There are various methods and softwares available for correlating strata. The principle behind all correlations is that because of extinctions, radiations, morphological changes and speciation, each taxa will only be representative of a certain time period. Zoning of these events in series of wells allows the biostratigrapher to establish marker beds. These marker beds are then correlated between wells. This method of correlation is one of the best methods of sub surface mapping available.

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