Abstract

The El Paso Group in the Franklin Mountains at El Paso, Texas is divided into formations based on gross sedimentation. Four general sediment types are recognized. Type 1 is a massive marine carbonate. Type 2 is composed of alternating marine and mud flat carbonate. Type 3 is composed of pod-shaped bodies of fossiliferous wackestone enclosed in dark packstones and beds of alternating marine carbonate and algal stromatolites. Type 4 is composed of a group of shoreline sediments including tidal channel, intertidal and supratidal sandy carbonates. These shoreline sediments are most useful to determine paleogeography and are the main bases for dividing the El Paso into lithic formations. The formation names from bottom to top are: Bowen formation (Shoreline to marine), Hag Hill (Marine), Chamizal (Shoreline), McKelligon (Marine), Cindy (Shoreline), and Ranger Peak (Marine).

The shoreline sediments are most abundant along the Diablo Arch and extend from the Diablo Arch to a point just west of the Franklin Mountain-San Andres Mountain area. This distribution indicates that the Diablo Arch was topographically high during El Paso time and sloped off to the west into a shallow marine basin in south-central New Mexico.