sediment structures
DESCRIPTION
sedimenTRANSCRIPT
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Lithification Sediments become rocks by lithification Compaction - lithification occurs as the weight of overlying sediments and rocks squeeze the sediments together into rock.Cementation - precipitates from groundwater and the growth of secondary minerals between the fragments may cement the rock. (Calcium, Silica)Fe in Silica can create Red SandstoneRecrystallization - minerals may reform or change owing to burial pressure and temperatures - does not necessarily make the rock metamorphic.
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Depositional EnvironmentsContinental: on a land mass; usually detrital (clastic) in a river; detrital.in a lake; detrital or chemical.by the wind; detrital.in the desert; detrital or chemical.by a glacier; detrital.in a delta; detrital.
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Alluvial Fan Deposits
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Sorting - degree to which the particles are the same size, i.e. if all the particles are the same size, then they are well-sorted. The following figure shows an increase in sorting, from left to right, from very poorly sorted through to very well sorted.
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Grain shape - reflects the degree of abrading during transport, length of transport, and resistance to weathering and abrasion.
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Depositional EnvironmentsMarine: in the oceans; detrital or chemical Reef: usually detrital, occasionally chemical.Shelf: on the continental shelf; detrital or chemical.Submarine channel or fan: detrital.Pelagic: deep sea ocean floor; usually chemical.
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Depositional EnvironmentsTransitional (shorelines): between land and sea; usually detrital. Linear: form long deposits (shorelines); can be detrital or chemical.
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Graded Bedding
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Cross Bedding
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Bedding Planes
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Ripple Marks
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Asymettric Ripples
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Mudcracks