MISCELLANEOUS FIELD STUDIES MAP MF–2409Version 1.0

Surficial geologic map of the Bettles quadrangle, Alaska

Pamphlet accompanies map

ALASKA

QUADRANGLE LOCATION

SCALE 1: 250 000

0 25 KILOMETERS20151055

0 20151055 25 MILES

SURFICIAL GEOLOGIC MAP OF THE BETTLES QUADRANGLE, ALASKABy

Thomas D. Hamilton2002

Geology by W.W. Patton, Jr. and T.P. Miller, 1966-70; R.A. Kreig and R.D. Reger, 1972-75; and T.D. Hamilton, 1962-66, 1970-74, and 1983-87Digital representation by Earth Satellite Corporation, 1999; Greenhorne & O'Mara, 1999; K.A. Labay, Raytheon ITSS contractor, 2000-2002Edited by Jane S. CienerApproved for publication September 30, 2002

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary between electronic plotters and between X and Y dimensions on the same plotter, and paper may change size due to atmospheric conditions; there-fore, scale and proportions may not be true on plots of this map.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center Denver, CO 80225. 1-888-ASK-USGS

Digital files available on World Wide Web at http://geopubs.wr.usgs.gov

Base from U.S. Geological Survey, 1956; limited revisions, 1984Universal Transverse Mercator, zone 5

U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

CONTOUR INTERVAL 200 FEETNATIONAL GEODETIC VERTICAL DATUM OF 1929

1984 MAGNETIC DECLINATION AT SOUTH EDGE OF SHEET VARIES FROM 25 TO 27 EAST

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LIST OF MAP UNITS[See pamphlet for detailed descriptions. Units queried where uncertain.]

FAN DEPOSITS

Fan deposits—Range from coarse gravel (mountain valleys) to gravelly sand and silt (Koyukuk basin)

Inactive fan deposits

Sandy fan deposits—Dominantly sand- to granule-sized

Fan-delta deposits—Alluvial-fan deposits that grade distally into lacustrine beds

ALLUVIUM

Alluvium, undivided—Coarse gravel to sandy fine gravel and gravelly sand. Locally includes fan and low terrace deposits too small to map separately

Fine-grained alluvium—Along slow-moving streams

Sandy alluvium—Along slow-moving streams

Modern alluvium—Gravel and sandy gravel; generally unvegetated

Low alluvial terrace deposits—Gravel and sandy gravel, mantled with thin silt, sand, turf, and peat

Gravel deposits, other—Gravelly erosion remnants of obscure composition and origin

Quartzose gravel of inferred Tertiary age—Rounded quartz pebbles and small cobbles in nearly pure quartz sand

TERRACE DEPOSITS

Terrace deposit—Alluvial gravel; commonly intergrading or mantled with fluvial, deltaic, lacustrine, or organic deposits

Terrace gravel—Alluvial gravel, sandy gravel, and floodplain deposits; commonly mantled by loess, muskeg, and thaw-lake sediments

A. Terrace deposits along Henshaw Creek

Terrace deposit, low-level (late Pleistocene)—Alluvial gravel and sandy gravel, forming terraces 8-14 m high that decrease in height downstream

Terrace deposit, intermediate-level (middle Pleistocene)—Gravel and finer sediments, forming terraces up to 35 m high that decrease in height downvalley

Terrace deposit, high-level (early Pleistocene)—Gravel and finer sediments, forming terraces up to 75 m high that decrease in height downvalley

B. Terrace deposits along Jim River

Terrace gravel, low-level (late Pleistocene)—Gravel and sandy gravel, forming terrace remnant 2-3 m above river

Terrace gravel, intermediate-level (late middle Pleistocene)—Gravel and sandy gravel, forming terraces 25-30 m high

Terrace gravel, high-level (early middle Pleistocene)—Gravel and sandy gravel, with thick (5 m or more) silt cover, forming dissected terraces about 50 m high

C. Terrace deposits along Koyukuk River (upvalley from Allakaket)and South Fork Koyukuk River

Terrace deposit, low-level (late Pleistocene)—Sandy gravel, with some finer-grained deposits; muskeg cover locally thick and continuous. Forms terraces 5-10 m high that decline in height downvalley

Terrace deposit, intermediate-level (late middle Pleistocene)—Terrace deposits about 20-25 m high with muskeg cover locally thick and continuous

Terrace deposit, high-level (middle Pleistocene)—Terrace deposits about 40 m high along South Fork

D. Terrace deposits along Koyukuk River below Allakaket

Terrace gravel, low-level (late Pleistocene)—Alluvial gravel and sandy gravel, forming terraces 8-10 m high

Terrace deposit, low-level (late Pleistocene)—Sandy gravel, with some finer-grained deposits. Near mouth of Kanuti River

Terrace gravel, high-level (early Pleistocene)—Alluvial gravel with silt cover, forming terrace remnants 50-60 m high

Terrace gravel, highest-level (early Pleistocene?)—Oxidized gravel capped by thick loess. Forms terrace remnants up to 120 m above Koyukuk River

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als

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fi

fsa

fd

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tgB2

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tgD3

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tdA3

tdA2

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COLLUVIAL DEPOSITS

Colluvium, undivided—Mixed solifluction deposits and talus rubble

Solifluction deposits—Poorly sorted stony silt and organic silt

Flow deposits—Lobes of angular rock rubble in abundant silty matrix

Landslide deposits—Angular rubble below detachment scars and slide tracks

Rock-glacier deposits, active—Lobes of coarse angular rock debris with matrix of ice-rich silt and fine rubble

Rock-glacier deposits, inactive—Coarse angular rock debris lacking interstitial ice. Surfaces weathered and partly vegetated

Talus rubble, inactive—Angular rock debris along lower walls of mountain valleys. Surfaces weathered and partly vegetated

SAND, SILT AND ORGANIC (MUSKEG) DEPOSITS

Dune sand—Fine to medium sand, commonly forming parabolic ridges

Dune sand, younger and older components—Where partly reactivated by wind

Sand deposits—Sand with granules and sparse small pebbles; in grus-filled basins

Ice-rich silt deposits—Silt, commonly with ice-wedge polygons, in depressions and along valley centers

Upland silt deposits—Silt, organic silt, and slightly stony silt; commonly grades downslope into solifluction deposits

Muskeg—Organic deposits more than 1-2 m thick where drainage restricted

LACUSTRINE AND GLACIOLACUSTRINE DEPOSITS

Beach deposits—Sand and platy fine gravel; locally shoved into ridges

Lacustrine deposits—Fine sediments, grading into sand and gravel near former shorelines and river mouths

Lacustrine deposits, low-level (late to middle Pleistocene)—Stratified silt and related deposits. Overlain by muskeg with abundant lakes

Lacustrine deposits, high-level (early Pleistocene)—Stratified silt and related deposits forming poorly drained surfaces above bluffs 30 m high

Glacial-lake deposits, undivided—Stratified silty deposits of uncertain age

Glacial-lake deposits of Sagavanirktok River age (middle Pleistocene)— Fine sediments grading into sand to fine gravel near former stream mouths

Glacial-lake deposits of Anaktuvuk River age (early Pleistocene)—Stratified stony silt, forming erosion remnants that generally bear thick cover of ice-rich silt with numerous thaw ponds

OTHER GLACIAL DEPOSITS

Drift, undivided—Glacial deposits of uncertain age

Itkillik glaciation (late Pleistocene)

Drift of Itkillik Phase I—Compact bouldery till with local ice-contact sand and gravel

Drift of Itkillik Phase IA—Outermost moraine and associated drift of Itkillik complex

Kame and kame-terrace deposits—Unusually thick and extensive water-washed sand and gravel

Outwash of Itkillik age, undivided—Valley trains of sandy gravel

Outwash of Itkillik Phase I—Sandy gravel associated with drift of Itkillik I age

Outwash of Itkillik Phase IA—Outwash train that originates at moraine of Itkillik IA age

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s

fl

ls

rga

rgi

tri

ds

ds2 ds1

sa

si

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gl

sgl

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Sagavanirktok River glaciation (middle Pleistocene)

Drift of Sagavanirktok River age—Bouldery till and ice-contact gravel, generally covered by thick loess, solifluction, and muskeg deposits. Weathered gravel and erratic boulders exposed on some ridges and knolls

Drift of Sagavanirktok River late phase—Till and ice-contact deposits

Outwash of Sagavanirktok River age—Sandy gravel associated with end moraines of Sagavanirktok River age

Anaktuvuk River glaciation (early Pleistocene)

Drift of Anaktuvuk River age—Bouldery till, with some coarse gravel

Kame terrace(?)—Linear gravel-rich deposit

Outwash of Anaktuvuk River age—Gravel and sandy gravel, associated with moraines of Anaktuvuk River age

Gunsight Mountain glaciation (Tertiary?)

Drift of Gunsight Mountain age—Till and ice-contact deposits, forming isolated erosion remnants

MAP SYMBOLS

Contact—Dashed where approximately located or inferred

Fault—Expressed in Quaternary sediments. Dashed where approximately located or inferred. Arrows indicate direction of lateral motion

Drainage channel—Abandoned or underfit

Crest of morainal ridge

Headwall scarp of debris flow

Direction of glacier flow across topographic divide

Direction of ice movement or meltwater drainage— Associated with ice-scoured bedrock

Former glacial-lake outlet or drainage diversion

U-shaped pass—Where glacier crossed topographic divide

Spring

Pingo

Bedrock, undifferentiated

Bedrock—Exposed along canyon walls or margin of river terrace

Near-surface bedrock—Generally covered by 1-2 m of sod, peat, loess, solifluction deposits, and rock debris; usually completely vegetated

Pediments—North and east of Sithylemenkat Lake. Bear thin colluvial cover

Altiplanation terrace

Surface and subsurface lacustrine deposits

Heavily eroded surficial unit

Lake—M, Minnkokut; S, Sithylemenkat; T, Todatonten

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CORRELATION OF MAP UNITS

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id1

id1A

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Fandeposits

Alluvium Terrace deposits Colluvial deposits Sand, silt, and organicdeposits

Lacustrine andglaciolacustrine deposits

Other glacial deposits

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fl

Mainphase

Latephase Sagavanirktok

Riverglaciation

PhaseI

PhaseII

GunsightMountainglaciation

AnaktuvukRiverglaciation

Itkillikglaciation

Pleistocene

Holocene

TERTIARY(?)

QUATERNARY

A B C D

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TERRACE DEPOSIT COLUMNSU. Age unassignedA. Henshaw CreekB. Jim RiverC. Koyukuk River + South Fork Koyukuk RiverD. Koyukuk River west of Allakaket

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