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| | Cretaceous Fossils: West Texas Rock Correlation Chart |
 | | It dropped off into the Chihuahua Basin to the west, and was bordered periodically by a series of barrier reefs (Stuart City Trend) to the south and to the east (Bebout, et al., 1974, Powell, 1965; Morán–Zenteno, 1994). |
 | | Thus, going from west to east: a) the uppermost Chispa Summit is lowermost Santonian in age (Prionocycloceras gabrielense Young zone), b) the uppermost Ojinaga/basal San Carlos is lowermost Campanian in age (Submortoniceras tequesquitensis Young zone), and c) the uppermost Pen Formation is early Campanian in age (Menabites (Delawarella) delawarensis (Morton) zone). |
 | | Bureau of Economic Geology, University of Texas at Austin Geological Atlas of Texas: Del Rio, Emory Peak–Presidio, Fort Stockton, Marfa, Pecos, Sonora, and Van Horn–El Paso Sheets. |
| www.cretaceousfossils.com /stratigraphy/stratigraphic_correlation_pv.htm (2392 words) |
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