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San Sebastián San Sebastián () or Donostia () is a coastal city and municipality located in the Basque Autonomous Community, Spain. It lies on the coast of the Bay of Biscay, from the French border. The capital city of the province of Gipuzkoa, the municipa ...
,
Spain , * gl, Reino de España, * oc, Reiaume d'Espanha, , , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = , national_anthem = , image_map = , map_caption = , image_map2 = , ...
The geologic record in
stratigraphy through Jurassic strata of the Colorado Plateau area of southeastern Utah demonstrate the principles of stratigraphy. Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primari ...
,
paleontology Paleontology, also spelled palaeontology or palæontology (), is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene Epoch (roughly 11,700 years before present). It includes the study of fossils ...
and other
natural sciences Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatability of fin ...
refers to the entirety of the layers of rock
strata (Argentina). , Canada. These are Middle Cambrian marine sediments. This formation covers over half of Nova Scotia and is recorded as being 8,800 m (29,000 ft) thick in some areas. In geology and related fields, a stratum (plural: strata) is a l ...
. That is, deposits laid down by
volcanism Volcanism (or volcanicity) is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called a vent. It inc ...
or by deposition of sediment derived from
weathering Weathering is the breaking down of rocks, soils, and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
detritus (
clay Clay is a type of fine-grained natural soil material containing clay minerals. Clays develop plasticity when wet, due to a molecular film of water surrounding the clay particles, but become hard, brittle and non–plastic upon drying or firing. ...

clay
s,
sand Sand is a granular material composed of finely divided rock and mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural cla ...
s etc.). This includes all its
fossil A fossil (from Classical Latin: , literally "obtained by digging") is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or ...
content and the information it yields about the history of the Earth: its past
climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
, geography, geology and the
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different character ...

evolution
of life on its surface. According to the
law of superposition 250px, Layer upon layer of rocks on north shore of Isfjord, Svalbard, Norway. Since there is no overturning, the rock at the bottom is older than the rock on the top by the Law of Superposition. The law of superposition is an axiom that forms ...
,
sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at the Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to ...
and
volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are d ...

volcanic
rock layers are deposited on top of each other. They harden over time to become a solidified ( competent) rock column, that may be intruded by
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lav ...
s and disrupted by
tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents kn ...
events.


Correlating the rock record

near
Drumheller Drumheller is a town within the Red Deer River valley in the badlands of east-central Alberta, Canada. It is located northeast of Calgary, and south of Stettler. The Drumheller portion of the Red Deer River valley, often referred to as Dinos ...
,
Alberta ("Strong and free") , image_map = Alberta in Canada 2.svg , Label_map = yes , coordinates = , official_lang = English , capital = Edmonton , largest_city = Calgary , l ...
At a certain locality on the Earth's surface, the rock column provides a Cross section (geometry), cross section of the
natural history Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is calle ...
in the area during the time covered by the age of the rocks. This is sometimes called the ''rock history'' and gives a window into the natural history of the location that spans many geological time units such as ages, epochs, or in some cases even multiple major geologic periods—for the particular
geographic Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the word γεωγραφ ...
region or regions. The geologic record is in no one place entirely complete for where geologic forces one age provide a low-lying region accumulating
deposits A deposit account is a bank account maintained by a financial institution in which a customer can deposit and withdraw money. Deposit accounts can be savings accounts, current accounts or any of several other types of accounts explained below. Tr ...
much like a layer cake, in the next may have uplifted the region, and the same area is instead one that is
weathering Weathering is the breaking down of rocks, soils, and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
and being torn down by chemistry, wind, temperature, and water. This is to say that in a given location, the geologic record can be and is quite often interrupted as the ancient local environment was converted by geological forces into new
landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, mountains ...
s and features. Sediment core data at the mouths of large riverine drainage basins, some of which go deep thoroughly support the law of superposition. However using broadly occurring deposited layers trapped within differently located rock columns, geologists have pieced together a system of units covering most of the
geologic time scale The geologic time scale (GTS) is a system of chronological dating that classifies geological strata (stratigraphy) in time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events i ...
using the law of superposition, for where tectonic forces have uplifted one ridge newly subject to
erosion In earth science, erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location. Erosion is distinct from ...

erosion
and
weathering Weathering is the breaking down of rocks, soils, and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
in
folding Fold or folding may refer to: Arts, entertainment, and media *''Fold'' (album), the debut release by Australian rock band Epicure *Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Above the fold, ...
and
faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within the Earth's crust result from the action of plate tectonic ...
the strata, they have also created a nearby trough or
structural basin A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as b ...
region that lies at a relative lower elevation that can accumulate additional deposits. By comparing overall formations, geologic structures and local strata, calibrated by those layers which are widespread, a nearly complete geologic record has been constructed since the 17th century.


Discordant strata example

left, USGS correlation diagram Correcting for discordancies can be done in a number of ways and utilizing a number of technologies or field research results from studies in other disciplines. In this example, the study of layered rocks and the fossils they contain is called
biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Biolog ...
and utilizes amassed
geobiology Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a relatively young field, and its borders are fluid. There is considerable overlap with the fields of ecology, evolutiona ...
and
paleobiological Paleobiology (or palaeobiology) is a growing and comparatively new discipline which combines the methods and findings of the life science biology with the methods and findings of the earth science paleontology. It is occasionally referred to as "g ...
knowledge. Fossils can be used to recognize rock layers of ''the same or different geologic ages'', thereby coordinating locally occurring geologic stages to the overall geologic timeline. The pictures of the fossils of monocellular algae in this
USGS The United States Geological Survey (USGS, formerly simply Geological Survey) is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural ha ...
figure were taken with a scanning electron microscope and have been magnified 250 times. In the U.S. state of
South Carolina South Carolina () is a state in the Southeastern region of the United States. It is bordered to the north by North Carolina, to the southeast by the Atlantic Ocean, and to the southwest by Georgia across the Savannah River. South Carolina is th ...

South Carolina
three marker species of fossil algae are found in a core of rock whereas in
Virginia Virginia (), officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are s ...

Virginia
only two of the three species are found in the
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "dawn") ...
Series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used in ...
of rock layers spanning three
stages Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Stage ...
and the geologic ages from 37.2–55.8 MA. Comparing the record about the discordance in the record to the full rock column shows the non-occurrence of the missing species and that portion of the local ''rock record'', from the early part of the middle Eocene is missing there. This is one form of discordancy and the means geologists use to compensate for local variations in the rock record. With the two remaining marker species it is possible to
correlate In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. In the broadest sense correlation is any statistical association, though it commonly refers to the ...
rock layers of the same age (early Eocene and latter part of the middle Eocene) in both South Carolina and Virginia, and thereby "calibrate" the local rock column into its proper place in the overall geologic record.


Lithology vs paleontology

Consequently, as the picture of the overall rock record emerged, and discontinuities and similarities in one place were cross-correlated to those in others, it became useful to subdivide the overall geologic record into a series of component sub-sections representing different sized groups of layers within known geologic time, from the shortest time span
stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Stage ...
to the largest thickest strata
eonothem near Drumheller, Alberta. Image:Péry-Reuchenette Oxfordian.JPG, 200px, Oxfordian (Upper Jurassic) cyclic sediments at Péry-Reuchenette, near Tavannes, kanton Bern, Switzerland. Alternating layers are limestone (light, more Competence (geology), c ...
and time spans eon. Concurrent work in other natural science fields required a time continuum be defined, and earth scientists decided to coordinate the system of rock layers and their identification criteria with that of the geologic time scale. This gives the pairing between the physical layers of the left column and the time units of the center column in the table at right. Image:Dinosaur Park Fm.jpg, Well
stratified Stratification may refer to: In mathematics: * Stratification (mathematics), any consistent assignment of numbers to predicate symbols * Data stratification in statistics In earth sciences: * Stable and unstable stratification * Stratification, ...
and fully exposed Dinosaur Park formations (in Dinosaur Provincial Park,
Alberta ("Strong and free") , image_map = Alberta in Canada 2.svg , Label_map = yes , coordinates = , official_lang = English , capital = Edmonton , largest_city = Calgary , l ...
,
Canada Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering , making it the world's second-largest country by total ...

Canada
) and like formations that extend for over a thousand miles exposing eons of rock history through numerous wind and water exposed strata layers— which in the
Colorado Plateau The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area of 33 ...
are miles thick.Annabelle Foos, 1999
GEOLOGY OF THE COLORADO PLATEAU
– www.tribesandclimatechange.org
Image:DeepSiltOffMirabeau.jpg,
New Orleans New Orleans (,New Orleans
Hurricane Katrina Hurricane Katrina was a large Category 5 Atlantic hurricane that caused over 1,800 deaths and $125 billion in damage in August 2005, particularly in the city of New Orleans and the surrounding areas. It was at the time the costliest tropical ...
: Unlithified sediment layers laid down in historic times. This cut was an attempt to find bedrock near a residential street near the lower breach of the
London Avenue CanalThe London Avenue Canal is a drainage canal in New Orleans, Louisiana, used for pumping rain water into Lake Pontchartrain. The canal runs through the 7th Ward of New Orleans from the Gentilly area to the Lakefront. It is one of the three main draina ...
after restoring the levees which has been plowed/excavated clear by the Army Corps of Engineers, showing a nascent stratigraphy in the large deposits of silt deposited by flooding in recent earth history. Image:Tremp formatie.jpg, Three eras of deposition and two discordancies are visible in this highway cut in the Netherlands. Note the color and slight angular change between the lower red bed layering and the middle strata. The upper strata are tilted yet again relative to the bottom layerings well demonstrating the cycles this land formation went through as part of the sea floor. Image:Péry-Reuchenette Oxfordian.JPG, Oxfordian (Upper Jurassic) cyclic sediments at Péry-Reuchenette, near Tavannes, kanton Bern, Switzerland. Alternating layers are
limestone Limestone is a common type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (). Limestone forms when these minerals precipitate out of water con ...
(light, more competent) and
marl __NOTOC__ Marl or marlstone is a carbonate-rich mud or mudstone which contains variable amounts of clays and silt. The term was originally loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chief ...
/
clay Clay is a type of fine-grained natural soil material containing clay minerals. Clays develop plasticity when wet, due to a molecular film of water surrounding the clay particles, but become hard, brittle and non–plastic upon drying or firing. ...

clay
; dominant cycle is the 200,000 year-cycle. Image:Time-Honored Rockfall.jpg, An ancient rockfall which protected the rock records beneath its impact site from further large scale erosion. Taken along Burr Trail,
Grand Staircase-Escalante National Monument Grand may refer to: People with the name * Grand (surname) * Grand L. Bush (born 1955), American actor * Grand Mixer DXT, American turntablist * Grand Puba (born 1966), American rapper * Places * Grand, Oklahoma * Grand, Vosges, village and commun ...
, Utah, USA. Image:PS2492-2 0017-1298 photo.jpg, Sediment core, taken with a gravity corer by the research vessel POLARSTERN in the South Atlantic; light/dark-coloured changes are due to climatic variation of the
Quaternary Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million ...
; basis age of the core is about 1 million years.


References

{{DEFAULTSORT:Geologic Record
Paleontology Paleontology (US spelling) or palaeontology (UK spelling) is the study of the developing history of life on earth, of ancient plants and animals based on the fossil record, evidence of their existence preserved in rocks. This includes the study of ...
Zoology Zoology is the study of the biology of animals. Zoology {{CatAutoTOC ...
Fossils
Historical geology Historical geology is a discipline that uses the principles and techniques of geology to reconstruct and understand the geological history of Earth. Articles about that subject are categorized under . Subfields of geology {{CatAutoT ...
Geologic time scales of Earth {{see also, Geologic record Earth Geologic time scales ...
Geochronology
StratigraphyStratigraphy is the science of sedimentary rock strata or layers. {{portal, Geology Subfields of geology ...