--> ABSTRACT: Depositional Environments and Diagenesis of El Paso Group, Southern Hueco Mountains, Hudspeth County, Texas, by I. J. Aluka; #91030 (2010)

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Depositional Environments and Diagenesis of El Paso Group, Southern Hueco Mountains, Hudspeth County, Texas

I. J. Aluka

The El Paso Group, a predominantly carbonate sequence, overlies the time-transgressive Cambrian-Ordovician Bliss Sandstone, and underlies the Upper Ordovician Montoya Group. The sequence contains three units (in ascending order): lower limestone, middle cherty limestone, and upper dolomite.

The units were deposited in a shelf lagoon with open and restricted circulation, subtidal and intertidal environments. Deposition in these environments is indicated by the presence of land-derived clastics (silt- and sand-size quartz), abundant pellets, micrite, a variety of textures (mudstones to grainstones), algal structures, cross-bedding, and inter-fingering of clastics with limestones due to sedimentary offlap and onlap resulting in clastic progradation west and east from the Diablo platform (the clastic source). The upper unit was, in part, deposited in a supratidal environment, as shown by the presence of abundant dolomite.

In addition, the rocks of the El Paso Group were affected by various diagenetic processes, including dolomitization (supratidal dolomitization and dolomitization through meteoric mixing) and silicification, as exemplified by chert nodules and lenses and the presence of silica in intragranular voids and as intrapelmatozoan infillings. Silica partially replaced gastropods, cephalopods, and pelmatozoan ossicles. Recrystallization (aggrading neomorphism) converted carbonate muds into microspar and sparry calcite. Stylolitization (microstylolites and sutured stylolites) affected the rocks as indicated by the presence of iron oxides along the stylolites. The rocks were also affected by pyritization as shown silicified bioclasts.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.