- Group (stratigraphy)
A group is in
stratigraphya lithostratigraphic unit, a part of the geologic record or rock column that consists of defined rock strata. Groups are divided into formations (and sometimes into "subgroups") and are sometimes themselves grouped into "supergroups".
Some wellknown groups of northwestern Europe have in the past also been used as units for
chronostratigraphyand geochronology. These are the Rotliegend, Zechstein(both of Permianage), Buntsandstein, Muschelkalk, Keuper( Triassicin age), Lias, Doggerand Malm( Jurassicin age) groups. Because of the confusion this causes, the official geologic timescaleof the ICS does not contain any of these names any longer.
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