Coarse and medium grained clastic sedimentary rocks
Breccia, conglomorate, sandstone, orthoquartzite, desert sandstone, arkose, greywacke
- Created by: Brad_ers_B
- Created on: 28-04-14 21:19
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- Coarse and medium grained clastic sedimentary rocks
- Breccia
- Coarse grained clastic, angular rock, poorly sorted
- Coarse clasts often mixed with finer grains and set in matrix
- Commonly form as scree, alluvial fans and wadi deposits
- Conglomerate
- Coarse grained clastic, rounded rock
- Poorly sorted, Large clasts surrounded by a finer grained matrix
- Commonly form as beach and river channel deposits
- Sandstones
- May be well cemented meaning low porosity or poorly cemented meaning high porosity
- Main component is quartz but also minerals low on Bowen's R S
- Found in virtually all sedimentary environments
- Orthoquartzite
- A Sandstone, consists of only quartz grains held by quartz cement
- Grains are well sorted and well rounded
- Commonly form in beach and shallow marine deposits
- Desert sandstone
- Red in colour due to iron oxide coating the quartz grains
- Very well sorted, very well rounded, medium sand-sized grains having high sphericity
- Commonly form in arid environments as wind blown sands
- Clasts cemented together by silica or iron minerals
- Arkose
- Medium to coarse grained sandstone containing at least 25% K feldspar
- Other main mineral is quartz though fragments of rock and mica may be present
- Grains are sub-angular to sub-rounded
- Commonly formed in alluvial fan environments in arid areas
- Greywacke
- Fine to coarse in grain size
- Dark coloured and poorly sorted with angular to sub-angular clasts
- Clasts usually consist of rock fragments with some quartz and K feldspar
- More than 15% of it is clay matrix
- Commonly form as turbidite deposits and often show graded bedding
- Breccia
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