1,590 ft. of El Paso sediments at the southern end of the Franklin Mountains, but in the southern San Andres Mountains, near Ash Canyon, the El Paso sediments have thinned to 760 ft. At Hembrillo Canyon the El Paso is 535 ft. thick, whereas to the north at Rhodes Canyon and Sheep Mountain, thicknesses are 305 and 285 ft., respectively. At the northern end of the range, at Mockingbird Gap, the El Paso interval is only 40 ft. thick.The El Paso Group as developed in southern New Mexico, and far West Texas, is continuous with, and a facies expression of, the Ellenburger Group of the outcrop area in central Texas and the subsurface of West Texas. In southwestern New Mexico, the El Paso Group is probably correlative with a portion of the Abrigo Limestone of Arizona. The El Paso Group undoubtedly represents a sedimentary sequence that is generally time-transgressive from west to east. Recent work by Hayes (1975) demonstrates that the Cambro-Ordovician sedimentary patterns seen in this region are illustrative of a series of complex transgressions and regressions, rather than a simple, single transgression.McKelligon Canyon Formation Organic Buildups -Cloud & Barnes (1948, p. 365) were the first to recognize mound structures in the El Paso sediments. They lucidly described the mound-bearing sequence at the southern end of the Franklin Mountains with the statement that "considerable stromatolitic structure is locally evident in the more massive limestone units of interval 15 and Calathium and piloceratid siphuncles are commonly abundant in such beds." Ham & Toomey (1966, pp. 83-84) recognized the "stromatolitic structures" as organic buildups per se and noted that the primary mound contributor was not stromatolites, but a previously unknown colonial organism of possible coelenterate affinity which they discussed in detail and formally described as Pulchrilamina spinosa (Toomey & Ham, 1967). Kelley & Silver (1952, pp. 46-50), in their study of the El Paso sediments of the Caballo Mountains of south-central New Mexico, Opposite: Fig. 5. Outcrop photographs showing channels that have cut through the lightercolored moundrock in the principal mound horizon of the McKelligon Canyon Formation, southern Franklin Mountains, West Texas, (a) This channel is approximately 3 ft. wide at the top of the mound, but narrows to approximately 1 ft. in width near the base of this particular organic buildup, (b) Channel-filling calcarenites (marked-C) on Lechuguilla Mound. The channel-filling is slightly cross-bedded and consists of shell debris and intraclasts.Pulchrilamina (15.1 per cent). The non-skeletal mound components are mudstone (38.1 per cent) and intraclasts (1.8 per cent), without significant variation between succeeding grids.Channel Rock Petrology. -As noted above, channels cutting down into the organic buildup are well developed on the larger mounds. These channels are usually not more than 2 ft. in width, and the deepest one observed to date cuts into moundrock for a depth of 12 ft. The channels are of darker-color and stand...

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The growth history of a phylloid algal biohermal complex of Late Carboniferous (Westphalian) age, outcropping within the La Pasada Formation in northeastern New Mexico, U.S.A., is described in relationship to paleogeography, biostratigraphy, and microfacies associations. This phylloid algal biohermal complex occurs within typical Late Paleozoic cyclical sediments, in a paleogeographic setting along a narrow shelf margin bordering a deep geosynclinal trough to the northwest. Fusulinid foraminifers suggest that the bioherm is of Middle Pennsylvanian (lower Des Moines) age, whereas the overlying sediments are of middle Des Moines age. Both field and petrographic evidence suggest that the bioherm grew upward from relatively shallow water depths, into extremely shallow water where it probably was subaerially exposed. Biohermal growth appears to have been initiated on a ‘hard‐ground’ surface on which lithified clasts and abundant clusters of robust linoproductid brachiopods served as a foundation. Four major microfacies have been identified from the biohermal complex. These are: (I) phylloid algal wackestones‐packstones (mound proper), (2) marly limestones (sediments laterally adjacent to and overlying mound), (3) pelletal‐foraminiferal wackestone (partially capping the mound), and (4) crinoidal packstones‐grainstones (post‐mound). Comparison is made with other surface and subsurface occurrences of phylloid algal complexes of similar age in the southwestern United States.

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Toomey. Donald F. & Cys. John M. 1979 01 15: Community succession in small bioherms of algae and sponges in the Lower Permian of New Mexico. Lethaia, Vol. 12. pp. 65–74. Oslo. ISSN 0024–1164. Small organic mounds outcrop in the Lower Permian Laborcita Formation of the northern Sacramento Mountains of southcentral New Mexico. These small organic structures, up to I'm in height and 3 m in diameter, are unique because they show a well developed vertical biolic zonation. This zonation consists of an initial pioneer community composed of small digitate or plumose colonies of algae and foraminifers (Stage 1). This is followed by a climax community that is first dominated by laminar colonies of the red alga Archaeolithophyllum (Stage 2). and followed by a terminal community composed of minor Archaeolithophyllum, erect heliosponges and brachiopods, dominated by the form Composita (Stage 3). Evidence suggests that the mounds initially developed in shallow water within an open lagoon but. with continued transgression and rapid deepening of the depositional environment. the biota responded to the changes. The organic buildups were killed off by sudden influx of clastics from a tectonically active nearby landmass.