Una secuencia volcano-plutónica-sedimentaria cretácica en el norte de Sinaloa; ¿un complejo ofiolítico?

Abstract

A volcano-plutonic sequence, associated with pelagic sedimentary rocks containing Albian ammonites, was discovered in the Bacubirito area, northern Sinaloa. The sequence, with its stratigraphic order apparently inverted, seems to have been thrusted from the northwest over phyllonitic green rocks of unknown age. From base to top, the sequence consists of four, mutually conformable units which are: Unit A, limestone and chert with its base strongly tectonized; Unit B, alternating shaly limestone, calcareous shale, chert with radiolarians and interbedded limestone, felsic tuff, siliceous shale, and some volcanogenic graywacke; Unit C, basaltic pillow lavas with a sedimentary interval in its upper part; and Unit D, gabbroic and doleritic rocks, partly metamorphosed under possible suboceanic conditions.