Jurassic and Lower Cretaceous Stratigraphy and Tectonics of Northeast Mexico

From 1952 to 1956, Pemex conducted a considerable amount of stratigraphic field work in the eastern Sierra Madre and in Laramide folds to the north across the Sabinas Basin. Special thanks and consideration are extended to Pemex for releasing this classic work, in which 76 stratigraphic sections were measured and described, resulting in this significant internal company report by William E. Humphrey and Teodoro Diaz. The former was initially employed by the consulting firm of DeGolyer and MacNaughton; the latter was employed by Pemex. When Humphrey joined Pemex as well, they worked on this project together. The amount of section they studied totaled about 6500 feet (2150 meters). The area they covered extends across seven states of northeastern Mexico, from Chihuahua in the west to Veracruz in the east, and north to the U.S. border. This compilation is particularly valuable because the extensive paleontology done on the measured sections permits widespread correlation of the total Jurassic and Lower Cretaceous with the western Tethyan province in Europe. The complexity caused by intermittent clastic influx into carbonate-producing intrashelf basins is manifest. We took great care to preserve the authors' original text and not to rewrite it; certainly, minor errors of grammar or syntax were corrected to improve the readability of the manuscript. For ease of use by the reader, all of the 76 measured sections have been numbered in the text as follows: MS-1 for Measured Section No. 1, and so forth, as listed in our table. This same system is used to label measured sections that are on the accompanying CD-ROM, containing jpeg file images of all 76 sections. As a partial release of their work, Humphrey published a brief paper with an outline of their interpretations regarding regional stratigraphy and tectonics in the 1956 Transactions of the Gulf Coast Association of Geological Societies. Just as Humphrey and Diaz updated the earlier studies of Burckhardt and Imlay, who worked in the 1930's and 1940’s, this 1956 report at the time furnished several additional stratigraphic sections and an updated understanding of both carbonate and sandstone reservoirs, as well as hydrocarbon source beds in northeastern Mexico.