(a) · the architecture of oceanic plateaus revealed by the volcanic stratigraphy of the accreted...

0 10 20 kmA A

8000'4000'

Sea level EUREKACREEK

FAULT

Paleozoic

mafic/ultramafic

Mapped units

Inferred units

Gabbroic rocks

Ultramafic rocks

Map legend

massive basalt

pillow basalt

basalt undifferentiated

gabbro

mafic/ultramafic

nT59000

56300

57000

56800

55800

56500

56600

56400

56700

56900

57200

57500

mafic rocks

ultramafic

Paleozoicsediments

&

A

RI C

HA

RD

SON

(b)

(a)

(c)

subaerial basalt flows

? ?

A

The Architecture of Oceanic Plateaus Revealed by the Volcanic Stratigraphy of the Accreted Wrangellia Oceanic Plateau [Geosphere]. Andrew R. Greene, James S. Scoates, Dominique Weis, Erik C. Katvala, Steve Israel, and Graham T. Nixon

1

Andrew

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Supplementary map 1. Geology and magnetic map of the Amphitheater Mountains, Alaska (location shown in Figure 3). (a) Color shadow total magnetic field map of part of the Amphitheater Mountains. A summary of the magnetic survey is provided in Burns and Clautice (2003) and the full color shadow map is presented in Burns et al. (2003). Details of the data acquisition, interpretation, publications, and data formats are provided in Prichard (2003). The surveys (1995 and 2002) mapped the magnetic and conductive properties of the area to detect conductive mineralization. This was accomplished by using a DIGHEM(V) multi-coil, multi-frequency electromagnetic system, supplemented by a high sensitivity cesium magnetometer and GPS system (Burns and Clautice, 2003). The rocks with the highest magnetic susceptibility (Fe-rich magnetic minerals; mafic and ultramafic rocks) dampen the magnetic signal and produce highs and lows, measured in nanoTeslas (nT). The high nT values are purple and orange in color, indicating magnetic rocks, and the low values are blue and green. The purple and red areas are assumed to be coincident with mafic and ultramafic rocks, and the blue areas are inferred to be Paleozoic sediments. (b) Generalized geology of the Nikolai Formation and related plutonic rocks in the Amphitheater Mountains. Five main field areas are outlined with numbered boxes (denoted in map). Map derived Nokleberg et al. (1992) and digital compilation of Wilson et al. (1998). Inferred units from Burns et al. (2003). (c) Schematic cross-section of Amphitheater Mountains from A to A' (shown in panels a and b), adapted from Nokleberg et al. (1985).

DO

NJE

KR

IVE

R

SLIMS

RIVER

KLUANE

MUSHLAKE

HainesJunction

0 50 km

Scale

KLUTLAN

GLA

CIE

R

S TE L I A S

MO

U N T A I NS

KLUANE

RANGES

ALASKAYUKON

GLACIERSEWARD

LAKE

61° N

62° N140° W

140° W

DENA L I F AU L T

AL

SE

KR

I VE

R

Sheep Mtn.

HalfbreedCreek

Nutzotin

Mountains

D U K E R I V E R F A U L T

BB

Nikolaisubaerial flows

pillow breccia(with local pillows)

bioclastic limestone, locally ~40 mchert, shale, and limestone(Hasen Creek Fm.), locally ~300 m

(<70 m)

Penn

sylv

ania

nto

Early

Perm

ian

Late

Tria

ssic

Jura

ssic

NIKOLAI FORMATION

CHITISTONE LIMESTONE

NIZINA LIMESTONE

Tatamagouche succession

MCCARTHY FM

SKOLAI GROUP

subaerial basaltic flows

limestone, dolomite

shale with ‘Daonella beds’

arc-derived volcanic rocks

thin-bedded limestone, chert, shale

(phyllite, pebbleconglomerate)

(~1000 m exposed thickness)

pillow breccia, minor pillow basalt

(Station Creek Fm.)

lower flow member

mafic and ultramafic rocks

upper volcaniclastic member

-extensively faulted-

?

(shale, limestone)


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Andrew

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Supplementary map 2. Map and stratigraphic column of the Nikolai Formation in southwest Yukon. (A) Simplified map of southwest Yukon showing the distribution of the Nikolai Formation (black; after Israel, 2004; Israel and Van Zeyl, 2004; Israel et al., 2005). Stratigraphic column for Kluane Ranges derived from Read and Monger (1976) Israel et al. (2006), Israel and Van Zeyl (2005), and fieldwork.


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Andrew

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Supplementary map 3. Simplified map of southeast Alaska showing the distribution of Triassic basalts and sedimentary rocks. Some may be correlative with Wrangellia flood basalts while others are part of the Alexander Terrane. Orange line is Alaska-BC border. Purple lines are faults. See text for description of units. Map adapted from a map provided courtesy of Brew (written comm., 2007). Inset shows location of map in northwestern North America.

Volcanic stratigraphy the Karmutsen Formation

Early to Middle JurassicIsland Plutonic Suite

Subaerial flows

Hyaloclastite

Pillowed and unpillowed flows

Flood basalts,undifferentiated

Road

High-Mg pillow lava

Suspected high-Mg pillow lavaOlivine-bearing flow

High-Mg pillow breccia

Attitude of bedding andflow contactsVolcanic lamination(amygdules, drainage features)

(MgO >10 wt %)

(no geochemistry)

(MgO <10 wt %)

Olivine-bearing pillow lava(MgO <10 wt %)

(MgO >10 wt %)

Synclinal fold axis


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Andrew

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Supplementary map 4. Generalized geology of the Karmutsen Formation on northern Vancouver Island in the Port Alice-Robson Bight area. Map derived from Nixon et al. (2008). Sample locations and units shown in the legend. Stratigraphic column for this area is shown in Figure 5.

REFERENCES CITED Brew, D. A. C., 2007, written comm., Unpublished map showing the distribution of the

Late Triassic Wrangellia, Hyd Group, and Perserverance group rocks in southeastern Alaska: scale 1:600,000, based on Brew, D. A. C. (Compiler), Unpublished bedrock geologic map of southeastern Alaska.

Burns, L. E., U. S. Bureau of Land Management, Fugro Airborne Surveys, and Stevens Exploration Management Corp., 2003, Color shadow magnetic map of the southern Delta River area, east-central Alaska: Alaska Division of Geological and Geophysical Surveys, Geophysical Report 2003-5-1C, 2 sheets, scale 1:63,360.

Burns, L. E. and Clautice, K. H., 2003, Portfolio of aeromagnetic and resistivity maps of the southern Delta River area, east-central Alaska: Alaska Division of Geological and Geophysical Surveys, Geophysical Report 2003-8, 16 p.

Israel, S., 2004, Geology of Southwestern Yukon: Yukon Geological Survey Open File 2004-16, scale 1:250,000.

Israel, S., Tizzard, A. and Major, J., 2005, Geological map of the Duke River area (parts of NTS 115G/2, 3, 5, 6, 7), Yukon: Yukon Geological Survey, Open File 2005-11, scale 1:50,000.

Israel, S., Tizzard, A. and Major, J., 2006, Bedrock geology of the Duke River area, parts of NTS 115G/2, 3, 4, 6 and 7, southwestern Yukon, in Emond, D. S., Bradshaw, G. D., Lewis, L. L. and Weston, L. H., eds., Yukon Exploration and Geology 2005: Yukon Geological Survey, p. 139-154.

Israel, S. and Van Zeyl, D. P., 2004, Preliminary geological map of the Quill Creek area (parts of NTS 115G/5, 6, 12), southwest Yukon: Yukon Geological Survey, Open File 2004-20, scale 1:50,000.

Nixon, G. T., Laroque, J., Pals, A., Styan, J., Greene, A. R. and Scoates, J. S., 2008, High-Mg lavas in the Karmutsen flood basalts, northern Vancouver Island (NTS 092L): Stratigraphic setting and metallogenic significance, in Grant, B., ed., Geological Fieldwork 2007: B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 2008-1, p. 175-190.

Nokleberg, W. J., Aleinikoff, J. N., Dutro, J. T. J., Lanphere, M. A., Silberling, N. J., Silva, S. R., Smith, T. E. and Turner, D. L., 1992, Map, tables, and summary fossil and isotopic age data, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U. S. Geological Survey Miscellaneous Field Studies Map 1996-D, scale 1:250,000.

Nokleberg, W. J., Jones, D. L. and Silberling, N. J., 1985, Origin and tectonic evolution of the Maclaren and Wrangellia terranes, eastern Alaska Range, Alaska: Geological Society of America Bulletin, v. 96, p. 1251-1270.

Prichard, R. A., 2003, Project report of the airborne geophysical survey for the southern Delta River area, east-central Alaska: Alaska Division of Geological and Read, P. B. and Monger, J. W. H., 1976, Pre-Cenozoic volcanic assemblages of the Kluane and Alsek Ranges, southwestern Yukon Territory: Geological Survey of Canada, Open-File Report 381, 96 p.

Read, P. B. and Monger, J. W. H., 1976, Pre-Cenozoic volcanic assemblages of the Kluane and Alsek Ranges, southwestern Yukon Territory: Geological Survey of Canada, Open-File Report 381, 96 p.

Wilson, F. H., Dover, J. D., Bradley, D. C., Weber, F. R., Bundtzen, T. K. and Haeussler, P. J., 1998, Geologic map of Central (Interior) Alaska: U. S. Geological Survey, Open-File Report 98-133-A, http ://wrgis.wr.usgs.gov/open-file/of98-133-a/.


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(a) · the architecture of oceanic plateaus revealed by the volcanic stratigraphy of the accreted...

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