Facies

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Facies

The term "Facies
Facies (medical)

In medical contexts, facies are distinctive facial expressions associated with specific medical conditions.It comes from the Latin word for "face"....
" can also refer to distinctive facial expressions associated with conditions such as Williams syndrome
Williams syndrome

Williams syndrome is a rare neurodevelopmental disorder caused by a deletion of about 26 genes from the long arm of chromosome 7. It is characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; mental retardation coupled with unusual language skills; a...
.

In geology

Geology

Geology is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the study of the composition, structural geology, physical properties, dynamics, and History of the Earth of Earth materials, and the processes by which they are formed, moved, and changed....
, facies are a body of rock with specified characteristics. [Reading (1996)] Ideally, a facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment.

The term facies was introduced by the Swiss geologist

Geologist

For other uses, see Geologist .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 ....
Amanz Gressly

Amanz Gressly

was a was a Switzerland Geology and Paleontology. He introduced the use of the term facies in geology, he is considered one of the founders of modern stratigraphy and paleoecology....
in 1838 and was part of his significant contribution to the foundations of modern stratigraphy

Stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary rock and layered volcanic rocks....
, [Cross and Homewood (1997)] which replaced the earlier notions of Neptunism

Neptunism

Neptunism is a discredited and obsolete scientific theory of geology proposed by Abraham Werner in the late 18th century that proposed Rock s formed from the crystallisation of minerals in the early Earth's oceans....
.

rally, facies are distinguished by what aspect of the rock or sediment is being studied.

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In geology

Geology

Geologist

Amanz Gressly

Stratigraphy

Neptunism

Facies types

Sedimentary facies

Generally, facies are distinguished by what aspect of the rock or sediment is being studied. Thus, facies based on petrological

Petrology

In geology, petrology is the study of Rock s, and the conditions in which they form. Lithology once was approximately synonymous with petrography, but in current usage, lithology is a subdivision of petrology focusing on macroscopic hand-sample or outcrop-scale description of rocks, while petrography is the speciality that deals with m...
characters such as grain size and mineralogy are called lithofacies

Lithofacies

Lithofacies may refer to:* A mappable subdivision of a designated stratigraphic unit, distinguished from adjacent subdivisions on the basis of lithology; a facies characterized by particular lithologic features....
, whereas facies based on fossil

Paleontology

File:Geological time spiral - sharper.pngPaleontology from Greek: pa?a??? "old, ancient", ??, ??t- "being, creature", and ????? "speech, thought" is the study of prehistory life, including organisms' evolution and interactions with each other and their environments ....
content are called biofacies.

These facies types are usually further subdivided, for examples, you might refer to a "tan, cross-bedded oolitic limestone

Limestone

File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record....
facies" or a "shale

Shale

Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
facies". The characteristics of the rock

Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
unit come from the depositional environment

Sedimentary depositional environment

In geology, sedimentary depositional 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....
and original composition. Sedimentary facies reflect depositional environment, each facies being a distinct kind of sediment for that area or environment.

Since its inception, the facies concept has been extended to related geological concepts. For example, characteristic associations of organic microfossils, and particulate organic material, in rocks or sediments, are called palynofacies

Palynofacies

Palynofacies studies examine the preservation of particulate organic matter and palynomorphs to provide information on the Sedimentary depositional environment of sediments and depositional palaeoenvironments of sedimentary....
. Discrete seismic

Seismology

Seismology is the scientific study of earthquakes and the propagation of Linear elasticity#Elastic waves through the Earth. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic, atmospheric, and artificial processes ....
units are similarly referred to as seismic facies.

Metamorphic facies

The sequence of minerals that develop during progressive metamorphism

Metamorphism

Metamorphism is the solid-state Crystallization of pre-existing Rock due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids....
(that is, metamorphism at progressivley higher temperatures) define a facies series and depend on the pressure, or range of pressures, at which the progressive metamorphism occurred.

Walther's Law of Facies

Walther's Law of Facies, named after the geologist Johannes Walther, states that the vertical succession of facies reflects lateral changes in environment. Conversely, it states that when a depositional environment "migrates" laterally, sediments of one depositional environment come to lie on top of another.(Stanley, 134) A classic example of this law is the vertical stratigraphic succession that typifies marine trangressions

Transgression (geology)

A marine transgression is a geology event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding....
and regressions. However, the law is not applicable where the contact between different lithologies is non-conformable (i.e. sedimentation was not continuous), or in instances of rapid environmental change where non-adjacent environments may replace one another.

Facies

Facies types

Sedimentary facies

Metamorphic facies

Walther's Law of Facies

See also