U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

PRELIMINARY GEOLOGIC MAP OF THE 

PAROWAN QUADRANGLE, IRON COUNTY, UTAH

By

1 2 Florian Maldonado and Rosalie C. Moore

Open-File Report 93-3

.S. Geological Survey, Denver, CO 

Kent State University, Department of Geology, 

Kent, Ohio, 44242

This report is preliminary and has not been reviewed for conformity with U.S. Geological

Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for

descriptive purposes only and does not imply endorsement by the USGS.
DESCRIPTION OF MAP UNITS

[PHENOCRYST CONTENTS ARE AVERAGES FROM VARIOUS CITED REFERENCES; 

AGES CORRECTED FOR NEW DECAY CONSTANTS (STEIGER AND JAGER, 1977); 

ROCK CHART COLORS FROM GODDARD (1948)]

Qac Alluvium and colluvium undivided (Holocene)-Pebbles, cobbles, and boulders in 

a silt and sand matrix. Poorly sorted. Composed of locally derived material 

deposited along streams, bordering flood plains, and local depressions. 

Estimated maximum thickness 5 m

Of a Fan alluvium (Holocene) In Parowan Valley deposits are composed of poorly 

sorted pebbles, cobbles, and lesser amounts of boulders supported by silty 

sand matrix. Unit includes well rounded clasts derived from conglomerate 

beds of the Grand Castle (Tgc), Claron (Tc), and Brian Head (Tbh) 

formations. Approximate thickness 20 m

QTfa Basin-fill deposit (late Pleistocene-Tertiary) Shown in cross section only. 

Includes basin-fill alluvial deposits approximately 470 m thick

Qt Terrace alluvium (late Pleistocene)-Medium to coarse sand and pebbly to

bouldery gravel. Found in the upper part of First Left Hand Canyon. Clasts 

are predominantly from Baldhills Member of Isom Formation (Tib) and also 

may have been eroded from landslide debris (QTli) hi Yankee Meadows. 

Estimated maximum thickness 20 m

Qbw Trachy-basalt lava flows of Water Canyon (middle Pleistocene)-Black to darkgray, dense to vesicular, olivine-clinopyroxene bearing flows. Quartz 

xenocrysts common. Vent is located hi Water Canyon approximately 3 km 

east from eastern edge of Parowan Valley where flows fill a paleovalley. KAr whole rock date of lava is 0.45 ±0.04 Ma (Fleck and others, 1975). Table 

1 shows chemical analysis and CIPW normative analysis. Thickness about 

120m

Qbwc Cinder cone of vent area-Composed of grayish-red scoria approximately 90 m 

thick

Qbwd Feeder dike for basalt lava flows-Dark gray dense olivine-clinopyroxene 

bearing. Width about 2 m

Qbh Breccia and basaltic dike of Second Hand Canyon (Pleistocene?)-Breccia and 

dikes are located hi Second Left Hand Canyon west of Henderson Hill. 

Breccia contains predominantly angular fragments of Claron Formation, 

Grand Castle Formation (?), cinder blocks of mafic rock, and sparse Needles 

Range Group rocks and Isom Formation hi a gray matrix. The breccia and 

dike may represent a vent complex. Approximate thickness 60 m

Qdh Basaltic dikes Dikes are medium gray and fine grained, and contain olivine

and clinopyroxene phenocrysts, rare quartz xenocrysts(?) and rare sandstone 

xenoliths. Dikes intrude the breccia and parallel mapped faults. Exposure 

may represent remnants of a vent breccia with feeder dike (roots of a cinder 

cone)

Qp Pediment alluvium (middle? Pleistocene) Poorly sorted deposit composed of 

subangular pebbles, cobbles, and sparse boulders of Tertiary volcanic rocks, 

and Tertiary-Cretaceous sedimentary rocks hi a silty sand matrix. Deposited 

as thin veneers on fan-shaped surfaces. Estimated thickness 3-12 m
Landslide debris (Pleistocene)

Ql Debris undivided-Landslide debris deposited in grabens or against the

downthrown side of normal faults. May contain pebble- to boulder-size 

Tertiary volcanic and Tertiary-Cretaceous sedimentary rocks in a matrix of 

sand, silt and clay. Estimated maximum thickness 90 m

Qli Debris of Baldhills Tuff Member of Isom Formation-Deposit composed of

blocks of brecciated grayish-red ash-flow tuff. Deposited along plateau front 

near edge of Parowan Valley. Estimated thickness 15 m

QIC Debris of Claron Formation-Deposit of broken blocks of moderate-red, 

bluish-white, grayish-orange sandstone, siltstone and limestone. May be 

same as gravity-slide block of Claron Formation shown in Sections 9 and 16, 

T. 34 S., R. 8 W. Deposited along plateau front near edge of Parowan 

Valley. Estimated thickness 30 m

Qlg Debris of Grand Castle formation-Deposit composed of broken blocks of 

pale-red and bluish-white conglomerate that contain well-rounded clasts 

mostly of quartzite and limestone. Deposited along plateau front near 

Parowan Valley edge. Estimated thickness 60 m

Qlk Debris of Iron Springs Formation Deposit composed of broken blocks of

yellowish-gray sandstone and some conglomerate. Deposited along plateau 

front near Parowan Valley edge. Estimated thickness 30 m

QTIi Landslide debris predominantly Isom Formation (late Pleistocene to 

Pliocene?)--Found in the southeast corner of quadrangle. Debris is 

predominantly composed of blocks of Baldhills Member of Isom Formation 

and may contain some Blue Meadows Member of Isom Formation. The 

landslides have broken away from Black Ledge, a long scarp-line cliff located 

in adjacent Red Creek Reservoir quadrangle located just east of southeast 

corner of quadrangle. The landslides partly fill the topographic low Yankee 

Meadows and probably broke away from scarps topographically above 

Yankee Meadows along Black Ledge. Estimated thickness 190 m

QTs Older alluvium (early Pleistocene and late Tertiary?)--Remnants of older

alluvial fans, composed of Tertiary volcanic and Cretaceous clasts of pebble 

to boulder size in a silty sand matrix. Estimated maximum thickness 25 m

Tmd Mafic dike (Miocene?) Medium-gray fine-grained, olivine- and plagioclasebearing dike. Intrudes tuffaceous sandstone of the Brian Head formation 

northeast of Parowan in Section 8, T. 43 S., R. 8 W.

Th Harmony Hills Tuff (Miocene)-Pale pink to grayish-orange-pink, moderately

welded, crystal-rich trachic andesitic-andesitic (Le Bas and others, 1986), ashflow tuff. Contains about 50 percent phenocrysts of plagioclase (63 percent), 

biotite (16 percent), hornblende (9 percent), quartz (7 percent), pyroxene (5 

percent), and trace of sanidine (Williams, 1967). Located in Parowan 

Canyon hi southwestern part of quadrangle. Source area is thought to be in 

the Bull Valley Mountains (Blank, 1959). First defined as member of 

Quichapa Formation by Mackin (1960), later elevated to formation by 

Williams (1967) and Anderson and Rowley (1975). Average K-Ar date of 

21.6 Ma based on biotite and plagioclase (Armstrong, 1970, and Noble and 

McKee, 1972) but more acceptable age of 22-22.5 Ma based on age of 

plutons and ash-flow tuff in the Iron Springs district that postdate the 

Harmony Hills tuff (Rowley and others, 1989; and Sider and others, 1990). 

Thickness as much as 15 m
Tcb Bauers Tuff Member of Condor Canyon Formation (Miocene)-Resistant, lightbrown-gray, densely welded rhyolite ash-flow tuff. Contains about 15 percent 

phenocrysts of plagioclase (55 percent), sanidine (35 percent), biotite (7 

percent), Fe-Ti oxides (3 percent), and trace amount of pyroxene (Anderson 

and Rowley, 1975). Characterized by conspicuous bronze biotite and lightgray flattened lenticules that may be flattened pumice. Source area is Clover 

Creek caldera (Rowley and Siders, 1988), within the Caliente caldera 

complex, Lincoln County Nevada (Ekren and others, 1977). Defined by 

Mackin (I960). ^Ar/^Ar Sanidine date is 22.78 Ma (Best and others, 

1989b). Thickness as much as about 15 m

Tmb Mudfiow and lava-flow breccia and tuffaceous sandstone (Miocene and

Oligocene)~Mudflow breccia contain clasts mostly of olive-gray pyroxenerich mafic lava, hornblende-rich mafic lava, gray-olive-black lava and flow 

breccia of intermediate composition, and lesser amounts of tuffaceous 

sandstone, Isom Formation, and Needles Range Group in a yellowish-gray 

and pale-yellowish-brown matrix of day. Mudflow breccia interbedded with 

pyroxene-rich mafic lava flow breccia and tuffaceous sandstone. Sandstone is 

nonresistant, olive gray and yellow gray, contains subangular to well-rounded 

grains of quartz, ferromagnesium minerals, and feldspars; sandstone is 

crossbedded in places suggesting eolian origin. Resembles but is not the 

tuffaceous sandstones of the formation of Brian Head (informal) and the 

Bear Valley Formation, a unit defined by Anderson (1971). Clasts of Isom 

Formation and Needles Range Group range from about 3 cm to about 200 m 

in length. These clasts and blocks are supported in a sandstone matrix. The 

large blocks are exposed one km east of Parowan Canyon in Section 12, T. 35 

S., R. 9 W. The mudflow breccias are the thickest in the P-Hill area, about 

one km southeast of Parowan, and the tuffaceous sandstone sequence is the 

thickest east of Parowan Canyon. These interbedded rock units may be 

equivalent to sandstone of the Bear Valley Formation and mudflow breccia 

of the Mount Dutton Formation of Anderson and Rowley (1975) mapped in 

the northern part of the Markagunt Plateau. Thickness as much as 200 m

Tib Baldhills Tuff Members of Isom Formation (Oligocene)--Many cooling units of 

moderately resistant to resistant, pale-red, grayish-red, pale-reddish-brown, 

pale-reddish-purple, and yellowish-gray densely welded, trachydacite (Le Bas 

and others, 1986), ash-flow tuff. Contains 5-20 percent phenocrysts, of 

mostly plagioclase and minor pyroxene, and Fe-Ti oxides in a glassy to 

devitrified groundmass (Anderson and Rowley, 1975). Unit characterized by 

elongated vesicles and secondary flowage structures that are both flattened 

and folded and resemble flowage features in lava flows. In the Red Hills 

area, west of map area, nine cooling units have been described but are not 

described in this quadrangle because of poor exposures (Maldonado and 

Williams, in press a,b). Commonly brecciated west of Maple Spring Hollow 

and poorly exposed in grabens. Unit defined by Mackin (1960). Caldera 

source of the Baldhills is probably at northwest edge of Escalante Desert 70 

km west of map area (Best and others, 1989a). K-Ar age 27 Ma (Best and 

others, 1989a). Thickness as much as about 275 m
Tn Needles Range Group, undivided (Oligocene)--Shown only as gravity slide blocks. 

May include Wan Wah Springs Formation and Cottonwood Wash Tuff. Wah 

Wah Springs Formation is a grayish orange pink, dacitic, moderately welded, 

simple cooling ash-flow tuff unit (Anderson and Rowley, 1975). Contains 

approximately 35 percent phenocrysts composed of the following: plagioclase 

(70 percent), hornblende (15 percent), biotite (5 percent), quartz (5 percent), 

Fe-Ti oxides (3 percent), sanidine (2 percent), and trace amounts of 

pyroxene, apatite, and zircon (Anderson and Rowley, 1975). Source area of 

formation is Indian Peak caldera (Best and Grant, 1987; Best and others, 

1989a; Best and others, 1989b) along central Utah-Nevada border. Defined 

by Mackin (1960) and later elevated to formational status by Best and Grant 

(1987). Average K-Ar age 29.5±0.5 Ma (Best and others, 1987). 

Cottonwood Wash Tuff is a grayish orange pink to light brownish gray, 

dacitic, moderately welded simple cooling ash-flow tuff unit (Anderson and 

Rowley, 1975). Contains approximately 40 percent phenocrysts composed of 

plagioclase (65 percent), hornblende (15 percent), quartz (10 percent), 

biotite (5 percent), Fe-Ti oxides (3 percent), sanidine (2 percent), and trace 

amounts of pyroxene, apatite, and zircon (Anderson and Rowley, 1975). 

Source area probably located in an alluvial valley between Fortification 

Range of eastern Nevada and Mountain Home Range of southwestern Utah 

(Best and others, 1989a). Defined by Mackin (1960) and later elevated to 

formational status by Best and Grant (1987). Average K-Ar age about 30.6 

(Best and Grant, 1987)

Tbi Mudflow breccia and lava flows (Oligocene)--Volcanic mudflow breccia and 

intermediate composition lava flows and flow breccia. Known only locally 

and poorly exposed in the eastern-central part of the quadrangle in T. 34 S., 

R. 8 W., Section 28. May correlate with poorly exposed parts of "local 

volcanic and sedimentary strata" units of Anderson and others (1987). 

Approximate thickness as much as 185 m

Tbh Brian Head formation (informal) (Oligocene)--Unit is mostly poorly resistant

tuffaceous sandstone interbedded with pebble- to boulder-size conglomerate, 

sandstone, minor limestone, and mudflow breccia. Tuffaceous sandstone is 

yellowish gray and light gray, laminated and crossbedded and contains 

abundant biotite that gives them a salt-and-pepper texture. Locally contains 

chalcedony zone. Conglomerate beds contain pebble- to boulder-size clasts 

of (1) predominantly ash-flow tuff, (2) lesser amounts of lava flows of 

intermediate composition, and (3) minor amounts of quartzite and light-gray, 

micritic limestone. Mudflow(?) breccia contains volcanic clasts and grains of 

quartz, feldspar, hornblende, pyroxene, and trace amounts of garnet. Map 

unit is equivalent to part of "local volcanic and sedimentary strata," a unit 

mapped on the Markagunt Plateau by Anderson and others (1987), 

"sedimentary and volcanic rocks of the Red Hills" in the Red Hills 

(Maldonado and Williams, in press a,b), and to upper-most part of "white" 

subunit of the Claron Formation of Anderson and Rowley (1975), and 

Doelling and others (1989). Brian Head formation is mapped separately 

from the uppermost part of the "white" subunit Claron Formation largely on 

the basis of its abundant volcaniclastic content. In the Red Hills, an ash-flow 

tuff present in the upper part of the sedimentary and volcanic rocks of the 

Red Hills unit is correlated to a similar tuff (Maldonado and Williams, in 

press a) dated at about 31.9 ± Ma based on biotite (Fleck and others, 1975). 

Poorly exposed with incomplete thickness as much as about 120 m
Tc Claron Formation (Eocene and Paleocene?)-Formation is composed of an upper 

part that is characterized by prominent cliff-forming white limestone beds 

with some sandstone and conglomerate, and a slope and a cliff forming lower 

part that contain fewer limestone beds of dominantly red to orange hues; 

these two parts have been referred to as the "white" and "red" subunits of the 

Claron Formation, respectively by Anderson and Rowley (1975). The "white" 

Claron is present locally with average thickness of about 60 m (Moore, 1982); 

contact with red Claron is gradational. The "red" subunit is composed of 

poorly to moderately resistant fluvial and lacustrine deposits predominantly 

of sandstone intercalated with mudstone, limestone, and pebble 

conglomerate beds; conglomerate clasts are well-rounded quartzite and 

limestone. "Red" subunit is mottled and varicolored in beds of pale red, pale 

reddish brown, moderate red, gray yellow, moderate reddish orange, very 

pale orange, and gray orange pink. Deposits are interpreted to be paleo-soil, 

that is, to have been altered by pedogenic processes (Mullett and others, 

1988; Mullett, 1989). Red and white subunit equivalent to "pink" subunit and 

lower part of the overlying "white" subunit of Doelling and others (1989) of 

the Claron Formation. Thickness is as much as about 395 m

Tgc Grand Castle formation of Goldstrand (1991) (Paleocene)-Type section is at 

Grand Castle in First Left Hand Canyon in Section 5, T. 35 S., R. 8 W. 

Divided into an upper red massive cliff-forming conglomerate, a middle 

white slope-forming sandstone, and a lower hoodoo or "beehive"-shaped cliffforming conglomerate by Goldstrand (1991). Contains well-rounded clasts of 

mostly quartzite and limestone and lesser amounts of sandstone and chert of 

pebble-, cobble-, and boulder-size. Some of the quartzite clasts resemble the 

Ordovician Eureka Quartzite, a unit exposed in western Utah and eastern 

Nevada. In the Red Hills, in the Parowan Gap area, correlative 

conglomerate deposits mapped as conglomerate of Parowan Gap 

(Maldonado and Williams, in press b), are found locally as channel fill on an 

erosional surface with angular unconformable relationships cut on underlying 

Iron Springs Formation. This unit was previously mapped as lower part of 

the Claron Formation by Threet (1952) in the Red Hills but in this report, 

unit was mapped separately from the Claron. Unit is correlative with the 

informal beehive unit of Moore (1982). Thickness ranges from 120 to 275 m

Kis Iron Springs Formation (Upper? Cretaceous)-Defined by Mackin (1947) for 

exposures in the Iron Springs mining district about 25 km southwest of 

quadrangle, where unit is about 1,000 m thick. Moderately resistant fluvial 

deposits composed of yellowish-gray, grayish-yellow, moderate-yellow, and 

dark-yellowish-orange, fine- to medium-grained, thin-bedded to massive 

sandstone and interbedded with some siltstone, shale, and conglomerate. 

Shale may make up 70 percent of formation locally (E.G. Sable, U.S. 

Geological Survey, written commun., 1992). Locally contains coal lenses. 

Contains several interbedded, thin, light-gray siltstone beds, approximately 5 

cm thick towards top of unit. Correlative with Free Thought unit of Moore 

(1982). Base not exposed. Exposed thickness about 335 m but may be as 

much as 940 m (Stokes, 1986)

Jc Carmel Formation (Middle Jurassic)-Shown only in cross section. Light-gray, 

bluish-gray, yellowish-gray, and tan, platy to massive, dolomitic and 

fossiliferous limestone; white, gray to light-olive-gray and reddish-brown to 

pale-red thin-bedded to massive, calcareous sandstone, interbedded with 

pale-red silty shale (Threet, 1952,1963). Exposed thickness about 250 m in 

the Red Hills (Threet, 1952) 10 km west of quadrangle
 Contact Dashed where approximate. Contacts between bedrock and surficial 

deposits approximately located

 - . Normal Fault Bar and ball on downthrown side; bar and ball not shown where 

sense of displacement not known; dashed where approximately located; 

dotted where concealed; queried where uncertain

»A» Tertiary thrust (?) fault Sawteeth on upper plate; arrow indicates direction and 

amount of dip; dotted where concealed

Boundary of megabreccia deposit interpreted as Miocene-Oligocene (?) gravityslide block-Showing parent bedrock unit symbol. Dotted where concealed; 

queried where uncertain

ii f. . JL. fjL. . Red Hills low-angle shear zone Double hachures on upper plate, approximately

located; dotted where concealed; queried where uncertain. Shear zone has 

detached part of unit Tbh and overlying rocks from underlying rocks and has 

been referred to as the Red Hills shear zone (Maldonado and others, 1990, 

1992). It may occur along contact between unit Tbh and base of Tertiary 

volcanic rocks, or in some areas within upper part of unit Tbh. Shear zone is 

arbitrarily placed at contact between unit Tbh and base of Tertiary volcanic 

rocks even though it may occur below that contact. Shear zone is variously 

characterized by comminuted rock, folding, and discordance in attitudes and 

thinning or omission of rocks overlying shear zone. Approximately located in 

geologic section

1 ' ' . J.. ^L Low-angle fault Dashed when approximately located, dotted where concealed.

Locally, fault becomes high-angle along part of its segment. Locally, lowangle fault may be same as the Red Hills shear zone.

Anticline Showing approximate trace of axial plane

Strike and dip of sedimentary beds and of foliation of pumice in ash-flow tuff 

Inclined
REFERENCES CITED

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Bulletin, v. 82, p. 1179-1205. 

Anderson, J J., livari, T A., and Rowley, P.D., 1987, Geologic map of the Little Creek Peak

quadrangle, Garfield and Iron Counties, Utah: Utah Geological and Mineral Survey Map

104, scale 1:24,000. 

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geology of southwestern High Plateaus of Utah: Geological Society of America Special

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Armstrong, R.L., 1970, Geochronology of Tertiary igneous rocks, eastern Great Basin and

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Best, M.G., Christiansen, E.H., and Blank, R.H., Jr., 1989a, Oligocene caldera complex and

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Best, M.G., Christiansen, E.H., Deino, A.L., Gromme, C.S., McKee, E.H., and Noble, D.C.,

1989b, Eocene through Miocene volcanism in the Great Basin of the Western United

States: New Mexico Bureau of Mines and Mineral Resources Memoir 47, p. 91-133. 

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rocks, Lincoln County, Nevada: U.S. Geological Survey Miscellaneous Investigations

Series Map 1-1041, scale 1:250,000. 

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High Plateaus region of Utah, in Anderson, J J, Rowley, P.D., Fleck, R J., and Nairn,

A.E.M., Cenozoic geology of southwestern High Plateaus of Utah: Geological Society of

America Special Paper 160, p. 53-61. 

Goddard, E.N., chm., and others. 1948, Rock-chart; Washington, National Research Council

(reprinted by Geological Society of America, 1975). 

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Cretaceous to Eocene rocks of southwest Utah: Reno, Nevada, University of Nevada at

Reno, Ph.D. dissertation, 205 p. 

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and early Tertiary sedimentary rocks of southwest Markagunt Plateau, Utah: Kent, Ohio,

Kent State University, M.S. thesis, 79 p. 

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classification of volcanic rocks based on the total alkali-silica diagram: Journal of

Petrology, v. 27, pt. 3, p. 745-750. 

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Utah Geological Association Publication 21,1992 Field Symposium, p. 315-323.

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quadrangle, Iron County, Utah: U.S. Geological Survey Geologic Quadrangle Map, GQ1712. scale 1:24,000. 

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quadrangle, Iron County, Utah: U.S. Geological Survey Geologic Quadrangle Map, GQ1713. scale 1:24,000. 

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southwestern Utah: Kent, Ohio, Kent State University M.S. thesis, 72 p. 

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Geological Society of America Abstracts with Programs, v. 2, no. 5, p. 120. 

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1 2

Table 1. 1Major-oxide, normative mineral, and trace-element composition of basalt of 

Water Canyon

^Sample number NP 9

Major-oxide composition

Si02

A1203 

3Fe203

FeO

MgO

CaO

Na2O

K20

TiO2

?205

MnO

Zrfy

Cr203

NiO

BaO

SrO

Total

Normative mineral composition

51.10

15.20 

2.87

6.30

8.27

8.25

3.50

1.92

1.37

0.61

0.14

0.02

0.03

0.02

0.16

0.13

99.87

or

ab 

an

di-wo

di-en

di-fs

hy-en

hy-fs

ol-fo

ol-fa

mt

cm

il

z

ap

Total

11.38

29.71 

20.15

7.33

5.00

1.75

3.26

1.14

8.69

3.35

4.17

0.04

2.61

0.03

1.42

100.0

Major elements determined by wavelength dispersive X-ray spectroscopy: J.S. Mee and

D.F. Siems, analysts.

^Trace elements determined by energy dispersive X-ray spectroscopy: J. Kent, analyst. 

3Fe203 calculated as TiO2 +1.5. 

4Sample location lat 37°52'25" and long 112°46'46M .
CORRELATION OF MAP UNITS

Oac

Ot

Ofa

QTfa OTIi 01 Qli QIc Olg Oik

Qbh \^

^^Qdh

Obw Obwc

U 

U

^/

\

J

nconformity

Op

nconform

QTs

'y x

<!

Holocene

late Pleistocene

middle Pleistocene 

early Pleistocene

Unconformity f r I I O C 6 H 6

Miocene

j- Miocene and Oligocene

Oligocene

Eocene and Paleocene (?)

Paleocene

Upper(?) Cretaceous

Middle Jurassic (Shown in cross s