DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR BULLETIN 532 ^ -J 4 THE KOYUKUK-CHANDALAR REGION ALASKA BY A. G. MADDREN WASHINGTON GOVERNMENT PRINTING OFFICE 1913 CONTENTS. Page. Preface, by Alfred H. Brooks __ 7 Introduction____________________________ ______ _ 9 Topography _ 11 General features _ _ __ 11 Relief______________-__-___________-__-___ 11 Yukon Flats_____________ _______________ 11 Hodzana highland 13 Koyukuk Flat and Valley________________________ 34 Endicott Mountains __ _______________ _ 15 Drainage __ _ i 15 Streams flowing southward to the Yukon_____________ 15 General features _ __ 15 Chandalar River and tributaries________________ 16 Orenzik, Hodzana, and Dall rivers __ __________ 21 Koyukuk drainage basin_ _ 22 Tributary streams _____________ 22 Kanuti River ____________________________ 23 South Fork of the Koyukuk and tributaries__________ 23 Middle Fork of the Koyukuk and tributaries________ 26 Climate__ - 27 Vegetation___ _ __ _ _ 28 Animal life - 29 Population and settlements___________________________ 29 Transportation and trails _ __ _ __ _ ___ 30 Geology ___ 32 Principal features _ 32 Geologic map 33 General section _ 34 Birch Creek schist (pre-Ordovician?)__ ____________.._ 34 General features____________________________ 34 Lithology, distribution, and structure_______________ 36 Dall River area__________________________ 36 Koyukuk-Chandalar area_______________________ 38 General features_____i_________________ 38 "Rapids" schist_______________________ 39 Amphibolite [hornblende] schist______________ 40 "Lake quartzite schist"___________________ 40 Intrusives___ _ _________ ______ 41 John River area_________________________ 44 Totsen "series"_______________1______ 44 Character and occurrence________ ________ 44 Structure ____ ____ __ 44 Age and correlation. __ 44 171453 4 CONTENTS. Geology Continued. Birch Creek schist (pre-Ordovician?) Continued. Page. Summary_________________________________ 45 Correlation _____________________________ 45 Structure. _,__________________ 46 Mineralization ______________;____________ 47 Paleozoic rocks _ __________________________ 49 Subdivisions_____________________________.._ 49 Devonian (?) rocks_______ _._____________ 50 Character and distribution,- .__________________ v 50 Age and correlation_^_____________________ 51 Carboniferous (?) rocks______________________ 51 Lithology, structure, and distribution_____________ 51 Age and correlation_____ ________________ 52 Mesozoic rocks ______ ___ _ _______________ 53 General features_______ ____ ______________ 53 Cretaceous system___ __ _ ______________ 54 Character, structure, and distribution__. _________ 54 Age and correlation______ ___(_____________ 54 Mesozoic (?) intrusive rocks___ ________________ 55 Cenozoic rocks ___ __________ ______'_________ 56 Tertiary system____ _______ _ __________, 56 Cenozoic lavas (Tertiary or Quaternary)______________ 56 Quaternary system _ __ _ 58 Pleistocene series _________________________ 58 Sediments _ _ : ___ __________ 53 Glaciation ___________________________ 60 Recent series __________ ______________ 66 Mining___________ _________ _____________ 68 Production ___.__ ________ _____________ 68 Methods of mining_______ ____i __________ 71 Surface mining _ __________ ______________ 71 Underground mining ________ ______________ 71 Costs and wages __________ -_____________ 72 Economic geology '_ ___ _~ 74 General conditions ____________ ________________ 74 Historical outline __ 76 Distribution and geologic association of gold____________ 77 Classes of placers ____ _ _ _ 78 Criteria for classification-_____________________ 78 Present stream placers_ ___ ___________ __ 78 Bench placers -:__________ __________'. _______ 79 Unconsolidated formations_____________________ 80 Summary of classification___________________ __ 80 Source of placer gold ___ _ ....___ 82 The placers __ 83 Koyukuk district________'___ __ ______ 83 Drainage basins __ ___ ____ 83 Middle Fork of Koyukuk River ____ ____ 84 Tramway Bar and Chapman Greek- i_ 84 Twelvemile Creek_____ _______._______ 85 Rose Creek ________ ________ 86 Porcupine Creek _______ _ 86 Slate and Myrtle creeks__ ___ 86 CONTENTS. 5 Economic geology Continued. The placers Continued. Koyukuk district Continued. Middle Fork of Koyukuk River Continued. Page. Clara Gulch ___________________.._____ 89 Kelly Gulch____________________________ 89 Marion Creek___________________________ 90 Emma Creek_______________-_________ 90 Wiseman Creek ________________________ 91 Nolan Creek and tributaries ______ ______ 92 General features _____________________ 92 Bench gravels_______________________ 93 Shallow gulch gravels_________________ 93 Deep frozen gravels___________________ 93 Character of gold__________,_________ 94 Minnie Creek _____ ________ _ _____ 94 Union Gulch___________________________ 95 Hammond Creek 95 Goldbottom, Swift, and Buckeye gulches 96 Vermont Creek________________________ 97 Streams between Hammond Creek and Gold Creek____ 99 Gold Creek ________________ __________ 99 Linda Creek _________________________ 102 Settles River and tributaries..- ____ 104 South Fork of Koyukuk River__________________ 105 General features __________________________ 105 Gold Bench and vicinity___________________ 105 Davis and other creeks___________________ 107 Headwaters of Glacier Creek________-_______ 107 North Fork of Koyukuk River_________________ 108 General features ______________________ -108 Mascot Creek________________________ 108 Wild River _____________________________ 109 John River ______________________________ 110 Dall and Hodzana River region_______.___________ 110 Cbandalar district ________________ ________ 110 General features _______________ ________ 110 Quartz lodes_____________________'._________ 111 Placers _________________ _ ______ 115 Index _ _ _ 117 ILLUSTRATIONS. Page. PLATE I. Topographic reconnaissance map of Koyukuk - Chandalar region___________________________________ In pocket. II. A, Hodzana highland, incised by upper valley of Fish Creek; B, Mountainous portion of Hodzana highland between upper forks of Bonanza Creek_______________________ 12 III. A, Weathering and wind erosion of granite at head of Dall River; B, Flats on Middle Fork of Koyukuk River__. _____ 14 IV. A, Endicott Mountains, in upper Dietrich River valley; B, Rapids on Chandalar River, 128 rniles above mouth______ 15 V. Geologic reconnaissance map of Koyukuk-Chandalar region. In pocket. VI. A, Limestone and schist contact in Endicott Mountains; B, Lime­ stone cliffs south of Bettles River, a possible fault scarp___ 34 VII. A, Pleistocene silt bluffs on Koyukuk River near Arctic Circle; B, Gold Creek valley near mouth_________________. 58 VIII. A, Horses towing freight scow, Middle Fork of Koyukuk River; B, Myrtle Creek valley_______________________ 86 I.. A, Nolaii Creek valley, shoeing principal mining plants; B, Nolan Creek valley, showing boiler house and dumps_____ 92 FIGURE 1. Map showing physiographic provinces of Koyukuk-Chandalar region _________________________ 12 2. Sketch map showing distribution of timber in Koyukuk-Chanda­ lar region .___ _________ _________ 28 6 PREFACE. By ALFRED H. BROOKS. In 1899 F. C. Schrader and T. G. Gerdine carried a topographic and geologic reconnaissance survey through the Chandalar and Ko- yukuk basins, in northern Alaska. This was the first investigation of the mineral resources north of the Yukon. The time was well chosen, for it was in 1899 that the first important discoveries of placer gold were made in the Koyukuk district, though there had been some mining on the river bars during the previous decade. Since 1899 the Koyukuk has produced gold to the value of about $2,500,000. Some promising gold-bearing veins have also been found in the Chan­ dalar region. As this progress in mining gave promise of yielding much new information about the occurrence of mineral deposits, and as Schra- der's report had long been out of print, a second investigation of this field seemed justified. This resurvey was made by A. G. Mad- dren in the course of a single field season, during which he visited practically all the important localities of mining and also consider­ ably extended the areal surveys. Mr. Maddren had the benefit of the geologic results achieved since 1899 in other parts of the Yukon basin, which have helped to elucidate a number of the stratigraphic problems. Although Mr. Maddren's conclusions as regards the geo­ logic sequence differ-somewhat from those reached by his predecessor in this field, yet this volume must in a measure be regarded as a revised edition of Schrader's report, which has proved remarkably accurate considering the conditions under which the field investiga­ tions were carried out. Other systematic surveys have recently been made in northern Alaska. In 1911 and 1912 Mr. Maddren carried a geologic survey northward from Porcupine River to the Arctic Ocean, along the international boundary (one hundred and forty-first meridian, west longitude). In 1910 and 1911 P. S. Smith made reconnaissance sur­ veys in the Kobuk and Noatak region, and the results of his work are embodied in a report 1 now in preparation, which will include a i Smith, P. S., The Noatak-Kobuk region, Alaska : Bull. U. S. Geol. Survey No. 536. 7 8 KOYUKUK-CHANDALAE REGION, ALASKA. geologic map of an area that extends eastward to the western bound­ ary of the area mapped in the present volume (PI. V, in pocket). These two maps will serve to elucidate the general geologic features of this