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Tectonic, Metamorphic, and Geographic Data for the Seward Peninsula, Alaska

By

Alison B. Till1, Julie A. Dumoulin1, Melanie B. Werdon2, and Heather A. Bleick1

2011

NORTON SOUND

Imuruk

Lake

Imuruk

Basin

Salmon

Lake

Killeak

Lakes

Devil

Mountain

Lakes Whitefish

Lake

Grantley Harbor

NORTON BAY

KOTZEBUE SOUND

Nome

Nome-Tayl or Road

Nom e-Teller Road

Nome-Council Roa d

Espenberg

Maars

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Alkaline

rocks

Alkaline

rocks

Devil

Mountain

maar

South

Killeak

maar

North

Killeak

maar

Felsic

volcanic

rocks

Whitefish

maar

Oonatut

Granite

Complex

Kougarok

Mountain

Virginia

Butte

stock

Nimrod

Hill

stock

Asses

Ears

stock

Kugruk

pluton

Alkaline

rocks

Quartz

Creek

pluton

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Crossfox

Butte

stock

Granitic rocks,

undifferentiated

Granitic rocks,

undifferentiated

Granitic rocks,

undifferentiated

Granitic rocks,

undifferentiated

Granitic rocks,

undifferentiated

Granite

Mountain

pluton

Kuzitrin

pluton

Lost Jim

Basalt

Alkaline

rocks

Darby

pluton

Darby

pluton

Bendeleben

pluton

Kachauik 

pluton

Windy

Creek

pluton

Dikes and

stocks

Dikes and

stocks

Pargon

pluton

Dikes and

stocks

Dikes and

stocks

Cenozoic

volcanic

rocks

Cenozoic

volcanic

rocks

Mount

Arathlatuluk

Sledge

Island

Kigluaik

pluton

Little

Diomede

Island

Fairway

Rock

King

Island

Black

Mountain

stock

Brooks

Mountain

stock

Tin Creek

stock

Cape

Mountain

stock

Ear

Mountain

stock

Lost River

Mines

Dry

Canyon

stock

10

10 0 10 20 30 40 50 Kilometers

0 10 20 30 40 Miles

Figure 2. Map of the Seward Peninsula, Alaska, showing locations and names of Quaternary, Tertiary, and 

Cretaceous igneous rocks. Cenozoic volcanic rocks, pale yellow; Late Cretaceous tin-bearing granites, dark 

yellow; compositionally diverse Early and Late Cretaceous rocks, brownish red; Early Cretaceous alkalic rocks, 

pale pink; dikes and stocks, magenta. 

168°00'

65°00'

66°00'

165°00'

162°00'

Kiwalik

Mountain

B e n d e l e b e n

M o u n t a i n s

K i g l u a i k M o u n t a i n s

D

a r b

y

M

o

u

n

t

a

i

n

s

Mount 

Arathlatuluk

McCarthys Marsh

York

Mountains

Death Valley

Mount

Osborn

Mount 

Bendeleben

Moon

Mountains

Grantley

Harbor

Fault

Zone

King Island

Fairway 

Rock

Little 

Diomede

Island

Sledge Island Nome

Cape Espenberg

Nome-Council

Road

Nome-Tell e r Road

Nome-Taylor Road

King Island

Sledge Island

Fairway 

Rock

Little 

Diomede

Island

Cape Deceit

Cape Nome

Imuruk

Lake

Imuruk

Basin

Grantley Harbor

K O T Z E B U E S O U N D

NORTON SOUND

N O R T O N

B A Y

Salmon

Lake

Killeak

Lakes

Devil

Mountain

Whitefish Lakes

Lake

Sinuk River

Fish River

Koyuk River

Nugnugaluktuk River

Goodhope

River

Serpentine River

Kuzitrin River

A

giapuk River

Koug

arok River

Noxapaga River

Kuzitrin River

BERING STRAIT

8

1

4

5,6

7

9

12,13

14

15

26

27

28

29

30

31,32

33

34 36 35

37 39 38

40

41

42

45

46 47,48 49

50

51

52,53

54

55

58,59,60,61,62,63,64

98

100

101

2

2

1

3

4

5

6

7

8

9

10,11

12

13 14

17

18,19

20,21

19

65

66,67

68,69,70

71,72

73

74

75

76

77

78

79

80

15,16

10

11

16

17

18

43

44

56

57

94

102

103

23

22

81

82

83,84 85

86

87,88

89 90

91

92,93

95

97

99

96

3

25

22

23,24

20,21

168°00'

168°00'

65°00'

66°00'

165°00'

165°00'

162°00'

162°00'

66°00'

65°00'

1

U.S. Geological Survey, Anchorage, Alaska, 2Alaska Division of Geological and Geophysical Surveys, Fairbanks, Alaska

A-6 A-5 A-4 A-3 A-2 A-1

B-6 B-5 B-4 B-3 B-2 B-1

C-6 C-5 C-4 C-3 C-2 C-1

D-6 D-5 D-4 D-3 D-2 D-1

162° 161° 160° 159°

66°

65°30’

65°

SHISHMAREF

168° 165° 162° 159°67°

66°

65°

64°

SHISHMAREF KOTZEBUE SELAWIK

TELLER BENDELEBEN CANDLE

NOME SOLOMON NORTON BAY

INDEX MAP SHOWING 1:250,000-SCALE QUADRANGLE NAMES AND LABELS FOR 

1:63,360-SCALE QUADRANGLES WITHIN EACH 1:250,000-SCALE QUADRANGLE

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Geology compiled by Alison B. Till (2008)

GIS database and digital cartography by Keith A. Labay 

and Heather A. Bleick

Edited by Theresa Iki

Cartography by Darlene A. Ryan

Manuscript approved for publication July 14, 2010

Shaded relief from National Elevation Dataset (NED) 42.7-meter Digital Elevation 

Models (DEMs)

Universal Transverse Mercator Zone 3N; 1927 North American Datum

Base layer for water from 1:250,000 quadrangles (1950–1955)

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3131

Sheet 2 of 2

Pamphlet accompanies map

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government.

For sale by U.S. Geological Survey, Information Services, Box 25286, 

Federal Center, Denver, CO, 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3131

LIST OF METAMORPHIC-TECTONIC ELEMENTS

York Terrane—Late Proterozoic (?) and Paleozoic sedimentary 

and metasedimentary rocks and minor Late Cretaceous 

tin-bearing granites; dominantly carbonate and siliciclastic 

lithologies, in which primary features are generally retained; 

fine-grained metasedimentary rocks are weakly foliated. 

Metamorphic and thermal history variable from unit to unit, 

and generally lower grade than Nome Complex. Tin granites 

intruded in shallow crustal settings. The generally brittle 

shallow and steeply-dipping structures in the area may have 

formed in shallow contractional settings, extensional settings, 

or both

Nome Complex—Late Proterozoic and Paleozoic metasedimentary and metaigneous rocks, metamorphosed during the 

Mesozoic

Nome Complex, central—Penetratively deformed and recrystallized schists with ductile fabrics; mineral assemblages 

record a blueschist-facies event that traversed lawsonitestable conditions and peaked at epidote-stable conditions; one 

eclogite-facies assemblage; blueschist-facies assemblages are 

variably overprinted by greenschist facies assemblages

Nome Complex, west-central—Weakly foliated metasedimentary and unfoliated metaigneous rocks that retain relict 

primary features; mineral assemblages in mafic rocks formed 

at pumpellyite-actinolite, greenschist, and blueschist facies 

(one locality)

Nome Complex, eastern—Penetratively deformed and 

recrystallized schists with ductile fabrics; protolith packages 

and metamorphic fabrics identical to Nome Complex in 

central Seward Peninsula; mineral assemblages in most of the 

area are characteristic of greenschist facies, but slightly 

higher grade assemblages occur in the vicinity of Kiwalik 

Mountain. Lack of high pressure metamorphic minerals may 

be significant or a product of poor exposure and limited 

sampling. Metamorphic history of this block may not be 

consistent throughout and the block may be cut by unrecognized faults

Nome Complex, northern—Weakly foliated metasedimentary 

and unfoliated metaigneous rocks; mineral assemblages in 

small metagabbro bodies are variable; some show weak 

greenschist-facies overprint, others show pervasive static 

overgrowth of greenschist-facies minerals over igneous 

minerals; one contains pseudomorphs after blue amphibole

High grade metamorphic and associated igneous rocks—

Amphibolite and granulite-facies metamorphic rocks and 

associated Cretaceous plutons; penetratively deformed 

metasedimentary and metaigneous schist and gneiss with 

complex metamorphic histories; aluminum-rich lithologies 

show early development of kyanite-stable mineral assemblages succeeded by sillimanite-stable, lower-pressure 

assemblages. Lithologies rich in iron and aluminum retain 

early, relatively high pressure aluminosilicate plus orthoamphibole assemblages (>5kb) that are overprinted by relatively 

lower pressure cordierite plus staurolite or garnet assemblages (<5kb). Timing of peak metamorphism and exhumation may not be the same in Kigluaik, Bendeleben, and Darby 

mountain ranges. Kigluaik and Bendeleben ranges formed in 

the Tertiary and are bounded by active faults

Grantley Harbor fault zone—Weakly metamorphosed metasedimentary rocks with stronger deformational fabrics than those 

in the western Seward Peninsula, but weaker deformational 

fabrics than the Nome Complex. Primary sedimentary 

features locally preserved

Angayucham terrane—Mafic, ultramafic, and tonalitic rocks 

juxtaposed along a series of vertical faults with minor slivers 

of Nome Complex carbonate rocks; mafic rocks are 

volumetrically dominant, contain blueschist and albiteepidote-amphibolite facies metamorphic assemblages, and 

exhibit weakly foliated to mylonitic fabrics

Conglomerate and sandstone—Unmetamorphosed Cretaceous 

(?) carbonate-clast conglomerate and sandstone, likely related 

to marine sedimentary rocks of the Yukon-Koyukuk basin; 

Tertiary (?) sandstone and coal

Yukon-Koyukuk basin—Folded and faulted Mesozoic volcanic 

and marine sedimentary rocks and associated plutons.

Cenozoic volcanic rocks—Basalt cinder cones, flows, and large 

maar volcanoes with associated pyroclastic rocks

Kugruk fault zone

METAMORPHIC MINERAL KEY

Lawsonite

Pseudomorph after lawsonite

Glaucophane

Glaucophane and pseudomorph after lawsonite

Pseudomorph after glaucophane

Pseudomorph after glaucophane and pseudomorph after 

lawsonite

Crossite or glaucophane

Crossite or glaucophane and lawsonite

Eclogite

Aluminous rock with mineral assemblage that contains relicts 

of the reaction aluminosilicate + orthoamphibole = 

cordierite + garnet or staurolite (decrease in pressure) 

Aluminous rock with mineral assemblage that contains relicts 

of the reaction orthoamphibole + kyanite = cordierite + 

garnet or staurolite (decrease in pressure)

Pelitic rock crystallized at temperatures above the second 

sillimanite isograd and aluminous rock with mineral 

assemblage that contains relicts of the reaction aluminosilicate + orthoamphibole = cordierite + garnet or staurolite (decrease in pressure)

Pelitic rock crystallized at temperatures above the second 

sillimanite isograd

Kyanite

Andalusite

Approximate position of second sillimanite isograd; teeth 

towards higher-grade rocks 

CONODONT COLOR ALTERATION INDEX (CAI) VALUES

[See appendix, including tables A-1 and A-2 in pamphlet, for more information]

Not determined

1.5–2.5

Minimum 1.5–2.5 and maximum 3.0–3.5

3.0–3.5

Minimum 1.5–2.5 and maximum 4.0–4.5

Minimum 3.0–3.5 and maximum 4.0–4.5

4.0–4.5

5.0–5.5

Minimum 5.0–5.5 and maximum 6.0–6.5

6.0–6.5

Minimum 5.0–5.5 and maximum 7.0–8.0

Minimum 6.0–6.5 and maximum 7.0–8.0

7.0–8.0

MAP SYMBOLS

K-Ar, 40Ar/39Ar, and Rb-Sr sample location; see table 2 for 

age data 

U-Pb zircon sample location; see table 3 for age data

Mountain

1:250,000-scale quadrangle boundary 

Contact—Depositional, intrusive, or metamorphic, as shown on 

sheet 1

Fault—Dotted where concealed, as shown on sheet 1

Contact—Metamorphic-tectonic elements

Major fault or tectonic subdivision boundary—Dashed where 

concealed or approximately located

Road