Geological formation

A geologic formation is a formally named rock stratum or geological unit. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant easily mapped and recognizable Formations are lithostratigraphic units which are defined by primary lithology. A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant easily mapped and recognizable In Geology, petrology (from Greek πέτρα petra, rock and λόγος logos, knowledge is the study of rocks and the conditions on which

The concept of formally defined layers or strata is central to the geologic discipline of stratigraphy. Stratigraphy, a branch of Geology, studies rock layers and layering ( stratification)

Usefulness of formations

Formations allow geologists to correlate geologic strata across wide distances between outcrops and exposures of rock strata. A geologist is a contributor to the Science of Geology, studying the physical structure and processes of the Earth and planets of the solar system Outcrop is a geological term referring to the appearance of Bedrock or Superficial deposits exposed at the surface of the Earth In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes

Formations were initially described to be the essential geologic time markers based on relative ages and the law of superposition. The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other The law of superposition (or the principle of superposition) is a key axiom based on observations of Natural history that is a foundational principle of sedimentary The divisions of the geological time scale were the formations described and put in chronological order by the geologists and stratigraphers of the 17th and 18th centuries. The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other

Modern revision of the geologic sciences has restricted Formations to lithologies, because lithological units are formed by depositional environments, some of which may persist for hundreds of millions of years and will transgress chronostratigraphic intervals or fossil-based methods of correlating rocks. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. For example, the Hammersley Basin is a Proterozoic sedimentary basin where up to 1200 million years of sedimentation is preserved within the intact sedimentary stratigraphy, with up to 300 million years represented by a single lithological unit of banded iron formation and shale. The Proterozoic (ˌproʊtərəˈzoʊɪk is a geological eon representing a period before the first abundant complex life on Earth. A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant easily mapped and recognizable

Geologic formations are usually sedimentary rock layers, but may also be metamorphic rocks and volcanic flows. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Plate tectonics and hotspots Divergent plate boundaries At the Igneous intrusive rocks are generally not divided into Formations.

Defining lithostratigraphic formations

Formations are the only formal lithostratigraphic units into which the stratigraphic column everywhere should be divided completely on the basis of lithology.

The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region and the detail needed for geologic mapping and to work out its geologic history.

Formations must be able to be delineated at the scale of geologic mapping practiced in the region. The thickness of formations may range from less than a meter to several thousand meters.

Geologic formations are typically named for the geographic area in which they were first described.

Strictly, formations cannot be defined on any other criteria except primary lithology. However, it is often useful to define Biostratigraphic units based on paleontological criteria, Chronostratigraphic units based on the age of the rocks, and Chemostratigraphic units based on geochemical criteria. A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant easily mapped and recognizable Palaeontology redirects here For the Scientific journal, see Palaeontology (journal. A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant easily mapped and recognizable A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant easily mapped and recognizable

Sequence stratigraphy is a concept which challenges the idea of strict lithostratigraphic units by defining units based on events in sedimentary basins such as oceanic regressions and transgressions. Sequence stratigraphy is a relatively new branch of Geology that attempts to link relative Sea-level changes to Sedimentary deposits These sequences are a combination of chronostratigraphic units, linked by time, and depositional environment linked by the geologic events which occurred at that time, regardless of the grain size of the sediments.

The term "formation" is often used informally to refer to a specific grouping of rocks, such as those encountered within a certain depth range in an oil well.

"Formation" is also used informally to describe the sometimes odd shapes (forms) that rocks acquire through erosional or depositional processes. Some well known cave formations include stalactites and stalagmites. A cave is a natural underground void large enough for a human to enter A stalactite ( Greek stalaktites, (Σταλακτίτης from the word for "drip" and meaning "that which drips" is a type of Speleothem A stalagmite (from the Greek stalagma ("Σταλαγμίτης" "drop" or "drip" is a

A geologic formation is said to be abandoned when it is no longer affected by the geologic agent that produced it.

Usefulness of formations

Defining lithostratigraphic formations

See also