Geology of Organ Mountains and Southern San Andres Mountains, New Mexico
Total Page：16
File Type：pdf, Size：1020Kb
Geology of Organ Mountains and southern San Andres Mountains, New Mexico COVER—"THE SIERRA DE LOS ORGANOS' OR ORGAN MOUNTAINS are so named from their pinnacled summits and sides which resemble the pipes of an organ. They are of a light gray granite, and rise to the height of 3,000 feet above the river. The defiles are filled with large pines and the more open valley, with live oaks. From the place where we halted and lunched, I took a sketch of these mountains and of the defile through which I had passed." (from Bartlett, 1854) FRONTISPIECE: ORGAN MOUNTAINS AND SOUTHERN JORNADA DEL MUERTO; view to east-southeast (photo courtesy of Rollag and Associates, El Paso, Texas). Memoir 36 New Mexico Bureau of Mines & Mineral Resources A DIVISION OF NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY Geology of Organ Mountains and southern San Andres Mountains, New Mexico by William R. Seager SOCORRO 1981 iv NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY KENNETH W. FORD, President NEW MEXICO BUREAU OF MINES & MINERAL RESOURCES FRANK E. KOTTLOWSKI, Director GEORGE S. AUSTIN, Deputy Director BOARD OF REGENTS Ex Officio Bruce King, Governor of New Mexico Leonard DeLayo, Superintendent of Public Instruction Appointed William G. Abbott, President, 1961-1985, Hobbs Judy Floyd, 1977-1987, Las Cruces Owen Lopez, 1977-1983, Santa Fe Dave Rice, 1972-1983, Carlsbad Steve Torres, Secretary-Treasurer, 1967-1985, Socorro BUREAU STAFF Full Time MARLA D. ADKINS, Assistant Editor DAVID W. LOVE, Environmental Geologist ORIN J. ANDERSON, Geologist WESS MAULDIN, Driller's Helper RUBEN ARCHULETA, Technician I VIRGINIA McLEMORE, Geologist KEVIN C. BAKER, Field Researcher LYNNE McNEIL, Staff Secretary ROBERT A. BIEBERMAN, Senior Petrol. Geologist NORMA J. MEEKS, Department Secretary STEVE BLODGETT, Assistant Editor DAVID MENZIE, Geologist LYNN A. BRANDVOLD, Chemist ARLEEN MONTOYA, Librarian/Typist JAMES C. BRANNAN, Draftsperson TERESA A. MUELLER, Draftsperson CORALE BRIERLEY, Chemical Microbiologist SUE NESS, Receptionist BRENDA R. BROADWELL, Assoc. Lab Geoscientist ROBERT M. NORTH, Mineralogist FRANK CAMPBELL, Coal Geologist KEITH O'BRIEN, Hydrologist RICHARD CHAMBERLIN, Economic Geologist JOANNE C. OSBURN, Coal Geologist CHARLES E. CHAPIN, Senior Geologist GLENN R. OSBURN, Volcanologist JEANETTE CHAVEZ, Admin. Secretary I JOAN C. PENDLETON, Associate Editor RICHARD R. CHAVEZ, Assistant Head, Petroleum BARBARA R. POPP, Lab. Biotechnologist RUBEN A. CRESPIN, Laboratory Technician II ROBERT QUICK, Driller LOIS M. DEVLIN, Director, Bus.—Pub. Office MARSHALL A. REITER, Senior Geophysicist KATHY C. EDEN, Editorial Technician JACQUES R. RENAULT, Senior Geologist ROBERT W. EVELETH, Mining Engineer JAMES M. ROBERTSON, Mining Geologist K. BABETTE FARIS, X-ray Lab. Manager GRETCHEN H. ROYBAL, Coal Geologist ROUSSEAU H. FLOWER, Sr. Emeritus Paleontologist AMY SHACKLETT, Asst. Lab Biotechnologist STEPHEN J. FROST, Coal Geologist JACKIE H. SMITH, Laboratory Technician IV JOHN W. HAWLEY, Environmental Geologist DALE STALEY, Driller's Helper DANA M. HELJESON, Editorial Technician WILLIAM J. STONE, Hydrogeologist STEPHEN C. HOOK, Paleontologist SAMUEL THOMPSON III, Petroleum Geologist MELVIN JENNINGS, Metallurgist JUDY M. VAIZA, Executive Secretary BARBARA J. JOHNSON, Staff Secretary DEBRA VETTERMAN, Draftsperson ROBERT W. KELLEY, Editor & Geologist ROBERT H. WEBER, Senior Geologist SHERRY A. KRUKOWSKI, Record Manager DONALD WOLBERG, Vertebrate Paleontologist MARK LOGSDON, Economic Geologist MICHAEL W. WOOLDRIDGE, Scientific Illustrator ANNABELLE LOPEZ, Clerk Typist Part Time CHRISTINA L. BALK, Geologist BEVERLY OHLINE, Newswriter, Information Services HOWARD B. NICKELSON, Coal Geologist THOMAS E. ZIMMERMAN, Chief Security Officer Graduate Students BRUCE W. BAKER ROBERTA EGGLESTON TOM MCANULTY INDIRA BALKISSOON TED EGGLESTON LAWRENCE NELSON GERRY W. CLARKSON ADRIAN HUNT JOHN YOUNG Plus about 50 undergraduate assistants First Printing, 1981 Published by Authority of State of New Mexico, NMSA 1953 Sec. 63-1-4 Printed by University of New Mexico Printing Plant, May, 1981 Available from New Mexico Bureau of Mines & Mineral Resources, Socorro, NM 87801 Price $20.00 v Preface Forty-five years have passed since Sir Kingsley Charles swarms of gnats and small flies infest every bush and rocky crevice along the higher peaks. They can be set into motion just by a Dunham wrote Geology of the Organ Mountains, yet his account ' of the geology of the range is as timely today as it was in 1935 and persons presence and they seem indifferent to insect repellent. his writing style is as much a pleasure to read now as then. His They come at you in clouds, and shortly your ears, eyes, nose, and description of the ore deposits and his petrographic work with the mouth are full. Retreat from the ridge top is the only effective igneous and metamorphic rocks are not likely to be improved upon antidote. At least once in each summer swarms of ladybugs also for many years. Besides being of interest for the local geology, the take over the highest peaks, rendering the rocks orange by their book is also of general value because Dunham carefully martials numbers. evidence from the Organs on such topics as the emplacement of Satisfying experiences far outweigh the disagreeable ones, batholiths, structural and lithologic controls of orebodies, however. Reaching the summit of the range and looking out over metamorphic mineral equilibrium assemblages, and alteration the vast stretches of canyons and ridges below to the broad desert processes. Geology of the Organ Mountains has justly become a beyond is always exhilarating. To come upon unexpected springs classic in the geology of New Mexico. or groves of aspen or Douglas fir is a pleasant surprise and a walk The quality of Dunham's work is such that few additional through a flattish stretch of canyon floor shaded by high Ponderosa geologic studies in the Organ district were published between 1935 pines or ancient juniper trees is a pleasure. Golden eagles and 1980, although many individuals and mining companies used swooping up a canyon toward you, bighorn rams or huge deer Dunham's report as a basis for mineral exploration during the same clashing and locking horns in front of you, newly born, unafraid period. The present study was undertaken partly to integrate the fawns motionless beneath a bush at your side—these are all results of recent exploration activity, geophysical studies, and occasional rewards which more than compensate for the bugs and radiometric dating into Dunham's geologic framework and partly to for the spells of disagreeable weather. Of course, over the long run, show geologic details on greatly improved 7½-min topographic the daily variety for a geologist working in the Organ or San base maps. Additional objectives were: 1) to map previously Andres Mountains is provided by the geology itself. Even if there unmapped portions of the northern Organ and southern San Andres were nothing else to make field work a pleasure, the geologic Mountains that contain features of structural significance, 2) to relations among rocks and structures are sufficiently challenging describe sections of Paleozoic rocks that had not been described in and revealing to insure boredom as an impossibility. Putting detail or subdivided into up-to-date stratigraphic units, and finally together a picture of the geologic relationships and history of the 3) to investigate relationships between the Organ batholith and range can be likened to assembling a huge, complex puzzle with volcanic rocks in the southern Organ range, which recently were half (or more?) of the pieces missing. For a geologist the best part shown to be of the same age. During the course of mapping and of the field experience—aspen, eagles, and fawns from many discussions with John Hawley, I realized that there notwithstanding—is putting that puzzle together. were many kinds and ages of alluvial deposits mantling the edge of ACKNOWLEDGMENTS-Many people have directly or indi- the mountains and that they were related to the general geomorphic rectly contributed to this effort through their advice, critical evolution of the range and to repeated movements on the boundary readings of the text, or with other kinds of help and cooperation. I fault along its eastern margin. Another objective in this study was thank Sam Thompson III, Pete Lipman, Dick Chamberlin, Jerry to distinguish among these deposits and relate them to the Mueller, John Hawley, Tom Giordano, Charles Chapin, Glenn R. Quaternary erosional and faulting history of the range. Osburn, and D. D. Seager for reviewing various chapters of the Field work was done between 1975 and 1978, mostly during the book, Charles B. Hunt for reviewing an early version of the summer months. Working in the summer in the Organ Mountains manuscript and for his help with fig. 83, and especially Vincent C. can be exhilarating, discouraging, rewarding, frightening, or Kelley for reviewing the manuscript in its entirety. The New satisfying, and is always different from day to day. Aside from the Mexico Bureau of Mines and Mineral Resources funded chemical steep slopes, rocky precipices, and occasional rattlesnakes (mostly analyses, and I thank Lynn Brandvold for running those analyses. black-tailed rattlers), nature uses other ways to insure that geologic The University of Arizona geochronology laboratory also provided information does not come easily from the mountains. Many of the some chemical analyses, a radiometric date, and computer analysis higher slopes are covered