Geologic History of the San Rafael Swell

(Figure 1) East-facing limb of the San Rafael Swell (Mullins, 2019).

This report analyzes a geologic feature known as the San Rafael Swell located in eastern central Utah in order to describe and comprehend the complex geologic and stratigraphic history of the field area. To accomplish these tasks an in-depth geologic history of the central Utah region was synthesized from various published and online resources, a stratigraphic column and corresponding description of major rock units that comprise the feature was developed, and field interpretations were made using the Google Earth program. Results of these efforts indicated that the San Rafael Swell structure is a large, dome-shaped anticline formed by the Laramide Orogeny which faulted underlying basement rock about 60 million years ago. Additionally, the development of the ancient Rocky Mountains and the evolution of depositional environments from the early Permian to the Neogene are evident in the rock units studied in the area of interest. The constructed cross-section which encompasses the eastern-most piece of the San Rafael Swell effectively demonstrates the original shape of the parallel-bedded anticline structure and highlights the erosion that has removed significant portions of the younger rock units, exposing older units that reside in the center of the anticline. Also apparent is the inconsistent limb steepness from east to west, as the eastern limb folds at a far greater angle than the western limb. This report emphasizes the unique identifying characteristics of the San Rafael rock units and the geologic history of the region responsible for their development.

Throughout the semester of DePauw University’s 2020 Geologic Field Experiences course students focused on developing skills and acquiring knowledge that would be utilized on a Spring Break trip to Utah in order to study the San Rafael Swell field area in person. During the trip itself students were to make observations of key rock units in the field, including recognizing and interpreting individual units, structures within those units, among others. Basic measurements such as strike, dip, and geologic field data were to be recorded in anticipation for later geologic map and cross section construction. In turn, these created resources in addition to literature research would be the basis for interpretation of the San Rafael Swell structure itself. Unfortunately, due to the COVID-19 pandemic this planned field trip was cancelled, resulting in a shift in the class’ approach to studying the area of interest. Rather than observing rock units in the field, descriptions of rocks were compiled from the study of available hand specimens and synthesis of literature research. Depositional environment interpretations of individual rock units were made on the basis of this research. Additional synthesis of literature research was done to produce a general geologic and tectonic history for the central Utah area. Also, mapping and cross-section work of the region was accomplished utilizing photographic resources on the computer in the Google Earth program, and crafting said maps in the Adobe Illustrator program. The construction of these literature syntheses and photograph-based maps was the basis of the interpretations and results that this report addresses.

The regional geologic setting of the Colorado Plateau is focused upon in this report. The region is largely dominated by a present-day desert, and it is centered on the Four Corners region of the United States (Figure 2). The Colorado River and its major tributaries also make up a significant area of the Colorado Plateau. The San Rafael Swell can be found in the northern section of the Colorado Plateau, in eastern central Utah. This specific area of the region is of most interest in this report, as its primary goals are to describe and provide interpretation for the geologic history of the San Rafael Swell. The area of interest, in addition to the area utilized to create geologic maps and cross section are highlighted below (Figure 3).

The Precambrian eon is responsible for the origin of the basement of the San Rafael Swell area. From 1.8 to 1.6 billion years ago material collided and attached itself to a newly-formed continent that pre-dates North America (Utah Geological Survey, n.d.). These collisions were the driving force behind the creation of granitic and metamorphic rocks during this time as the tectonic activity produced ideal conditions of pressure and temperature to cause the rock to metamorphose. About 1.4 billion years ago, magmatism of granitic substances and reactivation of faults occurred, causing the accrual of new rock (Karlstrom and Humpherys, 1998). More recently, in the Proterozoic Era, the accretion of various sediments produced thick layers of sedimentary rock, including glacial till (Hintze, 1973).

The important major formations of rock considered in this geologic history were deposited beginning in the Permian Period. At this time, about 270 million years ago, the continents of South America and Africa collided with the North American continent as the Supercontinent Pangaea was formed (National Park Service, n.d.). This major collision caused the development of the Appalachian Orogeny in the central eastern United States and the development of the Ouachita Orogeny in the central southern United States. Tectonic activity was common which created areas of high elevation and low elevation, especially along faults. One such area of elevation was within the Paradox Basin, which allowed the basin to occasionally become restricted, similar to the current day Mediterranean Sea (Geos 220, 3/11/2020). Evidence of the Paradox restricted basin can be found in Permian evaporite deposits that formed as a result of the water held in the basin drying up over time. The Cutler Group is the primary formation of rock associated with the early Permian time period (Sprinkel et al., 2003). 

The late Permian is regarded as distinct from the early Permian due to the development of the Kaibab Sea throughout a large portion of present-day central and western Utah (Geos 220, 3/11/2020). A large area of coastal dunes developed along the edge of the shallow inland Kaibab Sea, which is presented as the White Rim Sandstone member of the Cutler Group (Sprinkel et al., 2003). The shoreline of the Kaibab Sea prograded to the east over time, which created a layer of beach deposits overlying the dune deposits. This arrangement of beach and dune deposits is considered part of the Cutler Group. Continued progradation of the Kaibab Sea to the east created another overlying layer, comprised of shallow marine deposits, which is now referred to as the Kaibab Limestone. Evidence of this shallow marine environment can be found within the Kaibab Limestone in the form of very fine-grained sandstone and fossils within the limestone such as crinoids (Sprinkel et al., 2003). During the late Permian Period, the Uncompahgre Highlands became a significant orogenic feature, creating a major source for sediment and becoming a part of what is believed to be the modern-day Rocky Mountains (Utah Geological Survey, n.d.).

An unconformity marks the contact between the rocks of the late Permian and the rocks of the early Triassic Period (Geos 220, 3/11/2020). At this time, about 240 million years ago, the area of present-day Utah was covered, for the most part, by the Moenkopi Sea, with another portion of the area to the southeast covered by a significant river delta system (Geos 220, 3/11/2020). The transgression and regression of the shoreline in the area of interest created a relatively thick layer of alternating tidal and deltaic deposits. No deep marine deposits can be found in the rocks of the early Triassic Period as the rivers and deltas in the area were at sea level, and the shoreline did not prograde far enough to the east to produce deep marine deposits. Additionally, there were no major orogenies present in the area of the present-day western United States, as the early Triassic was a period of tectonic inactivity (Morris, et al., 2016). The relative lack of tectonics in the area of interest around this time is the primary reason that the area was flat with no significant mountain range. Evidence of this flat deltaic and shallow marine environment can be found within the Moenkopi Formation in the form of mudcracks, brachiopod fossils, and swim tracks of amphibians or reptiles (Utah Geological Survey, n.d.). Additionally, the Moenkopi Formation is the primary group of rocks associated with the early Triassic time period (Sprinkel et al., 2003).

The middle Triassic Period was not preserved in rocks of the area as the early and late Triassic Periods share a contact that is an erosional unconformity (Sprinkel et al., 2003). In the late Triassic, major alluvial systems and scattered swamp areas dominated the deposition of sediment in eastern Utah (Morris, et al., 2016). Additionally, the Ancestral Rocky Mountains and a volcanic arc in present-day California both formed around this time (Geos 220, 3/11/2020). Evidence for a large area of braided rivers in the area can be inferenced by cross-stratification and grain sizes in the Shinarump Conglomerate Member of the Chinle Formation. (Sprinkel et al., 2003). The river system that deposited the Chinle Formation flowed to the west-northwest from their origin point in the southern Appalachian region (Blakely, n.d.). The braided river system migrated northward after the deposition of the Shinarump Conglomerate Member, resulting in a large lake in the area of interest. This large lake system dominates the depositional processes of sediment, ultimately producing an abundance of mudstones, siltstones, and limestones that is now known as the Owl Rock Member (Sprinkel et al., 2003). Further evidence of a large lake system found within the Owl Rock Member includes large burrows, mudcracks, and thin layers of volcanic ash deposits originating from the volcanic arc that existed in California at the time (Sprinkel et al., 2003). The characteristic feature of the Chinle Formation, the petrified wood from large trees that once grew on the banks of these large rivers and lakes, can be commonly found in both members of the Chinle Formation.

An erosional unconformity forms the contact between the rocks of the late Triassic Period and the rocks of the early Jurassic Period (Geos 220, 3/11/2020). Early in the Jurassic Period, around 200 million years ago, eastern Utah was completely covered by a large, dry desert of rolling sand dunes (Utah Geologic Survey, n.d.). Wind was the primary sediment transportation method during this time, as eastern Utah was comprised of a desert environment. Evidence of an eolian environment can be found within the rocks of the Wingate Sandstone, which exhibits characteristic large cross-stratification and desert varnish (Geos 220, 3/11/2020). Sometime thereafter, but still early within the Jurassic Period, the environment changed. This change was seemingly gradational as no unconformity is seen between the Wingate Sandstone and the overlying Kayenta Formation (Sprinkel et al., 2003). In this changed environment, fluvial processes once again dominated the transportation and deposition of sediment (Morris, et al., 2016). Evidence for small river systems during the depositional time of the Kayenta Formation in the early Jurassic primarily comes from thin layers of mud interspersed with layers of sandstone that have much smaller cross-stratification than the previous Wingate Sandstone (Sprinkel et al., 2003). Conglomerate mudchips are also common evidence for small river systems dominating the landscape at this time. The streams associated with the early Jurassic Period appear to have flowed toward the west, likely after originating in the orogenic region that became the Rocky Mountains (Geos 220, 3/11/2020). Once again during the early Jurassic Period, the environment changed once again in a major way. The area reverted back to an arid, sandy desert after a gradational change from the stream-dominated environment that deposited the Kayenta Formation (Sprinkel et al., 2003). In the changed environment, transportation and deposition of sediment in the area of focus was due to eolian processes. Utah at that point in time strongly resembled a desert, much like the present-day Sahara Desert in Africa (Geos 220, 3/11/2020). The major sand dune deposits are evident in the rock found in the Navajo Sandstone, including structures such as frosted grains, well-rounded grains, and very large cross-stratification (Sprinkel et al., 2003). 

In the middle Jurassic Period (about 170 million years ago) a long, relatively thin seaway moved inland originating from the north, and an area of sand dunes along its eastern shore comprise the environment of Utah (Blakely, n.d.). This environment is preserved in the rocks of the Carmel Formation, which provides evidence for shallow marine flooding and evaporation with sedimentary structures including evaporative crystals and low-lying, tidal flat characteristics (Geos 220, 3/11/2020). Additional information found within the Carmel Formation that suggests a shallow marine environment are layers of siltstones and limestones that include marine fossils (Sprinkel et al., 2003). It appears that at some point in the middle Jurassic Period the environment changed. The sea level regressed from the point at which the Carmel was deposited, creating a very large tidal flat that covered an expanse of present-day Utah (Geos 220, 3/11/2020). In addition, the area of sand dunes expanded to cover a much larger area than it had during the time that the Carmel Formation was deposited, extending outward into adjacent regions that now are the states of Colorado, Arizona, and New Mexico (Geos 220, 3/11/2020). It was during this time that the Entrada Sandstone was deposited by both eolian and sabkha methods (Morris, et al., 2016). The vast majority of the sandstone that comprises the Entrada Sandstone would have been deposited in the dry desert region to the east of the large tidal flat. Sabkha, or evaporite, deposits within the Entrada Sandstone would have come as sea level rose and fell, creating periods where the tidal flat was able to completely dry up. It also appears that the Nevada orogenic belt originated around this time period, creating an area of uplift to the west of the tidal flat (Geos 220, 3/11/2020). Another period of sea level transgression occurred in the middle Jurassic Period, which once again created a tidal flat environment in present-day eastern to central Utah (Sprinkel et al., 2003). The Curtis Formation originated in this environment, which is known for the glauconitic sandstone of a marine deposit, meaning that the Curtis Formation was deposited in a time when the area experienced shallow marine after the dry period of the Entrada (Geos 220, 3/11/2020). In a relatively short amount of time, the environment changed again. The sea level once more regressed to the point that the area of focus was a large tidal flat. This environment deposited the rocks of the Summersville Formation, which includes significant evidence that suggests a tidal flat depositional environment. This evidence includes abundant siltstones and mudstones, evaporite deposits, small-scale cross-stratification, and mudcracks (Sprinkel et al., 2003).

In the late Jurassic Period, around 150 million years ago, the environment was drastically changed from the previous environments of the middle Jurassic (Utah Geologic Survey, n.d.). A very large, east-flowing river system developed as the area to the west increased in elevation relatively quickly due to the orogeny in Nevada (Blakely, n.d.). The Morrison Formation is associated with this vast fluvial system in the late Jurassic Period, most well-known for the impressive dinosaur fossils preserved by the rock formation (Morris, et al., 2016). The area rapidly evolved around this time due to the braided nature of the river systems, often changing locally between river, flood plain, and lake relatively quickly.

In the early Cretaceous Period, around 130 million years ago, a major orogenic event took place, uplifting areas in Western Utah and creating the Sevier orogenic belt (Geos 220, 3/11/2020). The area of interest was largely dominated by the northeast-flowing fluvial systems that deposited the Cedar Mountain Formation. Evidence for a fluvial environment around this time comes from freshwater fossils and dinosaur bones found within the sandstones of the Cedar Mountain Formation (Sprinkel et al., 2003). Additionally, the existence of conglomerates in the area suggests that the depositional area was proximal to the source area of uplift (Geos 220, 3/11/2020). Thrust faults generally began causing a drop of elevation around the area of interest, resulting in sea level transgression in the Utah area, which then deposited the Dakota Sandstone (Morris, et al., 2016). The evidence for a shallow marine environment in this time are marine bivalve fossils that can be found within the Dakota Sandstone (Sprinkel et al., 2003). 

In the late Cretaceous Period, around 90 million years ago, the Western Interior Seaway reached its maximum extension into present-day Utah, covering about half of the land area as the sea level reached its highest point (Geos 220, 3/11/2020). The Mancos Shale is associated with the sediment deposited within this environment (Figure 13). The earliest members of the Mancos Shale, the Tununk Member and the Ferron Sandstone, are comprised of mudstones and siltstones with marine fossils commonly found, indicating a marine depositional environment (Sprinkel et al., 2003).

Following deposition of the Mancos Shale, the Western Interior Seaway slowly receded from the eastern Utah area. Between the late Cretaceous and early Paleogene Periods, the Farallon Plate began subducting beneath the North American Plate (Morris, et al., 2016). Due to the low angle of subduction in this case, the subducting slab was enabled to reach further under the continent as it was not hot enough to melt, ultimately affecting the area of interest in Utah (Geos 220, 3/11/2020). This subduction event dominated the landscape at the time, and in turn forced uplift in rocks in present-day Utah, a mountain-building event known as the Laramide Orogeny. The Laramide Orogeny itself caused major folds including the San Rafael Swell and Waterpocket Fold, creating many characteristic monoclines throughout the eastern Utah region (Morris, et al., 2016).

Learn more about how anticlines are formed with an animation found at the linked site below.

In the Neogene Period, the most recent period of significant tectonic change in eastern Utah, the Farallon Plate finally sinks deep enough into the mantle to melt (Morris, et al., 2016). The melting of the plate created a hotspot around 15 million years ago which produced a volcanic chain in present-day eastern Utah with basalt flows and volcanic cones increasing in age to the southwest, indicating that the North American Plate is moving to the southwest (Geos 220, 3/11/2020).

This section section of the report provides descriptions in outcrop, in hand sample, and environmental interpretations of the many rock units that comprise the stratigraphy of the San Rafael Swell and Moab areas. Descriptions of rock units in outcrop were compiled from literature sources. Descriptions of rock units in hand specimen were compiled both from specimens from the areas and literature sources. Environmental interpretations of the rock units were created based on evidence presented in the outcrop and hand specimen descriptions and literature sources. This information can be utilized as useful context for studying these regions of Utah both in the past and the present. 

The stratigraphic column above offers a brief overview of the variety of rock units present in the San Rafael Swell area. While it is not to scale, an idea of rock unit thicknesses can be formulated based on the listed ranges in thickness that have been compiled from literature research. A brief section of comments is included that highlight key features of these particular rocks that could assist with in-field identification.

The Precambrian basement is a term that describes deeply buried rock that was the oldest formed in San Rafael Swell area, and is seldom seen in outcrop today. The basement is primarily made up of granites that appear dark in color when viewed in an outcrop (Figure 17). Some metamorphic rocks, such as schist, can be found in the Precambrian basement. This unit was the group of rocks that faulted to produce the San Rafael Swell during the orogeny of the period.

The “basement” of the San Rafael Swell and Moab areas was likely deposited as a result of a various rock material that collided and attached itself to the newly-formed continent (Utah Geological Survey, n.d.).

In outcrop, the undifferentiated Paleozoic includes some of the oldest rocks exposed in the San Rafael Swell and Moab areas, however, most remains not exposed at the surface (Sprinkel et al., 2003). Rocks consisting of the undifferentiated Paleozoic range from sandstones to limestones to evaporites (Sprinkel et al., 2003). The thickness of the undifferentiated Paleozoic can also vary greatly from area to area anywhere up to 10,000 feet in total (Sprinkel et al., 2003). The undifferentiated Paleozoic shares a contact with the underlying “basement” (Sprinkel et al., 2003). The Undifferentiated Paleozoic also shares a contact with the overlying Cutler Formation, which is considered an unconformity (Sprinkel et al., 2003).

In hand specimen, samples of the undifferentiated Paleozoic appear highly variable in color (Sprinkel et al., 2003). In terms of its petrology, the undifferentiated Paleozoic specimen is fine to medium-grained. The rock can be relatively well-cemented (Sprinkel et al., 2003). Additionally, hand specimens of the undifferentiated Paleozoic can contain some feldspars and dark minerals in addition to an abundance of quartz (Sprinkel et al., 2003). According to Sprinkel et al. (2003), hand specimens of the undifferentiated Paleozoic can contain various species of fossil including crinoids and brachiopods.

The presence of feldspars and dark minerals suggest the depositional environment was relatively close to the source of sediment. Limestone and Evaporite deposits mentioned by Sprinkel (2003) could suggest a shallow sea that eventually dried up in order to produce evaporite deposits. The presence of crinoids and brachiopods suggests a shallow marine environment as well. Based on these observations the most consistent interpretation of the data would be that the undifferentiated Paleozoic was deposited in an ancient shallow sea that eventually dried up.

In outcrop, the Cutler Formation appears red orange to brown in color. According to Sprinkel et al. (2003), the Cutler Formation consists of beds of sandstone that often exhibit tabular-planar cross-bedding and horizontal bedding. Trough cross-stratification and cut-and-fill structures can also be seen throughout the formation (Sprinkel et al., 2003). The Cutler Group is not often exposed in the Moab area, pinching out in several areas around the location (Sprinkel et al., 2003). While not exposed at the surface, it is believed that the Cutler Group ranges in thickness from 0 to 1,500 feet (Sprinkel et al., 2003). In the Moab area, the Cutler Formation shares a contact with the Moenkopi Formation as there is an unconformity where the Kaibab Formation should be (Sprinkel et al., 2003). The Cutler Formation also shares a contact with the Honaker Trail Formation, which is a part of the undifferentiated Paleozoic (Sprinkel et al., 2003). 

The tabular-planar cross-stratification mixed with horizontal bedding seems to indicate an eolian period of transport and deposition in the environment that the Cutler Formation formed in. The somewhat poor sorting of the grains in hand specimen, in addition to the somewhat angular clasts suggests a depositional environment relatively close to the source, in other words and alluvial fan. The rare occurrence of fossils suggested by Sprinkel et al. (2003) seems to indicate there may have also been a marine environment at the time of the Cutler’s deposition. Based on these observations, the most consistent interpretation of the data would be that the Cutler Formation was deposited somewhere very near to a shallow inland sea and also nearby to its source of sediment, an ancient mountain range.

In outcrop, the Kaibab Formation appears white to gray in color. According to Sprinkel et al. (2003), the Kaibab Formation consists of limestone that often has fine-grained sandstones to siltstones dispersed within its beds. Fossils of several invertebrates that originated in the Permian period can also be found throughout the formation (Sprinkel et al., 2003). Generally, the Kaibab Formation forms steep cliffs, which is a key distinguishing feature of the unit. The Kaibab Group is not often exposed in the Moab area, as there is an unconformity (Sprinkel et al., 2003). While not exposed at the surface, it is believed that the Kaibab Group can reach thicknesses of up to 200 feet. (Sprinkel et al., 2003). In the San Rafael Swell area, the Kaibab Formation shares a contact with the underlying Cutler Formation, but the Kaibab is not seen in the Moab region due to an unconformity (Sprinkel et al., 2003). The Kaibab Formation also underlies the Moenkopi Formation; the contact between the two units is an erosional unconformity (Sprinkel et al., 2003).

The interpretation of the rock as a quartz limestone with some layers of fine-grained siltstones and sandstones commonly found in outcrop suggests that the Kaibab Formation formed in a marine environment. This idea is further supported by the evidence of fossils of several invertebrate species including crinoids and gastropods. Based on these observations the most consistent interpretation of the data would be that the Kaibab Formation was deposited in a shallow marine environment.

In outcrop, the Moenkopi Formation primarily appears light brown, a distinctive feature, but certain sections could appear red in color. According to Sprinkel et al. (2003), the Moenkopi Formation consists of beds of sandstone, siltstone, and shale which commonly contain ripple marks and mudcracks. Fossils can also be found, although somewhat rarely, throughout the formation, and tracks of large reptiles can be found throughout the formation (Sprinkel et al., 2003). The Moenkopi Group forms both steep slopes and cliffs (Sprinkel et al., 2003). It is believed that the Moenkopi Group ranges in thickness from 0 to 1,300 feet (Sprinkel et al., 2003). In the Moab area, the Moenkopi Formation shares a contact with the underlying Cutler Formation as there is an unconformity where the Kaibab Formation should be (Sprinkel et al., 2003). The Moenkopi Formation also shares a contact with the Chinle Formation, and this contact is also believed to be an unconformity (Sprinkel et al., 2003).

The ripple marks and laminations evident in hand sample, in addition to the ripple marks and mudcracks found in outcrops of the Moenkopi Formation, suggest that there must have been an environment influenced by flowing water, but that the water was shallow enough to dry up. The evidence of fossils and tracks of reptiles in outcrop of the Moenkopi Formation suggest an environment that must have had shallow water as well. Based on these observations, the most consistent interpretation of the data would be that the Moenkopi Formation was deposited somewhere that shallow water was integral in deposition of the area, which could mean tidal flats or flood plains of rivers. As the Kaibab Formation was very likely deposited in a shallow marine environment, it seems reasonable that the Moenkopi was deposited in a region of tidal flats and alluvial fans. 

In outcrop, the Chinle Formation appears light gray to a more common red-brown in color. According to Sprinkel et al. (2003), the Chinle Formation consists of beds of sandstone, with occasional layers of conglomerate, siltstone, and mudstone. One distinguishing characteristic of the Chinle Formation is its propensity to form cliffs due to the erosion of the mudstone and siltstone between thick sandstone layers. Petrified wood and fossilized root systems can also be commonly found throughout the formation, another diagnostic feature of the Chinle Formation (Sprinkel et al., 2003). The Chinle is often exposed at the surface of the Moab area and it is believed that the Chinle Group ranges in thickness from 200 to 900 feet (Sprinkel et al., 2003). In the Moab area, the Chinle Formation shares a contact with the underlying Moenkopi Formation and this contact is believed to be an unconformity (Sprinkel et al., 2003). The Chinle Formation also shares a contact with the overlying Wingate Sandstone, which appears to be a disconformity (Sprinkel et al., 2003).

The well-sorted and well-rounded clasts of sand that exhibit sphericity in the hand sample of the Chinle suggest fluvial transport over a long enough distance to round the grains. Evidence of petrified wood and root systems in outcrops of the Chinle Formation also suggest that the Chinle Formation was deposited in a fluvial environment. The mudstone and siltstone evident in outcrop suggest something slightly different, as this would indicate a water-based environment with less flow than a river. Based on these observations the most consistent interpretation of the data would be that the Chinle Formation was deposited in an ancient braided river system where certain branches were active at any one time, while others were cut off to form oxbow lakes and point bars that could create mudstone and petrified wood from trees that had fallen into areas of stagnant water.

In outcrop, the Wingate Sandstone appears red to brown in color, but sections can appear brown or black due to desert varnish. According to Sprinkel et al. (2003), the Wingate Sandstone consists of beds of sandstone that often are interpreted as massive, but some planar bedding and cross-stratification can be seen. The Wingate Sandstone is commonly found in the Moab area, forming distinguishing cliffs with desert varnish (Sprinkel et al., 2003). It is believed that the Wingate Sandstone on average reaches thicknesses of about 300 feet (Sprinkel et al., 2003). In the Moab area, the Wingate Sandstone shares a contact with the overlying Kayenta Formation, with a gradual transition from one to the next (Sprinkel et al., 2003). The Wingate Sandstone also shares a contact with underlying Chinle Formation, which is a disconformity (Sprinkel et al., 2003).

The well-rounded, frosted grains displayed by the Wingate Sandstone in hand sample seem to strongly suggest that the Wingate Sandstone was transported with eolian conditions. Cross-stratification of the Wingate Sandstone in outcrop further supports this idea. Based on these observations the most consistent interpretation of the data would be that the Wingate Sandstone was deposited by wind, based on the previous interpretation of a braided river system for the Chinle it could be that most of the rivers of the Chinle era have now dried up, leaving an abundance of sand to be transported by wind.

In outcrop, the Kayenta Formation appears red when the entire formation is viewed together, but individual beds of sandstone can vary in color from white to red to pale purple (Sprinkel et al., 2003). According to Sprinkel et al. (2003), the Kayenta Formation consists of large beds of sandstone. Some fossils can also be found throughout the formation (GEOS 220, 2/24/2020). Sprinkel et al. (2003) claim that the Kayenta Formation is easiest distinguished from the underlying Wingate Sandstone by the thick ledges exhibited by the Kayenta Formation, which contrast the massive cliffs of the Wingate Sandstone. The Kayenta Group typically has a thickness of 300 feet (Sprinkel et al., 2003). In the Moab area, the Kayenta Formation shares a gradational contact with the underlying Wingate Sandstone (Sprinkel et al., 2003). The Kayenta Formation also shares a contact with the overlying Navajo Sandstone, but this contact is often confusing as the two units can interfinger in some areas (Sprinkel et al., 2003).

The evidence of fluvial depositional features in outcrops of the Kayenta Formation such as ripple marks and channels indicate that water has once again come to dominate depositional processes in the area. The slightly larger and lack of well-developed sorting in the hand specimen indicates that the source of the deposited material was, once again, not very far from its depositional location. The smaller scale of the channels and ripples that can be found in the Kayenta Formation indicate that this is a river system rather than a marine environment, and a smaller system than that of the Chinle Formation. Based on these observations the most consistent interpretation of the data would be that the Kayenta Formation was deposited in a small river system which was nearby to its source of sediment, an ancient mountain range.

In outcrop, the Navajo Sandstone appears white to light gray in color, which is one of its distinguishing characteristics. According to Sprinkel et al. (2003), the Navajo Sandstone consists of beds of sandstone that often exhibit high-angle cross-stratification, the second distinguishing characteristic of the Navajo Sandstone. The Navajo Sandstone is very resistant to weathering which means it commonly forms cliffs (Sprinkel et al., 2003). The Navajo Sandstone is one of the most common and easily distinguishable units exposed in the Moab and San Rafael Swell areas (Sprinkel et al., 2003). The Navajo Sandstone ranges in thickness from 200 to 550 feet, but this is highly variable due to the interfingering of the underlying Kayenta (Sprinkel et al., 2003). In the Moab area, the Navajo Sandstone shares a contact with the underlying Kayenta Formation which is often interfingering of the two rock units (Sprinkel et al., 2003). The Navajo Sandstone also shares a contact with the overlying Carmel Formation, which forms a regional unconformity (Sprinkel et al., 2003).

The evidence of large-scale high-angle cross beds of the Navajo Sandstone strongly suggests that the deposition of sediment in the area had once again become eolian-dominated. The very fine to fine quartz grains of the Navajo, coupled with the fact that they are frosted and well-rounded, also suggests that the area is an eolian-deposited environment once again, but on a very large scale. The cross-bed sizes of the Navajo suggest that the eolian transport was not beach related. Based on these observations, the most consistent interpretation of the data would be that the Navajo Sandstone was deposited in a period of dryness, similar to the Wingate Sandstone, but that the depositional environment is a much larger area, similar to the present-day Sahara Desert.

In outcrop, the Carmel Formation appears yellow, gray, or brown in color. According to Sprinkel et al. (2003), the Carmel Formation consists of beds of planar-bedded sandstone with less common beds of limestone and gypsum interspersed within the unit. Some red to brown sandstone can also be seen throughout the formation (Sprinkel et al., 2003). It is believed that the Carmel Group ranges in thickness from 200 to 1,000 feet (Sprinkel et al., 2003). In the Moab area, the Carmel Formation shares a contact with the underlying Navajo Sandstone which is considered a regional unconformity (Sprinkel et al., 2003). The Carmel Formation also shares a contact with the overlying Entrada Sandstone, which is a sharp contrast between the two layers, where the two often interfinger (Sprinkel et al., 2003).

The evidence of planar beds and gypsum in the outcrops of the Carmel Formation suggest that a period of marine-dominated deposition has returned to the area. The silty to very-fine grain size in the hand specimen suggests that there was little to no flow of water as the Carmel was deposited. Based on these observations, the most consistent interpretation of the data would be that the Carmel Formation was deposited in a tidal environment due to the lack of evidence for a current, and that the marine environment must have dried up periodically as suggested by evidence of gypsum in the outcrop.

In outcrop, the Entrada Sandstone appears orange to light brown in color. According to Sprinkel et al. (2003), the Entrada Sandstone consists of massive beds of sandstone that often exhibit cross-stratification or planar bedding. However, “interbedded shale, siltstone, and sandstone with planar beds” are primary features of the Entrada in the San Rafael Swell area (Sprinkel et al., 2003). Banding in the layers of the Entrada Sandstone is one of the unit’s most distinguishing features (Sprinkel et al., 2003). It is believed that the Entrada Sandstone ranges in thickness from 200 to 400 feet in the Moab area and is about 425 feet thick in the San Rafael Swell area (Sprinkel et al., 2003). In the Moab area, the Entrada Sandstone shares a sharp and locally interfingering contact with the underlying Carmel Formation (Sprinkel et al., 2003). The Entrada Sandstone also shares a regional unconformable contact with the overlying Curtis Formation, which appears very sharp in outcrop (Sprinkel et al., 2003).

The evidence of shale, siltstone, and sandstone that exhibit planar beds in outcrops of the San Rafael Swell area suggests a depositional environment dominated by water that had little to no current. However, the evidence of massive beds of sandstone that exhibit cross-stratification in the Moab area suggests that a depositional environment dominated by aeolian transport and deposition (Carr and Kocurek, 1988). Based on these observations the most consistent interpretation of the data would be that the Entrada Sandstone did not have a consistent depositional environment between the two locations, as it must have varied from shallow marine in the west near the San Rafael Swell to eolian deposited sand dunes in the east near Moab.

In outcrop, the Curtis Formation appears white, light green, or gray in color (Figure 37). According to Sprinkel et al. (2003), the Curtis Formation consists of beds of massive sandstone that often form cliffs due to the general hardness of the rock. Low-angle cross-beds can also be seen throughout the formation (Sprinkel et al., 2003). The Curtis Formation is a relatively thin formation of rock, ranging in thickness from 60 to 120 feet near Moab and about 85 feet thick near the San Rafael Swell (Sprinkel et al., 2003). In the Moab area, the Curtis Formation shares a contact with the underlying Entrada Sandstone as there is a regional unconformity which creates an abrupt transition between the two units (Sprinkel et al., 2003). The Curtis Formation also shares a contact with the overlying Summersville Formation, which is referred to as a “thin red marker unit” (Sprinkel et al., 2003).

The tendency for the hand specimen to fizz when a weak acid is introduced suggests that the Curtis Formation may have been deposited in a marine environment. This idea is also supported by the evidence of low angle cross-beds found in the outcrops of Curtis Formation. The size and poor sorting of the grains speaks against the idea that wave processes could have been a factor in depositing the rock of the Curtis Formation. Based on these observations the most consistent interpretation of the data would be that the Curtis Formation was deposited somewhere near to the shoreline of an ancient sea.

In outcrop, the Summersville Formation appears primarily red in color. According to Sprinkel et al. (2003), the Summersville Formation consists of thin to medium beds of sandstone and common thin-bedded siltstones. Mudcracks, very small cross-beds, and ripple structures can also be seen throughout the formation (Sprinkel et al., 2003). Gypsum can be found within outcrops of Summersville Formation in the San Rafael Swell area (Sprinkel et al., 2003). The Summersville Group is not very thick in the Moab area, pinching out in several areas around the location (Sprinkel et al., 2003). It is believed that the Summersville Group ranges in thickness from 6 to 20 feet in the Moab area and up to 340 feet in the San Rafael Swell area (Sprinkel et al., 2003). In the Moab area, the Summersville Formation shares a contact with the underlying Curtis Formation as there is a distinguishing sharp contact between the characteristic light colors of the Curtis Formation and the deep red color of the Summersville Formation (Sprinkel et al., 2003). The Summersville Formation also shares a contact with the overlying Morrison Formation, which is considered an unconformity (Sprinkel et al., 2003).

In hand specimen, a sample of the Summersville Formation appears light-tan, brown, or red in color (Sprinkel et al., 2003). In terms of its petrology, the Summersville specimen is silty to fine-grained sandstone, with clasts that are well-rounded and well-sorted (Sprinkel et al., 2003). The rock is relatively well-cemented, with quartz its primary constituent (Sprinkel et al., 2003). Specimens are non-calcareous (Sprinkel et al., 2003). Based on these descriptions, the Summersville Formation could be classified as a subarkose or quartz arenite. According to Sprinkel et al. (2003), hand specimens of the Summersville Formation can contain ripple marks if taken from the top of the formation.

The evidence of thin beds of both sandstone and siltstones comprising outcrops of the Summersville Formation in both the Moab and San Rafael Swell areas suggests that there was little to no current influencing deposition at the time the Summersville Formation was deposited. Additionally, the evidence for primary depositional features such as mudcracks, small cross-beds, and ripple structures suggest that water influenced the deposition at this time. The presence of both mudcracks and gypsum in outcrops of Summersville Formation suggest that it was deposited in a time that was wet, but also dried up occasionally. The classification of this hand specimen as a siltstone would suggest a marine environment as strongly as the other evidence does. Based on these observations the most consistent interpretation of the data would be that the Summersville Formation was deposited on a tidal flat that often experienced dry spells to produce evaporites.

In outcrop, the Morrison Formation appears in a variety of colors including red, light brown, dark brown, and green. According to Sprinkel et al. (2003), the Morrison Formation consists of beds of siltstone and muddy siltstone with some uncommon areas of sandstone. The Morrison Formation is known for its dinosaur fossils and petrified wood, but the “popcorn” appearance of some of its weathered surfaces is also diagnostic (Sprinkel et al., 2003). The Morrison Group is commonly found in the Moab area, ranging in thickness from 300-450 feet and is the final geologic member found in the San Rafael Swell area reaching a thickness of 150 feet (Sprinkel et al., 2003). In the Moab area, the Morrison Formation shares a contact with the underlying Summersville Formation as there is a recognizable unconformity (Sprinkel et al., 2003). The Morrison Formation also shares a contact with the overlying Cedar Mountain Formation, which is regarded as another unconformity (Sprinkel et al., 2003).

The classification of the Morrison Formation hand specimen as a mudstone or siltstone without evidence for calcite suggests that water was once again involved in the depositional environment, but that this was not a marine environment as there is no calcite present. Evidence for dinosaur fossils and petrified wood in the Morrison Formation suggests that the environment was dominated by fluvial processes. Based on these observations the most consistent interpretation of the data would be that the Morrison Formation was deposited in a shallow, slow-moving fluvial system that allowed mud to be deposited and preserved fallen trees as petrified wood and dinosaurs as fossils as well.

In outcrop, the Cedar Mountain Formation appears light brown to dark brown in color. According to Sprinkel et al. (2003), the Cedar Mountain Formation consists of beds of sandstone that contains mudstone intervals. Fossils, including those of dinosaurs, are common, and white petrified wood can also be seen throughout the formation (Sprinkel et al., 2003). One distinguishing characteristic of the Cedar Mountain Formation is the hardness of the rock that creates its propensity to form cliffs (Sprinkel et al., 2003). It is believed that the Cedar Mountain Formation ranges in thickness from 100 to 250 feet (Sprinkel et al., 2003). In the Moab area, the Cedar Mountain Formation shares a contact with the overlying Dakota Sandstone where an unconformity is present (Sprinkel et al., 2003). The Cedar Mountain Formation also shares a contact with the underlying Morrison Formation, which is considered another unconformity (Sprinkel et al., 2003).

In hand specimen, a sample of the Cedar Mountain Formation appears light brown to dark brown in color (Sprinkel et al., 2003). In terms of its petrology, the Cedar Mountain specimen varies in grain size including clasts that are fine, medium, coarse, and conglomeratic, with clasts that are well-rounded and moderately sorted (Sprinkel et al., 2003). The rock is relatively well-cemented (Sprinkel et al., 2003). The Cedar Mountain Formation hand specimen could be classified as a sedimentary conglomerate based on the large size of some of its clasts. According to Sprinkel et al. (2003), hand specimens of the Cedar Mountain Formation could contain various species of fossil including those of larger dinosaur species.

The well-rounded clasts of various sizes that make up the hand specimen of the Cedar Mountain Formation suggests that eolian or fluvial processes were at work to round the grains, but that the source must be relatively nearby as it is not yet well-sorted. The evidence of mudstone in outcrops of the Cedar Mountain Formation provides strong evidence against eolian deposition and strong evidence for fluvial deposition. Fossils of dinosaurs and petrified wood can be found in outcrops of the Cedar Creek Formation, further supporting a fluvial system. Based on these observations, the most consistent interpretation of the data would be that the Cedar Mountain Formation was deposited in a fluvial system and also nearby to its source of sediment, an ancient mountain range.

In outcrop, the Dakota Sandstone appears tan to dark gray in color. According to Sprinkel et al. (2003), the Dakota Sandstone consists of beds of sandstone with intermittent layers of conglomerate, shale, and coal seams. Dinosaur footprints are preserved and can be found throughout the formation in addition to fossilized bivalves and petrified wood (Sprinkel et al., 2003). The Dakota Sandstone is most recognizable in outcrop by its conglomerate and conglomeratic sandstone layers (Sprinkel et al., 2003). The Dakota Sandstone ranges in thickness from 0 to 150 feet (Sprinkel et al., 2003). In the Moab area, the Dakota Sandstone shares a contact with the underlying Cedar Mountain Formation recognized as an unconformity at the base of a white layer of clay (Sprinkel et al., 2003). The Dakota Sandstone also shares a contact with the overlying Mancos Shale, which is gradational in nature (Sprinkel et al., 2003).

The evidence of dinosaur footprints and petrified wood in outcrops of the Dakota Sandstone seem to suggest a fluvial depositional environment. However, the classification of the hand specimen as a mudstone or shale with carbonaceous material included strongly suggests that the Dakota sandstone was deposited in a marine environment. Coal seams would suggest that there was no current flow during this depositional time period. Additionally, the evidence of bivalve fossils in outcrop and fine-grained rocks in both hand specimen and outcrop also suggest a marine depositional environment. Based on these observations, the most consistent interpretation of the data would be that the Dakota Sandstone was deposited in a shallow marine environment.

In outcrop, the Mancos Shale appears gray to dark brown in color. According to Sprinkel et al. (2003), the Mancos Shale consists of layers of fissile shale that often exhibit more sand composition in the younger members of the unit. The fossils of shellfish can also be seen throughout the formation (Sprinkel et al., 2003). The Mancos Shale is commonly exposed in the Moab and San Rafael Swell areas, reaching thicknesses that range from 700 to 2,000 feet (Sprinkel et al., 2003). In the Moab area, the Mancos Shale shares a contact with the underlying Dakota Sandstone, which is considered a gradational contact (Sprinkel et al., 2003).

Based on the classification of the Mancos Shale as a fissile shale and sandy silt in outcrop and hand specimen respectively, the evidence suggests that there was little to no current influencing deposition during the time of the Mancos Shale. In hand sample the rock would fizz due to its calcite content which suggests that the Mancos Shale was deposited in a marine environment. Additionally, the evidence of fossilized shellfish in Mancos Shale outcrops supports this idea. Based on these observations the most consistent interpretation of the data would be that the Mancos Shale was deposited in a deeper marine environment than the previous Dakota Sandstone unit, as the shoreline must have migrated further.

As mentioned earlier, the area of interest in this report is the San Rafael Swell (Figure 47), yet the entirety of the geologic structure is too large for effective field interpretations when considering the scope of the field trip that was planned. In lieu of field interpretations taking place in the area of study, the field trip cancellation necessitated the use of Google Earth photography in addition to provided data from M. Scott Wilkerson (2020) in order to make necessary field observations and collect the data required to create a geologic map and cross section. The area utilized for mapping and cross section interpretation is highlighted below (Figure 48). This area, while still quite large in human terms, encompasses just a small section on the easternmost limb of the San Rafael Swell. This limb is significant in that it exhibits a clear anticline structure.

The above imagery (Figure 48) was utilized to create the initial geologic map of the area of interest. Some primary contact data was provided by Wilkerson (2020), and further contact data was gathered in Google Earth by examining variations in outcrop, especially color, apparent in available imagery. Once a geologic contact was found, it was traced from one end of the map region to the other with polyline tools that can used in the Google Earth program. Once contact tracing was complete, the data was transferred into the drawing program Adobe Illustrator in order to retrace the contacts, color the exposed geologic units, and label them. Younger units of rock lie to the east, as the anticline structure of the San Rafael Swell, which causes overall dips in the eastern direction as evidenced by dip data (Figure 49), has eroded the uplifted younger rock units in the west. This, in turn, has exposed older rocks which lie to the west on the map.

The geologic map (Figure 49) was the primary resource used to create the cross section of the San Rafael Swell (Figure 50). Additional resources used included dip data provided by Wilkerson (2020), Google Earth imagery, and literature research to determine the origin and overall form of the anticline structure. A topographic profile was obtained using Google Earth. Contact data from the previously created geologic map provided the basis for the unit contacts on the cross section. Dip data was also transferred from the original geologic map using tie lines. The anticline was revealed to have parallel beds by both Wilkerson (2020) and map data. Rock units that remain at and below the surface are represented in opaque coloration, whereas rock units that have been eroded away have a transparent coloration. A fault is represented in the hinge of the anticline based on literature research (Morris, et al, 2016). This fault was produced by the Laramide Orogeny which took place about 70 million years ago (Morris, et al, 2016). The brittle granite of the Precambrian basement could not maintain its integrity under the stresses on compression that took place at that time. Thus, the fault that underlies the anticline of the San Rafael Swell was created, and overlying sedimentary rock resisted faulting due to its less-brittle nature (Morris, et al, 2016). This allowed the anticline structure of the San Rafael Swell to develop into the impressive dome-shaped formation that can be seen today.

(Figure 1): Mullins, William, 2019, San Rafael Swell: https://fineartamerica.com/featured/2-san-rafael-swell-william-mullins.html, (accessed May 10, 2020).

(Figure 2): Gavan, Mary and Wegner, Dave, 2017, The Evolution of the Colorado Plateau and Colorado River, https://medium.com/river-talk/the-evolution-of-the-colorado-plateau-and-colorado-river-ac159791b73c, (accessed May 10, 2020).

(Figure 3): Dewaelsche, Peyton, 2020, Express Map of San Rafael Swell Area.

(Figure 4): Karlstrom, Karl and Humpherys, Eugene, 1998, Persistent influence of Proterozoic accretionary boundaries in the tectonic evolution of southwestern North America: Interaction of cratonic grain and mantle modification events, Rocky Mountain Geology, p. 161-179. 

(Figure 5): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 6): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 7): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 8): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 9): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 10): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 11): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 12): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 13): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 14): Share, Jack, 2014, Written In Stone…seen through my lens, http://written-in-stone-seen-through-my-lens.blogspot.com/2014_09_01_archive.html, (Accessed May 10, 2020).

(Figure 15): Fillmore, R., 2000, The Geology of the Parks, Monuments, and Wildlands of Southern Utah, University of Utah Press, Salt Lake City, Utah, p. 61-65.

(Figure 16): Dewaelsche, Peyton, 2020, Composite Stratigraphic Column for San Rafael Swell and Moab Regions.

(Figure 17): Museums of Western Colorado, n.d., Geology and Paleontology of the Grand Valley, https://museumofwesternco.com/learn/grand-valley-geo-and-paleo/, (Accessed May 10, 2020).

(Figure 18): Museums of Western Colorado, n.d., Geology and Paleontology of the Grand Valley, https://museumofwesternco.com/learn/grand-valley-geo-and-paleo/, (Accessed May 10, 2020).

(Figure 19): Wikipedia, 2020, Cutler Formation, https://en.wikipedia.org/wiki/Cutler_Formation, (Accessed May 10, 2020).

(Figure 20): DiMichele, William A., et al., 2014, Fossil-Floras from the Pennsylvanian-Permian Cutler Group of Southeastern Utah, https://pdfs.semanticscholar.org/659f/7fffc7d8ba9f2859055fa8668e27a406c6a9.pdf, (Accessed May 10, 2020).

(Figure 21): National Park Service, n.d., Kaibab Formation, https://www.nps.gov/zion/learn/nature/kaibab.htm, (Accessed May 10, 2020).

(Figure 22): Wilkerson, M. Scott, 2020, Kaibab Hand Sample, (Accessed May 10, 2020).

(Figure 23): National Park Service, n.d., Moenkopi Formation, https://www.nps.gov/zion/learn/nature/moenkopi.htm, (Accessed May 10, 2020).

(Figure 24): Wilkerson, M. Scott, 2020, Moenkopi Hand Sample, (Accessed May 10, 2020).

(Figure 25): National Park Service, n.d., Chinle Formation, https://www.nps.gov/zion/learn/nature/chinle.htm, (Accessed May 10, 2020).

(Figure 26): Wilkerson, M. Scott, 2020, Chinle Hand Sample, (Accessed May 10, 2020).

(Figure 27): National Park Service, n.d., Wingate Sandstone, https://www.nps.gov/cany/learn/nature/wingate.htm, (Accessed May 10, 2020).

(Figure 28): Wilkerson, M. Scott, 2020, Wingate Hand Sample, (Accessed May 10, 2020).

(Figure 29): National Park Service, n.d., Kayenta Formation, https://www.nps.gov/zion/learn/nature/kayenta.htm, (Accessed May 10, 2020).

(Figure 30): Wilkerson, M. Scott, 2020, Kayenta Hand Sample, (Accessed May 10, 2020).

(Figure 31): National Park Service, n.d., Navajo Sandstone, https://www.nps.gov/zion/learn/nature/navajo.htm, (Accessed May 10, 2020).

(Figure 32): Wilkerson, M. Scott, 2020, Navajo Hand Sample, (Accessed May 10, 2020).

(Figure 33): National Park Service, n.d., Carmel Formation, https://www.nps.gov/zion/learn/nature/carmel.htm, (Accessed May 10, 2020).

(Figure 34): Wilkerson, M. Scott, 2020, Carmel Hand Sample, (Accessed May 10, 2020).

(Figure 35): Wikipedia, 2020, Entrada Sandstone, https://en.wikipedia.org/wiki/Entrada_Sandstone, (Accessed May 10, 2020).

(Figure 36): Wilkerson, M. Scott, 2020, Entrada Hand Sample, (Accessed May 10, 2020).

(Figure 37): University of Utah, 2018, Curtis Formation, https://sed.utah.edu/Curtis.htm, (Accessed May 10, 2020).

(Figure 38): Wilkerson, M. Scott, 2020, Curtis Hand Sample, (Accessed May 10, 2020).

(Figure 39): Wikipedia, 2020, Summersville Formation, https://en.wikipedia.org/wiki/Summerville_Formation, (Accessed May 10, 2020).

(Figure 40): Tang, Carol Marie, n.d., Morrison Formation, https://www.britannica.com/place/Morrison-Formation, (Accessed May 10, 2020).

(Figure 41): Bentley, Callan, 2011, Ripple Marks and Cross Beds in the Morrison Formation, https://blogs.agu.org/mountainbeltway/2011/10/01/ripple-marks-and-cross-beds-in-the-morrison-formation/, (Accessed May 10, 2020).

(Figure 42): Wikipedia, 2020, Cedar Mountain Formation, https://en.wikipedia.org/wiki/Cedar_Mountain_Formation, (Accessed May 10, 2020).

(Figure 43): Wikipedia, 2020, Dakota Formation, https://en.wikipedia.org/wiki/Dakota_Formation, (Accessed May 10, 2020).

(Figure 44): Loope, David, et al., 2012, Iron Oxide Concretions, https://www.researchgate.net/figure/Rinded-concretions-in-the-Dakota-Sandstones-Note-that-concretions-have-a-grain-supported_fig5_236952812, (Accessed May 10, 2020).

(Figure 45): McDonald, Nikolyn, n.d., Mancos Shale, https://fineartamerica.com/featured/mancos-shale-geology-utah-nikolyn-mcdonald.html?product=spiral-notebook, (Accessed May 10, 2020).

(Figure 46): Kocurek Industries, n.d., Mancos Shale, https://kocurekindustries.com/index.php?page_name=Mancos%20Shale&page_id=252&id=193, (Accessed May 10, 2020).

(Figure 47): Wikipedia, 2020, San Rafael Reef, https://en.wikipedia.org/wiki/San_Rafael_Reef, (Accessed May 10, 2020).

(Figure 48): Dewaelsche, Peyton, 2020, Google Earth Image of Geologic Map and Cross Section Area.

(Figure 49): Dewaelsche, Peyton, 2020, Geologic Map of the San Rafael Swell.

(Figure 50): Dewaelsche, Peyton, 2020, Cross Section of the San Rafael Swell.

Blakey, Ron, (Last revised: Unknown), Ron Blakey’s Paleogeographic Reconstructions of the Colorado Plateau, (Retrieved Apr. 9, 2020), from http://utahgeology.com/ron-blakeys-paleogeography-of-the-colorado-plateau/

Carr, M. and Kocurek, G., 1988, Entrada Sandstone: An Example of a Wet Eolian System, Geological Society Special Publications, p. 103-126.

Hintze, Lehi F., 1973, Geologic History of Utah, p. 10-12.

Karlstrom, Karl and Humpherys, Eugene, 1998, Persistent influence of Proterozoic accretionary boundaries in the tectonic evolution of southwestern North America: Interaction of cratonic grain and mantle modification events, Rocky Mountain Geology, p. 161-179.

Morris, T.H., Spiel, K.G., Cook, P.S., and Bonner, H.M., 2016, Landscapes of Utah’s Geologic Past, BYU Press, 80 p. 

National Park Service, (Last revised: Unknown), Geology – Capitol Reef National Park, (Retrieved Apr. 9, 2020) from https://www.nps.gov/care/learn/nature/geology.htm

Sprinkel, Douglas A., Chidsey, Thomas C., and Anderson, Paul B, 2003, Geology of Utah’s Parks and Monuments, Utah Geological Association and Bryce Canyon Natural History Association, Utah, 562 p.

Utah Geological Survey, (Last revised: Unknown), Utah: A Geologic History, (Retrieved Apr. 9, 2020) from https://geology.utah.gov/popular/general-geology/geologic-history/utah-a-geologic-history/

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Wilkerson, M.S., “Geologic Field Experiences Lecture.” DePauw University, 11 March 2020, DePauw University, Greencastle.