GEOL 2530 Lecture 6: 6 Other Sed Rocks handout

• School: University of Manitoba
• Department: Geological Sciences
• Course: GEOL 2530
• Professor: Chow Nancy

Document Summary

Thick units of same evaporite concentration by evaporation. Variable water chemistry diverse mineral suites carbonates gypsum dependent on brine inflow chemistry . 6. 1. 3 types of evaporite accumulations: nodular anhydrite-gypsum e. g. chicken-wire structure enterolithic structure gypsum rosettes. Origin: laminated evaporites & carbonates, crystalline crusts e. g. chevron halite swallow-tailed twin gypsum. 6. 2. 1 petrography: microquartz, megaquartz, chalcedonic quartz, siliceous tests. Primary deposits thin beds with shale partings sedimentary structures. Predominantly siliceous tests altered by dissolution & recrystallization siliceous tests - opal-a (metastable) opal-ct (cristobalite, tridymite) - lepispheres quartz. Commonly lack internal structures silicified fossils, relict structures. Thick sequences, up to 50-600 m thick: distinctive thin bedding or laminations (bif) Fe minerals interbedded with chert: granular (reworked) Thin sequences, up to few 10s m thick. Oxidizing atmosphere - problem of transport mechanism: subaerial weathering supplying ferric hydroxide/oxide. Low o2, high co2 atmosphere - problem with oxidation of fe. 6. 5. 1 types of om: soil humus, peat. Type of om: coal, oil shale, petroleum, solid bitumen.