Pedological Processes Research Articles

Delineating the significance of sharp boundaries between horizons and their synergetic linkage in calcareous vineyard soils

The present work was undertaken to appraise and delineate the significance of sharp boundaries between horizons in calcareous vineyard soils by evaluating parent material uniformity and pedogenesis. To do so, 10 soil profiles (selected from 275) were investigated. The profiles up to a depth of approximately 150 cm were opened. Macromorphological features were described following FAO guidelines. Physico-chemical properties were analysed by the usual methods. X-ray fluorescence (XRF) was used to determine elemental Ti and Zn concentrations. In terms of the main morphological characteristics, soils are reddish, and have a well-developed solum, a subangular or prismatic structure and friable moist consistency (B horizon) unlike the C horizon, which generally varies from friable to hard or very hard in a massive structure. These latter are usually related to the pedogenesis of evolved soils containing accumulations of calcium carbonate to form calcic or petrocalcic horizons. Other genetic horizons of the studied soils are argillic or cambic, which all lie directly on parent materials, in addition to a surface Ap anthropic horizon. Although the considered soils displayed a significant sharp boundary between some horizons, and even though some soil parent materials were stratified in nature and apparently formed of multidepositional regimes, certainly the vertical distribution of Ti/Zr displayed minor variations with no clear inflection with depth. Therefore, the parent materials of the investigated soils are apparently formed of homogeneous depositional materials. The morphological contrast within a profile is due mainly to pedological processes (they are very mature) rather than to geogenic ones. Nevertheless, the marked contrasts between horizons cannot be explained only by pedogenetic processes, but by other secondary processes related to agricultural use (mechanical impact of tillage). This means a partly artificial distinction that entails surface erosion and, consequently, a manifest redistribution fundamentally on surface horizons. Based on all this, it can be deduced that these soils are formed from local and not from extraregional materials.

A numerical investigation of the influence of hydraulic parameters on the stability of a residual soil slope

The residual tropical soils and their unsaturated condition add more complexity to the study of slope stability, introducing the suction variable to the stress state analysis. Due to the complexity of the pedological processes involved in their formation, tropical soils present variability in their parameters. This results in uncertainties regarding its behaviour in geotechnical structures. The most common promotion agent for deformation and loss of strength in residual soils in an unsaturated condition is the advancing of the wetting front due to rainfalls. A tropical climate with high levels of rainfall makes landslides a constant and dangerous phenomenon, leading to loss of human life and material. Thus, it is essential to verify the influence of precipitation on slope behaviour in residual conditions. This study analyzes the behaviour of a slope formed by a residual soil by determining the soil properties followed by a numerical analysis. Laboratory tests were performed to characterize the soil and determine the strength, hydraulic, and unsaturated condition parameters. In the numerical analysis, it was intended to visualize the influence of rainfall and hydraulic parameters on the pore pressure distribution inside the slope and in its stability. After the numerical step, it was found that the different rainfall characteristics (intensity and duration) increased the pore pressures and decreased the strength of the material. However, it was insufficient to trigger any failure mechanisms. The hydraulic parameters’ critical roles at seepage through the soil and how this is reflected in the calculations of safety factors were verified.

Genesis, mineralogy, and geochemistry of soil profiles developed on volcanic materials under semi-arid conditions from Central Anatolia-Turkey

Pedogenesis of volcanic soils has been studied broadly in humid regions, but very little data are present regarding these soils in arid and semi-arid regions of Turkey. This research aimed to assess the pedological processes and investigate the physical, chemical, and mineralogical characteristics of soil profiles developed from volcanic parent material. The studied soils were not classified as Andisol because they lack andic properties. The results showed that sand and coarse silt fractions exceeded 30%. The bulk density was higher than 0.90 grcm-3 in all profiles. In general, phosphate retention was low, higher than 25% in profiles but lower than 85% in all profiles. The Al + ½ Fed percentages were lower than 2% in all profiles. Selective extraction (Na–Pyrophosphate, Ammonium Oxalate, Na–Dithionite) indicated that soils lack noncrystalline minerals, such as allophane, imogolite, and iron humus complexes. The only noncrystalline minerals in high quantities are Al-humus complexes and small amounts of ferrihydrite. X-ray diffraction indicated that smectite, kaolinite and illite were dominant minerals in the clay fraction. Among the studied profiles, profiles 1 and profile 4 are classified as vitrandic Haploxerept, profile 2 as vitrandic haploxerolls, and profile 3 as vitrandic Xerorthent. The results indicated that the dominant soil-forming processes include the following: 1. desilication and the eluviations of base cations and Al from the solum; and 2. transformation of iron and aluminum from the sand and silt-size fractions into secondary clay and crystalline Fe minerals. The major factors determining soil genesis on Mt. Karacadağ appear to be climate and topography affected by the leaching regime and weathering rates.

Soil processes in the Aeolian Litoral Sheet of Doñana National Park (Huelva, SW Spain): the catena of Colón small-lake ecosystem

The wetlands on the quartz sands aeolian sheet make up one of the ecosystems most recognized and important of the Doñana National Park and Doñana Biological Reserve (South Spain). More than 650 temporal small-lakes have been surveyed in the abundant sand depressions of the aeolian sheet, the most are a hydro-geomorphological dune-small-lake system. This paper studies the pedological processes around Colón small-lake ecosystem wetland (COL), one of the more interesting temporal small-lakes. The movement of fine particles through sand dunes ("sand washing") and their subsequent accumulation in depth is the process responsible for the formation of a large part of the small and medium small-lakes in the Eolian Litoral Sheet of Doñana. Their bodies of water are supported by these clay layers generated corresponding sometimes to ancient soil horizons formed under previous different ecological conditions. The vegetation, the soil morphology and the evolution of the physical-chemical processes studied in this geosystem small-lake of Colón allow understand this phenomenon of chronologies very recent.

Detailed soil mapping and classification study for sustainable agricultural land management; Samsun-Vezirköprü example

This study aims to determine basic physico-chemical soil properties, make a classification, create a soil database, and generate a digital soil map for agricultural areas that cover about 111 km2 ha and includes 18 villages located in Vezirköprü district in the Samsun province. The average annual temperature is 12.52 °C and the annual average rainfall is 518 mm. According to the Newhall simulation model, soil temperature and moisture regimes are Mesic and Typic Xeric, respectively. Field observations and investigation of topographical, geological, and geomorphological maps, 16 soil pedons were described. Soil samples were taken from each pedon based on the genetic horizon and laboratory analyzes were performed. The detailed field study was carried out by considering the grid method and auger examination. The determination and description of 16 soil series were made by evaluating the findings of analyses and field research. Due to their quick pedological processes, six of them were classified as Entisol, six as Inceptisol, three as Verisol, and one as Alfisol. Vertisols cover about 35.63% of the total area followed by Inceptisols at 22.3%, Entisols at 22.3%, and Alfisol at 13.58%. As for FAO-WRB classification system, soils were classified as Vertisol, Cambisol, Leptosol, and Luvisol. In addition, whereas the Bakçekonak series has the largest area (15.02%), the Yürükçal series was determined as the smallest land (1.65%) in the study area.

Soil formation and hydrological evolution of Navazo del Toro small-lake ecosystem, Doñana National Park, Andalusia, Spain

The wetlands on the quartz sands aeolian sheet make up one of the ecosystems most recognized and important of the Doñana National Park and Doñana Biological Reserve (South Spain). More than 650 temporal small-lakes have been surveyed in the abundant sand depressions of the aeolian sheet, the most are a hydro-geomorphological dune-small-lake system. This paper studies the pedological diversity around Navazo del Toro (NVT) wetland, one of the biggest temporal small-lakes, through a geopedological catena along 230 m with five soil profiles (NVT-1 to NVT-5). In this context a major focus is displayed on pedological processes and the current hydrological situation of the depression in the Middle-Upper Holocene. The main processes are: translocation of materials (silt and clay) from the Arenosols developed in the slope dune (sand washing processes), sediment accumulation on the dune depression (current wetland bottom), and the development of tirsificated and vertic Luvisols with a chronology of more than 4.255 BP (OSL dating). The water body of the geoecosystem has modified the horizons morphology, creating new hydromorphic (gleyic and stagnic) conditions that have incorporated abundant organic material (sediment of diatoms and sponge spicules) in the higher profile layer and generated an incipient podzolization processes.

Geochemical evidence of illuvial processes in clay-rich soils on limestones in a humid temperate climate

In environments with high precipitation, eluvial–illuvial processes play a key role in pedogenesis. Vertical translocation of clay leads to the formation of an argic horizon. Such soils are of global importance and formed on different rock substrates under different climatic conditions. However, the pedogenesis of clay-rich soils developed on limestone in humid temperate climates has not been sufficiently investigated. Therefore, this study aimed to evaluate the geochemical and mineral compositions and properties of Luvisols (10 profiles) from the Dinaric karst region and identify the geochemical indicators of eluvial–illuvial processes. The geochemical and mineral differences between the A, E, and Bt horizons could be explained by the pedogenic processes of biorecycling, migration, isomorphic substitution in minerals, surface adsorption to clay or Al/Fe oxide minerals, and precipitation from the soil solution. Illuviation is evident in the downward increase in Al2O3, Fe2O3, MgO, K2O, Ba, Co, Cr, Ga, Ni, Sc, Th, U, V, Y, and REE. Despite differences in the geochemical characteristics of the 10 studied profiles, eluvial–illuvial processes outweighed the heterogeneity of the soils from different sites and the probable contribution of allochthonous material to the soil. We established new textural and geochemical indicators that could explain the differences among horizons and profiles in light of the polygenetic origin of soil material and pedological processes.

Characterizing a weathering profile over serpentinite in the Senaling area, Negeri Sembilan Darul Khusus

Three broad morphological zones can be differentiated; the top, 2.5 m thick, pedological soil comprising IA and IB sub-zones of brown, soft clays, and IC1 and IC2 sub-zones of reddish brown, stiff silty clays with lateritic concretions and lateritized core stones. The intermediate, 1.5 m thick, saprock zone consists of brown, stiff, silty clays with indistinct relict fault planes and core-stones, whilst the bottom bedrock zone consists of serpentinite with effects of weathering along discontinuity planes. Constant volume samples show the earth materials to be rather loose with dry unit weights of 10.32 to 16.28 kN/m3 and porosities of 39 to 60%. Particle size distributions are variable with depth; silt contents decreasing from 38 to 58% in saprock to 28 to 44% in the pedological soil zone. Increasing fine clay (<2 μm) contents up the profile from 34 to 43% in saprock to 40 to 51% in sub-zones IA and IB indicate that pedological processes result in continued disintegration of weathered serpentinite. Plastic and liquid limits have limited variation ranging from 24 to 33%, and from 36 to 50%, respectively. Weathered rims around core-stones show alteration of serpentinite to start with the opening-up of grain boundaries and formation of micro-cracks (Stage 1) followed by staining along chrysotile veinlets (Stage 2). More extensive staining then occurs with decomposition (to clay minerals) of most antigorite and chrysotile grains (Stage 3) and ending with formation of a brown, stiff silty clay (Stage 4). Increasing stages of weathering are marked by decreasing dry unit weights and uniaxial compressive strengths, but increasing apparent porosities. It is concluded that in situ alteration of serpentinite through lowering of an unconfined groundwater table has led to development of the weathering profile.

Periglacial landforms and soil formation on summit of the Mount lda (Kaz Dağı), Biga Peninsula-Turkey

ABSTRACT The aim of the study is to reveal geomorphological characteristics and evolution of the periglacial landforms occurred on the summit of the Kaz Dağı (in Turkish) characterised with a specific mountain environment developed under the dry summer subtropical Mediterranean climate. To reach this aim, morphoclimatic processes-characteristics and soil development of the Kaz Dağı district have been evaluated. Kaz Dağı (1774 m a.s.l.), which had been called as the Mount Ida in Greek Mythology, forms a physical geographic border between Çanakkale and Balıkesir provinces. Periglacial landforms consisting of the non-sorted circles including mud circles and stony earth circles, non-sorted steps and cryoturbation terraces and block currents, are found in subalpine vegetation zone at upper boundary of Mount Ida. According to morphogenetic process analysis, on the summit of the Kaz Dağı, the dominant processes are freezing + freezing-thawing in the December-March period, freezing-thawing + weathering in the November and April months, and weat-hering in which frost is not effective in the April-November period. As for pedological processes and mineralogical characteristics of soils formed under the same climatic conditions but on different parent materials of various periglacial landforms, taxonomy of these soils was classified at the Entisol ordo described as young soils.

Soil-sediment-configurations on slopes of Central and Western Crete (Greece) and their implications for late Holocene morphodynamics and pedogenesis – A conceptual approach

Geomorphological processes and soil formation in slope positions within the Mediterranean area have been in the focus of research for a long time. Many of the surface-near soil-sediment-configurations in the Mediterranean area have been termed soils and have been interpreted as typical (zonal) Mediterranean reddish-brown soils (RMS) of Terra Rossa type associated with clay illuviation as main pedological process. However, there has been an extensive scientific debate which (late) Holocene geomorphological and pedological processes in fact dominate current soil-sediment-configurations, especially before the background of a long-lasting history of intense human land use impacts.In the present study, we present field evidence as well as analytical data for a number of representative soil-sediment-profiles located in a variety of geological, geomorphological and climatic settings in central and western Crete (Greece). We have grouped the profiles in three schematic geomorphological categories in order to provide a geomorphological instead of a pedological context for their interpretation and comparison. Based on geochemical, mineralogical, geophysical and micromorphological evidence we could show that in most of the studied profiles, (late) Holocene pedogenesis is comparatively weak, except for bioturbation in combination with surprisingly high TOC-contents. Discontinuities within profiles are the result of geomorphological processes and the corresponding deposition of clearly distinguishable parent materials (substrates) rather than pedologic processes resulting in the in-situ differentiation of soil horizons. Furthermore, characteristic and ubiquitous peaks in grain size distribution within the clay and silt grain size fractions could be identified and are most likely related to long-range dust inputs. Whether the weak degree of recent pedogenesis is due to the long-lasting history of intense land use or rather due to the (naturally) high intensity of geomorphological processes and sediment relocation remains one of the main open questions raised by the results of this study.

Geochemistry of semi-arid Cryosols on volcanic and sedimentary materials from James Ross Island, Antarctica

In most parts of Antarctica, specifically in arid and semi-arid condition, soils are the results of weak weathering and little pedogenic processes. There, the use of geochemical data is considered an important tool to interpret possible pedological processes through the changing molecular ratios of elements with depth. The semi-arid soils of Antarctica remains little explored. In this study, the geochemistry of soils developed on different parent materials under a typical semi-arid climate was investigated, based on the quantification of the elements by various methods. Based on the major and trace elements geochemistry, the soil types are clearly differentiated by their geochemical composition, and highly affected by their parent materials. Based on the major elements abundances, chemical weathering is very limited. Using geochemical parameters to identify lithologic discontinuities, five profiles showed this characteristic. The apparent high chemical index of alteration and mineralogical composition, with kaolinite in the clay fraction, soils developed on the marine sedimentary rocks showed a pre-weathered nature, related to the ancient inheritance of Cretaceous paleoclimates, during which warmer climate led to intense weathering under subtropical conditions. Therefore, pre-weathering has a role in the mineralogical composition of Antarctic soils on sedimentary rocks.

Characterizing a weathering profile over the Kuantan Basalt

Three broad morphological zones can be differentiated; the top pedological soil (Zone I) being 3.60 m thick and comprising brown, soft to stiff, clays. The intermediate saprock (Zone II) is 1.12 m thick and consists of brown, very stiff, sandy silt with many lateritic concretions, whilst the bottom bedrock (Zone III) is an outcrop of vesicular olivine basalt with weathering along joints. Constant volume samples show the saprolite (sub-zone IC) to have dry unit weights of 11.78 to 12.80 kN/m3, whilst the solum (sub-zones IA and IB), and saprock, have values ranging from 10.65 to 11.09, and from 11.35 to 11.50, kN/m3, respectively. Porosities are variable; the saprolite with the lowest values of 52 to 56% and the solum and saprock with values of 57 to 60%. Clay and silt contents increase up the profile with a corresponding decrease in sand and gravel contents. Colloid (<1 μm size) contents especially increase up the profile from 10 to 15% in saprock through 30 to 40% in saprolite and exceeding 57% in the solum, These increasing colloid contents point to the increasing effects of pedological processes. Thin-sections of weathered rims (1-2 cm thick) show alteration of basalt to start with formation of micro-cracks (Stage 1) that become stained by secondary iron oxides and hydroxides. Decomposition of the essential minerals then occurs in the order: olivine (Stage 2), augite (Stage 3), and plagioclase feldspar (Stage 4). An increase in apparent porosity, but a decrease in unit weights and specific gravity, reflect these stages of weathering; the boundary between ‘rock’ and ‘soil’ material occurring when all olivine and augite crystals have decomposed. It is concluded that the weathering profile results from in situ alteration of basalt due to lowering of an unconfined groundwater table; pedological processes giving rise to further alteration.

Changing controls of soil water retention in an alpine catchment: Integrating sedimentological and pedological processes

Soil’s hydrological and ecological functions depend largely on soil water retention, which is affected by both structural and compositional soil properties. Studies have shown that alpine soils derived from sediments with different origins in the northeast Qinghai-Tibetan Plateau differ significantly in terms of particle size distribution, bulk density and soil organic carbon content. However, the variation pattern and its drivers of soil water retention in this region remain unclear. In this study, soil water retention characteristics (saturated soil water capacity, field capacity, wilting point and plant available water capacity) from different geomorphic settings (i.e., hillslopes, alluvial fans and floodplains) of an alpine catchment in the western part of the Qilian Mountains were analyzed in relation to sediment types and soil properties. Results show that soil water retention varies significantly with sediment types. Soils with an aeolian origin have a higher capacity to retain water compared with soils developed on fluvial sediments. Variations in soil water retention are mainly controlled by particle size distribution for fluvial sediments and by soil organic carbon content for aeolian sediments. The accumulation of soil organic carbon enhances plant available water capacity for sandy fluvial sediments but not for silty fluvial and aeolian sediments. The critical eco-hydrological functions of the mattic surface soil horizon in relation to water retention, runoff regulation and erosion control were highlighted for the alpine ecosystems. By deciphering sedimentological and pedological controls of soil water retention, this study improves the understanding of the evolution and functioning of alpine soils, which has further implications for other sedimentary ecosystems.

Multiscalar Geomorphometric Generalization for Soil-Landscape Modeling by Random Forest: A Case Study in the Eastern Amazon

Multiscalar topography influence on soil distribution has a complex pattern that is related to overlay of pedological processes which occurred at different times, and these driving forces are correlated with many geomorphologic scales. In this sense, the present study tested the hypothesis whether multiscale geomorphometric generalized covariables can improve pedometric modeling. To achieve this goal, this case study applied the Random Forest algorithm to a multiscale geomorphometric database to predict soil surface attributes. The study area is in phanerozoic sedimentary basins, in the Alter do Chão geological formation, Eastern Amazon, Brazil. The multiscale geomorphometric generalization was applied at general and specific geomorphometric covariables, producing groups for each scale combination. The modeling was run using Random Forest for A-horizon thickness, pH, silt and sand content. For model evaluation, visual analysis of digital maps, metrics of forest structures and effect of variables on prediction were used. For evaluation of soil textural classifications, the confusion matrix with a Kappa index, and the user’s and producer’s accuracies were employed. The geomorphometry generalization tends to smooth curvatures and produces identifiable geomorphic representations at sub-watershed and watershed levels. The forest structures and effect of variables on prediction are in agreement with pedological knowledge. The multiscale geomorphometric generalized covariables improved accuracy metrics of soil surface texture classification, with the Kappa Index going from 43% to 62%. Therefore, it can be argued that topography influences soil distribution at combined coarser spatial scales and is able to predict soil particle size contents in the studied watershed. Future development of the multiscale geomorphometric generalization framework could include generalization methods concerning preservation of features, landform classification adaptable at multiple scales.

Mapping soil properties at multiple depths from disaggregated legacy soil maps in the Brittany region, France

Digital Soil Mapping (DSM) is increasingly needed to improve existing soil information and derive soil property maps at the suitable spatial resolution for sustainable soil landscape management. However, predicting several soil properties while preserving specific pedological process is a great challenge, particularly when only coarse soil information is available over large areas. Spatial disaggregation seems to be an effective technique to extract pedological information by downscaling the original information to produce soil maps at finer resolutions. In a previous study, legacy soil maps of Brittany (France) were disaggregated at a 50 m spatial resolution using the DSMART (Disaggregation and Harmonization of Soil Map Units Through Resampled Classification Trees) algorithm and pedological knowledge. The present study had two main objectives: (i) assess the preservation of the relationships between soil properties when soil properties are estimated at standard depths by applying the equal-area spline method on soil data at pedon scale, and (ii) combine disaggregated soil maps and spline-function results to estimate spatial patterns of nine soil properties for six regular soil-depth intervals down to 200 cm across Brittany, an area of 27,040 km2. To this end, soil properties were first generated for standard soil-depth intervals using spline functions. Then, for mapping soil properties at the six standard depths, weighted mean of each soil attribute was calculated for each grid cell from reference soil-property values of the three most probable predicted soil types. Their associated probabilities of occurrence were used as weights. To assess the ability of spline functions to preserve soil-property relationships, multiple statistical analyses were performed using original and splined soil datasets. Bivariate and multivariate analysis highlighted that spline functions preserved soil-property relationships. Derived digital soil maps showed strong spatial patterns: SOC and silt contents generally decreased with depth, while sand content and coarse fragment percentage consistently increased with depth. In addition, experimental semivariogram analysis of SOC content showed high spatial variability over short distances for all soil-depth intervals except the deepest (100–200 cm), while silt content showed high semivariance for the deepest soil layers. This study can be considered an example of harmonization to common output specifications, which generates a geo-database of quantitative soil properties that describe lateral and vertical soil variation for regular depth intervals. These predictions can be incorporated into environmental models to help decision makers manage landscapes.

Growth of Grimmia mosses on volcanic tephra: Geoecological processes of biocrust development in Haleakalā crater (Maui, Hawai′i)

This research examines high-elevation biocrusts on volcanic tephra in Haleakalā Crater, Maui, Hawai′i; geomorphic, ecological, and pedological processes are discussed, in order to provide an integrated geoecological view of linkages that have influenced biocrust genesis. The study considers four spatial scales: (i) the landscape scale; (ii) the site scale; (iii) the miniature scale and, (iv) the microscopic scale. (i) Biocrusts grow at ~ 2335 m on a hydrologic basin circumscribed by four cinder cones which contributed tephra materials during eruptions between 11000 and 5000 BP, ~2700 BP, and 970 ± 50 BP. Basin landforms provide multiple clues about past geomorphic processes that have affected crust evolution, including intermittent runoff, which decreased the length of cryptobiosis periods, allowing poikilohydric mosses to gradually expand into dense biocrusts; and widespread frost activity, which caused tephra sorting and extensive slope creep on cinder cones. Ubiquitous signs of current frost disturbance are also found on basin soils. (ii) The study site, located amidst bare volcanic tephra—ash and lapilli—includes mainly two organisms: an acrocarpous moss, Grimmia torquata, and a foliose lichen, Peltigera rufescens. Biocrusts attained 40.23% groundcover;G. torquata was found on 64 undisturbed specimens, and showed 78.3% frequency on 46 sampling plots, whereas P. rufescens grew on 23.4% of specimens. Biocrusts also supported 13 vascular species. The most common were grasses, with 5.6% cover and 67.4% total frequency, including Trisetum glomeratum (47.8%) and Deschampsia nubigena (19.6%); other vascular plants reached just 0.85% combined cover. Tests show 72% of vascular-plant cover was statistically correlated with presence of biocrusts, suggesting these have beneficial—presumably pedological—effects on vascular plant growth. (iii) Biocrust microtopography was characterized by intermingling areas of rolling, 15–35 mm-high, protrusions, and 40–75 mm-high pinnacles. (iv) Soil micromorphology indicated crust growth was probably influenced by a host of genetic processes, including wind abrasion and erosion; aeolian dust deposition; soil desiccation during seasonal wet-dry cycles; rainwash and raindrop impact; diurnal temperature cycles; and bioturbation by burrowing fauna. The interactions among these agents are integrated into an idealized crust developmental sequence during the past few millennia.

Development of the ground model for the Clay-with-flints Formation: adventures in geological boundaries

The Clay-with-flints Formation crops out on the high chalk plateaux in southern England. Changes in terminology are summarized and distinctions from adjacent similar deposits (e.g. Valley Gravel) are detailed. A threefold division of the transition zone between the two deposits is proposed based on degree of disturbance. Relationships with parent materials are discussed through structural and spatial relationships, as shown on published maps and in memoirs. Dominant pedological processes involved in the formation of the Clay-with-flints Formation from the Lambeth Group are described. A twofold division between the two is proposed based on physical changes. In addition to geological and pedological information, the deposit was studied through ground investigation data from 60 km of motorway network, which covers the variation in the Paleocene deposits (Lambeth Group facies (Reading Formation to Woolwich Formation) and the increasing presence of Thanet Sand Formation along the North Downs, east of approximately Leatherhead). The resulting ground model requires detailed knowledge of the microstructures of the chalk, the facies variation of Paleocene and Pliocene deposits, and temperate climate pedological processes in the vadose zone. Future work to study the engineering properties reflecting the variation of both the Paleocene facies and the development of the vadose zone is summarized. Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology

Mineralogical and Geochemical Nature of Calcareous Vineyard Soils from Alcubillas (La Mancha, Central Spain).

The mineralogical and geochemical patterns of calcareous vineyard soils located in Alcubillas (La Mancha, Central Spain) have been evaluated; also their variability has been studied. The information provided by this study supports the assessment of geochemical spatial variability, the origin of these soils, their elements and the factors that control their distribution. The presence of quartz, calcite, feldspar and, in particular, illite and kaolinite is due to their inheritance from surrounding lithologies (and pedological processes), which mostly include limestones, marls and other sedimentary rocks, as well as metasedimentary rocks of Hercynian origin. Furthermore, since the presence and accumulation of certain trace elements in vineyard soils is a relevant global hazard (in particular with respect to wine production quality), the spatial distributions of Ba, Cr, Cu, Pb, Rb, Sr, V and Zr (carried out using geostatistical techniques and geometry-based interpolation methods) were investigated in order to determine the origin of these trace elements. The presence of these elements can be interpreted as being due to geogenic, pedogenic and, in certain cases, anthropic influences. The nature of certain agricultural practices, including the use of fertilizers, phytosanitary products and machinery, could explain the local increases in some trace element contents.

The Cenozoic deposits of the ancient landscapes of Quadrilátero Ferrífero highlands, Southeastern Brazil: Sedimentation, pedogenesis and landscape evolution

The Quadrilátero Ferrífero (QF), Southeastern Brazil, is a very important tropical highland region in the world’s geological context for its large and diverse Archean and Proterozoic rocks with great reserves of gold, iron, manganese, aluminum and industrial rocks, on a apparently stable geological structure. There, Cenozoic deposits perched on highland valleys show unclear genetic relationships with the underlying bedrock, with no apparent regional correlation. We studied five representative Cenozoic deposits (BR356, Água Limpa, Padre Domingos, Pau Branco and Casa de Pedra) on the highlands of the Serra da Moeda syncline, Western QF, to answer the question of their sedimentological origin, and investigate their pedological evolution. Field sampling was complemented by macromorphological, mineralogical and micromorphological analysis supported by X-ray diffraction (XRD), differential thermal analysis (DTA), infrared analysis (IR), scanning electron microscopy (SEM), micropobre and transmission electron microscopy (TEM). The evolution of these isolated highland deposits comprises a deep-weathered source area, a tectonic activity, besides sedimentological and pedological processes, during and after the deposition. The deposits overlie deep saprolites of Precambrian rocks (Piracicaba and Itabira Groups), representing unconformable contact. The onset of the deposition was marked by torrential, coarse colluvial and large blocks landslides into the small basins generated by reactivating tectonic events during the Oligocene, producing local grabens. These tectonic basins were filled by cohesive debris and mudflow from the adjacent and previously laterized cover, developed under the hot and humid climate in the Eocene. The cover reveals an upside-down lateritic profile where morphology and kaolinite crystal properties (values of size of coherent scattering thickness ranging from 135 Å to 162 Å) in the bottom is related to the pedolith horizons of the former lateritic cover. Later, due to climate changes (during and after the Miocene), renewed weathering on these pre-weathered sediments occurred, characterized by alternating ferruginization and Fe-losses, with the superimposed generation of new pedogenic features such as nodules, ferruginous duricrusts and mottling (redox features). In addition to demonstrating that the Brazilian platform was not stable during the Cenozoic, these deposits reveal the role of polygenetic tropical pedological processes in their formation and transformation.

A soil colour map of China

Soil colour can indicate soil physical, chemical and biological properties and processes, and is an important indicator for soil classification, soil quality evaluation and soil management. It varies in both horizontal and vertical dimensions, and thus regional maps of soil colour can reveal spatial patterns of these properties, processes, and indicators. However, although soil regions are sometimes named for their dominant soil colour, it is directly measured only at “point” support, i.e., during soil profile description, whereas it is desirable to know soil colour over the entire soilscape. To achieve this for China we used predictive soil mapping methods to produce soil colour maps (dry and moist colours) at 1 km2grid cell size and over multiple depths from a consistent dataset of approximately 4 600 full profile descriptions taken as part of a national survey to define soil series in Chinese Soil Taxonomy, and a set of environmental covariates covering the national territory. The covariates characterized soil forming factors including climate, parent materials, terrain, vegetation, land surface water and thermal conditions. Soil colour descriptions in the Munsell system were extracted from the genetic horizon descriptions at the selected depths and converted to the sRGB and L*a*b* colour spaces. Dry and moist colour separates were not well-correlated in either space (r<0.76). Random forest models were constructed in both spaces, for dry and moist colours separately. Models in sRGB space were moderately successful (R2≈0.43,RMSE≈26/255) at 5 cm, with success decreasing with depth. Models smoothed the colour space and thus did not predict the more extreme values or chromas, nor the rarer hues. Models in L*a*b* space were less successful. The fitted sRGB models were used to produce predictive maps over all of China. Regional patterns as well as local detail are clearly shown. Solar radiation, wind exposure, regolith thickness, and Landsat TM bands 7 and 5 contributed most to the predictions, followed by elevation, mean annual precipitation, terrain wetness index, air temperature seasonality, precipitation standard deviation and standard deviation of NDVI. These suggest pedological processes acting on the development of soil colours, including weathering of parent materials, oxidation-reduction chemistry and biochemistry of the decomposing of organic matter. This study shows that predictive methods from points using suitable covariates are an alternative to spatial predictions over map units from their representative profiles.