DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DiBECTOB BULLETIN 536 THE NOATAK-KOBUE REGION ALASKA BY PHILIP S. SMITH WASHINGTON GOVERNMENT PRINTING OFFICE 1913 C/f CONTENTS. Preface, by Alfred H. Brooks. .............................................. 7 Introduction. ............................................................. 9 Scope of report. ........................................................ 9 Acknowledgments. ................................................... , 10 Geography. .................. '. ........................................... 11 History of exploration. ................................................ 11 Early expeditions. ................................................ 11 Kobuk basin. .................................................... 12 Noatak basin. .................................................... 16 Alatna basin. ....................................................... 17 Major features of the geography. ....................................... 19 Drainage and relief. ................................................... 20 Kobuk basin. .................................................... 20 The Delta. .................................................. 20 Squirrel River to Reed River province. ......................... 21 The headwater mountain province ............................. 25 Noatak basin ..................................................... 26 The coastal lowland. ........................................... 26 Igichuk Hills .................................................. 27 Mission lowland. .............................................. 27 The second highland. ......................................... 29 Aniuk lowland. .............................................. 30 The headwater mountains. .................................... 32 Alatna River basin. ................................................ 33 Koyukuk River to Helpmejack Creek. .......................... 33 Helpmejack Creek to head. .................................... 33 Main stream. ............................................. 33 Side streams. ............................................. 34 The highlands. ............................................ 36 Climate. ............................................................. 38 Temperature ..................................................... 38 Precipitation. .................................................... 40 Population and settlements. ............................................ 42 Whites. .......................................................... 42 Natives. .......................................................... 45 Animals and vegetation. .............................................. 47 Alatna River basin. ................................................ 47 Noatak River basin. .............................................. 50 Kobuk River basin. ................................................ 52 Descriptive geology. ....................................................... 54 Divisions of the rocks. ................................................. 54 Sedimentary rocks. .................................................... 55 Paleozoic and pre-Paleozoic (?) rocks. .............................. 55 Undifferentiated metamorphic schists. ......................... 55 Distribution................... ............................. 55 Lithologic character. ...................................... 56 Structure. ................................................. 59 Age and interrelations. .................................... 60 3 152882 4: CONTENTS. Descriptive geology Continued. Sedimentary rocks Continued. Paleozoic and pre-Paleozoic (?) rocks Continued. Page. Undifferentiated Paleozoic limestones........................... 61 Distribution.............................................. 61 Lithologic character....................................... 61 Structure.................................................. 63 Age and interrelations. ..................................... 65 Silurian system............................................... 68 Devonian system............................................. 68 Carboniferous system.......................................... 69 Noatak sandstone.......................................... 69 Distribution and lithology............................. 69 Structure.............................................. 71 Age and interrelations................................. 72 Lisburne limestone........................................ 75 Distribution and lithology.............................. 75 Structure.............................................. 76 Age and interrelations................................. 77 Mesozoic era...................................................... 79 Divisions of the rocks.......................................... 79 Triassic system................................................ ' 79 Occurrence................................................ 79 Age and correlation....................................... 80 Lower Cretaceous or Upper Jurassic series....................... 80 Koyukuk group............................................ 80 Distribution.......................................... 80 Lithologic character................................... 80 Structure.............................................. 81 Age................................................... 82 Anaktuvuk group.......................................... 82 Lithologic character................................... 82 Structure..................0............................ 83 Age................................................... 83 Upper Cretaceous series........................................ 84 Bergman group........................................... 84 Distribution.......................................... 84 Lithologic character................................... 84 Structure.............................................. 85 Age................................................... 86 Cenozoic era...................................................... 87 Tertiary system............................................... 87 Lithologic description..................................... 87 Structure.................................................. 88 Age and interrelations..................................... 88 Quaternary system............................................. 89 Divisions of the deposits.................................... 89 Older deposits............................................. 90 Distribution.......................................... 90 Physical features...................................... 90 Noatak basin..................................... 90 Kobuk basin..................................... 94 Koyukuk basin................................... 97 Other areas........................................ 101 Age and interrelations................................. 103 CONTENTS. 5 Descriptive geology Continued. Sedimentary rocks Continued. Cenozoic era Continued. Quaternary system Continued. Page. Recent deposits............................................ 104 Marine gravels.................... I.................... 104 Stream gravels........................................ 104 Glacial deposits....................................... 105 Igneous rocks......................................................... 106 Greenstones.............................................../....... 107 Distribution and general characteristics.......................... 107 Age........................................................... 109 Early effusives and intrusives....................................... 109 Distribution and general characteristics........................... 109 Age........................................................... Ill Granitic rocks..................................................... 112 Distribution and lithologic characters........................... 112 Age and interrelations......................................... 114 Late lavas or basaltic effusives..................................... 114 Distribution.................................................. 114 Lithologic characters........................................... 115 Age........................................................... 116 Veins................................................................ 117 Older quartz veins................................................ 118 Younger quartz veins.............................................. 119 Calcite veins..................................................... 120 Origin of the vein material........................................ 121 Summary of the geologic history............................................ 121 Economic geology.......................................................... 125 General features....................................................... 125 Gold placers............................................................ 125 Zobuk basin..................................................... 125 General conditions............................................ 125 Shungnak region.............................................. 126 Dahl Creek................................................ 126 Kogoluktuk River......................................... 129 Shungnak River........................................... 131 Squirrel River region.......................................... 133 Development............................................. 133 Creek placers............................................. 134 Description of operations.............................. 134 Origin of the gold....................................