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0"N

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QalQal

Qal

Qal

Kt

Gulf of Cal

Kt

Kt

Qal

Kt

Kd

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QPg

QPg

Kg

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Mr

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ms

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ms

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ms

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Qal

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ms

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Qal

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QPg

ms

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Mrb

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Kt

ms

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Pzq

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mv

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Qal

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ms

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Qal

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Mc2

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QPg

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Kt

QPg

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ms

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Mr

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Kt

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Mc2

Qal

Mrb

Mc1

Pzq

Qal

QPg

Kt

Md1

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QPg

Kgd

Mc2

Kt

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Mc2

Mdt

Mc2

Kt

Md1

Md3

Mc2

Mdt

Mc2

Qal

Md2

Qal

Qal

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Mr2

Qal

ms

Mdt

Mr2

Mrcp

Qal

Mc2

Ma2

Mb3

Ma2

Mdt

Qal

Ma2

Mb3

Qal

Mdt

QPg

QPg

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Md1

Mrcp

Qal

Md2

Md2

Ma2

Mc2

Mc1

Qal

Mr2

Mdt

Ma2

Mba

Mc2

Md2

Mc2

Mc1

Ma3

Ma2

Mc1

Mc1

Md3

Mdf

Qal

Mc1

Md2

Kg

Md1

Qal

Ma2

Qal

Mtsi

Md2

Ma1

Mc2

Md3

Md1

Md3

Mdf

Md1

Mrcp

Md1

Md2

Mr2

Mb2

Mdf

Mba

Tce

Md1

Md2

Mr2

Md2

Md1

Ma1

Ma2

Md2

Mr2

Md1

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Mb1

Md3

Mb3

Mb3

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Mr1

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Mr2

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Mta

Qal

Kgd

Qal

Qal

Qal

Qal

Kg

Kt

Kt

Kt

Kt

Kt

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Mc1

Mc1

Mc1

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Qal

Qal

QalKt

Mdf

Mdf

ms

Mdf

Mdt

Kd

Mb1

Kg

Kg

Kg

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Mdf

Mb1Mdt

Mdf

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Kg

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QPg

QPg

Qal

Qrs

Qal

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Mdt

Mdt

Mc2

Mba

Md1

Qco

Mdf

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Mdt

Kt

ms

Kt

ms

ms

Kt

Kt

Mc

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Qco

Qco

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Ma4

Mc2Mru

Ma4

Mr

Mr

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Mtcp

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Mc2

Md1

Mc2

Mc2

Md3

Qrs

Mb2

Mr2

Mr2

Mc2

Mc3

Mc2

QPg

QPg

Mr

Md3

Mba

Md2

KtKt

KtKtKt

mcb

mcbmcb

mcb

ms

Kg

Kg

ms

msKt

Mtsi

Ma2

Ma1

Mtcc Mss

Kt

Kt

Mss

Ma1Ma1

Mtsi

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Ma3

Mtsi

Mb1

Qal

Qal

Qal

Qal

Qal

Mtcc

Mtcc

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Mss

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Mst

Mst

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Ma1

Mc3

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mcb

ms

ms

Mc2

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Mdt

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Mb1

Mb2

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Mtsf

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Mtd

Mtd

Mtd

Mc3

Mc3

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QPg

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ms

Mc3

Mc3

Qal

Qal

Qal Kt

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Kt

Kt

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Qal

Kt

Mss

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Mdt

Mss

Mr1

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Mtsi

Ma1

Ma1

Md2

Ma3

Mb1

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Ma1 Kt Ma1Kt

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Mss

Mss

mv

Mtcc

Mtcc

Ma1

Ma1

Mtsi

Ma1

Qal

Ma1

Mtu

Qco

Mss

Mtsi

Qco

Mss

Ma1Mr1

Md1Md1

Md2Mst

Mst

Mr2

Mr1Mtsi

Mtsi

Mtsi

Md1

Md1Ma2

Md2

Ma2

Ma2Mst

Mtu

Ma2

Ma1

Md1

Ma1

Qal

Mr2

Md1Mc2

Mb3

Md2

Qal

Qal

Qal

Qal

Qal

Mba

Mb3

Mb3

Mb3

Mb3

Mb3

Mta

Mtsi

Qal

Mba

Mcu

Mc3

Mc1

Mc1

Mdt

Mdt

Mc1

Mru

Mru

Mc2

mv

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32

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DS-21

Seri Fault

Bacha Fault

Bacha Fault

Pozo Coyote Fault

Coyote Fault

Pozo

Pozo Coyote Fault

Noriega Fault

San

Igna

cio F

ault

?

Amado-Libertad Fault

A

A’

B’

B

C

C’

Gulf of California

DS-22

DS-17

DS-23

DS-24

S2G-114A

SON10-356G

SON10-346G

SE-03-06

S2G-114

El Desemboque

Pozo Coyote

C e r r o C o l o r a d o

C e r r o L a s B u r r a s

C e r r o P e l ó n

L o m a s O n a - J e c o

S i e r r a T o r d i l l a

Si e r r a B

a c h a

C e r r o P r i e t a

Rio San

Igna

cio

SON003

SON003

Lithologic Map Units

Cretaceous batholithic rocks Kg - granite Kgd - granodiorite Kt - tonalite (69.4 ± 1.2 Ma [U-Pb]) Kd - quartz diorite Mesozoic(?) metamorphic rocks ms - metasedimentary mcb - metacarbonate mv - metavolcanic

Basalt of Arivaipa (6.4 ± 1.9 Ma [K-Ar])

Tuff of Desemboque (10.4 ± 0.2 Ma [K-Ar])

Andesite # 3 (basaltic andesite with no olivine;11.8 ± 0.1 Ma [Ar/Ar])

Tuff of San Felipe (12.50 ± 0.1 Ma [U-Pb])

Tuff of San Ignacio (12.56 ± 0.1 Ma [U-Pb])

Tuff of Cerro Colorado (14.5 ± 0.3 Ma [U-Pb])

Exotic clast conglomerate (Gastil et al., 1973)

Syn-tectonic volcaniclastic conglomerate #3

Andesite #4 (vesicular basaltic-andesite flows)

Paleozoic(?) Quartzite

Qrs

Qco

Qal

QPg

Mba

Mc3

Ma4

Mtd

Mb3

Mr2

Mb2

Mst

Md3

Mrcp

Mtcp

Mc2

Ma3

Md2

Md1

Mtsf

Mtsi

Mta

Mr1

Ma2

Mc1

Mss

Mtcc

Ma1

Mdt

Mdf

Mb1

Tce

Pzq

Undifferentiated volcanic rocks Mru - rhyolite Mtu - tuffs and pyroclastics Mcu - volcaniclastic conglomerate

Rhyolite flows (Mr) and breccias (Mrb)

Basalt #1 (px ≈ oliv > plag)

Porphyritic dacite flows (plag >> bio > qz)

Dacitic lithic tuffs, breccias, and minor flows

Andesite #1 (vesicular basaltic-trachyandesite)

Maroon epiclastic sandstones (grus)

Mono-lithologic dacite conglomerate

Andesite #2 (aphyric purple trachyandesite flows)

Rhyolite #1 (crystal-poor w/ diagnostic flow banding)

Tuff of Arivaipa (maroon quartz-feldspar-lithic tuff)

Dacite #1 (trachydacite flows with minor sanidine)

Dacite #2 (common flow foliation and sanidine)

Volcaniclastic conglomerate #2

Tuff of Cerro Prieta (welded, pink, san > bio > qz)

Rhyodacite of Cerro Prieta (pink, foliated lava flows)

Dacite #3 (grey porphyritic flows, plag > alk ≈ amph)

yellow pumiceous sandstones and lithic tuffs

Basalt #2 (plag > opx >> amph)

Rhyolite #2 (thick, gray-purple aphanitic lava flows)

Basalt #3 (aphanitic, hyaline basalt)

Plio-Quaternary gravels (post-tectonic)

Quaternary colluvium

Quaternary alluvium

Quaternary fluvial deposits (Rio San Ignacio)

Gro

up 1

Bas

emen

tG

roup

2 (p

re-r

ift)

Gro

up 3

a (e

arly

rift)

Gro

up 3

b(la

te ri

ft)G

roup

4 (p

ost-r

ift)

Mio

cene

Pale

ozoi

c-M

esoz

oic

Cen

ozoi

cPl

ioce

ne-

Qua

tern

ary

Olig

o.(?

)

approximate strike and dip of bedding

strike and dip of bedding

eutaxitic foliation

horizontal bedding

metamorphic foliation

vertical eutaxitic foliation

vertical metamorphic foliation

strike and dipof fault

strike of verticalfault

fault with striae (arrow indicates trend of striae)

¦

o

pe

¨ ¨

¢

S¢

¤

45

Structures

approximate strike anddip direction

p

9

51

77

60

42

Contactscontact (dashed where approximate, dotted where concealed)

fault (dashed where approximate, dotted where concealed)

felsic dike (dashed where inferred)DD D D

DD DD DD intermediate dike (dashed where inferred)

high angle (or inferred high angle) normal fault

low angle normal fault

PLATE 1. GEOLOGIC MAP OF THE SIERRA BACHA, COASTAL SONORA, MEXICOMapping and data compilation by Michael H. Darin (2010-2011)

0 1 2 3 4 50.5Kilometers

0 1 2 30.5Miles

SCALE 1:30,000

CONTOUR INTERVAL 25 m

DS-21 Paleomagnetic drill site(site name shown)

Symbols

Geochronologic sample site(sample name shown)

S2G-114

Unimproved dirt road

Improved dirt road

Paved highway

AA’ Cross section line (Fig. 11, in text)

settlement

10.4º

True

Nor

th

Mag

netic

Nor

th

Datum: WGS 84Projection: UTM Zone 12N

Cartographic contours were created in ArcGIS v. 9.3using a 30m ASTER Global Digital Elevation Model thatwas smoothed and resampled to 10m resolution using

the RST interpolation method.

UNIVERSITY OF OREGONDEPARTMENT OF

GEOLOGICALSCIENCES

dike

jointÂ

j

25

73

(AT MAP CENTER, 2011)

108° W

108° W

112° W

112° W

116° W

116° W

30°

N

30°

N

26°

N

26°

N

22°

N

22°

N

STUDY AREA

U.S.Mexico

NORTHAMERICAN

PLATE

PACIFICPLATE

LOCATION MAP