GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association ISSN 2380-7601 Volume 10 2023 This is an open-access article in which the Utah Geological Association permits unrestricted use, distribution, and reproduction of text and figures that are not noted as copyrighted, provided the original author and source are credited. Email inquiries to GIW@utahgeology.org. UTAH GEOSITE—THE SALINA CANYON UNCONFORMITY, A CLASSIC EXAMPLE OF MISSING TIME Shelley Judge, Emmett Werthmann, Cristina Millan, Michael Braunagel, and Erica Maletic GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association ISSN 2380-7601 Production Cover Design and Desktop Publishing Douglas A. Sprinkel Cover View of the Salina Canyon unconformity in the southern part of the Wasatch Plateau. The Jurassic Twist Gulch Formation forms the vertical to subvertical unit under the angular unconformity. Salina Canyon is an example of a progressive unconformity, with overlying strata including Paleogene sandstone beds of the Flagstaff and Colton Formations capped by the variegated cliffs of the Paleogene Green River Formation. i Become a member of the UGA to help support the work of the Association and receive notices for monthly meetings, annual field conferences, and new publi- cations. Annual membership is $30 and annual student membership is only $5. Visit the UGA website at www.utahgeology.org for information and membership application. The UGA board is elected annually by a voting process through UGA members. However, the UGA is a volunteer-driven organization, and we welcome your voluntary service. If you would like to participate please contact the current president or committee member corresponding with the area in which you would like to volunteer. Utah Geological Association formed in 1970 from a merger of the Utah Geological Society, founded in 1946, and the Intermountain Association of Geologists, founded in 1949. Affiliated with the American Association of Petroleum Geologists. Volume 10 2023 Geology of the Intermountain West (GIW) is an open-access journal in which the Utah Geological As- sociation permits unrestricted use, distribution, and reproduction of text and figures that are not noted as copyrighted, provided the original author and source are credited. 2022–2023 UGA Board President Rick Ford rford@weber.edu 801.915.3188 President-Elect Eugene Syzmanski eugenes@utah.gov 801.537.3364 Program Chair Megan Crocker meganlynncrocker@gmail.com 801.538.5290 Treasurer Aubrey DeReuil aubrey@zanskar.us 850.572.2543 Secretary Tom Chidsey tomchidsey@gmail.com 801.824.0738 Past President John South johnvsouth@gmail.com 801.367.9292 UGA Committees Environmental Affairs Craig Eaton eaton@ihi-env.com 801.633.9396 Geologic Road Sign Greg Gavin greg@loughlinwater.com 801.541.6258 Historian Paul Anderson paul@pbageo.com 801.364.6613 Outreach Greg Nielsen gnielsen@weber.edu 801.626.6394 Public Education Zach Anderson zanderson@utah.gov 801.537.3300 Matt Affolter gfl247@yahoo.com Publications Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Publicity Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Social/Recreation Roger Bon rogerbon@xmission.com 801.942.0533 AAPG House of Delegates 2020–2023 Term David A. Wavrek dwavrek@petroleumsystems.com 801.322.2915 State Mapping Advisory Committee UGA Representative Bill Loughlin bill@loughlinwater.com 435.649.4005 UGA Newsletter Newsletter Editor Bill Lund uga.newsletter@gmail.com 435.590.1338 UGA Website — www.utahgeology.org Webmaster Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Earthquake Safety Committee Chair Grant Willis gwillisgeol@gmail.com 801.537.3355 Douglas A. Sprinkel Azteca Geosolutions 801.391.1977 GIW@utahgeology.org dsprinkel@gmail.com Bart J. Kowallis Brigham Young University 801.380.2736 bkowallis@gmail.com Steven Schamel GeoX Consulting, Inc. 801.583-1146 geox-slc@comcast.net Thomas C. Chidsey, Jr. Utah Geological Survey 801.824.0738 tomchidsey@gmail.com John R. Foster Utah Field House of Natural History State Park Museum 435.789.3799 eutretauranosuchus@ gmail.com Editors GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association Volume 10 2023 169 ABSTRACT Salina Canyon, Utah, reveals a spectacular angular unconformity along an east-west transect through the southern part of the Wasatch Plateau. This region of Utah is well known as the eastern extent of Se- vier orogenesis, but it also includes subsequent extensional overprinting. Earliest descriptions of this un- conformity were published by Dutton (1880) and Spieker (1946, 1949), and work continues today. Field relationships expose many classic stratigraphic and sedimentologic features of erosional surfaces. Due to the geometry of the progressive unconformity onto the topographic high of the Sanpete-Sevier Valley anti- form, the angular discordance of strata results in a gap in time of greater than 107 million years in the west, decreasing toward the east to about 39 million years and finally to less than 17 million years. Paleosols and small-scale channels/scours with infilled basal conglomerates are also prominent along the unconformity, as are several mine adits. Because of its abundant geologic features, the Salina Canyon unconformity is a superb teaching and learning space for geoscientists and outdoor naturalists. Utah Geosite—The Salina Canyon Unconformity, a Classic Example of Missing Time Shelley Judge1, Emmett Werthmann1, 3, Cristina Millan2, 4, Michael Braunagel2, 5, Erica Maletic2, 6 1Department of Earth Sciences, The College of Wooster, Wooster, OH 44691 USA; sjudge@wooster.edu 2 School of Earth Sciences, The Ohio State University, Columbus, OH 43210 USA; 3emmett.werthmann@wri.org; 4millan.2@osu.edu; 5braunagel.2@buckeyemail.osu.edu; 6maletic.2@osu.edu Citation for this article. Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E., 2023, Utah geosite—the Salina Canyon unconformity, a classic example of missing time: Geology of the Intermountain West, v. 10, p. 169–183, https://doi.org/10.31711/giw.v10.pp169-183. INTRODUCTION Unconformities are stratigraphic contacts between rock layers where nondeposition or extensive erosion of the underlying older rock unit occurred before depo- sition of the overlying younger rock, indicating a gap in time when sedimentation was not continuous. One type of unconformity—an angular unconformity—is easily identified in the field, because the rock layers above and below the unconformity are not parallel. As ancient surfaces of erosion, unconformities are import- ant to geology because they signify a disruption in the typical, uninterrupted deposition of sedimentary layers. Unconformities help geoscientists understand geologic time by bracketing the age range of geologic events. Salina Canyon, Utah (figure 1), is home to one of the most striking angular unconformities in the state. Many geoscientists travel to see this unconformity just east of the city of Salina and the Salina City Park. The Salina Canyon unconformity exhibits many of the classic fea- tures of unconformities. In addition, the erosional sur- face itself displays relief, and hence, ensuing deposition- al onlap. Geographically it marks the eastern extent in Utah of the Sevier orogeny, a mountain building event from about 170 to 40 million years ago. Previous work has been instrumental in our under- standing of this angular unconformity at Salina Canyon. Dutton (1880) published the earliest description of the Salina Canyon unconformity. The first detailed field- work at Salina Canyon was conducted by Spieker (1946, 1949), first with the U.S. Geological Survey and later as a faculty member at The Ohio State University. Spieker described the field relationships between rocks both below and above the unconformity. In 1947, Spieker 170 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 moved Ohio State’s field camp program from Tennessee to Snow College in Ephraim in Sanpete Valley (Weiss, 1995). For decades, Ohio State’s field camp (still based in Ephraim) has visited the Salina Canyon angular un- conformity, colloquially known to these geoscientists as the “Spieker unconformity.” The Salina Canyon unconformity has been described by numerous additional workers. Gilliland (1963) at- tributed the large-scale folding in the Sanpete-Sevier Valley region to the Sevier orogeny, whereas Witkind (1982, 1983, 1994) considered diapiric action to be the cause of younger units pinching out against the regional large-scale fold. The unconformity has been described and interpreted in field guides (e.g., Lawton and Wil- lis, 1987) and in geologic maps of the area (e.g., Willis, 1986). Additional research characterizing the unconfor- mity and associated bedrock units (Judge and Krissek, 2003; Werthmann, 2018) has added to the story of the unconformity from a stratigraphic and sedimentologic perspective. This paper aims to (1) provide the physical location and geologic setting for the Salina Canyon unconfor- mity, (2) outline the geologic characteristics of this un- conformity, which illustrates many classic stratigraphic and sedimentologic features of erosional surfaces, and (3) summarize recent research on the unconformity re- garding paleosol (ancient soil) formation and the sedi- mentary characteristics along the boundary. LOCATION The Salina Canyon unconformity is in northern Se- Figure 1. (A) Location of Salina Canyon in relation to the city of Salina, I-70, and major state highways. The area in the yellow box is the primary focus of this field guide. Yellow arrows indicate the driving route from downtown Salina to the unconfor- mity. The red “P” denotes possible parking. (B) Inset map shows the transect where the Salina Canyon unconformity is well exposed. Stations 1, 2, and 3 are described in the text. Modified from Google Earth, Utah AGRC. 171 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 vier County, central Utah (figure 1). Outcrops visited in this guide are within the Wasatch Plateau, which is im- mediately east of the Sanpete-Sevier Valley. The uncon- formity is exposed at the southern end of Cedar Moun- tain, which lies a few miles east of Salina, the northern segment of Fishlake National Forest. The unconformity is best exposed just north of Interstate 70 (I-70) at the entrance to Soldier Canyon. The dirt access road to the unconformity is 3.8 miles (6.1 km) east of State Street (U.S. Highway 89 [U.S. 89]) in Salina and just 2 miles (3.2 km) east of Salina City Park. Beautiful exposures of the unconformity can be seen along an east-west transect for a minimum of 1 mile (1.6 km), although the surface continues farther to the east (figure 2A). Several of the most spectacular locations showing image-worthy angular discordance and other exceptional features are located within 0.25 mile (0.4 km) of each other. These stations are described in detail in the Stratigraphy section: • Station 1 (well-developed paleosol): 38°56.049'N., 111°48.584'W. (figure 2B). • Station 2 (mine adit): 38°56.033'N., 111°48.549'W. (figure 2C). • Station 3 (stunning photo opportunity): 38°56.113'N., 111°48.404'W. (figure 2D). SUGGESTED DRIVING DIRECTIONS The Salina Canyon unconformity is easily accessible from any cardinal direction because the nearby city of Salina is at the crossroads of several major state high- ways and I-70 (figure 1). Each of the directions below end on E. Main Street; from there, more detailed direc- tions are provided in the last paragraph of this section. • When driving from the north or south via U.S. 89 or when driving from the west via U.S. Route 50, proceed to the intersection of State Street and E. Main Street in downtown Salina. The famous Mom’s Cafe (voted one of the best places to eat in America and featured in National Geograph- ic Explorer magazine) sits on the southeast cor- ner of this intersection. Proceed east on E. Main Street. (Follow directions below.) • When driving from the west or east via I-70, take exit 56 (Salina). Proceed north on U.S. 50/U.S. 89 (State Street) to the intersection of State Street and E. Main Street in Salina. (Follow di- rections below.) The pull-off for the Salina Canyon unconformity is 3.8 miles (6.1 km) from the intersection of State Street (U.S. 89) and E. Main Street. Drive east on E. Main Street and proceed three blocks to S. 300 E. Turn south on S. 300 E.; a small, wooden sign at this intersection marks this intersection as the turn-off for Salina City Park. S. 300 E. (old Highway 10) gently curves to the southeast and finally to the east. On the south side of the road, visitors will pass Salina City Park, which has two entrances/exits. The pull-off for the Salina Canyon unconformity is 2 miles (3.2 km) ahead. Proceed east to a “Y” junction at 38°55.964'N., 111°48.673'W. Vehicles with high clearance can proceed left at the “Y” junction and park along the dirt track once it flattens out. Vehi- cles lacking high clearance should park on S. 300 E. Do not park too close to the tunnel, which is just ahead, about 520 feet (160 m). Note: visitors have driven too far when the road curves to the south and turns into a one-lane tunnel as it passes under I-70. Visitors who wish to observe a large segment of the Salina Canyon unconformity and Stations 1, 2, and 3 simultaneously can do so from the south side of I-70. When on S. 300 E., drive south under the I-70 tunnel toward the entrance to Soldier Canyon. Proceed imme- diately east on the frontal road before entering Soldier Canyon, and there will be opportunities for a large-scale perspective and transect photographs. STRUCTURAL GEOLOGY Physiographic Provinces Salina Canyon is in a region that exposes the com- plex Mesozoic and Cenozoic geology of central Utah (Spieker, 1936, 1946, 1949; Villien and Kligfield, 1986; Anderson and others, 2001; Schelling and others, 2007). An older compressive phase (145 to 38 Ma) was followed by younger extension (post 38 Ma), creating exceptional structural overprinting (Mattox and Weiss, 1987; DeCelles and others, 1995; Constenius, 1996; De- Celles, 2004; Judge and others, 2005; DeCelles and Coo- 172 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 gan, 2006). The Salina Canyon unconformity lies in the transition zone between the Basin and Range Province to the west and the Colorado Plateau to the east (figure 3; Stokes, 1977). The transition zone is within the Utah hingeline, a zone of structural weakness and repeated tectonic reactivation that runs generally north-south through the state and marks the eastern limit of the Se- vier fold-thrust belt (Stokes, 1976; Ritzma, 1981; Schell- ing and others, 2007) as well as the boundary between thin and thick Paleozoic limestone successions. Contractional Tectonics Deformation from the Sevier orogeny was a result of compressive stress established along the western margin of North America (DeCelles, 2004). In central Utah, the pulses of thrusting spanned about 80 million years (DeCelles and Coogan, 2006). Multiple research (i.e., structural geology and tectonics, stratigraphy, geo- chronology, and geophysics) guides our understanding of the timing of deformation in the region and of the re- gional paleostress orientations (DeCelles and Coogan, 2006; Schelling and others, 2007). The Sanpete-Sevier Valley antiform (SSVA), also called the Salina anticline (Schelling and others, 2007), is one of the dominant geologic features of central Utah and is exposed in the Sanpete and Sevier Valleys (figure 3). A north-plunging, upward arching fold, the SSVA is Figure 2. (A) Aerial photograph of the loca- tion of Stations 1, 2, and 3 in Salina Canyon. View to the northeast. Inset shows a clearer view of the outcrop for Stations 1 and 2. Note the adit in the center of the photograph. Mod- ified from Google Earth. (B) Station 1, where a well-developed paleosol (purplish pink) is present below the unconformity. View to the east. (C) Station 2 depicts the vertical beds of the Jurassic Twist Gulch Formation (average attitude of 028°, 85° SE; N. 28° E., 85° SE) un- der the unconformity and the overlying Pa- leogene fluvial sandstones (average attitude of 320°, 12° SW; N. 40° W., 12° SW). View to the north. (D) Station 3, which is the best-known photogenic locality of the Salina unconformi- ty. Strata here have similar attitudes to Station 2. View to the northeast. 173 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 reported as 50 to 70 miles (80-113 km) long with verti- cal structural relief up to 20,000 feet (6100 m), varying from 2 to 4 miles (3-6 km) wide and opening toward the south (Gilliland, 1963; Anderson and others, 2001). Its location and sheer size play an important role in petro- leum resources of central Utah. Covenant field in Sevier County is along the east limb of the SSVA (Chidsey and others, 2007), and a similar field, Providence, lies to the northeast of Covenant. In these regions, the subsurface geology includes a series of imbricate thrusts, fault-bend folds (with well-developed hanging-wall anticlines), and backthrusts that create a triangle zone within the core of the SSVA (Schelling and others, 2007). Here, the Jurassic Navajo Sandstone and Temple Cap Formation (White Throne Member) are the producing reservoirs, and the Jurassic Arapien Formation acts as the reservoir seal (Chidsey and others, 2007; Schelling and others, 2007; Sprinkel and others, 2011). Several researchers hypothesized that buckling as- sociated with Sevier thrusting was the primary cause of SSVA folding and related deformation. Lateral com- pression is likely the mechanism responsible for the de- formation (Gilliland, 1963; Lawton, 1985; Willis, 1986; Weiss, 1994). Extensional Tectonics The region also experienced a change in the stress regime from east-west crustal shortening to extension. Two distinct episodes of Cenozoic extension overprint previous compressive deformation (Constenius, 1996; Judge and others, 2005). Rowley and others (1998) cor- Figure 3. Simplified map on left shows the major physiographic provinces of Utah, including the relationship of the transition zone to the Basin and Range, Colorado Plateau, and Middle Rocky Mountains provinces. The blue line represents the eastern extent of Sevier orogenesis in Utah, whereas the red line is the axial trace of the SSVA. Modified after Utah Geological Survey (2018). Map on right illustrates the major geomorphic features of the Sanpete-Sevier Valley area. The red line shows the axial trace of the SSVA. 174 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 related these extensional periods with two magmatic ep- isodes: (1) an episode of pre-middle Miocene extension (also referred to as pre-Basin and Range extension), and (2) the more well-known and well-documented Basin and Range extension that began in late Miocene time and continues to this day. Regional structures on the Wasatch Plateau that demonstrate extensional tectonics include normal faults and extensional fractures (open- ing mode joints and calcite veins) that overprint the un- conformity. In addition, the formation of the Wasatch monocline in Salina Canyon is interpreted as a roll-over fold from a half-graben caused by this regional exten- sion (Judge and others, 2005, in press; Judge, 2007). GEOLOGIC HISTORY OF SALINA CANYON The Salina Canyon uniformity captures millions of years of Earth history and tectonic deformation in the transition zone of central Utah. Below is a summary of the geologic history of the area, incorporating both sed- imentation and age dating to create a timeline of events. Stratigraphy and Sedimentation The Middle Jurassic and Cretaceous stratigraphy of central Utah was controlled by mountain building, cre- ating a region of dynamic sedimentation. Depositional packages can be divided into four general time inter- vals: (1) Jurassic foreland basin development (Perkes and Morris, 2011; Sprinkel and others, 2011), (2) Cre- taceous Sevier orogenesis (Villien and Kligfield, 1986; DeCelles and others, 1995; DeCelles and Coogan, 2006; Schelling and others, 2007), (3) Paleogene uplifts and basins (Dickinson and others, 1988), and (4) Miocene to recent regional extension (Mattox and Weiss, 1987; Constenius, 1996; Judge and others, 2005). In Salina Canyon, units representing each of these four intervals are exposed along an east-west transect through the area. Our focus is on the Jurassic, Cretaceous, and Pa- leogene units adjacent to the unconformity (figure 4). Strata in the core of the SSVA were deposited during the Jurassic. The Arapien Formation is interpreted as an open marine, marginal marine, and restricted marine deposit, deposited in a developing foredeep basin as part of the Jurassic Carmel-Twin Creek Seaway (Sprin- kel and others, 2011; Hintze and Kowallis, 2021; D.A. Sprinkel, Utah Geological Survey, written communica- tion, 2023). The age range from palynomorphs for the uppermost member of the Arapien, which is exposed in Salina Canyon, is about 164 to 162 Ma (Sprinkel and others, 2011). Overlying the Arapien is the Jurassic Twist Gulch Formation, which is interpreted as primar- ily an alluvial to shallow marine unit in Salina Canyon, derived from highlands to the west and deposited into the Arapien basin (a subbasin within the regional fore- land basin system; Perkes and Morris, 2011). Its age range from U-Pb geochronology of detrital zircons and supported by palynomorphs is about 165 to 155 Ma (Perkes and Morris, 2011). Cretaceous units comprise the limbs of the SSVA (Spieker, 1946, 1949; Gilliland, 1963; Schelling and others, 2007). Cretaceous units are a thick sequence of clastic sediments, derived from the Sevier orogenic highlands to the west, that were deposited in a foredeep basin (Villien and Kligfield, 1986; DeCelles and others, 1995; DeCelles and Coogan, 2006; Schelling and oth- ers, 2007). These Cretaceous units are tied directly to multiple east-propagating thrusting events (DeCelles and Coogan, 2006). Sedimentation from the orogen- ic highlands to the west record a terrestrial to marine transition from west to east. In Salina Canyon, Creta- ceous units include the Cedar Mountain Formation and the Indianola Group (San Pitch, Sanpete, Allen Valley, and Funk Valley Formations), which range in age from about 145 to 75 Ma (Spieker, 1949; Lawton and Willis, 1987; Sprinkel and others, 1999; DeCelles and Coogan, 2006). The North Horn Formation spans the Creta- ceous/Paleogene boundary (figure 4). Sanpete-Sevier Valley Antiform and the Unconformity The SSVA underwent several pulses of deformation and uplift during its evolution (Gilliland, 1963). Seismic interpretations, along with studies of exposed strata, in- dicated that the SSVA was initiated between about 80 to 70 Ma (Gilliland, 1963; Schelling and others, 2007) after deposition of the Funk Valley Formation (about 80 Ma; Lawton, 1985; Lawton and others, 1997). It may have been actively folding during deposition of the Sixmile Canyon Formation (Lawton and others, 1997), but it 175 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 was uplifted prior to deposition of the basal beds of the North Horn Formation (Schelling and others, 2007). After SSVA formation and erosion, it was covered by a mile-thick (1.5 km) package of lacustrine, fluvial, and volcanic deposits that created unconformable relation- ships with the dipping strata of the SSVA (Spieker, 1946, 1949; Gilliland, 1963). In Salina Canyon, these young- er Paleogene units include the Flagstaff, Colton, Green River, and Crazy Hollow Formations. Volcaniclastics and volcanic units overlie the Crazy Hollow. Due to the presence of unconformities between dipping SSVA strata and overlying strata in central Utah, researchers hypothesize that SSVA uplift was episodic, with each episode marked by an angular unconformity (Gilliland, 1963). Cenozoic Overprinting in Salina For central Utah, Constenius (1996) proposed that south of 40° N. latitude, extensional tectonics (pre-Basin and Range extension due to the gravitational collapse of the Sevier orogenic belt) began between 40 and 35 Ma. Judge and others (2005) constrained the timing of San- pete-Sevier extension to 38.0 ± 0.2 Ma from radiomet- ric dates for an ash-flow tuff in the Aurora Formation, which onlaps the Wasatch monocline flexure adjacent to western Salina Canyon. Cline and Bartley (2007) not- ed evidence for extension in Sevier Valley, south of Sa- lina Canyon. Overall, this extensional regime produced the normal faults that cross-cut the Salina Canyon un- conformity, as mapped by Willis (1986). RECOGNITION OF THE UNCONFORMITY Subaerial unconformities, like the one in Salina Canyon, can be recognized in the field by a suite of characteristics: angular discordance, a gap in the fossil record, karst features (in carbonate settings), paleosol formation, and basal conglomerates (Shanmugam, 1988). The Salina Canyon unconformity is an instruc- tive teaching locality because it contains most of these classic features. Angular Discordance The angular unconformity is easily observed at the outcrop. At several localities (especially Stations 2 and 3), the Jurassic Twist Gulch Formation beds are nearly vertical below the unconformity (figures 2C and 2D). At these photogenic stations, the Twist Gulch is a red, gray, tan/white, and sometimes mottled sequence of in- terbedded sandstones, mudstones, and siltstones. Sand- stones vary from fine to coarse grained, subrounded to subangular, and are well sorted. They contain quartz/ rose quartz, feldspar, biotite, red jasper, opaque/black Figure 4. Generalized stratigraphic column for Salina Can- yon. Jurassic, Cretaceous, and Paleogene strata are exposed along the transect discussed in this manuscript and outlined in figures 1 and 2. Modified from Lawton and Willis (1987). cgl = conglomerate; ls = limestone; mdst = mudstone; sh = shale; slts = siltstone; ss = sandstone. 176 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 lithics, and calcareous cement. The unit contains grad- ed beds and parting lineation. Although determining facing (i.e., younging to the east) is sometimes a chal- lenge for the beginning geology student at Station 2, students recognize the wonderfully preserved ripples, climbing ripples, cross-laminations, and cross-bed- ding at Station 3. To the east of Station 3, progressively younger units are exposed below the unconformity, beginning with the Cretaceous Cedar Mountain Formation and ending with the Funk Valley Formation (figures 5A and 5B). There is an obvious change in the bedding dip of these units from west to east as they progressively pass from nearly vertical to subhorizontal, eventually becoming subparallel to those units that overlie the unconformi- ty. The cause of this gradual change in bedding dip is structural. The dipping Jurassic and Cretaceous units below the unconformity form the eastern limb of the SSVA (Gilliland, 1963; Schelling and others, 2007), and this eastern limb gradually is less steep as you transect west to east through Salina Canyon. Above the unconformity, beds pinch out to the west against the erosional surface, demonstrating onlap. Salina Canyon is an example of a progressive uncon- formity since overlying strata onlap onto the regional paleotopographic high of the SSVA. These strata have a shallow dip, observed from a distance. We interpret the small ledges of sandstone above the unconformity from Station 1 to Station 3 as Colton Formation beds because of their petrographic similarities to known Colton lo- calities north of Salina (north of Stone Quarry and near Willow Creek). The unconformity exhibits slight relief; therefore, in this interpretation the Flagstaff Formation is missing where beds assigned to the Colton rest di- rectly on the unconformity. These basal Colton sandstones are gray to tan, but younger Colton strata include interbedded mudstone, shale, and limestone. Sandstones vary from fine to me- dium grained, subrounded to subangular, and moder- ately to well sorted. They contain quartz/rose quartz, feldspar (plagioclase and microcline), biotite, musco- vite, amphibole, red jasper, malachite, chert, opaque/ black lithics (in thin section, igneous, sedimentary, and metamorphic grains), and calcareous cement with mi- nor iron oxides. The unit has planar cross-bedding, var- ious sizes of trough cross-bedding, loading, pinch-and- swell geometries, and lenticular channel scours. Age Relationships The Salina Canyon unconformity does not repre- sent an equal gap in geologic time along its west to east transect. In the west, this gap in geologic time is greater than 107 million years, decreasing toward the east to about 39 million years and finally to less than 17 million years. The age range for the unconformity can be con- strained by using the ages of the units both below and above the surface. Below the unconformity, the Mid- dle Jurassic Arapien Formation is exposed to the west of Station 1 in Salina Canyon, where they have an age range of about 164 to 162 Ma based on regional paly- nology (Sprinkel and others, 2011). The Arapien shows extreme diapiric deformation (Witkind, 1982, 1983, 1994), thus making for challenging field relationships and interpretations. Beds of the Upper Jurassic Twist Gulch near Station 3 have an age range of 159.5±5.1 Ma (Perkes and Morris, 2011). Above the unconformity near these stations, Colton sandstones are exposed but have not been radiometrically dated. The Colton in Sa- lina Canyon has been assigned a late Paleocene to early Eocene age based on fossil evidence (Fouch and others, 1982; Willis, 1986). Therefore, at Stations 1 and 2, the unconformity spans approximately 107 million years (from ca. 160 to 53 Ma). To the east in Salina Canyon, the age range for the unconformity is less, because younger Cretaceous units are below the surface. The Cedar Mountain Formation and Indianola Group are exposed to the east of the Twist Gulch Formation (figure 5) and have not been radio- metrically dated in Salina Canyon. Their approximate age is based on fossil evidence and relative age relation- ships. East of Station 3 the Flagstaff Formation rests un- conformably on the Sanpete Formation. Here, the un- conformity spans about 39 million years (from the Late Cretaceous to the early Eocene, about 92 to 53 Ma). Still farther to the east (beyond the geologic map limit of fig- ure 5) where the angular unconformity becomes a dis- conformity, beds of the North Horn Formation rest on the Funk Valley Formation. This disconformity spans 177 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 about 17 million years (within the Late Cretaceous; ca. 87 to about 70 Ma; Schelling and others, 2007). Paleosols Paleosols are ancient soils that leave behind traces of past environments. These deposits can provide infor- mation on the climate, depositional environment, and flora/fauna present at the time the soils developed. They are commonly located at unconformities where little information can be inferred about the gap in the rock record (Kraus, 1999). A well-developed paleosol at Sta- tion 1 provides an opportunity to better understand the Salina Canyon area during formation of the unconfor- mity. At Station 1, the strata was divided into five distinct zones based on mottling (after Retallack, 1988), color, texture, burrow abundance, carbonate nodule abun- dance, and stage of paleosol development (figures 6A and 6B; after Retallack, 1997). Other characteristics, such as the presence or absence of drab-haloed root traces or hematite/goethite (after Kraus and Hasiotis, 2006), were also noted. Table 1 summarizes the charac- teristics of each zone. Werthmann (2018) interpreted the paleosol at Sali- na Canyon to be two stacked paleosols that most close- ly resemble vertisols (figure 6B). The older Paleosol 1 comprises zones 1 through 3. It contains an abundance of burrows in zones 2 and 3, implying these portions of the soil were near the surface. Prominent mottling, commonly oriented in vertical streaks, is aligned with the bedding in the underlying Twist Gulch Formation and is attributed to organic matter within the vadose zone (Smith and others, 2008). There is gradual bound- aries between each zones, suggesting high connectivity and internal deformation (Retallack, 1997). Paleosol 2, the younger paleosol, consists of zones 4 and 5. There are fewer burrows and root traces, as well as a decrease in mottling. There is a clear boundary between zones 3 and 4, which marks a change from red mottling to the bulbous structure characteristic of zone 4. Zone 5 is very weakly developed. Figure 5. (A) Aerial photograph of Salina Canyon with superimposed geologic units. Modified from Google Earth; Willis (1986). Yellow stars denote the extent of the cross section in figure 5B. (B) Idealized cross section through Salina Canyon depicting the progressive unconformity, onlap of Paleogene strata onto paleotopography, and the folded SSVA. The cross section was constructed for the time of Flagstaff/Colton deposition and prior to deposition of the Green River Formation and subsequent extensional events. Jtg = Twist Gulch Fm; Kcm = Cedar Mountain Fm; Ks = San Pitch Fm; Ksp = Sanpete Fm; Pgf = Flagstaff Fm; Pgc = Colton Fm; Pggr = Green River Fm; Qms = landslide deposits; Qal = alluvial-fan deposits. Pg represepents Paleogene in the symbol Pgf, Pgc, and Pggr. 178 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 Perhaps the most interesting feature of these pa- leosols is the presence of Naktodemasis bowni (figures 6C and 6D), an adhesive meniscate burrow (AMB) de- fined as “burrows composed of distinct, ellipsoid pack- ets that contain indistinct, meniscate backfill” (Smith and others, 2008). Defined by Smith and others (2008), Naktodemasis has since been noted as a junior synonym of Taenidium (Buatois and others, 2017). This is the first report of AMB at Salina Canyon, and these bur- rows are found without evidence of other organisms in the soil and in the presence of root traces. Smith and others (2008) concluded that AMB were formed by burrower bugs (Hemiptera: Cydnidae) and cicada nymphs (Hemiptera: Cicadae). We conclude that these insects probably produced the burrows in the Station 1 paleosol. Werthmann (2018) further classified these burrow-filled zones as A or upper B soil horizons using estimations of the soil depth where these insects typ- ically live and the moisture content of the soil (Smith and others, 2008). Figure 6. (A) Generalized stratigraphic column of the paleosol at Station 1. The internal features of the strata are depicted in the key: channels/scours, cross-bed- ding, mottling, burrows, root traces, and carbonate nodules. For mottling, the ellipses within each zone are organized by the abundance of color. The largest el- lipse represents the most abundant mot- tling color, whereas the smallest ellipse represents the least abundant color. (B) Station 1 correlated to the stratigraphic column. Paleosol development for each zone is labeled (i.e., strongly developed, moderately developed, etc.). Two stacked paleosols are shown by respective yellow arrows, separated by the dashed yellow line. The blue dashed line near the top of the photograph marks the Salina Canyon unconformity, above which is subhor- izontal Colton strata. View to the east. (C) Line drawing of adhesive meniscate burrow (AMB) showing the morpholo- gy of the burrow. Modified after Smith and others (2008). (D) AMB examples from within zone 3 at Station 1. A pencil tip at the bottom of the photograph pro- vides scale. View to the east. 179 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 Basal Conglomerates On a regional scale, paleotopography on the uncon- formity has been demonstrated by onlap of strata. At outcrop-scale, the erosional surface at the contact is un- dulatory. At Station 2, small-scale channels and scours are present along the unconformity (figure 7A) and are infilled with basal conglomerates. This reflects erosion and paleoflow on the boundary surface. Twist Gulch beds contain small-scale paleoflow in- dicators (figure 7B), whereas the Colton fluvial sand- stones above the unconformity contain large, planar to slightly festoon cross-bedding, as well as small-scale and broad trough cross-bedding (figure 7C). Paleocur- rent analysis for the area near Station 2 shows a mean vector of 321° (N. 39° W.), indicating local paleoflow to the northwest along the regional paleoslope (figure 7D). This data agrees with all measured flow directions in the Colton Formation in the Sanpete-Sevier Valley region (Judge and Krissek, 2003; Judge, 2007). For decades, previous workers concluded that the Colton Formation was sourced primarily from the south-southeast as it onlapped onto the paleotopography of the unconformi- ty (e.g., Stanley and Collinson, 1979; Chapman, 1982; Zawiskie and others, 1982; Dickinson and others, 1986; Judge and Krissek, 2003; Judge, 2007). More recent work concentrated on detrital zircons in the Colton Formation of the Uinta Basin and used U-Pb ages to in- terpret a source area to the south-southwest, suggesting that sediment was transported to central Utah from Ar- izona and California by a paleodrainage system named the California paleoriver (Davis and others, 2010; Dick- inson and others, 2012). Additional Features There are several small mine adits in the area easily viewed along the trace of the unconformity. The geo- graphic area of Stations 1 through 3 is part of the Salina Creek mining district. The Lead Hill Mine is the adit immediately adjacent to Station 2 and was the only pro- ductive mine in the area (Perry and McCarthy, 1976). Historically, small amounts of lead ore was produced from 1908-1912 and in 1944. Perry and McCarthy (1976) identified both beds below the unconformity and the channel sandstones above the unconformity as the mining targets. Minerals identified include: ga- lena, cerussite, sphalerite, pyrite, chalcocite, malachite, azurite, and celestite (Perry and McCarthy, 1976; Willis, 1986). Perry and McCarthy (1976) reported that the mineralized zone of the Lead Hill Mine was 0.5 to 6 feet (0.1-1.8 m) thick and was mined for nearly 600 feet (180 m) underground. GEOLOGIC UNIQUENESS If you are driving through Salina, Utah, then the Sa- lina Canyon unconformity is only a brief stop outside of town. It is well worth the visit for professional geo- scientists, rockhound enthusiasts, and outdoor natural- ists. Below are several reasons why the unconformity is special: 1. Outcrops provide spectacular views of classic features characteristic of unconformities. The outcrops near Stations 1, 2, and 3 are easily acces- sible and do not require much climbing, so most friends and family members can enjoy them. Zone Level of Devel- opment Burrows Root Traces Nodules Ped Type 5 very weakly none identified none identified absent none 4 moderately present present present blocky 3 very strongly present present present granular 2 strongly present present present granular 1 strongly none identified none identified present granular Table 1. Basic characteristics of each of the paleosol zones at Station 1, following the classification schemes of Retallack (1988, 1997). 180 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 2. Salina Canyon is an example of a progressive unconformity. Below the erosional surface, the bedding dips change from vertical in the west to horizontal toward the east. The overlying strata progressively onlap from the east onto the pa- leohigh of the SSVA. When you are at the out- crop on the north side of I-70, it can be difficult to view the “big picture.” However, if you drive south under the I-70 tunnel toward Soldier Canyon and then proceed immediately east on the frontal road, you will have photo opportuni- ties for the entire transect. 3. Salina Canyon geology represents the eastern extent of Sevier orogenesis in the region. Spieker (1949) wrote, “no less than 5,000 and possibly more than 7,000 feet of beds come in and flatten out beneath the unconformity, and the uncon- formity itself passes eastward into a disconfor- mity that is not easy to discern.” Spieker (1949) first noticed this relationship, but since his time, the geosciences have witnessed the advent of plate tectonics and our increased understand- ing of Sevier mountain-building. Salina Canyon can now be better placed in a comprehensive re- gional context. In a short transect, visitors can observe the near vertical deformed strata that were folded as part of the SSVA, flattening to the east. These near horizontal strata represent un- deformed units not impacted by the lateral com- pression of Sevier mountain-building, marking the eastern limit of the Sevier orogeny in Utah. Figure 7. (A) Undulatory erosional surface at Station 2 showing small channel/scour with basal conglomerate. View to the north. (B) Paleoflow and facing indicators in the Twist Gulch Formation are best observed at Station 3. View to the north-northeast. (C) Colton fluvial sandstones above the unconformity at Station 2 show trough cross-bedding. (D) Rose diagram of paleocurrent analysis (mean vector = 321°) of Paleogene fluvial sandstones above the unconformity at Station 2. 181 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 ACKNOWLEDGMENTS This work was supported by The College of Wooster Department of Earth Sciences and The Ohio State Uni- versity School of Earth Sciences Geology Field Camp. We appreciate Wooster students Peter Hurst, Eduar- do Luna, and Mara Sheban for their help in the field. Thanks to A. Lanier (formerly a Wooster student; now Ohio Department of National Resources) and N. Wi- esenburg (Wooster) for assistance in the rock prep lab. We are grateful to Ohio State field camp colleagues W.I. Ausich, D.H. Elliot, W.A. Griffith, L.A. Krissek, and T.J. Wilson, and to, Utah Geological Survey geologists D.A. Sprinkel and G.C. Willis for rich and enjoyable discus- sions on Utah stratigraphy. We welcomed the detailed suggestions from informal reviewers D.H. Elliot (Ohio State), R. Faatz (Snow College), and M.A. Wilson (Col- lege of Wooster), and from formal reviewers R.F. Biek, M. Milligan, and P.J. Nielsen (all Utah Geological Sur- vey). Their time and effort on the manuscript is much appreciated. This manuscript was originally part of the 2019 Utah Geological Association (UGA) Publication 48 edited by M. Milligan, R.F. Biek, and P. Inkenbrandt (all of the Utah Geological Survey), but later transferred to the Geology of the Intermountain West for publica- tion. We would like to thank the editors of UGA Publi- cation 48 for their work on this manuscript. REFERENCES Anderson, R.E., Diehl, S.F., and Barnhard, T.P., 2001, Age and style of deformation and stratal thinning at the tran- sition, Wasatch Plateau to Great Basin, central Utah: Rocky Mountain Geology, v. 36, no. 1, p. 49–80. Buatois, L., Wisshak, M., Wilson, M.A., and Mángano, G., 2017, Categories of architectural designs in trace fos- sils—a measure of ichnodisparity: Earth-Science Re- views, v. 164, p. 102–181. Chapman, D.D., 1982, Sedimentary petrology of the Colton Formation (Upper Paleocene-Eocene), central Utah: Columbus, The Ohio State University, M.S. thesis, 107 p. Chidsey, Jr., T.C., DeHamer, J.S., Hartwick, E.E., Johnson, K.R., Schelling, D.D., Sprinkel, D.A., Strickland, D.K., Vrona, J.P., and Wavrek, D.A., 2007, Petroleum geology of Covenant oil field, central Utah thrust belt, in Wil- lis, G.C., Hylland, M.D., Clark, D.L., and Chidsey, T.C., Jr., editors, Central Utah—diverse geology of a dynamic landscape: Utah Geological Association Publication 36, p. 273–296. Cline, E.J., and Bartley, J.M., 2007, Nature of the Cenozo- ic-Mesozoic contact in Sevier Valley and tectonic impli- cations, in Willis, G.C., Hylland, M.D., Clark, D.L., and Chidsey, T.C., Jr., editors, Central Utah—diverse geology of a dynamic landscape: Utah Geological Association Publication 36, p. 31–45. Constenius, K.N., 1996, Late Paleogene extensional collapse of the Cordilleran foreland fold and thrust belt: Geolog- ical Society of America Bulletin, v. 108, no. 1, p. 20–39. Davis, S.J., Dickinson, W.R., Gehrels, G.E., Spencer, J.E., Law- ton, T., and Carroll, A.R., 2010, The Paleogene California River—evidence of Mojave-Uinta paleodrainage from U-Pb ages of detrital zircons: Geology, v. 38, p. 931–934. DeCelles, P.G., 2004, Late Jurassic to Eocene evolution of the Cordilleran thrust belt and foreland basin system, west- ern U.S.: American Journal of Science, v. 304, p. 105–168. DeCelles, P.G., and Coogan, J.C., 2006, Regional structure and kinematic history of the Sevier fold-and-thrust belt, central Utah: Geological Society of America Bulletin, v. 118, no. 7/8, p. 841–864. DeCelles, P.G., Lawton, T.F., and Mitra, G., 1995, Thrust tim- ing, growth of structural culminations, and synorogenic sedimentation in the type Sevier orogenic belt, western United States: Geology, v. 23, no. 8, p. 699–702. Dickinson, W.R., Inman, K.F., and Lawton, T.F., 1986, Sand- stone detrital modes, central Utah foreland region—strati- graphic record of Cretaceous-Paleogene tectonic evolution: Journal of Sedimentary Petrology, v. 56, no. 2, p. 276–293. Dickinson, W.R., Klute, M.A., Hayes, M.J., Janecke, S.U., Lun- din, E.R., McKittrick, M.A., and Olivares, M.D., 1988, Paleogeographic and paleotectonic setting of Laramide sedimentary basins in the central Rocky Mountain region: Geological Society of America Bulletin, v. 100, p. 1023– 1039. Dickinson, W.R., Lawton, T.F., Pecha, M., Davis, S.J., Gehrels, G.E., and Young, R.A., 2012, Provenance of the Paleogene Colton Formation (Uinta Basin) and Cretaceous-Paleo- gene provenance evolution in the Utah foreland—evi- dence from U-Pb ages of detrital zircons, paleocurrent trends, and sandstone petrofacies: Geosphere, v. 8, no. 4, p. 854–880. 182 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 Dutton, C.E., 1880, Report on the geology of the High Pla- teaus of Utah, with atlas: Department of the Interior U.S. Geographical and Geological Survey of the Rocky Mountain Region, 408 p. Fouch, T.D., Lawton, T.F., Nichols, D.J., Cashion, W.B., and Cobban, W.A., 1982, Chart showing preliminary correla- tion of major Albian to middle Eocene rock units from the Sanpete Valley in central Utah to the Book Cliffs in eastern Utah, in Nielson, D.L., editor, Overthrust belt of Utah: Utah Geological Association Publication 10, p. 267–272. Gilliland, W.N., 1963, Sanpete-Sevier Valley anticline of cen- tral Utah: Geological Society of America Bulletin, v. 74, p. 115–123. Hintze, L.F., and Kowallis, B.J., 2021, Geologic history of Utah: Brigham Young University Department of Geo- logical Sciences Special Publication 10, 266 p. Judge, S.A., 2007, The origin and evolution of the Wasatch monocline, central Utah: Columbus, The Ohio State University, Ph.D. dissertation, 396 p. Judge, S.A., and Krissek, L.A., 2003, Paleocurrent analyses of the Tertiary Colton and Crazy Hollow Formations, central Utah—implications for timing of the Wasatch monocline [abs.]: Geological Society of America Ab- stracts with Programs, v. 35, no. 6, p. 510. Judge, S.A., Wilson, T.J., Elliot, D.H., and Foland, K.A., in press, The Wasatch monocline, central Utah—a pre-Ba- sin and Range extensional structure: Geology of the In- termountain West, v. 10. Judge, S.A., Wilson, T.J., Elliot, D.H., Foland, K.A., and Kilm- er, D.S., 2005, A comparison of paired monoclines in central Utah—origin, timing, and structural style [abs.]: American Association of Petroleum Geologists Annual Convention Program Abstracts, v. 14, p. A69. Kraus, M.J., 1999, Paleosols in clastic sedimentary rocks— their geologic applications: Earth Science Reviews, v. 47, p. 14–70. Kraus, M.J., and Hasiotis, S.J., 2006, Significance of different modes of rhizolith preservation to interpreting paleoenvi- ronmental and paleohydrologic settings—examples from Paleogene paleosols, Bighorn Basin, Wyoming, U.S.A.: Journal of Sedimentary Research, v. 76, p. 633–646. Lawton, T.F., 1985, Style and timing of frontal structures, thrust belt, central Utah: American Association of Pe- troleum Geologists Bulletin, v. 69, no. 7, p. 1145–1159. Lawton, T.F., and Willis, G.C., 1987, The geology of Salina Canyon, in Beus, S.S., editor, DNAG centennial field guide: Rocky Mountain Section, Geological Society of America, p. 265–268. Lawton, T.F., Sprinkel, D.A., DeCelles, P.G., Mitra, G., Suss- man, A.J., and Weiss, M.P., 1997, Stratigraphy and struc- ture of the Sevier thrust belt and proximal foreland-ba- sin system in central Utah—a transect from the Sevier Desert to the Wasatch Plateau: Brigham Young Universi- ty Geology Studies, v. 42, no. 2, p. 33–67. Mattox, S.R., and Weiss, M.P., 1987, Reactivation of a Cre- taceous thrust surface by Basin-and-Range extension, southwestern Gunnison Plateau, central Utah: The Mountain Geologist, v. 24, no. 3, p. 55–65. Perkes, T.L., and Morris, T.H., 2011, Integrating facies anal- ysis, nonmarine sequence stratigraphy, and the first de- trital zircon (U-Pb) ages of the Twist Gulch Formation, Utah, USA—constraining paleogeography and chronos- tratigraphy, in Sprinkel, D.A., Yonkee, W.A., and Chid- sey, T.C., Jr., editors, Sevier thrust belt—northern and central Utah and adjacent areas: Utah Geological Asso- ciation Publication 40, p. 173–192. Perry, L.I., and McCarthy, B.M., 1976, Lead and zinc in Utah: Utah Geological and Mineral Survey Open-File Report 22, p. 336–348. Retallack, G.J., 1988, Field recognition of paleosols: Geolog- ical Society of America Special Papers, v. 216, p. 1–20. Retallack, G.J., 1997, A colour guide to paleosols: New York, John Wiley, 175 p. Ritzma, H.R., 1981, Oiling the “Hingeline:” Utah Geological and Mineral Survey, Survey Notes, v. 15, no. 4, p. 1, 4–6. Rowley, P.D., Cunningham, C.G., Steven, T.A., Mehnert, H.H., and Naeser, C.W., 1998, Cenozoic igneous and tectonic setting of the Marysvale volcanic field and its relation to other igneous centers in Utah and Nevada, in Friedman, J.D., and Huffman, A.C., Jr., editors, Laccolith complexes of southeastern Utah—time of emplacement and tectonic setting workshop Proceedings: U.S. Geo- logical Survey Bulletin 2158, p. 168–201. Schelling, D.D., Strickland, D.K., Johnson, K.R., Vrona, J.P., 2007, Structural geology of the central Utah thrust belt, in Willis, G.C., Hylland, M.D., Clark, D.L., and Chidsey, T.C., Jr., editors, Central Utah—diverse geology of a dynamic landscape: Utah Geological Association Publication 36, p. 1–29. 183 Utah Geosite—The Salina Canyon Unconformity, A Classic Example of Missing Time Judge, S., Werthmann, E., Millan, C., Braunagel, M., and Maletic, E. Geology of the Intermountain West 2023 Volume 10 Shanmugam, G., 1988, Origin, recognition, and importance of erosional unconformities in sedimentary basins, in Kleinspehn, K.L., and Paola, C., editors, New perspec- tives in basin analysis, frontiers in sedimentary geology: New York, Springer-Verlag, p. 83–108. Smith, J.J., Hasiotis, S.T., Kraus, M.J., and Woody, D.T., 2008, Naktodemasis bowni—new ichnogenus and ichnospecies for adhesive meniscate burrows (AMB), and paleoenvi- ronmental implications, Paleogene Willwood Forma- tion, Bighorn Basin, Wyoming: Journal of Paleontology, v. 82, no. 2, p. 267–278. Spieker, E.M., 1936, The orogenic history of central Utah: Science, v. 83, no. 2142, p. 62–63. Spieker, E.M., 1946, Late Mesozoic and Early Cenozoic his- tory of central Utah: U.S. Geological Survey Professional Paper 205-D, p. 117–161. Spieker, E.M., 1949, The transition between the Colorado Plateaus and the Great Basin in central Utah, Guidebook to the geology of Utah 4: Utah Geological Society, 106 p. Sprinkel, D.A., Weiss, M.P., Fleming, R.W., and Waanders, G.L., 1999, Redefining the Lower Cretaceous stratigra- phy within the central Utah foreland basin: Utah Geo- logical Survey Special Study 97, 21 p. Sprinkel, D.A., Doelling, H.H., Kowallis, B.J., Waanders, G., and Kuehne, P.A., 2011, Early results of a study of Middle Jurassic strata in the Sevier fold and thrust belt, Utah, in Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., edi- tors, Sevier thrust belt—northern and central Utah and adjacent areas: Utah Geological Association Publication 40, p. 151–172. Stanley, K.O., and Collinson, J.W., 1979, Depositional history of Paleocene-Lower Eocene Flagstaff Limestone and co- eval rocks, central Utah: American Association of Petro- leum Geologists Bulletin, v. 63, no. 3, p. 311–323. Stokes, W.L., 1976, What is the Wasatch line?, in Hill, J.G., editor, Geology of the Cordilleran Hingeline: Rocky Mountain Association of Geologists Symposium, p. 11–25. Stokes, W.L., 1977, Physiographic subdivisions of Utah: Utah Geological and Mineral Survey Map 43, scale 1:2,400,000. Utah Geological Survey, 2018, Physiographic provinces: On- line, https://geology.utah.gov/popular/general-geology/ utah-landforms/physiographic-provinces/" https://ge- ology.utah.gov/popular/general-geology/utah-land- forms/physiographic-provinces/, accessed December 26, 2018. Villien, A., and Kligfield, R.M., 1986, Thrusting and synoro- genic sedimentation in central Utah, in Petersen, J.A., editor, Paleotectonics and sedimentation in the Rocky Mountain region, United States: American Association of Petroleum Geologists Memoir 41, p. 281–307. Weiss, M.P., 1994, Geologic map of the Sterling 7.5-minute quadrangle, Sanpete County, Utah: Utah Geological Sur- vey Map 159, scale 1:24,000. Weiss, M.P., 1995, Edmund Maute Spieker, 1895-1978: Utah Geological Survey, Survey Notes, v. 27, no. 3, p. 1–5, 12. Werthmann, E., 2018, Reconstructing the Cretaceous pa- leoenvironmental and paleoecological setting of Salina Canyon using paleosols, Sevier County, U.S.A.: Wooster, Ohio, The College of Wooster, B.A. thesis, 54 p. Willis, G.C., 1986, Geologic map of the Salina 7.5-minute quadrangle, Sevier County, Utah: Utah Geological and Mineral Survey Map 83, scale 1:24,000. Witkind, I.J., 1982, Salt diapirism in central Utah, in Nielson, D.L., editor, Overthrust belt of Utah: Utah Geological Association Publication 10, p. 13–30. Witkind, I.J., 1983, Overthrusts and salt diapirs, central Utah: Geological Society of America Memoir 157, p. 45–59. Witkind, I.J., 1994, The role of salt in the structural develop- ment of central Utah: U.S. Geological Survey Profession- al Paper 1528, p. 1–145. Zawiskie, J., Chapman, D., and Alley, R., 1982, Deposition- al history of the Paleocene-Eocene Colton Formation, north-central Utah, in Nielson, D.L., editor, Overthrust belt of Utah: Utah Geological Association Publication 10, p. 273–284.