Editing Sedimentology (section)

== Basic principles ==
[[Image:HeavyMineralsBeachSand.jpg|thumb|right|Heavy minerals (dark) deposited in a [[quartz]] beach [[sand]] ([[Chennai]], India).]]
The aim of sedimentology, studying sediments, is to derive information on the depositional conditions which acted to deposit the rock unit, and the relation of the individual rock units in a basin into a coherent understanding of the evolution of the sedimentary sequences and basins, and thus, the Earth's geological history as a whole.{{cn|date=March 2024}}

The scientific basis of this is the principle of uniformitarianism, which states that the sediments within ancient sedimentary rocks were deposited in the same way as sediments which are being deposited at the Earth's surface today.<ref>{{cite journal |last1=Kravitz |first1=Gadi |title=The Geohistorical Time Arrow: From Steno's Stratigraphic Principles to Boltzmann's Past Hypothesis |journal=Journal of Geoscience Education |date=November 2014 |volume=62 |issue=4 |pages=691-700 |url=https://files.eric.ed.gov/fulltext/EJ1164156.pdf |access-date=18 February 2025}}</ref>

Sedimentological conditions are recorded within the sediments as they are laid down; the form of the sediments at present reflects the events of the past and all events which affect the sediments, from the source of the sedimentary material to the stresses enacted upon them after [[diagenesis]] are available for study.{{cn|date=March 2024}}

The [[Law of superposition|principle of superposition]] is critical to the interpretation of sedimentary sequences, and in older metamorphic terrains or fold and thrust belts where sediments are often intensely [[fold (geology)|folded]] or deformed, recognising [[Younging direction|younging]] indicators or [[graded bedding]] is critical to interpretation of the sedimentary section and often the deformation and metamorphic structure of the region.{{cn|date=March 2024}}

Folding in sediments is analysed with the [[principle of original horizontality]], which states that sediments are deposited at their angle of repose which, for most types of sediment, is essentially horizontal. Thus, when the younging direction is known, the rocks can be "unfolded" and interpreted according to the contained sedimentary information.

The [[principle of lateral continuity]] states that layers of sediment initially extend laterally in all directions unless obstructed by a physical object or topography.

The [[principle of cross-cutting relationships]] states that whatever cuts across or intrudes into the layers of strata is younger than the layers of strata.