Degree Of Soil Development Research Articles

Magnetic enhancement is linked to and precedes hematite formation in aerobic soil

Soil formation usually increases magnetic susceptibility, most often by increasing the concentrations of magnetite and maghemite, which are two ferrimagnetic iron oxides. Here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite, which is later transformed into hematite—the iron oxide that gives red color to soil. We show that the maghemite/hematite ratio is influenced by the particular environment and the degree of soil development, so it constitutes an effective tool for paleoenvironmental and planetary studies.

Geomorphological and pedological investigations on the glacial history of the Kali Gandaki (Nepal Himalaya)

In semi-arid orographic left tributaries of the Kali Gandaki at the northern and western flank of the Nilgiri Himal, glacio-geomorphological and pedological investigations were carried out on prehistoric moraines. Geomorphological relief analysis was derived from other literature and the own fieldwork of the author. The resulting glacial chronology was used as benchmark to explore the limits of different pedological dating methods regarding the degree of soil development. These methods are based on iron fractionation, total element contents and particle size distribution. In general the different glacial stages are mirrored correctly in the relative graduation of soil development. The ratio of well crystallised pedogenic iron-oxides to the total iron content and the ratio fine clay to total clay are most suitable, because they are almost independent from existing changes in the lithological composition. The total element based weathering indices are less suitable, because they react highly sensitive to the geology dependent shift to higher carbonate content. Most of the grain size based weathering indices are inapplicable because of the typically high textural variability within till deposits.

Paleosols derived from loess and loess-like sediments in the Basin of Persepolis, Southern Iran

In the Basin of Persepolis, late Quaternary basin fills consist of loess, loess-like sediments and fine- or coarse-textured alluvium. The loess and its derivatives are divided by various paleosols, which consist of well-developed fBw(t)-horizons, weakly developed fBwC- and fBwgC-horizons, as well as fAh-horizons. Strongly developed fBtk-horizons occur in stony alluvial fan deposits or superimpose residual loams of carbonate bedrock mixed with loess. The different types of paleosols result from various degrees of soil development as evidenced by micromorphological features such as the birefringence fabrics, and less clearly by pedochemical properties. Based on the stratigraphy and different degrees of soil development, various phases of soil formation and sediment deposition can be distinguished. Infrared optically stimulated luminescence (IRSL), thermoluminescence (TL) and radiocarbon dating methods are consistent with the stratigraphy and yielded, except for one sample, age estimates of less than about 30 ka. The strongly developed fBw(t) and fBtk horizons reflect soil-forming periods prior to the Last Glacial Maximum (LGM) and probably during Marine Isotope Stage 5 (MIS 5), with climatic conditions comparable to the present-day. The upper loess deposits likely formed under considerably cooler and drier climatic conditions during the LGM. However, poor bleaching of sediments prior to final deposition, as indicated by greater TL than IRSL dates, suggest fluvial reworking of these loesses. The weakly developed fAh, fBwC, and fBwgC horizons may indicate interstadial periods of MIS 3 and short phases of climate amelioration during the early Holocene. The formation of the modern soil probably did not start before 7–9 ka.

Soil–landform development of a part of the fold belt along the eastern coast of Bangladesh

The evolution of landforms and soils from the Jaldi and Maiskhali anticlines and adjoining areas in a part of the coastal region of the north–south trending fold belt of Bangladesh during the Late Quaternary Period has been investigated. Based on the degree of soil development and luminescence dating, eight soil geomorphic units have been deciphered and grouped into four members (I–IV) of a morphostratigraphic sequence for the study area. Various soil geomorphic units included in different member/sub-members are: Member I—river floodplains and active tidal flats (< 500 years); Member II—distal Piedmont Plains and old tidal flats (0.5–2 ka); Member III—proximal Piedmont Plains (6–10 ka); and Member IV—Mainland Higher and Lower Hillocks and Island Hillocks (> 15 ka). Member IV is further subdivided into Sub-member IVa—Island Hillocks (15–18 ka); Sub-member IVb—Mainland Lower Hillocks (23–25 ka); and Sub-member IVc—Mainland Higher Hillocks (30–35 ka). The youngest and poorly developed soils of Member I show features related to hydromorphism. Moderately developed soils of Members II and III show a fersiallitisation stage of pedogenesis. Member IV includes ‘strongly developed soils’ with a ferrugination stage of pedogenesis. These soils also exhibit degradation and poor birefringence of argillans and ferriargillans, indicating a significant change in conditions of pedogenesis, probably related to a paleoclimatic change from a subhumid to semiarid phase (40 ka to about 16 ka) to a hot humid to subhumid phase (16 ka–present). Parent material composition and physiography also have affected the pedogenesis in the area. Based on ages and heights above the mean sea level for the five terraces recognized in the study area, the overall base-level rise rates calculated are about 3.6 mm/year (18 ka–present) for the Maiskhali Island and 2.86 mm/year (35 ka–present) for the mainland (Jaldi anticline). These base level changes represent combined effects of eustatic sea level and tectonic uplift due to folding.

Nutrients and Trace Elements of Arable Soils Rich in Organic Matter

The distribution and the status of macronutrients and trace elements in surface soil samples originated mainly from organic deposits of Philippoi (northern Greece) were investigated. These soils are classified as Histosols and belong to the suborder of Saprists (1). The pH of examined samples ranged from 5.1 to 7.8 and the total soil nitrogen (Ntot) varied from 4.0 to 21.8 g kg−1. The total soil carbon (Ctot) ranged between 116.0 and 336.5 g kg−1, whereas the organic carbon (Corg) was between 109.4 and 335.5 g kg−1 and the C:N ratio varied between 12.4 and 29.3. Calcium carbonate (CaCO3) was not detected in all surface horizons, and the exchangeable calcium (Ca++) ranged between 12.95 and 54.65 cmol kg−1. This suggests the impact of aquatic organisms (which contain CaCO3) on soil enrichment with calcium by means of weathering process. Micronutrients extracted by 4 M HNO3 were in the following order iron (Fe)>manganese (Mn)>zinc (Zn)>copper (Cu). The distribution of trace elements extracted by DTPA varied considerably among the examined soil samples. The following range was found: Fe 97.5–579 mg kg−1, Mn 1.48–53.0 mg kg−1, Cu 0.24–10.4 mg kg−1, and Zn 0.5–23.9 mg kg−1. Total soil nitrogen was closely related to Corg, whereas soil properties showed considerable variability. This may reveal the factors responsible for deposition process, degree of soil development; part of this distribution may be attributed to intensive farming activities. Symptoms of Fe deficiency have been observed, which may be ascribed mainly to the presence of CaCO3. Deficiency of Cu was also recorded in maize (Zea mays L.) cultivated in slightly alkaline soils. Geostatistics have been used for a quantitative depiction in maps of nutrient status and variability. A combination of measures, such as water management, tillage practices, application of proper rotation schemes, and recommendation of rational fertilization practices, is expected to maintain soil quality and enhance fertility.

Duration dependence of magnetic susceptibility enhancement in the Chinese loess–palaeosols of the past 620 ky

Past climate has been interpreted from the loess–palaeosol record found in China. There is no argument that the palaeosols are more strongly weathered than the underlying less well-weathered loess and that these changes have been governed by glacial/interglacial climate fluctuations. However, the duration of pedogenesis may have also contributed to the development of palaeosol properties. Previous studies have not attempted to separate these two factors which both affect the intensity of soil formation, and have assumed that the degree of soil development and pedogenic magnetic susceptibility enhancement depended solely on the climate conditions. We show that the magnetic susceptibility enhancement of palaeosols of the lower Malan and upper Lishi Formations (S 1–S 5 correlated to the interglacials of the past 620 ky) depends partly on the duration of pedogenesis. This suggests that pedogenic magnetic susceptibility enhancement of palaeosols should not be used for such direct palaeoclimate reconstructions as determining the amount of rainfall or the temperature of the soil-forming intervals. However, used in combination with other proxies (other magnetic properties, % Fe d, Fe d/Fe t, color indices, the depth of decalcification, particle size), magnetic properties of palaeosols and loess layers can provide valuable insight into climatic conditions of soil-forming episodes. It follows that multiproxy evidence provides better insight into climate dynamics than the interpretation of a single proxy.

Origin, distribution and age of high-level chert gravels (Plio-Pleistocene) in eastern Kansas

It is probable that the rounded flint has partly originated from these [Flint] hills. G.C. Broadhead (1880).High-level (upland) chert [flint] gravels occur in almost all of the counties in the Osage Cuesta country of eastern Kansas. The locations of the high-level chert gravel deposits now are well known as a result of recent remapping of the state on a scale of 1:24:000, but the origin and age of the chert gravels remain as debatable today as they were 125 years ago. The gravels are composed of brownish, smooth, angular to subangular chert pebbles and cobbles ranging up to 6 inches (15 cm) in size.The chert clasts have been derived from Lower Permian limestones that contain abundant chert [flint] and crop out in the topographically high Flint Hills in east-central Kansas. The chert weathers from the limestones to create lag gravels, which in turn are reworked and transported eastward and southeastward by streams.In the glaciated region in northeastern Kansas, remnants of high-level chert gravel deposits occur in association with glacial tills, outwash, and erratics. In places the chert gravels occur beneath glacial deposits. South of the glaciated region, however, the remnants of the high-level gravels occur on bedrock surfaces whose elevations range from 20 to 200 feet (6 to 60 m) above the floodplains of major streams.The chert itself that forms the gravels is known to be Early Permian in age, based on fossils preserved in the pebbles and cobbles. Deposition of the high-level gravels, however, cannot be dated directly, but information bearing on their relative ages is provided by the degree of soil development over them and their elevations with respect to modern floodplains. Deposits at higher elevations may be Pliocene, whereas deposits at lower elevations may be early to middle Pleistocene. Chert gravels that occur on low-lying floodplains and in modern alluvium and are judged to be late Pleistocene to Recent in age.

PEDOGENIC INTERPRETATION OF A LOESS-COVERED, PLEISTOCENE-GLACIATED TOPOSEQUENCE USING THE ENERGY MODEL

Runge's energy model is one of several models of soil development that have been suggested in the last three-quarters of a century. This energy model includes three factors that affect the amount of energy input to a soil system (i.e., time, organic matter production/accumulation, and water available for leaching through the profile) and can be used to differentiate soil development among similarly classified soils in a defined landscape setting. In the context of the energy model, soil development was evaluated for four Typic Argiudolls along a toposequence in a loess-covered, glaciated landscape in south-central Wisconsin. Time was considered constant since loess was deposited at all sites during the last glaciation. Interpretations of pedogenic development along the toposequence were made in the context of the energy model based on soil surface organic matter and soil profile carbon (C) concentrations, measured water fluxes through undisturbed soil using tension lysimeters, a qualitative water-balance assessment, and clay content profiles. Pedogenic interpretations based on field observations and measurements were supported by estimates of relative kinetic energy input to the soil system from moving water and relative potential energy inputs stored in the existing soil C pool. Therefore, it was concluded that Runge's energy model accurately indicated variations in the degree of soil development in similarly classified soils along a toposequence. The results of this study represent the first of its kind to quantify and interpret differential soil development based on units of energy input, as the energy model was originally intended. The results of this study also indicate that Runge's energy model could be a useful tool in the prediction of soil morphological response to future land-use and/or hydrologic change in areas where the taxonomic classification of a soil mapping unit does not provided sufficiently specific information.

Spatial Correlation Between Land Development Level and Vulnerability Level of Mass Movement in the Watershed of Kayangan, Kulon Progo Regency, Yogayakarta Special Region

The objective of this research were: 1) to study the degree of soil development, and 2) to study the spatial correlation between the degree of soil development and the degree of mass movement susceptibility in the research area. The sampling method applied in this research was stratified sampling. Soil mapping units were applied as strata. The sample within strata was determined according the degree of mass movement susceptibility. The degree of soil development was determined using quantitative method of color indices and proflie index. The color indices were Buntley – Westin (B – W), Harden (H), and Hurst. The profile index was determined using solum, texture, structure, and soil consistency. The degree of mass movement susceptibility map was taken from PSBA UGM (2001). Spatial correlation between the soil development map and the mass movement susceptibility map was analyzed using “error matrix”. The result of this research indicated that the degree of soil development in the research area could be classified into three classes, i.e. class 1 (weakly develop soil); class 2 (moderately developed soil), class 3 (strongly developed soil). The degree of mass movement susceptibility was classified into three classes, i.e. class 1 (low susceptibility), class 2 (moderate susceptibility), and class 3 (high susceptibility). The result of error matrix calculation between mass movement susceptibility and soil development were 9.56%; 21.96%; 30.21% for BW + Ha, Hurst, and profile indices respectively. There values showed that there were low spatial correlations between the degree of soil development and mass movement susceptibility in the study area.

Complex exposure histories of chert clasts in the late Pleistocene shorelines of Lake Lisan, southern Israel

AbstractActivities of 26Al and 10Be in five chert clasts sampled from two beach ridges of late Pleistocene Lake Lisan, precursor of the Dead Sea in southern Israel, indicate low rates of chert bedrock erosion and complex exposure, burial, and by inference, transport histories. The chert clasts were derived from the Senonian Mishash Formation, a chert‐bearing chalk, which is widely exposed in the Nahal Zin drainage basin, the drainage system that supplied most of the material to the beach ridges.Simple exposure ages, assuming only exposure at the beach ridge sampling sites, range from 35 to 354 ky; using the ratio 26Al/10Be, total clast histories range from 0·46 to 4·3 My, unrelated to the clasts' current position and exposure period on the late Pleistocene beach ridges, 160–177 m below sea level. Optically stimulated luminescence dating of fine sediments from the same and nearby beach ridges yielded ages of 20·0 ± 1·4 ka and 36·1 ± 3·3 ka. These ages are supported by the degree of soil development on the beach ridges and correspond well with previously determined ages of Lake Lisan, which suggest that the lake reached its highest stand around 27 000 cal. years BP.If the clasts were exposed only once and than buried beyond the range of significant cosmogenic nuclide production, then the minimum initial exposure and the total burial times before delivery to the beach ridge are in the ranges 50–1300 ky and 390–3130 ky respectively. Alternatively, the initial cosmogenic dosing could have occurred during steady erosion of the source bedrock. Back calculating such rates of rock erosion suggests values between 0·4 and 12 m My−1. The relatively long burial periods indicate extended sediment storage as colluvium on slopes and/or as alluvial deposits in river terraces. Some clasts may have been stored for long periods in abandoned Pliocene and early Pleistocene routes of Nahal Zin to the Mediterranean before being transported again back into the Nahal Zin drainage system and washed on to the shores of Lake Lisan during the late Pleistocene. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Holocene loess accumulation and soil development at the western edge of the Chinese Loess Plateau: implications for magnetic proxies of palaeorainfall

A high-resolution Holocene sequence of loess, palaeosols and incipient soils at the western edge of the Chinese Loess Plateau, dated using optically stimulated luminescence techniques, is used to identify the respective influence of dust accumulation rate, time and climate on soil magnetic properties. Dust deposition and soil formation have both been quasi-continuous through the Holocene at this site; the soils are thus accretionary in nature. The degree of soil development (as indicated both by geochemical and magnetic properties, which correlate strongly) varied through the Holocene. Compared with the less-weathered loess units, each palaeosol is enriched in nitrogen and organic carbon, depleted of carbonate due to leaching, and displays higher values of pedogenic magnetic susceptibility, frequency-dependent susceptibility (%), remanences and magnetisation. Magnetic grain size indicators show that the pedogenic ferrimagnets are ultrafine, of single domain and superparamagnetic dimensions. Sediment accumulation rates were lowest from ∼12 to 2.5 ka, providing ample time (100 s of years) for weathering and soil formation to proceed, yet pedogenesis through this interval was relatively weak. Conversely, soil development was stronger during later intervals—when loess accumulation rates were higher, and soil-forming intervals were correspondingly shorter. In terms of Jenny's (1941) soil-forming equation, accumulation rate (and thus time), sediment source (parent material) and topography show no systematic variation between the loess and the palaeosols. Therefore, climate seems to be the key soil-forming factor which has controlled the geochemical and magnetic properties of these Holocene palaeosols.

Schätzung der mikrobiellen Biomasse von Böden aus anthropogenen und natürlichen Substraten — ein Beitrag zur Standortbewertung

Whereas the estimation and evaluation of physical and chemical soil properties is possible with the use of widely accepted methods, there is still no procedure with respect to microbiological parameters. Therefore, our objective was to develop a field procedure for estimating the integral parameter microbial biomass. For this purpose, microbial biomass data (C mic in dry matter) of soils developed in natural parent materials from 116 sites in Germany and abroad were analyzed. Additionally, C mic in 33 German soils developed in anthropogenic parent materials was determined. In the soils under consideration, C mic varied between 100 and 4000 kg ha -1 in the upper 30 cm. For soils of natural substrates statistical relations between C mic and the humus and clay content as well as pH were derived. From these parameters which are combined as the diagnostic characteristics of humus a simple procedure for estimating C mic of arable soils was developed. For soils developed in anthropogenic parent materials, however, an estimation procedure was developed that uses the nature of the parent material and the degree of soil development. To evaluate the estimated amount of C mic , a frame consisting of 6 classes is proposed: 3200 kg ha -1 (= very high).

Use of Soils to Identify Glacial Deposits of Various Ages East of Glacier National Park, Montana, U.S.A.

Degree of soil development increases with age of parent materials in the zone of confluence of continental and alpine piedmont glaciers east of Glacier National Park, Montana. Surficial deposits are assigned to three, possibly four, glacial events on the basis geomorphic and pedologic evidence. Based on over 100 profiles examined, soils in late Wisconsin till and outwash are typically Cryoborolls and Cryochrepts with 0- to 62-cm-thick, brown cambic (Bw) horizons and 50+- cm-thick calcic (Bk) horizons with Stage II to II+ carbonate morphology. Soils in late Illinoian or early Wisconsin sediments are Argiborolls or Argic Cryoborolls with 34- to 92-cm-thick, dark yellowish brown argillic (Bt) horizons and those in Illinoian sediments are strongly developed Paleudolls with 51- to 54-cm-thick, yellowish red argillic horizons. Soils on Number 1 and 2 Bench remnants (considered Pliocene to early Pleistocene in age) are very strongly developed Paleudolls with about 2.5-m-thick, leached, yellowish red argillic horizons. Properties which best reflect relative soil age include thickness of argillic horizon, depth of leaching, depth of oxidation, Harden profile index, Harden rubification index, and clay accumulation index.

Spatial variability of soils developing on basalt flows in the Potrillo volcanic field, southern New Mexico: prelude to a chronosequence study

If the systematic spatial variability of soils in a chronosequence is identified and accounted for, the accuracy of quantitative data derived from soil chronosequence studies will be increased. A sample design using landscape positions with minimal variability could result in more accurate chronofunctions from these studies. Four basalt flows in the Potrillo volcanic field, southern New Mexico, with ages ranging between 20 ka and 260 ka (40Ar/39Ar and/or cosmogenic 3He methods) provide a sound basis for a soil chronosequence study. Basalt flow surface relief in the Potrillos reduces with time as depressions fill with basalt rubble and aeolian dust. Soil variability is primarily a function of landscape position with respect to ridges and swales in the original basalt flow topography. Soils developing over original topographic lows (swale soils) form primarily in aeolian dust, have larger amounts of total carbonate and soluble salts, and display greater variability than soils developing over original topographic highs (ridge soils). It is thus concluded that ridge soils, which have minimal variability, should be employed for a soil chronosequence study of basalt surfaces in the Potrillo volcanic field. The spatial variability of swale soils results in part from the significant hydrologic variability of low-lying landscape positions. Depth profiles of chloride concentrations suggest that hydrologic variability systematically correlates with the size and shape of depressions in which soils are forming. The infilling of depressions with aeolian material results in increasingly arid hydrologic conditions both by increasing the volume of aeolian material that is being drained and by reducing the catchment area for runoff into the depression. Depressions fill at different rates, however, depending on their size, shape and catchment area. Small, narrow depressions fill quickly, and their associated soils form under more arid conditions and have stronger development than soils in large depressions. Therefore, a number of geomorphic surfaces of varying age may develop on a single isochronous basalt flow. Each of these surfaces will have unique hydrologic characteristics and consequently different degrees of soil development. The pre-burial high water flux evident in depressions suggests that basalt flows may play an important role in aquifer recharge in this area of New Mexico. Copyright © 1999 John Wiley & Sons, Ltd.

Spatial variability of soils developing on basalt flows in the Potrillo volcanic field, southern New Mexico: prelude to a chronosequence study

If the systematic spatial variability of soils in a chronosequence is identified and accounted for, the accuracy of quantitative data derived from soil chronosequence studies will be increased. A sample design using landscape positions with minimal variability could result in more accurate chronofunctions from these studies. Four basalt flows in the Potrillo volcanic field, southern New Mexico, with ages ranging between 20 ka and 260 ka (40Ar/39Ar and/or cosmogenic 3He methods) provide a sound basis for a soil chronosequence study. Basalt flow surface relief in the Potrillos reduces with time as depressions fill with basalt rubble and aeolian dust. Soil variability is primarily a function of landscape position with respect to ridges and swales in the original basalt flow topography. Soils developing over original topographic lows (swale soils) form primarily in aeolian dust, have larger amounts of total carbonate and soluble salts, and display greater variability than soils developing over original topographic highs (ridge soils). It is thus concluded that ridge soils, which have minimal variability, should be employed for a soil chronosequence study of basalt surfaces in the Potrillo volcanic field. The spatial variability of swale soils results in part from the significant hydrologic variability of low-lying landscape positions. Depth profiles of chloride concentrations suggest that hydrologic variability systematically correlates with the size and shape of depressions in which soils are forming. The infilling of depressions with aeolian material results in increasingly arid hydrologic conditions both by increasing the volume of aeolian material that is being drained and by reducing the catchment area for runoff into the depression. Depressions fill at different rates, however, depending on their size, shape and catchment area. Small, narrow depressions fill quickly, and their associated soils form under more arid conditions and have stronger development than soils in large depressions. Therefore, a number of geomorphic surfaces of varying age may develop on a single isochronous basalt flow. Each of these surfaces will have unique hydrologic characteristics and consequently different degrees of soil development. The pre-burial high water flux evident in depressions suggests that basalt flows may play an important role in aquifer recharge in this area of New Mexico. Copyright © 1999 John Wiley & Sons, Ltd.

Soil Development and Fertility Characteristics of a Volcanic Slope in Mindanao, the Philippines

Thirteen pedons representing the mountains, the upper footslopes, the lower footslopes, and the alluvial terraces of a volcanic slope in Mindanao, the Philippines were studied to understand relationships between the degree of soil development and fertility characteristics. Soils in the upper and the lower footslopes were Oxisols as were soils in the alluvial terraces, while those in the mountains were Ultisols and Inceptisols. Presence of “amorphous components”, such as allophane and imogolite, in all the pedons studied was indicated by a &gt;9.4 soil pH in NaF. Halloysite, gibbsite, goethite, hematite, and cristoballite were more common minerals in the clay fraction. Surface layers of all the pedons were slightly acidic and pH increased by depth. Phosphate sorption maxima ranged from 6944 to 14208 μg P g−1, and it was closely associated with oxalate‐extractable Al (Alo) and clay content. Inceptisols had higher phosphate sorption maxima than Oxisols. Soil samples representing the mountains showed the lowest level of both the available K and the potential buffering capacity for K (PBCK), while the upper footslopes had the highest level of available K. The PBCK values were lower for Inceptisols than for Oxisols, and they were found to be positively correlated with soil pH. There was a large difference between the cation‐exchange capacity (CEC) and the effective cation‐exchange capacity (ECEC), an indication of a large pH‐dependent charge. Mountain soils showed lower base saturation than soils representing the upper footslopes, the lower footslopes, and the alluvial terraces.

Distribution of iron and manganese oxides in Haploxeralfs and Rhodoxeralfs and their relation to the degree of soil development and soil colour

AbstractThe status and the distribution of iron and manganese oxides were studied in six soil profiles from Thrace region (Greece), classified as Rhodoxeralfs and Haploxeralfs. The acid ammonium oxalate and the dithionite‐citrate‐bicarbonate methods were used to extract the free iron and manganese oxides from the soils. In both great groups the Fed and Mnd values are higher than Feo and Mno values, respectively, indicating that a considerable fraction is present in crystalline form. Both Feo/Fed and Fed‐Feo values suggest that, in the study area, Haploxeralfs are less developed soils than Rhodoxeralfs. The manganese oxides present in crystalline forms (Mnd‐Mno) were more in Rhodoxeralfs than in Haploxeralfs, suggesting that the crystallinity of manganese oxides increases, with the degree of soil development. Significant correlations were found of Redness Rating to Fed‐Feo and to Feo/Fed ratio, positive and negative respectively, leading to the conclusion that soil red colouration increases with the degree of soil development.

Active tectonics at Wheeler Ridge, southern San Joaquin Valley, California

Wheeler Ridge is an east-west–trending anticline that is actively deforming on the upper plate of the Pleito–Wheeler Ridge thrust-fault system. Holocene and late Pleistocene deformation is demonstrated at the eastern end of the anticline where Salt Creek crosses the anticlinal axis. Uplift, tilting, and faulting, associated with the eastward growth of the anticline, are documented by geomorphic surfaces that are higher and older to the west. Faulting and associated folding is propagating eastward, as indicated by increases in both the degree of surface dissection and the degree of soil development from east to west. Distinct topographic areas having distinct degrees of surface dissection, bounded by tear faults, suggest that faulting and folding have propagated eastward in discrete segments. Numerical dates indicate (1) the anticline is propagating eastward at a rate of about 30 mm/yr (about 10 times the rate of uplift); (2) folding was initiated about 400 ka; (3) a prominent wind gap was formed during Q3 time (about 60 ka) when an antecedent stream was defeated, forcing the stream east around the nose of the fold; today drainage through the ridge is by way of two antecedent streams (water gaps) east of the wind gap; and (4) the rate of uplift at the easternmost and youngest (past 1 k.y.) part of the fold is at least 3 mm/yr. Investigations of the tectonic geomorphology of Wheeler Ridge support the hypothesis that climatic perturbations are primarily responsible for producing geomorphic surfaces such as alluvial fan segments and river terraces—tectonic perturbations deform the surfaces.

Loess stratigraphy of the Lower Mississippi Valley

Loesses of the Lower Mississippi Valley (LMV) are world-famous. Sir Charles Lyell (1847), Hilgard (1860), Stafford (1869), Call (1891) and Mabry (1898), thought the LMV loess was a single water deposit although “double submergence” was noted by Call (1891) and Salisbury (1891). Shimek (1902) and Emerson (1918) recognized LMV loess as a wind deposit which came from the valley. Although wind-deposited loess gained wide acceptance, Russell (1944a) published his controversial theory of “loessification” which entailed weathering of backswamp deposits, downslope movement and recharge by carbonates to form loess. Wascher et al. (1947) identified three LMV loesses, mapped distributions and strongly supported eolian deposition. Leighton and Willman (1950), identified four loesses and supported eolian deposition as did Krinitzsky and Turnbull (1967) and Snowden and Priddy (1968), but Krinitzky and Turnbull questioned the deepest loess. Daniels and Young (1968) and Touchet and Daniels (1970) studied the distribution of loesses in south-central Louisiana. West et al. (1980) and Rutledge et al. (1985) studied the source areas and wind directions which deposited the loesses on and adjoining Crowley's Ridge. B.J. Miller and co-workers (Miller et al., 1985, 1986, Miller and Alford, 1985) proposed that the Loveland Silt was Early Wisconsin rather than Illinoian age and advanced the name Sicily Island loess. They proposed the underlying loess was Illinoian and advanced the name Crowley's Ridge. We termed the loesses, from the surface downward, Peoria Loess, Roxana Silt, Loveland/Sicily Island loess, Crowley's Ridge Loess and Marianna loess. Researchers agree that the surfical Peoria Loess is Late Wisconsin and the Roxana Silt is Late to Middle Wisconsin, but little agreement exists on the age of the older loesses. Pye and Johnson (1988) proposed Early Wisconsin for the Loveland/Sicily Island. McKay and Follmer (1985) suggested this loess correlated with a loess under Illinoian till. Clark et al. (1989) agreed on Crowley's Ridge, but suggested the Loveland/Sicily Island loess on Sicily Island was older. Mirecki and Miller (1994) and Millard and Maat (1994) suggested an Illinoian age for the Loveland/Sicily Island loess. Miller and co-workers suggested, as did Pye and Johnson (1988), an Illinoian age for the Crowley's Ridge loess. McKay and Follmer (1985) suggested it correlated with a loess under “Kansan” till. Stratigraphy indicates the Marianna is the older of the five loesses. Researchers identified loess on both the east and west side of the LMV as well as on higher terraces within the valley. Many researchers assumed unaltered loesses were commonly yellowish brown, and silts or silt loams (West et al., 1980; Miller et al., 1986). The nonclay fraction of unweathered LMV loesses was dominated by quartz followed * Corresponding author. by carbonates, mainly dolomites, followed by feldspars, and micas. Clays were dominated by montmorillonite followed by micaceous minerals, kaolinite and vermiculite (Miller et al., 1986). Soils in the Crowley's Ridge loess are most developed, followed by the soils in the Loveland/Sicily Island which are more developed than the modern soils in the Peoria Loess. Soils in the Roxana and Marianna loesses are least developed and the Farmdale Soil of the Roxana is the weaker of the two (Miller et al., 1986). There is certainly overlapping range in the degree of soil development in the various loesses.

Soils as a tool for estimating ages of Quaternary fault scarps in a hyperarid environment — the southern Arava valley, the Dead Sea Rift, Israel

On the alluvial fan of Nahal Shehoret in the extremely arid region of the Negev desert, Israel, Reg soils developed on stable alluvial surfaces in colluvium along terrace risers and in colluvial units on a complex fault scarp were compared. The degree of soil profile development provided an age estimate of the surface that was faulted, a maximum age estimate of the scarp or terrace riser, and an estimate of the maximum recurrence intervals of faulting events. IRSL dates of the tectonically displaced alluvial surfaces and colluvial units at the same site enabled us to re-evaluate the use of Reg soils for relative dating. The major faulting event started at 34.8 ± 4.3 ka. It displaced a late Pleistocene surface of the Nahal Shehoret alluvial fan dated at 56 ± 10.8 ka. Renewed fluvial activity and deposition of alluvium on the downfaulted block had almost terminated by 13.6 ± 2.3 ka. The scarp was formed during the latest Pleistocene and was followed by smaller faulting events which had only minor effects on the fault scarp morphology. The similarity of age estimates from IRSL dating and the degree of soil development in this environment indicates that soils can be used to date surfaces and colluvial units.