Relict Paleosols Research Articles

Elucidating the geogenic and pedogenic pathways of formation of soils of Peninsular India – Signatures of past landscape modifications

The soils of modified landforms of Peninsular India present an opportunity to unearth soil and landscape evolution. We explore the potential of vertical texture contrast (VTC) soils as signatures of past landscape modifications and associated soil formation in Peninsular India. We studied six VTC soils occurring on different geological formations for their morphology, geochemistry, and mineralogy in order to interpret the geogenic and pedogenic pathways of their formation. The presence of a lithological discontinuity with sharp contrast in particle size in pedons P1 and P3 suggested that fluvial sedimentary layering led to their formation. Pedons P2 and P5 are examples of buried soils where basaltic alluvium of varying thickness is overlying the soils of granitic and gneissic complex origin. These soils are potential proxies of landform changes attributable to paleo-alluvial mass deposition, possibly during the late Pleistocene. Pedon P4 is a relict paleosol in which the presence of a Ck horizon between the argillic (Bt) and BC horizons indicates sedimentation of stratified rocks (geogenic) followed by clay illuviation (pedogenic) during the past wet climate. The occurrence of smectite-dominant shrink-swell (S-W) soil (pedon P6) over the shale parent material suggests that the S-W soil is from a transported alluvium of weathering Deccan Basalt. Our results demonstrate the usefulness of VTC soils in interpreting the climate-shift-driven soil-landscape evolution in Peninsular India and elsewhere.

The imprint of time on Canadian soil landscapes

The imprint of time on Canadian soil landscapes reflects the strong influence of repeated Quaternary glaciations, with most soils having formed on Late Pleistocene glacial sediments, and to a lesser extent, Holocene non-glacial sediments. Soil chronosequences in these youthful landscapes seldom span the full Holocene, and have been documented principally in areas of coastal isostatic uplift and shoreline evolution, as well as on recessional moraine sequences in the Cordillera. These chronosequences have placed quantitative constraints on rates of podzolization in environments ranging from coastal temperate rainforest to subarctic. Longer sequences, involving soils and relict paleosols on Pleistocene morainal and glaciofluvial surfaces in the central Yukon Territory, record more complex legacies of pedogenesis and landscape evolution, but with much coarser time control and many potentially confounding influences of climatic change and disturbance processes. Older weathered bedrock and regolith can make significant contributions to soil parent materials in several settings: (1) in favoured locations where local conditions protected these materials from glacial erosion in southern Canada, (2) beyond the maximum limits of glaciation, principally in northwestern Canada, and (3) in the Arctic, where cold-based, non-erosive ice allowed preservation of these materials. Closer collaborations between pedologists and other Quaternary scientists will be needed to ensure a more complete understanding of these complex pedogenic legacies in Canadian landscapes.

Lateritization and Bauxitization Events

Laterites and bauxites are produced in tropical soils by weathering, which enriches iron (of laterites) and alu- mina (of bauxites)—as well as trace elements such as nickel, gold, phosphorus, and niobium—to ore grade. La- terites and bauxites can be redeposited into sedimentary sequences, and remain as ores if not transported far and diluted with other materials. The age of redeposited laterites and bauxites, and of bauxitic and lateritic pa- leosols, can be established from the geologic age of overlying rocks, an approach especially effective in pale- osols within sequences of isotopically datable volcanic rocks. Lateritic profiles can also be dated by paleomag- netic inclination in special cases in which land masses such as in Australia and India drifted long distances northward during Cenozoic time. In addition, cryptomelane and other K-Mn oxides can be dated by K-Ar and 40Ar-39Ar techniques to obtain multiple ages from different crystals in a single relict paleosol. Compilation of new and more accurate laterite and bauxite ages reveals unusually widespread and intense laterite and bauxite formation during events of less than 100 k.y. duration at 2, 12, 16, 35, 48, 55, 65 and 100 Ma. Such events can also be inferred at times older than 100 Ma from paleolatitudinal distribution of laterites and bauxites, but these are poorly sampled. Laterite and bauxite peaks were coeval with times of global high warmth and pre- cipitation, elevated atmospheric carbon dioxide, oceanic anoxia, exceptional fossil preservation, and mass ex- tinction. These CO2 greenhouse events and attendant titration of carbonic acid with soils are interpreted as transient fluctuations in the atmosphere produced by meteorite impact, flood basalt volcanism, and methane outbursts. Concentration of bauxite and laterite resources, in particular stratigraphic horizons formed during greenhouse crises, suggests the usefulness of an event stratigraphic approach to exploration and exploitation of these and related ores.

Correlations between pedological parameters in relation to lithology and soil type in Almería (SE Spain)

South-eastern Spain can be considered as a model of desertification in the Mediterranean environment. The desertification intensity varies according to two different geomorphological areas: glacis and badlands. The modal soil of the glacis area is calcic Luvisol, for which the severity of degradation depends on the degree of aridity and human activities, which give rise to the following degradation series: calcic Luvisol – luvic Calcisol – haplic, petric or aridic Calcisol. The badland area is more desertified than the glacis area. The modal soils in the badland area depend exclusively on the parent material: aridic Arenosols on sand; eutric, calcaric or gypsiric Regosols on silt and calcilutite; aric Gypsisols on gypsum; and aric Solonchaks on parent material rich in halite. Luvisols, Gypsisols and Solonchaks can be considered relict paleosols that developed in a wetter climate than the prevailing arid conditions that make clay illuviation or the formation of gypsic or salic horizons impossible. Soil quality reduction is shown by creating a database for soils’ physical and chemical properties, ranging in classes that facilitate the use of these properties as an effective tool for decision making with regard to desertification.

The last interglacial pedocomplexes in the litho- and morpho-stratigraphical framework of the central-northern Apennines (Central Italy)

Recently in Italy, a great deal of effort has been devoted to the mapping of Quaternary continental deposits. Several Unconformity Bounded Stratigraphic Units (UBSU) have been defined. The unconformities indicate important phases of changing dynamics linked to Quaternary climatic changes, and have been related to valley downcutting simultaneous with paleosol formation during interglacials. However, glacial periods are characterised by deposition of thick continental sequences. We suggest that the UBSU's belonging to the late Middle Pleistocene (MIS 6) and Late Pleistocene can also be defined under a pedostratigraphic point of view. Locally at the top of the UBSU attributed to MIS 6, buried or relict paleosols are preserved. The paleosols developed in calcareous fluvial and moraine gravels with minor flints. The pedocomplexes are made of three paleosols separated by erosion surfaces and/or stonelines. The older paleosol (MIS 5e) is severely truncated and is characterised by a Ck horizon overlain by strongly leached reddish Bt horizons with flinty rock fragments (with a diagnostic wavy lower boundary). In some sites, subsequent secondary precipitation of carbonates transformed this horizon into a Btk. This paleosol is buried by a younger paleosol (MIS 5c) with less leached reddish Btk horizons, quartz of aeolian origin, and very small and scarce calcareous clasts. The main pedofeatures are associated with colluvial processes, biological activity, and carbonate precipitation. This paleosol is also truncated and buried under a similar paleosol (MIS 5a). Therefore, the lower paleosol of the pedocomplex can be attributed to the Eemian, and constitutes a valid marker for the definition and mapping of the underlying and overlying sedimentary units. In other parts of the Apennines, no sedimentary units have been found that correspond to the unconformities separating different pedostratigraphical units. In order to map the different UBSU's, due to the poor lateral continuity of the preserved paleosols, morpho- and litho-stratigraphical investigations and correlation are always recommended.

Using the analysis of iron and iron oxides in paleosols (TEM, geochemistry and iron forms) for the assessment of present and past pedogenesis

This study investigates the iron oxide chemistry and mineralogy of two relict paleosols, a Ferri-Endostagnic Lixisol (Bathiplinthic) and a Profondi-Endostagnic Luvisol (Chromic). The estimated inception of their pedogenesis is Early Pleistocene. The two paleosols belong to the same geomorphic body, but are found at different elevations and have experienced different hydrology expressed as either dark red or mottled dominant colors throughout their profile. We hypothesized that the difference in color reflected a recent transformation of iron oxides that were mainly formed in the past. The aim of the research was to discriminate recent from relict soil forming processes by evaluating iron oxide composition, soluble forms, and geochemistry. In the studied profiles hematite and goethite ( αFeOOH) are the main iron oxides. Their fate depends on the present pedogenic conditions. Both hematite and goethite are a source of iron for recently synthesized iron oxides (feroxyhyte ( δ′FeOOH) and Fe-protophases), but hematite is preferentially dissolved in reducing conditions. In the red soil profile, hematite content still masks the presence of the other iron oxides, while the mottled color of the topographically lower profile, with poorer internal drainage, is a consequence of a more advanced hematite dissolution. The iron oxides (hematite, goethite and recently synthesized iron oxides) are the result of different pedoclimatic conditions in former and present time. Hematite is inherited from past pedogenesis, while feroxyhyte and Fe-protophases have been recently formed. Goethite can be of either current (transformed from feroxyhyte) or inherited origin. These results indicate that the soils studied are polygenetic; the red color and hematite content are the results of past soil forming processes acting in different climatic and drainage conditions.

Vetusols and paleosols: natural versus man-induced environmental change in the Atlantic coastal region of Morocco

Surface Terrae Rossae (Rhodoxeralfs), and a Terra Fusca (Petrocalcic Palexeralf) developed on mid-Quaternary calcarenites in the moister region of Rabat, show substantial pedogenic formation of clay minerals, particularly kaolinite, mainly in the fraction <0.2 μm . For the most part, the pedogenic kaolinites show poor crystallinity of the fireclay type. They are mainly formed from feldspars and perhaps also amphiboles and pyroxenes in the fractions >2 μm , and from smectites inherited from the calcarenite-residual loam in the coarse (2– 0.2 μm ) and fine clay fractions ( <0.2 μm ). In one Terra Rossa soil, formation was interrupted twice by deposition of eolian materials, and it is regarded as a polycyclic pedocomplex. Eolian input was much less important during development of the other surface Terrae Rossae. On younger calcarenites ( ⩾100 ka ) near the coast, three Rendzinas (Typic Calcixerolls) show only slight mineral weathering and pedogenic clay formation, in spite of a varied spectrum of primary minerals. In one example, kaolinite formation has just started. The Calcixerolls were probably recalcified by addition of eolian material as a result of anthropogenic thinning of the vegetation and/or due to the vicinity of the coast. These results suggest that, at least in this region, the younger Terrae Rossae of the coastal area were formed over much of the Brunhes epoch. In areas farther from the coast they have been developing for almost all of the Brunhes epoch. Because climatic fluctuations in the Quaternary were generally slight in this region, the direction of soil formation was constant. Therefore we regard the Rhodoxeralfs in the northern part of our study area as Vetusols. According to our expanded definition, Vetusols are surface soils which underwent almost constant processes of soil formation under an almost constant constellation of soil-forming factors, especially climate and vegetation, over a long period of time, including at least some part of the Pleistocene. Consequently the present patchy distribution of Terrae Rossae is hardly a result of climatically induced periods of “geomorphological activity and stability”. but the result of the removal of an earlier dense forest cover, followed by severe soil erosion. The human impact on the ecosystem is much more serious than any climatic fluctuations. In the southwestern part of the study area, between El Jadida and Agadir, the soil moisture regime is dry xeric to aridic and Terrae Rossae occur only in small areas, mostly in depressions. However, two selected Rhodoxeralfs in the vicinity of Tamanar show considerable pedogenic mineral weathering and clay mineral formation, though hardly any kaolinite. The strong weathering and clay illuviation must have been preceded by decalcification, implying a distinctly moister climate here in the past. However, micromorphological features of recent recalcification are common in these Rhodoxeralfs, suggesting that their main properties are not in equilibrium with the present climate and the soils should be regarded as nonburied paleosols or relict paleosols.

A micromorphological index of soil development for the Quaternary geology research

Profile development indices of Harden [Harden, J.W., 1982. A quantitative index of soil development from field: examples from a chronosequence in Central California. Geoderma 285, 1–98] and Ferrari and Magaldi [Ferrari, G., Magaldi, D., 1983. Significato ed applicazioni della paleopedologia nella stratigrafia del Quaternario. Boll. Mus. Civ. St. Nat. Verona 10, 315–340] have shown their utility for comparative dating of some paleosols during geomorphological and geological surveys. In Italy and other countries, pedostratigraphic methods have been commonly applied to soil profiles formed in continental formations. Unfortunately, buried and relict paleosols are very scarce or badly preserved in some areas of Italy due to past and recent tectonic activity and to strong human impact dating back to prehistoric times. In order to use relict paleosols for correct chronostratigraphic interpretation of relict paleosols and in order to correlate them with old landscape forms for the reconstruction of Quaternary sequences, a new micromorphological index (MISODI) for assessing soil development and degree of weathering was devised. The index was tested in the extensional tectonic basin of L'Aquila-Scoppito (Abruzzi, Central Italy) where some chronostratigraphic information is available. Results demonstrate that there is a good relationship between presumed relative age of paleosols and degree of weathering and pedogenesis in B and B/C horizons as assessed by this index. The index has the potential to be adapted for application to other paleosol types in other countries.

Factors affecting the structural stability of three contrasting soils of China

The structural stability of eight samples representing three soil profiles from tropical and subtropical regions of China (Latosol, Red Earth and Yellow Brown Earth) was studied by dispersion treatments. The samples were treated with the following solutions in order without previous mechanical disruption: (I) H 2O, (II) 0.1 N NaCl, (III) 0.002% Na 2CO 3, (IV) 0.1 N NaOH, (V) acid oxalate, (VI) 0.1N NaOH. These procedures were designed to disperse soil samples by removal of potentially aggregating substances and by anion adsorption. After each treatment the clay dispersed was separated by sedimentation and its mineralogical composition was studied by XRD, Mössbauer spectroscopy and magnetic susceptibility measurements to assess the role of mineralogy in the maintenance of soil structure. The amounts of iron extracted by Na-dithionite–citrate–bicarbonate were 9.6–10.8% in the Latosol, 3.1–3.4% in the Red Earth and 0.9–2.1% in the Yellow Brown Earth. It was concentrated in clay fractions and existed mainly as superdispersed particles. The hematite/goethite ratio varied from 1.7 for the Latosol to 0.2 for the Yellow Brown Earth. The clay fraction of the Yellow Brown Earth is vermiculitic and has a permanent negative charge. This soil's structural stability is mainly influenced by exchangeable Ca 2+. In the Latosol and the Red Earth, surfaces with variable (pH-dependent) charges prevail because of the large free Fe-oxides contents. Alkaline treatment (IV) promoted most dispersion of these soils, indicating the mainly electrostatic nature of interactions between mineral particles. Thus, the role of the Fe oxide minerals in these soils is one of aggregation rather than cementation. The aggregation properties of the Latosol and Red Earth are relict paleosol features inherited from an earlier period of cooler and wetter climate than the present.

Recent Pedological Approach to Reconstruction of the Quaternary Environment in Japan and East Asia.

Pedological studies contributed to the reconstruction of Quaternary environment of Japan and eastern Asia in 1990s. Study of the material in the Red-Yellow soil, a representative relict paleosol in Japan, improved understandings of the soil's genesis. The origin of Japanese Red-Yellow soils confirmed to be aeolian dust from the Asian continent and can be characterized as a transitional soil between a tropical and a warm regime, which has been developed by weathering during 103kyr. Studies of weathered volcanic ash layers improved the understanding of the formation of tephra-soil sequences widely distributed in Japan. The development of tephra-soil has occurred succestively during intervals between volcanic activity by the addition of weathered tephra and aeolian dust. Interpretations of environmental change in Holocene and late Pleistocene by investigations on tephra-soil and loess-soil sequences were supported by these findings.

Clay Minerals in Soils as Evidence of Holocene Climatic Change, Central Indo-Gangetic Plains, North-Central India

Clay mineral assemblages of a soil chrono-association comprising five fluvial surface members (QGH1 to QGH5) of the Indo-Gangetic Plains between the Ramganga and Rapti rivers, north-central India, demonstrate that pedogenic interstratified smectite–kaolin (Sm/K) can be considered as a potential indicator for paleoclimatic changes during the Holocene from arid to humid climates. On the basis of available radiocarbon dates, thermoluminescence dates, and historical evidence, tentative ages assigned to QGH1 to QGH5 are <500 yr B.P., >500 yr B.P., >2500 yr B.P., 8000 TL yr B.P., and 13,500 TL yr B.P., respectively. During pedogenesis two major regional climatic cycles are recorded: relatively arid climates between 10,000–6500 yr B.P. and 3800–? yr B.P. were punctuated by a warm and humid climate. Biotite weathered to trioctahedral vermiculite and smectite in the soils during arid conditions, and smectite was unstable and transformed to Sm/K during the warm and humid climatic phase (7400–4150 cal yr B.P.). When the humid climate terminated, vermiculite, smectite, and Sm/K were preserved to the present day. The study suggests that during the development of soils in the Holocene in alluvium of the Indo-Gangetic Plains, climatic fluctuations appear to be more important than realized hitherto. The soils older than 2500 yr B.P. are relict paleosols, but they are polygenetic because of their subsequent alterations.

Paleopedology of Terrae rossae—Rodoxeralfs from quaternary calcarenites in NW Morocco

Selected Terrace rossae or Rhodoxeralfs from calcarenites, in all probability of Mid-Pleistocene age, in the vicinity of Rabut show a strong mineral weathering and a considerable to extensive formation of clay minerals especially of kaolinites. Main sources of pedogenic kaolinites, mostly of a disordered structure and poor cristallinity, are primary feldpars (> 2 μm) and smectites (2-0.2 and <0.2 μm) inherited in the calcerenites as the parent material. The Rhodoxeralfs contain more or less allochtonous eolian material: these additional eolian inputs are in parts probably connected with the lowering of the sea level in the cool (glacial) stages, which results in an extended beach area of 10–15 km to the west in this region. However, the periods of the formation of the investigated relict (polygenetic) paleosols extended over most parts of the Brunhes epoch, including those of the cool (glacial) stages. The today's patchy distribution of the Terrae rossae is a result of a land degradation especially the removal of earlier dense forest cover followed by severe soil erosion due to human activity which is still grossly underestimated in comparison to climate variations in this area.

Soil polygenesis as a function of Quaternary climate change, northern Great Basin, USA

The Quaternary environmental history of the northern Great Basin is characterized by a combination of lower temperature and higher moisture than present. Using water-balance analysis of soils sampled along a climatic gradient, we demonstrate that long-term average effective moisture was about 2–4 cm yr −1 greater than present. Although this long-term average represents most of Quaternary time, there are important short-term excursions from these values during full glacial and interglacial times. Full glacial conditions are characterized by effective moisture about 7–9 cm yr −1 greater than present; interglacial times, similar to present conditions, are characterized by dry lake basins that provide major increases in eolian activity. These climatic extremes drive pedogenic processes that leave polygenetic imprints on soils of Pleistocene age. Soils that are now dominated by opaline silica, carbonate, and smectite contain evidence of earlier, more acidic, chemical environments conducive to dissolution of primary carbonate and formation of kaolinite. During interglacial time, more eolian activity and less effective moisture combine to decrease the depth of leaching, increase base cations, and modify the soil chemical environment in relict paleosols. In a soil of Bull Lake age (≈ 150 ky BP), desert loess accumulation created a 25% increase in water holding capacity and decreased the depth of water penetration by 65 cm; climatic drying at the end of the Pleistocene decreased leaching depth by about 150 cm.

Formation of Di- and trioctahedral smectite as evidence for paleoclimatic changes in Southern and Central Peninsular India

Di- and trioctahedral smectites in saprolites, developed on Precambrian gneiss and Gondwana sediments in southern and central Peninsular India, indicate a climatic change from tropical humid to semi-arid during the Plio-Pleistocene transition period. Well crystallised dioctahedral smectite was the first weathering product of Peninsular gneiss, and was subsequently transformed to kaolinite in ferruginous soils formed in a pre-Pliocene tropical humid climate. When the humid climate terminated both these clay minerals were preserved to the present. Silt and clay size trioctahedral smectite (i.e. low-charge vermiculite) in these saprolites is regarded as the alteration product of biotite formed in arid climate since the Plio-Pleistocene transition period. We conclude that the ferruginous soils on Peninsular gneiss and Gondwana sediments are relict paleosols, but are polygenetic because of their subsequent alterations.

Soil—Landscape Relationships in the Piedmont of Maryland

AbstractA study was conducted to investigate and model the soil‐landscape relationships in the Piedmont of Maryland. The soil series of particular interest were the Chester, Glenelg, and Elioak series of Typic Hapludults. Results indicate that Elioak soil is a relict paleosol. A stone line separating strongly weathered Elioak soil material from silty overburden was revealed in several excavations. Particle‐size analyses and elemental analyses of silt fractions confirmed these discontinuities. Comparisons with known and radiocarbon‐dated loess deposits on the eastern shore of Maryland indicate that the silty overburden on the Piedmont is loess which was deposited after 10,520 ± 240 years B. P. Where the loess is thick, as on gentle slopes, Chester soils are mapped. Where the relict paleosol has been essentially eroded away, as on steeper slopes, Glenelg soils are mapped.

Uranium-series and soil-geomorphic dating of the Calico archaeological site, California

Lithic specimens identified as artifacts have been recovered from near the base of the Yermo fan deposits at Calico, California. The soil on the fan surface is a strongly developed relict paleosol. Comparison of this soil with dated paleosols elsewhere in the southwestern United States suggests that the surface is about 80,000 to 125,000 yr old. Clasts near the base of the deposit are well cemented by laminated CaCO 3 that probably formed from groundwater action while the fan was still active. Uranium-thorium assays on the CaCO 3 indicate an age of 200,000 yr.

Adjustment to Quaternary Climatic Change by the Colorado River in Central Texas

Geomorphic mapping of flood plain and channel morphology in the Quaternary alluvial valley of the Colorado River revealed ten cross-cutting assemblages of fluvial channel patterns and associated sedimentary structures and textures. Quantitative studies of the modern and ancient patterns between Austin and La Grange, Texas, indicate systematic changes in channel width, meander wavelength, sinuosity, and sediment type through time. The changes appear to be cyclic, although the amplitudes of the cycles vary. Sufficient morphology is preserved to utilize empirical correlations of meander wavelength to discharge as an aid in paleohydrologic interpretation. However, the influences of sediment load and flood magnitude-frequency changes preclude quantitative speculation. Data from fluvial sediments, relict paleosols, and paleobiological studies support the hypothesis that Quarternary climate in central Texas alternated between relatively arid and humid intervals. Humid phases were characterized by fine-grained lo...

Paleosol identification and soil stratigraphy in South Island, New Zealand

Field and laboratory methods used for the identification of paleosols in New Zealand are discussed, and examples are given of their application to both buried and relict paleosols. Field methods include a pedomorphic index based on the quantitative assessment of four or more selected diagnostic properties for each horizon, which is useful under certain conditions to express the relative degree of development of several profiles. The significance of paleosol identification is only fully appreciated when the paleosol is defined stratigraphically and interpreted in terms of time and environment. The basis for defining soil-stratigraphic units in parts of New Zealand is outlined.

Paleohydraulic interpretation of Quaternary alluvium near Golden, Colorado

Quaternary terraces and pediments along Ralston Creek and Clear Creek, near Golden, Colorado, are associated with Verdos, Slocum, Louviers, and Broadway Alluviums. Terrace deposits can be locally correlated on the basis of elevation and relict paleosols. The terrace sediments probably represent aggradation by braided streams flowing from glaciated drainage basins. Engineering hydraulic calculation procedures suggest that flood flows were 2–3 m deep on steep gradients (0.008–0.01). Discharges were as great as 1400 m 3/sec, nearly an order of magnitude greater than modern flood discharges. The most useful paleohydraulic calculation techniques were found to be the dimensionless shear approach applied to stream competence and bedload function theory applied to stream capacity.