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360000
360000
370000
370000
380000
380000
3270
000
3270
000
3280
000
3280
000
112°15'0"W
112°15'0"W
112°20'0"W
112°20'0"W
112°25'0"W
112°25'0"W
112°30'0"W
112°30'0"W29
°40'
0"N
29°4
0'0"
N
29°3
5'0"
N
29°3
5'0"
N
29°3
0'0"
N
29°3
0'0"
N
QalQal
Qal
Qal
Kt
Gulf of Cal
Kt
Kt
Qal
Kt
Kd
Qrs
QPg
QPg
Kg
QPg
Mr
Kt
ms
Kt
QPg
ms
Kt
Kt
QrsQPg Qal
Kt
Mba
Mc3
Kt
Qrs
ms
Qal
Kt
Qal
Qal
Kt
QPg
Qrs
Qal
Mc1
Mdt
QPg
Kt
Mc1
Qal
Qal
Kt
Kt
Qal
Mba
Qal
Qal
Kt
Kt
QPg
Mrcp
Mtsi
Kt
ms
QPgQal
Qal
Mc2
QPg
ms
Qal
Mrb
Kt
Kt
ms
Kgd
Pzq
Mb3
Kt
Qal
Mc2
Qal
Kt
mv
Mb3
Kt
Kt
Kt
Qal
Mdt
Mc3
Kgd
Kt
Qal
Qal
Kt
Mba
Mdt
Qal
ms
Mb3
Qal
Kt
Mc1
Mc2
Mb3
QPg
Qal
QPg
Mc2
Kt
QPg
Mc1
Mdt
ms
QPg
Mr
Qal
Kt
Mtsi
Mc2
Qal
Mrb
Mc1
Pzq
Qal
QPg
Kt
Md1
Qal
Mc1
QPg
Kgd
Mc2
Kt
QPg
Mc2
Mdt
Mc2
Kt
Md1
Md3
Mc2
Mdt
Mc2
Qal
Md2
Qal
Qal
QPg
Mr2
Qal
ms
Mdt
Mr2
Mrcp
Qal
Mc2
Ma2
Mb3
Ma2
Mdt
Qal
Ma2
Mb3
Qal
Mdt
QPg
QPg
Qal
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
Md1Ma2
Mb1
Md3
Mb3
Mb3
Ma2
Mr1
Md3Mc1
Mr2
Mdt
Ma3
Ma3Md2
Ma1
Mr
Mb3
Mc3
Md2
Mb1
Ma2
Mb2
Md1Ma2
Ma2
Mb1
Mb3
Ma1
Ma1
Mba
Md1
Mc3
Mta
Qal
Kgd
Qal
Qal
Qal
Qal
Kg
Kt
Kt
Kt
Kt
Kt
Kg
Mc1
Mc1
Mc1
Mc1
Qal
Qal
Qal
QalKt
Mdf
Mdf
ms
Mdf
Mdt
Kd
Mb1
Kg
Kg
Kg
Mdf
Mdf
Mb1Mdt
Mdf
KtKt
Kg
Qal
QPg
QPg
Qal
Qrs
Qal
Mdt
Mdf Mc1
Mdt
Mdt
Mc2
Mba
Md1
Qco
Mdf
MdtMdt
Mdt
Kt
ms
Kt
ms
ms
Kt
Kt
Mc
Qco
Qco
Qco
Mb3Mru
Ma4
Mc2Mru
Ma4
Mr
Mr
Mtcp
Mtcp
Mr
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
Md2 Qco
Ma3
Mtsi
Mb1
Qal
Qal
Qal
Qal
Qal
Mtcc
Mtcc
Ma1
Mss
Qal
Mtsi
Mst
Mst
Ma1
Ma1
Mc3
KgMtd
Mtsf
Mb1 Mdt
Mc3
mcb
ms
ms
Mc2
Kt
Ma2
Mdt
Mdt
Mb1
Mb1
Mb2
Mtsf
Mtsf
Kgd
Mtd
Mtd
Mtd
Mtd
Mc3
Mc3
QPg
QPg
Mc2
Mb2Kt
ms
Mc3
Mc3
Qal
Qal
Qal Kt
KtMa2
Mtsi
Mdt
Kgd
Kt
Kt
Qal
Qal
Kt
Mss
Ma1
Mdt
Mss
Mr1
Mtsi
Mtsi
Ma1
Ma1
Md2
Ma3
Mb1
MtsiMb2
Mtcc Ma1
Ma1 Kt Ma1Kt
MtccMa1
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
Mtsi
Ma1
Mtcc
Mtcc
53
32
32
76
41
69
72
71
66
33
62
46
45
56
33
70
3550
54
36
5456
83
60
84
8680
79
71 70
38
4381
82
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
