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Geology of the Middle Canyon, Whetstone Mountains, Cochise County, Arizona Item Type text; Thesis-Reproduction (electronic); maps Authors Burnette, Charles Richard, 1929- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 23/09/2021 19:55:22 Link to Item http://hdl.handle.net/10150/553905 GEOLOGY OF THE MIDDLE CANYON, WHETSTONE MOUNTAINS, COCHISE COUNTY, ARIZONA &*■ . by Charles R. Burnette A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY In Partial FulfiUment of the Requirements For the Degree of MASTER OF SCIENCE In the Graduate College UNIVERSITY OF ARIZONA 1957 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfillment of re­ quirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to bor­ rowers under rules of the Library. Brief quotations from this thesis are allowable without spe­ cial permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in their judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below: w, / f r ? JOHN F. LANCE Date Professor of Paleontology GEOLOGY OF THE MIDDLE CANYON, WHETSTOfNE MOUNTAINS, COCHISE COUNTY, ARIZONA by Charles R. Burnette ABSTRACT Middle Canyon, in the Whetstone Mountains southwest of Benson, Arizona, contains Paleozoic sedimentary rocks lying un- conformably on the Precambrian Pinal schist. The sedimentary rocks dip to the southwest and are cut by two sets of high-angle faults, a major set with northeast trend and a minor set with north­ west trend. The Pinal schist is intruded by Precambrian Whetstone granite and related pegmatite dikes. The Paleozoic rocks mapped range in age from Cambrian to Pennsylvanian. Quartzites, conglomerates, and shales predominate in the lower part of the section. The upper Cambrian and younger rocks are chiefly limestones. A trilobite from the Abrigo limestone is identified by Stoyanow as a new species. ii The Lonestar fluorite mine and one tungsten prospect contain the only known minerals of economic value. Mapping of the Lonestar mine shows localization of the fluorite vein along a shear zone in the Pinal schist. TABLE OF CONTENTS Page INTRODUCTION............................................................................... 1 Location of Area Topography Acknowledgments ^ CO c o STRATIGRAPHY AND PETROLOGY .................................. 6 General Statement .......................................................................... 6 Sedimentary Rocks ................................................................... 7 Cambrian System ................................................................. 7 Bolsa Quartzite ................................................................... 7 Cochise Formation ............................................. 9 Abrigo Limestone ........................................................... 10 Rincon Limestone ................................. 11 Devonian System ..................................................................... 11 Martin Limestone ................................................ 11 Mississippian System ............................................................ 12 - ■ .. ' ; Escabrosa Limestone ....................................................... 12 Pennsylvanian System ..................................................... 13 Naco Lim estone.......................................... 13 Quaternary Alluvium ............................................... 13 Igneous Rocks .................................................... 14 Whetstone granite ........................................................... 14 Dacite ............................................................... 14 iv Page Metamorphic R o ck s................................................................... 15 Pinal Schist ........................... 15 PALEONTOLOGY _______ 17 , Cambrian .................... 18 Devonian ........ ...................................................... .................... ‘ 19 Mississippian........................................................ 19 STRUCTURAL GEOLOGY ........ ................... ............ 20 General Statement ..................... 20 Middle Canyon F a u lt........ ......................... 21 Benson Fault ........................................................ 21 Minor Faults ............... 22 Folds ........... 23 ECONOMIC GEOLOGY........................................................ 25 Lonestar Fluorite Mine ........................................................... 25 Geology ................................. 26 Mineralogy ............................................................................. 27 Economic Importance ............... 28 Tungsten Prospects........................... 28 GEOMORPHOLOGY................................................................ 31 APPENDIX A - DESCRIPTION OF MEASURED SECTIONS .. 35 REFERENCES CITED ........................... 55 LIST OF FIGURES .... Figure . Page 1 Location map of the Middle .Canyon, Whetstone. Mountains ................. 3 2 Structural geology and geomorphology of the Middle Canyon, Whetstone Mountains ...................... ................ in pocket v LIST OF PLATES Plate Page I Geologic map of the Middle Canyon area. Whetstone M ountains............................................................................ in pocket n Detailed section of the Middle Canyon ............... in pocket m Geologic map of the . 90-foot level* Lonestar Mine, "Middle Canyon ................ 1......... ..................................... in pocket IV Geologic map of the 150-foot level, Lonestar Mine, Middle Canyon ............................... ............... .. in pocket V Geologic map of the 2 50-foot level, Lonestar Mine, Middle Canyon ............................................... ......... in pocket VI Cambrian Trilobite, between Blountia alethes and andreas Walcott ........................................... 45 VII Middle Canyon, Whetstone Mountains ......................... 46 Vm Intrusive relationships and contact metamorphic effects of Cretaceous d a c ite ................................................ 47 IX Flat pebble conglomerate in the Abrigo formation and pre-Bolsa channeling ..................................... 48 X Sedimentary and intrusive contacts in Cambrian formations ............................................................................... 49 XI Views of the Benson fault ....................................................... 50 XII Views of the Bolsa quartzite cliff........................................... 51 XTTT Views of intrusive and fault contacts in Middle Canyon ............................................................. 52 XTV Paleozoic formations in Middle Canyon ............................. 53 XV Folds in Middle C anyon.......................................... 54 vi INTRODUCTION The Middle Canyon area is located on the east side of the Whetstone Mountains, nine miles southwest of Benson, Cochise County, Arizona, Middle Canyon has a nearly complete Paleozoic section overlying Precambrian igneous and metamorphic rocks, Precambrian and Paleozoic rocks to the top of the Mississippian Escabrosa limestone were mapped. The geology was plotted on a map of scale 1:31,680 modi­ fied from a U. 8. Forest Service map of the Whetstone Mountains. Minor changes were made in the field to conform with drainage and topography. Aerial photographs loaned by the Soil Conservation Service aided in the study. Underground mine maps of the Lonestar mine were made with the assistance of Gene Thompson of the University of Arizona. The field work was started in the summer of 1952 and was carried on through the school year of 1952-53. The laboratory work necessary for this thesis was completed before the author left the University of Arizona for the U. S. Air Force. „ Most of the manuscript was written while the author was on active duty with the Air Force. 2 Location of Area Middle Canyon is located on the eastern slope of the Whetstone Mountains in Cochise and Pima Counties, Arizona (Fig. 1). The area is bordered on the south by French Joe Canyon and on the north by Cain Canyon, both of which trend approximately east-west. To the west of Middle Canyon are French Joe Canyon and Apache Peak. The area mapped occupies sections 26, 27, 28, 33, 34, and 35, and the western half of section 25 of T. 18 S., R. 19 E., Gila and Salt River Baseline and Meridian. It is entirely within the Coronado National Forest and is 70 miles southeast of Tucson, Arizona. Middle Canyon can be reached by traveling 52 miles on Highway 80, and 18 miles on a dirt road to the southwest of Highway 80. An additional mile and a half can be covered by jeep only. Benson, Arizona is the only sizable town near Middle Canyon. Topography Middle Canyon derives its name from its position near the center of the east side of the Whetstone Mountains (PI. VH).

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