Soil catenas of calcareous tills,Whiskey Basin,Wyoming, USA

We describe catenas developed on calcareous moraines of Pinedale (∼21–15 ka) and Bull Lake (>130–100 ka) ages at Whiskey Basin on the eastern flank of the Wind River Range, Wyoming, USA. We sampled one catena of each age from each of two separate moraine fields: the Jakey's Fork and Torrey Creek valleys. Soils of the Bull Lake catena at Jakey's Fork are more developed than those of the corresponding Pinedale catena: they have thicker sola, more horizons, more pedogenic clay, and more pedogenic carbonate presumably, because of their greater age. The Weighted Mean Profile Development Index does not distinguish between the Torrey Creek catenas. Pedogenic carbonate content is greater in the Torrey Creek Pinedale catena than the corresponding Bull Lake catena, and pedogenic clay is greater in the Bull Lake catena. Catenas on the Jakey's Fork moraines are generally more developed than corresponding catenas on the Torrey Creek moraines. We suggest that differences in catena development mostly result from the differences in slope length between the Jakey's Fork and Torrey Creek catenas. The Jakey's Fork catenas are shorter than those of the Torrey Creek, which appears to lessen the role that topographic position plays in catena development.     

Influences of quaternary climatic changes on processes of soil development on desert loess deposits of the Cima volcanic field, California

Soils formed in loess are evidence of both relict and buried landscapes developed on Pliocene-to-latest Pleistocene basalt flows of the Cima volcanic field in the eastern Mojave Desert, California. The characteristics of these soils change systematically and as functions of the age and surface morphology of the lava flow. Four distinct phases of soil development are recognized: phase 1 - weakly developed soils on flows less than 0.18 M.y. old; phase 2 - strongly developed soils with thick argillic horizons on 0.18 – 0.7 M.y. old flows; phase 3 - strongly developed soils with truncated argillic horizons massively impregnated by carbonate on 0.7 to 1.1 M.y. old flows; and phase 4 - degraded soils with petrocalcic rubble on Pliocene flows. A critical aspect of the development of stage 1 soils is the evolution of a vesicular A horizon which profoundly affects the infiltration characteristics of the loess parent materials. Laboratory studies show that secondary gypsum and possibly other salt accumulation probably occurred during the period of phase 1 soil development. Slight reddening of the interiors of peds from vesicular-A horizons of phase 1 soils and presence of weakly developed B horizons indicates a slight degree of in situ chemical alteration. However, clay and Fe oxide contents of these soils show that these constituents, as well as carbonates and soluble salts, are incorporated as eolian dust. In contrast to phase 1 soils, chemical and mineralogical analysis of argillic horizons of phase 2 soils indicate proportionally greater degrees of in-situ chemical alteration. These data, the abundant clay films, and the strong reddening in the thick argillic horizons suggest that phase 2 and phase 3 soils formed during long periods of time and periodically were subjected to leaching regimes more intense than those that now exist. Flow-age data and soil-stratigraphic evidence also indicate that several major loess-deposition events occurred during the past 1.0 M.y. Loess events are attributed to past changes in climate, such as the Pleistocene-to-Holocene climatic change, that periodically caused regional desiccation of pluvial lakes, reduction of vegetational density, and exposure of loose, unconsolidated fine materials. During times of warmer interglacial climates, precipitation infiltrates to shallower depths than during glacial periods. Extensive, saline playas which developed in the Mojave Desert during the Holocene are a likely source of much of the carbonates and soluble salts that are accumulating at shallow depths both in phase 1 soils and in the formerly noncalcareous, nongypsiferous argillic horizons of phase 2 and 3 soils.     

Soil-geomorphology relations in mountains of Oregon,U.S.A.

The development and distribution of soils in the Coast Range and Klamath Mountains are related to geomorphic surfaces and slope gradients. Soils over basalt, studied in the Coast Range, were formed in transported materials and include examples of more than a half dozen great groups of the Alfisol, Inceptisol, Mollisol, and Ultisol orders. Distribution patterns of the soils can be related to active slopes, metastable slopes, pediments, ridge tops, flood plains, and alluvial fans. Variables among the factors of soil formation in the Coast Range are chiefly geomorphic surfaces and parent materials.Soils of a lithosequence of pyroclastics, granite and schist in the Klamath Mountains include examples of great groups in the Entisol, Inceptisol, and Mollisol orders. All soils from pyroclastics have argillic horizons, those from granite lack argillic horizons, and those from schist lack argillic horizons except on relatively stable surfaces. Average thicknesses of soils over saprolite range from 76 cm over granite and schist to 150 cm over pyroclastics.Lithologic discontinuities are common in both mountain areas. Field techniques for identification, described briefly, include stone lines, irregular distribution of rock fragments with depth, thicknesses of weathering rinds on rock fragments, and the lateral extensions of soil horizons.     

Mineralogic evolution in hydromorphic sandy soils and podzols in “landes du médoc”, France

Soils of the nearly level “Landes du Médoc” in southwestern France have a pattern of alternating bodies of hydromorphic podzols (Haplaquods) and low humic hydromorphic soils (Psammaquents). The soils are formed in a sedimentary mantle of coarse, quartzose sands with a slight microrelief consisting of low, elongated ridges and shallow, intervening troughs. The water table is at shallow depths throughout the plain, even at the surface in places. The podzols on the crests of the low ridges have distinct A₂ and cemented B₂ h horizons. Podzols persist down the sides of ridges but going downslope first lose the A₂ horizon and then the cementation of the Bh horizon. Soils in the shallow troughs have A₁ and Cg horizons without B horizons.The fine silt (2–20 μm) and clay (0–2 μm) fractions of the parent sand contain primary trioctahedral chlorite, mica, feldspars, and quartz, with the last mineral predominant. During soil development, the first three minerals undergo weathering at different rates and to different extents. Chlorite is most strongly weathered, followed in order by plagioclases and K-minerals. In the fine silt fraction, weathering seems to occur mostly by fragmentation of particles. In the clay fraction, the phyllosilicates successively form irregularly interstratified minerals with contractible but not expandable vermiculitic layers, interstratified minerals with contractible and expandable smectitic layers, and finally smectites.The extent to which the silicate minerals are weathered becomes progressively greater from the low humic hydromorphic soils to the podzols with friable Bh horizons to the podzols with cemented Bh horizons. Smectite is present only in the A₂ horizons of these last podzols.The aluminum release by weathering of silicate minerals is translocated in part in the form of organo-metal complexes into the Bh horizons of the podzols. Greatest concentrations of Al are associated with coatings of monomorphic organic matter on mineral grains in the cemented Bh horizons, in which some Al has also crystallized into gibbsite. That mineral was not detected in friable B horizons of podzols nor in the low humic hydromorphic soil. Contrary to expectations, the mobile Al did not enter interlayer spaces of expanding 2:1 clay minerals.     

Buffering capacity of cashew soils in South Eastern Tanzania

Abstract. Cashew soils of South Eastern Tanzania become acidified due to sulphur used for controlling powdery mildew disease ( Oidium anacardii Noack). The buffering capacity of surface and subsurface horizons of 35 soil profiles of major cashew growing areas –- the Makonde plateau, its piedmont and inland plains –- was studied. The buffering capacity of surface and subsurface horizons was strongly correlated with clay content and weakly with organic carbon content. In addition, it was only weakly correlated with total exchangeable bases and available P of the surface horizon, but strongly with soil pH, base saturation and cation exchange capacity of the clay fraction of the subsurface horizon. Highly weathered sandy soils, dominant on the Makonde plateau and common on the Piedmont, had the lowest buffering capacity. Soils from the inland plains had better buffering capacities as they are generally more clayey or are less weathered. The risk of severe acidification and of a decline in productivity of cashew and of food crops is highest on the Makonde plateau. Further development and dissemination of methods which can reduce the use of sulphur are required.     

Chemical properties and pedogenesis of yellowish/yellow brown forest soils in the submontane and mountain zones of Kyushu district,southwestern Japan

Abstract

This study aimed to clarify pedogenetic processes and classification of yellowish Brown Forest Soils according to the Classification of Forest Soils in Japan and the Yellow Brown Forest soils according to the Unified Soil Classification System of Japan in the warm and cool temperate forest of Kyushu district, Japan. In addition, the study aimed to clarify a problem with the Unified Soil Classification System of Japan. Thirty-six soil profiles of Brown Forest Soils, including 13 yellowish Brown Forest Soils and 15 Yellow Brown Forest soils, were compared with regard to their chemical properties and the relationship with climatic conditions was assessed. The yellowish Brown Forest Soils had thin A horizons, low pH and low levels of free oxides in the B horizons, and a low amount of silica and a high aluminum and iron to silica ratio. These features were related to the paleo reddish weathering. The immaturely developed A horizon of the yellowish Brown Forest Soils was caused by these weathered, low-activity substances. The Yellow Brown Forest soils had low levels of active iron oxides and a low activity ratio of free iron oxides compared with the Haplic Brown Forest soils in the same thermal climatic conditions. The activity ratio of free iron oxides was correlated to mean annual air temperature with the carbon stocks and with many other chemical properties. Accordingly, classification of Brown Forest Soils was clearer according to thermal climatic conditions. The activity ratio of free iron oxides can become an effective index that distinguishes Yellow Brown Forest soils under warm temperate lucidophyllous forest and Haplic Brown Forest soils under cool temperate broad-leaved deciduous forest with considerable vertical soil zonality.     

Soil–landscape relationships at the lower reaches of a watershed at Bear Creek near Oak Ridge,Tennessee

The watersheds at Bear Creek, Oak Ridge, TN, have similar soil–landscape relationships. The lower reaches of many of these watersheds consist of headwater riparian wetlands situated between sloping non-wetland upland zones. The objectives of this study are to examine the effects of (i) slope and geomorphic processes, (ii) human impacts, and (iii) particular characteristics of soils and saprolite that may effect drainage and water movement in the wetlands and adjacent landscapes in one of these watersheds. A transect was run from west to east in a hydrological monitored area at the lower reaches of a watershed on Bear Creek. This transect extended from a steep side slope position across a floodplain, a terrace, and a shoulder slope. On the upland positions of the Nolichucky Shale, mass wasting, overland flow and soil creep currently inhibit soil formation on the steep side slope position where a Typic Dystrudept is present, while soil stability on the shoulder slope has resulted in the formation of a well-developed Typic Hapludult. In these soils, argillic horizons occur above C horizons on less sloping gradients in comparison to steeper slopes, which have Bw horizons over Cr (saprolite) material. A riparian wetland area occupies the floodplain section, where a Typic Endoaquept is characterized by poorly drained conditions that led to the development of redoximorphic features (mottling), gleying, organic matter accumulation, and minimal development of subsurface horizons. A thin colluvial deposit overlies a thick well developed Aquic Hapludalf that formed in alluvial sediments on the terrace position. The colluvial deposit from the adjacent shoulder slope is thought to result from soil creep and anthropogenic erosion caused by past cultivation practices. Runoff from the adjacent sloping landscape and groundwater from the adjacent wetland area perhaps contribute to the somewhat poorly drained conditions of this profile. Perched watertables occur in upland positions due to dense saprolite and clay plugging in the shallow zones of the saprolite. However, no redoximorphic features are observed in the soil on the side slope due to high runoff. Remnants of the underlying shale saprolite, which occur as small discolored zones resembling mottles, are also present. The soils in the study have a CEC of <10 cmol kg⁻¹, silt loam textures and Fe_d values of 0.5–4.3%. These soils are also mainly acidic and low in total carbon.     

Study of a toposequence for variability in micronutrients from the moist subhumid Siwalik agro-ecological subregion of Punjab

A toposequence from the moist subhumid Siwalik agro-ecological subregion ofPunjab was studied for available and total micronutrient variability. The toposequence showed the least developed soils with only an A–C horizon sequence on steep slopes and a well-developed profile with an argillic horizon on moderate slopes. The soils consist of a variety of minerals and thus belong to the mixed mineralogy class. There were higher levels of DTPA-extractable micronutrients in the surface horizon than in the subsurface horizon due to their association with organic matter through chelation and adsorption. The surface horizons have relatively lower total micronutrient contents than the subsoil horizons. Soils from moderate slopes and lower terraces showed higher total micronutrients contents in the middle horizons, suggesting some redistribution of the constituents due to the illuviation process of pedogenesis. DTPA-extractable and total micronutrients showed an irregular increasing trend from the steep slope to the lower terrace soils. The DTPA-extractable micronutrients showed relatively greater variability (8–107%) than the corresponding total micronutrient contents (2–34%), suggesting the relatively dynamic nature of the former. Variability in DTPA-extractable and total micronutrients within and among the different soils was caused by several processes involved in the differentiation ofmicronutrients. DTPA-extractable micronutrients show the influence of organic matter through the processes of chelation and adsorption, whereas total micronutrients varied due to differences in pedogenic processes of eluviation/ illuvial on different landscapes and textural variation.     

我国北亚热带白浆化土壤矿物学特性的研究

本文对北亚热带地区七个白浆化土壤的原生矿物和次生矿物的特性进行了研究。重，轻矿物含量表明土壤继承了母质的特性，粘淀层与漂白层的母质沉积是间断的，前者风化强度大于后者。石英颗粒表现特征显示漂白层物来来源于黄土物质再堆积，粘土矿物以水云母为主，其结晶度较差，氧化铁类型以针铁矿和赤铁矿为主，也有非晶质氧化铁和硅酸盐中的Ｆｅ＾２＋，其形成条件与现代化成土条件一致。     

EXTRACTABLE SESQUIOXIDES IN SIX MEDITERRANEAN SOILS DEVELOPED ON BASALT AND SCORIA

Iron, Al, and Mn were extracted by oxalate and dithionite from two Brown Mediterranean Soils, two Red Mediterranean Soils, one Vertisol and one Gley soil, all derived from basalt or scoria in the sub-humid and humid Mediterranean regions of the Golan Heights. Ratios of oxalate: dithionite extracted iron (Fe_o:Fe_d) were low in all soils, indicating that the predominant form of free iron is crystalline. Fe_o accumulates in the argillic B horizons of the Mediterranean soils, while Fe_d accumulates in the surface horizons. A large part of the free iron oxide in the surface horizons of Mediterranean soils is associated with non-clay fractions. While manganese behaves in a manner somewhat similar to that of iron, no definite trends could be discerned in the vertical distribution of free aluminium. In the Vertisol, Fe_o and Mn_o accumulate in the subsoil. Fe_d and Mn_d increase slightly with soil depth. In the Gley soil, amorphous iron accumulates in the surface horizon, total free iron in the bottom horizon. Both amorphous and total free Mn had been depleted from the upper horizons of the Gley soil.     

Linking fragipans,perched water tables,and catchment-scale hydrological processes

Soils with very slowly permeable fragipans and fragipan-like argillic horizons are extensive throughout the Palouse Region of northern Idaho and eastern Washington, USA. These soils develop seasonal perched water tables (PWTs) under the xeric moisture regime of the region. The objective of this study was to utilize a hydropedology approach to examine the linkages between fragipans, PWTs, and catchment-scale hydrological processes such as soil water storage, runoff, and lateral throughflow. A 1.7-ha catchment dominated by Fragixeralfs (Fragic Luvisols) was instrumented with 135 automated shallow wells to monitor PWTs. Soil water content was measured with water content reflectometry probes, and catchment outflow was measured with a flume. A 35 m × 18 m plot was isolated hydrologically from the surrounding hillslope using tile drains and plastic sheeting to measure perched water outflow. Results show that during the wet winter and spring months, the transition from unsaturated to saturated conditions is accompanied by changes in volumetric water storage of only 4–5%. PWT levels are at the surface of ∼ 26–45% of the catchment soils during periods of high rainfall and snowmelt, thereby generating saturation-excess surface runoff from hillslopes. Observed solute movement via subsurface flow is very rapid and ranges between 2.9 and 18.7 m d^− 1 when PWTs are maintained in more-permeable Ap and Bw horizons. Subsurface lateral flow accounts for as much as 90% of the incident precipitation and snowmelt during early spring. Data indicate that the relatively shallow depth to the fragipans and high K_sat in surface soil layers combine to create a very flashy hydrological system characterized by considerable temporal and spatial variation in patterns of saturation-excess runoff.     

Regolith and soils in Bhutan, Eastern Himalayas

Bhutan lies at altitudes of 100–7500 m on the steep, long and complex southern slopes of the Eastern Himalayas. Soil surveys show that, despite steep gradients, there are many moderately or deeply weathered soils. Many slopes are mantled with polycyclic, layered drift materials, so soil horizons owe as much to regolith heterogeneity as to pedogenesis. In the limited arable areas soil profiles are further complicated by rice cultivation and the construction, maintenance and irrigation of flat terraces on steep slopes. Some natural pedogenic horizonation is apparent, and there is an altitudinal zonation of soil types. Although the climate is warm and seasonally wet, most soils on the subtropical southern foothills are not particularly weathered and leached. The foothills are seismically active, and many soils are formed in unstable landslide debris. Elsewhere the regoliths are more stable. The main soils up to about 3000 m in the inner valleys are moderately weathered and leached, and have bright subsoil colours and thin dark topsoils. Above these there is a zone of bright orange‐coloured non‐volcanic andosolic soils. Further upslope there are acid soils with thick surface litter, stagnogleyic topsoils, and drab brown subsoils with organic cutans. These grade to weak podzols, which extend from about 3500 m up to the treeline, around 4000 m. Above this, alpine turf soils, with deep, dark, and friable topsoils and yellowish friable subsoils, are intermixed with unweathered glacial deposits. The interactions between pedogenesis and the deposition of the varied and layered drift materials complicate mapping and classification of the soils.     

Lateral flow in loamy to sandy Kandiudults of the Upper Coastal Plain of Georgia (USA)

Interest in site-specific agronomic management in intensively cropped regions necessitates characterization of subsurface water movement for efficient water management (irrigation timing) and control of off-site agrichemical movement. Soils formed in fluvial sediments in portions of the Upper Coastal Plain of Georgia (USA) are extensively used for peanut, cotton, and corn production. Certain proximate soils in this region possess contrasting subsoil properties, and it was hypothesized that these differences would have major effects on water redistribution across the landscape. This could be important in irrigation management, where soils possessing increased impedance to vertical flow could require decreased irrigation as opposed to soils without vertical flow restrictions. At a site near Plains, GA. (USA), hydraulic properties of soils with differences in overlying sand thickness and contrasting argillic horizon textures (sandy vs. loamy) were evaluated. The soils were predominantly in loamy and sandy families of Typic, Arenic, and Grossarenic Kandiudults. Laboratory measurements, field monitoring of matric potentials under simulated and natural rainfall, and modeling (VS2DT) were utilized to evaluate soil hydraulic properties. Reduction in vertical K_s occurred in horizons containing higher clay (argillic horizon). Changes in tension and build ups in hydraulic gradients associated with infiltration and redistribution events existed above and within horizons with low K_s. Evidence suggested there was less groundwater recharge occurring in the loamy than in the sandy pedons, suggesting more pronounced lateral flow occurred in the loamier soils. Model simulations of water movement across a slightly sloping (1%) simulated landscape indicated lateral gradients of flow existed within the solum of these soils. Analyses of tracer (Br) movement suggested a very slight lateral redistribution occurred within a relatively short monitoring period within the sandy pedon's Bt1 horizon, and the Bt2 and Bt3 horizons of the loamy pedon. Evidence suggested both loamy and sandy argillic horizons slightly, but not overwhelmingly, induced lateral flow on these landscapes.     

Cryo-geomorphological evolution of soils on islands of Terekhol Lake,Tyva, Southern Siberia

Specific soils on calcareous lacustrine sediments have been described on the islands in the Terekhol Lake, Terekhol’skaya intermontane trough of the Tuva Upland. The islands themselves originate from frost heaving cycles as shown by their relief and interfacial analysis of litho- and biostratigraphy of dated cores sampled in the bottom of the lake and on the islands. Soils of two altitude-age groups (generations) of islands have been studied. Younger islands (400–1700 cal yrs BP) have relative heights above the lake level below 2.5 m and an active layer 0.6–1.5 m thick. Histic Cryosols (Limnic, Drainic) were found there. Soils are well drained now and have no relation with the lake waters. The central elevated parts of older, and higher islands (4000–5000 cal yrs BP; 2.5–4.5 m, active layer about 1.5 m thick) are under dry-steppe phytocenoses on Calci-Mollic (Histic) Cryosols (Limnic, Calcaric, Gypsiric). The following evolution phases of islands and their soils were reconstructed. The lacustrine sediments were raised from the sedimentation zone to remain in subaerial conditions, where Histic Cryosols were formed. Owing to heaving, an admixture of limnic material was included in them. Further heaving resulted in the isolation of soils from the lake waters, the sedimentation completely stopped, and pedogenesis slowly shifted toward that inherent to well-drained conditions under dry-steppe vegetation. Histic horizons got degraded and transformed to mollic ones, the permafrost table moved deeper, carbonates, gypsum and soluble salts were leached from the upper horizons.     

Soils and slopes in a humid temperate environment: A simulation study

A three dimensional simulation of the landsurface system is presented, which includes the processes of weathering, soil creep and fluvial erosion. Soils represent a deposit in equilibrium between the processes of weathering and erosion. The simulated drainage basin with a fixed exit point reproduces the “closed” system dynamics of the Davisian model, in which however slopes still attain a dynamic equilibrium form. Within the basin the overall mean soil depth very rapidly reaches a constant value even though a considerable redistribution of material is still to occur. This implies a rapid establishment of a balance between the process of weathering and erosion. By contrast the detailed pattern of soil depths on individual slopes is established much more slowly, only after the slopes themselves come to equilibrium. The equilibrium configuration of soils under soil creep shows a slight downslope increase in depths, and major increases in soil depth are restricted to locations where external constraints force an accumulation of material.     

Bodenformen und Bodenabtrag in den Hochlagen der axialen Pyrenäen

Soil types and erosion phenomena at high elevations of the axial Pyrenees Two soil toposequences are described for the high altitude valley of Benasque (axial Pyrenees, Northern Spain, elevation 1800–2400 m a.s.1.). Deeply weathered cambisols (mostly dystric and eutric) are developed from quaternary deposits of paleozoic sedimentary and metamorphic rocks. These soils are mostly under grass cover and strongly grazed. The physical and chemical properties of these cambisols and the corresponding erosion phenomena are described. In one toposequence (Ampriú) a specific form of soil erosion called “regressive topsoil denudation” is common and correlated with soils developed from stratified substrates with sandy top soil overlying clayey and silty horizons.     

The morphology and genesis of eight surface-water gley soils developed in till in England and Wales

The morphology is described of eight surface-water gley soils developed in til in Wales and central and northern England. Physical and chemical analyses as well as micromorphological observations are used to investigate processes affecting the genesis of the soils. The characteristic property of surface-water gley soils, namely slowly permeable subsurface horizons, causes a degree of periodie waterlogging within the profile. Effects of gleying and shrink/swell processes are described. Three main aspects of weathering are shown to be operating: decalcification in two of the three calcareous profiles, the breakdown of coarse into finer particles and the alteration of the clay fraction, chiefly the formation of mixed-layer minerals from mica. Argillic B horizons are present in some soils. In profiles developed in calcareous till the degree of decalcification relates strongly to the amounts of recognizable clay concentrations as seen in thin section. Of the other five profiles three clearly have argillic B horizons. Problems associated with the identification of argillic B horizons in surface-water gley soils in till are discussed.     

Changes in the soil microbial community structure with latitude in eastern China, based on phospholipid fatty acid analysis

Phospholipid fatty acid (PLFA) profiles were measured in soils from 14 sites in eastern China representing typical geographic zones of varying latitude from north (47.4°N) to south (21.4°N). Amounts of soil microbial biomass, measured as total amounts of PLFAs, showed no regular trend with latitude, but were positively correlated with soil organic carbon content, the concentration of humic acid and amorphous iron oxide. Soil microbial community structure showed some biogeographical distribution trends and was separated into three groups in a cluster analysis and principal coordinate analysis of log transformed PLFA concentrations (mol%). Soils in the first group came from northern China with medium mean annual temperature (1.2–15.7 °C) and rainfall (550–1021 mm). Soils in the second group originated from southern China with a relatively higher mean annual temperature (15.7–21.2 °C) and rainfall (1021–1690 mm). Soils clustered in the third group originated from the most southerly region. The northern soils contained relatively more bacteria and Gram-negative PLFAs, while the southern soils had more fungi and pressure indexed PLFAs. These differences in soil microbial community structure were largely explained by soil pH, while other site and soil characteristics were less important.     

A quaternary soil sequence in the Kennet Valley,central southern England

The field characteristics, texture, mineralogy and micromorphology of the soils of four chronologically separate river terraces of the River Kennet are described. The soils on the three uppermost terraces have illuvial (palaeoargillic) horizons, which have been intensely disturbed by periglacial activity. These horizons are overlain by similarly disrupted eluvial horizons mixed with aeolian silts derived from outside the Kennet catchment. The illuvial horizons most probably result from interglacial pedogenesis under climatic conditions warmer and wetter than at present, whilst the aeolian material was probably added to the soils during the last glacial period (Devensian). The lowest and youngest terrace is characterised by an undisturbed (normal argillic) soil developed in loams derived predominantly from the aeolian silts. Consequently, it is postulated that the soils of the lowest terrace owe their characteristics to a phase of postglacial pedogenesis.The results illustrate that several phases of pedogenesis can be recognised, which provide important information on the Quaternary development of the area. This is especially significant where floral, faunal, or archaeological evidence of environmental changes is unavailable.