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Sedimentary rocks (Structures (Normal bedding- a bed is deposited in a…
Sedimentary rocks
Structures
Normal bedding- a bed is deposited in a single pulse of sedimentation. Small beds are called laminae and are separated by lamination planes
Ripples/Dunes- <10cm ripples, >10cm dune. Asymmetric in shape as steep lee
Cross bedding- multiple inclined forest beds. Can have climbing ripples under rapid deposition. More than 5m= desert. 0.5 to 5m= shallow marine. 0.1 to 0.5= river. Less than 0.2m= beach
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Dessication Cracks- formed when a surface drys, contracts and cracks
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Rocks
CONGLOMERATE- coarse, poorly sorted, sub rounded, shingle beach, mature
BRECCIA- coarse, poorly sorted, sub angular, alluvial fan, immature
GREYWACKE- fine grained, moderately sorted, sub rounded, turbidity current, mature
ARKOSE- medium/coarse grained, moderately sorted, sub angular, flood plane of braided river, immature
ORTHOQUARTZITE- medium grained, well sorted, well rounded, beach/desert, mature
SHALE- fine grained, well sorted, deep sea
BIOCLASTIC LIMESTONE- medium/coarse grained, poorly sorted, warm tropical seas and beaches
CHALK- fine grained, well sorted, warm deep sea, cocoliths and micrite mud
OOLITHIC LIMESTONE- medium grained, well sorted, well rounded, calcite, tropical beaches, immature
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WEATHERING
mechanical
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FROST WEATHERING- expansion of ice within rock. When water freezes, it expands by 10% which creates stress especially on porous and fractured rock. Creates Scree/Talus
INSOLATION- daily expansion of rock due to the sun's heat, especially on dark rocks. Creates Scree/Talus
chemical
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CARBONATION- water reacts with limestone and changes it into soluble calcium carbonate. Creates calcium bicarbonate
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biological
disintegration or decomposition of rock due to the action of burrowing animals, tree roots and organic acids
Erosion
weathered debris or rock material is loosened and dissolved by mechanical and chemical action of water, ice and wind
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Flocculation- salt in sea water induces electrical charge causing clay particles to attract. They become bigger then sink
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