An Introduction to Geology Sedimentary Rocks Back to

An Introduction to Geology Sedimentary Rocks

Back to the Rock Cycle

Sedimentary processes 1. Weathering 2. Transportation 3. Deposition 4. Lithification OF A. Existing rocks B. Biological materials C. Chemical precipitates

Sedimentary processes

Common sedimentary minerals Feldspars Quartz Micas Calcite

Hand specimens First impressions?

Weathering Physical / Mechanical

Weathering Chemical / Biological

Weathering = clasts

Transportation

Transport mechanisms Rivers = fluvial Mississippi delta Seas = marine

Transport mechanisms AEOLIAN (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:

Deposition Transportation into basins

Lithification Deposition (+ deposition) = burial Burial = compaction + cementation

Compaction Stylolites in chalk

Cementation • Mineral precipitation into pore spaces: • e. g. calcite, quartz, haematite

Hand specimens Second impressions?

Sedimentary rocks Particle size, shape and composition Grain size >2 mm Classification Rudaceous Example Conglomerate

Conglomerate

Sedimentary rocks Particle size, shape and composition Grain size Classification Example >2 mm Rudaceous Conglomerate 0. 06 -2 mm Arenaceous Sandstone

Sandstone

Sedimentary rocks Particle size, shape and composition Grain size Classification Example >2 mm Rudaceous Conglomerate 0. 06 -2 mm Arenaceous Sandstone 0. 004 -0. 06 mm Argillaceous Siltstone

Siltstone

Sedimentary rocks Particle size, shape and composition Grain size Classification Example >2 mm Rudaceous Conglomerate 0. 06 -2 mm Arenaceous Sandstone 0. 004 -0. 06 mm Argillaceous Siltstone <0. 004 mm Claystone Argillaceous