Qg

Tbbu

Qg

Qv

Qg

Tbbu

Trh

Qg

QTb

Qhc

Tazm

Tazm

Qg

Tbbu

QTat

Qae

Qbc

Qae? Qhoc

Qls

Qca

Tbbu

Trh

Qls

Tazm

Trh

Trh

Qhtc

Tbbu

QTat

QTat

Trh

Trh

Trh Qha

Qha

Qha

Qha

Qha

QTat

Qal

Qt

Qdf

Qdf

Qaw

Qal

Qaw

Qoba

Qyba

Qoba

Qyba

QTb

QTb

Qob

Qacl

Qacl

QTb

Qyba

Tbao

Tbao

Tbao

Qls

Qo

Qo

Qal

Tma

QTba

Toa

Tma

Tma

Tbao

QTb

QTb

Qyba

Qoba

Qg

Qg

Qal

Tdb

Tdb

Tdl

QTb

QTb

QTb

Toma

Qal

Qca

Qaw

Qaw

Qg

QTb

Qv

QTbg

QTbg

Tbj

QTs

QTs QTab

Tbj

Tbj

Tbj

Tbj

Tcwf

Tcwf

Ttvp

Trgd

Trgx

Trgx

Trgx

Trgd

Trgd

Tcgn2

Qg

Tcwf

Tcgn2

QTab

Tbbu

Qg

Qls Qls

Tcwf

Tcgn2

QTb

Tcgn2

Tcwf

Trh

Tcwf

Bull Run Lake

Lost

 Lake

Laurence

Lake

Timothy Lake

Clear Lake

Rock Creek

Reservoir

Eliot Glacier

Newton

Clark

Glacier

Sandy

Glacier

Zigzag

Gl

Reid Gl.

Ladd Gl.

Coe Gl.

White River Gl

Palmer

Gl. 

Qca

Qget

Qg

Qt

Qha

Qhpc

Qha

Qha

Qgnt

Qget

Qhdl

Qhpc

Qhpl

Qgnt

Qgnt

Qget

Qal

Qget

Qget

QTat

Qget

QTb

Qaw

Qam

QTs

QTs

Tdgb

Tdgb

Ttv

Qal

Tvs

Tcwf

Tcgn2

Qls

Qls

Qls

Qls

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Tomr

Tcgn 

Tcgn2

Qls

Qls Qls

Qls

Qls

Qls

Tcgn2

Tcwf

Tcwf

Qca

Tcwf

Tcgr2

Tcgr2

Tcgr2

Tcgr2

Tcgn2

Tcgr2

Toma

Tomr QTs

QTs

QTb

Qal

QTs

Qal

Tdl

Qca

Qca

Qv

Qv

Qv

Qv

Qal

QTb QTb

Tbao

Qal

Qca

Qca

Qt

Qls

Qal

Qt

Qt

Tma

Toa

Toa

Toa

Toa

Tcwf

Tcgn2

Qt

Qt

Qt Qg

Qg

Qg

Tbao

Tbao

Qg

Qt

Qg

Qg

Qv

Qt

Qg

Tma

Qt Qls Qt

Tbao

Tbao

Qt

Tbao

Tma

Qg

Qg

Qg

Qt

Qg

Qg

Qt

Tbao

Qt

Tbao

Qg

Trh

Qg

Tcgn2

Tcwf

Tbbu

Qca

Tcwf

Qhoc

Qhpc

Trh

Qls

Qv

Tcgn2

Tcwf

Tcwf

Tcwf

Trh

Qal Qls

Qls

Qls

Qal

Qal

Qhtc

Qhoc

Tma

Tma

Qv

Qhpc

QTat

Qg

Qhpc

Qhpc

Qhpc

Qhpc

Qha

Qhpc

Tma

QTat

Qhtc

Qha

Qhoc

Qhtc Qhpl

Qhtc

Qhc Qhc

Tazm

Trh

Trh

Trh

Tbbu

Qha

Qha

Qhtc Qhoc

Qhol

Qhpl

Qhpl

Qhpl

Qha

Qha Qha

Qhpc

Y

Y

Y

0

0

0

Qhpc

Qg

Qal

Qt

Qal

Qca

Qhpc

Qhpc

Tcwf

Tcgn2 Qt

Qt

Qv

Qv

Qv

Qv

QTb

QTb

QTb

Tdm

Td

Td

QTb

Tcwf Tvs

Tcwf Tcgn2

Tcgn2

QTb Tcgn2

Tcgn2

Tcwf

Qhc

Qha

QTb

Qv

Qbr Qg Qca

Qt Qca

Qv

Qv

Qca

Qca

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Tazm

QTb

Qls

QTb

Trh

Trh

Tazm

Qls

Tvs

Tvs

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Tcgn2

Tcgn2

Tcgn2

Tcgn2

Tcgn2

Tcgn2

Tcgn2

Tcgn2

Tomr

Tcwf

Tcwf

Tcwf

Tbj

Tbj

Tdgb

QTb Tbj

Qg Qg

QTbg

Qt

Qal

Qg

Qob

Qaw Qv

Qv

Qal

QTs

QTs

Qyba

QTb

Qoba

Qg

Qg

Qg

Qv

Qv

Qal

Qca

Tbao

Qal

Qyba

Qas

Qas

Qas

Qas

Qas

Qas

Qas

Tar

Tar

Tar

Tar

Tar

Qv

Qv

Qls

Tma

Tma

QTbme

Qls

Qls

QTbme

QTbme

Trbg

Trbg

Trbg

Trbg

Trbg

Trbg

Trbg

Trbg

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Tr

QTb

Qiba

Qiba

Tiba

Tiba

Tiba

Tiba

Tiba

Qt

Qt

Qg

Qg Tiba

Tiba

Tiba

Tiba

Tiba

Tha

Tha

Ta

Ta

Qac

Qabl

Trbg

Qah

Qahr

Tvmf

Tvmf?

Tvmf?

Tvmf Tvmf

Qall

Qall

Qap

Qap

Qall

Qall

Qg Qt

Qv

Qv

Qbap

Qbr

Qbr Qt

Qal

Qget

Qal

Qt

Qca

Qal

Qoe

Qget

Qgnt

Qgnt Qgnt

Qhdl

Qha

Qbac

Qbac

Qbac?

Qbac

Qbdr

Qbdr

Qbdr

Qbdr

QTb

QTb

Tlma

Tlma

Tlma

Tlma

Tlma

Qha

Qha

Tlma?

Qhc?

Tlmd?

Tlmd Tlmd

Tlmb

Tlmb Qal

Qls

Tos

Tos

Tcgn2

Tbao

Tbao

Qt Qo

Tbao

Tbao

Tbam Tbam

Trh

Trh Tas

Tas

Tas Tas

Tas

Tfa

Tfa

Tfa

Tfa

Tiba

Trh

Trh

Tcwf

Tdp

Qt

Qt

Qt

Qt

Tfa

Tbao Qt

Trh

Qg

Qob

Qob

Tcgn

Tcgn2

Tcgn2

Qob

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Qls

Qt

Tbg

Qal Qaw

Ttla1

Ttla1

QTtla2

QTtla2

Qob

Qca

Qg

QTtlb

QTtlb

QTtlb

Qg

Qls

Tb

Tb

Tb

Tb

Tb

Qhtc

QTa

QTa

QTa

QTa

QTb

QTa

Qsg

Qsg

Qal Qls

Qls Qls

Qha Qhc

Qha

Qhoc

Tazm

Qhc

Qhtc

Qhpc

Qhc

Tazm Qget

Qhpc

Qhpc

Qget

QTb

Qal

Qls

QTb

QTba

QTb

Qg

Qt

Qget

Qls

Tb Tbbu

Tazm

Qal

Qbdc

Qbdc

Ts

Ts Ts

Tbbu

Qls

Tia

Tia

Qt

Taef

Taef

Taef

Taef Taef

Taef

Taef Qt

Td

Taef

Taef

Taef

Qbp

Qha

Qha

Qha

Qha Qha

Qha

Qha

Qha

Qal

Taop

Taop

Taop

Taop

Taop

Taop

Tb Taop

Qls

QTba

Qal

Taop? Taop?

Taop?

Tafv

Taft

Taft

Taj

Qg

Tcwf

Taj

Taj

Taj

QTb

Qv

Taft

Trgd

Qg

Td

Trgd

Tcgn2

Tcgn2 Qls

Tcwf Trgd

Tcwf

QTb

Qv

Tbas

Tbas

Qbal

Qbas

Qbap

Talb

Talb

Tb

Tb

Tb

Talb

Talb Ttvp

Ttvp

Ttvp

Ttvp

Ttvp

Ttvp

Ttvp

Qt

Qt

Tcgn Tcgn2 2

Ttvp

Tcgn2

Trgx

Trgx

Ttvp

Tcwf

Tcwf

Tcwf

Trgx Tcwf

Tbah

Tbah

Tbah Ttvp

Ttv

Qls

Qls

Tbah

Tbj

Tbj

Qls

Qls

Tcgn2

Tcwf

Tvs

Tvs

Tys

Tys

Tys

Tatc

Qls

QTs

Tilh

Tilh

Laurel Hill

intrusion

Still Creek intrusion

UNMAPPED

UNMAPPED

UNMAPPED

Tcwpr

Tcwf Tcgn2 Tcwf Ts

Tb

Qal

QTb

QTs

QTs

Taft

Qal

Tcwf Tcwpr

Td

Td

Td

Tcgn2

Tcgn2

Tcgn2

Tcwf

Tcwf

Tvs

Tcgn2

Tcgr2

Tcgr2

Tcgn2

Tcgr2

Tcwf

Tcwf

Tcwf

Tcgr 

Tcgr2

Tcwf Tcwf

Tcwf

Tcgn2

Tcwf

Tcwf

Tcgn2

Tar

Tr

Qoba

Tbao

Qt

Tbao

QTs

QTs

Tcwf

Tcwf

Tcwf

Tcwf

Tcwf

Tb

Qha

Qbaa Qha

Tbbu

Tcwpr

Qt

Taop

Qca Qget

Qgnt

Qgnt

Qhpl

Qget

Qhpc

Qget

QTb

Qls

Qha

Qal

Qls

Qal

Qal

Qal

Qal

Qal

Qca

Qt

Tbao

Qv

Qv

Qg

Qt

Qt

Tbao

Qv

Qv

Tma

Qca

QTb

Tba

Tomt

Tomt

Tomt

Tcgn2

Tcgn2

Tcgn2

Qal

Tcwf

Tcwf

Tcwf

Qls

Tcgn2

Tb

Ttvp

Tcgn2

Tcgn2

Td

QTb

Trgx

QTs

QTb

QTb

QTb Taft

Qv

QTb

Qls

Qt

Qca

Qca

Qt

Td

Qt

Tb

Tb

Td

Qt

Qv

Qt

Qhpc Qhpc

Qhpc

Qal

Qhpc

Qhpc

Qget Qhpc

Tilh

Qal

?

?

59

56

41

42

43

39

29

13

22

24 14

33

37

23

11

25

30

35a 34

31 32

38

36

27

15

10

8

21

1

3

9

18

7

5

2

40

20

6

28

26

12 16

49

51 53

44

52

45 48

50

55

54

47

19

17

2

1

3

3

7

7 7

1

1

3

42 43

2

4

6

70

87

80

26

23

26

67 67

66

3

28

11

22 22

41

82

4

20

5

45

40

2

87

72

60 68

238

75

240

255

71

67

358

343

16

350

339

230 15

20

284

185

347 337

22

0

98

54

0

0

56

57

239

240

238

240

60 68

75

289

255

67

71 82

90 95

35

72

55

102

110

164

218

13

Glisan

N

N

R

R

R

N

R

R

R

R

R R

R

N

N N

N

N

N

R

N

R

R

R

R

R

N

N

R

N

N

R

N

N

N

R

R

N

N

R

N

R

N

N

R R

R

R

R

R

R

R

R

R

R N

N

N R R

R

R N

R

N

R

R

R

R

R

N R

N

N

N

N

N

N

R

N

R

N

R

R

R

R

R

R

N

R

N

N

Pucci

OMF-1

OMF-7A

image area (without reg marks) center of image area

center of image area

image area (including reg marks)

trim size

Preliminary Geologic Map of the Mount Hood 30- by 60-Minute Quadrangle, 

Cascade Range, North-Central Oregon

By

David R. Sherrod and William E. Scott

1995

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

This map is published as an online-only version. If printed, then dimensional calibration may vary 

between electronic plotters and between X and Y directions on the same plotter, and paper may 

change size due to atmospheric conditions; therefore, scale and proportions may not be true on 

plots of this map.

Digital files available at http://pubs.usgs.gov/ds/906

Suggested Citation: Ma, Lina, Sherrod, D.R., and Scott, W.E., 2014, Digital data for preliminary 

geologic map of the Mount Hood 30- by 60-minute quadrangle, northern Cascade Range, Oregon: 

U.S. Geological Survey Data Series 906, pamphlet 36 p., scale 1:100,000 

[http://dx.doi.org/10.3133/ds906].

Printed on recycled paper

12'30" 10' 121°00'

121°30' 122°00'

122°00'

45°00'

15'

45°30'

45°00'

122°00'

45°30'

121°30'

15'

Y

O

26

80

R

59

OMF-1

Palmer

Gl. 

Qaw

Qas

Qap

Qabl

Qac

Qacl

Qae

Qah

Qahr

Qal

Qall

Qam

Qca

Qbr

Qbp

Qbaa

Qbac

Qbal

Qbap

Qbas

Qbc

Qbdc

Qbdr

Qhpl

Qhtc

Qiba

Qls

Qo

Qob

Qoba

Qoe

Qsg

Qt

QTa

QTab

QTat

QTb

QTba

QTbg

QTbme

QTs

QTtla2

QTtlb

Qv

Qyba

Ta

Taef

Qhpc

Qhol

Qdf

Qg

Qgnt

Qget

Qha

Qhc

Qhdl

Qhop

Tbah

Tba

Tb

Taft

Tafv

Taj

Talb

Taop

Tar

Tas

Tatc

Tazm

Tcgr2

Tcgn2

Tcwf

Tbam

Tbao

Tbas

Tbbu

Tbg

Tbj

Tcwpr

Tlmb

Tlmd

Tma

Toa

Toma

Tomr

Tomt

Tos

Tr

Trbg

Trgd

Trgx

Trh

Ts

Ttla1

Ttv

Ttvp

Tv

Tvmf

Tvs

Tys

UNMAPPED

Tlma

Tilh

Td

Tdb

Tdgb

Tdl

Tdp

Tdm

Tfa

Tha

Tiba

Tia

LIST OF MAP UNITS

[Arranged alphabetically by map-unit symbol except within stratigraphic 

groupings, where shown by age. See Description of Map Units (in pamphlet) for 

unit descriptions, where volcanic units are arranged into sections according to 

quadrants on the map. Bracketed letters following unit names in this list 

indicate corresponding section in Description of Map Units]

Andesite of Boulder Lake [SE]

Andesite of Cabin Creek [SW]

Andesite west of Clear Lake [SW]

Andesite of Enola Hill [NW]

Andesite of Hiyu Mountain [NW]

Andesite of Horseshoe Ridge [NW]

Alluvium

Andesite of Laurance Lake [NW]

Andesite of McCubbins Gulch [SE]

Andesite of Perry Lake [NW]

Andesite of Skyline Road [SW]

Andesite of Wapinitia Pass [SW]

Basaltic andesite of Aschoff Buttes [NW]

Basaltic andesite of Cloud Cap [NW]

 Basaltic andesite of Lost Lake Butte [NW]

Basaltic andesite of The Pinnacle [NW]

Basaltic andesite of Stump Creek [NW]

Basalt of Crutcher Bench [NW]

Basaltic andesite of Devil Canyon [NW]

Basaltic andesite of Dog River [NE]

Basaltic andesite of Parkdale [NW]

Basaltic andesite of Blue Ridge [NW]

Colluvial and alluvial slope deposits

Dacite of Frog Lake Buttes [SW]

Glacial deposits

Glacial deposits, till of neoglacial age

Glacial deposits, till of Evans Creek age

Pre-Polallie andesitic and dacitic rocks of Mount Hood

Andesite and dacite lava [NW]

Pyroclastic-flow and debris-flow deposits [NW]

Debris-avalanche deposit of Ladd Creek [NW]

Products of Old Maid eruptive period

Pyroclastic-flow and debris-flow deposits [NW]

Lava flows [NW]

Products of Polallie eruptive period

Pyroclastic-flow and debris-flow deposits [NW]

Lava [NW]

Timberline eruptive period, pyroclastic-flow and debris-flow 

deposits [NW]

Intrusive basalt and basaltic andesite

Landslide deposits

Outwash

Olivine basalt [SW]

Older basaltic andesite [SW]

Outwash of Evans Creek age

Rocks of Sandy Glacier volcano [NW]

Talus

Andesite [NE]

Andesite of Badger Butte [NE]

Andesite of Tom Dick and Harry Mountain [NW]

Basalt [SE]

Basaltic andesite [SW]

Basaltic andesite of Grasshopper Point [SE]

Basaltic andesite of Mirror Lake and Eureka Peak [NW]

Sedimentary rocks and deposits [SE]

Volcanic rocks in Trillium Lake area

Andesite [SW]

Basalt [SW]

Cinder cone or small volcano

Younger basaltic andesite [SW]

Andesite [SW]

Andesite of East Fork Hood River [NE]

Andesite of Fifteenmile Creek [NE]

Andesite of Fivemile Butte [NE]

Andesite of Jordan Butte [NE]

Andesite of Little Badger Creek [NE]

Andesite of Lolo Pass [NW]

Andesite of Rocky Point [SW]

Andesite of Salmon Butte [SW]

Andesite of Tumble Creek [NW]

Andesite of Zigzag Mountain [NW]

Basalt [NW]

Basaltic andesite [SW]

Basaltic andesite of Happy Ridge [NE]

Basaltic andesite of Mack Hall Creek [SW]

Basaltic andesite of the Oak Grove Fork [SW]

Basaltic andesite of Sunset Spring [NE]

Basalt of Bull Run Watershed and other ridge-capping basalt [NW]

Basalt near Ghost Creek [SW]

Basalt of Juniper Flat [SE]

Columbia River Basalt Group

Wanapum Basalt, Priest Rapids Member [NW]

Wanapum Basalt, Frenchman Springs Member [NW]

Grande Ronde Basalt, normal-polarity unit 2 [NW]

Grande Ronde Basalt, reversed-polarity unit 2 [NW]

Dalles Formation [NE]

Dacite of Beaver Butte [SW]

Dacite of Graveyard Butte [SE]

Dacite north of Long Ridge [SW]

Dacite of Mill Creek Buttes [NE]

Dacite of Plaza Lake [SW]

Fine-grained andesite [SW]

Hornblende-bearing andesite [SW]

Intrusive andesite

Intrusive basalt or basaltic andesite

Intrusive rocks of Laurel Hill [NW]

Lookout Mountain volcanic sequence

Andesite [NW]

Basalt [NW]

Dacite [NW]

Andesite of middle and late Miocene age [SW]

Older andesite [SW]

Volcanic rocks of the Mutton Mountains

Andesite [SE]

Rhyolite [SE]

Tuff and tuffaceous sedimentary rocks [SE]

Older sedimentary rocks

Rhyolite [SW]

Rocks of Barlow Ridge and Gunsight Butte [NW]

Rhyodacite of Gordon Butte

Domes and flows [NE]

Tuff breccia [NE]

Rhododendron Formation [NW]

Sedimentary rocks [NW]

Volcanic rocks in Trillium Lake area, andesite [SW]

Tygh Valley Formation [NE]

Pyroclastic and sedimentary rocks [NE]

Cinder cone or small volcano

Volcaniclastic rocks of Middle Fork of Hood River [NW]

 Volcaniclastic rocks [NE]

Younger sedimentary rocks [SW]

Unmapped [NW]

Contact—Approximately located. Short dashed where inferred; shown 

dotted where enclosing a zone of propylitic alteration between 

Salmon River and Still Creek as mapped by Wise (1969)

Contact—Separating sequentially younger deposits of Polallie eruptive 

period in and adjacent to Newton Creek east of Mount Hood (unit 

Qhpc). Contact labeled to show relative age of deposits: Y, 

younger; O, older

Contact—Bounding unmapped area in Salmon River drainage and 

poorly mapped area in Mutton Mountains

Fault—Showing dip locally; dashed where approsimately located or 

inferred, dotted where concealed. Ball and bar on downthrown 

side

Reverse or thrust fault—Dashed where approximately located or 

inferred, dotted where concealed. Teeth on upper plate

Anticline—Showing crestline and locally showing plunge

Syncline—Showing troughline

Monocline—Shown only on Columbia Plateau and on east wall of 

Hood River escarpment

Abrupt decrease of dip in direction of arrows

Abrupt increase of dip in direction of arrows

Lineament—Interpreted from aerial photographs

Moraine crest—Shown in glacial deposits (unit Qg)

Strike and dip of clastic strata or layering in basalt flows

Inclined

Horizontal

Overturned—Found in lava flows of Columbia River Basalt Group 

on Tygh Ridge

Dike—Tick marks indicate composition; two ticks, basalt or basaltic 

andesite; three ticks, andesite or dacite

Intermediate-size volcano—Showing central buildup of basalt or 

basaltic andesite shield volcanoes. Many occurrences interpreted 

on basis of landform, owing to lack of dissection

Thermal remanent magnetization (TRM) measurement—N, normal 

polarity; R, reversed polarity

Potassium-argon sample locality—Showing map number (table 1) 

Samples from bedrock exposures except No. 31, which is from 

drill core. Nos. 46, 57, and 58 are from outside map area and not 

plotted on map. Thermal remanent magnetization indicated by R

(reversed polarity) or N (normal polarity) where known

Drill hole locality—Showing name and number for holes deeper than 1 

km. Two holes west of Mount Hood in upper reach of Old Maid 

Flat (OMF-1 and OMF-7A) and one hole (Pucci) on south flank of 

Mount Hood. Locations from Priest and others (1982) and Hook 

(1982). Symbol for OMF-7A nearly filled by dot showing K-Ar 

sample locality No. 31

Snow and ice—Showing extent of major glaciers. Limited to higher 

elevations of Mount Hood. Names of separate glaciers shown 

where space allows

CONTOUR INTERVAL 50 METERS

1 0 1 2 3 4 5 6 7 8 9 10 KILOMETERS

SCALE 1:100,000

1 0 1 2 3 4 5 6 7 8 MILES

APPROXIMATE MEAN

DECLINATION, 2013

151

/2° 

TRUE NORTH

MAGNETIC NORTH

OREGON

MAP LOCATION

Base from U.S. Geological Survey, 1983

Universal Transverse Mercator projection, zone 10, North American 

datum of 1927

Base, intended for visual reference only, was fitted to map neatline by 

inspection. River-reach GIS layer (Oregon Geospatial Enterprise 

Office website, http://www.oregon.gov/DAS/CIO/GEO/), digitized from 

1:24,000- and 1:62,500-scale maps, is also fitted by inspection and 

varies slightly in its coincidence with base map

Geology mapped by D.R. Sherrod, 1985 and 1987–94; and 

W.E. Scott, 1989–94. Distribution of Columbia River Basalt 

Group compiled from published and unpublished sources of 

mapping

This map sheet presents legacy mapping that was available 

previously only in paper print-on-demand format, published 

1995. GIS database by Lina Ma, 2006; digital cartography by 

D.R. Sherrod, 2013

Manuscript approved for publication December 15 , 2014

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 95-219

Pamphlet accompanies map

Prepared in cooperation with the

National Park Service and Bureau of Land Management

0.40” space

0.30” space

1.0”

space

registration

marks

0.275” space

0.05” space

minimum 0.50” space

text box for cooperator note always is centered

within entire image area (but text box should

not overlap any other map elements – allow

at least 0.5” space on either side)

guides

DBID

DBID

Prepared In Cooperation Note

Recycled Paper Note Author Affiliation Footnote URL Character Style

Pamphlet Accompanies Headnote

Map Series Headnote

Sheet X of Y Headnote

Footnote # in Author Affiliation Footnote Character Style

Cooperator Note

Lat/Long Value

Along Left Side

Lat/Long Value

Along Top & Bottom

SURFICIAL DEPOSITS,

ALL PARTS OF MAP AREA

Qbp

Qbaa Qbap Qbac

QTb

Qall Qsg

QTbme

Qah

QTat

Tbbu

Trbg

Tvmf

Tilh

Tazm

Trh

Tcwpr

Tcwf

Tcgn2

Tcgr2

Qbas

Tlma

Tlmb

Tlmd

Taef

Tatc

Qhol

Qhoc

Qhdl

Qhtc

Qhpl

Qhc Qha

Qhpc

Qbc

Qbdc

Qahr

NORTHWESTERN PART OF MAP AREA

Tb

Taop

Qbal

Ts

Qae

Qbr

Qap

?

?

Qac Qyba

Qas

Qaw

QTb

QTtla2

Tma

Tr

Tfa

Tbam

Toa

Tcwf

Tcgn2

Qob Qdf Qacl Qoba

Tos

Trh

Tbg

Ttla1

QTtlb

Tbao

Tha

Tys

Tar Tdl

Tdb

Tba

Tas

Ta

Tdp

QTba QTba

?

CORRELATION OF MAP UNITS

SOUTHWESTERN PART OF MAP AREA

QTb

QTs

Taft

Tb

Td

Taef

Tvs

Tcwpr

Tcwf

Tcgn2

Tcgr2

Qbdr

Trgd

Trgx

Tbah Talb

Ttv

Ttvp Taj

Tbas Tdm

Tafv

NORTHEASTERN PART

OF MAP AREA

QTab

QTa

QTs

QTbg

Qabl

Tdgb

Tcwf

Tcgn2

Tcgr2

Tbj

Tomt

Toma Tomr

QTb

SOUTHEASTERN PART

OF MAP AREA

Qam

VENT DEPOSITS AND INTRUSIVE ROCKS

ALL PARTS OF MAP AREA

Qg

Qt Qls Qgnt Qal Qca

Qget

Qo

Qoe

Qv

Qiba

Tv Tiba

Tia

2

5

24

0.78

Pliocene

Miocene

Oligocene

TERTIARY

1.76

1.98

2.60

3.05

0.78

**

** Normal polarity (black) and reversed 

polarity (white) shown for major 

subchrons through end of Gauss 

time

**

APPROXIMATE AGE, IN

MILLIONS OF YEARS AGO

(Nonlinear scale)

Matuyama ReversedPolarity Chron

Pre-Gauss chrons

Gauss Normal -

Polarity Chron

Brunhes NormalPolarity Chron

0.010

Holocene

Pleistocene

QUATERNARY