GEOLOGICAL SOCIETY OF AMERICA SPECIAL PAPERS NUMBER 52

GEOLOGY AND PALEONTOLOGY

of THE PERMIAN AREA NORTHWEST OF LAS DELICIAS, SOUTHWESTERN COAHUILA, MEXICO

BY

ROBERT E. KING, CARL O. DUNBAR

PRESTON E. CLOUD, JR., A. K. MILLER

PUBLISHED BY THE SOCIETY February 20, 1944

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Vice-Presidents E. W. BERRY J. B. REESIDE, JH. Baltimore, Md. Washington, D. C. B. S. BUTLER J. F. SCHAIRER Tucson, Ariz. Washington, D. C. Secretary H. R. ALDRICH, 419'West 117 Street, New York, N. Y. Treasurer EDWARD B. MATHEWS, , Baltimore, Md. Councilors (Term expires 1944)

ROLLIN T. CHAMBERLIN . A. I. LEVORSEN W. O. HOTCHKISS Chicago, 111. Tulsa, Olda. Troy, N. Y. (Term expires 1945)

JAMES GILLULY FREDERICK J. ALCOCK K. C. HEALD Los Angeles, Calif. Ottawa, Canada Pittsburgh, Penna. (Term expires 1946)

T. M. BRODERICK CHESTER STOCK WILMOT H. BRADLEY Calumet, Mich. Pasadena, Calif. Washington, D. C.

COMMITTEE ON PUBLICATIONS E. B. KNOPF, Chairman

H. R. ALDRICH KIRK BRYAN A. J. EARDLEY (ex officio)

BOARD OF EDITORS H. R. ALDRICH, Editor-in-Chief AGNES CREAGH, Managing Editor G. ARTHUR COOPER GLENN L. JEPSEN C. F. PARK, JR. A. J. EARDLEY P. B. KING F. J. PETTIJOHN R. C. EMMONS E. S. LARSEN, JR. M. E. WILSON M. KING IIUBBERT O. E. MEINZER F. J. WRIGHT

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GEOLOGY AND PALEONTOLOGY

of THE PERMIAN AREA NORTHWEST OF LAS DELICIAS, SOUTHWESTERN COAHUILA, MEXICO

BY

ROBERT E. KING SUPERIOR OIL COMPANY, CARISBAD, N. MEX. CARL O. DUNBAR PEABODY MUSEUM, , NEW HAVEN, CONN. PRESTON E. CLOUD, JR. U. S. GEOLOGICAL SURVEY, WASHINGTON, D. C. A. K. MILLER STATE UNIVERSITY OF IOWA, IOWA CITY, IOWA

PUBLISHED BY THE SOCIETY February 26, 1944

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WAVERLY PRESS, INC. BALTIMORE, MD.

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BY The following memoir on the Permian rocks and fauna of central Mexico brings to fruit studies in which I have been deeply interested for many years. During the Tenth International Geological Congress in Mexico City in 1906, I listened with fascination to Sir T. W. E. David's paper, On the morphology and evolution of the Australian continent and -particularly in regard to the Cambrian and Permo-Carboniferous glacial climates; and the scratched boulders he exhibited and the pictures he showed convinced me of the existence of glacial climates in the Permian of Australia. My enthusiasm over this spectacular conclusion was rewarded by the gift of three of Professor David's lantern slides, which I displayed for many years to Yale classes in Historical Geology. This incident started an interest in the Permian history which has grown with the years. My active part in Permian studies was delayed, however, until 1924, when I spent the winter at the University of Arizona. The train route westward crossed the Marathon Basin, and I shall never forget the panorama that unfolded from the car window as the Sunset Limited made its way across this plateau which is rimmed along its northern border by the towering cliffs of Permian strata that form the Glass Mountains. Carrying out a resolve made at that time, I stopped on my way east the following spring to visit that grand section and to collect Permian ammonites. In 1926 I was again in the Southwest, this time at the University of Texas, and there I met Philip B. King, then an instructor in the University, who had begun to map the geology of the Glass Mountains the previous summer. The work thus started by King offered an avenue for my growing enthusiasm, and it was soon arranged that Philip and his brother Robert should continue field work in the Glass Mountains with my financial support, and should come to Yale for graduate study looking toward dissertations based on the Permian of that area. In 1927, with additional aid from the Geological Survey of Texas, this work was extended to include a reconnaissance of the Permian of much of West Texas. Meanwhile, Robert King, stimu- lated by Bose's brief account of the discovery of Permian in Mexico, had visited the area about the Hacienda de Las Delicias in 1926 and spent 11 days collecting and making notes on the stratigraphy. The brachiopods then secured were later included in his study of the forms of that group from the Permian of the Glass Mountains. After Robert King's graduation from Yale, I sent him to Coahuila again to make a detailed study of the Permian. From this expedition he brought back four large boxes of fossils and copious notes. A preliminary statement of results was presented in his paper, The Permian of southwestern Coahuila,

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Mexico, in 1934. The study of the faunas, however, has had to wait the co- operation of specialists, and so the final results, presented herewith, have been much delayed. Meanwhile, A. K. Miller and N. D. Newell, con- templating this study, visited the area in 1936 to see the stratigraphy and to augment the collections. In addition, Dunbar, Miller, and Newell all attended the Seventeenth International Geological Congress and partici- pated in the Permian excursion which covered the type area of the system west of the Urals. In the last decade, moreover, a number of monographs have appeared on the stratigraphy and faunas of West Texas and New Mexico that make the sequence there the most useful standard for Permian correlation in this continent if not in the world. These studies provide a background and a basis for interpreting the vast Permian section in central Mexico—an interpretation presented with mature understanding in this paper.

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