Editing Sedimentary rock (section)

== Deposition and transformation ==

=== Sediment transport and deposition ===
[[File:Logan Formation Cross Bedding Scour.jpg|thumb|upright=1.1|Cross-bedding and scour in a fine [[sandstone]]; the [[Logan Formation]] ([[Mississippian (geology)|Mississippian]]) of Jackson County, [[Ohio]]]]

Sedimentary [[rock (geology)|rocks]] are formed when [[sediment]] is [[deposition (geology)|deposited]] out of air, ice, wind, gravity, or water flows carrying the particles in [[Suspension (chemistry)|suspension]]. This sediment is often formed when [[weathering]] and [[erosion]] break down a rock into loose material in a source area. The material is then [[Sediment transport|transported]] from the source area to the deposition area. The type of sediment transported depends on the geology of the [[hinterland (geology)|hinterland]] (the source area of the sediment). However, some sedimentary rocks, such as [[evaporite]]s, are composed of material that form at the place of deposition. The nature of a sedimentary rock, therefore, not only depends on the sediment supply, but also on the [[sedimentary depositional environment]] in which it formed.

=== Transformation (Diagenesis) ===
[[File:Pressure solution sandstone.svg|thumb|[[Pressure solution]] at work in a [[clastic rock]]. While material dissolves at places where grains are in contact, that material may recrystallize from the solution and act as cement in open pore spaces. As a result, there is a net flow of material from areas under high stress to those under low stress, producing a sedimentary rock that is harder and more compact. Loose sand can become sandstone in this way.]]
{{main|Diagenesis}}

As sediments accumulate in a depositional environment, older sediments are buried by younger sediments, and they undergo diagenesis. Diagenesis includes all the chemical, physical, and biological changes, exclusive of surface weathering, undergone by a sediment after its initial deposition. This includes [[compaction (geology)|compaction]] and [[lithification]] of the sediments.{{sfn|Boggs|2006|pp=147-154}} Early stages of diagenesis, described as ''eogenesis'', take place at shallow depths (a&nbsp;few tens of meters) and is characterized by [[bioturbation]] and mineralogical changes in the sediments, with only slight compaction.{{sfn|Choquette|Pray|1970}} The red [[hematite]] that gives [[red bed]] sandstones their color is likely formed during eogenesis.{{sfn|Walker|Waugh|Grone|1978}}{{sfn|Boggs|2006|pp=147-154}} Some [[biochemical]] processes, like the activity of [[bacteria]], can affect minerals in a rock and are therefore seen as part of diagenesis.{{sfn|Picard|Kappler|Schmid|Quaroni|2015}} Another example of sedimentary diagenesis is the [[Dolomitization|dolomitzation]] of rocks such as limestone.<ref>{{Cite journal |last1=Chen |first1=Chao |last2=Zhong |first2=Hanting |last3=Wang |first3=Xinyu |last4=Ning |first4=Meng |last5=Wang |first5=Xia |last6=Ge |first6=Yuzhu |last7=Wang |first7=Han |last8=Tang |first8=Ruifeng |last9=Hou |first9=Mingcai |date=December 2023 |title=Thermodynamic and Kinetic Studies of Dolomite Formation: A Review |journal=Minerals |language=en |volume=13 |issue=12 |pages=1479 |doi=10.3390/min13121479 |doi-access=free |bibcode=2023Mine...13.1479C |issn=2075-163X}}</ref>

Deeper burial is accompanied by ''mesogenesis'', during which most of the compaction and lithification takes place. Compaction takes place as the sediments come under increasing [[overburden pressure|overburden (lithostatic) pressure]] from overlying sediments. Sediment grains move into more compact arrangements, grains of ductile minerals (such as [[mica]]) are deformed, and pore space is reduced. Sediments are typically saturated with [[groundwater]] or seawater when originally deposited, and as pore space is reduced, much of these [[connate fluids]] are expelled. In addition to this physical compaction, chemical compaction may take place via [[pressure solution]]. Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact.{{sfn|Boggs|2006|pp=147-154}} The increased pressure and temperature stimulate further chemical reactions, such as the reactions by which [[organic material]] becomes [[lignite]] or coal.{{sfn|Kentucky Geological Survey|2020}}

Lithification follows closely on compaction, as increased temperatures at depth hasten the [[precipitation (chemistry)|precipitation]] of cement that binds the grains together. Pressure solution contributes to this process of [[cementation (geology)|cementation]], as the mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. This further reduces porosity and makes the rock more compact and [[Competence (geology)|competent]].{{sfn|Boggs|2006|pp=147-154}}

Unroofing of buried sedimentary rock is accompanied by ''telogenesis'', the third and final stage of diagenesis.{{sfn|Choquette|Pray|1970}} As erosion reduces the depth of burial, renewed exposure to [[meteoric water]] produces additional changes to the sedimentary rock, such as [[Leaching (chemical science)|leaching]] of some of the cement to produce [[secondary porosity]].{{sfn|Boggs|2006|pp=147-154}}

At sufficiently high temperature and pressure, the realm of diagenesis makes way for [[metamorphism]], the process that forms [[metamorphic rock]].{{sfn|Brime|García-López|Bastida|Valín|2001}}