Structural Investigations of the Italian Trap Allochthon, Redington Pass, Pima County, Arizona
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Structural investigations of the Italian Trap Allochthon, Redington Pass, Pima County, Arizona Item Type text; Thesis-Reproduction (electronic) Authors Benson, Gregory Scott 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 24/09/2021 07:35:39 Link to Item http://hdl.handle.net/10150/557699 STRUCTURAL INVESTIGATIONS OF THE ITALIAN TRAP ALLOCHTHON, REDINGTON PASS, PIMA COUNTY, ARIZONA by Gregory Scott Benson A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE In the Graduate College THE UNIVERSITY OF ARIZONA 19 8 1 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 borrowers under rules of the Library. Brief quotations from this thesis are allowable without special 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 his judg ment the proposed use of the material is in the interests of scholar ship. 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: *G. H. DAVIS Date Professor of Geosciences ACKNOWLEDGMENTS I am deeply thankful to several people without whose help this thesis would not have been possible. Foremost, I am grateful to Dr. George H. Davis, who acted as thesis advisor, for suggesting this project, arranging for my transportation to and from the study area, and for his firm guiding hand in the editing of this manuscript. Drs. Peter Coney and Joseph F. Schreiber, Jr. were helpful by providing enlightening discussion of field relationships. This work has bene- fitted greatly from conversations with Steven H. Lingrey, a fellow graduate student, who graciously led me on a field trip in Paige Canyon and provided me with his maps. Dean Warner lead me through his thesis study area in the Bar LY Ranch/Mineta Ridge locality and discussed his findings with me. I would like to thank Jeffrey A. Grover and Ralph D. Rogers for their moral support and lengthy dialogues, and my wife Kellee for her constant understanding, inestimable support, and the typing of the manuscript. iii TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS.................. .. ..................... vi ABSTRACT ...................................................... viii INTRODUCTION.......... .................... .................... 1 H CN CN CN HCN VO m P u r pose.................... .. Location of Area .............. Previous Work .......... GEOLOGY OF ITALIAN TRAP ALLOCHTHON . Major Structural Components .... Rock Units ............ Autochthonous Crystalline Rocks Porphyritic Granite .... Garnet Muscovite Granite .......... .............. 10 Microdiorite . ..................................... 12 Mylonitic Gneisses .................. 12 Allochthonous Crystalline R o c k s ............. 15 Upper Domain . ......................... 15 Lower Domain . ............ 15 Allochthonous Metasedimentary Tectonites .............. 18 Introduction ........... .......... 18 Cambrian Bolsa Quartzite .......................... 19 Cambrian Abrigo Formation .......................... 21 Devonian Martin Formation .......................... 21 Mississippian Escabrosa Limestone .... .......... 22 Pennsylvanian Horquilla Limestone .................. 24 Pennsylvanian and Permian Earp Formation .......... 26 Allochthonous Tertiary Sedimentary and Volcanic Rocks . 28 Mlneta Formation .......... 28 Turkey Track Porphyry ............................... 29 General Orientations ..... ...................... ... 31 Structures of Italian Trap Allochthon ...................... 33 Lineation and Boudins in the Allochthon ................ 33 Faults of the A l l o c h t h o n ............................... 36 Low-Angle Detachment Fault ..... .............. 36 Faults within the A l l o c h t h o n ...................... 40 Subconcordant Low-Angle Faults .................... 41 High-Angle Faults ................................... 42 iv V TABLE OF CONTENTS— Continued Page Faults in the Autochthon ............................... 43 Folds in the Italian Trap A l l o c h t h o n .................. 44 Introduction ....................................... 44 Northeast-Trending Upright F o l d ................... 44 Northwest-Trending Upright Folds .............. 44 Asymmetric Folds ................................... 46 INTERPRETATION...................... 51 Slip-Line Determination ..................................... 51 Subconcordant Low-Angle Faulting .............. .... 51 Asymmetric Folding ................................. 51 Fault G r ooves....................................... 53 High-Angle Faulting ....... ...................... 56 Detachment Faulting ..................................... 56 Shape of F a u l t ................................... 57 Orientation of Planar Elements .................... 57 Significance of Tectonite Fabrics ............ 58 Metasedimentary Rock Fabrics . ........... 58 Mylonitic Crystalline Rock Fabrics .................... 59 Conditions of Deformation........................ 60 Grade of Metamorphism.......... 60 Nature of Deformation ................................... 61 Folding............................................. 61 Faulting ......................... 61 CONCLUSIONS......................................... 63 Timing of Tectonic Events ..................................... 63 Emplacement of Italian Trap A l l o c h t h o n .................. 66 Summary ..... ........................................ 68 APPENDIX 1: Supplemental Orientational Data ..................... 71 APPENDIX 2: Asymmetric Fold D a t a ................................. 77 LIST OF REFERENCES 81 LIST OF ILLUSTRATIONS Figure Page 1. General Geology and Diagrammatic Cross Sections of the Santa Catalina-Rincon Metamorphic Core Complex ........ 3 2. View of Italian Trap Allochthon from Redington Road; Looking South ........................................... 4 3. Major Structural Components of Italian Trap Allochthon. and Its Undergirding Crystalline Terrane .............. 7 4. Map of Faults, Lithologies, and Structural Domains of Italian Trap Allochthon .......... .......... 8 5. Structural Geologic Map of Italian Trap Allochthon .... 13 6. Geologic Cross Sections through Italian Trap Allochthon............................................... 14 7. Large-Scale Maps of Crystalline Tectonites in Lower Domains of Italian Trap Allochthon ...................... 17 8. Close-Up Photograph of Bolsa Quartzite near Detachment F a u l t s ................................................. 20 9. Photograph of Escabrosa Limestone Illustrating Schistose Foliation in Pure Calcite Marble ...................... 23 10. Close-Up Photograph of Horquilla Limestone Showing Abundant Siliceous Interbeds .... ............... 25 11. Photograph of Hematite Pseudomorphs after Pyrite in Phyllites of the Earp Formation ......................... 27 12. Photograph of Typical Outcrop of the Tertiary Turkey Track Andesite P o r p h y r y .......... 30 13. Pi-Diagram of 659 Foliation and Compositional Layering Measurements from Italian Trap Allochthon .............. 32 14. Lower-Hemisphere Equal-Area Stereographic Projection of Lineation Measurements in the Allochthonous Tectonites . 34 vi vii LIST OF ILLUSTRATIONS— Continued Page 15. Tracing of Field Sketch of Outcrop Showing Three Dimensional Nature of Lenses within the Horquilla Limestone.................. .......................... 35 16. Tracing of Field Sketch of Small Isoclinally Folded Siliceous Interbed in the Escabrosa Limestone of Domain i l l .............................. 35 17. Topographic Analysis of Italian Trap Area as Guide to Determining Probable Detachment Fault Shape ........... 38 18. Topographic Map of Tanque Verde Wash Illustrating Steep Dips of the Detachment Surface which Define Deep Fault Grooves ......................................... 39 19. Lower-Hemisphere Equal-Area Stereographic Projection of Poles to Bedding Planes in the Mineta Formation of Domain x v ............ 45 20. Small Asymmetric Fold of Transitional Style in the Upper Escabrosa Limestone ................................... 48 21. Photograph of a Large Asymmetric Fold at the Contact between Domains ill and vi ....................... 49 22. Contoured Lower-Hemisphere Equal-Area Stereographic Projection of 46 Asymmetric Fold Ax e s ................. 50 23. Lower-Hemisphere Equal-Area Stereographic Projection of Asymmetric Fold Axes Individually Labeled as to Sense of A s y m m e t r y ......................................... 54 24. Lower-Hemisphere Equal-Area Stereographic Plot of Asymmetric Fold Axes Exclusive of Those in Domain ill . 55 25. Tectonic Paragenesis Chart Showing Relative Timing of Ductile, Moderately Ductile, and Brittle Deformational and Faulting E v e n t s ........................ 64 26. Diagrammatic Structural Profiles through a) Redington Pass, and b) Paige Canyon Area, Comparing