Sedimentary Structures

Sedimentary structures are commonly formed as a result of erosion, deposition, or because of postdepositional deformation of sediments. Understanding the mechanisms by which sedimentary structures form is an important tool for geologists to understand the evolving depositional record. Although mechanisms of erosion remove sediment, and therefore remove components of this record, it still leads to the preservation of unique structures that allow for an interpretation of the depositional environment (e.g., certain channel forms could be interpreted as fluvial) and even paleocurrent (e.g., bimodal directions from drag marks). Processes that lead to deposition are equally as important. Most sedimentary structures formed due to deposition give a clear indication of depositional process, for example, asymmetrical ripples suggest a unidirectional flow. Some depositional structures are even indicative of very specific processes, for example, herringbone cross stratification indicates a tidally-dominated environment. After deposition, various forces acting on the sediments can alter the preserved structures. Soft sediment deformation, for example, can lead to slumping, load and flame structures, or clastic dykes. An understanding of the combination of processes that lead to erosional, depositional, and postdepositional structures in a sediment can lead to sound paleoenvironment reconstructions. The nature of a sedimentary body has numerous applications, for example, for identifying adequate aquifers for groundwater.