Field criteria for epigenetic-supergene versus sedimentary-diagenetic silica concentrations in cretaceous limestones,Chihuahua, Mexico

The Cretaceous limestones of Chihuahua, Mexico, exhibit both sedimentary-diagenetic and epigenetic-supergene silica deposits which are distinguished from each other on the basis of texture/fabric/structure, composition, colour, presence or absence of certain other minerals such as malachite and/or hematite, structural relationships with the host-rock, and general paragenetic characteristics with each other; all described herein. The criteria offer a useful composite working model during field work.