An Introduction to Geology
Sedimentary Rocks
Back to the Rock Cycle
Sedimentary processes
1. Weathering
2. Transportation
3. Deposition
4. Lithification
A. Existing rocks
B. Biological materials
C. Chemical precipitates
OF
Sedimentary processes
Common sedimentary minerals
Quartz Feldspars
Micas
Calcite
Hand specimens
First impressions?
Weathering
Physical /
Mechanical
Weathering
Chemical /
Biological
Weathering = clasts
Transportation
Transport mechanisms
Rivers = fluvial
Seas = marineMississippi delta
Transport mechanismsAEOLIAN (wind)Can only transport small grains
GLACIAL (ice)Huge volumes of sediment
Transportation
Proximity + velocity = grain size
Transport time = maturity
Textural maturity:
Transport time = maturity
Mineralogical maturity:
DepositionTransportation into basins
LithificationDeposition (+ deposition + deposition) = burialDeposition (+ deposition + deposition) = burial
Burial = compaction + cementationBurial = compaction + cementation
Compaction
Stylolites in chalk
Cementation•Mineral precipitation into pore spaces:•e.g. calcite, quartz, e.g. calcite, quartz, haematitehaematite
Hand specimens
Second impressions?
Sedimentary rocks
Grain sizeGrain size ClassificationClassification ExampleExample
>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate
Particle size, shape and composition
Conglomerate
Sedimentary rocks
Grain sizeGrain size ClassificationClassification ExampleExample
>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate
0.06-2 mm0.06-2 mm ArenaceousArenaceous SandstoneSandstone
Particle size, shape and composition
Sandstone
Sedimentary rocks
Grain sizeGrain size ClassificationClassification ExampleExample
>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate
0.06-2 mm0.06-2 mm ArenaceousArenaceous SandstoneSandstone
0.004-0.06 mm0.004-0.06 mm ArgillaceousArgillaceous SiltstoneSiltstone
Particle size, shape and composition
Siltstone
Sedimentary rocks
Grain sizeGrain size ClassificationClassification ExampleExample
>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate
0.06-2 mm0.06-2 mm ArenaceousArenaceous SandstoneSandstone
0.004-0.06 mm0.004-0.06 mm ArgillaceousArgillaceous SiltstoneSiltstone
<0.004 mm<0.004 mm ArgillaceousArgillaceous ClaystoneClaystone
Particle size, shape and composition
Claystone
Bituminous shales, Saltwick Nab, near Whtby
Sedimentary rock types1. Clastic (or detrital)
Sedimentary rock types1. Clastic (or detrital)
Sedimentary rock types2. Biogenic (or organic)
Sedimentary rock types2. Biogenic (or organic)
Sedimentary rock types3. Chemical (precipitates)
Hand specimens
What sedimentary rock type is your specimen?
Sedimentary structures
Bedding
Sedimentary structuresCross-bedding
Sedimentary structuresCross-bedding
Sedimentary structures
Ripple marks
Sedimentary structures
Mud cracks
Sedimentary structuresShell beds
Sedimentary structuresTrace fossils
Sedimentary UK
Next weekUnder Pressure: Metamorphic Rocks
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