Rock Coatings

Preface and Acknowledgements. Section 1. General Perspectives. Chapter 1. Introduction. Focus and organization of book. Awareness of rock coatings. Nomenclature. Historical perspective on major research threads. Chapter 2. Paradigms and Methods in Rock Coating Research. Alternative perspectives. Adopting the paradigm of landscape geochemistry. Adjudicating competing hypotheses. Introduction to landscape geochemistry. The development of landscape geochemistry in Soviet geography. Landscape geochemistry outside of Russia/Soviet Union. Fundaments of landscape geochemistry. Rock coatings as a part of the geochemical landscape. Methods used in original data gathering. Field collection. Preparation of polished cross-sections and ultrathin sections. Secondary electron microscopy. Backscattered electron microscopy. X-ray spectrometry. X-ray images. Energy dispersive spectrometry. Wavelength dispersive spectrometry. Detection of organic matter. Admission of bias. Section 2. Different Rock Coatings. Chapter 3. Anthropogenic Pigments. Introduction. Prehistoric rock pigments. Historic rock painting. Coatings to change appearances. Coatings to preserve stone. Coatings to preserve landscape aesthetics. Chapter 4. Lithobiontic Coatings. Introduction. Different types of lithobiontic coatings. Bacteria. Cyanobacteria. Fungi. Algae. Lichens. Higher plants. Controls on distributions. Impact of lithobiontic coatings. On organic remains. On rock weathering. On other rock coatings. Chapter 5. Carbonate Crusts. Introduction. Freshwater deposits. Marine littoral. Pedogenic. Subaerial rock faces. Carbonate crusts and greenhouse warming. Chapter 6. Case Hardening Agents. Introduction. Characteristics. Environmental settings. Subaerial desert exposures. Subsurface origins. Associated with carved rock. Tropics. Temperate environments. Arctic and Alpine environments. Composition. Material added to weathering rind. Rock coatings as case hardening agents. Fused rock as a case hardening agent. Rates of formation. Origin. Chapter 7. Dust Films. Introduction. Characteristics. Environmental settings. Composition. Rates of formation. Origin. Chapter 8. Heavy Metal Skins. Introduction. Manganese skins. Environmental settings. Composition. Mineralogy. Chemistry. Scavenging of other heavy metals. Rates of formation. Morphology. Origin. Biotic hypotheses. Abiotic hypotheses. Combination of biotic and abiotic formation. Heavy metal skins as a mix of natural and anthropogenic factors. Introduction. Lead-enriched heavy metal skins. Copper and other heavy metal skins. Patina, metal corrosion and rock coatings. Chapter 9. Iron Films. Introduction. Characteristics. Environmental settings. Artifacts. Fractures in rocks. Grain coating on sand. Springs. Streams. Subaerial rock surfaces. Underside of rocks. Iron films interdigitated with other rock coatings. Composition. Mineralogy. Type I iron films. Type II iron films. Type III iron films. Heavy metal scavenging. Information on rates of formation. Origin. Source of the iron. Abiotic genesis. Biotic genesis. General models. Chapter 10. Manganiferous Rock Varnish. Introduction. Characteristics. Environmental settings: desert varnish or rock varnish? Perspectives prior to World War II. Perspectives in the middle years. Notion of an ideal climate of formation. Environmental context. Physical-chemical characteristics. Thickness. Color. Sheen. Mineralogy. Chemistry. Micromorphology. Textures seen in cross-section. Post-depositional modification. Classification of rock varnish. Prior perspectives on classification. Why classify rock varnish? Color/chemistry differences. Geomorphic differences. Microscopic Distinctions. Dangers of misidenification. Dangers of instituting a bad classification. A tiered classification for rock varnish. Rates of formation. Observations prior to World War II. Observations from World War II to the first dissertation. Calculating rates of formation. Origin. Framing the issues historically. Debate prior to World War II. Internal origin. External origin. Biological origin. Polygenetic origin. Debate from World War II to the first dissertation. Internal origin. External origin. Both internal and external. Manganese enhancement by chemical processes. Manganese enhancement by biotic processes. Source of the manganese. New polygenetic model of varnish formation. Clay minerals at the building block level. Managanese enhancement. How rock varnish grows. Chapter 11. Nitrates and Other Uncommon Rock Coatings. Introduction. Phosphate skins. Nitrate crusts. Salt crusts. Sulphate crusts. Why these rock coatings have a limited distribution. Chapter 12. Oxalate-rich Crusts. Introduction. Characteristics. Environmental settings. Composition. Rates of formation. Origin. Chapter 13 Silica Glaze. Introduction. Characteristics. Environmental settings. Silica accumulation in geologic and pedogenic systems. Subaerial surfaces in deserts. Sub-glacial and pro-glacial environments. Hawaiian silica glaze. Silica glazes in temperate environments. Antarctic silica glaze. Silica glaze on artifacts. Silica glaze and rock art. Silica glaze on stone monuments. Streams. Silica glazes interdigitated with other rock coatings. Composition. Type I. Homogeneous amorphous silica glaze. Type II. Detrital-rich silica glaze. Type III. Alumina-iron-rich silica glaze. Type IV. Alumini-rich silica glaze. Type V. Iron-rich silica glaze. Type VI. Alumina glaze. Rates of formation. Origin. Source of the silica. Abiotic genesis. Biotic genesis. General models. Speculation on iron films on Mars. Section 3. Synthesis. Chapter 14. General Model of Rock Coating Development.Introduction. Landscape geochemical hierarchy of controls. First-order processes: geomorphic controls. Exposure of bare rock. Stability of rock surfaces. The role of rock type. Second-order processes: inheritance from a subsurface position. Third-order processes: habitability for lithobionts. Fourth-order processes: transport pathways. Fifth-order processes: biogeochemical barriers. A consideration for the dynamic. The hierarchical model as an interpretive tool. Chapter 15. Analyzing Geographical Variations in Rock Coatings. Introduction. Different approaches to map regional geographical variability. Generalization of micron-scale analyses. Generalization of field observations. Remotely sensed imagery. Case study in regional variability: Himalayan transect. Study areas. Rock coatings in the Khumbu. Rock coatings in Ashikule Basin, West Kunlun mountains. Discussion and conclusion. Asymmetry in rock coatings and landscape aesthetics. Role of rock coatings in the weathering system. Iron films. Silica glaze. Dust films. Carbonate and sulfate crusts. Oxalate-rich crusts. Phosphate skins. Rock varnish. Comparison with rock coatings in other geographic settings. Immplications for understanding geographical variations in rock coatings. Concluding perspectives. References. Geographical index. Subject index.