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1.
A study was conducted of the Mediterranean Red soils of a region in Central Western Spain with a goal of describing the relationship between their main characteristics and the age of the geomorphic surfaces over which they have developed. The main macromorphological characteristics of the soils were analyzed, with a statistical study of the analytical data on 70 samples of Mediterranean Red soils. The oldest surfaces contain Palexerults and Ultic Palexeralfs, Calcic Rhodoxeralfs, Calcic-vertic Palexeralfs, Typic Rhodoxeralfs, Typic Palexeralfs, Vertic Haploxeralfs and Typic Haploxeralfs have been observed in a chronosequence on terraces of the River Tormes. The soil typology changes with the age of the surfaces, from soils with a sharp textural contrast at the upper limit of the argillaceous horizon, with a dark red very clayey and very thick Bt horizon (on the oldest surface) to not very thick brown soils without a clear clay illuviation and with a lower content in clay (on the youngest surface).The effect of recent erosion on the morphology of the soils located on a single surface has caused new soils to form superimposed on pre-existing soils. 相似文献
2.
One of the significant features of loess-derived soils in Kansas is the occurrence of clay-rich subsurface horizons above a layer enriched with pedogenic carbonates. In order to examine the extent of clay increase and pedogenic carbonate enrichment in a precipitation gradient, ten soil profiles from three different precipitation regions were studied using micromorphological and mineralogical techniques. The precipitation gradient was divided into three groups: 400–550 mm, 550–750 mm, and 750–1100 mm regions. The objectives were to (1) understand the cause of clay orientation in clay-rich horizons (2) investigate the reasons for the clay increase, and (3) observe the interaction of clay and pedogenic carbonate accumulation features along a precipitation gradient in Kansas. Although clay films were identified in the field for soils in the 400–550 mm regions, illuvial clay films were not observed in thin section analysis. The clay accumulations mostly occurred as grain coatings. The rest of the clay accumulations observed were very thin, striated, and mostly associated with voids. The argillic horizons had a granostriated b-fabric, which indicates stress orientation of micromass caused by high shrink–swell activity. Thick and continuous illuvial coatings were observed in the buried horizons of paleosols. In the other two regions where precipitation exceeds 550 mm, illuvial clay coatings with strong orientation were observed along with thin and striated stress-oriented clay. Both types of clay orientations exceeded 1% of the cross-sectional area for the thin section. Although illuvial clay features and pedogenic carbonates were observed in all soils at approximately the same depth, complete obliteration of clay coatings was not observed in these horizons. In-situ weathering of biotite was one of the reasons for the clay increase in all soil profiles. In all soils studied, the clay increase and cause of clay orientation cannot be attributed to a single genetic process or event. Both illuviation and shrink–swell activity were involved in the orientation of clay. Although orientation of clay and pedogenic carbonates were observed in all soils at approximately the same depth, the decomposition of clay coatings was not observed in these horizons. 相似文献
3.
Micromorphological examination of the paleosols (50–10 ka) developed in alluvial fan deposits of the NW Himalayas and the bordering polygenetic soils (mainly Holocene) of the Gangetic Plains has been used to differentiate the pedosedimentary features indicating climatic changes during late Quaternary time. The paleosols within rapidly aggrading sediments of the alluvial fans of the Dehradun valley resulted in response to the reduced rate of sedimentation and climatic changes and correspond to the MIS3 and MIS2 stages. Distinctive micromorphic features of these paleosols provided the details of the prevalent pedogenesis in response to the paleoclimatic changes during 50 ka. Microfabrics of these paleosols show reorganization of the pedality from massive and/or subangular blocky to platy and prismatic structures, strong to very strong mobilization of the plasma, different types of textural pedofeatures along with faunal activities. These pedofeatures are indicative of cold-humid climate with subsequent change to even colder but drier conditions during the last Glaciation. Comparison of the micromorphological characters of the paleosols of the NW Himalayas and the polygenetic soils of the Gangetic Plains show the same degree of soil development indicating 5–10 ka pedogenic intervals in alluvial fans of the Dehradun Valley. However, the difference in their pedofeatures is attributed to different pedogenic environments. The paleosols of the Dehradun Valley show predominance of the illuvial features with superposed impure silty clay on earlier clay pedofeatures and banded clay fabric features without any pedogenic calcium carbonate. The bordering Gangetic Plains are covered with polygenetic soils developed on stable surfaces and are < 13.5 ka. These surficial soils developed during the period marked by deglaciation and correspond to MIS1 stage. These are defined by the juxtaposition of different illuvial pedofeatures along with pedogenic calcium carbonate. This study suggests that formation of the paleosols in NW Himalayas was mainly controlled by warmer intervals during the last glaciation and the movement along the adjacent thrusts. While fluctuating climate punctuated with humid–semiarid–humid conditions played a major role during the formation of soils on the Gangetic Plains in Holocene that favoured illuviation, calcification and dissolution of pedogenic carbonates in the polygenetic soils. 相似文献
4.
A paleosol with Mousterian tools in aeolianites at the Habonim site (Carmel Coastal plain, Israel) is a complex pedosedimentary sequence which records a succession of soil-forming episodes and stages of coastal dune instability. We identified three strong soils and one accretionary soil within Mousterian pedocomplex via micromorphological techniques, coupled with FTIR and SEM/EDAX. In the lowermost, red sandy soil (hamra) in Unit IV, decalcification led to the formation of micritic coatings, disrupted by faunal churning, while rubefication resulted in red ferric segregations. Illuviation of ferruginious clay in the form of clay coatings is lacking, probably due to its strong incorporation into the matrix. Redox features were intensified in the pseudogley of the next stage (Unit III). Polyphase calcitic features here indicate that illuviation of clay pre-dates illuviation of micrite and its later recrystallization into sparitic calcite. Further deterioration of drainage conditions and increased accumulation of fine particles led to the formation of vertisol (Unit II). Paleovertisol is characterized by a maximum of clay, stress-originated microfabric, abundant Mn precipitates and calcitic pseudomorphs. The peak of landscape instability occurred later and is recorded in the upper Unit I, in which micromorphological signs of colluvial and aeolian processes are juxtaposed with various ferric accumulations, associated with gleying. The final episode occurred at a time of climatic instability, devegetation, and probably, a simultaneous groundwater rise in the littoral zone. 相似文献
5.
A. V. Novikova 《Eurasian Soil Science》2007,40(7):729-739
Solonetzic soils are widespread in the south of Ukraine; some of them are represented by low-sodium solonetzes whose diagnostics is complicated by the absence of correspondence between the low content of exchangeable sodium and the clearly pronounced features of the illuvial solonetzic horizon. The statistical treatment of available literature, personal materials, and the materials of soil surveys in the south of Ukraine demonstrated that the diagnostics of low-sodium solonetzes should be based on the assessment of the degree of illuviation in the soil profile. It was shown that the degree of correlation between the content of exchangeable sodium and the degree of illuviation of the soil profile varies in dependence on the size of the statistical sample and differs for the low-sodium and medium-sodium solonetzes. Two scales characterizing the degree of soil illuviation were developed for these soil groups. It is suggested that these scales should be applied during soil surveys in the areas with solonetzic soils. 相似文献
6.
S.‐H. Jien Z.‐Y. Hseu Y. Iizuka T.‐H. Chen C.‐Y. Chiu 《European Journal of Soil Science》2010,61(3):319-332
Well‐developed placic horizons have been found in subalpine forest soils with large clay contents in Taiwan. We investigated their formation processes in five profiles in a subalpine ecosystem of northeastern Taiwan, using scanning electron microscopy (SEM), energy‐dispersive spectrometry (EDS), electron probe microanalysis (EPMA), differential X‐ray diffraction (DXRD) and chemical extractions. The placic horizons, ranging from 3‐ to 17‐mm thick, always occurred above argillic horizons with abrupt changes in pH and texture between the two horizons. When fully developed, the placic horizons were clearly differentiated between upper and lower sub‐horizons. EDS and chemical extractions revealed that the cementing materials in both were predominantly inorganic Fe oxides. However, contents of aluminosilicates and organically complexed Fe and Al were greater in the lower than in the upper placic sub‐horizon. Results of EPMA indicated that interstitial fine materials in the upper placic sub‐horizon were composed mainly of Fe oxides, whereas Fe oxides were codominant with illuvial clay in the lower sub‐horizon. These analyses identified the migration of Fe and clay as major formation processes in both sub‐horizons. We hypothesize that there is a pedogenic sequence that starts with clay illuviation, followed by podzolization. The resultant textural and permeability differentiation reinforces the tendency to profile episaturation that is already inherent from the heavy rainfall and clayey surface soils. Topsoil Fe is therefore reduced and mobilized, and then illuviated with clay and organically complexed Fe/Al to initiate the lower placic sub‐horizon. The poor permeability of this layer reinforces the moisture conditions in the surface soils, and the further reduction, illuviation and deposition of inorganic Fe to form the upper placic sub‐horizon. 相似文献
7.
Data are presented on the physicochemical composition and specific macro-, meso- and micro-morphological features of automorphic
soils formed on silty loams in the northern and middle taiga subzones of the Timan Ridge. These soils have a texture-differentiated
profile and are well aggregated, which is manifested at all levels of structural organization of the soil mass. The morphological
structure of the middle soil horizons is characterized by the presence of specific nongleyed cryometamorphic horizon CRM.
Its formation is due to the development of long-term seasonal cryogenic processes in relatively deep (up to 40 cm) light and
medium loam deposits under conditions of the northern and middle taiga subzones. The processes of cryometamorphism, combined
with Al-Fe-humus and textural differentiation, result in the formation of podzolic, iron-illuvial, cryometamorphic, and textural
horizons (O-E-BF-CRM-BT). The textural horizons have a set of micromorphological features indicating that recent clay illuviation
is a weak process. 相似文献
8.
The soils of the Golan basaltic plateau were surveyed and analyzed. Soils on uneroded plateaus range from montmorillonitic calcareous Reddish Brown Grumusols in the semi-arid areas through noncalcareous Brown Grumusols in the sub-humid areas to Brown and Red Mediterranean Soils with typical argillic horizons and dominance of kaolinitic clay in the humid parts of this region. Protogrumusols and basaltic Lithosols are found in eroded places. Volcanic cone soils in the humid Golan parts range from tuffic Regosols on the youngest cones and most eroded areas through tuffic Red Mediterrranean silty clay loam and silty loam on less eroded areas to tuffic Red Mediterranean clays on the older volcanic eruption sites and comparatively stable slopes.The weathering of the basalt is comparatively very slow, especially in the drier upland areas of the southern Golan. The weathering of the pyroclastic materials, on the other hand is fast, due to the great internal surface of this parent material.The various soils exhibit different leaching stages. A gradual disappearance of lime, decrease in pH values, increase in exchangeable H+ and a shift from montmorillonite clay dominance to kaolinite and similar clay types expresses the increase in the leaching degree from the dry areas to the moist ones.The textural profile of Golan soils depend on clay content and type. A soil sequence commencing with self-mulching Grumusols through various intermediate types to typical ABC Red and Brown Mediterranean Soils may be distinguished along climatic, time and drainage gradients. 相似文献
9.
Polygenetic Soils of the North-Central Part of the Gangetic Plains: A Micromorphological Approach 总被引:1,自引:0,他引:1
Micromorphology indicates that soils of the central part of the Gangetic Plains are polygenetic. They occur on surfaces originating at 13 500, 8000, 2500, >500 and <500 BP (QGH5 to QGH1, respectively). The QGH5 soils on upland interfluves show degraded illuvial clay pedofeatures of an early humid phase (13 500–11 000 BP) and thick (150–200 μm) microlaminated clay pedofeatures of a later humid phase (6500–4000 BP). The earlier clay pedofeatures were degraded by bleaching, loss of preferred orientation, development of a coarse speckled appearance and fragmentation, whereas those of the later phase are thick, smooth and strongly birefringent microlaminated clay pedofeatures. The illuviation was more extensive during the later phase, as indicated by enrichment of groundmass as discrete pedofeatures of clay intercalations. Pedogenic carbonate was formed during the intervening dry phase from the early Holocene to 6500 BP. It forms irregularly shaped nodules of micrite and diffuse needles with inclusions of soil constituents. The subsequent change to wetter conditions caused dissolution–reprecipitation, which resulted in partial to complete removal of carbonate from soils over large areas. 相似文献
10.
Development of texture contrast soils by a combination of bioturbation and translocation 总被引:1,自引:0,他引:1
Soils and weathering profiles in a wide variety of parent materials and environmental settings exhibit coarse-over-fine vertical textural contrasts. Where these cannot be attributed to inherited texture contrasts or erosion–deposition, the most common explanations are based on translocation (eluviation–illuviation) which removes clays from surface layers and deposits them in the subsoil; or bioturbation, where preferentially fine material is delivered to the surface by organisms, from whence erosional winnowing creates a coarse surface layer. In some soils of the lower coastal plain of North Carolina, U.S.A., neither explanation is sufficient to explain the observed texture contrasts. A heuristic model based on a combination of translocation of fine material from surface to subsoil, and bioturbation-driven delivery and recycling of material to the surface can explain the observed vertical textural contrasts. The key elements in the model are coastal plain sediments which include some fine material; eluviation–illuviation by percolating water; delivery of additional fine and mixed grain size material to surface by bioturbation, making it available for translocation; concentration of fine material originally scattered throughout the parent material in a B horizon; and maintenance of vertical moisture fluxes by bioturbation. The model is supported by morphological evidence of the key mechanisms, argillic horizons that are finer than both the surface layers and underlying parent material, evidence that argillic horizon formation is not limited by the rate of clay synthesis, and the absence of texture contrasts in nearby soils formed from dune sands which lack fines. 相似文献
11.
Whether some soils observed in Morocco prior to the 1966 conference on Mediterranean soils held in Madrid had argillic horizons was the subject of active discussions. Textural differences between A- and B-horizons were obvious. Consequently, individual horizons of a number of profiles were sampled for micromorphological study. No clay films were observed in thin sections representing the B-horizons free in carbonate. Peds had pressure faces and internal striations in the matrix. Microchurning and swelling and shrinking are believed to have obliterated evidence of clay illuviation in the B-horizons, but clay coatings were observed at greater depth in well-developed Bca-horizons. 相似文献
12.
13.
The effects of the migration of two soil constituents into illuvial horizons is described by a set of equations. Differential movement of clay fractions during illuviation causes changes in the fine to total clay ratios in A and B horizons. A mathematical model is used for the interpretation of clay fraction data in order to estimate the degree of profile development, the amounts of fine and total clay which have moved, and to determine the original composition of the parent material. No bulk density data of the soil horizons are necessary for the computation. The equations can be programmed on desk calculators. Comparison with measurements on Alfisols in temperate regions was found to be satisfactory. 相似文献
14.
The classification of solonetzes (including the scheme developed by Fridland et al.) does not take into account the thickness
of the solonetzic horizon and the depth of the lower boundary of the illuvial horizon. The degree of solonetzicity is only
judged from the content of absorbed sodium in the illuvial horizon. For the diagnostics of solonetzes, the authors propose
two additional characteristics: the degree of illuviation (weak, medium, strong, and very strong (for solonetzes)) and the
depth and kind of illuviation (typical medium-profile, lithogenic medium-profile, deep-profile, and high-profile). As an example,
data on some soils of Ukraine are presented. 相似文献
15.
Data from particle-size analyses were used to determine the relative importance of the four mechanisms proposed to explain the development of strong textural contrast in the end members of four chronosequences. The mechanisms proposed were sedimentary layering, in-situ chemical weathering, clay illuviation and physical breakdown.Depth functions of fine clay: total clay ratios and detailed particle-size distributions at ø intervals from 0.6 μm to 2000 μm indicated that there had been a marked increase in fine clay in the B horizons of the older soils of each sequence, a result consistent with, but not proving, a clay illuviation hypothesis. Cumulative particle-size distribution indices showed that most profiles had texturally uniform parent materials. Changes in the ratio fine silt : total silt with depth were slight for all but one profile, indicating no significant contribution to the clay fraction by in-situ chemical weathering of the silt fraction.From changes in the depth functions of gravel with time, it was concluded that physical breakdown had occurred but that it had not been responsible for the development of the textural B horizon. The rate of disintegration was particularly high early in pedogenesis, preceding the development of texture-contrast. Breakdown contributed fines to the whole solum and was not generally any more intense in one horizon than another. Grain counts of rock fragments in the medium sand range lent support to this conclusion.Changes in the particle-size distribution of quartz from 0.2 μm to 2000 μm indicated that the contribution to the clay fraction from physical disintegration was only slight. 相似文献
16.
Field studies of Duplex soils (Red and Yellow Podzolics or Ultisols) on hillslopes in the Sydney Basin show that their primary morphological feature (the texture contrast between A and B horizons) is explicable in terms of differential bedrock alteration combined with downslope movement of the coarser grained materials as a discrete surface layer. The more usually invoked processes of clay illuviation and/or clay destruction are of no more than minor importance in the genesis of Duplex soils in this area. 相似文献
17.
The Pleistocene volcanic paleosols of Armenia and Mexico combine the features of both arid and humid pedogeneses. They were
studied in order to reconstruct the environmental conditions during the period of the initial settlement of humans in these
areas. The main attention was paid to the micromorphological analysis of the pedogenic features. The pedocomplexes studied
in Armenia have been forming since the Early Pleistocene. They bear evidences of humid (weathering, clay illuviation, and
gleying) and arid (calcification) pedogeneses alternating in different soil layers and pointing to climatic cycles. The nonuniform
lithology of the soil profiles is related to pulsating volcanic activity. Mexican paleosols of the Late Pleistocene period
are similar to the lower layers of the soils in Armenia with respect to the features characteristic of the humid and arid
phases of pedogenesis. This allows us to suggest that the early stages of the formation of the Armenian pedocomplex proceeded
under warmer paleoclimatic conditions similar to those of a tropical climate. It is shown that the arid pedogenesis may erase
the features produced during the previous stage of humid pedogenesis. The studied paleosols are characterized by the destruction
of the features inherited from the humid phase (the clayey groundmass and illuviation coatings) by the newly forming calcite.
Paleopedological records point to the fact that the paleoenvironmental conditions during the periods of the initial settlement
of humans in both regions differed significantly from the modern environmental conditions in these regions. 相似文献
18.
S. N. Lesovaya M. P. Lebedeva-Verba N. P. Chizhikova O. V. Romanov 《Eurasian Soil Science》2008,41(11):1137-1147
Soils developed from the red-brown Neogene clay and the Quaternary loesslike loams have been studied in the south of the forest-steppe zone on the Central Russian Upland. A polygenetic nature of the soil profile on the loesslike loams is shown. The modern pedogenetic processes in this soil ensure its eluvial-illuvial differentiation with the development of multilayered coatings in the illuvial horizon. The soil developed from the Neogene clay has a lower degree of differentiation despite the more acid reaction. The micromorphological study of the coatings and the mineralogical analysis of the clay fraction separated from the coatings and from the intraped mass disclose differences in the geneses of B horizons of the two soils. In the soil developed from the loesslike loam, hydromica predominates among clay minerals of the coatings; in the soil developed from the red-brown clay, smectitic minerals predominate in the clay fraction. Differences in the properties of these two parent materials predetermined differences in the major directions of soil formation: the metamorphic pedogenesis predominates on the red-brown clay, whereas the textural differentiation develops in the soil on the loesslike loam. The middle horizons in the studied soil profiles are referred to as the structural-metamorphic and textural (clay-illuvial) horizons, respectively. 相似文献
19.
20.
R. G. STURDY R. H. ALLEN P. BULLOCK J. A. CATT S. GREENFIELD 《European Journal of Soil Science》1979,30(1):117-137
Soils with paleosol features occur at the surface on the Chalky Boulder Clay in the Chelmsford area, Essex. Their particle size distribution, micromorphology and sand, silt and clay mineralogy indicate periods of weathering, clay illuviation and hydromorphism before deposition of loess in the Late Devensian. These periods are provisionally related to the Ipswichian and/or Hoxnian Interglacials. 相似文献