Geology of the Mockingbird Gap Quadrangle, Lincoln and Socorro Counties New Mexico GEOLOGICAL SURVEY PROFESSIONAL PAPER 594-J Geology of the Mockingbird Gap Quadrangle, Lincoln and Socorro Counties New Mexico By GEORGE 0. BACHMAN SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 594-J A summary of the stratigraphy, geologic structure, and regional geologic setting of the southern part of the Oscura Mountains and the northern part of the San Andres Mountains UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1968 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract __________________________________________ _ J1 Stratigraphy-Continued Introduction ______________________________________ _ 1 Permian rocks-Continued Location and accessibility------- ________________ _ 1 Abo Formation____________ ---- __ --- __ ------ J28 Physical features ______________________________ _ 1 Yeso Formation ______ -------- __ ---------- __ 29 Previous investigations _________________________ _ 3 ~eseta Blanca Sandstone ~ember _______ _ 30 ~ethods ofwork ______________________________ _ 3 Upper part of the Yeso Formation_______ _ 30 Acknowledgments ______________________________ _ 4 Interpretation of sedimentation and stratigraphy of Precambrian rocks _________________________________ _ 4 Pennsylvanian and Early Permian age __________ _ 31 Stratigraphy ______________________________________ _ 4 Cretaceous rooks __________ --______________ ---_-- 34 Upper Cambrian and Lower Ordovician rocks- Igneous rocks of probable Tertiary age ___________ _ 34 Bliss Sandstone ______________________________ _ 5 Quaternary deposits ________________________ ----- 34 Lower Ordovician rocks-El Paso Dolomite_______ _ 9 GeomorphologY-----------------------------------­ 35 ~iddle Ordovician rocks-Upham Dolomite ~em- Pediments------------------------------------- 35 ber of the ~ontoya Dolomite _________________ _ 14 Alluvial fans ____________ ---- __ ----------------- 35 Devonian and ~ississippian rocks _______________ _ 16 Arroyos (channel trenches)-------- ____ ----------- 35 Interpretation of pre-Pennsylvanian Paleozoic stra- Geologic structure ____________ - _- __ ----------------- 36 tigraphy and sedimentation,___________________ _ 16 Economic geology ____________ - ____ ----------------- 38 Pennsylvanian rocks ___________________________ _ 19 Copper deposits ___________ -- _____ -------------- 38 Sandia Formation __________________________ _ 20 Estey district ________________________ -_-_-- 38 ~adera Formation _________________________ _ 21 Other copper prospects_- __ ------------------ 40 Lower member ________________________ _ 21 Origin of red-bed copper minerals ___________ -- 40 Upper member________________________ _ 22 Oil and gas possibilities _________________________ _ 41 Permian rocks _________________________________ _ 25 Construction materials ____ ------- ____ ----------- 41 Bursum Formation _________________________ _ 25 References cited _________ --- ______ ------------------ 41 ILLUSTRATIONS Page PLATE 1. Geologic map and section of the ~ockingbird Gap quadrangle, New ~exico ____________________________ In pocket 2. Graphic sections of Pennsylvanian formations in the ~ockingbird Gap quadrangle, New Mexico, and stratigraphic relationships of pre-Pennsylvanian Paleozoic formations __________________________________ --------- In pocket 3. Graphic sections of Permian formations, southern Oscura ~ountains, Lincoln and Socorro Counties, N. Mex_ In pocket FIGURE 1. Index map of south-central New ~exico showing location of ~ockingbird Gap quadrangle___________________ J2 2. Photographs showing southern part of Oscura ~ountains ____________________________________ ------------ 6 3. Photographs showing primary sedimentary structures in lower Paleozoic rocks______________________________ 8 4. Graphic sections of pre-Pennsylvanian Paleozoic formations __________________________________ ------------ 10 5. Photograph showing lower Paleozoic rocks in southern Oscura Mountains ______________________ ------------ 14 6. Photomicrograph of colonial algae in the Bursum Formation_____________________________________________ 27 7. Index map of New Mexico showing relative positions of major tectonic elements during Pennsylvanian and Early Permian time__________________________________________________________________________________ 32 8. Interpretive diagram showing relationships of Paleozoic rocks in southern Oscura Mountains _____ ---_-------- 33 9. Photographic relief map of south-central New Mexico __ ~------------------------------------------------ 37 10. Diagrammatic cross section in Mockingbird Gap Hills___________________________________________________ 39 TABLE Page TABLE 1. Summary of rock formations exposed in the Mockingbird Gap quadrangle ________________ - __ -_------------ J5 Til SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGY OF THE MOCKINGBIRD GAP QUADRANGLE, LINCOLN AND SOCORRO COUNTIES NEW MEXICO By GEORGE 0. BACHMAN ABSTRACT Northward wedging OUit Olf pre-PeniD.ISIYlvnnian Paleozoic Sltlrarta The Mockingbird Gap 15-minute quadrangle comprises about is attributed to repeated epeirogenic movement along a generally 250 square miles in eastern Socorro and western Lincoln Coun­ east-west hinge line in the approximate latitude of the present­ ties, N.Mex. The quadrangle is about 50 miles southeast of the day Oscura Mountains. The hinge line was a broad zone of town of Socorro. crustal weakness ·along which the crust of the earth was tilted The southern Oscura Mountains and the northern extremity down t!O the south or was slightly uplifted to the north. of the San Andres Mountains are within the report area. The Tertiary tectonic activity occurred in at least two stages. The Mockingbird Gap Hills are located in the quadrangle northeast earlier stage was probably characterized by north-south elongate of the San Andres Mountains, about midway between the north­ doming of orogenic proportions accompanied by both high- and ern termination of that range and the Oscura Mountains. Mock­ low-angle normal faulting. The second stage was characterized ingbird Gap, from which the quadrangle derives its name, is the by generally northwesterly trending normal faulting which divide between the San Andres Mountains and the Mockingbird caused the present-day block-faulted mountains. Gap Hills. The geology described in this report is primarily that of the INTRODUCTION bedrock of the uplands. The intervening areas are covered to a LOCATION AND ACCESSIBILITY large extent by alluvial fans. The rock formations exposed in the quadrangle range in age from Precambrian to Quaternary. The Mockingbird Gap 15-minute quadrangle com­ The oldest rock exposed is granite of Precambrian age. The Bliss prises about 250 square miles in eastern Socorro and Sandstone, assigned to Late Cambrian and Early Ordovician western Lincoln Counties, N.Mex. (fig.1); it is bounded ages, rests on the granite in the northern San Andres and the southern Oscura Mountains ; it wedges out northward in the by lat 33°30' and 33°45' N. and long 106°15' and 106° Oscura Mountains. The El Paso Dolomite of Early Ordovician 30' W. The quadrangle is at the north end of Tularosa age rests with apparent conformity on the Bliss Sandstone, has Valley, an alluvium-filled basin that has interior drain­ a distribution similar to that of the Bliss in the quadrangle, and age and is about 100 miles long and as much as 40 miles wedges out to the north in the Oscura Mountains. The Upham wide. The valley is bounded on the east, from north to Dolomite Member of the Montoya Dolomite of Middle Ordovician age disconformably overlies the El Paso. The Montoya wedges south, by Sierra Blanca, the Sacra.mento Mountains, out northward in the southern part of the Oscura Mountains. and Otero Mesa, and on the west by the San Andres, Rocks of Silurian, Devonian, and Mississippian ages are not Organ, and San Augustin Mountains. The valley's north represented in the report area, but rocks of Devonian and Mis­ boundary is less definite, but it includes the Mocking­ sissippian ages are present and wedge out in the San Andres bird Gap Hills, Oscura Mountains, and the Phillips Mountains about 1 mile south of the quadrangle. Rocks of Pennsylvanian age lap across the Montoya, El Paso, and Bliss Hills. Its south boundary is also indefinite but is re­ Formati'Ons and rest on Precambrian granite in the Oscura garded as a low generally east trending drainage divide Mountains in the northeastern part of the report area. near the New Mexico-Texas boundary. Pennsylvanian SJtJrata coDJtruin the fusulinid zones of Fusuli­ neZla, Fusulina, and Triticites. Tbe rocks are divided into a PHYSICAL FEATURES lower clastic formation, the Sandia, and atn. UIPver formation, We Madera. The Madera Formation consd.srts of two informal The Mockingbird Gap quadrangle is within the con­ members: A lower, dominantly calcareous sequence of rocks fines of White Sands Missile Range. There are no in­ and an upper, cla.stJic sequence. habitants in t:he quadrangle, ·and access is prohibited Permian rocks include, in ascending order, the Bursum, Abo, to the general public. One main roa:d traverses the and Yeso Formations. The Bursum Formation, consisting of interbedded marine limestone and red beds, interfingers with the southwestern part of the quadrangle through Mocking­