�

�

���

��

��

�

�

�

�

�

�

����

�

��

�

��� �

�

��

�

��

�� � � �

�

81

86

83

78

82

7079

7580

72

7

7

5

7

5

7

10

45

8

5

30

82

74

80

87

85

81

75

77

80

87

70

5

78

81

65

6

Qya

Qw

Qya

Qya

Qya

Qya

Qoa

Qya

Qoa

Qoa

To

To

Tmv

Tsd

Qya

To

QoaQoa

Qvoa

Tsd

Tsd

Tsd

Tsd

Tmv

Tmv

Tmv

Qvoa

Tsd

Tmv

Qls?

Qls?

Qya

Qya

Qoa

Qls

Tsd

Qvoa

To

Qya

Tmv

Qls?

Kgt

Kgt

Kgt

Kgt

Kgt Kgt

Kgt

Kgt

Kgt

Kggd

Kggd

Kggd

Kggb

Kggb

Kggb

Kggb

KJmv

KJmv

KJmv

KJmv

Tof

Tof

Tof

TofTof

Tof

Tof

Tof

Tmv

TmvQya Tp

KJmv

Kggd

To

Qoa

Qoa

To

Tof

Qoa

KJmv

KJmv

Kggd

Kgt

Kgt

KJmv

KJmv

KJmv

Qoa

Qya

Qw

KJmv

Tof

TofQoa

Qoa

Qya

To

To

To

Qls

Qls?

Qls?

Qls?

Qls?

Qls?

Qls?Qls?

Qya

Qya

Tsd

Qls?

Qls?

Qls?

Qls?

KJmv

QlsQls

Qls?

Qoa

Qoa QyaTmv

Qoa

Qvoa

Qoa

Tmv

Qya

Qya

Qya

Qw

Qya

KJmv

DEPARTMENT OF

CONSERVATION

California

Geological Survey

GN

240 MILS13

0 021 MIL

MN

UTM GRID AND 1988 MAGNETIC NORTHDECLINATION AT CENTER OF SHEET

1/2

0

0

0

1

1

1.5

.5 2

2

2Thousand Feet

Kilometers

Miles

Scale 1:24,000

REFERENCES

Kennedy, M.P., and Peterson, G.L.,1975, Geology of the San Diego metropolitan area,

California; Section B, eastern San Diego metropolitan area: California Division of

Mines and Geology Bulletin 200, p. 43-56, scale 1:24,000.

Kennedy, M.P., and Tan, S.S., 1977, Geology of National City, Imperial Beach, and Otay

Mesa Quadrangles, southern San Diego metropolitan area, California: California

Division of Mines and Geology, Map Sheet 29, scale 1:24,000.

Kuper, H.T., and Gastil, R.G., 1977, Reconaissance of marine sedimentary rocks of south-

western San Diego County, California, and northwestern Baja California: San Diego

Association of Geologists, p. 9-15. Plate 2, scale 1:24,000.

Tan, S.S., 1992, Landslide hazards in the Jamul Mountains quadrangle, San Diego County,

California: California Division of Mines and Geology Open-File Report 92-12,

Geologic Map - Plate 29B, scale 1:24,000.

Mexico

Alpine

El Cajon

Jamul

United States

Ramona

67

94

1

2

4

Mexico

Alpine

El Cajon

Jamul

United States

Ramona

67

94

1

2

4

Santee

San

Ysidro

Chula

Vista

National

City

La MesaSan

Diego

Escondido

PowayDel Mar

Oceanside

15

S4

805

5

785

78

8

0 5 10

Miles

P A

C I F

I CO

C E

A N

INDEX MAP

1. San Vincente Reservoir quadrangle

2. El Cajon quadrangle

3. Jamul Mountains quadrangle

4. Otay Mesa quadrangle

Santee

San

Ysidro

Chula

Vista

National

City

La MesaSan

Diego

Escondido

PowayDel Mar

Oceanside

15

S4

805

5

785

78

8

0 5 10

Miles

P A

C I F

I CO

C E

A N

INDEX MAP

1. San Vincente Reservoir quadrangle

2. El Cajon quadrangle

3. Jamul Mountains quadrangle

4. Otay Mesa quadrangle

THIS

MAP

33

Quartz

Syenite

Quartz

Monzonite

Quartz

Monzodiorite

Syenite Monzonite Monzodiorite

Granite

Alk

ali-

feld

spar G

ranite

Tonalite

Diorite

Sye

nogra

nite

Gra

nodio

rite

Monzo

gra

nite

Quartz

Dio

rite

90 65 35 10

5

20

60Q Q

A P

60

20

5

60

Classification of plutonic rock types (from IUGA, 1973, and *Streckeisen, 1973).

A, alkali feldspar; P, plagioclase feldspar; Q, quartz.

*Streckeisen, A.L., 1973, Plutonic rocks--Classification and nomenclature recommended by

the IUGA Subcommission on Systematics of Igneous Rocks: Geotimes, vol.18, pp.26-30.

MAP SYMBOLS

Contact between map units.

Air photo lineaments that define major joints. No significant evidence of

faulting has been observed along these features.

Strike and dip of inclined sedimentary beds.

Strike and dip of inclined foliation in metavolcanic rocks.

Strike and dip of inclined foliation in igneous rocks.

Landslide (Qls) - arrow(s) indicate principal direction of movement, outline

includes headscarp of landslide. Querried where questionable.

5

?

50

25

Qw

Qya

Qoa

Qls

Tp

Tmv

Kgt

Kggd

Kggb

KJmv

Qvoa

Tsd

To

Tof

Late Holocene active channel and wash deposits; unconsolidated sand, silt,

gravel and clay. Deposits along smaller drainage channels are included in Qya.

Holocene alluvial deposits unconsolidated to locally poorly consolidated silt, clay,

sand and gravel. Included modern active sedmients along small drainage

channels.

Landslide deposits (Holocene and Late Pleistocene). Landslide slump and rock

fall deposits. On map, the deposit is depicted by landslide arrows (see "MAP

SYMBOLS"). Querried where questionable.

Late Pleistocene alluvial deposits; moderately consolidated, poorly sorted flood

plain deposits consisting of gravelly sandy silt and clay.

Middle Pleistocene alluvial deposits; well consolidated, poorly sorted flood plain

deposits consisting of gravelly, sandy silt and clay.

San Diego Formation (Pliocene); poorly indurated, fine- to medium-grained

sandstone, typically yellowish to light brown.

Otay Formation (Oligocene to Miocene); poorly indurated massive light-colored

sandstone, siltstone and claystone, interbedded with bentonite lenses.

Otay Formation - fanglomerate facies (Oligocene to Miocene); poorly cemented

bouldery conglomerate and coarse-grained sandstone. Interfingered with

overlying To.

Pomerado Conglomerate (middle Eocene); poorly to moderately cemented

massive cobble conglomerate with sandstone interbeds.

Mission Valley Formation (middle Eocene); poorly to moderately indurated light-

colored marine medium-to fine-grained sandstone with cobble conglomerate

lenses. Interfingers with underlying Stadium Conglomerate.

Tonalite (Cretaceous); includes some granodiorite and quartz diorite; medium-

grained; generally dark colored and severely weathered.

Granodiorite (Cretaceous); includes some tonalite and monzogranite; medium-to

coarse-grained.

Gabbro (Cretaceous); includes some peridotite, norite, quartz gabbro; medium-

grained and dark colored.

Metavolcanic rocks (Jurassic and Cretaceous); mildly metamorphosed volcanic,

volcaniclastic and sedimentary rocks. Volcanic rocks range from basalt to rhyolite,

but are predominantly andesite and dacite.

DESCRIPTION OF MAP UNITS

CENOZOIC

MESOZOIC

CORRELATION OF MAP UNITS

Qoa

Qw

Pleistocene

Holocene

QUATERNARY

CRETACEOUS

JURASSIC

TERTIARY

Qya

Eocene

Qls

Kgt Kggd Kggb

Tp

Tmv

Qvoa

PlioceneTsd

To

Tof

Oligocene/

Miocene

KJmv

GEOLOGIC MAP OF THE

JAMUL MOUNTAINS 7.5' QUADRANGLE

SAN DIEGO COUNTY, CALIFORNIA:

A DIGITAL DATABASEGeologic Mapping by

Siang S. Tan

Digital Preparation bySybil Jorgensen and Jonathan Williams

2002

This map was funded in part by the USGS

National Cooperative Geologic Mapping Program,

STATEMAP Award no. 01HQAG0092.

32o 37' 30"

117o 00'

32o 45'

117o 00'

STATE OF CALIFORNIA - GRAY DAVIS, GOVERNOR

THE RESOURCES AGENCY - MARY NICHOLS, SECRETARY FOR RESOURCES

DEPARTMENT OF CONSERVATION - DARRYL YOUNG, DIRECTOR Prepared in cooperation with the U.S. Geological Survey

Topographic base by U.S. Geologic Survey

7.5' Jamul Mountains Quadrangle

Polyconic projection, contour interval 20 feet,

dotted lines 10 feet.

32o 37' 30"

116o 52' 30"

32o 45'116

o 52' 30"

CALIFORNIA GEOLOGICAL SURVEY

JAMES F. DAVIS, STATE GEOLOGIST