UNIVERSITY OF UTAH

Geology of the Raft River Range from 2.54 Ga to present, including the

Metamorphic Core Complex and the

Associated Faulting and Detachment: Box Elder,

Utah

Mike Starkie

9th

June 2014

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Table of Contents

1. Abstract 2

2. Introduction 4

3. Geological Setting 5

4. Rock Unit Descriptions 7

a. Basement Rock: Precambrian Older Schist (pCme) 7 b. Precambrian Metamorphosed Mafic Igneous Rocks (pCme) 8 c. Precambrian Metamorphosed Trondhjemite and Metapegmatite 8

(pCme) d. Precambrian Metamorphosed Adamellite (pCme) 8

Lower Plate (Metamorphic Core, in mapped area) 9 e. Precambrian Elba Quartzite (pCeq & pCes) f. The Schist of the Upper Narrows (pCug) 10 g. Tectonic Mélange (pCtm) 12 h. Pogonip Group (Op) 13 i. Eureka Quartzite (Oe) 13 j. Fish Haven Dolomite 14 k. Chainman / Diamond Peak Formation (Mcdp) 14 l. Oquirrh Formation (Poq) 14 m. Modern Alluvium (Qal) 14

5. Depositional Environment 15

6. Structural Description and Timing Relationship 17

7. Geological history and Discussion 19

8. Conclusion 27

Acknowledgments 29 References 30 Appendix 31

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1. Abstract

The area of study is the southeast region of the Raft River Range located in Box Elder

County, Utah. The region encompasses Bald Knoll, Middle Hill, and Little Hill (Appendix: 1a, 2).

The Raft River Range contains some of the oldest rock units in Utah; approximately 2.5-2.54 Ga

(Dinter, 2014; Hintze & Kowallis, 2009). The oldest units are the Precambrian Older Schist Facies

originating from shale or mudstone, a mafic igneous facies that most likely originated from basalt, an

intrusion of trondhjemite/metapegmatite, and a metamorphosed adamellite facies (Dinter, 2014).

These make up the Basement Rocks (pCme) of the Raft Rivers Metamorphic Core Complex. The

mentioned rock facies belong to volcanic island arcs during the assembly of Laurentia, 1.5 Ga before

Rodinia assembled (Dinter, 2014). Later units of the Elba Quartzite (pCeq) and the schist facies in

the Elba Quartzite (pCes), along with the Schist of the Upper Narrows (pCug) would be later

deposited between 1,500- 800 Ma.; near the time of Rodinia. Utah from the time and separation of

Rodinia sat alongside a passive continental margin. Deposits from the end of the Proterozoic

through the Paleozoic are primarily marine deposition.

Between the end of the Precambrian and the Ordovician, are approximately ~500 Ma

missing in a major unconformity. This can be contributed to erosion and faulting forces. What is left

of the missing units comprise the Tectonic Mélange (pCtm). It is composed of the Precambrian

Schist of Stevens Springs, the Cambrian units of an unknown quartzite, possibly the Quartzite of

Clarks Basin, and the Schist of Mahogany Peaks (Dinter, 2014). The Tectonic Mélange represents

10-12 km of hanging wall of the Raft River Detachment that has eroded and transported away as the

thrust fault advanced during the Sevier Orogeny (Dinter, 2014).

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The next stratigraphic units are the Ordovician Pogonip Group (Op), which is composed of

a marbled dolomite, and a marbled limestone. This is followed by the highly brecciated Eureka

Quartzite (Oe) and the laminated marble dolomites of the Fish Have Dolomite (Ofh). Next is the

Mississippian Chainman/Diamond Peaks Formation (Mcdp). Another erosional/faulting

unconformity before the Pennsylvanian-Permian Oquirrh Formation (Poq) crops out.

The Raft River Range have under gone several metamorphic events. It began with the

Basement Rocks (pCme) being highly metamorphosed during the assembly of Laurentia. The later

Pennsylvanian Oquirrh Formation (Poq) would become metamorphosed during the compression

related to the Sevier Orogeny during the Late Cretaceous. The area of the Raft River Range at the

time of the Sevier Orogeny lay several kilometer in the curst and behind where the Sevier thrusts

broke the surface of the crust in the area known as the hinterland. At this point, the strata

composing the Raft River Range were in the ductile zone, and would be highly folded and

deformed; particularly the Elba Quartzite (pCeq, pCes).

The area of Bald Knoll and surrounding area have produced a series of thrust and normal

faults associated with the Sevier Orogeny. They are located by a repeating pattern of the Pogonip

Group (Op) thrusted over Pogonip (Op), with a sliver of the Eureka Quartzite (Oe) in-between. The

thrusting events have been dated using K-Ar dating of micas, to have occurred in the Late

Cretaceous and continuing in to the Tertiary (Bartley & Manning, 1994; Wells, Dallmeyor,

Allmendinger, 1990). The thrust faults in the studied area are believed to have been produced by a

rolling hinge. The rolling hinge theory states that slip along a high angle fault creates a series of

hanging wall blocks that deformed as a load increases on them causing the upper portion of the fault

to tilt to a shallower dip (Bartley & Manning, 1994). When the dip becomes shallow enough, a new

steeper fault forms and breaks through the hanging wall, and the cycle is then repeated as a series of

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low angle inactive faults form in front (Bartley & Manning, 1994). The thrust faults are the order of

13°-17° dip (Figure: 7.1).

The normal fault, which cuts through Bald Knoll, Middle Hill, and Little Hill, is a low angled

fault with a dip approximately 14°. It is also a result of Sevier uplifting in the region. The normal

fault resulted in a slope failure as the highlands rose. The normal fault is younger than the thrusts,

and occurred at a higher elevation. An indication of the normal fault is the younger fault,

Pennsylvanian-Permian Oquirrh Formation (Poq) is placed next to the older Eureka Quartzite (Oe),

or Pogonip Group (Op).

Basin and Range extension began approximately ~20 Ma (Hintze & Kowallis, 2009). The

extension west would cause the Raft River Range, that before laid beneath the Black Pine Range, to

rise to the surface along the Raft River Detachment taking bits of the hanging wall with it (Dinter,

2014; Wells & Allmendinger, 1990). It was during this event that the rock units would be

mylonitinized, become deformed and fractured within the brittle zone.

2. Introduction

The Raft River Range is located approximately 177 km northwest of Salt Lake City, Utah

near Park Valley in Box Elder County, Utah (Appendix 2). It is part of the Raft River Metamorphic

Core Complex which contains some of the oldest rocks in Utah; approximately 2.5-2.54 Ga (Hintze

& Kowallis, 2009; Doelling, 1980; Dinter, 2014). The formations within the mapping area

(Appendix: 1a, 2) are the Elba Quartzite (pCeq, pCes) and the Schist of the Upper Narrows (pCug),

which are Late Precambrian. There is also a Tectonic Mélange (pCtm) which is composed of the

hanging wall of the detachment that has been tectonically eroded away (~10-12 km) (Dinter, 2014).

The Mélange may contain the Precambrian Schist of Stevens Springs, an unknown quartzite which

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may be the Quartzite of Clarks Basin, and the Schist of Mahogany Peaks. The other units are the

Pogonip Group (Op), Eureka Quartzite (Oe), the Fish Haven Dolomite (Ofh), and the Oquirrh

Formation (Poq). The for-mentioned formations have undergone high grade metamorphism at least

once since their formation; twice for the Precambrian rocks. Along with these formations are lake

sediment from the Pleistocene Lake Bonneville, and other modern alluvium (Qal).

There have been several events that have had a major effect on the different lithofacies of

the Raft River Range, and adjacent mountain ranges. They are: (1) the formation and breakup of the

super continent of Rodinia, (2) the Antler Orogeny (to a lesser degree), (3) the Sevier Orogeny, and

(4) the Basin and Range Extension. Many of the units in stratigraphic succession found elsewhere in

the areas surrounding the Raft River Range are not found among those in the Raft River Range, and

those belonging to the Raft River Range have been thinned, which suggests tectonic forces

(Compton, 1975). Much of the metamorphism associated to the rock units occurred near the end of

the Miocene (Compton, 1975). The area of the Raft River Range once was an assemblage of smaller

volcanic island arc which merged together to form the continent of Laurentia (~2.5 Ga). These

formations now compose the southernmost portion of the Wyoming Shield (Hintze & Kowallis,

2009).

Our goal for this paper is to see how these events have affected the strata of the southeast

side of the Raft River Range near Bald Knoll, to determine the relationship between the formations,

if the folding and faulting was the result of brittle, or ductile deformation, and what the age and

relation the faulting of the mapped area. Tools used are the Park Valley Quadrangle Utah-Idaho 7.5

Minute Series Topographic map enlarged to a scale of 1:12,000, and the Brunton Hand Transit. A

geological map (Appendix: 1a), a cross-section (Appendix: 2), a stratigraphic column (Appendix: 2b),

and stereographics (Appendix: 4a-4c) where made to better illustrate our goal.

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3. Geologic Setting

The Basement Rock (pCme) of the metamorphic core complex are the oldest rocks of the

Raft River Range, which formed in a shallow marine sea environment, approximately 2.5-2.54 Ga.;

on a passive margin apart of the continent of Laurentia (Dinter, 2014; Hintze & Kowallis, 2009).

Nearly 1.5 Ga would pass before Laurentia and the other large continental land mass would form

the super continent of Rodinia. At this time, Utah went from being along a passive shoreline, to

deep within the continent, through to the end of Paleozoic (Blakey, 2011; Hintze & Kowallis, 2009).

Approximately ~750 Ma Rodinia began to break apart (Hintze & Kowallis, 2009). Utah for

the next ~500 Ma would once again be a passive margin of a shallow marine shelf of the North

American Plate (Hintze & Kowallis, 2009; Blakey, 2011). Sea level would rise and fall slightly, giving

change in depositional environment from off shore carbonate shelf, to beach.

Beginning in the Mississippian Period, tectonic forces began pushing east accreting island

arcs to the west of the North American Plate resulting in the creation of the Antler Orogeny (Hintze

& Kowallis, 2009). The Antler Orogeny rose to the west in present day Nevada. Deposits of fluvial

deltas can be found in the Mississippian Chainman/Diamond Peaks Formation (Mcdp). Northern

Utah would sit directly in the foredeep basin of at least two separate Orogenic events spanning for

the next several millions years.

During the Pennsylvanian and in to the Permian, Utah sat to the west of the Ancestral

Rocky Mountains , collecting large amounts of eroded sediments in the Paradox and Oquirrh Basins

(Hintze & Kowallis, 2009; Stokes, 1986). As the Ancestral Rockies rose as a result of the formation

of the super continent of Pangaea, portions of Utah subside as a result. Still at this time, Utah was

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still submerged under water along a passive shallow continental margin environment along the coast

of Pangaea.

Towards the Late Cretaceous, the area of the Raft River Range sat in the hinterland of the

thrusts accompanying the Sevier Orogeny (Wells, Dallmeyor e.t, 1990). The Sevier Highlands

pushed east compressing the land as they rose to heights along the Utah-Nevada border. Rivers

following east would deposit eroded debris of the Sevier Highlands to eastern Utah towards the

North American Western Interior Seaway (Hintze & Kowallis, 2009; Stokes, 1986).

Northern Utah began to experience volcanic activity beginning around ~40 Ma as the last of

the Farallon Plate was being subducted steeply under the North American Plate (Hintze & Kowallis,

2009). A portion of the Farallon Plate, which had been subducted, broke free in a slab pull which

resulted in a partial melt from the mantle to rise up and intrude the crust from Mid-Idaho to

Northern Utah (Hintze & Kowallis, 2009). The igneous intrusion would first enter Utah near the

Raft River Range. There is evidence of volcanic activity in flood basalt deposits. The deposits can be

seen along State Route 30 at the eastern edge of the Raft River Range between Park Valley, UT, and

Cedar Creek, UT.

Approximately ~20 Ma, the last of the Farallon became completely subducted. The Pacific

Plate then made contact with the North American Plate (Dott Jr. & Prothero, 2010). A change in

tectonic compression resulted in stress being removed against the North American Plate and the

land slowly began to extend westward. The Raft River Range sits at the north-eastern most corner of

the Basin and Range. The Raft River Range also sits obliquely to the north-south trending

mountains of the Basin and Range.

4. Rock Unit Descriptions

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a. Basement Rock (not in mapping area) Precambrian Older Schist (pCme) The Older Schist of the Raft River Range is part of the older crystalline basement of the Raft

River Metamorphic Core Complex (Figure: 4.1). Near the area of Rice and Jim Canyon on the north

side of the Raft River Range along Clear Creek Road is nearly 61 m of exposure (Compton, 1975). It

is fine-grained mica-feldspar-quartz schist (Dinter, 2014). It retains few features of its original

deposition, such as pebbles that have since been stretched in a ductile metamorphic zone deposited

in a mudstone matrix (Dinter, 2014; Compton, 1975). Total thickness of the Older Schist is between

90-300 m thick (Hintze & Kowallis, 2009).

b. Precambrian Metamorphosed Mafic Igneous Rocks (pCme)

The Metamorphosed Mafic Igneous rocks have a schistosity containing hornblende, biotite,

and amphibolite (Figure: 4.1) (Dinter, 2014; Compton, 1975). Also contained in rock is quartz,

epidote, and plagioclase (Compton, 1975). Appearance is black at a distance, sitting on top of the

Older Schist on the northeast side of the Raft River Range along Clear Creek Road (Compton,

1975).

c. Precambrian Metamorphosed Trondhjemite and Metapegmatite (pCme)

The exposure has a distinct white appearance. Out crops are gneiss made primarily of

pegmatite (Figure: 4.1) (Compton, 1975). Outcrop was approximately 4 m thick. It contains almost

no mafic minerals. It is made of quartz (10%), white micas (10%), and potassium plagioclase (80%).

The trondhjemite has been foliated, easily seen in the white mica layers. They are intrusive rocks,

and themselves intruded by dikes of Precambrian adamellite in the upper Rosevere Fork (Compton,

1975).

d. Precambrian Metamorphosed Adamellite (pCme)

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The metamorphosed adamellite (Figure: 4.1) is exposed in many of the deeper canyons

(Compton, 1975). It contains quartz, potassium plagioclase, white mica, and biotite. It has been

recrystallized into gneiss and was most likely a quartz monzonite (Compton, 1975).

[Figure 4.1: Raft River Detachment Fault with the Basement Rock (pCme). Box Elder County, Utah. (Precambrian age Older Schist (Bottom) with the Mafic Igneous Facie (dark middle), the intruded Trondhjemite/Metapegmatite facies (lighter colored middle), and the Metamorphosed Adamellite facies (near top))]

e. Lower Plate (Metamorphic Core, in mapped area) Precambrian Elba Quartzite (pCeq & pCes)

The Elba Quartzite is one of the more prominent and visible formations within the mapped

area. It is made of two portions; a white quartzite (pCeq), and darker schist (pCes) layer. Because

they are both thick distinguished features within the unit, they are mapped and described as two

units within in one formation. Between the two distinct units, total thickness in the Raft River Range

is approximately 15-450 m thick (Hintze & Kowallis, 2009) The quartzite member (pCeq) has a

weathered tan- red discolored surface, and on a fresh surfaces it is bright white (Figure: 4.2.a).

Within the quartzite member are layers of green quartzite containing the mineral fuchsite. Layers of

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muscovite schist can also be found. The quartzite member has a milky-opaque luster, fine-grained

texture and a smooth blocky appearance. The Elba Quartzite Member (pCeq) has foliated planes

and breaks near-perfectly along the foliations in blocky sheets. Also within the Elba Quartzite

(pCeq) are tan colored stretch lineation’s of sand grains stretched during ductile metamorphism. The

Elba Quartzite (pCeq) has also been fractured by high angled fractures. The Elba Quartzite (pCeq) is

observed dipping gently to the southeast at approximately 10°-25°. In some exposures outside our

mapping area, the Elba Quartzite (pCeq) has a conglomerate base which has been metamorphosed

and the pebbles have been stretched (Figure: 4.2.d). The pebbles rang in size as small as 2-3cm and

as large as + 20 cm.

The schist unit within the Elba Quartzite (pCes) is dark gray-to-green that has bands of

white quartz (Figure: 4.2.b). The banding is 1-3 cm thick. The schist unit has undergone

mylonitization. It is fine-grained schist primarily composed of quartz but also contains high amounts

of white mica, and feldspars, and lesser amounts of biotite, and other mafic minerals. The schist is

easily fractured, and breaks off in platy chunks. Within the schist unit, quartz sigma structures 5-10

cm in size show shear movement in a northeast / southwest direction. Along with sigma structures

showing a shear direction, the schist unit also contains asymmetric shear bands, mica fish structures,

and “S” & “C” textures. The asymmetric shear bands show an offset of approximately 5cm. The

asymmetric shear bands tilts in the direction of the shearing. The “S” texture dips in the opposite

direction of shearing, and the “C” texture dips in the direction of the shearing.

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f. The Schist of the Upper Narrows (pCug)

Figure 4.2.a: Elba Quartzite (pCeq), Box Elder

County, Utah. Quartzite contains stretching

lineation, foliations, and high angled fractures.

Figure 4.2.b: Elba Quartzite (pCes) schist

facies, Box Elder County, Utah. Notice

asymmetric shear bands and quartz sigma

structures.

Figure 4.2.c: Mica fish structures within the

Elba Quartzite (pCes) schist facies, Box

Elder County, Utah

Figure 4.2.d: Stretched pebble conglomerate

of the Elba Quartzite (pCes). Box Elder

County, Utah

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The Schist of the Upper Narrows is a dark brown-to-charcoal colored lithofacies. It is a fine-

grained highly siliceous rock which also contains quartz, feldspars, and biotite banding. At a closer

look, the schist also has dark and light colored banding (1-2cm). The Schist of the Upper Narrows

breaks easily along the foliations of the micaceaous mineral, which are strongly foliated. The Schist

of the Upper Narrows has also been mylonitinized.

g. Tectonic Mélange (pCtm)

The Tectonic Mélange (Figure: 4.3) is made of several units of float material left from the

remnants of the hanging wall along the detachment fault. It is an assemblage of schist, quartzite, and

gneiss. The older of the units is the Schist of Stevens Springs which is a quartz muscovite schist

containing hornblende (Dinter, 2014). The rock contains garnet and biotite porphyroblast

(Compton, 1975). There is an unknown quartzite which could possibly be that of the Quartzite of

Clarks Basin (Dinter, 2014). It is a bright white quartzite. The last is the Schist of Mahogany Peaks

which is a staurolite-garnet-biotite schist (Dinter, 2014). It has a darker color to it, ranging from a

gray-to-green hue.

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h. Pogonip Group (Op)

The Pogonip Group is made of a lower unit of marble dolomite, and an upper marble

limestone. Total exposure of outcrop is approximately 10 m on Bald Knoll. It is the second most

common unit in the mapping area only second to the Elba Quartzite (pCeq, pCes). The lower

dolomite layer (~ 5 m) is a highly fractured and weathered marbled dolomite. It is a fine-grain

textured white colored rock. There are crystals of mica within this unit; most likely form the rock

being mylonitinized.

The upper marble limestone (~ 5 m) is a light gray weathered rock. It is also been highly

fractured. The limestone unit reacts to acid much better than the dolomite unit; an easy distinction

between the units. The texture is fine-grained with subhedral crystals of mica ( > 1mm) which can

been seen under hand lens in the marble limestone unit, a result of mylonitization.

Figure 4.3: Tectonic Mélange (pCtm) of the Raft

River Detachment Fault, Box Elder County, Utah

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i. Eureka Quartzite (Oe)

The Eureka Quartzite is a bright white, highly fractured fine-grained quartzite. The Eureka

is often found near thrust sheets in small exposures that often pinch out. Crop outs are generally

small, but are as big as 3-4 m in good exposures. The Eureka is primarily quartz, with trace amounts

of mica. It is also brecciated.

j. Fish Haven Dolomite (Ofh)

The Fish Haven Dolomite is a light gray-to-silver color, highly fractured, gritty marble

dolomite. The gray Fish Haven Dolomite is laminated with white bands of calcite (1-3 cm), but it is

hard to see on the weathered surfaces. Along Bald Knoll Ridge, the exposed outcrop is

approximately 10 m thick. Fish Haven can also be found as a laminated (1-3 cm) white and tan

dolomite. Fish Haven to the touch has a much coarser feel compared to the marble dolomite of the

Pogonip Group (Op).

k. Chainman/Diamond Peak Formation (Mcdp)

The Chainman/Diamond Peak Formation is a dark charcoal colored phyllite or shale

(Dinter, 2014). It has been mircobrecciated, and is highly fractured.

l. Oquirrh Formation (Poq)

The exposure of the Oquirrh Formation along Bald Knoll is a dark charcoal-to-gray sandy

marble. It is a fine-grained rock that reacts to acid. The rock has been highly fractured. The fractures

are filled with calcite veins (~1-10 cm wide). Lower, near the southwest slope of Bald Knoll the

fractures are filled with quartz. This is since the rock would not react to acid, even on a fresh

surface.

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m. Modern Alluvium (Qal)

Active erosional processes are taking place on the southeast side of the Raft River Range.

The modern alluvium is a mixture of all the formations and units within the valley floor. These

include sand, pebbles and an assortment of unconsolidated sediments. Among the Modern Alluvium

are deposits of the Pleistocene Lake Bonneville. Some of the valley deposits are caked in a thin

calcium carbonate rich layer from the ancient lake.

5. Depositional Environment

Depositional environment is difficult to pin point since majority of the rock units have

undergone metamorphism; some formations have experienced two metamorphic events. Along with

metamorphism, many of the formations have experienced mylonitization since the original

deposition. Original textures and bedding structures have long since vanished; however, it is not

impossible to give a broad depositional environment to these formations. Many of the rock units are

exposed elsewhere with far less deformation. The metamorphic core Basement Rock (pCme) that

make up the older schist facies, mafic igneous facies, the trondhjemite metapegmatite facies, and the

metamorphosed adamellite facies were all deposited before the creation or during the creation of

major land masses 2.5-2.54 Ga (Hintze & Kowallis, 2009; Dinter, 2014). They were deposited in a

relatively shallow marine shelf along a passive margin. The volcanic arcs would explain the igneous

units and Older Schist containing pebbles, and cobbles with a mudstone matrix most likely derived

from shale (Compton, 1975).

For the rest of the Proterozoic and Paleozoic periods, Utah sat at the margin of shallow

epeiric sea. The Elba Quartzite (pCeq & pCes), Schist of the Upper Narrows (pCug), Pogonip

Group (Op), Eureka Quartzite (Oe), Fish Haven Dolomite (Ofh), Chainman/Diamond Peak

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Formation (Mcdp), and Oquirrh Formation (Poq) all represent depositions within a marine

environment; ranging from marine shelf to near beach marine environments.

The Elba Quartzite (pCeq, pCes) is a thick unit which shows a variety of marine

environments. Near its base, it contains the stretch pebble conglomerate which may have been

deposited in a higher energy environment such a marine shelf. Farther up the unit, the Elba

Quartzite becomes dominantly quartz with other minerals such as mica, and plagioclase. These may

have at one point been sandy beaches on the margin of a sea, or a near shore surface. Within the

Elba are darker schist. These most likely were deposits of shale, or mudstone. This is significant in

the sense that this shows a change in energy and a rise in sea level. These metamorphosed

shale/schist units are then preceded by the quartzite unit; once again a change in energy and level of

sea water.

The Schist of the Upper Narrows (pCug) is dark siliceous schist containing mica and

feldspars. It was most likely derived from shale, or a mudstone rich in silica and quartz. Similarly to

the schist of the Elba Quartzite (pCes), the Schist of the Upper Narrows was deposited in a shallow,

low energy marine environment along shore of the continental shelf of Laurentia.

An unconformity representing a span of approximately 500 Ma of lithofacies is missing from

the end of the Precambrian to the Ordovician. It was most likely eroded during one of the orogenic

events experienced in this area. The Pogonip Group (Op) which is the older of the Ordovician units

is made up of a marbled dolomite and limestone. These could have only been deposited in shallow,

warm, calcium rich waters most likely on a carbonate shelf off shore. The Eureka Quartzite (Oe)

indicates sea level regression because the Eureka is made of quarts grains. The Eureka Quartzite is

most likely that of a beach or sandy near shore marine environment, compared to the carbonate

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shelf environment of the Pogonip. Without bedding structure, or fossils, it is difficult to pin point an

exact location for the Eureka Quartzite. The Fish Haven Dolomite (Ofh) is an indication the warm

shallow water returned once again. This warm shallow calcium rich water would last through the

Mississippian Chainman/Diamond Peak Formation (Mcdp) which is derived from shale, and lasting

through the Pennsylvanian-Permian Oquirrh Formation (Poq) which is a sandy limestone. Both

being depositing in deeper water; the Oquirrh Formation was warm shallow marine shelf, the

Chainman/Diamond Peak Formation being on the continental shelf.

6. Structural Description and Timing Relationship

The Bald Knoll region of the Raft River Range is structurally complex with both normal and

thrust faults. Across Little Hill are three thrust faults with similar orientation and dips (between 13°-

17°) (Appendix: 1a; Appendix: 5). They were difficult to find. A small sliver of Eureka Quartzite

(Oe) separated Pogonip (Op) thrusted over Pogonip (Op); repeated over three thrusting events. A

similar thrust fault is found cross-cutting Bald Knoll and Middle Hill. The thrust becomes lost under

the alluvium of Cove Canyon, but it is believed to continue to all or at least one of the thrust faults

on Little Hill.

The normal fault that cuts across Bald Knoll, Middle Hill, and Little Hill is a similar age to

the thrust faults on Little Hill. The orientation of the normal fault is difficult because of its

curvature. Its dip is approximately 15° found through a three-point problem (Appendix: 5). This dip

is comparatively low to typical normal faults which tend to dip on the order of 60°, making it a low

angle normal fault. The curve of the fault is a result of its low angle. It was difficult to trace in the

field. Following the contact between the Eureka Quartzite (Oe) and the Oquirrh Formation (Poq)

was easier do to due to its contrasting differences is appearance, versus the contact between the

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Pogonip Group (Op) and the Oquirrh Formation (Poq), which tended to have a similar appearance.

The distinguished feature to look for between the Pogonip Group limestone and dolomite and the

Oquirrh Formation silty limestone, is the Oquirrh has been highly fracture by faulting, and

subsequently filled with both calcite and quartz veins. Offset of the normal fault is difficult to

determine; however the placement of the Oquirrh Formation against Ordovician rocks led to the

assumption that several hundred meters to several kilometers have been faulted out.

Ductile deformation occurred in the Elba Quartzite (pCeq, pCes). In the area termed the

“highlands” along the cliff faces of Quaking Aspen Canyon, and Little Rocky Canyon are noticeable

“M” folds of an overturned anticline that have been horizontally overturned within the Elba

Quartzite (pCeq, pCes) (Figure: 6.1 ). These have been mapped on Appendix: 1 by sitting on the

opposite side of the canyon to the fold at approximately the same elevation. Using topographic

features seen in the field and on the map such as drainages, and cliff faces, we are able to

approximate the location and shape of the folds on the geological map in Appendix: 1. Using this

relationship we are also able to reconstruct a cross-section (Appendix: 2a) to show how this might

look, and the relationship of the Schist of the Upper Narrows (pCug) being both on top and below

the Elba Quartzite (pCeq, pCes). Where the Schist of the Upper Narrows sits below the Elba

Quartzite (pCeq, pCes) and contacts the Tectonic Mélange (pCtm) is where the Raft River

Detachment Fault sits. This marks the exposed contact where the hanging wall would have been in

contact with the footwall, but has since been faulted away.

19

After a later mylonitization, the Elba Quartzite (pCeq, pCes) has been deformed and

fractured in the brittle zone. In the schist facies of the Elba Quartzite (pCes), micro fractures have

formed. These microfaults indicate a shear direction opposite to the dip of the microfault. The

microfaults have an offset of approximately 5 cm. Along with the micro faults, at this time the Elba

Quartzite (pCes) had been fractured by high angled fractures. These fractures are between 65°-90°

striking northwest-southeast. Many of the other units have also become highly fractured and some

even brecciated approximately the same time as the Elba Quartzite (pCes).

7. Geological History and Discussion

Figure 6.1: “M” Fold in the Elba

Quartzite (pCeq, pCes). Picture is taken

from the northeast side of Quaking Aspen

Canyon towards the southwest. Box Elder

County, Utah

20

2.5 Ga. is approximately the age of the oldest rocks in Utah, which are found in the Raft

River Range near the Utah-Idaho border (Hintze & Kowallis, 2009; Compton, 1975). The rocks

were once part of a passive margin along a volcanic island arc system. They contain deposits of a

shallow marine shelf environment which makes up the Precambrian Older Schist Facies, the

intrusion of the mafic igneous facies, and trondhjemite and metapegmatite facies, and the

metamorphosed adamellite facies. The smaller island arcs began to assemble into larger and more

stable land masses. They compose a portion of the Wyoming Shield and were once part of the

continent of Laurentia (~3.4-2.5 Ga), which caused these facies to be metamorphosed at high grades

due to compressional forces during its assembly (Hintze & Kowallis, 2009). Over the next 1.0-1.5

Ga., erosional forces prevailed as uplift continued as Laurentia formed (Dinter, 2014). Laurentia

would eventually assemble with the other continental landforms to form the super continent of

Rodinia approximately 1.0-1.2 G.A. (Dott Jr. & Prothero, 2010; Dinter, 2014). About 750 Ma

Rodinia began to break apart (Dott Jr. & Prothero, 2010; Blakey, 2011; Hintze & Kowallis, 2009).

Northwestern Utah would lie at the hinge line of the passive continental margin on Laurentia as

Australia and Antarctica moved away (Blakey, 2011; Dott Jr. & Prothero, 2010; Hintze & Kowallis,

2009; Dinter, 2014).

For the next ~500-550 Ma, from the end of the Proterozoic to the end of the

Paleozoic, the western margin of North America, including the area of what is now the Raft River

Range, would be shallow epeiric seas on a shallow marine carbonate shelf (Blakey, 2011; Hintze &

Kowallis, 2009; Dott Jr. & Prothero, 2010). The depositions would be that of sandstone, shale,

limestone, and dolomites. These would include the deposition of the Precambrian Elba Quartzite

(pCeq, pCes), which also includes a fine-grained schist member, and the Schist of the Upper

Narrow, along with the Ordovician deposits of the Pogonip Group (Op), Eureka Quartzite (Oe),

21

Fish Haven (Ofh), and the Pennsylvanian-Permian deposits of the Oquirrh Formation (Poq). This

was a productive marine environment.

Between the Precambrian Schist of the Upper Narrows and the Ordovician Pogonip Group,

the strata have been eroded / faulted away. Remnants remain in the Tectonic Mélange. The

Tectonic Mélange is the 10 to 12 km of the hanging wall that was faulted out and eroded away above

the Raft River Detachment (Dinter, 2014). The mélange is composed of the Schist of Stevens

Springs, an unknown quartzite that is possibly the Quartzite of Clarks Basin, and the Schist of

Mahogany Peaks (Dinter, 2014). The mélange is the representation of the unconformity caused by

Sevier Orogenic thrusting which began in the Late Cretaceous. This date is confirmed by using

minerals left in the hanging wall by K-Ar dating (Bartley & Manning, 1994).

The Ordovician was much like that of modern day Florida (Hintze & Kowallis, 2009). The

Pogonip Group (Op) which is at its thickest (~1066 m) around Delta, Utah contains large amounts

of fossils such as trilobites, graptolites, condonts, cephalopods, brachiopods and echinoderms

(Hintze & Kowallis, 2009). The Eureka Quartzite (Oe) shows a regression in the marine waters to

the west (Hintze & Kowallis, 2009). The waters would later rise again with the deposition of the Fish

Haven Dolomite (Ofh), the most widespread Ordovician rock unit in Utah which contains fossils of

corals and brachiopods (Hintze & Kowallis, 2009). Total thickness of Ordovician strata near the

Raft River Range is approximately 335 m (Hintze & Kowallis, 2009).

During the Late Devonian and into Early Mississippian a possible volcanic arc collided along

the west coast of the North American Plate which formed the Antler Orogeny (Dott Jr. & Prothero,

2010). The Antler Orogeny took place mostly in present day Nevada; however, evidence of this

orogenic event are found in the Raft River Range from detritus that where shed off from rivers of

22

the Antler Highlands to the west, deposited in the Chainman/Diamond Peaks Formation (Mcdp)

located in the foredeep basin, to the east in present day Utah. The Chainman /Diamond Peak

Formation is a dark phyllite (Dott Jr. & Prothero, 2010; Dinter, 2014; Hintze & Kowallis, 2009;

Stokes, 1986). Shallow carbonate water would last in the area through to the Permian (Blakey, 2011;

Hintze & Kowallis, 2009)

By the Pennsylvanian Period, the Ancestral Rocky Mountains began to form in present day

Colorado (Stokes, 1986). They consisted of two main ranges called the Uncompahgre and the Front

Range (Hintze & Kowallis, 2009; Stokes, 1986). They formed as the continents of Laurentia and

Gondwanaland merged together near present day Texas (Hintze & Kowallis, 2009) As a result of

this orogenic event, the Paradox Basin and the Oquirrh Basin form to the west of the Ancestral

Rockies. The Oquirrh Basin is located from mid-western Utah and continues north into Idaho

(Stokes, 1986; Hintze & Kowallis, 2009) Subsidence began in the Late Mississippian and reached it

max depositional rate in the Pennsylvanian, and continued into the Permian (Stokes, 1986; Hintze &

Kowallis, 2009). The deposition accumulation into the Oquirrh Basin was on the order of 6,100 m

to as much as 9,100 m of marine sediments, primarily limestone’s (Stokes, 1986; Hintze & Kowallis,

2009; Dinter, 2014). 6- 9 km of sediments make up the Oquirrh Formation (Poq), which is seen in

the Raft River Rage; however, there is only on the order of 300 m of the Oquirrh Formation

deposited near the Raft River Range (Hintze & Kowallis, 2009) . Reason as to why there was such an

accumulation of sediments in the Oquirrh Basin is still unclear (Hintze & Kowallis, 2009; Stokes,

1986; Dinter, 2014).

During the Mesozoic Period, the epeiric seas left the western portion of Utah. Tectonic

forces to the west began to uplift the land as the Farallon Plate was being steeply subducted

underneath the North American Plate (Hintze & Kowallis, 2009). Rocks deposited during the

23

Mesozoic are not found in the mapped area of the Raft River Range. They were most like eroded

away during Sevier uplifting during the Late Cretaceous, or before. The Sevier Orogeny would

migrate eastward from the Utah-Nevada border from Mexico to Alaska between 100 – 80 Ma

(Fillmore, 2011: Stokes, 1986: Wells, Dallmeyor, & Allmendinger, 1990). The fold and thrust formed

as the western North American Plate experienced compression as the Farallon Plate continued to be

subducted. The Sevier Orogeny pushed tens of kilometers eastward, shortening the western North

American Plate as much as 100 km (Fillmore, 2011). The North American Western Interior Seaway

sat to the east of the Sevier Highlands, where much of the detritus was eroded into (Fillmore, 2011;

Hintze & Kowallis, 2009). The area of the Raft River Range sat in the hinterland of the Sevier

thrusting. Regional thrusting continued from Late Cretaceous into the Miocene (Covington, 1983:

Wells & Allmendinger, 1990). Late Cretaceous thrusting was associated with low angled faulting,

which caused much of the strata to be metamorphosed, in a first of two events; the other would

occur in the Tertiary (Wells, Dallmeyor, & Allmendinger. 1990).

The Sevier Orogeny had drastically shaped the land that is now exposed in the Raft River

Range. At the beginning of the Sevier thrusting the strata now exposed laid several kilometers

beneath the earth’s surface and behind where the thrust broke to the surface in what is known as the

hinterland. The thrusting of the Sevier Orogeny caused shearing in the brittle/ductile zone. While

the Elba Quartzite (pCeq, pCes) was still in the ductile zone, thrusting during the Sevier Orogeny

caused the Ebla Quartzite to fold on to itself multiple times in “M” folds of a horizontally

overturned anticline, which can be seen on the cliff walls of Quaking Aspen Canyon, and Little

Rocky Canyon (Figure: 6.1). It was this folding which allowed the Schist of the Upper Narrows

(pCug) , which is stratigraphically deposited on top of the Elba Quartzite (pCeq, pCes) to also

appear under it as well (Appendix: 2a). Within the mapped area around Little Hill, Middle Hill, and

24

Bald Knoll are faults associated with this thrusting event. Little Hill has three thrusts that have been

mapped. They are all approximately the same orientation, spaced at almost even intervals, and have

dips between 13°-17° (Appendix: 1a, Appendix5). These faults are thought to be associated with the

rolling hinge theory. The rolling hinge theory states that slip along a high angle fault creates a series

of hanging wall blocks that deform as a load increases on them causing the upper portion of the

fault to tilt to a shallower dip (Bartley & Manning, 1994). When the dip becomes shallow enough, a

new stepper fault forms and breaks through the hanging wall, and the cycle is then repeated as a

series of low angle inactive faults form in front (Figure: 7.1) (Bartley & Manning, 1994).

The rolling hinge theory would explain the three thrust faults of Little Hill. They are

systematically stacked on each other in a repeating sequence of the Pogonip Group (Op) deposited

on top of the Eureka Quartzite (Oe) which has been thrusted back on top of the Pogonip Group.

The thrust fault on Bald Knoll crosses across Middle Hill, and is also believed to be a continuation

Figure 7.1: From “Postmylonitic

Deformation in the Raft River

Metamorphic Core Complex,

Northwestern Utah: Evidence of a

Rolling Hinge” (Bartley & Manning,

1994).

25

of one of the faults of Little Hill (it is lost under the alluvium in the valley so to which fault it is

associated with in unknown), and a result of the rolling hinge theory.

There is a low angle normal fault which cuts through Bald Knoll, Middle Hill, and Little Hill.

It is possibly a reactivation of an inactive thrust fault block from the rolling hinge. The Raft River

Range contains numerous low angle normal faults which dip east northeast (Wells, & Allmendinger,

1990). These low angle normal faults are associated with slope failure during the Sevier Orogeny and

occurred much later then the Sevier thrusting. The slopes faulted would have been at higher

elevations. The strata, which would have been deposited above the Pennsylvanian-Permian Oquirrh

Formation (Poq) faulted/eroded away. The Oquirrh Formation has dropped down to the

Ordovician Eureka Quartzite (Oe). The normal fault caused brittle fracturing of the associated

strata. The Oquirrh Formation fractures filled with calcite and quartz is also associated with the

Sevier normal faulting.

During the Oligocene, western Utah saw a period of intense volcanism. Igneous activity

moved into northern Utah approximately 40 Ma (Hintze & Kowallis, 2009). The subduction of the

Farallon Plate continued into the Miocene. It was being subducted eastward but at an oblique angle.

After which, the plate broke free in a slab pull which released melted mantle farther into the

continental plat away from the subduction zone (Hintze & Kowallis, 2009).

About 20 Ma, the last of the Farallon became fully subducted and the Pacific Plate made

contact with the North American Plate (Dott Jr. & Prothero, 2010). The change in tectonic

compression resulted in stress being removed against the North American Plate and the land slowly

began to extend westward. The resulting movement created a series of normal fault block mountains

with down-dropped grabens or basins in between, along with a multitude of normal faults that strike

26

approximately north to south (Dott Jr. & Prothero, 2010); this area known as the Basin and Range

Providence. It is bounded by the Cascade Mountains in the north to the northwest desert of Mexico

in the south and from the Sierra Nevada Mountains in the west, to the Wasatch Line in the east. The

extension westward thinned the crust as much as 100 % of its original thickness (Hintze & Kowallis,

2009). The normal faulting of the Basin and Range Extension exposed the strata of the Raft River

Range. Most of the metamorphic change of the rocks occurred during the Oligocene in to the

Miocene within the Raft River Detachment. The rock that had once been deeply buried within the

brittle/ductile zone now had been exposed, but not after heating caused by igneous intrusions in the

Oligocene, and normal faulting (which continues to present day) which started in the Miocene.

The second metamorphic event mentioned is the mylonitization of the Elba Quartzite

(pCeq, pCes) through to the Eureka Quartzite (Oe) which started in the Miocene and associated

with the Basin and Range extension starting about 20 Ma (Hintze & Kowallis, 2009). The Raft River

Range rose up from underneath the Black Pine Range, which are approximately 10 km north east of

the Raft River Range in the Sawtooth National Forest, Idaho (Wells & Allmendinger, 1990). The

Raft River Range rose up along the Raft River Detachment Fault taking bits of the hanging wall with

it. The Basin and Range extension brought the Raft River Range to the surface.

The Elba Quartzite (pCeq, pCes) was deformed during the Basin and Range extension and

up lift of the Raft River Range. Within the darker schist of the Elba Quartzite (pCes) are several

features that formed as a result of sheering. Mica fish (Figure: 4.2.c) which flow with the direction

of shearing, micro faulting which dip away from the shear direction, and “S” bands which dip

opposite to shearing, and “C” bands which dip towards shearing. Also within the schist facies are

multiple microfaults which dip towards the sheer direction. It was at this time that the Elba

Quartzite (pCeq, pCes) was foliated, and the stretching lineation’s formed. The foliations and

27

stretching lineation’s, within the Elba Quartzite (pCeq), formed parallel to the direction of sheering.

Appendix’s 4a through Appendix 4c are stereographics which group the lineation, foliations, and

fractures together to show grouping and trend of shearing. General shearing direction, as indicated

by Appendix 4a and Appendix 4b, to be in a south, southeast direction. Since Basin and Range

extension, not much else has occurred, other than active erosional force.

There is active alluvium being deposited along the slopes of the Raft River Range. Erosion

forces are constantly at work. Among some of the deposits of unconsolidated active alluvium are

deposits from the Pleistocene Lake Bonneville. The Raft River Range run east west near the

northwest shores of the remnant of Lake Bonneville, the Great Salt Lake (~35 km (Google Earth,

2013)). 20,000 to 10,000 years ago the climate was much cooler ( Utah Geological Survey, 1996).

Lake Bonneville covered much of the western portion of Utah from the Idaho bordered down to

central Utah. At its maximum, the lake was 20,000 mi2 and just over 300 m deep (Hintze &

Kowallis, 2009). Lake Bonneville formed approximately 26,000 years ago and rose to its maximum

approximately 15,000 years ago, with its decline by 10,000 years ago (Hintze & Kowallis, 2009).

Glaciers and rivers feed into Lake Bonneville from the surrounding canyons.

8. Conclusions

The area of the Raft River Mountains has a complex history which began nearly 2.5-2.54

Ga (Dinter, 2014; Hintze & Kowallis, 2009). The Raft River Range are composed of a metamorphic

core made of Precambrian schist, gneiss and, igneous intrusions. Following the assembly of the

continent of Laurentia and the breakup of the super continent of Rodinia, the area of the Raft River

Range lay along a passive continental margin for approximately 500-550 Ma (Hintze & Kowallis,

2009; Blakey, 2011). Depositions of marine sediments are dominant during this time. The

28

Precambrian Elba Quartzite and Schist of the Upper Narrows, the Ordovician age Pogonip Group,

Eureka Quartzite, Fish Haven Dolomite, the Mississippian Chainman/Diamond Peak Formation,

and the Pennsylvanian-Permian Oquirrh Formation were all deposited during this time, and in this

passive continental margin environment.

The main structural story of the Raft River Range, and particularly the mapped area, is that

of the Sevier Orogeny. The Raft River Range at this time sat several kilometers below the curst in

the hinterland of the Orogeny in the ductile zone. At this time the rocks, particularly the Elba

Quartzite (pCeq, pCes), was ductility folded. The mapped area contains several thrust faults, which

are believed to have been the result of a rolling hinge (Bartley & Manning, 1994). There is also a low

angle normal fault in the mapped area that dates to the Sevier Orogeny. It was a result of slope

failure caused by the highlands rising to great heights (Dinter, 2014).

After Sevier thrusting, plate dynamics changed to the west approximately 20 Ma resulting

in the Basin and Range Providence formation (Hintze & Kowallis, 2009; Stokes, 1986). It was during

the Basin and Range Extension that the Raft River Range was exhumed from under the Black Pine

Range in Idaho along the Raft River detachment Fault along the Eureka Quartzite Member (Oe).

Majority of the formations, during this time, experienced mylonitization. 10-12 km of the hanging

wall were faulted away (Dinter, 2014). Only small bits of the hanging wall remain along the

detachment.

29

Acknowledgments

I would like to personally thank the following people for their help in gathering information for this

report and for gathering information out in the field.

Dr. David Dinter and field camp managers Mallory Millington and Amy Steimke

I would like to thank for the help I received from my field Partners Jon Peterson and Taylor

Witcher, along with the help from Heather Judd, Taylor Wessman, David Christiansen, Robyn

Lyons, Tanner Morrill, Zach Stelby, Josh Johnston.

I would also like to thank TA Jelle Wiersrma for his help during field methods and both field camp

trips. He was extremely patient and helpful with explaining everything. I don’t think I would have

done nearly as good in either class without his help and direction. THANK YOU!

30

References

[1] Bartley, J. M., & Manning, A. H. (1994). Postmylonitic Deformation in the Raft River Metamorphic Core

Complex, Northwestern Utah: Evidence of a Rolling Hinge. University of Utah, Department if Geology and

Geophysics. University of Utah.

[2] Blakey, R. (2011, march). Library of Paleogeography. Retrieved February 5, 2014, from Colorado

Plateau Geosystems, Inc.: cpgeosystems.com/paleomaps.html

[3] Compton, R. R. (1975). Geological Map of the Park Valley Quadrangle, Box Elder County, Utah, and

Cassia County, Idaho. Salt Lake City: U.S. Geological Survey.

[4] Covington, H. (1983). Structural Evolution of the Rat River Basin, Idaho. Geoligical Society of

America.

[5] Dinter, D. (2014, June 2). Geology of the Raft River Metamorphic Core Complex, Ut. Salt Lake

City, Ut.

[6] Doelling, H. H. (1980). Geology and Mineral Resources of Box Elder County, Utah. Salt Lake City: Utah

Department of Natural Resources.

[7] Dott Jr., R. H., & Prothero, D. R. (2010). Evolution of the Earth (Vol. 8th). New York: McGeaw

Hill.

[8] Fillmore, R. (2011). Geological Evolution of the Colorado plateau of Eastern Utah and Western Colorado.

Salt Lake City: The University of Utah Press.

[9] Google Earth. (2013, October 7). Retrieved February 5, 2014, from Google Earth:

www.googleearth.com

[10] Hintze, L. F., & Kowallis, B. J. (2009). A Field Guide to Utah's Rocks: Geologic History of Utah.

Provo: Brigham Young University.

[11] Stokes, W. L. (1986). Geology of Utah. Salt Lake City: Utah Museum of Natural History,

University of Utah.

[12] Utah Geological Survey. (1996). The Wasatch Fault. Salt Lake City: Department of Natural

resources.

[13] Wells, M. L., & Allmendinger, R. W. (1990). An Early History of Pure Shear in the Upper Plate of the

Raft River Metamorphic Core Complex: Black Pine Mountains, Southern Idaho. Cornell University. Ithica:

Institute for Study of the Continents & Department of Geological Sciences.

[14] Wells, M. L., Dallmeyor, R. D., & Allmendinger, R. W. (1990). Late Cretaceous Extension in the

Hinterland of the Sevier Thrust Belt, Northwestern Utah & Southern Idaho. Geology .

31

32

Appendix 1a: Geological map of the

Bald Knoll Region of the Raft River

Range, near Park Valley, in Box

Elder County, UT. Original map

used was the Park Valley Quadrangle

15 Minute Topographic map that

was enlarged to 1:12,000. It has since

been modified to fit within this

reports format.

(Pages 31-32; Key is located on page

33)

33

Appendix 1b: Rift River Mountain, Box Elder County, Utah Map and Cross-Section Legend

Formations

Structures

Quaternary

Thrust Fault

(Thrust Direction)

Qal Modern Alluvium

Normal Fault

(Drop Down Direction)

Pennsylvanian-Permian

Detachment

Poq Oquirrh Formation

Inferred Fault

Mississippian

Fold Axis

Mcdp Chainman/Diamond

Hinge Axis

Peak Formation

"M" Fold

Ordovician

Strike and Dip

Ofh Fish Haven Dolomite

20 of Foliation

Oe Eureka Quartzite

1 20

Triplet measurement

Op Pogonip Group

Footwall Thrusting

Precambrian

Footwall Dropping

pCtm Tectonic Mélange

Bedding Direction

Metamorphic Core

Bedding Contact

pCug

N Cardinal Direction

Elba Quartzite

pCeq Quartzite Member

pCes Schist Member

pCme Basement Rock

34

Appendix 2a: Cross-section line A’,

B’, C’ through Bald Knoll in the

Raft River Range, near Park Valley,

Box Elder County, UT.

(See Appendix 2c for legend)

35

36

Appendix 2b: Stratigraphic column of the Raft River lithofacies near Bald Knoll, Box Elder County,

UT. (Pages 35-36: See Appendix 2c for legend)

37

Appendix 2c: Legend for cross section (page 34), and stratigraphic column (page 35-36)

Marble limestone /

Dolomite

Calcite / Quartz Fill

Schist / Schistosity

. . . . . . . . . . . . . . . . . . . . . . . . . .

Quartzite

Crystalline

Pegmatite

Stretched Pebbles

unconformity Indicator

38

Appendix 3: Location of Raft River Mountain, Box Elder County, Utah (Google Earth, 2013)

N

39

Appendix 4a: Stereographic of stretching lineation’s mapped in the Precambrian Elba Quartzite

(pCeq), Bald Knoll Region, Raft River Range, UT. Major fold axis plotted in hot pink.

40

Appendix 4b: Stereographic with poles of foliation measurements taken in the Precambrian Elba

Quartzite (pCeq), Bald Knoll Region, Raft River Range, UT. The detachment pole is indicated in hot

pink.

41

Appendix4 c: Stereographic of strike and dip of fractures mapped in the Precambrian Elba

Quartzite, Bald Knoll Region, Raft River Range, UT. Major fold axis plotted in hot pink.

42

Appendix 5: Triplet measurements taken from the field along the Raft River Detachment on the east side of the Raft River Mountains, Box Elder County, Utah

Number Foliation Lineation Fracture

(Strike, Dip) (Trend, Plunge (Strike, Dip)

1 075, 21 02, 251 028, 63

2 160, 08 03, 250 142, 58

3 094, 25 02, 080 168, 76

4 040, 19 04, 262 200, 068

5 070, 18 02, 075 144, 22

6 037, 35 018, 085 171, 60

7 074, 9 04, 079 182, 78

8 080, 26 04, 089 022, 64

9 060, 24 010, 081 172, 90

10 081, 21 01, 082 175, 082

11 044, 29 08, 054 342, 89

12 085, 19 06, 085 350, 80

13 060, 15 04, 080 345, 75

14 060, 21 013, 071 348, 75

15 078, 15 03, 067 05,82

16 089, 14 03, 072 347, 41

17 057, 20 011, 261 079, 84

18 057, 20 011, 261 079, 084

19 069, 19 05, 259 070, 026

20 045, 22 06, 73 01, 88

21 089, 19 011, 079 170, 75

22 041, 16 011, 071 02, 70

23 074, 35 06, 079 175, 76

24 065, 31 010, 077 159, 59

25 060, 33 08, 082 348, 79

26 077, 35 02, 072 04, 81

27 076, 15 003, 085 354, 68

28 116, 23 016, 269 003, 80

29 084, 14 06, 089 176, 82

30 108, 12 04, 110 189, 84

31 266, 09 06, 267 181, 90

32 090, 14 04, 266 129, 43

33 085, 16 02, 270 189, 77

34 064, 22 03, 081 184, 78

35 104, 20 07, 270 354, 56

43

36 111, 23 06, 070 349, 64

37 074, 20 01, 085 176, 53

38 066, 26 01, 72 02, 85

39 079, 29 03, 80 332, 79

40 074, 24 04, 076 01, 076

41 104, 20 07, 270 354, 56

42 110, 30 03, 260 345, 45

43 074, 20 01, 085 345, 81

44 069, 33 011, 079 176, 52

45 066, 26 01, 072 02, 85

46 059, 20 01, 065 350, 80

47 055, 30 01, 250 170, 70

48 062, 20 011, 72 172, 72

49 076, 28 05, 077 351, 79

50 145, 5 04, 253 017, 79

44

Appendix 6: Three point problems in order to find the dip of each thrust fault, the low-angle

normal fault, and the detachment fault.

{{Tan Ѳ = [

] Ѳ = Tan-1 [

]}}

Little Hill Thrust Faults Upper Thrust D = 900 ft., H1=6580 ft., H2= 6300 ft., ΔH= 250 ft.

Ѳ = 17.28° 17° Mid- Thrust D = 700 ft., H1= 6500 ft., H2= 6300 ft., ΔH= 200 ft.

Ѳ = 15.9 16° Lower Thrust D = 700 ft., H1=6460 ft., H2=6300 ft., ΔH= 160 ft.

Ѳ = 12.87° 13°

Middle Hill/Bald Knoll Thrust Fault D = 1300 ft., H1=7260 ft., H2=7000 ft., ΔH= 260 ft.

Ѳ = 11.3° 11° Low Angle Normal Fault D = 400 ft., H1=6400 ft., H2=6300 ft., ΔH= 100 ft.

Ѳ = 14° Detachment Fault D = 900 ft., H1=6500 ft., H2=6400 ft., ΔH= 00 ft.

Ѳ = 6.3° 6°

H1 D

ΔH= H1-H2

H2

Ѳ