Late Cretaceous phosphorite deposits have been found at widespread localities in the successful application of an exploration theory based on paleogeographic concepts. Phosphorites are generally deposited in the miogeosyncline or marginal trough adjacent to a craton, where upwelling can occur and where sedimentation is slow. The upwelling oceanic suite of rocks used to identify the favorable setting here includes phosphorite, chert, black shale, and carbonate rock.

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