Cretaceous rocks of San Sebastian del Oeste area (Jalisco state, Mexico): Arc deposits between Teloloapan and Alisitos magmatic arcs

A new Lower Cretaceous sedimentary unit is described in western Jalisco state (Mexico). II consists of intercalations of sandstone, sandy limestone, shale and abundant conglomerate. Reefal limestone blocks, which consist of recrystallized matrix and rudists, are involved at the top of the unit and are the product of disruption of closely related reefs. Limestone levels yield Cretaceous microfauna. This unit corresponds to the northern and western extension of sedimentary units of the Cretaceous magmatic are of the Guerrero terrane, and may represent a junction between the southern and northern parts of the Teloloapan-Alisitos magmatic arc.