Krijgslaan 281/S8, B-9000 Gent, Belgium, 3Inst. of Archaeology and Paleogeography, KNC Presidium, Akademgorodok, 660036-Krasnoyarsk-36, Russia
The Kurtak section, located 250 km south of Krasnoyarsk, provides the most complete soil-sedimentary sequence for the Eemian and the transition to the Early Pleniglacial. The sequence contains the Kamennyi Log Soil (the Eemian stricto sensu) and the Souchoi Log Pedocomplex.
The micromorphological investigation of the secondary carbonates focused on their internal and related distribution. The sparitic crystals of the calcified root cells (CRC) occur in 4 different patterns: 1) in situ, 2) at random distributed in the former root gallery, 3) as clusters in the matrix and 4) as individual crystals in the matrix. These patterns can reflect various degrees of turbation, such as bioturbation, cryoturbation, erosion and sedimentation, within the soil or sediment. The third and fourth pattern have only been recorded in the pure sedimentary horizons. The first pattern is almost completely lacking in Kurtak, the second one is mainly encountered in the paleosoils. In horizons where a strong cryogenic action has been registered, such as creep or frostwedging, CRC are completely lacking.
The amount of micritic lime (ML) in channels and vughs are in positive relation to the environmental evolution of the sequence and its burial by new calcareous sediments. Since the ratio CRC/ML increases during sedimentary build-up, the internal distribution of the infilling of ML and CRC points to very strong leaching conditions at the beginning of sedimentation. We assume that after the weathering of CRC, biomineralisation or physico-chemical precipitation forms micritic crystals. Ultramicoscopic observations (SEM) show this weathering of CRC in the Kamennyi Log Soil. Needle fiber calcite (NFC) - formerly known as lublinite - is only noted in the Kamennyi Log Soil. The absence of this crystalisation in humiferous horizons of the Souchoi Log Pedocomplex may indicate a very dry environment during soil formation.
Throughout the sequence clay galls have been microscopically identified. They form during the drying and cracking of thin layers of mud, e.g. in small ponds, and can be transported over a short distance. Their presence in the parent material suggest considerable variations of dry and wet conditions within a very short period of time during the sedimentary build-up. Probably due to pedogenesis they are almost completely lacking in the Chernozem-like Kammenni Log Soil and the third soil of the Souchoi Log Pedocomplex.
In general the sequence at Kurtak is characterised by a very massive pedality. A detailed mesoscopical study of the degree of pedality (expressed in percentages) showed that several features were lost at the scale of the thin section. Apart from a micro-laminar pedality in a creeped horizon and a micro-granular structure in the Chernozem-like Eemian soil variability of pedality in Kurtak is very low.
* Research founded by the Federal Services for Scientific, Technical and Cultural Affairs: "Actie ter versterking van het wetenschappelijk en technologisch potentieel van de federale wetenschappelijke diensten"
T.D. Morozova, Institute of Geography, Russian Academy of Science, Moscow
Loessic sediments of Eastern Europe periglacial zone contain valuable information on the dynamic (fluctuations) of environment in the Pleistocene. Thus, two major natural-climatic stages have been specified in the Late Pleistocene climatic macrocycle - interglacial (warm) and glacial (cold); they strongly differed in trends and intensity of pedogenesis, sedimentation cryogenic processes. The difference is primarily due to climatic conditions (Velichko, 1982).
The warm stage of the Late Pleistocene macrocycle corresponds to Mikulino (Eemian) Interglacial (125ka). The climate of this interglacial was warmer and more humid than the present-day ones. Soil zonality was conspicuous in Eastern Europe then, it was dominated by soils of forest and forest-steppe genesis (Podzoluvisols, Luvisols, Cambisols, Luvic Chernozems). Therefore, the leading diagnostic horizons of paleosols were argic ones with illuviation coatings, diverse in terms of their fabric and composition.
During the cold stage (Valday Glacial Age) drastic changes in the environment took place. Cryoaridic climate was hardly favourable for soil formation, sedimentation processes were enhanced. Latitudinal zonality didn't exist, it was substituted by hyperzonal landscape pattern. The natural conditions were not homogeneous during the glacial epoch: there were warmings of the interstadial type, extremum of the maximum glaciation stage and cryogenesis stages, that were intermediate between interstadial and thermic maxima.
Soil formation of the Krutitskiy Interval (65-54ka) consisted mainly in spreading of humus-accumulative carbonate-free soils. Micromorphologically these soils could be identified by dark aggregated plasma rich in humus of the humate type. Steppe conditions were dominant, they were similar to present-day forest-steppes of the southern part of Central Siberia. During the Briansk Interval (32-24ka) gley-cryogenic soils with strong ooidal cryogenic-accumulative structure were widely spread. During the Valday glacial maximum (20-18ka) with its strongest (for the whole Pleistocene) climatic cooling and aridization (Velichko, 1973), sedimentation completely dominated soil formation. The advanced sediments accumulation under cryoaridic conditions resulted in the development of a specific loessic soils-sediments (Obruchev, 1948; Gerasimov, 1962). Micromorphological features proper to these formations are: weak organic matter accumulation, microaggregation, weak redistribution of secondary carbonates.
Thus, micromorphological investigations help to clarify the specific character of cold pedogenesis in the periglacial areas of Eastern Europe.
T.D. Morozova, A.A. Velichko, Ye.V. Voskresenskaya, Institute of Geography, Russian Academy of Science
The Upper Paleolithic site Mezhirich is one among important objects characterising ancient people habitats in the periglacial zone. The site is located on the second terrace of the Ros' river (Ukraine). The cultural layer is enclosed in the loess-like loamy sandy deluvium at the depth of 2.95-3.15m; its age is estimated as 14300=300(GIN-2596) - 14700=500(GIN-2593; Paleoclimate of the Late Pleistocene..,1995). Samples for micro- and mesomorphological studies were taken in different parts of the so-called complex IV. The complex includes a round construction made of mammoth's bones with adjacent "housing" holes. Macromorphological data didn't show any distinct boundary between the base of the cultural layer in this complex and the underlying sterile sediment. It is also difficult to detect the contact zone between "housing holes" and the sterile layer.
Preliminary micromorphological data concerning the enclosing depth enable to disclose some features proper only to human habitats.
The following microfabric features were recognised in samples of enclosing (sterile) sediments: light colour, sandy-plasmic-silty elementary fabric, loessic aggregation, weak microaggregation, intraparticle, channel-like and tubular voids, carbonate-clay plasma. Neoformations are presented by carbonates impregnating the micromass, by intercalary calcite and void calcitans. Iron nodules are encountered in the lower part of the depth.
Microfabric of samples from the sediments beneath the living place is peculiar by frequent sand grains (including glauconite ones) in clusters and by bright red silty particles, probably, fragments of ochre.
The material from the "housing hole" fills displays more conspicuous difference as compared to the sterile sediment. Mesomorphologically, the hole fill material is less homogeneous, skeleton grains and quartz particles, specifically, are coarser, they form separate lenses containing coloured grains (including amber), charcoals. Micromorphologically, the material is heterogeneous: there are microzones with massive fabric and those with sand grains clusters in the upper layer. Levels with diffuse distribution of organic material occur in the lower layer, it comprises fragments of bones, coal-sooty mass, dark brown cloddy humus-enriched matter. Presumably the lower level corresponds to the period of living in the site, whereas the upper one - to the later time of the hole filling. Thus, meso- and micromorphological studies enabled to differentiate the enclosing sterile depth and layers affected by human activities.
MUGGLER, C. C. & BUURMAN, P., Wageningen Agricultural University
One representative catena of soils developed on phyllitic rocks in Minas Gerais state, Brazil, was selected for the investigation on the genesis of Inceptisols related to rejuvenated Oxisols. Five profiles were described and analysed starting from a red Oxisol in the top and four yellow Inceptisols down in the slope. Besides chemical and mineralogical analyses, micromorphology turned out as the effective tool to assess the polygenetic nature of these soils. As it is common in humid tropics, the studied soils developed on preweathered materials and are influenced by a complex geomorphic history. Actually the parent material of such soils is a saprolite of phyllite which undergone different phases of weathering and the soil sequences encompass a number of erosion events. The whole saprolitic material is transformed in kaolinite booklets and spherical micro-aggregates of hematite that show an oriented distribution where the rock fabric is partially preserved. These hematite "droplets" are ubiquitously present in all soils and horizons, showing a slight decrease towards the top horizons, being the main relicts of former weathering undergone by the saprolites. The Oxisol shows a strong granular but irregular microstructure that is coalescing into blocks in some parts. The irregular shape and size of the granules appear to be a result of various cycles of bioturbation. Different kinds of iron nodules are present as relict pedofeatures and red mottles appear to be related to the present soil processes. The remarkable relict pedofeature is a brownish yellow clay "nodule" that is very frequent in the B horizon. The Inceptisols have a complex microstructure composed by granular (excremental) domains and subangular blocky or vughy and crack to massive domains. They show the same general features of the Oxisol except for the mottling and the brownish yellow clay "nodules". From the micromorphological data obtained up to now at least two erosion events and related soil formation can be postulated for these sequences. A first erosion stage removed a former yellower material developed on the saprolite leaving behind these yellow clay "nodules". The second event is related to the valley incision that removed the existing Oxisol and ensued the present pedogenesis producing yellow soils.
Mulyanto B., Department of Soil Science, Faculty of Agriculture, Bogor Agriculture University, Jl. Raya Pajajaran, Bogor, Indonesia, Langohr R., International Training Centre for Post-Graduate Soil Scientists, University of Gent, Krijgslaan 281/S8, B-9000, Gent, Belgium
A study is made of the soil (micro-)morphological characteristics along two toposequences in the upper part of a watershed of the Cigudeg area, West Java. The minimum disturbed area is today under cacao and coconut plantation, before it was under natural forest and can therefore be considered as rather unique as more than 90% of the land in Java is under intensive agriculture.
The soil profiles are situated along two transects selected after the elaboration of a detailed topographic map at a scale 1:1000 of the watershed. The parent material consists of andesitic volcanic rocks. The major soil types are clayey, kaolinitic, perudic, isohyperthermic, Typic Humitropepts on the backslope, Oxic Humitropepts on the crestslope and Typic Tropaquents on the footslope.
The soil colour is redder upwards the slopes and the completeness of pedality increases in the same direction. Some soil profiles show a crumb structure in the top horizons, are subangular blocky in the middle horizons and massive in the lowest horizons. The shape of the pedality is partly influenced by the bioactivity, with a crumb pedality in the surface horizons. Crescent striated b-fabric is observed both in top and subsoil horizons, especially in the profiles on crestslope and backslope position, probably related to a long lasting bioturbation by termites.
The decrease of the completeness of the pedality downwards in all soil profiles relates to a decreasing amplitude in wetting and drying. Striated and undifferentiated b-fabrics are dominant on the crestslope, whereas striated, stipple speckled and undifferentiated b-fabrics are dominate on the backslope and footslope. The presence of both striated and speckled b- fabric is most probably related to a rearrangement of the fine fraction, also corresponding to the wetting and drying processes. The dominance of a striated b-fabric on the crestslope and a stipple speckled b-fabric on the backslope and footslope indicates that the arrangement of the fine materials in the soil profiles is poorer downslope. This is probably due to a less strong intensity of wetting and drying down to the lower slope positions. So although this area has a perudic moisture regime, the soil morphology clearly reflects processes related to wetting and drying.
Evidences of clay illuviation occur mainly in the saprolite whose upper boundary is situated at about 120-150 cm depth. In the subsoil horizons above the saprolite, lesser amounts of illuviated clay coatings are observed. Also this is probably due to the disturbance by soil fauna. It can be concluded that in these soils the bioturbation process is stronger than the clay migration process and this down to a depth of about 120- 150 cm. Absence, except for the valley bottom, of features related to redoximorphoic processes shows that no subsurface runoff occurs along these toposequences.
Kathleen NICOLL, Department of Geosciences, University of Arizona, Tuscon, Arizona 85721 USA, HEMA ACHYUTHAN, Department of Geology, Anna University, Madras 600025, Tamil Nadu INDIA
A comparison of soil micromorphological characteristics in paleosols from the Western Desert of Egypt and the Thar Desert of India contributes to our understanding of pedogenesis, soil properties, and the influence of parent materials and climatic change in the vast tract of low-latitude arid lands which span the Afro-Asian region.
In the south-central portion of the Western Desert of Egypt, paleosols have formed from quartz arenite sands sheets which had primary planar and pin-stripe lamination. Beneath the currently-active sand sheet deposits and dunes there are older, pedogenetically-altered sand sheet deposits which lack primary stratification. At the surface of this soils there is a thin silt layer and a vesicular horizon with obvious peds, columnar structures and shrinkage cracks which are filled with wind-blown sand. These paleosols are alkaline and are characterized by a lack of humus and an abundance of airborne salts and carbonates, as well as occasional authigenic evaporites (gypsum, anhydrite, halite). The soils vary in morphological complexity with increasing age, with the oldest soils exhibiting incipient carbonate cementation.
In the eastern portion of the Thar Desert of India, paleosols have formed from stabilized sand dunes and sand sheets, the sands of which are derived from Aravallis Precambrian metamorphic rocks and reworked alluvial sediments. The paleosols are alkaline but lack airborne salts and authigenic evaporites. Compared to the soils from the Egyptian Sahara, the Thar soils are much richer in pedogenic carbonates and exhibit complex cement morphologies. Older Thar soils show distinct evidence that easily-weathered iron-bearing minerals originally present in the parent materials (e.g. horneblende and plagioclase) degrade to iron-rich clays in situ and also form haloes around more resistant minerals within the soil.
Detailed micromorphological and petrological study of soils from both regions confirms progressive changes in the mineralogy, texture, and chemical compositions of successively-older soils. Pedogenic alteration includes bioturbation, the addition of mechanically-infiltrated minerals in channel voids, precipitation of authigenic quartz, calcite, iron oxides, and aluminum. In both regions, the older soils have an increasing amount of iron-rich clay-bridging, channelization, and carbonate cementation.
Both the Western Desert of Egypt and the Thar Desert of India have experiences several environmental changes throughout the Quaternary. Paleosols buried by aeolian sands provide evidence that these arid landscapes formerly enjoyed wetter conditions, and were stable long enough for vegetative colonization to proceed. Deposition of the sand sheet parent materials and dune sands occurred at times when the deserts experienced deflation. Radiometric dating and archaeological correlation indicate that pedogenesis was most effective at times when the local climate was wetter due to strengthened summer monsoonal circulation patterns. As a result, intense pedo-complexes have formed in the eastern Thar Desert, whereas in the Egyptian Sahara, the formation of incipient pedo-complexes has been delimited by a comparable lack of water, high input of aeolian sand, and a more continental geographical location.
Th. POETHSCH, Dept. of Geography, University of Hamburg, 20146 Hamburg, F.R.G.
The results presented are the product of an interdisciplinary cooperation between soil scientists and archaeologists. Together they examined soils of old settlement, that had been occupied from prechristian times until the early middle ages.
Apparently a high concentration of phosphates in the soil is connected with the long anthropogenic influence. The soils is marked by the presence of vivianite and more so through pseudomorph alteration products of that mineral.
Very noticeable and characteristic also, especially in phasecontrast microscopy are deposits of silica-gel on the inner surfaces of soils. The gel exists either as free microlamellae or together with clay minerals, then in the form of "Mischkorper" (mass consisting of the two substances intimately mixed). The origin of the silica-deposits is obviously connected with the particular substrate of the soil formation.
The above microscopic findings were confirmed through chemical analyses using a microprobe.
M.C.RABENHORST1 AND J.N.SHAW2. 1Department of Agronomy, University of Maryland, College Park, MD 20742 USA, 2Department of Crops and Soils, University of Georgia, Athens, GA 30602, USA
Unconsolidated calcareous sediments (marls) have been identified in portions of the humid Eastern USA (Mean Temp 12C, Ann. Ppt. 1000 mm). Soils in these sediments typically occur in alluvial (floodplain) landscape positions and have been considered to be Rendzina soils (carbonatic, Fluvaquentic Haplaquolls or Hapludolls). Adjacent soils occupying upslope portions of the landscape are non-calcareous residual soils similar to Terra Rossa (Typic Hapludalfs), and are underlain by Paleozoic limestone. Radiocarbon analysis and prehistoric artifacts date the marl sediments as early to mid-Holocene (8500-5000YBP). The highly calcareous nature of the sediments is unusual for soils of udic moisture regimes. Several hypotheses for their origin were examined.
Following extensive reconnaissance evaluation, seven sites were examined in detail, including thorough soil characterization and micromorphological analysis (1). These soils demonstrate an irregular decrease in organic carbon with depth (buried A horizons) and have low bulk density (1.0 g cm-3). Extremely high CaCO3 content of the sediment (600-1000 g kg-1 CaCO3) mitigated against the postulation that super- or nearly saturated groundwater permeated alluvial (low carbonate) sediments and precipitated carbonates. The absence of an upstream source for carbonate rendered untenable the hypothesis that the carbonate sediment was primarily detrital.
Micromorphological examination demonstrated an abundance of calcified tissue from a subaerial aquatic algae in the family of Charophyceae, known to be a prominent marl forming algae. Oblique sections through thalli were characteristic of these algae and proved to be diagnostic. Biogenic components also included portions of various bivalves and gastropods. In deeper portions of the marl (> 1 m), readily identifiably biogenic components comprised up to 10% of the volume within a crystallitic b-fabric. Because the Chara sp. only occur in ponded or shallow water environments, it was deduced that the sediments must be of biogenic origin and formed within low energy, shallow freshwater habitats.
Greater alteration of the biogenic forms in the upper horizons was evidenced by common micritic nodular forms. Identifiable secondary carbonates (sparite and associated forms) were also more evident in the upper horizons. These pedogenic alterations were likely promoted by subaerial exposure. The identification of pedogenic carbonates led to the recognition of calcic horizons in these soils. The stratigraphic history of the marl derived soils appears to show periods of biogenic deposition punctuated by periods of subaerial exposure, during which time pedogenic alterations occurred.
Literature Cited.
(1) Shaw, J.N. 1993. Soils developed in freshwater marl sediments in the Hagerstown (Great) limestone valley. M.S. Thesis. Univ. of Maryland. USA. 156 pp.
A.V. Rusakov, Biological Research Institute, St-Petersburg University
In the course of soil surveying dark coloured soils on non-calcareous loams (Phaeozems?) have been encountered in the area dominated by sod-podzolic soils. They are restricted to flat surfaces at low levels of Borisoglebsk upland, and their profile comprises the following horizons: Ap-A1-Ah-AB-B1-B2-BC. The topsoil including the buried Ah horizon, is 52cm deep, its colour changes from dark grey to almost black in the Ah horizon, which is also conspicuous by its fine granular structure. Clay-organic coatings on ped faces occur up to the depth of 130cm. Ap horizon has 2.18% Corg., and fulvic-humic type of humus; eluvial-illuvial redistribution of particles <0.01 and <0.001mm is manifested in the upper 37cm, i.e. at the A1/Ah boundary. Ah horizon has the highest CEC values and minimum magnetic susceptibility.
In thin sections, the Ap horizon is heterogeneous: greyish-brown almost isotropic microzones alternate with light-brown ones, poor in humus, with scaly b-fabric. Moderate pedality (2-3 levels of aggregates), elevated porosity; plant residues, including carbonified, Fe oxides mottling. The Ah horizon consists of dark-brown and black isotropic, and brownish-grey weakly anisotropic microzones. Mull humus, humus-clay plasma; rounded, aggregates of the third level predominate, packing voids, rounded ferruginous concretions. The AB horizon is yellowish-brown, has striated and porostriated b-fabrics, few Fe mottles. Illuvial horizon comprises yellowish-grey and brownish-yellow mottles, it is compact, its b-fabrics are presented by poro- and dendritic-striated types, iron-clay plasma.
Thus, micromorphological and other data indicate the effect of former hydromorphism on the described paleosol origin. The Ah horizon is similar to that of humus-gley soils, and is supposed to be a remnant of the Atlantic optimum, when it evolved due to humid climate and weakly dissected relief. The second humus horizon of sod-podzolic soils occurring in well drained sites is of the same age.
S.A. Shoba, V.O. Targulian, M.I.Gerasimova, 1.Moscow State University, 2.Institute of Geography, RSA, Moscow
Soil systems are distinct from other exogenic systems due to their capacity to generate in situ the solid products of long-term functioning of the terrestrial ecosystems.
The solid phase of a soil system (morphology at macro-, meso, macro- and submicro-levels) is the only reliable record of soil functioning, formation and evolution in time and space. The integrity of solid phase properties comprises the total memory of soil system, which can be subdivided into: a)lithomemory (lithomatrix) inherited from the parent material, and b)pedomemory (pedomartix) evolving within the lithomatrix and gradually superimposing or replacing the lithomemory. The pedomemory should be also subdivided into inherited evolutionary memory of paleoenvironments and paleopedogenesis, and recent memory of current environment and pedogenesis.
Thus, the whole pool of information recorded in the soil solid phase is usually very intricate, heterochronous, polygenetic.
It is worth emphasizing, that contrary to the "book-wise" recording in sediments, the soil system displays the "palimpsest-wise" record (memory). This means, that the chronosequences of events and processes are recorded "at the same page", i.g. within the same mass of soil material.
The most basic goal of soil morphology is the correct discrimination, decoding and interpreting the information memorized by different material and organizational carriers within the solid phase in order to understand the essence of natural soil processes and their man-induced shifts, to reconstruct the paleo- and recent environments.
We presume, that one of the forward-looking ways to extract the information recorded in the soil system memory is the application of the hierarchical approach to the studies of solid-phase carriers of this information. This means investigation of composition, arrangement and transformations as they are expressed in soil morphology - soil volumes at different organizational levels, such as: individual particles (crystalline and amorphous)- plasma/skeleton - peds - morphons - horizons and trans-horizon vertical zones - soil body (pedon).
Each level in the hierarchy can (in a conceptual model) record, accumulate and store a specific kind of information. On each level the chosen morphological unit (or volume) can basically record different information on its interfaces (IF) and internal masses (IM). The IF information is mostly operative, labile, fragile, short-living, quickly recorded and easily deleted. The IM information is more conservative, stable, long-living, slowly recorded and hardly obliterated (Kozlovskiy, Goriachkin, 1996).
The IM of fabric units play the role of "refugiums" on many levels - they contain records of paleopedogenesis and paleoenvironments (IM of peds, the nodules, concretions, micropans, etc.).
The multy-layered IF (cutans within large fissures or pores) can remember the events and processes sequences; they can be dated by various methods, so that information about chronosequences of intrasoil processes and environmental changes might be decoded.
The potential information which can be recorded on IF and IM on each hierarchical level of soil solid-phase arrangement may be very diverse in its essence, density of record, volume and quality, simplicity or superposition, etc.
Systematic morphological study of the IF and IM of soil volumes on each level on the whole set of levels from the submicro- one (IM and IF crystals) to the macromorphological (IM and IF boundaries of horizons within the pedon), combined with microchemical and mineralogical studies and possible dating of pedofeatures, can give us the most complete information image of the soil system memory.
I.A. SOKOLOV, V.V.Dokuchaev Soil Science Institute, Moscow, Russia
Red ferrallitic soils and weathering crusts, plinthite, and laterite horizons are considered as a typical phenomena of tropical pedogenesis and formation of weathering crusts. Their genesis is a subject of discussions. Two hypotheses of their origin, i.e. the soil-hypergenic, and the hydrothermal one are the most popular.
The system of field and laboratory methods, including visual observations, interpretation of remote sensing data, and macro-, meso-, and micromorphological studies was applied to verify both hypotheses. All levels of organization of the pedosphere - soil cover, soil profile, genetic horizons, morphons, peds, mineral and organic inclusions and neoformations were investigated. The range of studied objects includes typical tropical and subtropical mottle-coloured ferrallitic soils with laterite and plinthite horizons and modern hydrothermal weathering crusts, and the soils which form in these crusts (Indochina, Polynesia, Caucasus, Kamchatka). Nondisturbed samples, organic and mineral inclusions and neoformations, and thin sections made from them, as well as coarse fraction of the fine earth were studied under the microscope.
The results obtained can be reasonably explained within the frames of the hypothesis of hydrothermal origin of studied phenomena and do not support the hypothesis of their soil-hypergenic genesis. This conclusion is also supported by the data derived from the studies of rock samples, fine earth and clay fractions of soils by means of modern chemical, physicochemical, and physical methods.
Pedogenic processes develop within the initially differentiated into genetic horizons hydrothermal weathering crusts. The high degree of weathering of the initial parent material provides its resistance to pedogenic weathering. The latter is manifested in biogenic amorphisation of clay minerals and in the formation of the "elueat" (strongly leached under the effect of soil biota) superhorizon.
I.A.SOKOLOV, V.V.Dokuchaev Soil Science Institute, Moscow, Russia
Russian Plain is the territory, where genetic soil science was developed; probably, from genetic viewpoint, soil cover of the plain is one of the best studied objects on the Earth. However, it is the Russian Plain, where four natural phenomena, whose origin is still subjected to discussion in spite of many years of investigations, occur. These phenomena are: (a) mantle loams; (b) texturally-differentiated profile; (c) pale-podzolic soils (texturally differentiated soils with pale (straw-like) colour of the eluvial (impoverished in clay) horizon; (d) second humus horizon. For a long time the problems of genesis of these phenomena were studied separately from each other. Our investigations was shown that all these phenomena are spatially and genetically interrelated. Therefore, we tried to elaborate such genetic concept that would consistently explain the total integrity of facts related to all these phenomena.
All the main areas of these phenomena on the Russian Plain were studied. The key sites, such as the soils of stationary research stations and training centers, as well as the soil profiles that had been demonstrated (as typical) to the participants of various national and international congresses and conferences, were specially studied. The bulk of field and available laboratory data was analyzed. The basic of the system of methods was formed by visual morphological studies of soils on all levels of organization of the pedosphere - from soil-stratigraphical method of tracing the "behavior" of the sequence of soil horizons in space to micromorphological investigations of soil samples.
The results obtained enabled to formulate the following conclusions about the origin of these phenomena.
(1) Mantle loams represent one of the types of specific blanket deposit inherent in glacial and periglacial environment and formed by a complex system of processes of formation and destruction of ice-enriched mineral sediments.
(2) Texturally-differentiated profile is inherited from soil-forming rocks; it is not the result of pedogenic processes.
(3) Pale colour of the upper horizons of Pale-Podzolic soils is inherent from the colour of initial soil-forming rock.
(4) Second humus horizon is the buried horizon of the Late Pleistocene - Early Holocene soil.
The role of micromorphological methods is especially significant for the studies of genesis of texturally-differentiated profiles, pale-podzolic soils, and second humus horizons.
M.R.USAI1 AND J.B.DALRYMPLE2, 1Dept. of Biology, University of York, 2Dept. of Soil Science, University of Reading
Difficulties in the identification of paleosols and of their associated, burred paleogroundsurfaces in both archaeological and "natural" sites result from the similarity of many weathering and pedogenesis features in altered sediments and soils. Further, soils properties are frequently transitory and liable to postburial deterioration and transformation, with the additional possibility of overimposition of postburial and preburial features. Solutions can often be achieved through the identification of pedon heterogeneity and catenary relationships resulting from soil /water/ slope interaction (Valentine and Dalrymple, 1976). Pre-Pleistocene old buried paleosols and their associated paleogroundsurfaces were identified in Sardinia at Serri and Siddi. They were interpreted on the basis of their three-dimensional relationships, not by their micromorphological properties alone, but in conjunction with a parallel field work and spectrochemical analysis (SEM and XRF). The younger, archaeological sites in Northumberland, Northern England - post Neolithic paleosols buried with Bronze Age cairns and pre-Roman paleosols near the Hadrian's Wall vallum were identified and interpreted through field work aided by micromorphology. At all other archaeological sites studied in Northern England, micromorphology on its own did not enable paleosols to be identified and distinguished from weathered "natural" or human deposited sediments.
L.T.WEST1, K.S.LAWRENCE2, A.A.DAYOT3, L.M.TOMAS3,R.D.YECK2,
1 Department of Crop and Soil Sciences, University of Georgia, Athens, Georgia, USA
2 USDA-Natural Resource Conservation Service, Athens, Georgia and Lincoln, Nebraska, USA
3 Philippine Bureau of Soil and Water Management, Manila, The Philippines
Eleven pedons were sampled across a volcanic slope on the island of Mindano in the Philippines to provide basic resource information and to evaluate relationships between soil characteristics and position on the volcanic slope. Elevations in the area range from 300 to more than 2100 m at the peak of the dormant volcano. Three upland physiographic provinces were identified in the area, mountains, upper footslope, and lower footslope, from aerial photo interpretation of elevation and local topographic relief. Parent material for all pedons was volcanic ash.
In the lower footslope province, all peons were Oxisols. The soils were clayey with A horizon clay content ranging from 60 to 70% and >75% clay in subsoils. Citrate-dithionite extractable Fe (Fed) was >5% in all horizons and was relatively uniform with depth. Acid-oxalate extractable Fe (Feo), Si (Sio) and Al (Alo) contents were low, however, indicating that these soils have little residual characteristics of their ash parent materials. The dominant clay mineral in these soils was halloysite. In thin section, A and B horizons of these soils had strongly developed granular microstructure and considerable evidence of bioturbation. The groundmass in all horizons had undifferentiated b-fabric and no clay coatings or other pedofeatures were identified.
The two pedons sampled in the mountains province had a thin capping of recent ash, and properties of these soils indicate they were less weathered than those on the lower footslope. Subsoil contents ranged from 30 to 60%. These soils had relatively high Fed contents, but Feo/Fed ratios in these pedons were appreciably higher than those in pedons from the lower footslope. Like the lower footslope pedons, clays were dominantly halloysite, but Sio and Alo contents suggest that minor amounts of allophane or other weakly crystalline components were also present. Because of the presence of these weakly crystalline components, clay activity was too high for these soils to classify as Oxisols. Microstructure of soils in this province was weakly developed. Zones of weathering were observable in thin-section with the most weathered zones being along planar voids and fractures. The b-fabric of groundmass was undifferentiated, but coarse opal grains were present in most horizons.
Soils on the upper footslope had properties intermediate between those on the lower footslope and those in the mountains. Pedons near the transition to the mountains had a thin capping of recent ash that was not present on pedons at lower elevations within this province. Other properties of pedons in this province, including micromorphological characteristics, suggested greater weathering at low elevations and less weathering at high elevations within the province.
These soil development relationships suggest the soil have developed in multiple-age ash deposits. The boundary between the mountains and upper footslope provinces approximates the limit of the most recent deposit. Though soil development in upper horizons is similar for soils in the upper and lower footslopes, depth of weathering suggests that soils on the upper footslope may be developed in an ash younger than that on the lower footslope.
Utami S.R., B. Mulyanto, E. Van Ranst and G. Baert, ITC for Post-graduate Soil Scientists, Universiteit Gent, Geologisch Instituut, Krijgslaan 281, 9000 Gent, Belgium
Five highly weathered profiles were selected along a toposequence (P3 on top of the hill, P2 and P4 on the midslope, P1 and P5 on the footslope) in Pleihari, South Kalimantan, Indonesia, to study the mineralogical and micromorphological characteristics and to evaluate these characteristics in relation to the landscape position. The hill is an intrussion of peridotite and associated igneous rocks in quartz sandstone and conglomerates.
Besides the determination of the physical-chemical properties, the mineralogy of the clay and the silt fraction was studied with XRD and the fine sand fraction (50-500 №m) by optical methods. The micromorphological properties were studied in thin sections.
Mineralogically, all profiles are characterised by the dominance of kaolinite, iron and aluminium oxyhydrates and quartz in the clay and the silt fraction; 2:1 clay minerals are only found in trace amounts. A small amount of quartz occurs in the clay fraction. Kaolinite is quite important in the silt fraction. The fine sand fraction of all profiles is dominated by opaque minerals (94-98%) in the heavy fraction and quartz (90-99%) in the light fraction. This mineralogy points to strongly weathered materials. A small admixture of unweathered minerals, however, is observed in profiles on the footslope.
Micromorphologically, profiles P2, P3, P4 and P5 have typical characteristics of Oxisols : the coarse fraction is dominated by quartz and opaque minerals, the micromass has an undifferentiated b-fabric and pedofeatures consist mainly of iron nodules and excrements. The rock fragments mainly consist of interlocking quartz grains, pointing to quartzitic sandstone. Undifferentiated b-fabric is due to low birefringence of kaolinite, masking effect of iron oxyhydrates and pedoturbation. The microstructure is moderately developed subangular blocky with planar and compound packing voids, channels and few fissures. The subangular blocky structure is developed due to natural compaction of the partly granular microstructure. A loose microped structure is only found in profile P2. Profile P1, situated in the lowest position, is distinguished from other profiles, by having a yellowish brown micromass with striated b-fabric and clay coatings.
The relationship between mineralogical - micromorphological characteristics of the studied soils and their landscape position is very weak, except for the soil in the footslope position which tends to have (1) a higher goethite/hematite ratio, resulting in a rather yellow micromass, and (2) a higher amount of 2:1 clay minerals which is at the origin of a partly striated b-fabric and clay coatings.