Depositional environment

In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record. In most cases, the environments associated with particular rock types or associations of rock types can be matched to existing analogues. However, the further back in geological time sediments were deposited, the more likely that direct modern analogues are not available (e.g. banded iron formations). Continental Alluvial – type of Fluvial deposit. Caused by moving water in a fan shape (Alluvial Fan) and containing mostly impermeable and nonporous sediments well sorted. Aeolian processes . Often in deserts and coastal regions and well sorted, large scale cross-beds Fluvial – processes due to moving water, mainly streams. Common sediments are gravel, sand, and silt. Lacustrine deposits – processes due to moving water, mainly lakes. Common sediments are sand, silt, and clay. Transitional River delta (possible cross beds, ripple marks) Common sediments are sand, silt, and clay. Tide – processes due to tidal currents, creates tidal flats (fine-grained, ripple marks, cross-beds). Common sediments are silt and clay Lagoon . Little transportation, creates lagoon bottom environment. Common sediments are carbonates (in tropical climates). Beach. Caused by waves and longshore currents. Creates beaches, spits, and sandbars with the common sediments of gravel and sand. Lake Marine Shallow water marine environment – processes due to waves and tidal currents, creates shelves and slopes, lagoons. Common sediments are carbonates (in tropical climates) or sand, silt, and clay (elsewhere) Upper shoreface Lower shoreface Abyssal plain (abyssal plains) caused by ocean currents. Common sediments are clay, carbonate mud, silica mud. Reef caused by waves and tidal currents. Also creates adjacent basins.