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The principles of lithostratigraphy were first established by the Danish naturalist, Nicolas Steno, in his 1669 Dissertationis prodromus. [1] A lithostratigraphic unit conforms to the law of superposition, which in its modern form states that in any succession of strata, not disturbed or overturned since deposition, younger rocks lies above older rocks. [2]
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 .
The lithology in Figure 1 & 2 is represented by the cyan, gray/black and yellow blocks of color. Cyan = lime, gray/black = shale and yellow = sand. More yellow represents more sand identified at that depth. The lithology is measured as a percentage of the total sample as visually inspected under a microscope, normally at 10× magnification ...
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.
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".
Lithology is a study of bedrock that occurs at a specific location. The strata may contain fossils which aid in determining how old they are and geologist's understanding of sequence and timing. Geologists group together similar lithologies, and call these larger sedimentary sequence formations .
The older country rock is crosscut by a younger magmatic body. The nature of the intruding body depends on its composition and depth. Common examples are igneous dikes, sills, plutons, and batholiths. Depending on the composition of the magma, the intrusive body may have a complex internal structure which can provide insight into its emplacement.
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.