Field relationships and paleontologic data in the Covelo-Laytonville area suggest (1) mélanges can be mapped as discrete stratigraphic units on the basis of matrix and type of included block; (2) some of the mélange units are in depositional contact with other Franciscan units and represent olistostrome deposits; (3) neither the type of included block nor the style of deformation observed in the matrix provides a basis for assuming a tectonic emplacement for these mélanges; (4) the process of mélange formation, at least locally, involved the mixing of rocks of different composition and age; and (5) in the Covelo-Laytonville area, mélange formation was active during or after Middle Cretaceous (Albian-Cenomanian) time.

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