Sedimentary Rocks - Environments

Energy of Clast Transport
- Clasts stop moving when transporting agent energy is insufficient.
- Grain size reflects energy of transport.
Key Clastic Environments
- Terrestrial
- Close to source: debris from alluvial fans, rock slides, etc.
- High energy = Breccia, Arkose (angular, poorly sorted).
- Fast upland rivers lead to Conglomerate (rounded, coarse).
- Rivers on plains lead to Sandstone (more mature, well sorted).
- Marginal Marine
- Beaches - Moderate energy with well-rounded sand & Quartz Sandstone.
- Marine
- Very far from source, low energy environments.
- Deep marine forms Siltstone & Shale (fine, well sorted).

Types of Chemical Sedimentary Rocks
- Halides:
- Halite (NaCl) - Rock Salt.
- Carbonates:
- Calcite (CaCO3) - Limestone.
- Dolomite (CaMg(CO3)2) - Dolostone.
- Silica: Chalcedony - Chert.
Evaporite Formation
- Occurs in restricted water bodies under high evaporation rates.
- Cations and anions from terrestrial weathering lead to precipitation in hot, dry climates.
Limestone Formation
- Precipitation from water, requires Ca2+ from weathering and CO32- from dissolved CO2.
- Reaction with acid indicates presence of calcite.
Factors Affecting Limestone Formation
- pH of water: Lower pH facilitates certain processes; warm & basic water promotes calcite formation.
Types of Limestone
- Micritic, Fossiliferous, Oolitic, Crystalline Limestone.
Dolostone Formation
- Results from magnesium replacement of calcium in calcite; origin remains controversial.