Abstract Origin and Structure of the Poverty
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ABSTRACT ORIGIN AND STRUCTURE OF THE POVERTY HILLS, OWENS VALLEY FAULT ZONE, OWENS VALLEY, CALIFORNIA by Tatia R. Taylor Structural field mapping and analyses of the Poverty Hills reveal a complex deformational geometry consistent with that of a transpressional positive-flower-structure uplift. Kinematic indicators show vertical and horizontal translation facilitated by reverse faulting with a strong oblique strike-slip component. The onset of deformation in the Poverty Hills is estimated at ~1.7 Ma, and the Owens Valley fault is proposed to have stepped westwards in kinematic response to the rapid development of regional transtensional fault patterns. Geometric modeling of uplift points to a constant slip rate of 1.27-1.44 mm/yr since ~1.7 Ma on the northern Owens Valley fault. These kinematic, geometric, and temporal relations are utilized to better constrain slip partitioning and distribution across the major fault systems in the region and to characterize the spatial and temporal evolution of the Owens Valley basin, the Owens Valley fault, and the Eastern California Shear Zone in this region. ORIGIN AND STRUCTURE OF THE POVERTY HILLS, OWENS VALLEY FAULT ZONE, OWENS VALLEY, CALIFORNIA A Thesis Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Science Department of Geology by Tatia R. Taylor Miami University Oxford, OH 2002 Advisor: Dr. Yildirim Dilek_____________________ Reader: Dr. Brian Currie______________________ Table of Contents Page TITLE PAGE................................................................................................................. i TABLE OF CONTENTS.............................................................................................. ii LIST OF FIGURES ..................................................................................................... iii LIST OF TABLES...................................................................................................... vii ACKNOWLEDGMENTS ......................................................................................... viii CHAPTER 1: GEOLOGIC BACKGROUND...............................................................1 CHAPTER 2: FIELD OBSERVATIONS ..................................................................10 CHAPTER 3: STRUCTURAL ANALYSIS ..............................................................25 CHAPTER 4: IMPLICATIONS .................................................................................28 REFERENCES ............................................................................................................85 ii LIST OF FIGURES Fig. 1. Schematic map of geologic features in the Owens Valley region. 41 Modified from Martel et al., 1987. Fig. 2. Lithologic map of Owens Valley region. From Beard and 42 Glazner, 1995. Fig. 3. The Inyo Thrust and related structures. Modified from Stevens 43 and Olson, 1972. Fig. 4. Map of late Cenozoic faults of the Eastern California Shear 44 Zone from the Garlock Fault to the Walker Lane. Fig. 5. Relative motion of the Sierra Nevada with respect to the Colorado 45 Plateau since 36 Ma. Northwesterly motion of SN started ~10 Ma. From Wernicke and Snow, 1998. Fig. 6. Faults of the northern Eastern California Shear Zone. 46 Adapted from Lee et al., 2001. Fig. 7. Map of Owens Valley with bounding ranges. Location of 47 northern and southern grabens shown on east side of basin. From Gillespie, 1991. Fig. 8. Enhanced Landsat 7 image of Poverty Hills and adjacent 48 geologic and geographic features. Ages given for dated volcanics of Big Pinevolcanic field. Fig. 9. View to the east of the Poverty Hills. 49 Fig. 10. Structural and geologic map of the Poverty Hills compiled from 50 structural mapping and field-collected data. Taylor, 2002. Fig. 11. Slickenlines on granodiorite boulder (not in place). East central 51 Poverty Hills. Fig. 12. Fluvial and colluvial deposits on NW margin of Poverty 52 Hills, ~8-10 m above Tinemaha Creek. Fig. 13. Angular unconformity in Plio-Pleistocene lacustrine sediments. 53 Eastern fault block near Tinemaha Reservoir. Fig. 14. Map of Big Pine Volcanic Field with eruption ages of dated 54 iii volcanics and local faults. Fig. 15. Shaft at uplifted contact between granodiorite and Paleozoic 55 rocks. Fault breccia of W-bounding normal fault on right. View to E. Fig. 16. Structural and geologic cross section A-A′ (Fig. 10), 56 Poverty Hills. Fig. 17. Schematic map of Owens Valley fault zone showing 57 orientations of regional and local principal stresses. Fig. 18. Shear zone in granodiorite. East side Poverty Hills. 58 View to the north. Fig. 19. Models of transpressional push-ups, or positive flower 59 structures. From Sylvester, 1988. Fig. 20. Breccia at fault contact. Mississippian shale clasts in 60 CaCO3 matrix. Southeastern Poverty Hills. Fig. 21. Tilted Quaternary basalt flow capping deformed 61 granodiorite on the north edge of Poverty Hills. View to the southeast. Fig. 22. Oblique reverse fault in Mississippian shale. SW 62 margin of Poverty Hills. View to the northeast. Fig. 23. Mississippian shale thrust above Pennsylvanian siltstone. 63 SE side Poverty Hills. View to NW. Jake for scale. Fig. 24. Stacked wedges of sheared and faulted granodiorite. SE 64 Poverty Hills. Fig. 25. Elliptical sag pond playa in structural half-graben. 65 Central Poverty Hills. View to the W. Fig. 26. NW and W margin of Poverty Hills showing scarp 66 of W-bounding normal fault. View to SE. Fig. 27. NE- and SW-dipping ‘limbs’ of columnar basalt sheet 67 stepping down to the SW across NW-trending basement steps. View to the SE. Fig. 28. View north from northwestern Poverty Hills. 68 iv Fig. 29. Contoured equal area stereographic projection of faults 69 in granodiorite. Fig. 30. Equal area stereographic projection of faults with slickenlines 69 in granodiorite. Fig. 31. Contoured equal area stereographic projection of faults 70 in metasediments. Fig. 32. Equal area stereographic projection of faults with slickenlines 70 in metasediments. Fig. 33. Contoured equal area stereographic projection of foliations 71 in granodiorite. Fig. 34. Equal area stereographic projection of foliations with 71 lineations in granodiorite. Fig. 35. Contoured equal area stereographic projection of foliations 72 in metasediments. Fig. 36. Equal area stereographic projection of foliations with 72 lineations in metasediments. Fig. 37. Equal area stereographic projection of bedding in metasediments 73 in west central Poverty Hills. Fig. 38. Distribution of fold axes in metasediments of the west 73 central Poverty Hills. Fig. 39. Equal area stereographic projection of bedding in metasediments 74 of isolated hill in southwestern Poverty Hills. Fig. 40. Distribution of fold axes in metasediments of isolated hill in 74 southwestern Poverty Hills. Fig. 41. Equal area stereographic projection of bedding in metasediments 75 of the southern Poverty Hills. Fig. 42. Distribution of fold axes in metasediments of the southern 75 Poverty Hills. Fig. 43. Distribution of fold axes in metasediments of all domains. 76 Fig. 44. Equal area stereographic projection of bedding of sediments 76 and basalt flow east of Hwy. 395. v Fig. 45. Tilt restoration of younger (pink) and older (blue) 77 fluvial/lacustrine beds of tilted fault block. Fig. 46. Equal area stereographic projection of ‘limbs’ (Fig. 27) of 77 disturbed basalt flow in southern Poverty Hills. Fig. 47. Tilt restoration of basalt flow (blue) with directional flow 78 lineations (magenta) in the southern Poverty Hills. Fig. 48. Spatial and temporal model of NW-directed oblique transtension. 79 Owens Valley basin prior to ~1.7 Ma. Fig. 49. Spatial and temporal model of NW-directed oblique transtension. 80 Present Owens Valley basin. Fig. 50. Slip distribution with calculated (this study) and published slip 81 rates for faults in the vicinity of the Poverty Hills and Owens Valley. vi LIST OF TABLES Table 1: Ages of dated BPVF basalts 82 Table 2: Summary Geochronology 83 Table 3: Offset Estimates 84 vii Acknowledgments I wish to acknowledge Dr. Yildirim Dilek for presenting me with the opportunity to pursue my project. My infinite gratitude goes to my son Jacob (who does not remember me as anything but his Mom, the student) for following me all over the country and providing the daily reminder that we have to pick our battles carefully and above all, life is far too short to get too serious about. I could not have finished without the help of some very important people. The faculty and graduate students at Miami University have given support and encouragement and sometimes just an ear when I really needed it. Shawn Irvin, Carrie Wright, and Art Losey will always have a couch in my living room. Darin Snyder has made time for me even when he had none (especially if it meant using Corel). Dr. Brian Currie was my reader and got my basemaps ready. Cathy Edwards went far beyond the call of duty so that I was able to travel and participate, and still know that things were safe at home. Thank you all. My friends and colleagues at the University of California White Mountain Research Station have served as a wealth of information and encouragement, and have made their home my home. Dr. Nancye Dawers, Tulane University, Dr. Jim McClain, University of California Davis, Dr. Anjela Jayco, U.S. Geological Survey, Menlo Park, and Dr. Clemens Nelson (ret.), University of California Los Angeles, and many other students and researchers, have all been an inspiration. Cheryl Seath at the California Bureau