At the Guadalupe River Gorge area in northern Baja California, five Ordovician-related allochthonous blocks, consisting of alternating metaquartzarenite and carbonate with subordinate hornfels, metasubarkoses and chert rests upon metasiltstones, metasandstones, metamudshales, phylli tes, and cherts of Mesozoic (?) age v:li thin a 4 square kilometer area. These distinct suites are separated by melange terrains which contain randomly oriented allochthonderived blocks within an argillaceous matrix. All the metasediments are intruded by granitics and dikes of the Cretaceous Peninsular Ranges batholith. The metasrdi· ments possess a metamorphic grade no higher than greenschist :t:acies and exhibit a strong westward dipping foliation within the argillaceous units. The entire terrain at Guadalupe has been lithologically correlated to a strikingly similar terrain at San Marcos, 6kms to the north, which has previously been lithologically and paleontologically correlated to the Ordovician Valmy Formation of north central Nevada. Exsisting models suggest that roughly 800km of south-wardmovement along a proposed Triassic to Jurassic "megashear" followed by the northward movement of the Neogene San Andreas Fault would place Valmy equivalent rocks at the general location of Guadalupe and San Marcos.
