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24 Cards in this Set
- Front
- Back
Mudstones |
1. most abundant sedimentary rocks
2. pelites, lutites, argalliceous sed. rocks |
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Siltstones
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50% silt
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Claytones
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more than 50% clay
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Mudstone
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silt and clay
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Shale
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laminated or bedded mudstone
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Texture
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1. Silt generally more common than clay
2. Generally not rounded - Difficult to round quartz silt - Platy because of cleavage *Micas *Clay minerals |
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Composition
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1. Clay and mica minerals
2. Quartz 3. Feldspars 4. Identified by x-ray refraction (XRD) |
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Clay minerals (Hydrous Aluminious silicates)
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1. Kaolinite
2. Smectite 3. Chlorite 4. Illite |
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Clay mineral building blocks: Tetrahedron
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Silica tetrahedron in a layer structure
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Clay mineral building blocks: Octahedron
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Kaolinite 1:1
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1. Non-expandable
2. No extra ions 3. Basal spacing 7 angstroms 4. No edge changes |
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Smectite 2:1
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1. Non-expandable
2. K 3. Basal spacing 10 angstroms |
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Chlorite 2:1
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1. Non-expandable
2. Fe + Mg 3. Fe + Mg also in octahedral hydroxyl sheet 4. Basal spacing 14 angstroms |
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Smectite
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1. Very expanbable
2. lots of extra ions 3. Basal spacing basically 14 angstroms, but varies from 9-22. |
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Provenance
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Weathering of feldspars
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Weathering of feldspars: Kaolinite
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1. Expansive leaching of high alumina rocks
- Granite - Rhyolite - Gneiss 2. Low ph (not a lot of H) 3. Bauxite (from Cyanite/high aluminium rock |
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Weathering of Feldspars: Illite
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intermediate leaching of K-rich rocks
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Weathering of feldspars: Chlorite
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1. Poor leaching of Fe- and Mg-rich rocks
2. High ph |
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Weathering of feldspars: Smectite
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1. Poor leaching of Ca-, Na-, Fe-, and Mg-rich rocks
2. High ph |
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Diagenesis: Time
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1. Paleozoic:
- Illite - Chlorite 2. Kaolinite - Mezosoic and Cenozoic 3. Smectite - Cenozoic (very important) |
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Glauconite
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1. Iron rich Chlorite (2:1)
2. Greensands |
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Glauconite: Greensands
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1. Shallow marine sandstones
- Agitated - Formed in a reducing environment - Deposited in oxidizing environment - 50-200 m in depth - Slow accumulation - Shallowing upward sequences and below uncomformities |
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Bentonite
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1. Smectite (2:1)
- "Weathered" glass shards from ash - Deposited in marine environment - Time lines - Not good for radiometric dating |
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Black shales
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1. Usually organic rick
2. Unoxidized - anaerobic 3. Euxenic 4. Pyrite common 5. Modern sample: Black Sea 6. No good modern analogue from Mesozoic and Paleozoic shales - Perhaps due to poor circulation and mixing due to more uniform temperature 7. Chattanooga (Devonian) and Fayetteville (Mississipian) shales |
