Stratigraphical Classification
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概要
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Two distinct categories of stratigraphic units are to be recognized, among which a unit of either category has no direct bearing on definition of units belonging to the other., This is because they are defined entirely by different criteria., Stratigraphic units defined solely by physical characters, including contained organic remains, include : (1) formation as the fundamental unit ; (2) subdivisions of formation, such as member, lentil, tongue, and bed ; and (3) aggregations of formations, called groups., These units are designated by a geographic name (treated as a noun) combined with a lithologic or classificatory term belonging to this category., Stratigraphic units defined solely on the basis of geologic time concepts include any and all sorts of rocks formed during a specified part of geologic time., Such units are (1) stage ; which may be considered as the fundamental unit of this category ; (2) series ; (3) system ; and (4) erathem., These units are designated by an adjectival name, generally of geographic origin, combined with a classification term belonging to this category., Geochronologic units, which comprise divisions of time, are not stratigraphical units, althouth they are defined by stratigraphical observations., Such units are (1)age, (2)epoch, (3)period, and (4)era., These units are designed by adjectival name identical to that of the stage, series, system, or erathem, which represents the geochronologic unit.,
- 日本地質学会の論文
- 1950-05-25