SURFICIAL GEOLOGIC MAP OF THE BETTLES QUADRANGLE, ALASKA · Surficial geologic map of the Bettles...
Transcript of SURFICIAL GEOLOGIC MAP OF THE BETTLES QUADRANGLE, ALASKA · Surficial geologic map of the Bettles...
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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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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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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Fandeposits
Alluvium Terrace deposits Colluvial deposits Sand, silt, and organicdeposits
Lacustrine andglaciolacustrine deposits
Other glacial deposits
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Mainphase
Latephase Sagavanirktok
Riverglaciation
PhaseI
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AnaktuvukRiverglaciation
Itkillikglaciation
Pleistocene
Holocene
TERTIARY(?)
QUATERNARY
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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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