The Probert Encyclopaedia of Rocks & Minerals

FORMATION

In geology, a formation is any series of rocks referred to a common origin or period, whether they consist of the same or different materials. Geological strata are divided into certain groups of one era of deposition, sometimes of very dissimilar mineralogical character, but inclosing the same fossil species; such as, the Carboniferous, Oolitic, Cretaceous, Silurian, Laurentian, etc.
Research Formation