Lithostratigraphy is the geological science associated with the study of strata or rock layers. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Science (from the Latin scientia, meaning " Knowledge " or "knowing" is the effort to discover, and increase human understanding In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes Major focuses of the study include geochronology, comparative geology, and petrology. In the Natural sciences under the umbrella of Natural history, Geochronology is the Science of determining the absolute age of rocks, Fossils In Geology, petrology (from Greek πέτρα petra, rock and λόγος logos, knowledge is the study of rocks and the conditions on which In general a stratum will be primarily igneous or sedimentary relating to how the rock was formed. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock)
Sedimentary layers are laid down by deposition of sediment associated with weathering processes, decaying organic matters (biogenic) or through chemical precipitation. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. These layers are distinguishable as having many fossils and are important for the study of biostratigraphy. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Biostratigraphy is the branch of Stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the Fossil assemblages contained Igneous layers are either plutonic or volcanic in character depending upon the cooling rate of the rock. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth. Plate tectonics and hotspots Divergent plate boundaries At the These layers are generally devoid of fossils and represent intrusions and volcanic activity that occurred over the geologic history of the area.
There are a number of principles that are used to explain the appearance of stratum. When an igneous rock cuts across a formation of sedimentary rock, then we can say that the igneous intrusion is younger than the sedimentary rock. The principle of superposition states that a sedimentary rock layer in a tectonically undisturbed stratum is younger than the one beneath and older than the one above it. 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 principle of original horizontality states that the deposition of sediments occurs as essentially horizontal beds.
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Types of Lithostratigraphic Units
A lithostratigraphic unit conforms to the law of superposition, which state that in any succession of strata, not disturbed or overturned since deposition, younger rocks lies above older rocks. The law of horizontal continuity states that a set of bed extends and can be traceable over a large area.
Lithostratigraphic units are recognized and defined on the basis of observable rock characteristics. The descriptions of strata based on physical appearance define facies. Lithostratigraphic units are only defined by lithic characteristics, and not by age.
Stratotype : A designated type of unit consisting of accessible rocks that contain clear-cut characteristics that are characteristic for a particular lithostratigraphic unit.
Lithosome: Masses of rock of essentially uniform character and having interchanging relationships with adjacent masses of different lithology. E. g. : Shale lithosome, limestone lithosome…
The fundamental Lithostratigraphic unit is the Formation. The formation is a lithologically distinctive stratigraphic unit that is large enough to be mappable and traceable.
Hierarchy of terms: Supergroup – Group – Formation – Member - Bed/Bed sets
Stratigraphic relationship
Two types of contact: Conformable and Unconformable.
Conformable: Unbroken deposition, no break or hiatus (break or interruption in the continuity of the geological record). The surface strata resulting is called a conformity.
Two types of contact between conformable stata: Abrupt contacts ( Directly separate beds of distinctly different lithology, minor depositional break, called Diastems) Gradational contact (Gradual change in deposition, mixing zone).
Unconformable: Period of erosion/non-deposition. The surface stratum resulting is called an unconformity.
Four types of unconformity
Angular unconformity Younger sediment lies upon an eroded surface of tilted or folded older rocks. The older rock dips at a different angle than the younger.
Disconformity The contact between younger and older beds is marked by visible, irregular erosional surfaces. Paleosol might develop right above the disconformity surface because of the non-deposition setting.
Paraconformity The bedding plans below and above the unconformity are parallel. A time gap is present but there is no erosion, just a non-deposition period.
Nonconformity Relatively young sediments are deposited right above older Igneous or metamorphic rocks.
Lithostratigraphic correlation
To correlate Lithostratigraphic units, you need to define Facies. You also need to find key beds or Key sequences that can act as datum.
Direct correlation: based on Lithology, Color, Structure, Thickness…
Indirect correlation: Electric log correlation (Gamma-ray, density, Resistivity…)
Three ways of correlating a sequence: Biostratigraphy, Lithostratigraphy, Chronostratigraphy.
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See also
External links
Biostratigraphy is the branch of Stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the Fossil assemblages contained Chronostratigraphy is the branch of Stratigraphy that studies the age of rock strata in relation to Time.Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic