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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
1
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
2
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).
3
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
4
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
5
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.
6
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
7
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
8
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)
9
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
10
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.
11
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
12
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.
13
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
14
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.
15
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
16
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
17
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
18
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