Subsurface mapping and structural elements of the top Jurassic in Eastern Mexico (Poza Rica and Tampico Districts)

The configuration of the top Jurassic is based on structural maps derived from oil-well data on the subsurface from the Poza Rica and Tampico regions, eastern Mexico. The maps are based on depths to the contact of the Pimienta and Lower Tamaulipas Formations at the Jurassic-Cretaceous boundary. Lithostratigraphic and chronostratigraphic data are from gamma-ray logs and ammonites, respectively. In the Poza Rica district, the La Mesa syncline was surveyed in the northwest, and the Sultepec homocline in the southeast. The depth to the top Jurassic varies from 2000 to 3700 m in the east and southeast of this region. An elongated area remained emergent during deposition of the Tithonian Pimienta Formation, along the present Gulf of Mexico coast east of Poza Rica, continuing to the southeast of the Tampico area. The Pimienta Formation was eroded in the southeast of Poza Rica along the initial cut of the San Andres paleocanyon. In the Tampico district, the top of the Pimienta Formation is found from 1000 to 3000 m in depth. Two structures, the Tranquitas anticlinorium and the Tanquian anticlinorium, are observed in the northwest and central part of the Tampico district, respectively. Various areas remained emergent during deposition of this formation to the east and southeast of Tampico. They were part of an ancient continent composed of metamorphic and intrusive rocks, and upper Paleozoic continental origin. In the Bejuco region east of the Tampico district, two structures, the Piedra de Cal anticline and the Jabonera syncline, are observed; depth to the top Jurassic varies from 1400 to 3000 m, respectively. In this same region, two areas, Llano de Bustos and La Aguada, remained emergent during the upper Tithonian.