UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY

BULLETIN 1028 PLATE 23

178°26'00" 27'30" 30'00" 32'30" 35/00" 178°36'00"
52°00'30" a cs 52°00'30"
2 31 34 ",
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26
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breakers 2 &
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51°53'00" 51°53'00"
Een 27/30" 30°00" ae INTERIOR GEOLOGICAL SURVEY, WASHINGTON. B.C, apo aEoaa
Topography from U. S. Coast and Geodetic Survey Topographic Geology by G. L. Snyder and R.A. Robie, 1951
Manuscript T-8256. Universal Transverse Mercator
Projection, Zone 60, 1927 North American datum
BB
A ‘ At
3000/4 7
2500/4

1000'4

5004

Sea level

500’.

\

NX
/ tc
\

—_——
= —~,

_
————

3500".
|
3000'4

250074

1500’.
1000’
500".
Sea level =

500".

GEOLOGIC MAP AND SECTIONS OF LITTLE SITKIN ISLAND, ALASKA

Seale 1:20 000
0

1 Mile

Contour interval 50 feet
with supplementary contours at 25 foot intervals
Datum is mean sea level
Shoreline is line of mean high water

EXPLANATION

SURFICIAL DEPOSITS

Qal
Alluvium Colluvium Eolian deposits
Sand, gravel, and boulders Boulders and boulder Boulders and bouldery Dune sand
debris in slope wash,
talus, landslide, and
and boulders, Qb2 mudflow deposits
VOLCANIC DEPOSITS
Little Sitkin dacite
Sequence Lica dacite flows; West Cove

of low-silica
Mad wilh youngest major eruption. Pratt
ated with youngest
Point member, Qip; rhyodacite flow unit.
Low-silica dacite flows with minor amounts
asyociated pyroclastic, material, Q's.
joundaries of individual flow units shown
in most areas

CONTACT OBSCURE

Dacitic ash and piimice and dacitic and
andesitic pyroclastic debris

MAJOR UNCONFORMITY
FORMATION OF CALDERA TWO

Double Point dacite
high-silica dacite 8 containing
reg) mmlartteie cichusion® of labradoris
andesite; ‘minor amounts of associated
material. Boundaries of indivic
flow units shown in some areas

East Point formation
Sequence of andesite and basalt flows

RELATIONS UNKNOWN
UNCONFORMABLE ON WILLIWAW COVE FORMATION

Sitkin Point formation
Weexiaats lastic material ;
gra; dacite- boulder tuff
a ie tuff, and pumiceous tuff

MAJOR UNCONFORMITY
FORMATION OF CALDERA ONE

Williwaw Cove formation

uence of andesite and bandaite flows with
ee ests of basalt and Meta ‘flows =

and major amounts o, lastic material.
Bikes gf andesite ond becatt asalt shown in some
areas

Contact

Long dash where kere apprecinatsly located,
short das ee

—SS ae ee ae ee
U

Fault, showing direction of dip

Long dash where approximately located, short
dash where inferred, dotted where conces
by younger deposits. U, upthrown ride, B
wnthrown side

90
Vertical fault

Areas of kaolinized, silicified,
‘and pyritized rock

kx
Active fumarolic areas, major and minor

eee

Strike and dip of beds
=
Approximate direction and amount of dip of beds
@
Horizontal beds

210
Location and number of chemically analyzed
specimen

Prominent shore bench

Offshore rock awash

a6

Thick kelp in season

QUATERNARY

QUATERNARY

TERTIARY OR
QUATERNARY