Pedogenic Changes Research Articles

Short-term, post-burial change in a humic rendzina soil, Overton Down Experimental Earthwork, Wiltshire, England

The 1992 excavation of the Overton Down Experimental Earthwork provided a unique opportunity to study pedogenic change in a humic rendzina soil 32 years after burial beneath a chalk bank containing a central stack of turves. Investigations focused on soil structure, porosity, organic matter, plant remains, pH, carbonate, iron, and magnetic susceptibility. Standard methods of chemical analysis and micromorphological description were complemented by quantitative analysis of soil thin sections. The results demonstrate both the speed of change (e.g., compaction and organic decomposition have reduced the thickness of the Ah horizon by >50% in places), and the way the microenvironment of burial can significantly affect the nature and direction of change (e.g., differences in pH, carbonate, soil structure, and earthworm activity between soils buried beneath the chalk rubble and the central turf stack). These have important implications for the preservation of biological and cultural remains, and for the maintenance of their stratigraphic integrity. © 1996 John Wiley & Sons, Inc.

Scanning electron microscope study of zircons and rutiles from a podzol chronosequence at Cooloola, Queensland, Australia

Summary A chronosequence of four soils derived from aeolian deposited sand at Cooloola, along the eastern coast of southern Queensland, has been studied to document predepositional and pedogenic changes in zircon and rutile grains in the fine sand fraction (53–125μm) with increasing soil age. The soils range in age from Holocene (Typic Quartzipsamment — presently drifting sand) to mid Pleistocene (Spodic Quartzipsamment — 90 ka BP). Parent materials are moderately stratified sands with irregular depositional layers, in places having high concentration of heavy mineral grains. Scanning electron microscopy was used to characterize grain surface microtexture by a semi-quantitative method based on frequency of occurrence of ten classes of surface microtextures. Pedogenic changes were quantified and differences between horizons in the same profile, between different profiles within the same horizon, and between minerals were tested for significance using the χ2-distribution. Zircon grains are less chemically weathered during pedogenesis than rutile possibly due to the higher iron content of the latter. However, zircons tend to show more features which can be associated with physical alteration. Rutile grains in the illuviated B2hs horizons of the Troporthod and Spodic Quartzipsamments are more thickly coated with poorly crystalline iron and alumino-silicate compounds compared with zircon grains, and the presence of grain coatings does not seem to have prevented the surfaces of grains from developing solution pits. With increasing age there is a preponderance of “weathering” features on grains of both minerals. The presence of various shapes and surface microtextures on grains from the different soils suggests a multiple grain source for zircon and rutile, and a complex predepositional history for these minerals. Nevertheless, microtextural features of zircons and rutiles are valuable for the interpretation of the extent and nature of post depositional weathering.

Spatial soil variability in the Cajon Pass chronosequence: implications for the use of soils as a geochronological tool

Spatial variation of soil properties on a single geomorphic surface has a significant influence on surface correlations and age determinations made on the basis of soil properties. Few chronosequence studies have been based on a sufficient number of soils to evaluate the influence of soil variability. We described and evaluate 35 soils on four terrace surfaces which constitute part of a previously described, well-dated soil chronosequence in Cajon Pass in southern California. Soils were described on both bar and swale sites, removed from the influence of deposition adjacent slopes. The influence of eolian silt on the rate of pedogenesis in Cajon Pass indicates that this sequence of soils cannot be considered a chronosequence in the strict sense of the term. Furthermore, the evidence for a pedogenic threshold in these soils indicates that the soils do not develop monotonically with time and that soil development cannot be defined by a continuous univariant chronofunction. The discrete nature of the data from a chronosequence and the complex nature of soil development are better analyzed by multivariate statistical procedures. Systematic variation in soil properties between soils from bar sites and soils from swale sites is Attributed to geomorphic processes which affect either the rate or duration of eolian dust accumulation. Soils from bar sites were less variable and generally less strongly developed that soils from swale sites from the same surface. The degree of variation of soil properties determined for a given landscape position on a surface is sufficient to raise questions concerning the usefulness of chronofunctions for determining the nature of time-dependent pedogenic changes and for providing numerical age determinations. Multivariate statistical methods were used to differentiate among soils developed on three surfaces which differ in age by only 1500 years.

Soil/landform relationships surrounding the Harappa archaeological site, Pakistan

AbstractA soil survey around the archaeological site of Harappa, Pakistan revealed alluvial deposits of five distinct ages based on relative position in the landscape and degree of soil profile development. the youngest deposit (age 1) is in the lowest landscape position and has received flood waters as recently as 1988. Soils there are in an incipient stage of development: only organic carbon and soluble salts have accumulated at the surface of the profile. the age 2 deposit has not undergone significant pedogenic change, but is in a slightly higher landscape position than the youngest deposit. Elevated concentrations of P, and the presence of sand‐sized pottery and brick fragments, indicate that this deposit was derived at least partially from archaeological material. the presence of small, soft calcite nodules (Stage II) and some soluble salt translocation are the primary pedogenic changes observed in the age 3 deposit. the age 4 deposit shows evidence of both carbonate and gypsum accumulation. Presence of large gypsum nodules in deep By horizons suggests that a high groundwater table has altered these soils. the oldest deposit, age 5, forms a late Pleistocene stream terrace of the Ravi River. the soil formed in this deposit exhibits considerable carbonate accumulation, with large, dense nodules (Stage II + ) and an argillic horizon. A 14C date from pedogenic calcite gives an age of 7080 ± 90 years B.P., indicating a minimum age of early Holocene. the soil survey suggests that the ancient city of Harappa was built on an age 5 stream terrace remnant, surrounded by Holocene floodplains and a meandering channel of the Ravi River.

Pedogenesis of a chronosequence in the Sacramento Valley, California, U.S.A., II. Elemental chemistry of silt fractions

A chronosequence of six soils from alluvium along Honcut Creek in central California has been analyzed to document pedogenic changes in the fine silt (2–20 μm) and coarse silt (20–50 μm) fractions with increasing soil age. The soils range in age from 600 yr to 1.6 million yr and have been formed in a xeric-thermic soil climate. Parent materials are moderately stratified loams, silt loams, and sandy loams derived from basic metavolcanic and granitic rocks. Parent material uniformity was quantified using particle-size distribution of non-clay fractions and X-ray fluorescence (XRF) elemental analysis of silt fractions. Pedogenic changes were quantified using XRF elemental data and a stable index calculation with Zr as the index element. Parent sediments of four of the six profiles fine upward. Parent elemental composition of the silt fractions was less variable than was texture: for example, clay-free silt/sand ratio changes by a factor of 5 down the horizons of the 600-yr-old soil whereas Ca/Zr ratio in fine silt changes by a factor of only 1.1. Comparison of C and deep BC horizons among soils demonstrate that the parent elemental composition was not constant for all chronosequence members. Silicon, K, Ti and Zr become more abundant and Na, Mg, Al, Ca and Fe less abundant in silt fractions of A and B horizons with increasing soil age due to differential weathering rates of primary minerals. All elements decrease in absolute abundance in silt fractions when Zr is used as a stable index element. About 40–50% of the Ti has been lost from the silt fractions of the 1.6-million-yr-old soil and proportional amounts from younger soils, clearly indicating that Ti is mobile in these soils. Magnesium loss can be detected over the effects of stratification in the 10,000-yr-old soil and Mg-bearing minerals are virtually absent from the silt fractions of the upper 1.5 m of soils that are 130–250,000 yr in age. Calcium, Na and Mg are almost completely weathered from the silts in the upper 4 m of the oldest soil, whereas half to more than three-fourths of K is retained. Age trends of element depletion are systematic for those elements and indices that are not influenced by stratification or change in other soil-forming factors. Age trends of depletion are linear when regressed on the log of soil age and have correlation coefficients ( r) that range from 0.57 to 0.93. A mobility sequence based on the degree of depletion of elements from fine silt of the 130,000- and 250,000-yr-old soils is: Mg ⪢ Na > Ca ≅ Fe > Al > Si > Ti > K > Zr.

Early Stages of Mine Soil Genesis in a Southwest Virginia Spoil Lithosequence

AbstractNatural topsoils in the Appalachian surface mining region are often more difficult to use and less desirable than alternative spoil materials. Parent material effects and initial pedogenic changes over 3 yr were observed in 5 mixes of sandstone (SS) and siltstone (SiS) spoils under grass vegetation. Spoil type controlled initial soil texture, but significant decreases in sand contents and increases in silt contents occurred in several spoil mixes within 2 yr. All mine soils studied were high (≥65%) in coarse fragments. Mine soils derived from spoils high in siltstone content were higher in coarse fragments, pH, extractable cations and iron, fine earth (<2 mm) water holding capacity, and electrical conductivity than sandstone mine soils. Dissolution and leaching, oxidation, and organic matter incorporation were dominant pedogenic processes influencing mine soil properties over the period of this experiment. Distinct surface A horizons formed within 3 yr. Water retention in the <2‐mm fraction increased over time in the surface (0 to 5 cm) of all spoil types except pure sandstone. Extractable Fe and total N increased between 1982 and 1984, while pH, and extractable Ca, Mg and P decreased in most spoil types. These changes reflect rapid pedogenesis in fresh unweathered parent materials in a humid environment.

Quantitative Evaluation of Pedogenic Changes in Boralfs (Gray Luvisols) of East Central Saskatchewan

Soil Science Society of America JournalVolume 50, Issue 4 p. NP-NP ErrataFree Access Quantitative Evaluation of Pedogenic Changes in Boralfs (Gray Luvisols) of East Central Saskatchewan This article corrects the following: Quantitative Evaluation of Pedogenic Changes in Boralfs (Gray Luvisols) of East Central Saskatchewan M. C. D. Santos, R. J. St. Arnaud, D. W. Anderson, Volume 50Issue 4Soil Science Society of America Journal pages: 1013-1019 First Published online: July 1, 1986 M.C.D. Santos, M.C.D. SantosSearch for more papers by this authorR.J. St. Arnaud, R.J. St. ArnaudSearch for more papers by this authorD.W. Anderson, D.W. AndersonSearch for more papers by this author M.C.D. Santos, M.C.D. SantosSearch for more papers by this authorR.J. St. Arnaud, R.J. St. ArnaudSearch for more papers by this authorD.W. Anderson, D.W. AndersonSearch for more papers by this author First published: 01 July 1986 https://doi.org/10.2136/sssaj1986.03615995005000040053xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume50, Issue4July-August 1986Pages NP-NP RelatedInformation

Quantitative Evaluation of Pedogenic Changes in Boralfs (Gray Luvisols) of East Central Saskatchewan

AbstractZirconium oxide/quartz ratios for the soil horizons of three Boralfs (Gray Luvisols) indicated that two of the soils were developed from sufficiently uniform deposits to permit quantitative evaluations of changes resulting from soil formation. A “pedogenic index” based upon total quartz content of horizons allowed the expression, as a percentage, of soil constituents present in relation to original contents in either total horizons or in component soil separates within them. The index, based upon the total quartz content of each horizon, provides values that overcome errors resulting from changes in particle size distribution of quartz such as occurs in Boralfs or other soils where significant physical breakdown of coarse to finer fractions has occurred. The index shows that approximately one‐third of the original sand in the E horizons has been physically weathered to finer sizes, dominantly to coarse silt size, but also down to clay size. Elemental analyses indicate that the Na‐ and K‐bearing minerals are more resistant than the Ca‐ and Mg‐bearing minerals, and that weathering has occurred in all size fractions. As a consequence, Ca and Mg, and to a lesser extent, Na and K, undergo greater net losses from the solum than do Si, Al, and Fe. Redistribution of the latter three elements within the sola is directly associated with the translocation of clay. Physical breakdown and lessivage are the major processes in all three soils, but chemical weathering and leaching losses are also important. Preferential translocation of fine clay (<0.2 µm) and the weathering of coarse clay (2‐0.2 µm) to fine clay size in both E and Bt horizons is substantiated.

USE OF QUARTZ, ZIRCONIUM AND TITANIUM AS INDICES IN PEDOLOGICAL STUDIES

Four soils, two of which had developed from deposits with visible unconformities, served as a basis for evaluating the use of quartz, ZrO2 and TiO2 as resistant indicators in pedological studies. Contents and ratios of these components for individual size fractions, the total non-clay fraction, and the total soil were compared. Values for individual fractions serve to differentiate and characterize underlying geological strata; changes in particle size distribution and clay translocation within solum horizons necessitate the use of the total non-clay fraction for establishing the original uniformity of soil deposits. Both quartz and zirconium are reliable indices upon which to base quantitative evaluation of pedogenic changes when the total > 2 μ fraction is used, providing that original uniformity of the soil deposit has been established. The mobilization of titanium in all fractions during soil weathering limits its usefulness in this regard. Except for the surface layers, in which anomalous zirconium values were obtained, quartz and ZrO2 provided similar values of calculated losses and gains within horizons of the Orthic Gray Luvisol studied. Significant changes in particle size distribution resulting from physical breakdown in the A horizon, as well as clay translocation and formation within the solum, were recorded.