The Type Alisitos Formation (Cretaceous, Aptian - Albian) of Baja California and its Bivalve Fauna

摘要: Abstract The Cretaceous pre-batholithic rocks of the northwestern Peninsular Ranges, predominantly andesitic breccias, tuffs, and interbedded biohermal limestones, are assigned to Alisitos Formation. Formation is intruded by 90 130 million year old plutons Ranges batholith. A stratigraphic thickness approximately 7500 meters evident in type area Formation, near Pacific coast northern Baja California, south Canon Santo Tomas. total exposed on southwestern flank a great north-west-plunging anticline. Fossils occur throughout that section. Eighty-four species molluscan class Bivalvia recorded from 73 fossil localities 10 other nearby localities. Twenty-nine identified with previously described species, 5 them questionably. Twenty-five new. Thirty recognized but not specifically identified. Most identical to, or most closely related relatively well-known Tethyan faunas Europe areas adjacent Mediterranean Sea. invertebrates suggest late Aptian-early Albian age for