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Lithology is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping and correlation between areas. In certain applications, such as site investigations, lithology is described using a standard terminology such as in the European geotechnical standard Eurocode 7.
Lithostratigraphic units are recognized and defined on the basis of observable physical rock characteristics. The lithology of a unit includes characteristics such as chemical and mineralogical composition, texture, color, primary depositional structures, fossils regarded as rock-forming particles, or other organic materials such as coal or ...
Lithology: A description of the rock's physical characteristics, such as grain size, composition and texture. [4] By studying the lithology of local geological outcrops and core samples, geoscientists can use a combination of log measurements, such as natural gamma, neutron, density and resistivity, [2] to determine the lithology down the well.
The Summerville Formation is composed of alternating thin beds of two lithologies, mudstone and sandstone, penetrated by veins of a third lithology, gypsum. The boundaries of a formation are chosen to give it the greatest practical lithological consistency. Formations should not be defined by any criteria other than lithology.
Rocks formations and the Dedo de Deus (God's Finger) peak in the background, Serra dos Órgãos National Park, Rio de Janeiro state, Brazil Raouché or Pigeons' Rock in Beirut, Lebanon Druid Arch, Canyonlands National Park, Utah, US View of Meteora, Greece Rock formations in Ongamira Valley, Sierras de Córdoba, Argentina Belogradchik Rocks, Balkan Mountains, Bulgaria "Jaws", an erosional fin ...
Units of formation or higher rank are usually named for the unit's type location, and the formal name usually also states the unit's rank or lithology. A lithostratigraphic unit may have a change in rank over a some distance; a group may thin to a formation in another region and a formation may reduce in rank for member or bed as it "pinches out".
The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England.
Examples of ophiolites that have been influential in the study of these rocks bodies are: Coast Range Ophiolite in the California Coast Ranges, from Santa Barbara through San Francisco Counties, California. Semail Ophiolite in Oman and the United Arab Emirates, widely considered one of the best exposed ophiolite sequences