STRATIGRAPHY OF EARLY ORDOVICIAN EL PASO GROUP OF THE SOUTHERN HUECO MOUNTAINS, HUDSPETH COUNTY, TEXAS.
Abstract
The Early Ordovician El Paso Group of the southern Hueco Mountains, Hudspeth County, Texas, crops out over an area of about 57 km('2) (22 mi('2)) at longitude 105(DEGREES) 53' 30" and 106(DEGREES) 1' 30" W and latitude 31(DEGREES) 40' 15" and 31(DEGREES) 47' 30" N. It is divided into three informal units (oldest to youngest): lower, middle and upper. The lower unit contains the lower calcareous sandstone member and an overlying sandy limestone member. The middle unit is cherty limestone. The upper unit contains two members: sandy dolomite and an upper silty dolomite.
The calcareous sandstone member is 36 m (118 ft) thick and conformably overlies the Bliss Sandstone. It is thin- to medium-bedded, grayish-orange-pink to pale-blue, glauconitic, dolomitic, and siliciclastic sandstone. The calcareous sandstone member was deposited in subtidal and intertidal environments and is of Early Early Ordovician age.
The sandy limestone member of the lower unit (35 m {115 ft} thick) conformably overlies the calcareous sandstone member. It is light brownish-gray to light bluish-gray in color, medium- to thick-bedded, and sparsely glauconitic. It is primarily a sandy wackestone, packstone, pelsparite, and pelmicrite that was deposited in a shelf lagoon which at various times had an open circulation, restricted circulation, and tidal flat development. The sandy limestone member is of Middle Early Ordovician age.
The middle unit (209 m {690 ft} thick) is a light olive-gray to medium light gray, very thick-bedded to massive cherty limestone. It is primarily a silty and sandy pelsparite, pelmicrite, wackestone, and grainstone sequence which was deposited in restricted circulation in shelf, shelf lagoon with open circulation, and tidal flat environments. The middle unit contains Lecanospira, Hormotoma, and Maclurites, gastropods, brachiopods, and cephalopod siphuncles (in part assignable to Mcqueenoceras and Piloceras spp.) and is of Early Late Early Ordovician age.
The sandy dolomite member of the upper unit (47 m {155 ft} thick), disconformably overlies the cherty limestone member. It is pale yellowish-brown to light olive-gray and medium- to very thick-bedded. It is a typical sandy, dolomitic wackestone, pelsparite, and grainstone sequence which was deposited in shelf lagoon with open circulation, restricted circulation in shelf, and tidal flat environments. The sandy dolomite member is of Middle Early Ordovician age. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI
Subject Area
Geology
Recommended Citation
ALUKA, MADUEGBOAKA INNOCENT JUDE, "STRATIGRAPHY OF EARLY ORDOVICIAN EL PASO GROUP OF THE SOUTHERN HUECO MOUNTAINS, HUDSPETH COUNTY, TEXAS." (1984). ETD Collection for University of Texas, El Paso. AAI8420094.
https://scholarworks.utep.edu/dissertations/AAI8420094