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A diagram of various depositional environments. 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.
These structures are within sedimentary bedding and can help with the interpretation of depositional environment and paleocurrent directions. They are formed when the sediment is deposited. Cross-bedding Cross-bedding is the layering of beds deposited by wind or water inclined at an angle as much as 35° from the horizontal. [1]
Cyclic sedimentation occurs when the depositional environments change repeatedly. Changes in the environment of deposition influence the type and amount of sediments that are deposited, producing different sedimentary rock types. At least one rock type, which is regarded as the starting point, must be repeated.
Normally graded beds generally represent depositional environments which decrease in transport energy (rate of flow) as time passes, but these beds can also form during rapid depositional events. They are perhaps best represented in turbidite strata , where they indicate a sudden strong current that deposits heavy, coarse sediments first, with ...
Conglomerates deposited in fluvial environments are typically well rounded and poorly sorted. Clasts of this size are carried as bedload and only at times of high flow-rate. The maximum clast size decreases as the clasts are transported further due to attrition , so conglomerates are more characteristic of immature river systems.
Figure 1 illustrates this relationship between sediment grain size and the depth of the marine environment. Figure 1. Illustrating the sediment size distribution over a shoreline profile, where finer sediments are transported away from high energy environments and settle out of suspension, or deposit in calmer environments.
Robert J. Dunham published his classification system for limestone in 1962. [2] The original Dunham classification system was developed in order to provide convenient depositional-texture based class names that focus attention on the textural properties that are most significant for interpreting the depositional environment of the rocks.
Techniques used to study surficial sedimentary rocks include: measuring stratigraphic sections, identifying sedimentary depositional environments and constructing a geologic map. [ 3 ] An important tool in sedimentary basin analysis is sequence stratigraphy , in which various sedimentary sequences are related to pervasive changes in sea level ...