Stratigraphy

Stratigraphy, a branch of geology, is basically the study of rock layers and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. The subject was essentially invented and first rigorously applied by William Smith in England in the 1790s and early 1800s. Smith, known as the Father of English Geology, created the first geologic map of England and first recognized the significance of strata or rock layering.

Lithologic stratigraphy

See also: Lithostratigraphy

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Lithostratigraphy, or lithologic stratigraphy, is the most obvious. It deals with the physical lithologic or rock type change both vertically in layering or bedding of varying rock type and laterally reflecting changing environments of deposition, known as facies change. Key elements of stratigraphy involve understanding how certain geometric relationships between rock layers arise and what these geometries mean in terms of depositional environment. One of stratigraphy's basic concepts is codified in the Law of Superposition, which simply states that, in an undeformed stratigraphic sequence, the oldest strata occur at the base of the sequence.

Related Topics:
Lithologic - Facies - Law of Superposition

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Chemostratigraphy is based on the changes in the relative proportions of trace elements and isotopes within and between lithologic units. Carbon and oxygen isotope ratios vary with time and are used to map subtle changes in the paleoenvironment This has led to the specialized field of isotopic stratigraphy.

Related Topics:
Isotope - Carbon - Oxygen - Paleoenvironment

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Cyclostratigraphy documents the often cyclic changes in the relative proportions of minerals, particularly carbonates, and fossil diversity with time, related to changes in palaeoclimates.

Related Topics:
Mineral - Carbonate - Palaeoclimate

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