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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 .
Petrology (from Ancient Greek πέτρος (pétros) ' rock ' and -λογία ' study of ') is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. [1] Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. [2]
petrology The branch of geology that studies the origin, composition, distribution, and structure of rocks. phenoclast A large, conspicuous fragment in sediment or sedimentary rock composed of various sizes of material. phenocryst A relatively large crystal in an igneous rock. phyllite
Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneous or sedimentary relating to how the rock was formed. Sedimentary layers are laid down by deposition of sediment associated with weathering processes, decaying organic matter (biogenic) or through chemical precipitation.
The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects. Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks.
Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The classification of rocks is based on the information acquired during the petrographic analysis.
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.