Sedimentary rocks Flashcards
What grain size is orthoquartzite?
Arenaceous
What is the sorting and grain shape of orthoquartzite?
Well sorted
Round
What colour are orthoquartzite?
White
Grey
Where is orthoquartzite often form?
Beach
Shallow Marine deposits
What is the composition of orthoquartzite?
Silicic
What is the grain size of arkose?
Arenaceous
What is the composition of arkose?
Mafic
What is the grain shape and sorting of arkose?
Sub-angular to sub-rounded
Moderately sorted
What is the colour of arkose?
Pink
What is the colour of greywacke?
Dark coloured
What is the composition of greywacke?
Mafic
What is the grain size of greywacke?
Arenaceous
What is the grain shape and sorting of greywacke?
Poorly sorted
Angular to sub-angular grains
What is the grain size of mudstone?
Argillaceous
What is the mineral composition of mudstone?
Clay
Mica
Quartz
Mudstone
Contains mud - particles of clay and fine silt
Less then 10% grains
Mud supported
Wackestone
More than 10% grains
Contains mud - clay and fine silt
Mud supported
Packstone
Grain supported
Grainstone
Lacks mud
What grain size is breccia?
Rudaceous
What sorting is breccia?
Poorly sorted
What is the grain shape of breccia?
Angular
Where do breccia usually form?
Scree
Alluvial fans
Wadi deposits
What is the grain size of conglomerate?
Rudaceous
What is the sorting of a conglomerate?
Poorly sorted
What is the grain shape of conglomerate?
Rounded
What colours can clay be?
Brown
Red
Green
Why is shale fissile?
Rock easily splits along the laminations of the rock.
What are the two groups of limestone?
Chemical limestone formed by the precipitation of CaCO3 from sea water.
Biological limestone formed from organic remains remains such as shell fragments.
What are ooliths surrounded by in oolitic limestone?
Fine grained calcite mud matrix (micrite)
or
crystalline calcite cement (sparite)
Where does oolitic limestone form?
Sub-tropical seas, in shallow water agitated by high energy waves
What type of limestone is oolitic limestone?
Chemical
What type of limestone is fossiliferous limestone?
Biological
How would you describe fossiliferous limestone?
Bioclastic
What is chalk?
Biologically formed limestone
Composed of coccoliths
Pure CaCO3
Low energy, deep water shelf environments
What is the grain size for argillaceous rocks?
<0.0625mm
What is the grain size for arenaceous rocks?
0.0625-2mm
What is the grain size for rudaceous rocks?
> 2mm