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Stratigraphy is a branch of geology concerned with the study of rock layers and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks . Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy ...
Stratigraphy is a key concept to modern archaeological theory and practice. Modern excavation techniques are based on stratigraphic principles. The concept derives from the geological use of the idea that sedimentation takes place according to uniform principles.
A stratigraphic column is a representation used in geology and its subfield of stratigraphy to describe the vertical location of rock units in a particular area. A typical stratigraphic column shows a sequence of sedimentary rocks , with the oldest rocks on the bottom and the youngest on top.
The golden spikes on geologic timescales represent internationally agreed upon references for the boundaries of the stages in the geologic timescale. These contacts have been identified by the International Commission on Stratigraphy and they are known as GSSPs, or global boundary stratotype section and points. Some of these boundary points are ...
The long history of sedimentary deposition in the Williston Basin included deposition of rocks well suited to serve as hydrocarbon source and reservoir rocks.The basin's oil and gas fields are found in a wide range of geologic ages, as indicated by the generalized stratigraphic column.
Customarily, only distinctive beds, i.e. key beds, marker beds, that are particularly useful for stratigraphic purposes are given proper names and considered formal lithostratigraphic units. [18] [19] In case of volcanic rocks, the lithostratigraphic unit equivalent to a bed is a flow. A flow is “...a discrete, extrusive, volcanic rock body ...
Stratigraphic sections can also be used to locate areas for water, coal, and hydrocarbon extraction, particularly petroleum and natural gas. A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundaries of stages on the geologic time scale. [5]
An abundance zone is a stratigraphic interval in which the abundance of a particular taxon (or group of taxa) is significantly greater than seen in neighbouring parts of the succession. [6] [7] An interval zone is a stratigraphic interval whose top and base are defined by horizons that mark the first or last occurrence of two different taxa. [6 ...