Stratigraphy and Palæogeography
The rocks found outcropping in, and on the margins of, the Tampico Embayment range in age from Middle Cretaceous (Albian-Cenomanian) to Miocene. Beyond the confines of the embayment, properly speaking, Palæozoic and Jurassic rocks are found. Jurassic rocks have been encountered only in wells within the Tampico Embayment itself. Neocomian rocks occur some distance north and southwest of the embayment and in wells near Tampico.
Considerable confusion, practically unavoidable, was evident in the classification of the various Cretaceous and Tertiary rocks in the earlier years of oil field development. These erroneous conceptions regarding the stratigraphy appeared in print from time to time. In a terrain such as the Tampico Embayment, largely covered by tropical or sub-tropical jungle, exposures are not all that can be desired. It has taken the combined labours of a large number of geologists, assisted by palaeontologists, many years to establish a satisfactory explanation of the stratigraphy. Some points are not yet cleared up and attention will be drawn to them in the following pages.