UNITED STATES DEPARWNT OF THE INTERIOR GEOLOGICAL SURVEY GEOLOGY OF THE KUKPOWRUK-NUKA RIVERS REGION, NORTHWESTERN ALASKA E. G. Sable, J. T. Dutro, Jr., M. D. Mangus, and R. H. Morris Open-File Report 81-1078 This report is preliminary and has not been edited or reviewed for conformity to Geological Survey standards and nomenclature. Page Ceology . -con t i nurd .......................... lntruduct ion 1 Mississippian system-.continued ......... I Locat ion. size. and acccss ill i li t y vf rc.$ion Lisburne group continued ................... Previuus invest igac ions 2 Utukok formation (new) ............... ............ Natureandscopeof tlleirlvrstigatir)n 3 Distribution and outcrop ............ ................. Field operations. 1447-1953 5 Character and thickness ............. ...................... Ar.knoi~ledgments. 8 Stratigraphic relationsl~ips........... ............................ I.eoyr.rptiy 9 Kogruk formation (new) ............... ~rcl~rolo~y.vegetation. wildlife. climate ......... 9 Distribution and outcrop ............ ................... Topography and drainage I1 Character and thickness ............. Stratigraphic relationsiiips ........... Tupik formation (new) ................ Dcvorliaa system....................... 19 Distribution and otltcrop ............ Kugururok formation (new) ................ 19 Character and thickness ............. Uistribution and outcrop .............. 19 Carboniferous-Permian systems ................ Character and tl>ickness............... 20 Cherty and shaly rocks ................. ............. Stratigraphic relationships 22 liistribution and outcrop .............. Fossils and age ................... 23 Character and thickness ............... Elode of deposit inn ................. 24 St rilLjgrnl,lbic relationstrips ............. Undifferentiated Dvvonian rocks ............. 25 Fossils r~nriaye ................... blississippian system .................... 29 Nuki~iornia t ion ..................... I.~S~IITI~L*group ..................... 30 llist rihut iur~;~rlri rwi.urc'llcc. ............. Con tents--continued Page The information contained in this report was collected during field Igneous rocks--continued investigations between 1947 and 1953. The text was written In 1957, and Mode of occurrence and age ................ 214 the generalized geologic map that accompanies the report (fig. 1) was Structural geology ...................... 216 compiled at that time. Although some of the statements or conclusions Folded belt. ....................... 218 contained herein may seem outdated when compared to modern theories, the Folded and faulted belt. ................. 221 report contains information that has not been published elsewhere, to- Overthrust belt. ..................... 225 gether with early interpretations that support the current hypotheses Interpretation and age of faulting ............ 230 regarding the development of the Brooks Range orogen. Economicgeology ....................... 232 Names and inferred age designations of stratigraphic units have I Petroleum possibilities. ................. 232 been changed from the original report to correspond with current usage. Referencescited ....................... 237 Locations of sections that are given by geodetic coordinates are from 1 planimetric maps used in mapping and compilation during the original work during the 1950's. Discussion of the Nuka Formation does not consider the much-studied section at Nuka Ridge (Tailleur, Mamet, and 1 ILLUSTRATIONS Dutro, 197?), and the Nuka Formation as described herein probably in- cludes Lower Mississippian, Permian, and Triassic strata of the Nuka Figure 1. Generalized geologic and structural map of the Kukpowruk-Nuka Rivers region, Northwestern Alaska Ridge exposures. The pelecypod Buchia reported herein was previously assigned to the genus Aucella. Both are considered to be of Early Cretaceous (Ncocomian) age, but in earlier reports, fine-ribbed Aucella was considered to be of Valanglnian age and coarse-ribbed Aucella was thought to be Berriasian. In the sec Lion entitled "Structural Geology1', the "(hrert\~rustbelt" is generally equated with the "Disturbed belt" oi later writers (Tailleur and Llrosgb, 1970). vii viii ill Y .4 w V] 0 a0 Y P P c S .rl m w 4 T a u; I ill 0 P a *A ill 4 rl0 .c m ill 'Y E 2 v] -rl Q rl E: P u 0 2 al m M 3 ri 2 v al m ?I h &J m w m u m e U Li m b ?. rl U u r: w ill u P U ri * rl Vc-. '+ E Li M ul m Y 30 U m > ill .A al s 0 X U a U Lrr rl m e h 3 d Y z CO w 4 Oy m m U u m u Li z i, d .o"n Li Yl .OU uc .='A 0 'rlU .cum C ?1 e c cam 0 .?+ .A Y b. WJw me- € '3, 0-L.., rrmm s25 u 0 E* I;IBLL>CY 01,. 'l'lil? KUKl1(IWHUt;-NULI 1:I VISHS I<EGl ON, NOR'I'HIJlrS'FIIKN AI,IISKA Snlal1r.r lakes, nlostly suitable only for crnerjiency landings, are scattered b Y in the soutllern fuorliills and along the mounti~in front. A gravel air- Edward C. Sable, .J. Tl~ui~tdsDutro, Jr., M.jrvio I). Mangus, strip, along the east side of the Utukok River 4 miles north of Driftwood and Rubcrt H. Morrls Creek was constructed in 1950, but because of the low position near the river it may now be unsuitable for wheel landings. 1NTKOl)iIC'~L Foot travel in the foothills and mountains is not difficult except Location, Size, and Accessibility of Region in the swampy lowlands of the foothills. Although the east- and north- Tlie Kukpouruk-Nuka Rivers region includes more than 3,200 square miles in east-trending ridges afford the best foot travel, they are mostly the western part of the DeLong Mountains, a part of the flruoks Range province, and discontinuous. Tracked vellicle travel is easily accomplished through- in the Arctic Foothills province north of the mountains. Most of the out the loothills and along most stream valleys to the mountain divide. region lies in the Southern Foottlills section and a lesser part in Routes must be selected with care through low swampy terrain, for the Northern Foothills section. The north- example, the area east of Lake Noluk and along the Colville River. ern part of the area overlaps with the Utukok-Corwin region (Chapman Streams flowing south from the divide are deeply incised, streun with and Sable, 1960) and the eastern part lies within NavaL Petroleum large houLders and, in some places flow over small waterfalls. In Reserve No. 4. Explorations during the years 1947 through 1953 were these valleys, vehicle travel is difficult or impossible. The divide undertaken as a part of the U.S. Geological Survey's program of irivesti- was crossed in one place with tracked vehicles, at Weasel Pass between gatiocs for the U.S. Deportment of the Navy in Naval Petroleum Keserve the Utukok and Kliguroruk Rivers. No suitable route over the divide is No. 4 and adjacent lands. known in the region east of this pass. The Kukpowruk-Nuka region can be reached by air Irum Kotzebue, Major rivers ;ire navigable to within 10 miles of the divide by Point Hope, and Point Lay, the nearest permanent settlements. Uistances boats having a dralt of less than one foot. During low water, however, to the center of the region from these towns are about 130, 130, and shallow channels and rifllrs make boat travel almost impossible. In 80 miles, respectively. In the winter season ski-airplane landings the mountains even the major strean~scan be crossed easily on foot at are possible at many places. During the sumlcr only a few lakes are selected places. known to be suitable for float-airplane landings; these include Lake Previous Investigations Noluk, Kvkolik Lake, and the large lake 5 miles suuth of Igluo Elr>untain. F(l1lowing the estiihlisl~n~r~ltof Naval Petroleum Reserve No. 4 hy Enctrutive Order in February. 1923, n part of the Kukpowruk-Nuka regioo w.2~iirst pmpltrr~d in :\ug~rsl .rnJ St-pt~.mlrpri~i 1924. A U.S. (:c~llc~~i~.~~l 5lll.v~.): j'drty 1l11~1c.rWi 1 l irllu 1'. I:LII-:JI~.IWL.~~~CCI stutly ctte stratigra[>hy and structrJre, and to evaluate rhe petroleum the Utuk~~k Kivcr and Ilisr%l>pvi~rl~nc~~tCreek in scaitrclj of a rtlurtl through possibilities of tlre area. The region had been only partly covered the DcLol~g >lourltijins. 'The p.lrty crossed the Colvillt. Kiver, traveled by rapid geologic reconnaissance during the earlier explorations sr~ut11w:ird to Ldke Nuluk. port;ljied across the divide to the Ninliuktuk of 1924-1926. Kiver, and co~~tinucddown the Noatilk Hiver to its moutlt. Very little The project was srlpt~rvisedby (:<,(,rgt.0. I:;ites jn 1547, by Ralph geologic work was accomplished a11 this trip because of logistic dl f f i- L. Miller in 1949-1950, and by George Gryc from 1951 to 1953. cultics. During field studies which covered about 70 percent of the area. In April and flay, 1925, a U.S. Geological Survey party under the geology was mapped on available aerial photographs, taken I:erald Fitzgerald, topographic engineer, with Walter R. Smith, Geologist, by the U.S. Air Force. These cover the entire map area and consist of asce~ided the Kugururok River by dog team from che Moatak River, portaged trimetrogon photographs flown in 1943, 1947, and 1949, and vercical across tlie divide to OtukoL Kiver drainage, and reached the upper Col- photographs of approximately 1:20,000 scale flown in 1948 and 1950. ville Xivar. The geology and topography along the route were mapped, Low-angle oblique photographs along portions of the upper Kukpowruk, and the parry continued down the Colville River by canoe. Kokolik, Utukok, Colville, and Nuka Rivers were taken by the U.S. In Hay and June, 1926, a U.S. Ceological Survey party under Phillip . Navy in 1949. In addition, the photographs were used for photogeologic S. Smith made an overland journey by dog team from Kivalina, crossing interpretation beyond the limits of field control and, to some extent, the headwaters of the Kukpuwcuk Hiver to the upper Kokolik River. The to calculate structural and stratigraphic measurements. Data were party then canoed down theKokolikRiver. Geology and topography along transferred from photographs to 1:48,000- and 1:96,000-scale planimetric the route were mapped.