Evaporites
• Gypsum
• Anhydrite (most ancient deposits are this)
• Evaporation sequence
• Playa lakes and sabkhas and salinas
• Problem = thick ancient deposits
Chert
• Microcrystalline quartz, chalcedony, opal
• Textures - granular, chalcedony, megaquartz
• Varieties - flint, jasper, novaculite
• Bedded chert - siliceous oozes
• Nodular chert - replacement of limestone
– Source of silica, process?????