This chapter summarizes the results of the writer’s work on the paleogeography and facies changes of the Monterrey Formation in the San Hilario area of Baja California, as part of the exploration for phosphate rock prospects carried out in the area by the Mineral Resources Council (Consejo de Recursos Minerales).
Field work from March 1975 to January 1976 covered detailed mapping on l:10,000-scale vertical airphotos of the Monterrey Formation outcrop belt, an area 70 km long and 4 to 5 km wide, together with the upper and lower portions of the respectively under- and overlying Tepetates and San Isidro Formations.
Additional information includes six cross sections along the principal stream beds, eight lithologic columns (scale 1:100), and a stratigraphic correlation table of these columns (1:2,000). As an aid to correlation and future detailed geological work, a collection of Polaroid photographs describes virtually all the Monterrey outcrops exposed at the streambeds, focusing on the section’s geoeconomic features. Part of this material is included here.
Figures & Tables
This volume was developed, produced, and privately printed in Mexico, in Spanish, by the late Ing. G.P. Salas in 1988, as a Mexican contribution to the Geology of North America, with the understanding that it would be translated into English for inclusion in the set. The translation is by Dr. Cecily Petzall of Caracas, Venezuela, with considerable figure translation and redrafting provided by GSA. Salas worked on the volume until his death, with much valuable help from Ing. Hugo Cortez Guzmán. The result is a valuable English-language synthesis of the information available to Salas in the early to mid-1980s about the geothermal, coal, and metal-mining sectors (and some non-metallic resources) of the economic geology of Mexico.