Open-File Report 2009-1254 U.S. Department of the Interior Sheet 2 of 2 U.S. Geological Survey Pamphlet accompanies map '02°761 '01°761 '00°761 LIST OF METAMORPHIC-TECTONIC ELEMENTS HIGH GRADE METAMORPHIC AND ASSOCIATED O<t Qs Ol Nome Complex, west-central – Weakly foliated metasedimentary O<l O<l IGNEOUS ROCKS – Amphibolite and granulite-facies O<l O<l Ol Ols Ols YORK TERRANE – Late Proterozoic (?) and Paleozoic sedimentary and unfoliated metaigneous rocks that retain relict primary features; and metasedimentary rocks and minor Late Cretaceous tin-bearing mineral assemblages in mafic rocks formed at pumpellyite-actinolite, metamorphic rocks and associated Cretaceous plutons; penetratively Qs greenschist, and blueschist facies (one locality) deformed metasedimentary and metaigneous schist and gneiss with Oal granites; dominantly carbonate and siliciclastic lithologies, in which Oal primary features are generally retained; fine-grained Nome Complex, eastern – Penetratively deformed and complex metamorphic histories; aluminum-rich lithologies show Ol early development of kyanite-stable mineral assemblages succeeded Ol 17 metasedimentary rocks are weakly foliated. Metamorphic and recrystallized schists with ductile fabrics; protolith packages and Ol Ols 165°00' by sillimanite-stable, lower-pressure assemblages. Lithologies rich in O<p Ols thermal history variable from unit to unit, and generally lower grade metamorphic fabrics identical to Nome Complex in central Seward Oal Qs Peninsula; mineral assemblages in most of the area are characteristic iron and aluminum retain early, relatively high pressure Ktg than Nome Complex. Tin granites intruded in shallow crustal Ols Ol aluminosilicate plus orthoamphibole assemblages (>5kb) that are Cape Espenberg settings. The generally brittle shallow and steeply-dipping structures of greenschist facies, but slightly higher grade assemblages occur in Ol the vicinity of Kiwalik Mountain. Lack of high pressure overprinted by relatively lower pressure cordierite plus staurolite or Ol Ol Oal in the area may have formed in shallow contractional settings, Ol metamorphic minerals may be significant or a product of poor garnet assemblages (<5kb). Timing of peak metamorphism and 65°30' Ol extensional settings, or both Ols exhumation may not be the same in Kigluaik, Bendeleben, and Ol NOME COMPLEX – Late Proterozoic and Paleozoic exposure and limited sampling. Metamorphic history of this block Darby mountain ranges. Kigluaik and Bendeleben ranges formed in Ols metasedimentary and metaigneous rocks, metamorphosed during the may not be consistent throughout and the block may be cut by SOul the Tertiary and are bounded by active faults Jurassic unrecognized faults GRANTLEY HARBOR FAULT ZONE – Weakly metamorphosed Nome Complex, central – Penetratively deformed and Nome Complex, northern – Weakly foliated metasedimentary and SOdl metasedimentary rocks with stronger deformational fabrics than recrystallized schists with ductile fabrics; mineral assemblages unfoliated metaigneous rocks; mineral assemblages in small 14 O<l those in the western Seward Peninsula, but weaker deformational Oal record a blueschist-facies event that traversed lawsonite-stable metagabbro bodies are variable; some show weak greenschist-facies Oal QTv fabrics than the Nome Complex. Primary sedimentary features Ol conditions and peaked at epidote-stable conditions; one overprint, others show pervasive static overgrowth of Ol locally preserved eclogite-facies assemblage; blueschist-facies assemblages are greenschist-facies minerals over igneous minerals; one contains Ktg Ol pseudomorphs after blue amphibole ANGAYUCHAM TERRANE – Mafic, ultramafic, and tonalitic QTv variably overprinted by greenschist facies assemblages Devil rocks juxtaposed along a series of vertical faults with minor slivers Ol Mountain Ols of Nome Complex carbonate rocks; mafic rocks are volumetrically Ol Whitefish Lakes dominant, contain blueschist and albite-epidote-amphibolite facies Lake QTv Ol QTv metamorphic assemblages, and exhibit weakly foliated to mylonitic Ols Killeak Lakes fabrics Oal QTv CONGLOMERATE AND SANDSTONE – Unmetamorphosed QTv 162°00' Cretaceous (?) carbonate-clast conglomerate and sandstone, likely 65°25' QTv related to marine sedimentary rocks of the Yukon-Koyukuk basin; Kv Tertiary (?) sandstone and coal DOx Ol YUKON-KOYUKUK BASIN – Folded and faulted Mesozoic k volcanic and marine sedimentary rocks and associated plutons. ktu Rive Qs Nug nugalu r DOx CENOZOIC VOLCANIC ROCKS Oal – Basalt cinder cones, flows, and large maar volcanoes with associated pyroclastic rocks '02°761 '01°761 '00°761 S O U N D B U E S Z E Ocs KUGRUK FAULT ZONE erp O T e iver K ntine R Kv Kv METAMORPHIC MINERAL KEY Cape Deceit Kv *# Lawsonite |d Qs DObm Oim Ksy 66°00' r QTv D_ks }|m Pseudomorph after lawsonite ve DObm Kv i D_ks |m DOx R DObm pe Glaucophane ho |m }|m 66°00' od |d Go |m DOx |m Glaucophane and pseudomorph after lawsonite Kv QTv |<g Ocs QTv Ddm Ksy Pseudomorph after glaucophane Ktg O<l QTv DOx QTv Oim Oim Ksy 20,21 DOx TKs TKv Pseudomorph after glaucophane and pseudomorph after lawsonite DOx Oim |m DOx DOx Od QTv DOx |d Ocs QTv |m 78 QTv Crossite or glaucophane |m Oim TKs |l 80 Ktg DOx Oim DOx Little Ddm DOx Diomede 79 Crossite or glaucophane and lawsonite Kgu Ocs Kgu Island Ocs DOx Ks }|m Kv Ddm Ksy Eclogite DOx |m }|m O<l 77 Od O<p |m Od Aluminous rock with mineral assemblage that contains relicts of Ds Ks Kv O<p O<l DOx Jt the reaction aluminosilicate + orthoamphibole = cordierite + |l Ds 75 DOx 15,16 QTv garnet or staurolite (decrease in pressure) Oal Ks Fairway O<p 74 Kku Ksy Aluminous rock with mineral assemblage that contains relicts of Kgu O<l Kv |gb O<l DOx Oim 65 102 Rock O<l Df Qs the reaction orthoamphibole + kyanite = cordierite + garnet or 1 Ds |m QTv O<t O<p Ds DOx staurolite (decrease in pressure) Oim BERING STRAIT O<l Oim 18,19 O<p Ocs Pelitic rock crystallized at temperatures above the second O<l Ds Ktg QTv 73 O<l Ol sillimanite isograd and aluminous rock with mineral Ml Ocs |m Ks O<t 2 Ol O<l assemblage that contains relicts of the reaction |gb O<l DSl Imuruk |d Ol O<l QTv |gb Ktg aluminosilicate + orthoamphibole = cordierite + garnet or Ols Lake 68,69,70 |m O<p OalYork DOx Jt QTv staurolite (decrease in pressure) 17 Oim 71,72 DOx Dg QTv Oal MountainsOl Ol Ocs QTv }|m Pelitic rock crystallized at temperatures above the second DOx |m Df Kv |gb Ocs 66,67 |d O<l 19 TKs Kiwalik sillimanite isograd O<l O<p Qlj Kbk Dg SOdl O<p Ol Ddm TKs 18 O<l SOul Jt Mountain Oal O<p Kgr Ol SOul 13|gb 76 r Ocs Ol 14 SOul Oal e 16 Kyanite Ktg Ol DOx v |d Ocs i Ocs Dg R Ols Ktg O<l QTv a Kbk |m |m Ol Ols Ols g Kgr Andalusite a }|m 103 Ol Ol p iver Df Ksy QTv a R 12 x Df |m o Kbk Approximate position of second sillimanite isograd; teeth towards n d 58,59,60,61,62,63,64 i a N r o t Kbk i higher-grade rocks R z O<l 10,11 r u e K 57 DOx r 9 v Ksy o QTv l i |<h QTv e y CONODONT COLOR ALTERATION INDEX (CAI) VALUES QTv R Kbk a n T o - k e Z |p DOx o DOx |m m r [See appendix, including tables A-1 and A-2 in pamphlet, for more t o a DOx N l g Ddm QTv u DOx |<m n t a i n s u M o u |m information] a o F |<h Gra DOx K n n A r tle b e Not determined o y H g Kgu e b a i l Kds 56 r rb a e a o p Qs d Kbk r u |<h n 17 Oim }|m H |p Ocs k |<h 1.5 - 2.5 R |<h e |<m Kgu y iv B e |<l e DOx Kv l r DOx t DOx Koyu n |<t TKs k Riv Minimum 1.5 - 2.5 and maximum 3.0 - 3.5 a er r K |<g 14 |<h |<hDeath Valley u Kp |m }|m G z r 52,53 4 it e Kbk |m rin Ri v Kgu Mount |<m |<h Kwc Oim Ddm 3.0 - 3.5 3 |<h 51 Bendeleben DOx 44 Kwc QTv QTv |np Kgu 54 50 |<h <v 11 Imuruk <n Ocs DOx QTv Minimum 1.5 - 2.5 and maximum 4.0 - 4.5 DOx TKs 8 15 12,13 Basin |<h Ocs Qs DOx Ocs QTv Kv Minimum 3.0 - 3.5 and maximum 4.0 - 4.5 |<h Kg McCarthy Marsh DOx Kd 7 Kg DOx DOx King Island Od 65°00' |<h |<h Kg Ds TKs DOx |d 4.0 - 4.5 <o DOx 10 |m |m 6 Kg 2 Sd 65°00' 5 49 Dcs Kgu |<h Kg 1 47,48 |<h }|m Oim 5.0 - 5.5 Kds 55 46 43 DOx <o 45 |<h DOx 28 |<h Mount DOx |d DOx <o Ds Ocs Ddm Minimum 5.0 - 5.5 and maximum 6.0 - 6.5 Kg Osborn |<h s <o 8 40 a i n s 101 98 94 D_bm Kdi n t DOx DOx n |d |m |<ho u <o 5,6 i TKs |m 9 M |m DOx 39 |<hi k 38 <n 100 a 6.0 - 6.5 a 37 <o Od t Kd Kgl u 33 Ocs _d Dcs |m Kg g <o n |m i 30 <n Salmon DOx Oim Oim Kdc |<h K 34 4 Ds |d 36 |<h u Minimum 5.0 - 5.5 and maximum 7.0 - 8.0 Ocs 31,32 35 Lake |m |<h 42 Kg |m o <o 27 DOx DOx 97 29 |<h Ocs Qs DOx Dcs |m Ds QTv M Kds Ddm Minimum 6.0 - 6.5 and maximum 7.0 - 8.0 |<h Ocs D_bm 41 DOx y }|m |<h 26 Oim Oim Ocs 23 b DOx r Dcs e r TKs 7.0 - 8.0 N iv 22 o R 96 a Ddm |m |m m 7 Oim Ds Dcs e DOx h s Mount D - Ocs T i DOx DOx F Qs e Ds Oim Arathlatuluk Ddm MAP SYMBOLS l l 168°00' e Ds r <n Oim Oim Moon 95 Ocs R Kds o DOx DOx Kds Mountains a 1 40 39 |mm DOx d 99 92,93 |m K-Ar, Ar/ Ar and Rb-Sr sample location; see table 2 for age Ocs Kkg Ddm Shaded relief from National Elevation Dataset (NED) 42.7-meter Digital Elevation Models (DEMs) 25 Ocs Ddm data r 91 e Kds "1 v Ds DOx Oim 82 Kkms U-Pb zircon sample location; see table 3 for age data Universal Transverse Mercator Zone 3N; 1927 North American Datum i Ocs 90 Dcs |m R k 89 Base layer for water from 1:250,000 quadrangles (1950-1955) u Dcs Ocs Ocs |m in <n Oim S 87,88 DOx Ocs Y Mountain DOx 3 |m DOx Ddm Ddm A DOx Ocs B Dcs DOx |<h 1:250,000-scale quadrangle boundary DOx DOx |m N Kkms O DOx 23,24 Ds Dcs86 D_bm T DOx Ddm R Contact – Depositional, intrusive, or metamorphic, as shown on Ocs DOx Ddm N O DOx |m Qs d Ocs Kd sheet 1 a DOx 81 o D_ks 22 R Ds Oim Dcs Ocs 85 |<h Fault – Dotted where concealed, as shown on sheet 1 Ocs Kkgm 83,84 Ds NATIONAL GEODETIC VERTICAL DATUM OF 1929 Kkms cil un Contact – Metamorphic-tectonic elements Co Ds e- Kgu m |m No Sledge Island Nome Major fault or tectonic subdivision boundary – Dashed where 159° <n Kkd concealed or approximately located 168° 162° |m 165° 67° |<h Road Cape Nome 20,21 Ds 162°00' KOTZEBUE SELAWIK 162° 161° 160° 159° SHISHMAREF 66° D-6 D-5 D-4 D-3 D-2 D-1 NORTON SOUND 66° C-6 C-5 C-4 C-3 C-2 C-1 Geology compiled by Alison B.