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 .
5-678: The Ancholme Group is a geologic group in England . It preserves fossils dating back to the Jurassic period . It has previously been referred to as the Ancholme Clay Group. The group consists of predominantly grey, marine mudstone and silty mudstone with beds of argillaceous limestone nodules. In parts of its range it interfingers with the Corallian Group , which predominantly consists of coralliferous limestones. This article about
10-523: A specific stratigraphic formation in the United Kingdom is a stub . You can help Misplaced Pages by expanding it . This article related to the Jurassic period is a stub . You can help Misplaced Pages by expanding it . This England -related article 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
15-571: 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
20-820: 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
25-460: 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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