A Transverse Fault in an Extended Terrane, the Currant Summit Fault, Nevada

UNLV Retrospective Theses & Dissertations

1-1-2000

A transverse fault in an extended terrane, the Currant Summit Fault, Nevada

Nathan David Williams University of Nevada, Las Vegas

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Repository Citation Williams, Nathan David, "A transverse fault in an extended terrane, the Currant Summit Fault, Nevada" (2000). UNLV Retrospective Theses & Dissertations. 1163. http://dx.doi.org/10.25669/6uj3-f36z

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A TRANSVERSE FAULT IN AN EXTENDED TERRANE, THE CURRANT

SUMMIT FAULT, NEVADA

Nathan D Williams

Bachelor of Science University of Kansas 1996

A thesis submitted in partial fulfillment of the requirements for the

Master of Science Degree Department of Geoscience College of Sciences

Graduate College University of Nevada, Las Vegas May 2000

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Thesis Approval u The Graduate College UniversitN’ of Nevada, Las Vegas

A p r il 28 ,20 00

The Thesis prepared by

Nathan D. Williams

Entitled

A Transverse Fault in an Extended Terrane.

the Currant Summit Fault. Nevada

is approved in partial fulfillment of the requirements for the degree of

______Master of Science ______

Examination Commiitec Chair

Dean o f the Graduate College

Exanuiiatiorf^ommittce Member

Examination Committee Member g~/^eg- ______

Graduate College Facultu Representative

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT

A Transverse Fault in an Extended Terrane: the Currant Summit Fault, Nevada

Nathan D. Williams

Dr W.J. Taylor, Examination Committee Chair Professor of Geoscience University of Nevada, Las Vegas

Transverse faults in extensional terranes strike parallel to subparallel to the

extension direction, are laterally continuous, and terminate abruptly. Problems of

transverse faults are addressed by analysis of the Currant Summit fault, an east-west

striking fault in east-central Nevada.

Mapping of rock units and structures allowed determination of the net slip along

the Currant Summit fault. The slip was calculated from an offset anticlinal hinge.

Motion is normal-left oblique with horizontal offset of 3300 m, throw of 1950 m and

heave of 70 m. Geometric calculations and field data constrain the fault dip to -87° N.

The name oblique-slip barrier transfer fault is proposed to describe this type of

fault. The oblique-slip barrier transfer fault: segments extensional provinces; may be

part of a larger transfer or accommodation zone; prohibits normal fault propagation; and

allows normal faults to transfer slip onto the transverse fault.

Ill

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

ABSTRACT...... iii

LIST OF FIGURES...... vi

ACKNOWLEDGEMENTS...... vii

CHAPTER 1 INTRODUCTION...... I

CHAPTER 2 STRATIGRAPHY...... 4 Paleozoic Stratigraphy ...... 4 Cenozoic Stratigraphy ...... 6

CHAPTER 3 TECTONIC BACKGROUND...... 8 Contraction ...... 8 Extension ...... 9

CHAPTER4 TRANSVERSE FAULTS...... II

CHAPTERS METHODS...... 16

CHAPTER 6 STRUCTURAL DESCRIPTIONS...... 18 White Pine Range anticline ...... 18 Sub-Tertiary unconformity ...... 20 Cenozoic extensional faults ...... 21 Currant Summit fault ...... 23

CHAPTER 7 STRUCTURAL AND TECTONIC INTERPRETATIONS ...... 26 The White Pine Range anticline...... 26 Cenozoic extension ...... 30 Kinematic analysis of the Currant Summit fault ...... 35 Relationship of Currant Summit fault to Regional Structures ...... 38

CHAPTER 8 SUMMARY AND CONCLUSION ...... 45

APPENDICES...... 65 Appendix 1. Stratigraphie descriptions ...... 65 Appendix 2. Using ArcView to create maps ...... 88

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. REFERENCES...... 93

VITA...... 103

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Figure 1 Map of Lineaments in the Central Basin and Range Province ...... 47 Figure 2 Regional Location Map Identifying the Basins, Ranges, and Study Area. 48 Figure 3 General Geologic Map of the White Pine, Horse, and Grant Ranges ...... 49 Figure 4 Geologic Map of the Study Area ...... 50 Figure 5 Paleozoic Stratigraphie Column...... 53 Figure 6 Cenozoic Stratigraphie Column ...... 54 Figure 7 Contractional and Extensional Structures of the Basin and Range Province ...... 55 Figure 8 Four Common End-Member Models of Transverse Faults ...... 56 Figure 9 Present Day and Restored Cross Sections ...... 58 Figure 10 Lower Hemisphere Stereoplot of Folds in the Study Area ...... 61 Figure 11 Stereoplot of Faults North and South of the Currant Summit Fault ...... 62 Figure 12 Stereoplot of Fracture Planes in Jasperoid Along Currant Summit Fault 63 Figure 13 Block Diagram of Oblique-Slip Barrier Transfer Fault ...... 64 Figure 14 ‘*®Ar/^^Ar Age Probability Curve o f Windous Butte Formation ...... 86

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I would like to thank the following sources for providing funding for this

project; American Association of Petroleum Geologists; the Bernard E French

Scholarship; Geological Society of America; Nevada Petroleum Society;

University of Nevada, Las Vegas Graduate Student Association; and the

University of Nevada, Las Vegas Department of Geoscience. Without this

funding, the project would not have been possible.

I would especially like to thank my advisor. Dr. Wanda J. Taylor, for her

continuous support, guidance, patience, and encouragement. I acknowledge my

committee members. Dr. Rodney Metcalf, Dr. Michael Wells, and Dr. George

Rhee, for their helpful reviews and input. I would also like to thank the following

people who have helped me complete this project: Dr. Terry Spell for dating a

volcanic unit from the study area. Dr. Rik Omdorff for assistance with ArcView,

all of the Geoscience faculty and staff for their support, and all of the graduate

students.

Lastly, I would like to thank my family for their endless encouragement

and support. I am very grateful for everything that they have provided for me.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1

INTRODUCTION

Normal faults are well documented structures of extensional terranes, but these

structures alone cannot fully explain the heterogeneous architecture most extensional

terranes exhibit. Other structures must be present to accommodate the asymmetric and

heterogeneous extension commonly found in extended regions. Transverse faults are

commonly these required structures.

Transverse faults, faults that strike parallel to subparallel to the extension

direction, are commonly laterally continuous and terminate abruptly. They are

commonly identified as strike-slip faults, deep crustal structures independent of

extension, or oblique-slip normal faults (e.g., Duebendorfer and Black, 1992; Rowley,

1998). These faults are recognized in many extended regions including the North Sea

(Gibbs, 1984), East Africa Rift (Rosendahl, 1987; Morley et al., 1990), Gulf of Suez

(Moustafa, 1997; McClay and Khalil, 1999), and the Basin and Range province

(Wernicke et al., 1988; Faulds et al., 1990; Faulds and Varga, 1998).

Many transverse faults in the Basin and Range province have been identified

as parts of east-west trending “lineaments”, but these structures are not completely

understood (Fig. 1) (Ekren et al., 1976; Duebendorfer and Black, 1992). Lineaments

are surficial lines drawn where researchers find an alignment of faults, mineralization.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. zones of brecciation, offset ranges, or aeromagnetic anomalies (Ekren et al., 1976;

Duebendorfer and Black, 1992; Rowley, 1998).

An understanding of transverse faults is needed to explain the evolution and

development of extended terranes in general, and the Basin and Range province, in

particular. Regional structural problems in the eastern Great Basin are addressed in

this study by detailed analysis of the Currant Summit fault, Nevada, a transverse fault

separating the southern White Pine Range from the northern Horse Range (Fig. 2).

The Currant Summit fault is thought to be near the eastern limit of the Pritchards

Station lineament (Figs. 1 and 2) (Moores et al., 1968; Ekren et al., 1976; Rowley,

1998).

This thesis focuses on the kinematics of and structures associated with the

Currant Summit fault, with the goal of deciphering the role of transverse faults in

extensional terranes. The role of transverse faults in extension can then be explained.

This paper will: (1) describe and kinematically analyze the Currant Summit fault, (2)

document and analyze low- and high-angle faults and folds, and (3) develop a model

to describe the kinematics and geometries of the Currant Summit fault and faults offset

by or terminated by the transverse fault.

In this study, detailed geologic mapping reveals that the Currant Summit fault

is a normal left-oblique slip fault that offsets folded Paleozoic strata. Geometric

relationships between the folded Paleozoic strata and the overlying Oligocene volcanic

rocks suggest that the folding is pre-Oligocene. Analysis of the Currant Summit fault

suggests the fault has been active since the early Tertiary, and has remained active into

the Quaternary. The new data are used to develop a model for the Currant Summit

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fault, the barrier transfer fault model, to explain the role of the Currant Summit fault in

regional extension and to relate this style of faulting to other extended regions.

The study area is located in the White Pine and Horse ranges of Nye County,

Nevada. The White Pine Range, north of the Currant Summit fault, is a north-trending

range consisting of Paleozoic strata, dominantly carbonate units, overlain by Cenozoic

sedimentary and volcanic units (Figs. 3 and 4; Plate 1 ). The exposed Paleozoic

section is approximately 7000 m (23,000 feet) thick and the Cenozoic section is

approximately 1200 m (4,000 feet) thick (Moores et al., 1968; Hose and Blake; 1976;

Kleinhampl and Ziony, 1985; Langrock, 1995). Tertiary plutons (34.5 Ma) are

exposed northwest of the study area (Moores et al., 1968; Taylor et al., 1996). The

Horse Range, south of the Currant Summit fault zone and in the southeastern portion

of the study area, consists of two north-trending ridges of Cambrian to Mississippian

units, correlative to units in the southern White Pine Range, and a fault-bounded basin

between ridges that contains Cenozoic volcanic units (Figs. 3 and 4; Plate 1) (Moores

et al., 1968).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2

STRATIGRAPHY

An understanding of the local stratigraphy is required to correctly correlate

rocks offset by faults. The apparent type and amount of offset of faults can be readily

constrained if well defined strata are employed. The timing and number of episodes of

faulting can also be constrained if the ages of strata are known.

Paleozoic units are unconformably overlain by previously undifferentiated

Cenozoic volcanic and sedimentary rocks in the White Pine and Horse ranges (Figs. 4,

5 and 6; Plate 1) (Humphrey, 1960; Moores et al., 1968; Tracy, 1980; Gurrerro, 1983;

Kleinhampl and Ziony, 1985; Langrock, 1995). No Mesozoic rocks crop out within

the study area. The total thickness and detailed rock descriptions of the Paleozoic and

Cenozoic units located in the study area are compiled in Appendix A.

Paleozoic Stratigraphy

The Paleozoic rocks are part of the passive margin marine sequence exposed

throughout central and eastern Nevada. Previous researchers applied eastern Nevada

formation names and subdivisions to the White Pine and Horse range Paleozoic rocks

(e.g., Kellogg, 1963; Lumsden, 1964; Moores et al., 1968). Formation names assigned

by Lumsden (1964) and Moores et al. (1968) were used for this study, however,

thicknesses and subdivisions differ for some o f the Lower Paleozoic units (Fig. 5).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Three thin subdivisions of the Cambrian Pole Canyon Limestone were identified by

Lumsden (1964). Two subdivisions of the Pole Canyon Limestone are used in this

study. The lower unit consists of a dark gray limestone (3 m thick) overlain by a 10m

section of thinly bedded limestone and shale. The upper unit is a 20 m thick massive

white to light-gray limestone and dolomite unit.

Other researchers in this area used different stratigraphie nomenclature. Hood

(1985) stated that the Lower Cambrian in this region is not the same as the

transgressive sequence seen in other stratigraphie sections in the Great Basin. The

middle Pole Canyon Limestone member identified by Lumsden has not been identified

in other sections in the same stratigraphie position. Hood (1985) gave part of the unit

a new name, the Currant Summit Limestone, because it was unlike previously reported

units in surrounding areas. This research includes this thin unit in the lower Pole

Canyon member.

Lumsden (1964) and Moores et al. (1968) identified three subdivisions of the

Ordovician Pogonip Group in the Horse Range, but they did not subdivide the units in

the southern White Pine Range. Three subdivisions of the Pogonip Group are used in

this study: Goodwin Formation, a 58-100 m thick light blue-gray limestone above the

light-gray cherty limestone of the Upper Cambrian Windfall Formation; Ninemile

Formation, a 335-460 m thick orange shale with intermittent 1-5 m thick limestone

ledges; and Antelope Valley Limestone, a 380-490 m thick unit of thick bedded

medium-gray limestone (Fig. 4). Previous research indicated that the Goodwin

Formation is 475 m thick in the Horse Range (Wire, 1961) and 550 m thick in the

Grant Range (Cebull, 1970). The lower contact with the Cambrian Windfall

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Formation is a gradational contact and the division between the Cambrian and

Ordovician may have been placed at different stratigraphie intervals in different

locations. The contact here was placed at the top of a light-gray limestone unit, with

intermittent chert, and below shaley slopes present below a 2 m thick fossiliferous

limestone ledge. The Windfall Formation in the study area is thicker than in previous

interpretations because the contact was probably placed in a different stratigraphie

position.

Cenozoic Stratigraphy

Cenozoic volcanic and sedimentary units unconformably overlie the east-tilted

Paleozoic section in the White Pine and Horse ranges (Fig. 6) (Moores et al., 1968;

Langrock, 1996). Cenozoic volcanism began in the Eocene along with or just after

extension in the northern Basin and Range province. Onset of volcanism migrated

from north to south across the northern Basin and Range province in generally east to

west trending belts beginning in 44 Ma and continuing to 18 Ma (Stewart and Carlson,

1976; Best and Christiansen, 1991; Axen et al., 1993).

Previous researchers did not differentiate the volcanic rocks in the study area

(Lumsden, 1964; Moores et al., 1968). However, distinct units were identified and

mapped for this study and correlated to other Tertiary volcanic rock units outside the

study area (Appendix A; Fig. 6). Oligocene volcanic rocks are the oldest Cenozoic

units documented in the study area (Figs. 3 and 6; Plate 1) (French, 1994). The source

for many of the volcanic units in the Currant Summit fault area, including the Stone

Cabin and Windous Butte formations, is the Central Nevada Caldera Complex, a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. cluster of calderas that began erupting in the Oligocene (Fig. 2) (Best et al., 1993).

The caldera complex is located to the west and southwest of the study area within the

Pancake Range and Railroad Valley (Fig. 2) (Best et al., 1993).

An undated intrusion, the Currant stock, is located in the north-central portion

of the study area. The unit is an altered granitic porphyry that intruded Mississippian

Chainman Shale as evidenced by the angle between bedding in the Chainman Shale

and the contact. Near the edge of the stock the shale is locally metamorphosed to a

light tan color, and a block of shale surrounded by the porphyry may be a roof pendent

or a xenolith. The unit contains large highly altered quartz crystals (1-5 mm), with

biotite and feldspar in a fine-grained green to brown matrix. The unit is pervasively

altered making dating difficult. The stock is older than the 35.3+0.04 Ma Stone Cabin

Formation that overlies that overlies the stock.

Tertiary and Quaternary sedimentary units are present in the study area and are

important units for the identification of recent faulting (Figs. 4 and 6; Plate I).

Dissected alluvial fans, undissected alluvial fans, and active alluvium formed afier

extension began and some units are offset by recent faults locally.

Silicification, the replacement of calcite by quartz, is common throughout the

study area. Red, pink, brown, or white jasperoid was precipitated along many faults

and along sedimentary contacts. In the central portion of the study area, the jasperoid

is exposed along the Currant Summit fault and along the north-south striking contact

between the Chainman Shale and Joana Limestone (Fig. 4; Plate 1).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTERS

TECTONIC BACKGROUND

Mesozoic Contraction

The Paleozoic marine sedimentary units within the western U.S. were thrust

faulted and folded during the formation of the Sevier orogenic belt and the central

Nevada thrust belt. The Mesozoic to Eocene Sevier orogenic belt consists of thin-

skinned east-vergent folds and thrusts in a generally northeast-trending belt that

extends from southern Nevada to southern Idaho (Fig. 7) (e.g., Armstrong, 1968;

Taylor et al.. 1993).

Recent research describes a geographically distinct but probably coeval fold

and thrust belt within the Sevier hinterland, the central Nevada thrust belt (Taylor et

ai., 1993; Taylor et al., 2000). The central Nevada thrust belt is bracketed between the

Permian and Late Cretaceous, and consists of east- and west-vergent folds and thrusts

with steeply dipping ramps and large stratigraphie separation. These geometries are

typical of the trailing edge or hinterland portion of a contractional orogenic belt as

opposed to foreland deformation with long flats and large offsets (Taylor et al., 1993).

The belt is 250 km long through central Nevada from Alamo to Eureka, and includes

the northern Eureka thrust belt (Speed et al. 1988; Taylor et al., 1993).

The White Pine and Horse ranges lie within the central Nevada thrust belt and

in the hinterland of the Sevier orogenic belt (Fig. 7). Langrock (1995) and Taylor et

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. al. (2000) identified large-scale and small-scale folds as central Nevada thrust belt

structures in the central White Pine and Grant ranges. The folds and faults

accommodate over 6 km of horizontal contraction in the White Pine Range (Lumsden,

1964; Moores et al., 1968). Previous research also identified folded Paleozoic rocks in

the Horse Range, a north-trending anticline in the west and an overturned anticline in

the east (Moores et al., 1968).

Cenozoic Extension

Mesozoic folds and thrust faults are cut by high- and low-angle normal faults

throughout much of the eastern Great Basin, including in the White Pine and Horse

ranges (Fig. 3) (Moores et al., 1968; Taylor et al., 1989). Overthickening of the crust

during the Sevier orogeny may have initiated extension in some regions within the

Basin and Range province in the late Cretaceous-early Eocene as regional back-arc

thrusting ended (e.g.. Wells et al., 1990; Camilleri, 1992; Hodges and Walker, 1992;

Axen et al., 1993; Wells et al., 1994; Taylor et al., 1999a).

Multiple episodes of extension followed the late Cretaceous to Eocene

extension in a broad area of western North America, from Canada to southern Mexico.

The episodes are characterized by both high- and low-angle normal faults that range

from Eocene to Quaternary in age (e.g., Taylor et al., 1989; Axen et al., 1990; Switzer,

1996; Wells, 1997; Miller et al., 1999). Large-magnitude Oligocene to Miocene

extension associated with low-angle normal faults is recognized in many Great Basin

ranges including the Grant, Horse, Pancake, and White Pine ranges (Figs. 2 and 3)

(e.g., Fryxell, 1988; Camilleri, 1992; Wernicke, 1992). Two major low-angle normal

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10

faults in the southwestern White Pine Range have been mapped in detail as the

Blackrock fault (Moores et al., 1968; Langrock, 1995; Lisenbee and Kieffer Rowe,

1996) or White Pine detachment (Walker et al., 1992), and as the Silver Spring

detachment (Figs. 2, 3, and 4) (Moores et al., 1968; Lisenbee, 1996; Taylor et al.,

1996). These low-angle normal faults and associated upper plate faults attenuate the

section, are non-planar, and generally place younger rocks over older rocks (Moores et

al., 1968).

Low- and high-angle normal faults of Oligocene to Quaternary age are exposed

throughout the eastern Great Basin. High-angle normal faults truncate and offset the

low-angle detachment faults and Tertiary rocks in many places, including the White

Pine and Horse ranges (Fig. 4; Plate 1). Offset of high-angle faults by some low-angle

faults suggests that some low-angle faulting occurred after high-angle faulting

(Moores et al., 1968; Fryxell et al., 1996).

The latest episode of faulting is Pliocene to Holocene in age and responsible

for the present Basin and Range province topography. High- and low-angle faults

bound mountain ranges forming the large basins and high ranges of the Great Basin

(Effimoff and Pinezich, 1981; Anderson et al., 1983). The Railroad Valley fault, a

high-angle range-bounding fault, strikes north-south along the western margin of the

White Pine and Grant ranges (Fig. 2) (Moores et al., 1968). The west-dipping normal

fault has more than 1800 m (6000 feet) of throw and aided in the development of

central Railroad Valley (Grabb, 1994). Truncation of recent alluvial terraces suggests

Late Pleistocene-Holocene movement along the Railroad Valley fault (Dohrenwend et

al., 1991; Fryxell et al., 1996).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4

TRANSVERSE FAULTS

Transverse faults, which strike parallel to subparallel to the direction of

extension, are required to explain the three-dimensional geometries found in extended

regions, including the Basin and Range province (Wernicke, 1992; Faulds and Varga,

1998), the North Sea (Gibbs, 1984), and the East African Rift (Rosendahl, 1987;

Bosworth, 1989; Bosworth and Morley, 1994). Many transverse features, called

lineaments, have been recognized in the Basin and Range province but all are not

necessarily transverse faults (Fig. 1) (e.g., Rowley et al., 1978; Duebendorfer and

Black, 1992). Lineaments are commonly defined by alignment of volcanic centers,

aeromagnetic discontinuities, mineralization, and hydrocarbons (Ekren et al., 1976;

Rowley et al., 1978; Grabb, 1994).

Types of transverse faults

A plethora of models have been proposed by different researchers to explain

transverse faults (e.g., Gibbs, 1984; Bosworth, 1985; Rosendahl, 1987; Wernicke,

1992; Faulds and Varga, 1998). Recent work by Faulds and Varga (1998) combined

previous research to create a nongenetic classification of these structures. Faulds and

Varga (1998) classify the regional segmentation structures, which may be transverse

faults, into two major divisions, accommodation zones and transfer zones. These

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12

subdivisions and others are based on the strike or trend of the structure, fault

geometry, and fault polarity.

The models most relevant to this study are transfer fault, accommodation zone,

overprinted normal fault, and overprinted strike-slip fault. Fault geometries, slip

direction, along strike changes in displacement, and lateral fault extent distinguish the

different fault models. Field observations needed to identify the appropriate model

include stratigraphie separation, kinematic indicators, piercing points, and map

patterns.

The accommodation zones accommodate strain resulting from overlapping or

opposing sets of normal faults (Fig. 8a). Accommodation zones are oriented oblique,

normal or parallel to the direction of extension and may result in anticlinal and

synclinal structures. The zones may have torsional or strike-slip components (Fig. 8a)

(van der Pluijm and Marshak, 1997; Faulds and Varga, 1998). Faulds and Varga

(1998) classified accommodation zones into antithetic and synthetic accommodation

zones. The classification schemes rely on the relative direction of movement along

the faults associated with the accommodation zone (Fig. 8a). Facing breakaway zones

of normal half-graben faults create a topographic high within an extensional basin in

the low-relief accommodation zone or antithetic accommodation zone models

(Rosendahl, 1987; Faulds and Varga, 1998). Associated faults dip toward the center

of the basin to produce a fault-formed anticline (Fig. 8a) (Faulds and Varga, 1998). In

the high-relief or synthetic accommodation zone model, the normal faulting causes a

fault formed syncline (Fig. 8a). In this model, the strata will dip in opposite directions

and faults will dip away from the hingeline and central high-relief graben (Fig. 8a).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13

The transverse accommodation zone is oriented parallel to subparallel the direction of

extension and may have characteristics of the antithetic and synthetic accommodation

zones as well as faults oriented parallel to the extension direction (Fig. 8a).

In the transfer fault models, extension direction is parallel or oblique to the

strike of the transverse fault (Fig. 8b) (Wernicke, 1992; Faulds and Varga, 1998).

Strike slip occurs along a fault zone, the transfer fault, between two separate sets of

normal faults. Normal faults terminate at or continue into the transfer fault and slip

from one normal fault is relayed along the transfer fault as oblique or strike slip and

onto the next normal fault. This model permits different amounts of extension on

opposite sides of the transverse transfer fault (Faulds and Varga, 1998). The overall

motion along the fault may be strike-slip, but segments of the transfer zone can exhibit

normal, reverse, or oblique slip. The model also allows constriction between the two

normal faults (antithetic transfer fault) (Faulds and Varga, 1998). A systematic

decrease in displacement along the transfer fault may occur with increasing distance

from the associated normal faults. Displacement along the transfer fault will increase

if associated normal faults are synthetic, and will decrease if the associated normal

faults are antithetic.

In contrast to the above models, transverse faults may form and be active later

than the faults on either side of them. The transverse fault may be a younger normal

fault which offsets older normal faults (Fig. 8c) (e.g., Overtoom and Bartley, 1996;

Switzer, 1996). The normal fault will have the largest component of displacement in

the vertical direction and will continue along strike past the older normal faults. The

normal faults cut by the transverse fault will correlate across it.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14

The transverse fault could, alternatively, be a strike-slip or oblique-slip fault

younger than the normal faults on either side of it (Fig. 8d). In this case, the fault will

continue along strike past the faults perpendicular to it. The separation of truncated

faults will be similar to the separation found in the stratigraphie units. The number of

truncated faults will be the same across the transverse fault and individual faults may

be matched across it.

The models presented above are end members of transverse structures. Many

transverse faults may be explained by a combination of the models. Accommodation

zones may have components of transfer fault zones and transfer faults may have

accommodation zone characteristics. A strike-slip fault may have components of

normal slip. Transverse faults that combine models are identified as composites

(Faulds and Varga, 1998). The fault may also act locally as an oblique-slip fault but

be a portion of a transfer fault or another type of transverse fault on a larger scale

view.

Many transverse faults are recognized in Nevada and western Utah, but their

kinematics are complicated and not completely understood (Fig 1 ) (Duebendorfer and

Black, 1992; Faulds and Varga, 1998). Many of these faults form all or parts of

lineaments that are over 200 km in length in the Great Basin (Ekren et al., 1976).

These east-west trending structural features have been identified as long-lived deep-

crustal structures independent of extehsion (Ekren et al., 1976; Hurtubise, 1994),

strike-slip faults accommodating differential extension (Grabb, 1994; Switzer, 1996),

strike-slip fault systems which link faults and are coeval with extension (Faulds et al.,

1990), and as oblique-slip to normal faults accommodating north-south extension

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15

(Overtoom and Bartley, 1994). The transverse structures commonly offset or truncate

north-trending mountain ranges, and the movement directions along each fault can

appear contradictory (Duebendorfer and Black, 1992).

The Currant Summit fault is the eastern end of the Pritchards Station lineament

(Figs. 1, 2 and 3) (Ekren et al., 1976). The fault strikes generally east-west along the

southern end of the White Pine Range and northern end of the Horse Range at

approximately 38°48’ latitude (Ekren et al., 1976). The fault continues west across

Railroad Valley and through the Pancake Range near 38° 45’ latitude (Figs. 1. 2, and

3) (Ekren et al., 1976). The fault may also truncate the Silver Spring low-angle fault

and a broad north-trending anticline in the southern White Pine Range (Moores et al.,

1968; Langrock, 1995).

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METHODS

Standard geologic mapping techniques were used to map approximately 60

square kilometers (approximately 23 square miles) of the southern White Pine and

northern Horse ranges (e.g., Compton, 1985). Geologic data were collected at a scale

of 1:24,000 and placed on the White Pine Peak and Currant Summit USGS 7.5 minute

topographic quadrangle maps. Air photographs at 1:24,000 scale were also used to aid

in geologic interpretation of the study area.

Pétrographie studies and point-count analyses of thin sections for seven

stratigraphie units were completed. Five hundred points were collected for each unit

using a pétrographie microscope. Two thin sections perpendicular to one another were

point counted (approximately 250 points each) with a fixed grid system. These data

were used to identify and correlate the volcanic rocks in the northeastern portion of the

study area.

Deformed-state cross sections and retrodeformed cross sections were produced

after mapping to analyze the amount and type of movement along the Currant Summit

fault, low-angle normal faults, and high-angle normal faults. Standard techniques

were used to restore the deformation along the transverse fault and Cenozoic normal

faults (Ragan, 1968; Dahlstrom, 1969; Groshong, 1989; Schultz-Ela, 1991; White,

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1992). The three-point method was used to calculate the strike and dip of faults where

the attitude of the fault was not measurable in the field.

Stereoplots were used to systematically analyze fault orientations north and

south of the Currant Summit fault. Stereoplots were also used to constrain the

orientation of the axial surface and fold axis of an anticline in the western portion of

the study area. R. Allmendinger’s stereonet program for Macintosh was used.

An ^°Ar/^^Ar date was obtained on the upper volcanic unit in the study area.

Several kilograms of sample were collected and weathered surfaces were removed.

The sample was then crushed and sieved at facilities in the University of Nevada, Las

Vegas, Geoscience Department. Clean and clear sanidine crystals were hand picked

and all groundmass was removed firom the crystals by sonicating and soaking the

crystals in a 1% Hf bath for 20 minutes.

Ten single sanidine crystals were analyzed by the ‘’°Ar/^^Ar laser fusion

technique at the Nevada Isotope Geochronology Laboratory facilities run by Dr. T.

Spell at the University of Nevada, Las Vegas. Fish Canyon Tuff sanidine (ANU 92-

176) was used as the flux monitor in calculating ages of the samples. LabView

software (written by B. Idelman, Lehigh Univ.) was used for data reduction and age

calculations.

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STRUCTURAL DESCRIPTIONS

The Currant Summit fault separates the White Pine Range from the Horse

Range. The fault also offsets an anticline exposed in Cambrian to Pennsylvanian

sedimentary units. High- and low-angle normal faults north and south of the Currant

Summit fault indicate at least three episodes of faulting, and faults terminating at the

Currant Summit fault indicate that the transverse fault was active during all episodes

of extension. Offset stratigraphie units and a piercing point formed by the anticline

constrain the amount and timing of movement along the Currant Summit fault. The

following data can be used to create a model for the Currant Summit fault.

White Pine Range anticline

Upright and open sub-horizontal anticlines in both the western White Pine and

Horse ranges fold Paleozoic strata (Figs. 4 and 9; Plates 1,2,3, and 4). The present-

day attitude of the axial surface of the slightly east-vergent anticline in the White Pine

Range is N9°E, 83° W and the hingeline plunges and trends 1°, S8°W. South of the

Currant Summit fault, in the Horse Range, the strike and dip of the axial surface is

N11°E, 74°W and the hingeline plunges and trends 5°, SI 1°W (Fig. 10). The axial

surface of the anticline is west-vergent (0-5°) after Cenozoic tilting is removed.

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Similar axial surface and fold axis attitudes, as well as size and shape of the anticlines

in the north and south suggest that a single anticline is offset by the Currant Summit

fault. In addition, the trace of the axial surfaces end at the east-west striking fault.

The attitudes of the Paleozoic sedimentary units are similar north and south of

the Currant Summit fault. The bedding on the eastern limb of the fold dips 30°-60° E

with dips decreasing near the center of the anticline. A small anticline, probably a

parasitic fold, crops out in the Ordovician Antelope Valley Limestone and Ninemile

Formation south of the Currant Summit fault (Figs. 9c and d; Plates 1 and 3). The

extreme western edges of the ranges expose the western limb of the fold. The beds in

this limb strike NNW and dip 10°-30° W.

The Paleozoic units exposed in the core of the anticline are different north and

south of the Currant Summit fault (Fig. 4; Plate 1). To the north, the Cambrian

Windfall Formation crops out in the core of the anticline. South of the Currant

Summit fault the Lower Cambrian Prospect Mountain Quartzite is exposed in the fold

core, therefore, deeper parts of the fold crop out south of the Currant Summit fault

than in the north.

Moores et al. (1968) named the fold the White Pine Range anticline in the

White Pine Range but the fold in the Horse Range was left unnamed. This research

uses the name White Pine Range anticline to include the anticline both north and south

of the Currant Summit fault.

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Sub-Tertiary unconformity

Tertiary volcanic rocks overlie the folded Paleozoic carbonate rocks, however,

few localities within the study area expose the contact. The contact is an angular

unconformity between the gently dipping Tertiary volcanic units and the underlying

40°-50° E dipping eastern limb of the White Pine Range anticline. No normal faults

are exposed that would cause this angular unconformity

Paleozoic units north of the Currant Summit fault are separated from the

Tertiary volcanic rocks by the Currant stock and Tertiary to Quaternary alluvium (Fig.

4; Plate 1 ). The volcanic rocks dip between 6° and 22° E. The Upper Paleozoic units

dip 40° E. Removal of the post-Tertiary tilting indicates that the pre-Tertiary dip of

the Paleozoic units would be 20°-34° E.

South of the Currant Summit fault, the Tertiary ash fall tuff imit is in contact

with Upper Paleozoic strata in the southeastern part of the study area (Figs. 4 and 9c;

Plates 1 and 3). This tuff is a thin veneer on top of Devonian carbonate units. The

volcanic unit dips 22° E and the Paleozoic units dip 40°-50° E. In another small

outcrop, volcanic rock is in contact with Mississippian Joana Limestone and the

Diamond Peak Formation on the eastern edge of the Horse Range. The volcanic unit

dips 10°-20° E and the Ely Limestone dips 35° E. The pre-Tertiary dip of the

Paleozoic rocks would be 40° to 15° E.

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Cenozoic extensional faults

High-angle normal faults occur throughout the study area (Figs. 4 and 9; Plates

1-4). These faults cut all the Paleozoic units and the Tertiary volcanic units. Faults

were recognized based on offset units, breccia, or fault scarps. A majority o f the faults

strike north-northwest to northeast and dip between 40° and 90° E and W (Figs. 4 and

11). The faults cut the folded Paleozoic units at 50°-90°, oblique to bedding. These

faults are generally planar but listric faults occur in the eastern portion of the study

area (Figs. 4, and 9; Plates 1-3). Faults that are either planar or curved along strike are

also present, but the majority of the faults are nearly planar.

North of the Currant Summit fault, faults that strike north-northwest cut faults

that strike north-northeast and dip 80°-90° E or W (Fig. 4; Plate 1 ). North-northwest-

striking faults exposed in the Devonian and Ordovician units north of the Currant

Summit fault offset some of these faults (near point D on Plate 1 and Fig. 4).

Crosscutting faults or fault sets are not present in the map area south of the Currant

Summit fault.

More faults crop out to the north of the Currant Summit fault than to the south

(Figs. 4 and 11; Plate 1). North o f the Currant Summit fault, 45 faults were mapped

with a majority of the faults dipping between 70° and 90° E or W (Fig. 11). Based on

cross section analysis these faults together accommodate over 1000 meters of east-

west extension (Figs. 9a and 9b). Faults south of the Currant Summit fault strike

north-south and dip steeply. Twenty-two faults accommodate 120 m o f east-west

extension (Figs. 9c and 9d). The non-matching orientations and different numbers of

faults indicate that the high-angle faults do not cut through or are not offset by the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Currant Summit fault, but end at the Currant Summit fault. If faults were offset by the

Currant Summit fault, they would be exposed within the study area because the study

area has an east-west width greater than the east-west offset on the Currant Summit

fault (see Chapter 7).

Low-angle normal faults crop out in the western part of the study area (Figs. 4

and 1 Ic; Plate 1). Eleven low-angle fault surfaces were measured on two major low-

angle faults in the White Pine Range (Fig. 1 Ic). The low-angle-faults were identified

by offset stratigraphy, brecciation, and small scale footwall folds. The faults have dips

of < 40° NNW and SW. The poles to the fault planes are scattered suggesting that the

low-angle faults are multiple faults or non-planar faults (Fig. 1 Ic). High-angle faults

offset these low-angle faults, which also may account for scatter on the stereoplot.

The low-angle fault surfaces northwest of the Currant stock appear to have

transported east-dipping strata generally to the west. One low-angle fault transported

Devonian Simonson Dolomite to the west over the east-dipping Devonian Sevy

Dolomite (Fig. 4; Plate 1). Another exposure of the same fault appears to have placed

Ordovician Eureka Quartzite generally to the west over the Ordovician Fish Haven

Dolomite. These exposures align when younger fault offsets are removed, indicating a

single low-angle fault.

A second low-angle fault in the western part of the study area is within the

Cambrian Windfall Formation and may correspond to a low-angle-fault exposed in the

Cambrian Pole Canyon Formation south of the Currant Summit fault (Figs. 4 and 9e).

Transport direction is unclear because the fault is nearly parallel to bedding.

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Currant Summit fault

The trace of the Currant Summit fault trends east-west through the middle of

the study area (Figs. 3 and 4; Plate 1). The fault is defined by a ridge of jasperoid in

the central portion of the study area, where it places Devonian units on the north

against Lower Cambrian strata on the south (Figs. 3 and 4, Plate 1). Two splays of the

fault, visible in the western portion of the study area, together place east-dipping

Ordovician carbonates on the north against the Lower Cambrian Lincoln Peak

Formation on the south (Fig. 4; Plate 1).

In the eastern portion of the study area the fault is exposed in Quaternary-

Tertiary (?) alluvial fan sediments. Several 5-10 m high east-striking degraded fault

scarps are present in the alluvium north of the east-dipping carbonates in the Horse

Range (Figs. 3 and 4; Plate 1). The scarps vary in height and are located at different

latitudes indicating several fault strands between 300 and 600 m north of the bedrock

outcrops of the Horse Range. A small offset and a large abundance of calcite veins are

present in weakly lithifîed sediments along one of the fault scarps. This portion of the

fault has a strike and dip of N66°E, 66°N. The fault continues to the east through

Tertiary volcanic rocks. Conservative fault scarp degradation calculations (Keller and

Pinter, 1996) suggest that some movement occurred at <45 ka on the Currant Summit

fault.

The Currant Summit fault tip line is ~20 km to the E of the study area (Hose

and Blake, 1976). There, a large ridge of Devonian Guilmette Formation is

continuous across the strike-projection of the fault (Hose and Blake, 1976). The tip

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line is also evidenced by the decrease in east-west extension on north-south striking

faults in the northeastern part of the study area (Plate 2).

Field observations and three-point problems indicate a general dip between

87°-90° N for the Currant Summit fault. Few fault surfaces are preserved but fault

surfaces with an east-west strike and dips of 87° N and 88° S are exposed in the

western White Pine Range where a narrow outcrop of Cambrian Windfall Formation

is faulted against Ordovician units to the north and lower Cambrian units to the south

(Fig. 4; Plate 1). Fracture surfaces with a wide array of strikes and dips were

identified in the jasperoid along the Currant Summit fault in the central portion of the

map area (Fig. 12). The 25 measured fiacture surfaces appear to be widely scattered

and do not define a single fault.

Mapping of the Currant Summit fault by Lumsden (1964), Moores et al.

(1968), and Castor and Hulen (1996) identified varying dips for the Currant Summit

fault. Dips of 70° N near the Gold Point Mine and 15° N and S in the western White

Pine Range were identified by Lumsden (1964), suggesting that the Currant Summit

fault changes from a high- to a low-angle fault along strike. Dips of 30-80° N are

recorded by Castor and Hulen (1996) south of the Gold Point Mine area in the central

portion of the study area. These dips may be from surfaces within the jasperoid along

the Currant Summit fault and not actual fault surfaces because they have variations

similar to those of the surfaces in the jasperoid. The steep fault dip identified in this

research suggests a high-angle fault with only a limited range in dip.

The net slip on the Currant Summit fault was calculated from the offset

anticlinal hinge of the White Pine Range anticline. The intersection of the hingeline

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with the Currant Summit fault creates a piercing point. Motion is normal-left oblique

with strike-parallel offset o f2700 m, dip slip of 1952 m, throw of 1950 m, heave of 68

m. and net slip of 3330 m at 37°, N87°W. The rake of the net slip is 37° NW.

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STRUCTURAL AND TECTONIC INTERPRETATIONS

To create an accurate model to describe the types and timing of faulting

associated with the Currant Summit fault, the relationship of the fault to Permian-

Eocene folding and Cenozoic normal faulting must be understood. The relationship of

the fold to Tertiary volcanic rocks and to other faults constrain the age of the fold.

Identification of the age and episodes of extensional faulting aid in understanding the

local and regional extensional stress field. The field and structural data allow

interpretation of the extension associated with the Currant Summit fault and creation

of a structural model for the Currant Summit fault.

The White Pine Range anticline

The sub-Tertiary unconformity indicates that folding in the White Pine Range

anticline occurred prior to local extension and deposition of volcanic rocks. The great

differences in dips between the moderately-dipping Paleozoic strata (30°-60°E) and

the gently-dipping Cenozoic strata (6°-22°E) suggest that the Paleozoic strata were

folded and tilted prior to deposition of the Oligocene volcanic rocks. Folding would

have occurred after deposition of Pennsylvanian units, the youngest Paleozoic rocks

exposed in the study area; Permian units are folded in the northern White Pine Range

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suggesting that folding occurred in the Permian or later (W.J. Taylor, written comm.,

1999).

Pre-volcanic deformation is suggested by a small outcrop in the Horse Range

in which volcanic rocks overlie the Devonian Guilmette Formation along an angular

unconformity (Fig. 4; Plate 1). The nonplanar contact indicates that erosion of tilted

Paleozoic stratigraphy had occurred and that the Horse Range was a topographic high

during deposition of some Tertiary volcanic rocks. Paleorelief is also documented

north of the study area in the White Pine Range, which suggests topographic relief and

erosion prior to emplacement of Oligocene volcanic rocks (Langrock, 1996). The

angular unconformity could be produced by folding or faulting, but faults with the

geometries and kinematics required to produce the pre-volcanic tilts are not observed

in the study area suggesting the paleotopographic highs were created by folding.

Prevolcanic paleorelief is also suggested by the Late Cretaceous-Eocene Sheep

Pass Formation (Fouch et al., 1991; Taylor et al., 1999a). The Sheep Pass Formation

comprises nonmarine landslide, pluvial and lacustrine deposits in isolated high-angle

normal fault bounded basins in east-central Nevada. Deposits of the Sheep Pass

Formation are identified in the Pancake Range and in Railroad Valley (Bortz and

Murray, 1979; Fouch et al., 1991; Perry and Dixon, 1993). The deposits suggest that

localized extension occurred in an intermontane high-relief setting. This is further

evidence for pre-volcanic paleo-relief.

The White Pine Range anticline may have formed during either Mesozoic

contraction or Oligocene or earlier extension. Contraction in the central Nevada thrust

belt took place sometime between the Late Permian-Cretaceous (Taylor et al., 1993;

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Taylor et al., 2000). Many styles of folding associated with extension have also been

recognized in the western U.S. and may have occurred in east-central Nevada during

the Cenozoic (Camilleri, 1992; Faulds and Varga, 1998; Janecke. 1998). Because no

thrusts or low-angle normal faults that may be directly linked to the formation of the

White Pine Range anticline are exposed, the cause of folding must be based on

regional arguments.

A variety of large folds and thrust faults are identified in the central Nevada

thrust belt. Thrusts and folds are well documented in the Worthington Mountains,

Duckwater Hills, and the Grant, Quinn Canyon, Pancake, Horse, and White Pine

ranges (Fig. 2) (Moores et al., 1968; Kleinhampl and Ziony, 1985; Bartley and

Gleason, 1990; Perry and Dixon, 1993; Taylor et al., 1993). The folds are commonly

east- and west-vergent. North-plunging ductile folds and associated reverse faults are

identified in the Grant Range as Mesozoic structures (Lund et al., 1991). An

overturned anticline intruded by a Mesozoic pluton in the Grant Range indicates pre

late Cretaceous deformation south of the study area (Camilleri, 1992; Taylor et al.,

2000). Thrusts in the Grant Range are east-vergent with upright folds in the footwall

(Fryxell, pers. comm., 1999). Similarly, east-vergent thrusts and broad upright

anticlines are exposed in the northern White Pine Range (Hose and Blake, 1976;

Langrock, 1995; W.J. Taylor, unpub. mapping). Like these examples, the White Pine

Range anticline is a broad and upright anticline.

Extension-related folds are also associated with detachment faults and

accommodation zones (Camillerri, 1992; Janecke, 1994; Faulds and Varga, 1998).

Large-scale detachment faults that could be responsible for folding or doming are not

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exposed in the study area although these structures do exist in the central White Pine

Range (Walker et al., 1992; Langrock, 1995) and northern Grant Range (Lund et al.

1991 ; Camilleri, 1992). Progressive low- or high-angle faulting caused doming of the

Grant Range forming a range-sized broad fold (Camilleri, 1992).

Janecke recognized extensional folds above low-angle faults in the northern

Basin and Range province (Janecke, 1998). Cross-cutting relationships that show

contemporaneous fold and fault development as well as growth strata that indicate

deposition during the fold development are distinguishing characteristics of

extensional folding (Janecke, 1998). The White Pine Range anticline does not exhibit

these features although structures and syntectonic sediments may be unidentified, at

depth or covered by recent alluvium.

Anticlines and synclines also occur in accommodation zones and are

associated with extension in parts of the Basin and Range province (e.g., Faulds and

Varga, 1998; Stewart, 1998). Such folds are created by a large number o f normal

faults that accommodate extension and dip towards the hinge surface to produce an

anticline. This fault geometry and continued extension during deposition of sediments

can cause sediment fanning on the limbs of the fold (Faulds and Varga, 1998). Faults

within the study area do not follow a geometry that would create a fold in the

Paleozoic units strictly by faulting (Figs. 8b and 9).

The lack of proper fault geometry, stacked low-angle normal faults, and coeval

fault and fold relationships suggest that the White Pine Range anticline is not an

extensional, but a contractional fold. Large magnitude pre-Oligocene extension is also

required to produce the folding and doming of the strata. Pre-Oligocene extension is

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associated with the Late Cretaceous-Eocene Sheep Pass Formation in the Pancake

Range and Railroad Valley but high-angle faults associated with this formation did not

produce broad folding. A shape similar to the surrounding late Permian to Mesozoic

folds, proximity to Mesozoic thrusts, the angular unconformity with Oligocene

volcanic rocks suggesting a pre-Oligocene age, and the location of the fold within an

area of known late Permian-Cretaceous contraction suggest a contractional origin for

the folding. The White Pine Range anticline is interpreted here as a fold associated

with Central Nevada thrust belt based on the fold geometry, age, and location within

this orogenic belt.

Cenozoic extension

Up to four episodes of extension are documented in the mountain ranges

surrounding the study area (Lumsden, 1964; Kleinhampl and Ziony, 1985; Langrock,

1995). Although only few cross-cutting fault relationships are exposed within the

study area, research in the White Pine, Grant, and Pancake ranges gives insight into

the age of faulting to those faults in the study area. Early low-angle normal faulting

was followed by up to three periods of post-Oligocene faulting in the White Pine

Range and surrounding region (Langrock, 1995). Cross-cutting fault relations within

the study area suggest three episodes of extension north and two episodes south of the

Currant Summit fault, beginning with low-angle faulting.

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Low-angle faults

Low-angle normal faults in the White Pine and Grant ranges caused

denudation of the ranges and may be related to low-angle normal faults exposed in the

study area. The Blackrock fault and Silver Spring detachment, low-angle normal

faults exposed in the White Pine Range, accommodated west-northwest and southwest

extension, respectively (Moores et al., 1968; Langrock, 1995; Taylor et al., 1996).

Relationship to Tertiary rocks and crosscutting relationships suggest the maximum age

for the Blackrock fault is Oligocene. The fault accommodates 7.6 km of west-

northwest extension and places Pennsylvanian and Mississippian units over Cambrian

units (Moores et al., 1968; Walker et al., 1992; Langrock, 1995). The Silver Spring

detachment in the southwestern White Pine Range is —35 Ma or younger based on

crosscutting relationships with an -35 Ma stock (Taylor et al., 1996).

The low-angle normal faults exposed in the White Pine Range may be related

to or generally synchronous with low-angle normal faults in the Grant Range, which

are stacked west- (Fryxell, 1988; Camilleri, 1992) and east-dipping faults (J.E.

Fryxell, pers. comm., 1999). Recent mapping in the Grant Range uncovered a north-

striking low-angle normal fault, the Eureka fault, exposed in Ordovician to Mississippi

strata in the north-central Grant Range (Fig. 3) (J.E. Fryxell, pers. comm., 1999). This

fault strikes north toward the Horse Range but has not been mapped completely.

Low-angle normal faults exposed within the study area may relate to those

identified north and south of the study area. Two low-angle normal faults appear to

exist after the later faults were removed (Fig. 9). A low-angle fault offsets Cambrian

strata on the western edge of the study area and another non-planar fault northwest of

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the Currant stock places upper Devonian units on lower Devonian units and Silurian

Laketown Dolomite and Ordovician Fish Haven Dolomite on lower Ordovician

Eureka Quartzite (Fig. 4; Plate 1). The younger over older offset of east-dipping strata

on the northwest-dipping low-angle fault northwest of the Currant stock suggests

transport direction is generally west and generally similar to the Blackrock fault and

the Silver Spring detachment. The total amount of offset of the low-angle faults on

the western margin of the White Pine Range is difficult to constrain because they are

nearly parallel to bedding. These faults may be similar to the stacked low-angle faults

in the Grant Range, which are also sub-parallel to bedding. The low-angle faults

within the study area have a transport direction similar to faults in the northern White

Pine Range and northwestern Grant Range. The low-angle normal faults in the study

area may be a critical link to low-angle normal faults located to the north and south

because of their location between the low-angle faults and similar transport direction.

Another low-angle normal fault in the western Horse Range is believed to form

the Horse Camp basin southwest of the study area (Fig 3) (Moores et al., 1968;

Brown and Schmitt, 1992; Horton and Schmitt, 1998). The basin is thought to be

bounded by the Currant Summit fault to the north and the Ragged Ridge fault, a 30°

W dipping fault on the east, near the western margin of the Horse Range (Moores et

al., 1968; Horton and Schmitt, 1998). A Miocene camel skull near the base of the

Horse Camp basin sediments, which overlie the Oligocene (26.2 Ma) Shingle Pass

Formation (Taylor et al., 1989), indicate that initial basin formation is Late Oligocene

to Early Miocene in age (Fryxell et al., 1996; Horton and Schmitt, 1998).

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Low-angle normal faults in the study area and surrounding ranges may be

related to the Ragged Ridge fault and the Horse Camp basin. The Ragged Ridge fault,

like the surrounding low-angle faults, caused exhumation of the mountain range and

has a similar transport direction to the Blackrock fault and the Silver Spring

detachment. The age of the basin is early Miocene, and other low-angle faults in the

Grant and White Pine ranges are known to be younger than late Eocene to early

Oligocene, suggesting a similar age is possible. The low-angle normal faults exposed

in the White Pine, Horse and Grant ranges, including the Blackrock fault. Silver

Spring detachment and the Ragged Ridge fault, all cause exhumation of the ranges and

may all be related.

Other options exist to describe the relationship of these low-angle faults to one

another. The Ragged Ridge fault may post-date earlier low-angle faults, now hidden

beneath the Horse Camp basin. Low-angle normal faults in the study area and near

the suspected margins of the Horse Camp basin may be related to movement of the

Ragged Ridge fault, but transport magnitude and timing constraints are required to

make these conclusions. The relationship of the Ragged Ridge fault to the Currant

Summit fault, and the age o f all the low-angle faults must be identified in order to

constrain the relationships among these low-angle normal faults and the Currant

Summit fault.

High-angle normal faults

North- to northwest-striking high-angle normal faults consistently cut

northeast-striking high-angle normal faults, suggesting two periods of high-angle

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faulting. North-striking faults are concentrated near the east-west striking Currant

Summit fault and in the Horse Range where cross-cutting relations are few. Some

north-striking normal faults cut northeast-striking faults in exposures in the volcanic

rocks. This suggests that the north-striking faults are, like the northwest-striking

faults, younger than the northeast-striking faults (Figs. 4 and 11 ; Plate 1 ).

Differences in fault orientation may represent changes in the local stress field

through time (Figs. 4 and 11; Plate 1). Previous research in the Basin and Range

province documents a rotation of the orientation of the regional least principal stress

direction over time firom northeast-southwest in the Miocene to northwest-southeast

d uring late Miocene time (Best, 1988; Zoback, 1989). This is inconsistent with

northeast-striking faults offset by a later stage of north and northwest-striking faults,

therefore the local fault relationships may be caused by a local stress field and not the

regional stress field.

The absolute ages of the high-angle normal fault sets are difficult to constrain.

Both fault sets offset the same strata including the Oligocene volcanic section, and

thus, they are post-Oligocene. Older pre-Oligocene faulting does occur within the

region as indicated by the Eocene Sheep Pass Formation basin fill deposits (Fouch et

al., 1991; Taylor et al., 1999a). However, no pre-Oligocene normal faults are

documented in the study area. No Quaternary high-angle normal faults oriented

perpendicular to the extension direction are mapped within the study area, but east-

west striking faults scarps are documented in the study area. This suggests local

extension is late Oligocene-Holocene in age.

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Kinematic analysis of the Currant Summit fault

By identifying the relationship of the Currant Summit fault to surrounding

structures in the study area, a kinematic model can be created for the fault and

compared to the proposed models of transverse faults; transfer fault, accommodation

zone, overprinted normal fault, and overprinted strike-slip fault (See Chapter 4). Fault

geometries on opposite sides of the transverse fault and their ages relative to the

Currant Summit fault are important for distinguishing among the different models.

Previous analysis by Moores et al. (1968) identified the Currant Summit fault

as an old fault that separates two areas that developed under very different stresses and

that initially formed prior to folding of the Paleozoic units. Interpretation of data from

this research suggests the age of the Currant Summit fault within the study area to be

Tertiary to Quaternary. Paleozoic units folded during Permian-Cretaceous contraction

are the oldest units offset by the transverse fault. If the Currant Summit fault was

active during the Mesozoic, folds north and south of it would have different shapes,

geometries, orientations, or positions across the transverse fault. The similarity of the

folds and dips of Paleozoic units suggest this was not the case.

Offset of Tertiary volcanic units and Quaternary sediments indicate movement

along the Currant Summit fault after ~31 Ma and in the Quaternary (Fig. 4; Plate 1).

Degraded fault scarps in Quaternary alluvium indicate that faulting continued into or

reoccurred in at least the Quaternary. Some motion must predate the scarps to account

for the total net slip along the Currant Summit fault. Five historic small magnitude

earthquakes are also documented along the Currant Summit fault (Dohrenwend et al.,

1991; dePolo and dePolo, 1998)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36

The Currant Summit fault does not fit entirely into one of the existing models

of transverse faults: accommodation zone, transfer zone, late strike-slip fault, and late

normal fault. The Currant Summit fault within the study area is a normal left oblique-

slip fault that acts as a barrier to fault propagation and accommodates different

amounts of extension on opposite sides. Extensional normal faults on opposite sides

of the fault do not propagate beyond the barrier fault, but transfer at least a portion of

extensional strain onto the transverse fault. Motion along this transverse fault is

predominately strike slip. The Currant Summit fault also allows some north-south

extension, which is recognized in other areas of the Basin and Range province.

The Currant Summit fault is not simply a strike-slip or young normal fault that

formed late in the Cenozoic extension and offset older faults. The lack of matching

faults across the fault and the net slip eliminate the overprinted strike-slip fault and

overprinted normal fault models for the Currant Sununit fault. In addition, the 3000 m

of throw required along a normal fault to match the unit outcrop patterns would

probably have created different associated structures, such as steeper hangingwall

dips, east-west strikes in beds, and deep basins.

The Currant Summit fault does not fit into the end-member accommodation

zone models as classified by Faulds and Varga (1998) because these structures tend to

have overlapping zones of normal faults accommodating extension (Fig. 8a). The

accommodation zones tend to form fault formed synclines or anticlines not present in

the study area (Rosendahl, 1987; Faulds and Varga, 1998). The Currant Summit fault

is a discrete fault zone, which is unlike most of the accommodation zone models

(Morley et al., 1990; Faulds and Varga, 1998).

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The Currant Sununit fault is similar to the synthetic sinistral transfer zone fault

of Faulds and Varga (1998) (Fig. 8b). In the transfer fault models, strain from

associated normal faults is transferred onto the transfer fault to acconunodate

extension in two separate regions (Gibbs, 1984; Faulds and Varga, 1998). Normal

faults north of the Currant Summit fault appear to transfer strain onto the fault, but

complete expression of this strain is not present south of the Currant Sununit fault

within the study area because of the large differences in extension across the Currant

Siunmit fault. It is possible that faults outside the study area accommodate the transfer

of the unaccoimted for strain.

The Currant Summit fault does not exhibit the characteristics of the antithetic

acconunodation zone of Faulds and Varga (1998) and the strike-slip accommodation

zone of Rosendahl (1987). The transverse fault can be a discrete fault zone with

opposing normal faults but most models have the linking fault oblique to the extension

direction (Faulds and Varga, 1998). Overlapping or interfingering normal faults

would be more typical of an accommodation zone model (Rosendahl, 1987; Faulds

and Varga, 1998) rather than the abrupt termination of high-angle faults as seen in the

study area and along other locally oblique-slip faults in the Basin and Range province.

Because the fault does not clearly fit into one of these two definitions for

faults, a new model is required. Therefore, I propose the name oblique-slip barrier

transfer fault for a transverse fault model in which the fault acts as a barrier to fault

propagation, allows different amounts of extension on either side of the fault, and has

oblique-slip with a large component of strike-slip (Fig. 13).

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Relationship of Currant Summit fault to Regional Structures

Pritchards Station Lineament

The Currant Summit fault appears to continue west of the study area into

Railroad Valley. North-south striking seismic lines in the valley are poor and do not

show conclusively an east-west striking fault along strike from exposures of the fault

(D.E. French, pers. com., 1999). However, bouguer gravity anomaly maps identify a

gravity high dividing two sub-basins in Railroad Valley along the same latitude as the

Currant Summit fault (Snyder et al., 1984; Saltus, 1988). This divide may be created

by the Currant Summit fault.

Previous research in the Horse Camp Basin, to the southwest of the study area,

suggests that the Ragged Ridge fault joins the Currant Summit fault west of the study

area (Fig. 3) (Moores et al., 1968; Horton and Schmitt, 1998). The west-directed slip

on the Ragged Ridge fault would add a right-lateral oblique component of slip to the

Currant Summit fault in the early Miocene. This suggests that the sense of strike-slip

motion or composite net-slip along the Currant Summit fault changes to the west.

Horton and Schmitt (1998) also found landslide blocks from the northwest in the

Horse Camp Formation suggesting that the White Pine Range was a topographic high

during the Miocene. The intersection of the Currant Summit fault with the Ragged

Ridge fault is obscured by alluvium and any interpretation of how they interact is only

speculative.

When adjacent regions separated by a transverse fault undergo different

amounts of extension, changes in the sense of strike slip can occur (Fig. 8b) (Gibbs,

1984; Faulds and Varga, 1998). The amount of slip on the Currant Summit fault may

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change to the west of the study area as slip is transferred onto it from different faults

on the north and south, however the sense of slip on the Ragged Ridge fault is not

enough to completely erase the left-lateral slip record. Horton and Schmitt (1998)

report 1600 m of exhumation in the Horse Camp basin and this research reports 2700

m of left lateral slip along the Currant Summit fault. This relationship could also

indicate that normal left oblique-slip along the Currant Summit fault occurred between

the Oligocene and early Miocene and was followed by normal right-oblique slip along

the western part of the fault after the Miocene. However, the opposite could be true or

the faults could be coeval. More research must be completed near the proposed

intersection of the faults before this relationship can be deciphered.

The Pritchards Station Lineament continues westward from the Currant

Summit fault across Railroad Valley and into the Pancake Range at —38° 45’ (Fig. 2).

No major east-west striking structures are mapped at this latitude in the Pancake

Range but the Pritchards Station Lineament does appear to separate Paleozoic strata

on the south from Tertiary units on the north (Ekren et al., 1976). Dixon et al. (1972)

and Ekren et al. (1976) did extensive studies in the Hot Creek Valley area on the

western Pritchards Station Lineament and found east-west striking left-lateral faults

and zones of breccia. Similarly, 2 km of left-lateral displacement are documented in

the Shoshone Mountains along an east-striking fault (Fig. 1) (Ferguson and Muller,

1949; Ekren et al., 1976). This suggests that left-lateral slip may be present along

much of the Pritchards Station Lineament.

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The lineament also bounds the margins of four calderas and is associated with

several mining districts (Rowley, 1998). The possibility of strike-slip along the

caldera margins is undocumented.

Oblique-slip faults

Other oblique-slip faults that strike normal to the majority of structures in a

region crop out elsewhere in Nevada. The Penoyer Spring fault zone and the Crystal

Wash fault zone are oblique-slip transverse faults and part of the east-west trending

Timpahute lineament in east-central Nevada (Figs. 1 and 2) (Taylor et al., 1999b).

The Penoyer Spring fault zone separates an extended area to the north from an area of

little to no extension to the south of the fault (Taylor et al., 1999b). Based on offset

piercing points, this fault originally formed as a north-dipping high-angle normal fault

and later the western portion of the fault was a transfer fault associated with

movement on normal faults to the north (Taylor et al., 1999b). This fault, like the

Currant Summit fault, may have slip transferred onto it from related normal faults

because the amount of extension to the north is equal to the strike component of slip

on the western end. Net slip in the western portion of the Penoyer Spring fault is then

oblique. The fault acts as a barrier to fault propagation because no normal faults are

exposed to the south.

The Crystal Wash fault, east of the Penoyer Spring fault zone, has a similar

history. The fault dips steeply to the north and rakes of slickenlines are 32°-54° W

indicating that the last movement on the fault is oblique slip (Fig. 2) (Switzer, 1996;

Taylor et al., 1999b). This fault zone along the Blue Ribbon lineament, like the

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Currant Summit fault, acts as a barrier to fault propagation because no exposed

Tertiary faults cut the transverse fault and it accommodates differently striking faults

north and south of the Crystal Wash fault zone.

Oblique-slip faulting has also been recognized on portions of the Blue Ribbon

Lineament in east-central Nevada (Overtoom and Bartley, 1996). Research on a

portion of this lineament in the Golden Gate Range revealed a total of 360-860 m of

right lateral slip across three east-west striking faults and 4030 m of dip separation.

This fault zone was active during Tertiary volcanism and accommodates a large

component of north-south extension probably related to this magmatism (Overtoom

and Bartley, 1996).

The steeply dipping transverse oblique-slip faults are common and important

parts of extended terranes. They act as barriers to fault propagation, strike parallel to

subparallel the extension direction, and remain active throughout much of the

extensional history in the Basin and Range province.

Transverse faults in extended regions

Locally, the net slip on many transverse faults in the Basin and Range province

is oblique-slip, but regionally each fault may be a part of a larger transfer zone or

accommodation zone. Transfer faults or accommodation zones are structures

currently recognized in parts of highly extended regions. Many components of slip

are present along different parts of the transfer faults or accommodation zones,

including normal slip, strike-slip, and oblique-slip. The locally oblique-slip Currant

Summit fault, Penoyer Spring fault zone, and Crystal Wash fault are parts of larger

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lineaments, which may have normal or strike-slip faulting in other locations along the

lineament. The lineaments and associated faults may be accommodation zones or

transfer zones. The structures link opposing normal faults, allow for linkage of normal

faults and accommodate extension at terminations of synchronously extended areas

(e.g., Gibbs, 1984; Rosendahl, 1987; Morley; 1990; Faulds and Varga, 1998;

Thenhaus and Bamhard, 1998).

Transfer faults are recognized in many extensional provinces including the

North Sea (Gibbs, 1984), Gulf of Suez (McClay and Khalil, 1998; Faulds and Varga,

1998), and the Basin and Range province (e.g., Faulds and Varga, 1998). In transfer

fault models, normal faults typically terminate abruptly and transfer slip onto the

transverse structure, similar to the geometries and kinematics seen along the Currant

Summit fault. Therefore, the barrier transfer fault model may be used for transverse

faults in many extended regions. Research in the Gulf of Suez shows left-lateral

oblique-slip faults striking subparallel to the extension direction that link domino-styie

normal faults (McClay and Khalil, 1998). These faults are documented as transfer

faults but more research may reveal that they are, specifically, barrier transfer faults.

Complex detachment fault geometries and transfer faults are identified in the

highly extended North Sea region (Gibbs, 1984). Transfer faults may be oblique-slip

faults parallel or oblique to the extension direction that allow ‘leakage’ of slip between

two regions of extension with different slip rates (Gibbs, 1984). These relations are

similar to the kinematics and geometries found in the study area and suggest a similar

role for the Currant Summit fault.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Accommodation zones have been well studied in rift systems, especially the

East Africa rift system and the Colorado River extensional corridor of the southern

Basin and Range province (Fig. 1) (e.g., Rosendahl, 1987; Morley et al., 1990; Faulds

and Varga, 1990; Faulds and Varga, 1998). Two types of transverse accommodation

zones are recognized in the Basin and Range province: broad anticlinal and synclinal

accommodation zones and transverse antithetic accommodation zones (Fig. 8a). The

anticlinal and synclinal structures identified in the Basin and Range province separate

opposing tilt domains and may continue across ranges and basins. The folds trend

generally north-south and are offset by east-west trending transverse zones (Stewart,

1980; Faulds and Varga, 1998). The antithetic transverse accommodation zones may

have different quantities of faults across the zone, and different patterns and tilts of

beds (Faulds and Varga, 1998). Faults may overlap and produce synclinal or anticlinal

structures (Faulds and Varga, 1998).

The locally oblique-slip faults of the Basin and Range province appear to have

components of both transfer fault zones and accommodation zones based on similar

relationships to normal faults, large strike-slip components, and faults transferring slip

onto the transverse fault zone. The oblique-slip faults act as barriers to multiple

episodes of extension and are oriented perpendicular to the direction of extension (Fig.

13b). The locally oblique-slip faults may represent isolated portions of a transfer fault

or accommodation zone in a highly extended terrane or may be a combination of the

two (Fig. 13b).

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Implications

The implications of the oblique-slip barrier transfer fault model in extensional

tectonics are that such a transverse fault: (1) segments extensional provinces; (2) may

be part of a larger transfer or accommodation zone; (3) acts as barrier to fault

propagation; and (4) allows the transfer of slip from normal faults onto it.

The barrier transfer faults are required for segmentation and asymmetry of

extensional systems. These structures are created at the termination of systems of

normal faults and allow for changes in the amount of extension across an extended

region. As barriers to fault propagation, the barrier transfer fault becomes an

important structure for transferring strain across the extensional system and allowing

for a change in the location of extension.

The oblique-slip barrier transfer fault and other faults oriented perpendicular to

the direction of extension also have an applied significance. The faults may be

pathways for the migration of hydrocarbons, groundwater, and hydrothermal fluids.

They may also create structural or stratigraphie traps for hydrocarbons. As in the

study area, the barrier transfer fault may be associated with intrusions or volcanic

centers. Oblique-slip barrier transfer faults may be parts of larger transverse faults,

but they stand alone as important structures in the understanding of local strain

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTERS

SUMMARY AND CONCLUSION

Detailed geologic mapping of the Paleozoic and Cenozoic rocks and Mesozoic

and Cenozoic structures that deform them allowed determination of the magnitude of

fault offset and number of episodes of faulting on the Currant Summit fault and

associated normal faults in the White Pine and Horse ranges. Field analysis and three-

point problems document that the fault is steeply dipping and does not change from a

low- to a high-angle fault along strike, as identified in previous research (Moores et

al., 1968). The hingeline of the offset White Pine Range anticline was used to

determine a net slip of 3300 m at 35°, N87°W.

Previously undifferentiated Tertiary volcanic rocks were identified in this

study. An age of 31.26+0.04 Ma was found for a rhyolitic tuff in the volcanic rock

sequence. The age and petrography of the unit suggests that it is the Windous Butte

Formation.

The name White Pine Range anticline was expanded to include the fold

identified south of the Currant Summit fault. The angular unconformity with the

overlying Cenozoic volcanic rocks, the lack of Cenozoic normal fault geometries

capable of producing extensional folds, and the location within an area of known

thrust faulting and folding, suggests the fold is related to Late Permian-Eocene Central

Nevada thrust belt.

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The folded Paleozoic rocks and the overlying Cenozoic rocks are extended by

high- and low-angle normal faults. Low-angle normal faulting was followed by > two

periods of high-angle faulting. A greater number of normal faults with a greater

amount of extension were identified north of the Currant Summit fault than south.

North-northwest striking normal faults consistently offset the northeast striking normal

faults suggesting a rotation of the stress field through time.

The relationship of the Currant Summit fault to the anticline, strata, and normal

faults allowed creation of a kinematic model, the oblique-slip barrier transfer fault, for

the Currant Summit fault. Northwest-northeast striking normal faults are exposed

north and south of the Currant Summit fault, but a greater number of faults

accommodate a greater amount of extension north of the Currant Summit fault. The

normal faults are not offset by the Currant Summit fault but appear to terminate at and

transfer strain onto the east-west structure. The Currant Summit fault does not fit

completely into one of the previously published models of transverse faults. This type

of fault has a large oblique-slip component orthogonal to the regional extension

direction and acts as a barrier to fault propagation.

This type of fault is identified in other areas of the Basin and Range province

suggesting oblique-slip barrier transfer faults are common and important structures in

the Basin and Range province and in other extensional systems. A barrier transfer

fault allows for segmentation and asymmetry in extended terranes.

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120°W 114°W

NV ’ritchards Statton Lineament 39°N SM CSF UT

Timpahute Lineament Colorado Plateau CA

200 km AZ

Figure 1. Map of lineaments identified in the central Basin and Range Province. The Currant Summit Fault (CSF) is the eastern limit of the Pritchards Station Lineament (Ekren et al. 1976). The approximate extent of the northern Colorado River extensional corridor is indicated by the gray dashed lines. Shoshone Mountains (SM) are the western limit of the Pritchards Station Lineament The Penoyer Spring and Crystal Wash fault zones are within the western Timpahute Lineament Lineaments from Duebendorfer and Black (1992) and Ekren et al. (1976).

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116"W 115“W

39°N

RRVF Pntcnards Siatkm vLineament While Grant

Railroad

North f:l A-ise. - 3 8 “N Pahroc ‘

Timpahute ^ g e

Figure 2. Regional location map identifying the ranges (daik color) and basins (white). Area of study (light gray area). Central Nevada Caldera Complex (gray dashed line), Pritchards Station lineament (black dashed line), the Black Rock fault (BR and double hatched line). Silver Spring detachment (SS and double hatched line), Penoyer Spring fault (PSF and solid black line). Crystal Wash fault zone (CWFZ and solid black line). Hot Creek Valley (HCV), Worthington Mountains (WM), Duckwater Hills (DH), Railroad Valley fault (RRVF), and the Currant Summit fault (black solid line) are identified. Figure modified from Taylor et al. (1993).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD Q.O C g Q.

■D CD 115 '10' I IS" 15' C/) C/) J White Pine Range (QTI study Area ■D8 V Anticline 1 3. 3" CD «1» ■DCD O Q. C I a 3O "O iorsc Camp o Basin

Q.CD ( Horse Range

38--15' ■D 2 Miles CD Figure 3. Simplified geologic map identifying major structures and stratigraphy in the southern White Pine Range and C/) C/) northern Horse Range. 1 he light gray line outlines the study area. UndilTerentiated Paleozoic units (Pzu and stippled pattern), undifferentiated Tertiary volcanic and intrusive units (Tu), Eocene to Miocene Horse Camp basin deposits (horizontal lines), and Tertiary to Quaternary alluvium (QTf and white), are the major stratigraphie units. Major faults and folds within the study area and in the surrounding ranges are shown, including the Silver Spring detachment (SSD), White Pine Range Anticline (WPR Anticline), Ragged Ridge fault (RRF), Currant Summit fault (CSF), and the Eureka fault (EF). (Information outside the study area from Moores el al., 1968; Taylor et a l, 1996, Horton and Schmitt, 1998, J E Fryxell, pers. com , 1999.) ;d ■DCD O Q. C 8 Q.

■D CD

C/) C/)

"O8

(O'

I SC

3. : 3" CD ■DCD O Q. C Mu? Oa 3 ■D •y O

Q.CD

■D CD (/) (/) 2 kiloinclcrs

I M iles

Scale l:38.0(K)

Figure 4a. Simplified geologic map of the western portion of the study area. Refer to Figure 4c for unit and symbol information. Refer to Plate I for detailed geologic map

73 CD

C/) C/)

738

3. 3 " CD

CD 73 O Q. C QT, a O 3 73 O

CD Q.

73 CD

C/) C/) KiloiiKtcrs

Figure 4b. Simplified geologic map of the eastern portion of the study area. Refer to Figure 4c for unit and symbol information. Refer to Plate I for detailed geologic map 52

k q l Cenozoic Paleozoic Quatematy Pennsylvanian Qa : Active alluvium We Ely Limestone Qc Colluvium Mississippi Undiflerentiated (Joana Ql Lacustrine deposits Mu Limestone. Chainman Shale, and Diamond Peak Fm.) Qua Old alluvium Devonian Guiimette Fortnation QTf Old fan deposits Tertiary (Inset units strat. position uncertain) Simotison Doloitiite Tu Volcanogenic scd. unit Dse Sew Dolomite

J Jasperoid Silurian Ta Ash fall SI Laketown Dolomite

Tb Basalt flow Ordovician 1 Geo Eureka Quartzite and I Windous Butte Fish Haven Dolomite O b Antelope Valley Ls. Tv Unnamed rhyolitic tuffs Tps Ogn Goodwin and Ninemile fms. Tuff of Pritchards Station Tc Cambrian Currant Tuff Windfall Formation White Pine Range rhyolite Lincoln Peak Fm. and Dunderberg Shale Tsc Stone Cabin Formation Pole Canyon Limestone intrusion (dike'sill) Cl Lower Cambrian units < : Currant Stock Symbols and Contacts Strike and dip of bedding Strike and dip of compaction foliation V Stratigraphie contact. Dashed where approximately located and dotted where concealed under alluvium. Faults dashed where approximately located and dotted where concealed under alluvium. Ball and bar are on the hangingwall. Low-angle normal faults. Double hatch mark on hangingwall. Oblique-slip fault. Bar and ball on the hangingwall. Arrows point in direction of slip. Tie line. Used to identiW areas with the same formation name. Anticline. Positioned on the trace of the axial surface. Svncline. Positioned on the trace of the axial surface.

Figure 4c. Unit key for simplified geologic map (Figure 4a and 4b). Refer to Plate 1 for detailed geologic map and unit key.

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R ock type T h ick n cs(m and wcalhcr* WPR HR ing profile Fonmadon Ely Limestone - gray limestone with chert and fossils Diamond Peak Formation - orange to brown sandstone

Chainm an Shale - gray to black fissile shale and thinly bedded brown iw tires is tant sandstone ledges

I Limestone - light gray crinoid-iicb limestone

Guihnetae Formation - brown to gray limestone and dolomite ledges and thinly bedded argillaceous layers

Simonson Dolondle - gray to brown medium bedded ______limestone ______Sevy Dolomite - light gray to white blocky ______weathering dolomite ______Laketown Dolomite - coaise-grained massive dolomite

Fish Haven Dolomite - dark gray to black massive dolomite

\ Eureka Quartzite - white to pink sandstone ______Antelope Valley Limestone - gray limestone and thinly bedded yellow shale: fossils are Receptaculites Ninemile Formation - predominantly tan to yellow calcareous shale with gray limestone ledges

Goodwin Limestone - blue-gray limestone with chert ______Windfall Formation - thick-bedded gray limestone with thinly bedded limestone at base

Dunderberg Shale - thinly bedded limestone and shale

Lincoln Peak Formation - thinly bedded limestone and tan to orange shale; some small trilobites arc exnosed ______/ Pole Canyon Limestone - thinly bedded limestone, shale ^ I —I and a massive white limestone Pioche Shale - khaki green to black phyllitic shale ______and dark gray limestone; fossils are Girvanella Prospect Mountain Quartdte - thinly bedded sandstone Figure S. Paleozoic stratigraphie column of all units exposed in the White Pine and Horse ranges. Thicknesses of beds for the White Pine Range (WPR) and the Horse Range (HR) determined in the field and compiled from Moores et al., (1968), Lumsden (1964), and Kleinhampl and Ziony (1985). Standard geologic symbols are used.

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Basalt (Tb)- thin basalt unit 2000 Windous Butte Formation (31.3+0.04 Ma) (Twb)- salmon to brown quartz and sanidine-rich unit 500 Unnamed rhyolitic tuff (Tv2) Xlmt^ed ash-flows tuff (Tvl)- red to brown welded tuff S^ f f of Pritchards Station (Tps)- quartz-rich rhyolitic tuff

Currant Tuff (Tc)- white to tan rhyolitic tuff and 1000 ' — V V V sedimentary units

250 m White Pine Range rhyolite (Tr)- plagioclase-rich rhyolite and andésite flows

Stone Cabin Formation (35.34+0.07 Ma, Radke, 1992) (Tsc)- densely welded daric colored phenocryst- rich rhyolitic tuff V V VV

Currant stock (Tes)- highly altered shallow intrusion with large plagioclase phenocrysts; intrudes Mississippian Chainman Shale (Me).

Figure. 6. Generalized stratigraphie section of Tertiary rocks exposed in the study area. Approximate unit thicknesses are given. See Appendix A for complete descriptions and ages of units.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55

114'

NV CNTB UT

I ; Sevier I • -Orogenic • • Basin I ' -0^14 Area • and ! Range ; province

- 37'

Figure 7. Location map of major contractional and extensional belts in the region of interest. CNTB = Central Nevada thrust belt. Teeth are on the upper plate of thrust faults. Shaded area = Basin and Range province. Approximate location of the study area is also indicated. Figure modified from Taylor et al. (1993).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56

a. Synclinal A.Z. Anticlinal A.Z.

Transverse A.Z.

b. Transfer fault zone

Figure 8. Four common end-member models for transverse faults, a. Possible accommodation zones indicating associated anticlines and synclines. b. Synthetic transfer fault c. Young normal fault offsetting older normal faults, d. Young strike-slip fault offsetting older normal faults. Accommodation zones and transfer fault zone modified from Faulds and Varga (1998).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57

Figure 8c.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 ■DCD O Q. C g Q.

■D CD

F a i C/) West T v 2 r v 2 C/) A C -C ^ Twb Tr A' m) Qa

■D8

(O' \ D si

pQu(?) Cjm €pi eip a. Present-day cross section north of the Currant Summit fault. 3"3. CD Tv 2 ■DCD Tvl\Twb Tv2 Twh O Q. Tvl Tv2, C a O3 "O O

CD Q.

■D CD

(/)

pCu(?) b. Retrodeformed cross section A-A', north of the Currant Summit fault. Restored to pre-extensional state (-Miocene). Movement in and out of the cross section not restored. The Currant stock may or not be present at time of deformation. Figure 9. Present day (a) and restored (b) cross section A-A', south of the Currant Summit fault. The location of the cross section line is shown of Figure 4. The restored cross section has been rotated 9° west to remove the tilt of the vol canic rocks. Refer to Figure 4c for geologic units and Plate 2 for detailed cross sections. 00 7) ■DCD Û.O C 8 Q.

■D CD

C/) C/) Tc IPe QTf Cw Ta 8

Oa on, 3 CD Cpcu

3-C C. Present-day cross section B-B', south of the Currant Summit fault.

■oCD O CQ. g Mj Md o 3 ■o D-D* o c-c* Cw Og

co Cpi Cpc Cpcu

C/) o' 3 d. Retrodeformed cross section B-B', south of the Currant Summit fault. Restored to pre-extensional state (-Miocene). Movement in and out of the plane of the cross section not restored.

Figure 9. Present day (c) and restored (d) cross section B-B', south of the Currant Summit fault. The location of the cross section line is shown of Figure 4. The restored cross section has been rotated 9 west to remove tilt of the volcanic rocks. See Figure 4c for stratigraphy unit key and Plate 3 for unit key and detailed cross sections.. 60

On Cw Cw Qb /<3p

Present-day cross section C-C'.

Souh North B-B A-A'

8000 - QTf % - QTf 6000

4000 Dsi

f. Present-day cross section D-D'.

North A-A' E TcTpsTvl

g. Present-day cross section E-E'.

Figure 9 continued. Present day cross sections (e) C-C', (£) D-D', and (g) E- E'. Locations of cross section lines are shown on Fig. 4. The cross sections are not retrodeformable because of movement in and out of the plane of the cross section. Refer to Figure 4c for geologic units and Plate 4 for detailed cross sections.

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Equal Area axial surface a.

N = 43 best fit fold axis

axial surface

b. Equal Area

best fit , fold axis N = 42

Figure 10a. Lower hemisphere stereoplot showing poles to Paleozoic bedding planes north of the Currant Summit fault. The axial surface strikes and dips N 9°E, 83°W with a plunge and trend of 1° S 8®W. b. Lower hemisphere stereoplot showing poles to Paleozoic bedding planes south of the Currant Summit fault. The axial surface strikes and dips N 11°E, 74° W with a plunge and trend of 5° S 11° W. Cenozoic tilting was not removed because Tertiary volcanic rocks have similar dips in both areas.

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N N

N=22 N=12

N N

N = ll N=22

Figure 11. Stereoplots of poles to present attitudes of faults north (a-c) and south (d) of the Currant Summit fault, a. N-S and NW-SE striking faults; b. NE-SW striking faults; c. Low-angle faults north of the Currant Summit fault; d. Faults south of the Currant Summit fault.

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N=25

Figure 12. Stereoplot of poles to fracture surfaces in jasperoid along the central portion of the Currant Summit fault Surfaces do not identify a single east-west striking fault but may show multiple faulting episodes, conjugate fault sets or rhombohedral fault sets.

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Figure 13a. Best fit model for the Currant Summit fault, a left oblique-slip barrier transfer fault b. A general view of an oblique-slip barrier transfer fault showing multiple p erils and styles of faulting. The transverse fault is present during all periods of faulting.

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STRATIGRAPHIC DESCRIPTIONS

Cambrian to Permian and Tertiary to Quaternary units are exposed in the White

Pine and Horse ranges (e.g., Humphrey, I960; Moores et al., 1968; Tracy, 1980;

Gurrerro, 1983; Kleinhampl and Ziony, 1985; Langrock, 1995). Hague (1883), and

Nolan and others (1956) defined Paleozoic stratigraphie units correlative to those in the

White Pine Range in the Eureka District. Paleozoic stratigraphy described by Kellogg

( 1963) in the Egan Range, east of the White Pine Range, also correlates to the units in

the study area (Fig. 4). Formations and units used in the study area are compiled in

Figures 5 and 6.

Paleozoic Stratigraphy

Cambrian System

Prospect Mountain Quartzite (€pm)

The Prospect Mountain Quartzite is a brown to tan ledge-forming quartzite in

the central portion of the study area. The unit is fine to medium grained and cross

bedding is visible in the middle of the outcrop. The outcrop is less than 7 m (20 feet)

high and the base of the unit is not exposed. The upper contact is placed at the top of

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the quartzite and below the dark shales of the Pioche Shale. Drewes and Palmer ( 1952)

first described this Lower Cambrian unit.

Pioche Shale (€pi)

The Pioche Shale comprises khaki green to brown micaceous shales, fine

grained sandstones, and fossiliferous black limestones. The shales are platy and less

resistant than the I — 2 m thick ledges of limestone. Large Girvanella are present in the

limestones and are 2 — 20 mm in diameter. The unit is approximately 91 m (300 feet)

thick. The upper contact was placed below a prominent and resistant 8 m thick ledge of

dark gray limestone. The unit is described by Drewes and Palmer (1957) in the Snake

Range and Kellogg (1963) in the Egan Range.

Pole Canyon Limestone (€pc)

The Pole Canyon Limestone is a varied unit above the Pioche Shale. It is

exposed in the west-central portion of the study area along and north of Highway 6.

The unit was divided into five members in the Snake Range, White Pine County by

Drewes and Palmer (1957). Two subdivisions of the Pole Canyon Limestone were used

for this study.

Lower Unit (€pcl)

The lower member of the Pole Canyon Limestone consists of moderately

bedded limestone (2 — 20 cm) intercalated with sandstone, calcareous shale, and shale

slope layers (1-20 m). Limestone ledges 1-4 m thick are exposed between soil covered

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This reproduction is the best copy available

UMI

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ledgy limestone 80 m thick. Stromatotoporoids were present in the limestone unit of

the White Pine Range. Previous interpretation by Lumsden (1964) suggested that the

limestone is a localized reef or bioherm. The location of the limestone below Cambrian

Dunderberg Shale and the Windfall Formation, as well as the lack of faults, suggests

that unit is the Lincoln Peak Formation. More research on the stratigraphy of the Lower

Cambrian is required. The limestone unit is not identified or described in the

surrounding ranges and is called the Lincoln Peak Formation for this research.

Dunderberg Shale (Ed)

The Dunderberg Shale consists of a light gray thin-bedded limestone and brown

to orange shale. The lithology varies in the study area and previous mapping combined

the Dunderberg with the Lincoln Peak Formation (Lumsden, 1964). The unit is 368 m

( 1200 feet) thick in the Horse Range and at least 274 m (900 feet) thick in the White

Pine Range. Exposures of the Dunderberg in the southwestern White Pine Range

consist of phyllitic fissile shale (1-10 cm thick) and dark-gray limestone ledges 1-5 m

thick near the top of the section. The limestone ledges become thicker near the top of

the unit. The Dunderberg Shale mapped in the northwestern Horse Range consists of

dark brown to orange metamorphosed shales with steppy limestone ledges less than 5 m

thick near the upper contact. In the White Pine Range, the Dunderberg Shale consists

of steppy limestone cliffs 5-10 m thick with shaley partings decreasing near the upper

contact with the Windfall Formation. The upper contact in both ranges is placed at the

base of the Windfall limestone cliffs. Nolan et al. (1956) first described the unit in the

Eureka Mining District, 90 km northwest of the study area.

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Windfall Formation (6w)

The Windfall Formation, named by Nolan et al. (1956), is a thin- to thick-

bedded massive cliff former exposed in both the White Pine and Horse ranges. The unit

was mapped as 270 m (885 feet) thick in the Horse Range and 883 m (2900 feet) thick

in the White Pine Range (Lumsden, 1964). The base of the unit is thin-bedded

limestone (5-10 cm) with thin shaly partings. The middle section is medium-gray

weathering limestone with abundant bedding parallel chert below a dark-gray thin-

bedded mottled dolomite. The Upper Windfall Formation is a medium gray to blue-

gray colored medium to thinly bedded limestone that continues upward into the

Ordovician system. The upper contact is a gradational contact but was placed at the top

of a light gray limestone with intermittent chert below the shaley slopes of the Lower

Ordovician Pogonip Group. Within the study area the top of the unit only crops out

south of the Currant Summit fault.

Ordovician System

Pogonip Group

The Pogonip Group was named by King (1878) for rocks identified and

described in the northern White Pine Range. Hintze (1952) recognized five subunits of

the Group in Blackrock Canyon of the White Pine Range (20 km north of the study

area), but Lumsden (1964) states that the five subdivisions are not as easily recognized

in other parts of the range. Three formations within the Pogonip Group have been used

in Eureka and Nye counties although previous mapping combined the units in the

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southern White Pine Range because of complex structural problems (Moores et al.,

1968). The three subdivisions used in the study area are the Goodwin Limestone,

Ninemile Formation, and the Antelope Valley Limestone.

Goodwin Limestone (Og)

The Goodwin Limestone is a massive light-blue to gray limestone that lies

conformably above the Cambrian Windfall Formation. The basal contact with the

Windfall Formation is gradational and can be difficult to recognize. The steppy cliffs of

the Goodwin Limestone contain some bedding-parallel black to white chert one to six

cm thick. Fresh surfaces are darker gray than weathered surfaces. The limestone is fine

to medium grained. Clastic carbonates and fossil-fragment rich beds are common. The

total thickness is 113 m (370 feet) in the White Pine Range and 58 m (190 feet) in the

Horse Range. The upper contact is placed at the first occurrence of the yellow to

orange shale beds of the Ninemile Formation.

Ninemile Formation (On)

Tan-yellow to orange and brown slopes of shale alternating with ledges of

limestone one-five meters thick are distinctive of the Ninemile Formation. The

limestone ledges are thinly bedded (1 to 30 cm thick) and weathered surfaces are dark

gray in color with rare globular chert and rare Receptaculities. Four to seven limestone

ledges occur in the unit with the distance between the ledges decreasing near the top of

the formation. The total thickness of the unit is 466 m (1532 feet) in the Horse Range

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and 347 m (1134 feet) thick in the White Pine Range. The upper contact is placed at the

top of a yellow-shale slope below a 12 to 24 m (40 to 80 feet) thick limestone ledge.

Antelope Valley Limestone (Oa)

Thick-bedded limestone cliffs of the Antelope Valley Limestone crop out above

the yellow slopes and gray ledges of the Ninemile Formation. The unit is 380 m ( 1242

feet) thick in the White Pine Range and 490 ra (1610 feet) thick in the Horse Range.

The basal medium-gray weathering cliffs are highly fossiliferous. Above the basal cliff

is a section with a rock type similar to the Ninemile Formation that contains abundant

Receptaculites. The blue-gray limestone ledges are 1-3 m thick with some thin (1-20

mm) silty mottled layering. Near the top of the Formation is a second 12-24 m (40 - 80

feet) cliff similar to the basal cliff. The upper contact is above a yellow to tan shale. A

light pink to white silica cemented sandstone lies above the contact.

Emeka Quartzite (Oe)

The Eureka Quartzite is a white to pink and brown resistant cliff former above

the Pogonip Group. The unit has been mapped as approximately 122 m (400 feet) thick

in both the White Pine and Horse ranges (Moores et al., 1968), although in the study

area the imit is always faulted so a true thickness is not known. The unit is a fine

grained and well-sorted silica cemented quartzite, easily distinguished from the

limestones above and below the unit. The unit has been studied by many researchers

including Hintze (1951) and Merriam (1963).

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Fishhaven Dolomite (Ofh)

The dark-gray and black- to brown-weathering cliff former above the Eureka

Quartzite is the Fishhaven Dolomite. Previous research reported that the unit is 128 m

(420 feet) thick in the White Pine Range and 235 m (770 feet) thick in the Horse Range.

It is faulted in both ranges and consists of coarse-grained dolomite and limestone

(Lumsden, 1964). Fresh surfaces may have calcite and pink staining along fractures.

Small white-weathering corals and limestone breccias are common throughout the unit.

Bedding is commonly obscure but thin areas of laminated bedding with alternating

dark-gray and white beds less than 10 cm thick occur throughout the unit. The upper

Fishhaven Dolomite is a dark-gray coarse-grained dolomite below a dark-brown

limestone of the Silurian Laketown Dolomite. A 1 m wide break in the slope was

recognized at the contact in the southern White Pine Range. The imit was first

described by Richardson (1913) in Idaho. The Fishhaven Dolomite correlative in the

Pioche District is the Ely Springs Dolomite (Westgate and Knopf, 1932).

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Silurian System

Laketown Dolomite (SI)

The Laketown Dolomite is a coarse to fine-grained poorly bedded massive

dolomite. The weathered surfaces are dark brown, dark gray to light gray and fresh

surfaces are sacchroidal and medium gray to brown with a fetid odor. Poorly preserved

coral fossils are common throughout the unit. The unit forms steppy cliffs and steep

slopes. Some beds within the formation are similar to the dark gray beds of the

Fishhaven Dolomite and some of the light gray beds are similar to the overlying

Devonian Sevy Dolomite. Bedding commonly is obscured but discontinuous beds of

chert can be found. The upper contact is above a chocolate brown striped unit with

some minor bedding parallel chert. The unit is exposed in ranges east and west of the

study area and is generally 305 to 336 m (1000 to 1430 feet) thick (Kleinhampl and

Ziony, 1985). The unit is 365 m (1200 feet) thick in the White Pine Range and 425 m

( 1400 feet) thick in the Horse Range.

Devonian System

Sevy Dolomite (Dse)

The Sevy Dolomite (Nolan, 1935) is a white to light-gray slabby to blocky

weathering fine-grained dolomite in the Lower Devonian. Fresh surfaces are dark to

medium gray and are fine to medium grained. The unit is 210 to 335 m (700 -1100

feet) thick and forms a steep slope with steppy ledges less than three meters thick. It is

generally unfossiliferous with some minor cross stratification. At the top of the unit is a

pale brown sandy unit. This thin capping sandstone unit was designated as the top of

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the Sevy Dolomite by Osmond (1954) and marks the top of the unit throughout much of

the study area.

Simonson Dolomite (Dsi)

The Simonson Dolomite (Nolan, 1935) is a fine-grained aphanitic dolomite

lying above the sandy unit at the top of the Sevy Dolomite. Weathered surfaces are

dark gray to chocolate brown and have a slabby to blocky fracture. Fresh surfaces are

dark gray to brown and coarsely crystalline. The unit is described by Nolan (1935) in

the Gold Hill Mining District, western Utah, and extends into ranges west of Railroad

Valley. The imit is 240 to 610 m (800 to 2000 feet) thick within the study area

(Osmond, 1954). White weathering solitary and spaghetti corals can be found within

the unit. Thin laminae and thick coarse-grained beds can also be found throughout the

unit. The upper contact is marked by an argillaceous yellow bed 1 to 3 m thick in the

White Pine Range. The upper contact was faulted in the Horse Range.

Guilmette Formation (Dg)

The Guilmette Formation (Nolan, 1935) is a thick unit of regularly layered gray

to brown limestone and dolomite cliffs containing thin argillaceous layers. The lower

brown-weathering limestone cliffs are similar to the brown dolomites of the Simonson

Dolomite. Massive pock marked beds commonly have an abundance of spaghetti coral.

Limestone breccias are common. The upper contact is between a brown weathered cliff

and an overlying resistant medium-gray cliff. The unit is 2000 feet thick in the study

area but is highly faulted in both ranges.

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Mississippian System

Joana Limestone (Mj)

The Joana Limestone is a 70 m (200 feet) thick limestone with local crinoid-rich

beds and irregular layers of chert above the Devonian Guilmette Formation. The basal

Joana Limestone is a medium-gray encrinite cliff. The top of this thin unit is a light tan

to wine colored (Lumsden, 1964) shaley unit less than 5 m thick. The unit was mapped

in the Gold Point block but does not crop out in the Horse Range. The unit was first

described by Spencer (1917).

Chainman Shale (Me)

The Mississippian Chainman Shale contains shale and sandstone beds of varying

thickness. The unit is exposed in small outcrops in the southern White Pine and

northern Horse ranges. Poor outcrops are exposed as buff brown to black soil with

small fissile shale flakes and a few nonresistant dark-brown weathering thinly bedded

sandstone ledges less than a meter thick. The unit is easily and commonly faulted so

the true thickness of the unit in the study area is unknown. The imit was described by

Sadlick(1960).

Diamond Peak Formation (Md)

A small outcrop of the Diamond Peak Formation is located on the eastern edge

of the Horse Range where it is a yellow to orange fine-grained sandstone. The grains

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are rounded and the unit is moderately lithified. The total thickness of the unit is

unknown. The unit was described by Hague (1883).

Pennsylvanian System

Ely Limestone (IPe)

The unit consists of light gray limestone with large and prominent light brown to

tan weathering brachiopods and coral fossils, and light-gray weathering crinoids. Green

to gray chert nodules 2-20 mm in diameter also crop out. Discontinuous steppy ledges

less than 1 m thick crop out on the eastern edge of the Horse Range where the total

thickness of the unit is unknown. The unit was not identified in the White Pine Range.

The outcrops of Ely limestone are small, surrounded by alluvium, and highly faulted,

therefore the nature and location of the upper and lower contacts is unclear.

Cenozoic Stratigraphy

One intrusive unit, seven Tertiary volcanic and five Quaternary (?) units are

identified in the study area (Figs. 4 and 6; Plate 1). Previous research within the study

area did not complete detailed subdivisions of these units. The volcanic rocks are

concentrated in the northeastern part of the study area. Modal point count analyses are

compiled in Table 1.

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Tertiary

Currant Stock (Tes)

The Currant stock is located in the north-central portion of the study area. The

unit is an altered granitic porphyry that intruded Mississippian Chainman Shale as

evidenced by: the angle between bedding in the Chainman Shale and the contact, local

metamorphism of the shale to a light tan color near the edge of the stock, and a block of

shale surrounded by the porphyry may be a roof pendent or a xenolith. The unit

contains quartz crystals ( 1 -5 mm), with highly altered biotite and feldspar in a fine

grained green to brown matrix. The unit is pervasively altered making dating difficult.

The stock is older than the 35.3+0.04 Ma Stone Cabin Formation that overlies the stock.

Stone Cabin Formation (Tsc)

The Stone Cabin Formation is an ~ 200 m (656 feet) thick phenocryst-rich unit

located in the central portion of the study area northeast of the Currant Stock. The unit

is locally highly welded and forms a resistant ridge, but the base is poorly welded. In

outcrop, the imit is light gray to brown in color and fresh surfaces are orange, brown,

black or gray. A lens of vitrophyre is exposed at the base of the unit but the zone is not

laterally continuous and is less than 10 m thick. The presence of the vitrophyre and the

lack of the hydrothermal alteration present in the Currant Stock suggest that the lower

contact of the Stone Cabin is depositional. Radke (1992) reports an '*°Ar/^^Ar

radiometric date of 35.34+0.07 Ma for the Stone Cabin Formation. The source for the

unit is thought to be southwest o f the study area in Railroad Valley (Radke, 1992).

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The Stone Cabin Formation contains 53% phenocrysts of large smoky to clear

quartz (<4 mm in diameter), biotite (< 4 mm in diameter), plagioclase and sanidine (<3

mm long) in a fine-grained matrix (Table 1). The unit also contains 5% pumice.

White Pine Range Rhyolite (Tr)

An unnamed highly altered rhyolite unit crops out in the northeastern portion of

the study area and called here, informally, the White Pine Range rhyolite. The unit may

be correlative with a rhyolite unit identified by Langrock (1995), 20 km north of the

study area.

The White Pine Range rhyolite is in depositional contact with the Stone Cabin

Formation east of the Currant Stock (Fig. 4, Plate 1). The unit contains large

plagioclase phenocrysts (6 mm), and minor quartz and sanidine in a fine-grained matrix.

Weathered surfaces are dark green to red and fi'esh surfaces are dark purple to gray.

Outcrops weather into flaggy blocks. Total thickness of the unit is unknown because

the unit is commonly faulted and the top does not crop out within the study area. The

basal contact with the Stone Cabin Formation is a sharp contact with no visible changes

in the unit at the contact.

Currant Tuff (Tc)

The Currant Tuff is approximately 200 m (656 feet) thick in the study area with

reported thicknesses of 300 m (1000 feet) 10 miles northeast of the study area (Faust

and Callaghan, 1948). The unit is located in the eastern portion of the study area and

consists of tuffs and sedimentary deposits (Fig. 4; Plate 1). The Currant Tuff is in

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depositional contact with the White Pine Range Rhyolite in the eastern part of the study

area. The Cfurrant Tuff also lies depositional above the White Pine Range rhyolite north

of the study area (Langrock, 1995).

The white to gray unit is easily distinguished from the other pink to brown

volcanic units in the study area. The tuff is poorly welded in outcrop but does form

cliffs and steep slopes near Currant Summit (Fig. 3). The Currant Tuff contains visible

phenocrysts, large rock fragments and pumice ( 1 —40 cm). The tuff also contains clear

to smoky quartz (<4 mm in diameter), biotite (<2 mm in diameter), and plagioclase.

The unit is poorly welded and very porous with large pore cavities.

Tuff of Pritchards Station (Tps)

A 20-30 m thick phenocryst-rich rhyolitic tuff forms rounded outcrops and

ledges in the eastem portion of the study area. The unit contains large quartz

phenocrysts, but fewer than the Stone Cabin Formation. Biotite (<2 mm across) and

plagioclase are also abundant. The stratigraphie position of this unit below the Windous

Butte and above the Stone Cabin Formation suggests that this unit is the Tuff of

Pritchards Station. The lower contact of the tuff with the Currant Tuff is not exposed

within the study area. The Tuff of Pritchards Station is in fault contact with other units

or the base is covered by alluvium. The phenocryst assemblage of the unit matches a

description by French (1998). The Tuff of Pritchards Station also occurs west of the

study area in Railroad Valley and the Pancake Range (French, 1998).

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Unnamed Ash-flow Tuffs (Tvl and Tv2)

Two thin ash-flow tuffs are exposed in the middle of the Tertiary section.

Previously described correlative units are not found in the literature. The lower unit

(Tvl) is less than 10 m thick with less than 5% phenocrysts (sanidine, quartz, biotite) in

a red to brown rich matrix (Table 1 ). The unit is dominated by glass shards and

flattened pumice (<6 mm across). The unit is densely welded, commonly weathers to a

“popcorn texture” and maintains its pink to brown color. The basal contact is a poorly

welded zone (< 1 m thick) above the Tuff of Pritchards Station.

The upper unit (Tv2) is a densely welded ash-flow tuff less than 5 m thick. The

unit crops out as a small ledge in only a few small locations in the northeast portion of

the study area (Fig. 4; Plate 1). Weathered surfaces are commonly orange, brown or red

in color while fresh surfaces are dark brown to red. The unit has even fewer

phenocrysts of plagioclase feldspar and sanidine than the lower ash-flow tuff and has a

large amount of glass and flattened pumice. The base of the unit is a poorly welded

zone < 1 m thick.

Windous Butte Formation (Twb)

The Windous Butte Formation forms a 6-10 m high cliff in the northeastern

portion of the study area (Fig. 4; Plate 1). The unit is highly welded and contains large

quartz (1-5 mm), plagioclase and sanidine crystals (< 3 mm) in a pink to brown matrix

(Table 1 ). Weathered outcrops are red to brown and the tuff exhibits some columnar

jointing. The base of the unit is commonly not exposed, but a dark black vitrophyre <1

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m thick was present along the exposed contact with Tv2 in the northeast portion of the

study area.

An ‘‘°Ar/^^Ar laser fusion dates for seven sanidines and three plagioclases

yielded an age of 31.25 ±0.04 Ma for this tuff. The sample was collected in the

northeastern portion of the study area (Fig. 14; Table 2). This age matches a 31.27

±0.03 Ma date by Best et al. (1989) for the Windous Butte Formation. The unit is

thought to be the flrst rhyolitic unit to have erupted from the Central Nevada Caldera

Complex (Cook, 1965; Phillip, 1989).

Tertiary Basalt (Tb)

A thin basalt unit caps a small hill above the Currant Tuff in the extreme eastem

portion of the study area (Fig. 4; Plate 1 ). The unit is black to brown in outcrop and

black on fresh surfaces. The unit is fine grained with small plagioclase (1-4 mm) and a

large number of vesicles. The exact age of the unit is unknown, but regional

relationships indicate the unit was deposited late in the volcanic history. Basalt units

exposed northeast of the study area are in depositional contact with several units and

locally fill channels.

Tertiary Ash-fall Tuff (Ta)

A thin (<2 m) and small outcrop of highly altered ash fall tuff is exposed in the

southeastern comer of the study (Fig. 4; Plate 1). The unit overlies the Devonian

Guilmette and Simonson formations. The unit is light brown to tan in outcrop and

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consisted of pumice, glass shards, and lithic fragments of carbonate and volcanic rocks.

The contact with the underlying Paleozoic rocks is a sharp contact.

Tertiary Volcanogenic Sediments

A small area north of the Currant Summit fault comprises reworked volcanic

rocks. Large boulders and cobbles of surrounding volcanic rocks occur in a medium to

fine-grained matrix of altered volcanic rocks. The unit may be a landslide or slump

deposit.

Quaternary Stratigraphy

Quaternary alluvial, fluvial, playa, and fan deposits are mapped within the

research area. Location, elevation, cross-cutting relationships, rock or sediment type,

rock size, and lithification were used to distinguish and map the units. The descriptions

below were used for field identification of the Quaternary units.

Quaternary and Tertiary (?) Older Fan Gravels (QTf)

The Quaternary and Tertiary older alluvial fan units are exposed in the lower

elevations surrounding both the White Pine and Horse ranges. The fan surfaces may be

slightly lithified by calcium carbonate cement and are dissected by younger stream

channels. Boulder-size clasts of proximal rock units occur near the break in slope at the

base of outcrops in both ranges. Colluvium at the base of outcrops is also included in

this unit. Angular to subangular clasts are common and clast size decreases with

distance from outcrops. The matrix is gravel to silt. The alluvium is heavily vegetated

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by brush and junipers but soil development is limited. Desert pavement occurs locally

in well-exposed areas.

Young Quaternary Fans, Undissected (Qf)

Young alluvial fan deposits fill dissections in the older Quaternary and Tertiary

fans. The young Quaternary fans are light tan to brown unconsolidated to moderately

consolidated sands and gravels with developed vegetation. The clasts are rounded to

subrounded. Clasts vary in size and consist of sand, gravel and boulders of the older

alluvial fan deposits or proximal rock units. The unit is generally exposed in the central

portion of the study area and may have some caliche development.

Quaternary Alluvium (Qa)

The unit is tan to brown imconsolidated silt, sand and gravel in active fluvial

washes that incise the QTf and QTfu. Clasts are rounded to sub-angular and range from

sand to boulder in size. The clasts are Paleozoic carbonates. Tertiary volcanic rocks,

and jasperoid. Quaternary alluvium varies in width (1-30 m) and thickness (< 5 m).

Quaternary Lacustrine (?) (silt or clay deposits) (Ql)

A light tan to brown slightly consolidated clay and silt unit crops out west of a

small lake in the central portion of the study area. The unit is in the lowest part of the

valley and the thickness is unknown. The unit is covered with brushy vegetation and

may be a shallow lake during extremely wet seasons.

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Quaternary Colluvium (Qc)

Unconsolidated pebble- to boulder-size clasts are mapped as colluvium. The

unit consists of angular clasts of proximal rock units and is exposed on or at the base of

steep slopes. Colluvium skirting outcrops above alluvial fans are included with the

older fan gravels.

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■ D CD

WC/) 3o' 0 Tabic 1. Modal percentages from point-couni analysis of the volcanic units in the study area. Proportions of phenocrysts arc with respect to 100%. 3 Total phenocrysts is the percentage of phenocrysts relative to other rock constituents. W PR-13.5 is a thin vitrophyre above the ash-flow lull Tv I. CD 8 ■D M odal A lkali H orn- Fe- Total pore lithic Unit/Sample # ()uar1z Feldspar Plag. P>Toxenc Hematite Olivin Biotite blende O xides Phenocrysts m atrix pum ice space fragments Total (O'3" 1 Windous Butte 3 CD F orm ation WPR-24.5 41.6 35.5 14.5 0.5 0.9 0.0 6.5 1.4 0 .0 0 35.5 6 3 .0 1.2 0.0 0.0 100.0 c-n 3. 3" CD Ashflow tuff WPR-13.6(Tv2) 34.4 35.1 15.3 1.5 0.0 0 .0 0 .0 6 .9 6.9 27.7 72.3 0.0 22.2 0.0 100.0 ■DCD O CQ. A shflow lutT Oa WPR-13.5 (Tvl') 15.5 52.5 26.7 3.0 2.0 0.0 1.0 1.0 5.9 17.7 67.0 11.7 1.0 2.6 100.0 3 ■D O A shflow tu ff W PR-7.id(TvI) 8.7 87.0 17.4 0.0 3 9 1 0.0 0 .0 4.3 13.0 4.2 7 3.9 7.9 5.3 0 .0 100.0

Q.CD Tuff of Pritch ards Station W PR -25.5 41.9 13.4 29.1 0.3 0.0 0.6 6.4 8.3 1.6 58.0 42.0 5.0 0.0 1.5 100.0

■ D CD White Pine Range (/) (/) R hyolite WPR-25.5 3.6 0.7 25.2 0.0 0.0 0.0 1.4 0.0 0 29.5 39.3 0.0 0 .2 0.0 100.0

Stone Cabin Form ation WPR-84.I 49.7 18.6 19.9 0.3 0 .0 0.0 1.0 10.5 1.0 55.2 42.1 2.3 0.4 0.0 100.0

LAoe 86

Weighted mean = 31.26 Std. dev.= 0.044

29 Age (Ma)

Figure 14. Ar/^Ar age probablity curve of sample NDWPR-24.5. The curve is produced from 7 sanidine and 3 plagioclase crystals of the Windous Butte Formation. The probability curve identified an age of 31.26 ± 0.04 Ma

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■D CD

C/) Table 2. ^"Ar/^’Ar laser fusion data for 7 sanidine and 3 plagioclase cry stals of the upper volcanic unit, the Windous Butte Formation, C/) in the southern White Pine Range, Nevada. Both a mean age and weighted mean age with 1 o standard deviations are reported. One crystal is omitted from the weighted mean calculation.

CD ^A r ■D8 Crystal “Ar ''Ar ^*Ar ”Ar % "A r* Ca/K ^Ar*/*’ Age (Ma) Std. Dev. 1 0.10 0.50 1.53 114.52 1714.70 98.2 0.01396 14.7443 31.327 0.199 (O' 2 0.07 0.40 1.06 79.98 1195.80 98.4 0.0158 14.7277 31.292 0.199 3* 0.04 14.10 0.05 3.58 61.93 92.9 12.6125 14.995 31.855 0.383 4 0.04 11.08 0.05 2.64 46.70 90.3 13.4421 14.514 30.842 0.477 5 0.12 0.51 1.50 113.94 1703.02 98.0 0.01428 14.6797 31.191 0.198 3. 3" 6 0.02 0.45 0.75 57.04 847.93 99.6 0.02494 14.7946 31.433 0.200 CD 7 0.31 0.24 0.54 36.48 625.11 86.1 0.02099 14.6973 31.228 0.201 ■DCD O 8 0.08 0.57 1.05 80.10 1200.97 98.2 0.02254 14.731 31.299 0.199 Q. C 9 0.09 20.91 0.13 8.59 148.49 86.5 7.78221 14.5416 30.900 0.207 a 10 0.06 0.43 1.10 84.08 1255.65 98.7 0.01628 14.7419 0.199 3O 31.322 "O Mean= 31.269 Ma O 1 o = 0.28

CD Q. Weighted Mean= 31.254 Ma J = 0.001188+/-0.5% I o = 0.044 ■D 4 amu discrimination = 1.02 +/- 0.18% CD 40/39K = 0.0505+/-94.4%, C/î(/) 36/37Ca = 0.0002771 +/- 1.6% 39/37Ca = 0.0007433+/-8.5% Note; Isotope beams in mV rlsd = released, error in age includes 0.5% J error, all errors I sigma Samples arc not corrected for decay. ^Sample #3 was omitted in weighted mean calculation because age was greater than 2 sigma away from the rest of the population. Laser power is 2 watts. Analyses performed under the supervision of Dr. I . Spell at the Nevada Isotope Gcochronolog)' Laborator) , University of Nevada, Las Vegas.

3 APPENDIX 2

USING ARCVIEW TO CREATE GEOLOGIC MAPS

The final geologic map was produced using ArcVtew GIS 3 .2 with a Windows

NT desktop computer. In Arc View, detailed geologic information can be accessed,

added, altered, and manipulated. The following provides general information on how

Arc View was used to create the geologic map. Basic Arc View steps are omitted and

detailed information on specific items can be found in the Arc View Help menu and at

the ESRI website fwww.esri.com).

1. Importing the field map into Arc View.

Field data was initial collected and recorded on traditional USGS 7.5 minute

quadrangles. Geologic maps were scanned on a large format scanner and made into an

image file (.jpeg). The image must be imported into ArcView with a world file A

world file contains the coordinates of the image, the number of pixels of the image, and

the size of the pixels. The world file allows the image to be geospatially referenced in

ArcView.

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2. Creating the geologic map.

The geologic map was created by digitizing the field data on the map image file

into ArcView. A single polygon theme was created for all of the stratigraphie units. A

line theme was created for all of the high-angle faults and another for the low-angle

faults. Each unique data set was made into one theme.

Information about the features in a theme can be added to the theme attribute

table. Information was compiled in the theme attribute table as the shape file was

created. All the polygons for a specific unit were given the same identification and

gridcode values for easy manipulation in the future (e.g., the number six was given to

all of the Devonian Guilmette Formation polygons; the polygons were labelled as Dg in

another column). This method allows a color or line weight to be assigned to each

identification number and allows the unit to be easily labeled.

Additional information that is generally not displayed on a geologic map can be

added to the theme table (i.e., field notes, details o f a sample location). This

information can then be viewed in ArcView by clicking on the desired object with the

identify. A window appears and lists all the additional information for the unit.

3. Digital Elevation Maps

Digital elevation models (DEM) were downloaded from the USGS mapping

website at www.mapping.usps.gov. The DEM is a grid file of the desired quadrangles.

A variety of scales are available on the USGS website.

The files on the website must be converted to a format readable by ArcView.

First, the files were downloaded and unzipped. The files were then converted to a

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format readable by ArcView using the sdts2dem.exe program that is also available on

the USGS website The DEMs can then be imported into a view in ArcView. The

OEMs are the base maps for the creation of contour maps and for overlaying geology.

4. Warp Extension

The image imported into ArcView was not exactly geospatially referenced with

respect to the elevation grid base maps. Folds in the paper map, defects in the scanned

image, or an imprecise world file alter the shape of the scanned image so that the

geologic data did not correlate with the elevation models and known coordinates. For

example, a known UTM coordinate o f630,000 m east and 43,000,000 m north on the

scanned image may appear in ArcView as 630,075 m east and 43,000,400 m north.

An ArcView extension, Warp.avx, was used to correct errors in the scanned

image. Forty-eight control points were used to correct the problem. The extension was

downloaded from the ESRI website. The UTM grid on the scanned image was used to

identify known coordinates. Shape files were first converted to grids because the Warp

extension only works for grids. The Warp extension creates a new grid that is properly

geospatially referenced. The extension works better with an increased number of

control points that are widely and evenly spaced. A large number of grid points also

allow for a higher order of resampling to be completed. This project used an 8*’’ order

Nearest Neighbor warp calculation. The warped data was checked to make sure it

matched the field map and the DEMs. Each grid theme must be warped individually.

Warped grids can be converted back to shapefiles for easy manipulation.

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Some georeferencing problems can be minimized by making sure the map to be

scanned is void of folds or gaps. Coordinates and pixel size are more easily identified if

the image is scanned squarely and if the scanned image has a uniform boundary.

4. Strike and dip symbols

Themes were created for all the strike and dip data. ArcView contains the strike

and dip symbol but the symbol must be rotated to the proper orientation. An Excel

spreadsheet was created with the proper rotation angle for the strike and dip symbol.

The spreadsheet was joined to the theme attribute table in ArcView. The symbols can

then be rotated by selecting the proper column to be used for rotation in the Legend

Editor.

5. Map Presentation

After all the polygons, faults and data points are properly georeferenced, fields

and units can be labeled. ArcView conatins an autolabel feature that allows you to pick

a column from the theme attribute table as the label field. All of the unit name

abbreviations were placed in a column in the theme attributes table. The ArcView

autolabel function does not always place the material in an ideal location so some

manipulation of the label is required. It is best to save the autolabel until last because it

drastically slows down ArcView. Contour lines can also be autolabeled but the

placement of the label is generally poor.

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ArcView is a powerful tool with many useful applications for geologists. This

research shows that ArcView GIS 3.2 on a desktop computer can be used for geologic

map production. New tools and extensions will make map production in ArcView

faster and easier to complete.

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Snyder, D B , Healey, D L , and Saltus, R W , 1984, Bouguer gravity map of Nevada, Lund Sheet: Nevada Bureau of Mines and Geology, Map 80.

Speed, R C , Elison, M W , and Heck, F R , 1988, Phanerozoic history of the western Great Basin, in Ernst, W G , éd.. Metamorphism and crustal evolution, western United States: Rubey volume 7, p. 573-605.

S.'encer, A C , 1917, The geology and ore deposits o f Ely, Nevada U.S. Geological Society of America Professional Paper 96, 189 p.

Snyder, D B , Healey, D L , and Saltus, R W , 1984, Bouguer gravity map o f Nevada, Lund Sheet: Nevada Bureau of mine and geology Map 80, scale 1:250,000.

Stewart, J H , and Carlson, JE , 1976, Cenozoic rocks of Nevada; Four maps and brief descriptions of distribution, lithology, age, and centers of volcanism: Nevada Bureau of Mines and Geology Map 52.

Stewart, J H , 1980, Regional tilt patterns of late Cenozoic basin-range fault blocks, western United States: Geological Society of America, v. 9, p. 460-464.

Stewart, J H , 1998, Regional characteristics, tilt domains, and extensional history of the Late Cenozoic Basin and Range, western North America, in Faulds, J E , and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101

Stewart, J.H., eds.. Accommodation zones and transfer zones; The regional segmentation of the Basin and Range province. Boulder, Colorado, Geological Society of America Special Paper 323, p. 47-74.

Switzer, D.D., 1996, The geology and structures of the northern Hi ko Range, Lincoln County, Nevada. M.S. thesis. University o f Nevada, Las Vegas, 129 p.

Taylor, W.J., Bartley, J M , Lux, D R , Axen, G J , 1989, Timing of Tertiary extension in the Railroad Valley-Pioche transect, Nevada: Constraints from ^Ar/^^Ar ages of volcanic rocks: Journal of Geophysical Research, v. 94, p. 7757-7774.

Taylor, W.J., Bartley, J M , Fryxell, J E , Schmitt, J.G , and Vandervoort, D.S.,1993, Tectonic style and regional relations of the central Nevada thrust belt: in Lahren, M M., Trexler, Jr., J.R , and Spinosa, C , eds., Crustal Evolution of the Great Basin and Sierra Nevada: Cordilleran/ Rocky Mountain Section, Geological Society of America Guidebook, Department of Geological Sciences, University of Nevada, Reno, p. 57-96.

Taylor, W.J., Bartley, J M , Martin, M W , Geissman, J W , Walker, J D , Armstrong, P A , Fryxell, JE , 2000, Relations between hinterland and foreland shortening: Sevier orogeny, central North American Cordillera, Tectonics, in press.

Taylor, W.J., Johnson, J A., and Walker, J D , 1996, Kinematics and mechanics along a low-angle normal fault, the Silver Spring detachment, central Nevada, in Taylor, W.J., and Langrock, Holly, eds., Cenozoic structure and stratigraphy of central Nevada, 1996 Field Conference Volume, Nevada Petroleum Society Inc., Reno, p . 7 5 - 8 4 .

Taylor, W J , Williams, N D , and Shigehiro, M ,1999a, Tectonics and paleogeography of the K-Eocene Basins, Nevada and Utah: Geological Society of America Abstracts with Programs, Cordilleran Section, v. 31, p. A-101.

Taylor, W J , Williams, N D , Switzer, D D , 1999b, Complex composite histories of transverse faults: Geological Society of America, Abstracts with Programs, v. 111, A-377.

Thenhaus, P C , Bamhard, T P , 1998, Insights from Quaternary relations for segmentation of the Great Basin by regional, transverse accommodation zones, in Faulds, J.E., and Stewart, J H , eds.. Accommodation zones and transfer zones: The regional segmentation of the Basin and Range province: Boulder, Colorado, Geological Society of America Special Paper 323.

Tracy, W.C., 1980, Structure and stratigraphy of the central White Pine Range, east- central Nevada: M.S. thesis, California State University, Long Beach, 70 p.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102

Vandervoort, D.S., Schmitt, J.G., 1990, Cretaceous to early Tertiary paleogeography in the hinterland of the Sevier thrust belt, east-central Nevada: Geology, v. 18, p. 567-570.

Walker, C.T., Francis, R.D., Dennis, J.G, and Lumsden, W W , 1992, Cenozoic attenuation detachment faulting, a possible control on oil and gas accumulation in east-central Nevada: American Association of Petroleum Geologists Bulletin, V. 76, p. 1665-1686.

Wells, M.L., Dallmeyer, R D , and Altmendinger, R W , 1990, Late Cretaceous extension in the hinterland of the Sevier thrust belt, northwestern Utah and southwestern Idaho: Geology, v. 18, p. 929-933.

Wells, M L , Snee, L W , and Blythe, A E , 1994, Mesozoic and Cenozoic extensional history of the northeastern Great Basin, Insights from the Raft River and Grouse Creek mountains: Geological Society of America Abstracts with Programs, v. 26, no., 2, p. 103.

Wells, M L , 1997, Alternating contraction and extension in the hinterland of orogenic belts: An example from the Raft River Mountains, Utah: Geological Society of America Bulletin, v. 109, p. 107-126.

Wernicke, B, Axen, G , and Snow, J , 1988, Basin and Range extensional tectonics at the latitude of Las Vegas. Nevada: Geological Society of America Bulletin, v. 100, p. 1738-1757.

Wernicke, B, 1992, Cenozoic extensional tectonics of the U.S. Cordillera, in Burchfiel, B.C., Lipman, P W , and Zoback, M L , eds.. The Cordilleran Orogen: Conterminous U.S.: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G-3, p. 553-581.

Westgate, L G , and Knopf, Adolph, 1932, Geology and ore deposits of the Pioche district, Nevada: U.S. Geological Survey Professional Paper 171, 79 p.

White, N., 1992, A method for automatically determining normal fault geometries at depth: Journal of Geophysical Research, v. 97, p. 1715-1733.

Wire, J.C., 1961, Geology of the Currant Creek district, Nye and White Pine Counties, Nevada: M A thesis. University of California, Los Angeles, California, 154 p.

Zoback, M L , 1989, State of stress and modem deformation of the Northern Basin and Range province: Journal of Geophysical Research, v. 94, p. 7105-7128.

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Department of Geoscience University of Nevada, Las Vegas

Nathan D Williams

Local Address; 2380 Natalie Ave Las Vegas, NV 89109

Home Address; 2336 Free State Lane Lawrence, Kansas 66047

Degree: Bachelor of Science, Geology, 1997 University of Kansas, Lawrence, Kansas

Special Honors and Awards: American Association of Petroleum Geologist student research grant, 1998 Geological Society of America graduate student research grant, 1998 Nevada Petroleum Society summer research grant, 1998 University of Nevada, Las Vegas Geoscience Department M.S. research grant, 1998 University of Nevada, Las Vegas Graduate College summer research grant, 1998 Erasmus Haworth Honor Award for outstanding graduating undergraduate, 1997 Selig Summer Research Fellowship Grant 1996 Ray P. Walters Scholarship for excellence in academics 1996

Publications: Williams, N D , and Taylor, W J , Role of transverse faults in extension, central Nevada: Geological Society of America Abstracts with Programs, Cordilleran Section, v. 31, p. A-108.

Taylor, W J , Williams, N D , and Shigehiro, M , Tectonics and paleogeography of the K-Eocene Basins, Nevada and Utah: Geological Society of America Abstracts with Programs, Cordilleran Section, v. 31, p. A-101.

103

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104

Williams, N D , Tectonic and structural analysis of a transverse fault in an extended terrane, the Currant Summit fault. Basin and Range province, Nevada; AAPG Bulletin, v. 82, p. 2170.

Omdorff, R L , Downing, R F , Jones, T.A., Ogan, B D , Rotert, J W , Sanford, A.L., Williams, N D , Willse, K.R., Building a GlS-based flood model for the Las Vegas basin in an applied spatial modeling course at the University o f Nevada, Las Vegas: Geological Society of America Abstracts with Programs, v. 83, p. A-808.

Thesis Title: Tectonic and structural analysis of a transverse fault in an extended terrane, the Currant Summit fault. Basin and Range province, Nevada

Thesis Examination Committee: Chairperson, Dr. W J Taylor, Ph.D. Committee Member, Dr. R V Metcalf Ph.D. Committee Member, Dr. M L Wells, Ph.D. Graduate Faculty Representative, Dr. G. Rhee, Ph.D.

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38° 52 ' 30 "

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Plate 1. Geologic Map of Cui

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^ye County, Nevada

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Plate 1. Geologic Map of 1 Currant Summit Fault Zone Nye County, Nevada

L 38°52' 30"

1 Unit Key Cenozoic Paleozoic

I Quateraaiy Pennsvlvanian

Qa Active alluvium Elv Limesti

Colluvium Mississippi Ql Lacustrine deposits Md Diamond P Old alluvium Chamman I QTf Old fan deposits Joana Lime

Tertiary (Units inset when strat. position uncertain) Devonian

) Guilmette F Volcanogenic sed. unit

Jasperoid Simonson I

Ash fall Se\y Dolon

Silurian Basalt flow Laketown D Windous Butte Fm.

Uimamed rhyolite tuff Ordovician

Ash flow tuff I T_T—____— Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Plate 1. Geologic Map of the Currant Summit Fault Zone, Nye County, Nevada

3 0 "

U nit K ey Cenozoic Paleozoic

Q u a te r n a r y Petinsvlvanian

Q a Active alluvium Elv Limestone

Colluvium m Mississippi Ql Lacustrine deposits Md Diamond Peak Fm. Qoa Old alluvium Chainman Shale

QTf i Old fan deposits Joana Limestone

Tertiary (Units inset when strat. position uncertain) Devonian

Volcanogenic sed. luiit Dg Guilmette Formation

Jasperoid Simonson Dolomite

Ash fall Sevy Dolomite

Silurian Basalt flow Laketown Dolomite Windous Butte Fm.

Unnamed rhyolite tuff Ordovician

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. QTf P ■--'1 -

iU g

r g y

r) r - C^f 74- J r.- j

j ’ -I- : '■ •/ - i* -.<• - - .

Q T £

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Unnamed rhyolite tufT / i l 7 Ordovician Ash flow tuff Fish Haven Dok

Tuff of Pritchards Station Eureka Quartzitc

Currant Tuff Antelope Valiev

White Pine Range rhyolite -N Ninemile Formal

Stone Cabin Formation Goodwin Formal

intrusion (dike/sill) Cambrian Currant Stock Wmdfall Format

Dunderberg Shal

Lmcoln Peak Fm

Upper Pole Cany

Pole Canvon Lirt

Pioche Shale \ Prospect Mounta

Symbols and Contacts

-I— . Strike and dip o f bedding

— Strike arid dip o f compaction foliation

a— Strike and dip o f joints

Brecciation. Placed in areas 6a V ■û where rocks are fractured and faulted Anticline. Positioned on the trace of the axial surface. Arrow on axial trace points in the direction of plunge.

Syncline. Positioned on the trace of the axial surface. Arrow on axial trace points in direction of plunge.

Stratigraphie contact. Dashed where / V approximately located and dotted where concealed under alluvium. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^.naoviciao

Ash flow tufT Fish Haven Dolomite

TufT of Pritchards Station Eureka Quartzite

Currant TufT Antelope Valley Ls.

White Pine Range rhyolite Ninemile Formation

Stone Cabin Formation Goodwin Formation

intrusion (dike/sill) Cambrian

Currant Stock Windfall Formation

Dunderberg Shale

Lincoln Peak Fm.

Upper Pole Canyon Ls.

Pole Canyon Limestone

Pioche Shale

Prospect Moimtain Quartzite

Symbols and Contacts

-I— Strike and dip of bedding

*— Strike and dip of compaction foliation

Strike and dip of joints

Brecciation. Placed in areas ^ ^ where rocks are fractured and faulted. 4 'I Anticline. Positioned on the trace of the axial surface. Arrow on axial trace points in the direction of plunge.

Syncline. Positioned on the trace of the axial siuface. Arrow on axial trace points in direction of plimge.

Stratigraphie contact. Dashed where approximately located and dotted where concealed under alluvium.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. %

3 8 ° 4 5 '

1 1 5 ° 30'

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 Miles

Contour interval = 40 feet

Map Scale 1:24,000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 Kilometers

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Stratigraphie contact. Dashed where \ / ■\ approximately located and dotted where concealed under alluvium.

Tie line. Used to identify areas with the same formation natne where one area is too small to be labeled.

Normal fault Dashed where approximately J______located and dotted where concealed under alluvium. Ball and bar are on the hangingwall.

Low angle normal fault. Dashed where approximately located and dotted where concealed under alluvium. Tick marks are on the hangingwall.

Reverse fault Dashed where u approximately located and dotted where " d * concealed under alluvium. U is on upthrown block. D is on the downthrown block. Oblique-slip fault. Dashed where approximately located and dotted where concealed under alluvium. Arrows show direction of motion. Ball and bar are on the hangingwall.

mapping completed on 38°45' N Currant Summit and White Pine Peak USGS 7.5' quadrangles 115" 5

Magnetic declination; 15 degrees East.

mapping by Nathan D. Williams May 2000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. of the axial surface. Arrow on axial trace points in the direction o f plunge.

Syncline. Positioned on the trace of the axial surface. Arrow on axial trace points in direction o f plunge.

Stratigraphie contact. Dashed where approximately located and dotted where concealed under alluvium.

Tie line. Used to identify areas with the same formation name where one area is too small to be labeled.

Normal fault Dashed where approximately 2 ______located and dotted where concealed under alluvium. Ball and bar are on the hangingwall.

Low-angle normal fault. Dashed where approximately located and dotted where concealed under alluvium Tick marks arc on the hangingwall.

Reverse fault Dashed where u approximately located and dotted where " o ' concealed under alluvium. U is on upthrown block. D is on the downthrown block. Oblique-slip fault. Dashed where approximately located and dotted where T _____ concealed under alluvium. Arrows show direction o f motion. Ball and bar are on the hangingwall.

mapping completed on 38°45' N Currant Summit and White Pine Peak USGS 7.5' quadrangles 15"

Magnetic declination: 15 degrees East.

mapping by Nathan D. Williams May 2000

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Oversize maps and charts are microfilmed in sections in the following manner;

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8000- h 2000

7000 - t

1500

(m) 'IÊ 4000 -I (feet)

p G K ?)

a. Present-day ax)ss section iK)i1h of the Cunant Summit feult

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. . ■day and restored cross- ^e, Nevada

D-D'

fauit

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ;s-section A-A',

Mc-IPfe(?) Mc-IPe (?) ^ / Mc-ip6(?) " 1 1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. U nit Key’

Cenozoic P ftleozoic Qiutemoy hfisæâppian - Pennsylvmiai i Active alluvium O' Pennsyivaniai Ely Limestone

CoUuvium □ Mc-IPe Md DiancndPeak Eæt A" Q1 I Lacustrine deposits Me ChaamnmSbak

Q h Old alluvium Joama Limestone Tc

Devonian Quafcmaiy - Ternary Dg Guümette Formation

Oldâadepoâts %(?) Simonson Dolomite

Tertiay (inset where straL Sew Dolomite poâtion incertan)

Tu' Voicanogaiki sed unit Silirian □ . Laketown Dolomite

Ta Ash fall Ordovician Tb Ofh Fish Haven Dolomite

\^ndous Butte Fomution Eueka Quotité

V 2H Unnamed ihyalite Antelope Valley Limestone

Ash flow Mneimle Formation Tuff of Mchards Station

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. « m a

« a s

b. Retrodefoimed ox)ss section A-A', north o f the Currant Sumnü Movement in and out o f plane o f cross section not restored. T

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. It

D-D' Tv Tps Tr

Mc-IPe (?]

summit fault Restored to pre-extensional state (~ Miocene). red. The Currant stock mayOr not be present at time o f retrodeformati

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. E-E Twb

Tv2

Mc-IPe (?) Mc-IPe (?)

jimation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A«ut Ordovician

Oflv Fidi Pbven Dolomite

\vbH Windous Bute Fonn^kn Eureka Quartzile v2aH Unnamed ifavolite Antelope Valley Limestone sa Ash flow Ninemile Formaticn Tuff of PritcfaaFds Station Goodwin Formation }TcB Currant Tuflf

Cambrian Tr White Pine Range ihyolite Windfall Formation Slooe Cabin Fctmadon

Dtndaberg Shale Ti Intrusion □

Lincoln Peak Formation Cuirant Stock

Upper Pole Canyon Limestone 2000 feet

609.6 km Pole Catwon Limestone

No vertical exaggeration

by- Nathan D. WDiams, Mav 2000 Pioche Shale

Prospect Mountain Quartzite

Aecantriai

Basemert

*Unit colors on the cross sections may vary slightly from-mil colors on map. □ Units not present on this plalê

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Oversize maps and charts are microfilmed in sections In the foliowing manner:

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West

B C-C D-D'

8000-

7000- Clp QTf

6000-

5000_ 1500'

4000-

a. Present-day cross section B-B', south of the Currant Summi

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. y and restored cross sec ida

Ofh Qq

Summit fault

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. section B-B',

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Unit Key

Cenozoic P b k o z D k QuaienMO M hrindppit - Pmmylvreihm Poinsjivaniai Ely Limestone I - Active alluvium

0= CoUuvium Mc-lPe Md Diamond Peak

Q 1 I Lacustrine deposits Me ChanmaiShale ^

□ Qdh Old alluvium Joana Limestone

Devonian

OldÊmdepoâs Dg Guilmette Formation

Tertiaiy (inct where atret poatk» unoerUn) Simonson Dolomite

Vdcanogoiic sed unit^ Sew Ddomile

Jaspaoid

S lu ria n Ta Ash fall tuff Laketown Dolomite

Tb Basalt □

O rdovldan iTwfo H WindousBitteFotmaticn □ Ofh Fish Haven Dolomite v2 S Unnamed di>olite ^ EuekaQuarlzite Ash flow □ Antelope Valley Limestone Tuff ofPrkcbards Station Ninemile Formation Cirrait Tuff

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a. Present-day cross section B-B', soudi of the Currant Summ

D-D'

C-C

b. Retiodeforaied cross section B-B', south o f the Currant Surm Movemait in and out of plane o f cross section not restored.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ummit fault

“^<3 '

ses^jSSa®

it Summit feult Restored to pre-extensional state (~ Miocene). stored.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. E-E'

Oligocène or older fault

♦Unit a ^Unilsi

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Volcanogouc sed mit "Tu Sevy Dolomite

Ta Ash fall tuflf Laketown Dolomite

Tb Basait ^

O rdovidan Twb H Windous Butte Fonnîtion Ofh Fi* Haven Dolomite Unnamedihyolhe ^ EmekaQuatdte C :,Tvl S Ash flow Antelope Valley Limestone Tuff of Pritchards Station^ Ninemile Formation ijc Ira Cmnnt Tuff Goodwin Foimaion Tr White Pine Rtnge rlwoiite

Cambrian sc ■ Stone Cabin Fcxmatian C s

'^ w Windfall Formation Ti ! Intrusion

Dmdeibeig Shale cs Cunant Stock

Lincoln Peak Fonnation

2000 feet Upper Pole Canyon Limestone I------1 609.6 km

No vertical exaggeration Pole Canvcn Limestcne

b%'Nathan D. WiDians, May2000 Piocfae Stale

♦Unit odors on the cross sections may vaiy sli^tly from trnit colors on map. Prospect Mountain Quamdte ^ Units not present on this plate.

uodififeieitialed sed. rocks a .

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Oversize maps and charts are microfilmed in sections in the following manner:

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Northwest

C A-A*

Og Gfe

2000

1500

W (feet)

a Present-day ooss sectioii C-C’(Not retrodefoi

South D B-B'

8000

TOO __ QTf 2000 Qa n rr repréduGlion prohibited without penhiss.oh. of the copyright owner. Further Reproduced with permission Tesent-day cross sections 1 the White Pine and Ho

ScUheasi C B-B'

Og Cb Cw /

xxiefoimable because of movement in and out of plane o f cross section

North A-A' *D'

3 ^ © 1® Dg J Dg Dg \ \ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. tons C-C, D-DV Horse ranges, Nevada.

□ufeeasl C

Cènozoîc

Active Q« :ip u: Qc Colluv

Ql Lacustri

I Qb I Old alli

CHd&n 3SS section.) Tcrtiuy(HnM

--Tu •©

Tb B

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ida.

Unit Key’

Cenozoic Paleozoic

QuaÉeinar>- Mhrtwjppii - PtamylviÉMi Active alluvium Pennsylvanian Ely Limestone

Colluvium Q: Mc-IPe Md j Diamond Peak □

Ql Lacustrine deposits Me Channoi Shale

Qoa Old alluvium Mj: Joana Limeskne

Quateman'-Tertiaty Devonsnm QTf Old fan deposits Dg Guilmette Formation

Tertiaiy (units inset #b*n straL position in œ rtan ) Simonson DOlomile

-Tu Vdcanogenic sed unit ^ Sew Dolomite

Jasperoid

Sliirten i . Ash fall Lakatown Dolomite □ Tb Basalt

^Twb M Windous Butte Foonaticn □ O rdovidan

Ofh Fish Haven Dokmite fv2 œ| Unnamed ihvoiite

EudcaQuatalB Tvl % Ash flow

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8000 _ _

7000 _ _ QTf 2000 Qa QTf 6000 D g r 5000 1500

4000

(m) (feet)

b. Present-day cross section D-D' (Not retrodeformable I

2000 _ Dg

5000 1500 ; Mc-ipè(?) (m) (feet)

c. Present-day cross section E-E' (Not retrodeformable

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. le because of movement in and out of plane o f cross section.)

North E' A A' v2

- ^ T r

P6(?)

because of movement ini and out of plane o f cross section.)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Tb

iTwb I Windous Bute FonnUion

v2 H Unnamed divolite

Ash flow

Tuff of Pritchards Station

Tc H C tarant Tuff

) jj . While Pine Rfngeriwclke 9C ■ Slone Cabin Formation

Ti I Intrusion

cs Currant Stock

2000 feet

609.6 km

No votical exaggo'ation

bybWtmD.WDiams, May2000

♦Unit colors on the cross sections may vary sli^tly from mit colors on map. □ Units not present on this plate.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Laketown Dolomite I Tb Basah

Windous Bute FomiUion O rdovidan

Ofh F t* Haven Dolomite Unnamed ihvoiite

EuekaQuarlzite T vl Ash flow

Antelope Valky Limestone Tuff of Pritchards Station

Ninemile Fonnation sTc^S Currant Tuff

Goodwin Foimuion jj. I White Pine Range rhyolite

Stone Cabin Fonnation

Windfall Formation Ti Intrusion

cs ■ Currant Stock Dutdoberg Shale

Lincoln Peak Fonnation

Upper Pole Caiiyon Limestone

2000 feet Pole Canvcn Limestcne 609.6 km

£|€pi Pioche Shale Ttical exaggeration

Prospect Mouitain Quartzite

undifiereitialed sed. rocks [lay vary sli^ tly from unit colors on map.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.