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USGS Scientific Investigations Map 3236, Pamphlet

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USGS Scientific Investigations Map 3236, Pamphlet Geologic Map of the Topock 7.5´ Quadrangle, Arizona and California By Keith A. Howard, Barbara E. John, Jane E. Nielson, Julia M.G. Miller, and Joseph L. Wooden Pamphlet to accompany Scientific Investigations Map 3236 2013 U. S. Department of the Interior U. S. Geological Survey Front cover: View downstream into Topock Gorge (“Head of Mojave Cañon”) as pictured in the Report upon the Colorado River of the West (fig. 16 of Ives, 1861). Miocene rocks on the skyline dip steeply to the right (west) in hanging-wall blocks above the Chemehuevi Detachment Fault and Devils Elbow Fault. Contents Abstract............................................................................................................................................................................................ 1 Introduction ...................................................................................................................................................................................... 1 Acknowledgments........................................................................................................................................................................ 2 Geography ....................................................................................................................................................................................... 2 Historical Significance...................................................................................................................................................................... 4 Previous Geologic Investigations..................................................................................................................................................... 7 Tectonic Block Diagram ................................................................................................................................................................... 8 Proterozoic Rocks.......................................................................................................................................................................... 10 Mesozoic Intrusions ....................................................................................................................................................................... 11 Sub-Miocene Unconformity............................................................................................................................................................ 13 Miocene Rocks Related to Tectonic Extension.............................................................................................................................. 14 Lower Miocene Volcanic and Sedimentary Rocks..................................................................................................................... 14 Miocene Intrusions..................................................................................................................................................................... 15 Synextensional Sedimentary Rocks........................................................................................................................................... 17 Miocene Extensional Structure ...................................................................................................................................................... 19 Low-angle Normal Faults ........................................................................................................................................................... 19 Tilted Fault Blocks and the Transverse Gold Dome Fault Zone ................................................................................................ 20 Other Normal Faults................................................................................................................................................................... 22 Folds .......................................................................................................................................................................................... 22 Intrusion Shape and Dike Orientations ...................................................................................................................................... 23 Post-extension Deposits ................................................................................................................................................................ 23 Deposits Predating the Colorado River...................................................................................................................................... 23 Pliocene to Pre-Late Pleistocene Alluvium and Its Relation to Degradation and Aggradation of the Colorado River ............... 24 Late Pleistocene and Holocene Alluvium and Its Relations to Further Aggradations and Degradation of the Colorado River.. 27 Pliocene and Quaternary Deformation........................................................................................................................................... 30 Paleontology .................................................................................................................................................................................. 31 Mineralization and Mineral Exploration .......................................................................................................................................... 31 Geologic History............................................................................................................................................................................. 33 Description of Map Units................................................................................................................................................................ 36 Sedimentary and Volcanic Rocks and Deposits ........................................................................................................................ 36 Rocks Deposited During Extensional Deformation .................................................................................................................... 43 Intrusive and Metamorphic Rocks.............................................................................................................................................. 47 References Cited ........................................................................................................................................................................... 52 Figures Figure 1. Map showing geologic mapping responsibilities in the Topock quadrangle................................................................. 2 Figure 2. Map showing Topock quadrangle geology and major structures................................................................................. 3 Figure 3. Map showing some geographic features in the Topock quadrangle............................................................................ 5 Figure 4. View northeastward up Topock Gorge (Mojave Cañon) from near Devils Elbow ........................................................ 6 Figure 5. Photo showing part of the Mystic Maze (Topock Maze)............................................................................................... 7 Figure 6. Map showing the Topock quadrangle in relation to adjacent geologic map areas and the Colorado River extensional corridor. ................................................................................................................................................... 8 iii Figure 7. A. Interpretive tectonic map of the Topock quadrangle. B. Interpretive tectonic block diagram.................................. 9 Figure 8. Contoured orientation data (poles, lower hemisphere equal-area projection) for areas in the Topock quadrangle... 10 Figure 9. Photo showing view west into the Chemehuevi Mountains in the southwest part of the Topock quadrangle............ 12 Figure 10. A reconstructed pre-extension cross-sectional shape of the Chemehuevi Mountains Plutonic Suite ...................... 13 Figure 11. Conceptual diagram showing stratigraphic relations among Cenozoic sedimentary and volcanic units.................. 14 Figure 12. Photo showing steeply dipping Miocene rocks of the sandstone and conglomerate unit (Ts, here including unlabeled basalt interlayers) in the Gold Dome Mine and The Needles area overlying flows of the lower volcanic sequence (Tv)............................................................................................................................................ 15 Figure 13. A. Photo showing cliff-forming rocks of the Needle Mountain intrusion (Ti) that rise above less resistant rocks of the lower volcanic sequence (Tv) in the foreground. B. Detailed map of the Needle Mountain intrusion (Ti) ............................................................................................ 18 Figure 14. Photo showing bedded mud and sand of the Bouse Formation (Tb) and overlying older piedmont alluvium (QTa1) near Sacramento Wash in the northeast part of the quadrangle................................................................ 25 Figure 15. Photo showing fan dips in fluvial and related deposits of the facies of Santa Fe Railway (Pliocene) ...................... 26 Figure 16. Photo showing boulder conglomerate of Bat Cave Wash (Trbb) resting unconformably on red Miocene gneiss-clast conglomerate (Tcgn)..........................................................................................................................
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