YR Hues Research Articles

Characterization and Evaluation of Cotton-growing Soils of Ghatanji Tehsil, District Yavatmal, Maharashtra

The present investigation was carried out in the Ghatanji tehsil of Yavatmal district, Maharashtra to characterize and evaluate the soil suitability for the cotton crop. Soil resource inventory at 1:10,000 scale was undertaken to establish the soil-landform relationship. Five soil series were identified with the phases on nine landform units. These calcareous clayey soils were shallow to deep (33 to 140 cm) and had their colour in 10YR hue with value 3 to 4 and chroma 1 to 6. The soils were neutral to moderately alkaline with electrical conductivity ranging from 0.11 to 1.35 dSm-1 and had, very low to medium in organic carbon content (0.11 to 0.95%) The surface horizon of all the soils had medium sub-angular blocky structures but sub-surface horizons had medium to coarse and moderate to strong sub-angular to angular blocky structure. The saturated hydraulic conductivity (SHC) of the soils varied from 0.0 to 6.52 cm hr-1. The available water content ranged from 4.60 per cent to 22.2 per cent in the surface horizon and increased with depth. The COLE valuer anged from 0.09 to 0.21 cm. Calcium was the dominant cation on the exchange complex followed by magnesium, sodium and potassium. Taxonomically these soils were classified as Leptic Haplusterts, Sodic Haplusterts, Lithic Haplustepts and Typic Haplustepts at the subgroup level. Parametric land evaluation techniques (Sys & Riquier’s) indicated marginally suitable to not suitable (Sys criteria) and good to poor (Riquier Index) for growing the cottn crop in Ghatanji tehsil of Yavatmal district.

Cordão Formation: loess deposits in the southern coastal plain of the state of Rio Grande do Sul, Brazil.

Loess consists of silt-dominated sediments that cover ~10% of the Earth's surface. In southern South America it occurs in Argentina, Bolivia, Paraguay and Uruguay, and its presence in southern Brazil was never studied in detail. Here is proposed a new lithostratigraphic unit, Cordão Formation, consisting of loess deposits in the southern Brazilian coastal plain. It consists of fine-very fine silt with subordinate sand and clay, found mostly in lowland areas between Pleistocene coastal barriers. These sediments are pale-colored (10YR hue) and forms ~1,5-2,0 meter-thick stable vertical walls. The clay minerals include illite, smectite, interstratified illite/smectite and kaolinite, the coarser fraction is mostly quartz and plagioclase. Caliche and iron-manganese nodules are also present. The only fossils found so far are rodent teeth and a tooth of a camelid (Hemiauchenia paradoxa). Luminescence ages indicate that this loess was deposited in the latest Pleistocene, between ~30 and 10 kyrs ago, and its upper portion was modified by erosion and accumulation of clay and organic matter in the Holocene. The estimated accumulation rate was ~630 g/m2/year. The probable source of this loess is the Pampean Aeolian System of Argentina and it would have been deposited by the increased aeolian processes of the last glacial.

국내 5성급호텔 실내공간의 색채 및 색채이미지 분석 연구

The objective of this study is to examine difference in spatial color planning of lobby, restaurant, and guest rooms of domestic hotels, and analyze spatial color images to provide information on color planning for hotels that are newly built or remodeled. For this purpose, we surveyed 88 five-star hotels in Korea, collected images of their lobbies, restaurants, and guest rooms, and identified dominant colors, secondary colors, and accent colors. Based on this, we analyzed color distribution of hotel spaces, identified their color image scales according to distribution of hue and tone, and analyzed statistical significance in spatial color distributions and color images. The results are as follow. First, regarding color distribution, both dominant colors and secondary colors showed a similar pattern of distribution for all examined areas of lobby, restaurant, and guest rooms. Specifically, dominant colors were biased toward YR Y hues and pale tones, and secondary colors toward YR hues and dark tones. Meanwhile, accent colors varied by hotel areas: GY hues and dark tones were used in the lobby, YR hues and dark tones in restaurants, and Y hues and pale tones in guest rooms. Second, spatial color planning varied at a statistically significant level. In the lobby, Y hues, YR hues, and GY hues were used as dominant color, secondary color, and accent color, respectively. And dominant color was brighter than secondary or accent color, and secondary color and accent color had a higher chroma compared to dominant color. In the restaurant, YR hues were used as both dominant and secondary colors, R colors were used as accent color, and dominant color and accent color were brighter than secondary color. In the guest rooms, Y hues, YR hues, and R hues were used as dominant color, secondary color, and accent color, respectively. And dominant color was brighter than secondary or accent color, and secondary color and accent color had a higher chroma compared to dominant color. Third, as for spatial color image scales of the hotels, elegant and natural images were dominant in all examined areas of lobby, restaurant, and guest rooms. Modern images dominated the lobby and restaurant, and modest images dominated guest rooms. Fourth, statistically significant difference was observed in spatial color image scales of the hotels. Particularly, in the restaurant, modest and subtle images were relatively less common than in other areas, and guest rooms had relatively more modest, splendid or subtle images and relatively less natural and modern images compared to other areas. Fifth, most color image scales were distributed in a hard-static or a soft-static area. From these findings, we extracted a color palette for different hotel areas.

Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Burning is a common practice in tropical areas and related changes in mineralogy might affect the chemical and physical behavior of soils. Maghemite is a common iron oxide in soils formed from basic rocks in tropical regions. This mineral and hematite are the main pigments in these soils and exhibit high magnetization stemming from the precursor magnetite formed during the weathering process of primary minerals. The objective of the present study was to analyze changes in color, magnetic suceptibility values, Fourier transform infrared spectroscopy (FTIR) spectra, and available Fe and Al contents extracted with 1 mol L-1 KCl during the process of thermal transformation of synthetic Al-maghemites into Al-hematites. Synthetic substituted maghemites with different degrees of Al-substitution (0.0, 1.0, 2.0, 2.9, 3.8, 5.6, 6.7, 10.0, 12.0, and 17.1 mol% Al) were subjected to a temperature of 500 ± 10 °C for 0, 5, 10, 16, 64, 128, 192, 360, 720, 2160, 3600, 5040 and 6480 min. The color of the samples was analyzed by a Munsell system in a colorimeter. Mass-specific magnetic susceptibility (χLF) was measured at low-frequency. Available Fe and Al contents were estimated by a 1 mol L-1 KCl solution. Fourier transform infrared spectroscopy (FTIR) spectra were obtained through use of a Bruker Vertex 70X FTIR spectrophotometer at a spectral resolution of 4 cm-1. Contents of Fe and Al extracted by 1 mol L-1 KCl in Al-hematites were not detected. All samples analyzed exhibited YR hue. Hue proportion decreased with increased heating time, and color changed from brown to red. The increase in isomorphic substitution (IS) led to increased hue values from maghemite to hematite, and the latter then became yellower. The χLF values decreased with an increase in heating time, indicating transformation from a ferrimagnetic phase (maghemite) to an antiferrimagnetic phase (hematite). With increasing IS, the maghemite χLF values decreased. Bands of the initial members (time 0) in the FTIR spectra were indexed as maghemites. The end members after completion of the heat treatment were identified as hematites. The IS of Fe by Al in maghemite influenced the thermal transformation to hematite, as well as the color and χLF of the minerals. The χLF proved to be very efficient in detecting maghemites remaining after thermal processing. Fe and/or Al were not ejected from the hematite crystalline structure after heat treatment.

Berino Paleosol, Late Pleistocene Argillic Soil Development on the Mescalero Sand Sheet in New Mexico

The Berino paleosol is the first record of a directly dated Aridisol in the American Southwest where paleoclimatic conditions during the time of pedogenesis can be estimated. The noncalcic, argillic paleosol formed in eolian sand during the cool, wet climate of the mid- and late Wisconsin, marine isotope stages 3 and 2, in presently semiarid southeastern New Mexico. Optically stimulated luminescence dating of the Mescalero sand sheet and the Berino indicates that soil formation occurred during the period 50–18 ka. The paleosol is a red 2.5YR hue Bt horizon, 120 cm thick, with 25% clay, 0.36% Fe, and an absence of visible carbonate. It is buried by younger eolian sand, although at the edges of the sand sheet, it is unburied and a relict soil. Red argillic paleosols in other sand sheets in the region may correlate with the Berino. The Berino paleosol is formally named as a pedostratigraphic unit.

Mineralogy and morphological properties of buried polygenetic paleosols formed in late quaternary sediments on upland landscapes of the central plains, USA

East central Kansas is largely comprised of alternating, level beds of Permian shale and limestone of the Central Plains, USA. Polygenetic upland soils of east central Kansas have been formed though multiple and likely different sets of soil forming factors. Upland soils in this region have a complex genesis, often contain one or more paleosols, and form in multiple parent materials including loess, locally reworked loess or colluvium, and residuum. The depth to bedrock rarely exceeds 2 m. Upland hillslope soils commonly contain one or more paleosols, and can be observed on a variety of hillslope positions on the landscape. Generally, the lower paleosols are recognized by strongly expressed structure, thick continuous clay coatings on all faces of peds, and strong reddish color with either 7.5YR or 5YR hues. Soil textures of the paleosols often feel less clayey than the overlying horizons in field determinations. At first, this was attributed to a decrease in clay content, stickiness, and plasticity. However, subsequent laboratory characterization revealed that the clay content was usually highest in the lower paleosol horizons, and that the clay mineralogy of the modern soil was dominated by smectite, while the paleosols contained a mixed suite of minerals. Therefore, the perceived decrease in clay content was caused by a change in clay mineralogy, a feature that can be exploited in future field descriptions in order to more accurately distinguish between stratigraphic units in these thin, welded polygenetic soils. The age of the paleosols sampled in this study were typical for the late Quaternary-aged Severance formation, clustering in two age ranges, which were ≈ 19,000 to 20,000 and ≈ 22,500 to 27,700 uncalibrated 14C yr BP. The results from this study illustrate that although they might be thin, truncated, and welded, late Quaternary-aged loess-derived soils and paleosols occur in regular, predictable patterns on many upland hillslopes in the Bluestem Hills Major Land Resource Area, and this region should be included in future regional investigations of the Central Plains.

景観色彩における配色パターン分析に関する研究 : ヨーロッパの伝統的な街区を対象として

This study is an investigative research to grasp the continuous structure of color order of the town scenes. The field survey was done on 15 traditional town districts of Europe mostly in Germany. Investigation data was analyzed by the degree of harmony of a keynote color using the standard color chart of MUNSELL with the continuous photograph of the town scenes and has organized the feature of a color scheme in pattern. As a result, a feature of color scheme was clarified by analyzing the relation of a keynote color on a continuous scene; the tendencies are concentrated on the YR hue system with high value and low chroma. Furthermore, the feature of harmony of color scheme and elements of continuous color structure became clear through the result of analysis.

Seasonal factors controlling mineral precipitation in the acid mine drainage at Donghae coal mine, Korea

Monitoring over a 12 month period in the Sanae creek flow in acid mine drainage, Donghae coal mine area, demonstrates that the concentrations of dissolved metals and sulphate are highest during autumn when water flow in the creek is at its lowest. The highest pH values of the stream were measured in April and May, whereas the lowest pH was recorded in October. The Fe concentration of stream water rapidly decreased downstream due to the precipitation of Fe oxyhydroxide and/or oxyhydroxysulfate phases in the stream. Mineral precipitates in the creek in the Donghae mine area show various colours such as brownish yellow (Munsell colour 9.5 YR hues), reddish brown (Munsell colour 3.5 YR hues) and white depending on seasons and distance from the pollution source in the creek. Such phenomena are attributed to the variation in pH and chemical composition of stream water caused by seasonal factors. The measured pH ranges in stream water of the brownish yellow, white and reddish brown precipitates are pH 3.2–4.5, 4.5–6.0 and 5.3–6.9, respectively.

Gallionella Ferruginea in ochreous precipitates from acid mine drainage in Donghae coal mine area, Korea

The morphology ofGallionella ferruginea and other microorganisms in the ochreous precipitates in acid mine drainage (AMD) were investigated using a scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS). Mineralogy of the precipitate containing the microorganism was characterized by X-ray diffraction analysis. TheGallionella ferruginea having twisted structure are found from precipitate samples on the stream bottom in AMD. Other microorganisms, characterized by coccus, bacillus, rod or cylindrical forms, are also observed in the precipitates. The ochreous preciptate was appeared reddish brown color (Munsell color 3.5YR hues) and consisted mainly of ferrihydrite with minor geothite.

Environmental, mineralogical, and genetic characterization of ochreous and white precipitates from acid mine drainages in Taebaeg, Korea.

X-ray diffraction, energy-dispersive X-ray fluorescence, thermal analysis, scanning electron microscopy, inductively coupled plasma emission spectroscopy, and ion chromatography were used for the environmental, mineralogical, and genetic characterization of brownish yellow, reddish brown, and white precipitates from acid mine drainage in Taebaeg, Korea. Ferrihydrite+goethite, schwertmannite, and Al-sulfate were precipitated under different chemical environments on the stream bottom of acid mine drainages. The brownish yellow precipitates (Munsell color 9.5YR hues) consist mainly of schwertmannite with traces of quartz, illite, pyrophyllite, goethite, lepidocrocite, and gypsum. The reddish brown precipitates (Munsell color 3.5YR hues) consist mainly of ferrihydrite with small amount of goethite. The white precipitates consist mainly of poorly crystalline Al-sulfate with small amounts of quartz, gypsum, and calcite. Thermal decomposition due to dehydration of ferrihydrite and schwertmannite takes place at approximately 120 degrees C and 140 degrees C, respectively. Al-sulfate converts to gamma-alumina at 850 degrees C. SEM study shows that the spheroid and rod-shaped precipitates characteristic of Gallionella consist of iron hydroxide with varying chemical compositions.

LATE PLEISTOCENE ICE-FLOW DIRECTIONS AND THE AGE OF GLACIAL LANDSCAPES IN NORTHERN LOWER MICHIGAN

Lineation (alignment) of certain landscape features, most of which are glacigenic, and till-fabric data were mapped and used to indicate glacier flow directions in northern lower Michigan. I also reexamine the limit of the Greatlakean (ca. 11,850 14C yr B.P.) ice advance in northern Michigan. My study assumes that reddish-brown (7.5YR and redder) till in the region was deposited by the last ice advance, the Greatlakean, since this color till covers uplands immediately down ice from an established Greatlakean stratigraphic marker bed. Landscape linearity and till-fabric data within the reddish-brown till landscapes of northwestern lower Michigan both show strong northwest-southeast alignment, indicating that Greatlakean ice advanced out of the Lake Michigan basin. Earlier (Port Huron, ca. 13,000 14C yr B.P.) ice deposited brown till of 10YR hue, as evidenced at a borrow pit where reddish-brown Greatlakean till overlies brown drift. Thus, the “7.5YR and redder” vs 10YR hue limit is interpreted as the outer limit of the Greatlakean advance in northern lower Michigan. By mapping this limit only a few tens of km southeast of its only stratigraphically confirmed position at the Cheboygan bryophyte bed, I imply that Greatlakean ice did not advance as far into northeastern lower Michigan as others previously have suggested. Port Huron landforms in brown till show similar alignment and till fabrics to Greatlakean landforms in red till, suggesting that Port Huron ice in northern Michigan (also) advanced primarily out of the Lake Michigan basin. As it advanced from the northwest, flowlines and till fabrics suggest that the Port Huron ice gradually curved, eventually flowing north-to-south in northeastern lower Michigan, nearer the Saginaw Lobe. [Key words: glacial geology, drumlins, landscape fabric, Greatlakean advance, Port Huron advance, till fabric, glacial dynamics.]

Red soils of different origins from southwest Nigeria: Characteristics, classification, and management considerations

Representative profiles of the Owena, Egbeda, Alagba, and Balogun series were studied. The Owena soil is formed in amphibolite whereas Egbeda and Balogun soils are formed in biotite gneiss derived parent materials. The Alagba soil is formed in sandstone parent rock. The main objectives were to characterize the soils and their clay fraction, and to classify and interpret soil properties for agricultural land use. Most soils exhibit 2.5 YR hues in subsurface horizons. A pedon formed in biotite gneiss has the highest dithionite Fe content and Fed/clay ratio. The relationships between clay content and Fed values vary according to parent material origin and, therefore, would have to be interpreted differently for soil weathering processes. Clay coatings were noticeable in some soil horizons of all pedons studied. Soils are generally medium to slightly acid with sandstone-derived soils being the most acid. The clay mineral suite in all soils is dominated by kaolinite with traces of 2:1 and 2:2 clay minerals, goethite, hematite, anatase, maghemite, and rutile. In addition, some soils contain trace amounts of gibbsite. Kandic horizons have been identified in all soils. The low charge properties of the soils reflect the intensely weathered clay mineral suite. The base status is probably influenced by the cropping system and therefore may tend to unnecessarily differentiate highly weathered soils at the order level. The Egbeda and Balogun series were classified as Rhodic Kandiudults, clayey-skeletal, oxidic and Rhodic Kandiudalfs, clayey-skeletal, oxidic, respectively. Others, Owena, and Alagba series, were classified as Typic Kanhaplohumults, clayey, oxidic and Rhodic Kanhaplustults, fine loamy or clayey, oxidic, respectively. In the FAO-Unesco legend, all soils become Rhodic Ferralsols. In addition, the Owena (with its nitic properties) is further classified as niti-rhodic Ferralsol. The two classification systems are at variance for highly weathered (variable charge property) soils and this difference will definitely influence management decisions depending on which system is used at any particular time. Soil attributes favorable for agricultural use include thick sola and favorable structures. Chemical properties suggest minimal fixation of phosphorus. Key words: Dithionite Fe, kandic, oxidic, variable charge, ferralic, exchangeable Al

Soil chronosequence of brasstown creek, Blue Ridge mountains, USA

A chronosequence of soils on alluvial terraces in the Appalachian highlands of the southeastern United States is identified by simple methods of quantitative soil morphology and chemical analysis. The chronosequence is from Brasstown Creek, a 5th order stream draining 65 km 2 of the Blue Ridge Mountains of north Georgia. The portion of the valley studied is about 1 km wide and contains five Quaternary terrace remnants. Radiocarbon dates show that the floodplain (T0) is late Holocene and includes historical (post ca. 1830 A.D.) sediment, and the four older terraces (T1–T5) are pre-Holocene. The floodplain soils are either Entisols in historical sediment or buried Inceptisols with weak Bw horizons in late Holocene to protohistoric sediment. The lowest terrace (T1) is terminal Pleistocene in age, and its soils have Bt horizons that are about 0.9 m thick, 10YR 4/5 to 10YR 5/4 in colour, and contain 25 to 35% clay. Soils on terraces older than T1 become progressively redder and contain more clay with increasing age, culminating with 2.5YR hues and 40 to 52% clay in the Bt horizon of T5. Percent clay in Bt horizons, rubification indices, iron oxide contents, and element ratios progressively change with age of the terraces, but other morphological properties, pH, and individual element concentrations are of less use as chronosequence variables.

Pedogenesis of a Vernal Pool Entisol‐Alfisol‐Vertisol Catena in Southern California

AbstractVernal pools are seasonal wetlands that have unique plant and animal species. More than 10 vernal pools are found on the basaltcapped mesas of the Santa Rosa Plateau Ecological Preserve in southern Riverside County, California. In this study, one vernal pool catena was investigated to determine the relationships between soil morphology, soil chemical properties, and water movement. Soils on the summit and backslope are shallow and coarse‐loamy, and are maintained as Entisols by extensive burrowing by rodents and their predators. Footslope soils are clayey Alfisols with strong prismatic structure. The basin and toeslope soils are Vertisols with strong angular blocky structure and slickensides. Iron oxides are concentrated in the upper slope soils, imparting 5YR hues and high chromas. Because Mn oxides are soluble at higher redox potential than Fe oxides, Mn has been preferentially dissolved, transported downslope with throughflow, and precipitated as oxides in the lower slope soils, which have 10YR hues and low chromas. Water infiltrates readily through the upper slope soils and moves downslope along the soil‐basalt bedrock contact and within the vesicular basalt. In the basin, the Vertisols are wetted unevenly as water moves downward through soil cracks and upward from throughflow in the underlying vesicular basalt.

Stratigraphy and genesis of Durorthids and Haplargids on dissected alluvial fans, western Mojave Desert, California

Presumed slow weathering rates in arid-region soils have given rise to the hypotheses that (1) the major carbonate source in most Aridisols is from eolian deposition, and (2) soil horizons cemented by carbonates and opaline silica are indicators of geomorphic surfaces of mid-Pleistocene age. To test these hypotheses we studied the stratigraphy and genesis of four soils, a Typic Durorthid (Alko series), two Typic Haplargids (Neuralia and Garlock series) and a Typic Torripsamment (Cajon series), found in close association on a dissected alluvial fan in the western Mojave Desert. The study area has a rolling topography with the calcareous Alko soil occurring on narrow summits and on the edges of broad summits, Neuralia (calcareous) on broad summits and on sideslopes, Garlock (noncalcareous) on sideslopes, and Cajon in the drainage ways. Soil stratigraphy in an excavated trench indicates that these soils are forming on deposits of differing ages. Paleomagnetic data indicate that at least four aggradational events have occurred in the past 783 ka (thousand years). The sequence of alluvial units in the area is similar to other sequences observed in the Mojave Desert and eastern San Joaquin Valley. The Garlock soil, with 5YR hues and a distinct carbonate-free argillic horizon, occurs on an older geomorphic surface, but younger deposit, than the Alko and Neuralia soils. Rodents are active in the profiles of Alko and Neuralia soils. Bioturbation of the upper soil mantle brings calcareous soil and duripan fragments to the surface, thus creating a pedogenically rejuvenated geomorphic surface on which profile development has been retarded. The occurrence of calcareous Haplargids adjacent to Haplargids that are noncalcareous to a depth of 65 cm, indicates that the atmospheric input of CaCO 3 in the study area has been minimal during the Holocene. The rate of CaCO 3 accumulation in soils of the study area is estimated to be 0.03 to 0.05 g cm −2 1000 yr −1 over the past 200 ka. A rate of accumulation of 0.27 g cm −2 1000 yr −1 is required to form the 2-cm-thick laminar cap of the upper Alko duripan during the Holocene. This amount could easily be added to the surface by bioturbation from calcareous duripan fragments in the profile. Thus, much of the laminar part of the duripan is probably a Holocene phenomenon.

Soils and landscape evolution of eolian plains: the Southern High Plains of Texas and New Mexico

Sheets of eolian sediment cover many areas of the earth's surface, sand seas, dune fields, and loess sheets being the best known examples of such features. Less well known are deposits of sandy, eolian sediment forming extensive plains. An excellent example of such a region is the semi-arid Southern High Plains (northwest Texas and eastern New Mexico). The level landscape of the area was created by deposition of multiple, extensive (≈ 80,000 km 2 ) sheets of eolian sediment (Blackwater Draw Formation) over the past 1.4+ Ma. This deposit grades from sandy (southwest) to silty and clayey (northeast) and is up to 27 m thick. Surface soils (at least 30,000 and possibly 120,000 years old) are well developed (5YR hues, agrillic horizons, 1–2m thick with prismatic structure, Stage II–III calcic horizons) and are generally Paleustolls and Paleustalfs, with some Paleargids and Haplargids. Morphologic variation is due mainly to textural variation of the eolian parent material, although locally thickness of the parent material and wind erosion and cumulization are important factors, and locally slight variation in effective precipitation may be significant. The Blackwater Draw Formation contains as many as six well-developed buried soils, each formed in individual layers of eolian sediment, similar to or more strongly expressed (2.5YR hues, higher illuvial clay content) than the regional surface soils. The presence of the buried soils indicates that sedimentation was episodic and separated by long periods of relative landscape stability. Eolian processes also appear to have been important during the periods of stability and pedoenesis by providing clayey, calcareous dust that was added to the soil, promoting formation of the argillic and calcic horizons. The sedimentologic and pedologic uniformity of the deposit suggests that the regional environment has not varied significantly during the Quaternary except for periods of increased sedimentation or wind deflation. Underlying the Blackwater Draw Formation is an Upper Tertiary deposit (up to 36 m thick) of eolian sand, silt, and clay (Ogallala Formation). This deposit contains buried soils very similar to those in the Blackwater Draw Formation, suggesting that the geomorphic processes that created the Quaternary landscape of the Southern High Plains began to operate in the late Tertiary, perhaps as much as 11 million years ago.

The Blackwater Draw Formation (Quaternary): A 1-4-plus-m.y. record of eolian sedimentation and soil formation on the Southern High Plains

The Southern High Plains of northwestern Texas and eastern New Mexico are mantled by a vast (>100,000 km 2 ) sheet of Quaternary eolian sediment locally as much as 27 m thick and termed the Blackwater Draw Formation. These sediments generally fine from southwest to northeast, exhibiting a linear relationship of decreasing sand content and sand size and increasing silt content with increasing distance, indicating the source area to be the Pecos River valley. As many as six well-developed buried soils (2.5YR to 5YR hues, Bt horizons 1-2 m thick, Stage II-III calcic horizons), similar to the regional Paleustalf and Paleustoll surface soils, occur in the formation. The buried soils indicate episodic sedimentation separated by long periods of landscape stability. Eolian sedimentation probably occurred during prolonged aridity, and stability and pedogenesis likely obtained during subhumid to semiarid conditions, similar to those of the late Quaternary. The presence of the 0.62-m.y. Lava Creek B Ash and the 1.4-m.y. Guaje Ash in the formation shows that the deposit accumulated throughout most of the Quaternary. Data from paleomagnetic, thermoluminescence, and radiocarbon studies suggest that each cycle of sedimentation-stability lasted for several hundred thousand years and that the last depositional event occurred at least several tens of thousands of years ago.

Weathering of Iron-Bearing Minerals in Soils and Saprolite on the North Carolina Blue Ridge Front: II. Clay Mineralogy

AbstractThe mineralogy of the clay fraction was studied for soils and saprolite on two Blue Ridge Front mountain slopes. The clay fraction contained the weathering products of primary minerals in the mica gneiss and schist parent rocks. Gibbsite is most abundant in the saprolite and residual soil horizons, where only chemical weathering has been operable. In colluvial soil horizons, where both physical and chemical weathering have occurred, the clay fraction consists largely of comminuted primary phyllosilicates —muscovite, chlorite, and possibly biotite—and their weathering products: vermiculite, interstratified biotite/vermiculite (B/V), and kaolinite. The clay-size chlorite contains Fe2+ as indicated by Mössbauer spectroscopy, and is more resistant to weathering than biotite. The vermiculite and B/V, both weathering products of biotite, contain Fe3+. Vermiculite in colluvial soils and, especially, surface horizons is weakly hydroxy-interlayered. The kaolinite in the clay fraction resulted at least partly from the comminution of kaolinized biotite in coarser fractions.The hematite content ranged from 0 to 8% of the clay fraction and strongly correlates (r =.95) with dry clay redness, as measured by the redness rating: RR = (10 - YR hue) × (chroma) ÷ (value). The hematite is largely a product of the weathering of almandine; thus, the soil redness is dependent on the amount of almandine in the parent materials and its degree of weathering in the soils. Goethite (13–22% of the clay fraction) imparts a yellow-brown hue to soils derived from almandine-free parent rocks. The release of Fe in relatively low concentrations during the weathering of Fe-bearing primary minerals, particularly biotite, appears to have promoted the formation of goethite.

Variations in Surface‐Layer Color, Texture, pH, and Phosphorus Content Across Prairie Dog Mounds

AbstractSpatial variations of soil surface color, texture, pH, and phosphorus content were studied so the effects of relict and modern prairie dog (Cynomys ludovicianus) pedoturbation on soil surface properties will be more predictable in southwestern South Dakota. When first formed, prairie dog mounds are made of surface soil. In time, lower‐layer materials are added to the surface. The overall textural variation usually increases with pedoturbation because the original surface layer has a different texture than the subsoil. The mound pH is usually greater than the adjacent soil because calcareous subsoil is deposited in the mound. With time, the mound pH decreases as carbonate leaches and the color becomes darker as organic matter accumulates. The color hue gradually changes to a 10YR if the subsoil was not originally a 10YR hue. Fecal and skeletal phosphorus are deposited in and on the mound to increase areal variation in phosphorus content as a mound continues to be used.

COLLUVIAL SOIL PARENT MATERIAL RELATIONSHIPS IN THE RIDGE AND VALLEY PHYSIOGRAPHIC PROVINCE OF PENNSYLVANIA1

We studied seven soil pedons developed in colluvium and located at the base of four primary ridges in Pennsylvania. In these footslope positions much of the colluvium consists of an upper brown layer (UBn layer) overlying a buried red layer (Rd layer). Landforms present at the study areas indicate that the UBn layer accumulated as stone-banked solifluction lobes or benches that flowed over the Rd layer during a periglacial environment. The UBn layer has 10YR to 7.5YR hues, is generally 1 to 3 m thick, and can be separated into sublayers. The Rd layer has mostly 5YR hues and is 1 to 2+ m thick. The color of the Rd layer is related to weathering rather than lithology. Beneath the colluvium is a thin lower brown layer (LBn layer) of residuum over bedrock. These layers represent a distinctive parent material sequence for recent soil development. Recognizing the nature of this sequence leads to a better understanding of pedogenesis of these soils. Color, texture, and the distribution of rock fragments with depth reflect variations in the parent material. The lateral continuity of the layers allows proposal of a parent material stratigraphy for colluvium in these foot-slope positions in the Ridge and Valley Physiographic Province.