In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into supergroups .
5-720: The Pease River Group is a geologic group in Texas Red Beds . It preserves fossils dating back to the Permian period , including some of the geologically most recent continental and coastal vertebrates of the Permian in North America. These are preserved in the San Angelo Formation, which is probably of early Roadian age. They include several fragmentary fossils that Everett C. Olson interpreted as
10-586: The Glenwoody Formation , other strata (particularly in the lower part of the group) remain undivided into formations. Some well known groups of northwestern Europe have in the past also been used as units for chronostratigraphy and geochronology . These are the Rotliegend and Zechstein (both of Permian age); Buntsandstein , Muschelkalk , and Keuper ( Triassic in age); Lias , Dogger , and Malm ( Jurassic in age) groups. Because of
15-866: The Wingate Sandstone , the Moenave Formation , the Kayenta Formation , and the Navajo Sandstone . Each of the formations can be distinguished from its neighbor by its lithology , but all were deposited in the same vast erg . Not all these formations are present in all areas where the Glen Canyon Group is present. Another example of a group is the Vadito Group of northern New Mexico . Although many of its strata have been divided into formations, such as
20-525: The earliest therapsids , an interpretation that has not been widely accepted. This article about a specific stratigraphic formation in Texas is a stub . You can help Misplaced Pages by expanding it . This article related to the Permian period is a stub . You can help Misplaced Pages by expanding it . Group (geology) Groups are useful for showing relationships between formations, and they are also useful for small-scale mapping or for studying
25-468: The stratigraphy of large regions. Geologists exploring a new area have sometimes defined groups when they believe the strata within the groups can be divided into formations during subsequent investigations of the area. It is possible for only some of the strata making up a group to be divided into formations. An example of a group is the Glen Canyon Group , which includes (in ascending order)
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