Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/50/5/697/3430888/BUL50_5-0697.pdf by guest on 25 September 2021 BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA TUCSON MOUNTAINS, AN ARIZONA BASIN RANGE TYPE BY W. HOBATIO BROWN CONTENTS Page Abstract............................................................................................................................... 698 Introduction........................................................................................................................ 699 Purpose of the investigation..................................................................................... 699 Location and extent................................................................................................... 699 Climate......................................................................................................................... 699 Vegetation.................................................................................................................... 700 Acknowledgments....................................................................................................... 701 Physiography...................................................................................................................... 701 Structural summary................................................................................................... 701 Processes of erosion.................................................................................................... 702 Stage and form............................................................................................................ 704 General statement.............................................................................................. 704 Pediments............................................................................................................ 704 Escarpment.......................................................................................................... 707 Dip slope.............................................................................................................. 708 Formational units............................................................................................................... 709 Columnar section........................................................................................................ 709 Pinal schist.................................................................................................................. 711 Paleozoic rocks............................................................................................................ 711 Cambrian system........................................................................................................ 711 Devonian system........................................................................................................ 712 Mississippian system.................................................................................................. 712 Pennsylvanian system............................................................................................... 712 Permian system.......................................................................................................... 713 Cretaceous system...................................................................................................... 713 General statement.............................................................................................. 713 Volcanics.............................................................................................................. 713 Recreation red beds........................................................................................... 715 Amole arkose...................................................................................................... 716 Correlation.......................................................................................................... 720 Laramide intrusive rocks.......................................................................................... 720 General statement.............................................................................................. 720 Amole granite...................................................................................................... 721 Granite porphyry............................................................................................... 722 Amole quartz monzonite................................................................................... 723 Amole latite......................................................................................................... 725 Pegmatites, aplites, and lamprophyres.......................................................... 726 Sedimentary Hills stock.................................................................................... 727 Saginaw stock..................................................................................................... 728 (697) Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/50/5/697/3430888/BUL50_5-0697.pdf by guest on 25 September 2021 698 W. H. BROWN----TUCSON MOUNTAINS Page Tertiary effusive rocks............................................................................................... 729 General statement.............................................................................................. 729 Cat Mountain rhyolite...................................................................................... 729 Safford tuff.......................................................................................................... 731 Diopside andesite................................................................................................ 733 Biotite rhyolite.................................................................................................... 734 Shorts Ranch andesite....................................................................................... 734 Tertiary conglomerate....................................................................................... 735 Rillito andesite.................................................................................................... 736 Upper andesite.................................................................................................... 736 Tertiary intrusive rocks............................................................................................ 739 Safford dacite neck............................................................................................. 739 Beehive rhyolite neck........................................................................................ 740 Silver Lily dikes.................................................................................................. 741 Warrens Ranch latite sill.................................................................................. 742 Spherulitic rhyolite............................................................................................ 742 Tertiary (?) lake beds................................................................................................ 743 Tertiary or Quaternary basalts................................................................................ 744 Quaternary alluvium.................................................................................................. 746 Structure.............................................................................................................................. 748 Introduction................................................................................................................ 748 Pre-Tertiary basement structure............................................................................. 748 Tertiary volcanic structure....................................................................................... 751 Tertiary (?) lake-bed structure................................................................................ 752 Basaltic mesa structure............................................................................................. 753 Regional structure...................................................................................................... 754 Ground water...................................................................................................................... 755 Mineralization..................................................................................................................... 757 Conclusions......................................................................................................................... 758 Works to which reference is made................................................................................... 759 ILLUSTRATIONS Figure Page 1. Map showing location of Tucson Mountains........................................................ 700 2. Columnar section of Tucson Mountains................................................................ 710 Plate Facing page 1. Geologic map and cross sections.............................................................................. 697 2. Western side of range................................................................................................ 708 3. Safford tuff.................................................................................................................. 709 4. Safford neck...............................................................................................................