Quaternary and Engineering Geology in the Central Part of the Alaska Range

130 Pages·2012·34.88 MB·English

Quaternary and Engineering
Geology in the Central
Part of the Alaska Range
GEOLOGICAL SURVEY PROFESSIONAL PAPER 293

Quaternary and Engineering
Geology in the Central
Part of the Alaska Range
A. Quaternary geology of the Nenana River valley and
adjacent parts of the Alaska Range
By CLYDE WAHRHAFTIG
B. Engineering geology along part of the Alaska Railroad
By CLYDE WAHRHAF1'IG and ROBERT F. BLACK
GEOLOGICAL SURVEY PROFESSIONAL PAPER 293
of of
~-rtudies glacialf eatures and periods glaciation
of
in the Nenana River valley and landslides, icings,
attd frost heaving and settling affecting mainte
of of
nance track bed along 63 tniles the Alaska
Railroad
UNITED STATES GOVERNl\1ENT PRINTING OFFICE, WASHINGTON: 1958
UNITED STATES DEPARTMENT OF THE INTERIOR
FRED A. SEATON, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
For sale by the Superintendent of Documents, U. S. Government Printing Office
Washington 25, D. C.
CONTENTS
[The letters in parenthesrs preceding the titles de.3ignate the separate chapters]
rn~e
(A) Quaternary geology of the Nenana River valley and adjacent parts of the Alaska Range _____________________ _ 1
(B) Engineering geology along part of the Alaska Railroad_ ______________________________________________________ _ 69
Ill

Quaternary Geology of
the Nena11a River Valley
and Adjacent Parts of
...
the Alaska Range
By CLYDE vVAHRHAFTIG
QUATERNARY AND ENGINEERING GEOLOGY IN THE CENTRAL PART
OF THE ALASKA RANGE
GEOLOGICAL SURVEY PROFESSIONAL PAPER 293-A
of o;
A study glacialf eatures and periods
glaciation itt an area on the northern
of
ntargin the Cordilleran ice sheet itt
Alaska
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1958

CONTENTS
Page Pagt>
Abstract __________________________________________ _ 1 Dry Creek glaciation __________________ -_-_---------- 28
Introduction ______________________________________ _ 2 Deposits along the Nenana River ______________ -_-- 28
Purpose and scope of the report _________________ _ 2 Outwash gravel along the Nenana River_ _________ _ 29
History and methods of the investigation _________ _ 2 Glacial advances on other rivers _________________ _ 30
Geographic setting _________________________________ _ 5 Uplift and erosion during the interval between the
Physiographic divisions _________________________ ·- 5 Brmvne and Dry Creek glaciations _____________ _ 31
The. Nenana River _____________________________ _ 6 Healy glaciation ________________________ -_---------- 32
Climate ______________________________________ _ 7 Glacial deposits along the Nenana River_ _________ _ 32
Bedrock geology of the Nenana River valley __________ _ 7 Landforms along the Nenana River ______________ _ 33
Sedimentary rocks_________________ _ __________ _ 8 Lake deposits along the Nenana River ___________ _ 34
Birch Creek schist_______________ _ ________ _ 8 Outwash gravel along the Nenana River_ _________ ·- 36
Undifferentiated Paleozoic and Mesozoic rocks Glaeial deposits along other rivers _______________ - 40
south of Windy __________________________ _ 8 Uplift and erosion between the Dry Creek and Healy
Cantwell formation ________________________ _ 8 glaciations _____________________ -_-_---------- 41
Tertiary coal-bearing formation ______________ _ 9 Summary of history ______________________ -_----- 43
Nenana graveL ____________________________ _ 11 Riley Creek glaciation ____________________ --________ _ 45
Igneous rocks _________________________________ _ 12
Deposits along the Nenana River ________________ _ 45
Totatlanika schist __________________________ _ 12
Erosional landforms of glacial origin ______________ _ 47
Greenstone ________________________________ _ 12 Lake deposits _________________________________ _ 47
Granitic intrusive rocks _____________________ _ 13
Outwash gravel along the Nenana River __________ _ 48
Igneous rocks in the Cantwell formation ______ _ 14
Alluvium deposited by tributaries of the Nenana
Igneous rocks intruding the Birch Creek schist __ 14
River __________ ~---------------------------- 50
Summary of the Pleistocene history______________ _ __ _ 15 Deposits on other rivers ________________________ _ 51
Events leading to the ice advances _______________ _ 15
Carlo readv ance along the Nenana River _________ _ 52
Browne glaciation ______________________________ _ 16 Summary of history ____________________________ _ 55
Dry Creek glaciation ___________________________ _ 17
Healy glaciation _______________________________ _ 17 Deposits and landforms younger than the deposits of the
Riley Creek glaciation __________________________ _ 18 Carlo readvance _________________________________ _ 56
Preglacial erosion surfaee ___________________________ _ 18 Terraces ______________________________________ _ 56
Talus ________________________________________ _ 57
Exhumed unconformity at the base of the Tertiary
rocks _______________________________________ _ 19 Congeliturbate _________________________________ _ 58
Evidence of existence for the late preglacial Cenozoic Landslide deposits _____________________________ _ 59
erosion surface ______________________________ _ 20 Rock glaciers __________________________________ _ 60
Nature and topography of the preglacial eros~on Till __________________________________________ _ 61
surlace _____________________________________ _ 21 Glac~rs ______________________________________ _ 61
Subsequent deformation of the erosion surfaee _____ _ 22 Peat _________________________________________ _ 62
Browne glaciation __________________________________ _ 22 Aeolian deposits _______________________________ _ 62
Glacial deposits along the Nenana River __________ _ 22
Perennially frozen ground _______________________ _ 63
Glacial lobe defined by the glacial deposits ________ _ 26
Climatic history implied by the deposits __________ _ 64
Fplift of the Alaska Range since the Browne gla-
ciation _____________________________________ _ 27 Diastrophism _________________________________ _ 64
Glaciation on the Wood River_ __________________ _ 27 Literature cited ___________________________________ _ 65
Topography during the glaciation _______________ _ 28 Index ____________________________________________ _ 67
ILLUSTRATIONS
[Plates in pocket]
PLATE 1. Map of the Alaska Range behveen long. 147°30' and 150° W., showing bedrock geology.
2. Geologic map of parts of the Healy D-4 and D-5 quadrangles, showing Pleistocene deposits along the Nenana
River.
3. Geologic map of part of the Healy C-4 quadrangle, showing Pleistocene deposits along the Nenana River.
4. Geologie map of part of the Healy B-4 quadrangle, showing Quaternary deposits along the Nenana River.
VII
VIII CONTENTS
PLATE 5. Geologic map of part of the Fairbanks A-5 quadrangle, showing Pleistocene deposits along the Nenana River.
6. Map of the Alaska Range between long. 147°30' and 150° W., showing glacial features.
7. Generalized profile of terraces and glacial deposits along the Nenana River.
8. Detailed profile of terraces and glacial deposits along the Nenana River. Page
FIGURE 1. Index map of Alaska, showing location of area of this report_____________________________________________ 3
2. Index map of the central part of the Alaska Range, showing location of areas covered on individual geologic maps__ 4
3. Physiographic divisions of the central part of the Alaska Range___________________________________________ 5
4. Aerial view, showing superposed north-flowing streams crossing east-trending ridges and valleys______________ 20
5. Geography of the Alaska Range before the Browne glaciation____________________________________________ 21
6. Erratic of the Browne glaciation at mile 382 on the Alaska Railroad______________________________________ 22
7. Graphs showing the distribution of probable glacial erratics in the beds of parts of Lignite and Moody Creeks__ 23
8. Map showing distribution of probable glacial erratics of the Browne glaciation, and contours on the inferred
floor of the Browne glacial valley of the Nenana River_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 24
9. Cross sections of terraces on the east side of the Nenana River between Lignite Creek and Ferry_____________ 29
10. View southwest from mountain north of Garner, showing the two-story canyon of the Nenana River__________ 34
11. Geologic cross section of the floor of the buried Nenana River gorge at mile 354 on the Alaska Railroad, showing
buried lake deposits west of the river_______________________________________________________________ 35
12. Steeply dipping foreset beds of the delta built by Sheep Creek into glacial Lake Moody overlain by outwash
gravel of the Riley Creek glaciation_________________________________________________________________ 36
13. Geologic cross sections of delta deposits into glacial Lake Moody ________________________ ·-_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 36
14. Geologic cross section of the point of land between miles 349.5 and ::'50.3 on the Alaska Railroad, showing out-
wash gravel and alluvium resting on lake deposits of glacial Lake Moody________________________________ 37
15. Field sketch of geologic conditions on northeast bank of the Nenana River one mile north of McKinley Park
statioil__________________________________________________________________________________________ 38
16. Panorama of terraces on the west bank of the Nenana River between Pangengi Creek and Lignite____________ 39
17. Drainage changes on tributaries of the Nenana River from the beginning of the Dry Creek glaciation to the end
of the Healy glaciation_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 44
18. Field sketch of north bank of the railroad cut through the terminal moraine of the Riley Creek glaciation at
mile 34 7.2 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 45
19. North bank of the railroad cut in the terminal moraine of the Riley Creek glaciation________________________ 45
20. Field sketches of fresh exposures in railroad cuts through drumlinlike hills in ground moraine of the Riley
Creek glaciation__________________________________________________________________________________ 47
21. Sketch map and profile of terraces on the Nenana River in the vicinity of Healy ___ .________________________ 49
22. Field sketch of geologic relationships as seen in exposure in bluff on east bank of the Nenana River opposite the
mouth of Slate Creek_____________________________________________________________________________ 50
23. Terraces on the east bank of the Nenana River at Ferry_________________________________________________ 50
24. Projected profile of terraces on Healy Creek____________________________________________________________ 51
25. Truncated alluvial cones on the east side of the Nenana River____________________________________________ 5Z
26. East bank of the Nenana River, showing layers of blue-gray terrace gravel resting on truncated beds of Nenana
gravel and overlain by thick deposits of alluvium_____________________________________________________ 53
27. Outwash of the Carlo readvance resting on till of the Riley Creek glaciation on the east bank of the Nenana
River___________________________________________________________________________________________ 54
28. Alluvium and outwash of the Carlo readvance deformed and offset by post-Carlo faulting on the east bank of
the Nenana River opposite McKinley Park station____________________________________________________ 65
29. Recent fault scarp in alluvium and terrace gravel along the fault crossing the Alaska Railroad near Windy_____ 65
TABLES
Page
TABLE 1. Climatological data for three stations on the Alaska Railroad ___________________________________________ _ 7
2. Petrography of the intrusive rocks in the Cantwell formation ____________________________________________ _ 15
3. Petrography of intrusive rocks in the Birch Creek schist_ _______________________________________________ _ 16
4. Thickness of ice of the Healy and Riley Creek glaciations along rivers of the Alaska Range _________________ _ 27
5. Differences in preEent altitude of Nenana River p~ofiles of Browne and Dry Creek glaciations _______________ _ 32