Cutans

Abstract: 1. Introduction. 2. The Geology and Geomorphology of Antarctica. Geology. Tectonic history. Significance of underlying geology to soil formation. Geomorphology. 3. The Climate of Antarctica. Climatic elements. General climatic regions. Ice-free regions. The climate of the soil. Climatic zones and soil relationships. 4. Biology of Antarctic Soils. Distribution of organisms. The influence of organisms in soil development. Biology of thermally heated ground. 5. Physical Weathering and Rock Disintegration. Physical weathering of rocks. Wind action and rock disintegration. Physical weathering within the regolith. 6. Chemical Weathering. Rock-weathering studies. Clay mineral formation. Calcite and gypsum accumulations. Influence of salts on soil weathering. 7. Soils and Soil Properties. Summary of pedological research. The soil properties. Salt horizons. Soil depth. Frozen ground. Particle-size differences within the profile. Consistence and structure. Cutans. 8. Soil Distribution and Factors Influencing the Soil Pattern. Soil forming factors. Local soil moisture variations and profile development. Parent material differences and soil distribution. The influence of time on soil development. Weathering stages in soil formation. General distribution of weathered soils. Topography and the soil pattern. Microtopography and soil pattern. 9. The Salts in Antarctic Soils. The chemistry of precipitation. Chemistry of saline lakes. Bedded salt deposits of coastal regions. Salt deposits in soils. Origin of the salts. Morphology of salts. Migration of salts. Salts and time. 10. Soil Weathering and Glacial History. Evidence of multiple glaciations. Estimate of absolute age. General outline of Mcmurdo glaciations. Soil weathering stages and glacial chronology. Reconstruction of Antarctic glaciation. 11. Classification of Antarctic Soils. Generalised approaches to Antarctic soil classification. Details classification of Antarctic soils. Alternative approaches to Antarctic soil classification. Similarities with aridic soils. 12. Soils and Environmental Considerations. Soil ecosystems. Climatic sensitivity and soil development. Soil stability and renewal. (Each chapter includes an Introduction and Conclusion). References. Index.

Abstract: ABSTRAcr Clay coats which may be continuous or discontinuous originate from soils as cutans from infiltration of clay in sand and sandstone and authigenically as newly formed or regenerated clay minerals Allogenic cutans and infiltration deposits have a laminar morphology whereas authigenic clay coats commonly have a radial morphology Thick well developed continuous clay coats regardless of origin may retard quartz cementation by masking the surface of detrital quartz grains and preventing the nucleation of quartz overgrowths Chlorite is the most effective of the clay minerals in preserving intergranular porosity and appears to be important in very deep sandstone reservoirs The most favorable amount of chlorite to preserve porosity is variable 4 to 7 volume percent for the Berea Sandstone and 5 to 13 volume percent for the Tuscaloosa Sandstone for example Smaller amounts of chlorite permit quartz to nucleate and destroy porosity and greater amounts result in porosity reduction by infill of pores Clay coats do not retard epitaxial cements e g carbonates and sulfates which may cover clay coats and occlude porosity Clay coats may occur in highly lithic e g 35 lithic material sandstones but are not important because physical com paction dominates diagenesis and destroys porosity Experimental growth of clay coats shows that clay flakes are flatly attached to detrital sand grains and curl upward to form a radial fibrous morphology This attached root zone may explain why clay coats are effective at blocking nucleation of quartz cement Ex perimental work also shows that mineralogy may provide an initial substrate control over the precipitation of clay coats by providing an in situ source of the cations needed to precipitate the clay Later the clay coats nucleate on other framework grains farther from the site of initial nucleation

Abstract: The potential for movement of sewage sludge-borne trace metals beyond the zone of soil incorporation poses a real concern for society. To address this concern, we sampled an Aeric Ochraqualf (Blount Series) after 14 yr of massive, sludge additions (765 Mg ha⁻¹ cumulative sludge applications, dry wt. basis). Cadmium, Zn, and Cu concentrations in each genetic horizon to a depth of 1.0 m were determined by atomic absorption spectroscopic analyses of 4.0 M HNO₃ extracts. In addition, ped surfaces (cutans) and intra-ped material (s-matrix) from prismatic structural units of the lower B and upper C horizons were analyzed to determine the partitioning of trace metals in this highly structured profile. Cadmium concentrations in the subsoil of sludge-treated areas were consistently and significantly higher (∼0.4 mg kg⁻¹) than levels present in the control areas. Similarly, Zn concentrations in the 0.32 to 0.51 m region (Bt1) were increased (∼12 mg kg⁻¹) with sludge applications; no increases in Cu levels were observed. Significantly more Cd (0.08 mg kg⁻¹) was present in cutans removed from ped surfaces in the upper B horizon than was observed in the s-matrix for sludge-treated areas. Cutans also contained more sludge-borne Zn than the associated s-matrix. The evidence suggests that small amounts of sludge-borne Cd and Zn moved out of the tillage zone into the subsoil of this highly structured agricultural soil over a 14-yr period of massive sludge additions. Contribution from USDA-ARS and the Univ. of Minnesota, St. Paul, MN 55108. Scientific Journal Series no. 18 073.