Geology of Utah’s Parks and Monuments 2010 Utah Geological Association Publication 28 (third edition) D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors

Geology and Geomorphology of

Coral Pink1 Sand Dune1 s State2 Park, Utah3 Richard L. Ford , Shari L. Gillman , David E. Wilkins , William P. Clement , 4 and Kathleen Nicoll

ABSTRACT Coral Pink Sand Dunes State Park, located in southwestern Kane County, Utah, contains a variety of geologic features including one of the largest areas of freely migrating dunes in the Colorado Plateau. The semiarid climate, strong pre- vailing southerly winds, sparse vegetation, and abundant supply of sand-sized sediment make this area susceptible to eo- lian processes. Picturesque exposures of Jurassic rocks are present within the park. The stratigraphic sequence ranges from the Tri- assic-Jurassic Moenave Formation to the Middle Jurassic Carmel Formation. The most widespread bedrock unit exposed within the park is the Navajo Sandstone (Lower Jurassic). The Navajo Sandstone is also widely exposed across the Moc- casin Terrace southwest of the park and is the most likely source for the sand that comprises the dune field. The “coral pink” color of the dune sand is the result of iron-oxide stains on the surface of the sand grains inherited from the source sandstones. Migrating dunes, whose morphology is primarily a function of wind characteristics, include transverse ridges, barchanoid ridges, and a solitary star dune. Dunes influenced or impeded by topographic obstacles or vegetation include climbing dunes, echo dunes, parabolic dunes, vegetated linear dunes, and nebkhas. We divide the dune field into major geomorphic units based on the dominant dune type. A largely stabilized (vege- tated) sand sheet and partially stabilized, poorly organized dunes are present at the southern (upwind) end of the dune field. The active core of the dune field contains transverse ridges and barchanoid ridges. Barchanoid ridges at the north- ern (downwind) end of the active core grade into climbing dunes that ramp up the bedrock escarpment associated with the Sevier fault. The climbing dunes in turn grade into large parabolic dunes that dominate the downwind end of the dune field. Coral Pink Sand Dunes lies within the structural transition zone between the Great Basin section of the Basin and Range province to the west, and the core of the Colorado Plateau to the east. The north-south-trending Sevier fault cuts through the length of the park. The fault trace is marked by a west-facing bedrock escarpment that divides the park into two topographic units (a forested plateau to the east and a relatively low-lying valley floor to the west) and acts as a major control over the accumulation of sand within the dune field. Important events recorded in the geologic features of the park include the Triassic and Jurassic depositional history of the Glen Canyon Group, the Cretaceous to Cenozoic structural history of the Colorado Plateau, and the late Holocene his- tory of the active dunes. Optically stimulated luminescence dates from the active core of the dune field indicate that Holocene eolian deposition began at least 4,000 years ago. Radiocarbon dating of organic materials from an exhumed soil surface suggests a period of landscape stability approximately 500-200 years ago, coincident with the Little Ice Age. Den- drochronologic data from the ponderosa pines in the park, along with historic photographs, indicate the dune field has ex- perienced alternating wet periods and drought since the end of the Little Ice Age, which have influenced vegetation cov- erage and dune activity in the area

1 2Department of Geosciences, Weber State University, Ogden, UT 84408 3Department of Geosciences, Boise State University, Boise, ID 83725 Center for Geophysical Investigation of the Shallow Subsurface,

4 Boise State University, Boise, ID 83725 Department of Geography, University of Utah, Salt Lake City, UT 84112

371 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

INTRODUCTION as aeolian) features and landforms are present within the Coral Pink Sand Dunes, making this an excellent field lab- Geographic Setting oratory in which to learn about the role of wind in shaping the surface of the Earth. Sand dunes occur in two distinct habitats; along the The northern half of the dune field is federal land ad- coasts of seas and rivers, on the one hand, and on the ministered by the Bureau of Land Management (BLM). barren waterless floors of deserts, on the other....Here The southern half of the dune field and adjacent land 2 [in deserts] instead of finding chaos and disorder, the (3,730 acres or 15 km ) comprises Coral Pink Sand Dunes observer never fails to be amazed at a simplicity of form, State Park (CPSDSP), the subject of this paper. The Yel- an exactitude of repetition and geometric order un- lowjacket Canyon 7.5-minute topographic quadrangle known in nature on a scale larger than that of crys- covers the park area. talline structure. The park was established in 1963 and initially visited primarily by small numbers of off-highway vehicle (OHV) — Ralph A. Bagnold, 1942 enthusiasts. Over the years visitation has greatly in- creased and today the majority of park visitors arrive The many geologic wonders of southern Utah include without OHVs to enjoy the scenic beauty of this distinctive a picturesque area of active dunes in southwestern Kane landscape. Park facilities include a 22-unit campground, County, located about 27 miles (43 km) northwest of modern restrooms with hot showers, a boardwalk over- Kanab near the Utah-Arizona border (figure 1). This is one look, and a one-half-mile nature trail. In addition, the park of the largest areas (approximately 5.4 square miles or 14 2 serves as an excellent base for exploring other areas of ge- km ) of freely migrating dunes within the Colorado ologic interest in southern Utah, including Zion and Bryce Plateau Province. This dune field has become known as Canyon National Parks, Cedar Breaks and Grand Stair- the Coral Pink Sand Dunes. The term “coral” in this case case–Escalante National Monuments, and Kodachrome refers to the deep orange pink color of the sand and has Basin State Park. nothing to do with the marine reef-building organisms of Sand Dune Road, a paved road that runs south from the same name. Using a soil-color chart, geologists or soil U.S. Highway 89 through Yellowjacket Canyon, and Han- scientists would formally describe the sand as reddish yel- cock Road, a paved road that runs southwest from U.S. low (5YR 6/8); it is probably a good thing that a geologist Highway 89, provide access to the park (figure 1). Togeth- did not name these dunes. A wide variety of eolian (an ad- er, Sand Dune Road and Hancock Road comprise the state- jective referring to wind activity, derived from the name of designated Ponderosa/Coral Pink Sand Dunes Scenic the Greek god of the wind, Aeolus; also commonly spelled Backway.

14 Y T DIXIE Y N DIXIE T U NATIONAL Long NATIONAL N O FOREST FOREST U Valley C

O Jct. BRYCE CANYON E C

N NAT'L PARK

A S

K F IF ZION CL NK NATIONAL Glendale PI S IFF PARK CL Orderville ITE 9 WH GRAND Mount Carmel STAIRCASE- ESCALANTE UTAH Mount Carmel Jct. NATIONAL d d MONUMENT R R e ck N n o S u c F O n LIF

T D a C H 89 ON

G I d LL CPSDSP n I N M 69 I R a VE H S KANAB S UTAH A W UTAH ARIZONA KAIBAB FREDONIA ARIZONA INDIAN RESERVATION

389 89 Pipe Springs Nat'l Monument

0 5 10 20 30 miles

0 10 20 30 40 km

Figure 1. Location of Coral Pink Sand Dunes State Park (CPSDSP) in Kane County, Utah.

372 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

Topography Topographically, the park can be divided into two dis- tinct units. The eastern half is a forested upland, part of the Moquith Mountains, bounded by a west-facing es- carpment. This escarpment forms the eastern redrock backdrop to the dunes, visible from the dune field and campground to the west (figure 2). This escarpment is fault-controlled (see Structure section) and increases in height from north to south, reaching a maximum of ap- proximately 700 feet (213 m) near the southern end of the park. Although given the name “mountains,” the Mo- quiths are actually a deeply incised plateau that is tilted to- ward the northeast. The highest elevation within the park, 6,977 feet (2,126 m), lies on this plateau. The fault-con- trolled escarpment exposes the same rock units that form the Vermillion Cliffs of the Grand Staircase, which lie gen- erally east and south of the park. For a complete descrip- Figure 2. View to the east from the boardwalk overview of the bedrock tion of the rock units and features that comprise the Grand escarpment that forms the eastern boundary of the dune field. The es- carpment was created by movement along the Sevier fault (see Struc- Staircase of southwestern Utah (see Grand Staircase–Es- ture section) and forms the western boundary of the forested Moquith calante National Monument article in this volume). Mountains in the background. A solitary star dune (see Classic Geo- The western half of the park is relatively low terrain logical Sites section) is visible in the middle ground. lying between the Moquith Mountains and the mesa just northwest of the park. Though unnamed on modern topo- graphic maps, this mesa was called Esplin Point by Gre- Climate and Vegetation gory (1950) in his early regional study, a name we will use Eolian processes are important in areas with strong in this paper. Esplin Point lies at the eastern end of a line prevailing winds, sparse vegetation, and an abundant sup- of cliffs and mesas that extend from Elephant Butte to the ply of sand-sized sediment. This is why most of the park, which collectively form the western expression of world’s major dune fields are found in association with the White Cliffs of the Grand Staircase. Esplin Point has a arid or semiarid climates. The Coral Pink Sand Dunes are maximum elevation of approximately 6,850 feet (2,090 m). no exception, being located within the extensive semiarid Most of the dune field within the park boundaries lies on climatic zone of Utah known as steppe (Köppen climatic this lowland at the base of the scarp bounding the Mo- classification: BS). In Utah, the steppe climate is transi- quith Mountains. Near the northern end of the park the tional between the true arid/desert climates of the Great dunes climb the escarpment and continue to the northeast, Basin and the moister climates of the state’s mountainous forming that part of the dune field on land administered regions (Murphy, 1981). The mean annual temperature in by the BLM. Kanab, Utah, is 54.4° F (12.4° C); the mean annual precipi- The park area is drained by a number of ephemeral tation is 13.3 inches (33.8 cm) (Utah Climate Center, as re- streams whose channels extend from the upland areas, on ported in Pope and Brough, 1996). The distribution of pre- either side of the dune field, to the margin of the dune field cipitation in this area, as evidenced by the data from itself. Channels are largely absent within the dunefield, Kanab, is distinctly bimodal with winter-summer precipi- owing to the high infiltration rates within the dune sand. tation peaks and spring-autumn drought. The closest However, the steep ephemeral channels which drain the weather station to the park with long-term wind data is eastern escarpment act as tributaries to Sand Canyon Las Vegas, Nevada, located approximately 140 miles (225 Wash, lying at the base of the escarpment and along the km) to the southwest. The mean annual surface wind at eastern margin of the dune field. Sand Canyon Wash this location blows from the southwest at 9.3 mph (15.0 flows southward to Kanab Creek and hence to the Col- kph). It is interesting to note that in Las Vegas, the two orado River. The lowest elevation within the park, ap- months of May and June have the greatest average wind proximately 5,620 feet (1,710 m), is in the channel of Sand speed, which coincides with the two driest months of the Canyon Wash where it crosses the park’s southern bound- year in the Kanab area. If this relationship is extrapolated ary. Thus, the total topographic relief within the park is to the Coral Pink Sand Dunes, one would hypothesize that approximately 1,357 feet (416 m). The drainage divide be- eolian activity would generally peak during this time. tween Sand Canyon Wash and Yellowjacket Canyon to the Outside of the distinctive habitats of the dune field it- north is located near the intersection of Hancock and Sand self (see Castle, 1954), the dominant vegetation of the west- Dune roads, approximately 0.9 miles (1.4 km) north of the ern half of the park is typical of pinyon-juniper woodlands park. North of this divide, Sand Dune Road descends Yel- (Pinus edulis, Juniperus spp.) and sagebrush scrub lowjacket Canyon, a north-flowing tributary of the East (Artemisia spp.) of the Colorado Plateau—with one no- Fork of the Virgin River. table and scenic exception. Impressive stands of pon- 373 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah derosa pine (Pinus ponderosa) are present within the more These units have historically been regarded to be Triassic stabilized areas of the dune field. Ponderosa pines also and Jurassic in age; however subsequent stratigraphic dominate the forested upland of the eastern side of the work has shown that the Glen Canyon Group is entirely park. Early Jurassic in age (Pipiringos and O’Sullivan, 1978; Imlay, 1980; and Doelling and others; 1989). The general Previous Investigations stratigraphy and depositional environments of the various Geologic aspects of Coral Pink Sand Dunes have been Jurassic-age bedrock formations exposed in the park area previously reported in more broad-based investigations, are discussed below. A generalized stratigraphic column most notably Gregory (1950), Doelling and others (1989), is presented in figure 5. Anderson and Christenson (1989), and Davis (1999). Cas- Moenave Formation (Jmo) tle (1954) investigated the soil conditions and vegetation communities within the dune field. We are greatly in- In western Kane County, the Moenave Formation (Tri- debted to these researchers, as much of this paper is a syn- assic-Jurassic) overlies the Chinle Formation and the thesis of their work. However, this is the first work to boundary between them was thought to represent a peri- focus specifically on the geology of Coral Pink Sand od of erosion called the J-0 unconformity (Pipiringos and Dunes. One of our major contribution to the geologic O'Sullivan, 1978), but new evidence suggests the contact is knowledge of this area lies in the complete characteriza- conformable and the "J-0" unconformity is within lower tion of the dune field, including its subdivision into dis- Moenave strata (Lucas and other, 2005) (figure 5). The tinct geomorphic units that reflect the relationship be- Moenave Formation is now divided into three members tween surface forms and dominant surface processes. In (in ascending order, the Dinosaur Canyon and Whitmore addition to our literature review, we conducted an analy- Point), The Springdale Sandstone was formerly the upper sis of color aerial photography (scale 1:4,000), augmented member but is now reassigned to the basal Kayenta For- by reconnaissance-level field research during the spring mation (Lucas and Tanner, 2006). Only the upper part of and fall of 1999. the Moenave Formation is exposed in fault blocks of the Subsequent research by the authors has utilized Sevier fault zone south of the park (figure 3). ground-penetrating radar (GPR) to characterize the inter- Thin bedded sandstone and siltstone with bedding nal structure of the dunes (Wilkins and others, 2002; 2003). parallel lamina and low-angle cross-beds in the Dinosaur Wilkins and others (2005) also developed a chronology of Canyon Member and siltstone, fine-grained sandstone, Holocene dune activity based on radiocarbon and optical- thin limestone, and mudstone with freshwater-fish fossils ly stimulated luminescence (OSL) dating. Wilkins and in the Whitmore Point Member suggest a terrestrial depo- Ford (2007) used repeat photography and spatial statistics sitional environment for the Moenave Formation. Specif- to document recent changes in the spatial organization of ic environments probably included lakes, mudflats, and the dune field. fluvial channels as part of a broad floodplain (Doelling and others, 1989). STRATIGRAPHY AND GEOMORPHOLOGY Kayenta Formation (Jk) The generalized geologic map of the park area (figure The Kayenta Formation (Lower Jurassic) uncon- 3) and diagrammatic cross section (figure 4) provide a idea formably overlies the Moenave Formation (figure 5). The of the geology. The general geology of the park can be Kayenta Formation is exposed within the park in the Sevi- characterized as an area of cliff-and-bench topography, de- er fault zone along the base of the escarpment that forms veloped on Mesozoic sedimentary rocks, with a Quater- the western edge of the Moquith Mountains (figure 3). nary dune field at the surface. The oldest Mesozoic unit The Springdale Sandstone Member is also exposed in fault exposed at CPSDSP is the Moenave Formation (Triassic- slices along the base of the Moquith Mountains. The unit, Jurassic). If one were to drill below the present-day dune 160 to 185 feet (49–56 m) thick, consists of very fine field, the Chinle (Upper Triassic) and Moenkopi (Lower grained, pale-reddish-brown sandstone with subordinate Triassic) Formations would be successively encountered amounts of cliff-forming conglomerate (Doelling and oth- below the Moenave Formation (figure 4). The youngest ers, 1989). The Kayenta Formation above the Springdale bedrock unit exposed within the park boundary is the consists primarily of deep red siltstones and mudstones. lowest member of the Carmel Formation (Middle Juras- Smaller amounts of lenticular, medium-grained, trough- sic); the Co-op Creek Limestone Member of Doelling and cross-bedded sandstone are also present. In Kane County, others (1989). The various unconsolidated eolian deposits the thickness of the Kayenta Formation (not including the and active dunes, for which the park is named, are the Springdale Sandstone Member) varies from 190 to 340 feet youngest of all the geologic units in the area. (58–104 m) (Doelling and others, 1989). Mesozoic Rocks Although the Kayenta Formation is mostly fluvial in origin (formed by shifting braided streams), some eolian The picturesque Moenave/Wingate, Kayenta, and sandstone and lacustrine limestone beds, deposited in in- Navajo Formations make up the Glen Canyon Group. terfluve areas, are locally present (Doelling and others,

374 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

Figure 3. Geologic map of the Coral Pink Sand Dunes area in Kane County, Utah (after Sargent and Philpott, 1987). The map legend is included with the cross section shown in figure 4 and identifies the geologic units and symbols used. Note the trace of the Sevier fault running north-south the length of the park.

375 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

Figure 4. Cross section along line A-A’ shown in figure 3. Note the offset in the geologic units created by movement along the Sevier fault zone.

1989). These streams originated in highlands to the east, cross-beds in the upper 10 to 15 feet (3–4.6 m) of the unit. probably the Uncompahgre uplift (Barnes, 1993). These contorted beds have been interpreted to be the re- A thin, though mappable, tongue of sandstone, known sult of slumping on the steep downwind side of dunes or as the Tenney Canyon Tongue, extends eastward from the possibly the result of earthquake-induced liquefaction main body of the Kayenta Formation into the lower por- (Doelling and others, 1989). The Lamb Point Point unit is tion of the overlying Navajo Sandstone (figure 5). The an intertongue of the Navajo Sandstone resulting from portion of the Navajo Sandstone lying between the main widespread eolian deposition in Early Jurassic time. body of the Kayenta Formation and the Tenney Canyon Tenney Canyon Tongue of the Kayenta Formation (Jkt) Tongue is called the Lamb Point Tongue of the Navajo Sandstone (Doelling and others, 1989). These two bedrock The Tenney Canyon Tongue (Lower Jurassic) of the units are also exposed within the park along the trace of Kayenta Formation is pale-reddish brown in color and the Sevier fault (figure 3). comprised of siltstone, mudstone, and very fine thin-bed- ded to laminated sandstone, representing floodplain and Lamb Point Tongue of the Navajo Sandstone (Jnl) channel deposition. It is 90 to 170 feet (27–52 m) thick and The Lamb Point Tongue (Lower Jurassic) is named for typically displays low-angle cross-bedding. This unit has a location on the Vermilion Cliffs south of the park. The sharp contacts with both the underlying Lamb Point unit consists of white, tan, or gray fine-grained sandstone Tongue and the overlying main body of the Navajo Sand- with thick sets of eolian cross-beds, locally greater than 25 stone (Doelling and others, 1989). The tongue thins from feet (7.6 m). The lower and upper contacts with the west to east and pinches out east of Kanab, Utah. Kayenta Formation are sharp. This unit is 90 to 410 feet Navajo Sandstone (Jn) (27–125 m) thick and pinches out to the west of the park. The Lamb Point Tongue contains distinctive contorted The Navajo Sandstone (Lower Jurassic) stands out as

376 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

Figure 5. Stratigraphic column of the Mesozoic bedrock units present within Coral Pink Sand Dunes State Park (modified from Doelling and oth- ers, 1989). the premier formation of the remarkable scenery of the iron oxides. Hematite and goethite cements, produce the Colorado Plateau. In the vicinity of CPSDSP, the Navajo red, orange, and yellow colors; ferrous-iron minerals con- Sandstone is a thick unit, 1,800 to 2,300 feet (549–701 m), of tribute to the brown and occasional green colors (Doelling well-sorted, fine-grained quartz sandstones of varying col- and others, 1989). The diagenetic coloration of the Navajo ors and degrees of cementation. In addition to the cross- Sandstone and related units tells an interesting story of bedded sandstone, the Navajo contains a few lenticular iron cycling, documented in the recent studies of Chan and beds of dense limestone or dolostone. These carbonate others (2000), Chan and Perry (2002), and Beitler and oth- rocks are thought to have accumulated in interdune lakes ers (2003 and 2005). or playas. Being more resistant than the sandstones, the The Navajo Sandstone is the most extensive bedrock limestones and dolostones commonly form benches or unit within the park (figure 3). The lower and upper parts shelves (Doelling and others, 1989). of the formation are more strongly cemented than the mid- The Navajo Sandstone is world-renowned for its elab- dle third and thus are cliff-forming units. The lower cliff- orate array of high-angle cross-beds and stark erosional forming unit is typically reddish in color and, along with forms, including cliffs, domes, and monuments. The light the underlying Kayenta Formation, form the Vermillion colors of the Navajo have been described variously as Cliffs of southwestern Utah. The upper cliff-forming white, tan, buff, salmon, pink, vermillion, brown, red, yel- sandstones typically lack the reddish hues characteristic of low, cream, orange and gray. The sandstone is weakly ce- lower section and thus form the White Cliffs of the Grand mented by calcite or dolomite and varying amounts of Staircase. The lower reddish cliff-forming portion of the

377 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

discovery of local occurrences of petrified trees within the sandstone (presumably spring-fed desert oases) and ani- mal tracks (from vertebrates, including dinosaurs, and in- vertebrates) preserved within the interdune limestone added further evidence of terrestrial deposition (Barnes, 1993; Wilkens and Farmer, 2005; Parrish and Falcon-Long, 2007). Recently BLM geologists confirmed the existence of a substantial dinosaur trackway, known to OHV enthusi- asts for some time, located on BLM land just southwest of Coral Pink Sand Dunes State Park (Mathews and others, 2010). The exposure in Navajo Sandstone, known as the Moccasin Mountain Tracksite, contains tracks from at least six different types of dinosaurs. Temple Cap Sandstone (Jtc) Figure 6. View to the northwest of Esplin Point, part of the White Cliffs. Navajo Sandstone (Jn), Temple Cap Sandstone (Jtc), and the Co- A major unconformity (J-1) marks the top of the Nava- op Creek Limestone Member of the Carmel Formation (Jc) are exposed jo Sandstone (figure 5). Above it is the Temple Cap Sand- in the cliff face. Foreground area is covered by mixed eolian and allu- stone of Middle Jurassic age, named for the East and West vial sediments (Qae). Temple features of Zion National Park. This formation contains, at its base, a prominent reddish, slope-forming Navajo is exposed in the bedrock escarpment east of the siltstone and sandy siltstone, that is 40 to 50 feet (12–15 m) active dunefield, whereas the upper white cliff-forming thick (Sinawava Member). This member is overlain by up portion of the Navajo is exposed in the face of Esplin Point to 150 feet (46 m) of light-gray to tan, cross-bedded, cliff- (figure 6), the prominent mesa located due north of the forming sandstone (White Throne Member) (Doelling and park’s campground. In active gullies and washes along others, 1989). The sandstones and siltstones of the lower the margin of the Coral Pink Sand Dunes, the Navajo Sinawava Member are marine to marginal marine Sandstone—presumably the middle to upper third of the (Sprinkel and others, 2009); the cross-bedded sandstones formation—directly underlies the modern dunes. of the White Throne Member represent aeolian deposition. Deposition of the Navajo Sandstone occurred in a However, the two members are difficult to separate owing large coastal to inland desert, possibly similar to the mod- to the extensive interfingering between the two (Doelling ern Sahara. Orientation of the cross-bedding, essentially and others, 1989). the lithified slip faces of the Jurassic dunes, indicates that The Temple Cap Sandstone is exposed in the central the Jurassic winds blew primarily from the north and portion of the face of Esplin Point north of the camp- northwest (Stokes, 1986; Parrish and Peterson, 1988; Peter- ground (figure 6). This outcrop belt extends to the western son, 1988). The mineralogy of the Navajo Sandstone, 90 to edge of the park (figure 3). 98 percent clear quartz with minor amounts of feldspar, Co-op Creek Limestone Member of the magnetite, tourmaline, staurolite, zircon, garnet, and mica, Carmel Formation (Jc) suggests the source area of the sand was dominated by metamorphic rocks (Doelling and others, 1989). Recent re- The Carmel Formation (Middle Jurassic), named for search on the detrital zircons found within the Navajo Mt. Carmel, Utah, is a lithologically complex unit of lime- Sandstone suggests that the sediments were eroded from stones and sandstones that is subdivided into numerous the Appalachian Mountains, Canadian Shield, and the An- members (Hintze, 1988; Doelling and others, 1989). The cestral Rocky Mountains (Dickinson and Gehrels, 2003). lowermost Co-op Creek Limestone Member caps Esplin The sediments were probably transported westward by Point (figure 6). Co-op Creek beds also occur just west of large rivers and deposited on a coastal plain and shallow- the road near the northern boundary of the park. The Co- water shelf that lay up-wind of the Navajo erg. Geologists op Creek Member consists of a basal siltstone, 10 to 20 feet use the Arabic term “erg” to refer to large (≥ 48 square (3–6 m) thick; however, this unit is similar to the Sinawava 2 miles or 125 km ) desert areas dominated by wind-de- Member of the Temple Cap and is considered the upper posited sand and complex dune forms (smaller areas of part of the Temple Cap (Sprinkel and others, 2009). The dunes, such as the Coral Pink Sand Dunes, are defined as remaining Co-op Creek Members is more than 200 feet “dune fields” [Pye and Tsoar, 1990]). (61+ m) of thin- to medium-bedded light-gray limestone Some early workers (e.g. Stanley and others, 1971) fa- and shaly limestone (Doelling and others, 1989). vored a marine origin for the Navajo Sandstone as large The Co-op Creek Limestone Member of the Carmel offshore sandbars cross-bedded by ocean currents. This Formation conformably overlies the Temple Cap Sand- controversy was essentially put to rest by the work of stone (figure 5). The Carmel Formation in turn is locally Hunter (1976, 1977), who established the criteria for dis- truncated by the unconformity at the base of the Creta- tinguishing eolian and water-laid cross-stratification. The ceous System. Most importantly, the Carmel Formation

378 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

B

Tranverse Barchanoid Barchans Ridges Ridges

Parabolic Linear Dunes Star Dunes Dunes

Figure 7. Morphology of the major types of dunes. Arrows indicate the formative prevailing wind direction (modified from McKee, 1979). marks the end of terrestrial deposition and the return of re- This asymmetric equilibrium profile can be seen in a vari- gional shallow marine conditions to this part of Utah dur- ety of dune types with differing plan forms (figure 7). ing Middle Jurassic time. Subsequent geologic events up- Wind direction and velocity, sand supply, and the lifted the sediments of the Carmel Formation from below presence of topographic obstacles or stabilizing vegetation sea level and raised them to their present elevation of over are the most important factors influencing dune morphol- 6,600 feet (2,011 m) in the vicinity of the park. ogy or type. Considering these factors, it is useful to clas- sify the various dune types as either free dunes, whose Quaternary Deposits and Geomorphology of morphology is primarily a function of wind direction and the Dune Field sediment supply, or impeded dunes whose form is greatly Although the local Jurassic bedrock units are impres- influenced by the effects of vegetation, topographic obsta- sive, the foremost geologic features of this park are the cles, or highly localized sediment sources (Summerfield, various unconsolidated eolian deposits and landforms 1991). Many of the classic dune types are present within that make up the dune field. Whereas the Jurassic forma- Coral Pink Sand Dunes State Park (table 1). tions provide information about ancient depositional envi- Sargent and Philpott (1987) divide the dune field into ronments, the modern dunes are the result of recent and two units: (1) a larger core of active sand dunes and (2) a on-going geological processes during the Quaternary Peri- smaller area of inactive eolian sand along the southern od (the last 2.6 million years of Earth’s history). margin of the dune field. Doelling and others (1989) map For a dune to form, a small patch of sand must first ac- the dune field as a single unit. Neither report identifies the cumulate where the wind speed has been reduced, gener- various types of dunes present in the area. Based on field ally by an increase in surface roughness. Once formed the observations and an analysis of aerial photography, we patch of sand grows by trapping bouncing (saltating) subdivide the active core of the dune field into five (5) map grains that are unable to rebound upon impact as easily as units that reflect the dominant dune type present (figure those that impact harder non-sandy surfaces (an example 8). In addition, we retain the stabilized-sand unit (Qes) of of a positive feedback). As a result of the separation and Sargent and Philpott (1987). These units are described deceleration of the airflow on the lee (downwind) side of below in order of their occurrence, starting at the south the growing sand body, sand accumulates more rapidly end of the dune field. than it is removed by eolian erosion; thus the dune in- Stabilized Eolian Sand Sheet (Qes) creases in size (Summerfield, 1991). A mature dune is thus shaped by the airflow over it and in turn modifies the air- In the southwestern corner of the park, and extending flow. As a result, many dunes attain a characteristic equi- beyond the park boundaries, is an area of wind-blown librium profile of three components: (1) facing upwind is a sand largely stabilized by sagebrush scrub (figure 8). Al- gently inclined (typically 10–15 degrees) backslope, (2) fac- though slipfaces are not preserved on the dune forms, this ing downwind is a steep slipface, standing at the angle of unit does retain some original depositional relief in the repose for sand (generally 30–34 degrees), and (3) separat- form of rolling hills of sand. The western and southern ing the two slopes, a dune crest (Ritter and others, 1995). boundary of this unit is gradational with the mixed eolian

379 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

Table 1. Classification of dune types present at Coral Pink Sand Dunes State Park (modified from Summerfield, 1991). See figure 7 for diagrams of the major dune types.

DUNE TYPE MORPHOLOGY WIND REGIME / MODE OF DEVELOPMENT

A. FREE DUNES Transverse ridge asymmetric ridge, straight crest unidirectional winds Barchanoid ridge asymmetric ridge, sinuous crest unidirectional winds Star dune central peak with 3 or more arms multidirectional winds B. IMPEDED DUNES Blowout elliptical depression localized deflation Parabolic dune u-shaped in plan, arms point upwind locally deflated sand partially anchored by vegetation Nebkha elliptical mound accumulation around a clump of vegetation

Climbing dune sandy ramp on the windward side of accumulation in zone of disrupted airflow large topographic obstruction Echo dune asymmetric ridge parallel to and separated accumulation in zone of disrupted airflow from the windward side of a large topographic obstruction Vegetated linear dune symmetric ridge parallel to prevailing remnant arm of an eroded parabolic dune wind

and alluvial sediments of the valley floor (Qae), which mesa tops and mountain slopes at elevations between support a pinyon-juniper woodland. The interior bound- 6,900 and 8,200 feet (2,100–2,500 m) (Betancourt, 1990). ary with the partially stabilized transverse dunes (Qeps) is Their presence at this relatively low elevation, approxi- sharper, being marked by a distinct change from sage- mately 5,680 to 5,800 feet (1,731–1,768 m), on a basin floor brush scrub to a more sparsely vegetated area. This low- otherwise dominated by a pinyon-juniper woodland, is relief accumulation of eolian sand is best termed a sand curious. Ponderosa pines can tolerate a variety of soil con- sheet. Sand sheets develop under conditions unfavorable ditions, but trees on thin, dry soils are usually dwarfed to dune formation, including a high water table, periodic (Harlow and Harrar, 1968). These trees are not dwarfed surface flooding, and a vegetative cover (Lancaster, 1995). and thus indicate a moisture regime more typical of cooler Each of these conditions, which act to limit the amount of habitats at higher elevations. We speculate that the south- sand available for dune formation, may be significant in ward slope of the dune field, combined with the high hy- this area, especially the cover of vegetation. draulic conductivity of dune sand, produces a localized southward flow of shallow groundwater. The water table Partially Stabilized Dunes (Qeps) and ground surface may converge as one moves south to a Located at the southern (upwind) end of the dune point that is within the rooting depth of ponderosa pines. field and interior of the stabilized sand sheet is an area of Four-year-old trees may have taproots 4 to 5 feet (1.2–1.5 partially stabilized dunes (figure 8). Dune morphology m) long (Harlow and Harrar, 1968). within this map unit is poorly developed and somewhat The ponderosa pines in Qeps are found in various sit- chaotic, but includes small transverse and parabolic-like uations, ranging from being rooted in shallow (less than forms (discussed in detail in following sections). Many of one meter deep over bedrock) cover sheet sand to having the low rolling dunes in this area lack obvious slipfaces. partially buried trunks (up to an estimated 4 meters) in the Topographically, this map unit is transitional, in terms of dunes. The duff from the trees (e.g., needles, branches, dune activity, relief and vegetative cover, between the sta- and cones) appears to add stability to the dune and swale bilized sand sheet (Qes) to the south and the core of active surfaces under and around the trees, and as a result very dunes (Qetd) to the north. little surface dune activity is observed in the stands. The most distinctive characteristic of this geomorphic In the summers of 2002 and 2003, 15 ponderosa in this unit is the presence of scattered ponderosa pines (Pinus section of CPSDSP were cored. Using standard den- ponderosa) amongst the dunes (figure 9). Ponderosa-pine drochronological methods, the cores were processed, forests are best developed on the Colorado Plateau on dated, and the rings visually cross-dated (Stokes and Smi-

380 G

D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

S o y EXPLANATION Cattle Guard Turnout

Overview Area 9 8 . State Park Boundary S . Star Dune U Cattle Guard Turnout o Roads t Overview Area to U.S. 89 Star Dune Geomorphic Units: Roads d Qelp - Large parabolic dunes a o Qecd - Climbing dunes R oad e k R Geomorphic Units: n oc Qemp - Marginal parabolic dunes u nc D Ha d Qetd - Transverse dunes n Qelp - Large parabolic dunes a Qeps - Partially stabilized dunes S Qecd - Climbing dunes Qes - Stabilized sand sheet Qemp - Marginal parabolic dunes Qetd - Transverse dunes Qeps - Partially stabilized dunes Qes - Stabilized sand sheet

Qes Qelp

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Qes e i Figur0 e 8. Geo1morphic map2 of the3 kmCoral Pink Sand Dunes. Trace of the

v e Sevier fault from Sargent and Philpott (1987). See text for detailed de- S criptions of the Quaternary-age map units. ley, 1996). The range of variability in the trees’ environ- The ages of the trees in CPSDSP were compared to a ments, that is, either partially buried or rooted in a swale, published ponderosa tree-ring chronology from Navajo results in different growth-ring responses to the same an- Mountain (Dean and Bowden, 1971), 150 miles to the east nual rainfall variability. Rings in cores collected from trees at roughly the same elevation. Establishment dates of the partially buried in the dunes show wider rings than trees CPSDSP trees correspond broadly with periods of wide in the swales show in the same years; it is thought that the ring widths in the Navajo Mountain trees, indicating they dunes allow greater retention of soil moisture during became established during periods of more effective mois- drought or dry years, and also enhance the growth in wet- ture. A similar comparison against the reconstructed ter years. These differences, though, prevent statistical Palmer Drought Severity Index for the dunes (Cook and cross-dating so these cores are best used to provide mini- others, 2004) also supports tree-establishment dates corre- mum ages of tree and stand establishment (Wilkins and sponding with higher levels of moisture, such as would others, 2005). have existed during the Little Ice Age. Because sampling was stratified towards the oldest A model of stand establishment and dune activity in trees, the majority of those cored are greater than 150 years this part of the dune field can be reconstructed using these old. Minimum dates of establishment range from the oldest observations. Assuming trees need moist conditions and a at 1562 CE to the youngest tree in the last decade of the 20th stable surface to germinate, ages for the oldest trees of 440 Century, indicating the stand may have first become estab- years suggests that activity in this portion of the dune field lished around the beginning of the Little Ice Age, sometime has been climatically limited, at least intermittently, since around the early 15th century (Bradley and Jones, 1993) but the beginning of the Little Ice Age. Those same climatic has continued to survive through the present. conditions would result in sediment-limited conditions, as

381 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

Figure 9. View to the south of ponderosa pines (Pinus ponderosa) growing among partially stabilized dunes (Qeps) at the southern end of the dune field. Figure 10. View to the east of barchanoid ridges within the active core sand does not travel well when conditions are damp (Ko- of transverse dunes (Qetd). Note the steep slipface and sinuous crest of curek and Lancaster, 1999). Additional limitations on the the dune. sand available for transport are imposed by the needle duff observed on the surfaces of the dunes. Finally, as in the dune spacing (up to 1,000 feet or 305 m). These trees have increased in height, the resulting feedback is in- barchanoid ridges display the characteristic alternating creased friction and reduced wind velocity at the surface, linguoid (protruding) and barchanoid (recessed) elements further limiting eolian transport. Thus, dune activity in (figure 7). Owing to the complex airflow over these sinu- this portion of the dune field may have been waning since ous ridges, the barchanoid element of one ridge is com- the establishment of the first trees over 450 years ago. monly aligned with a linguoid element in the adjacent Active Core of Transverse Dunes (Qetd) ridge, creating a complex crestal network referred to as aklé or fishscale patterns (Pye and Tsoar, 1990). A weak The most active portion of the dune field is character- aklé pattern is present at the northernmost end of this map ized by the presence of large, well-developed transverse unit, where the barchanoid ridges impinge upon the dunes, amid very sparse vegetation. These are the signa- bedrock escarpment to the east. ture dunes of the park, and this area is the most popular The convergence between the barchanoid ridges and with the OHV recreationists. This portion of the dune the bedrock escarpment has also produced several echo field lies on the valley floor immediately below the west- dunes (figure 11). Echo and climbing dunes (discussed facing escarpment of the Moquith Mountains (figure 8). below) are examples of topographically controlled dunes, Transverse dunes, generally associated with unidirec- dunes that owe their existence and morphology to interac- tional winds, are asymmetric ridges of sand with a single tions between sand-transporting winds and topographic slipface orientation. The ridge crests are oriented perpen- obstacles (Lancaster, 1995). Echo dunes commonly form in dicular or transverse to the prevailing winds (Summer- front of cliffs (slope > 50 degrees). A vortex forms immedi- field, 1991). The crest of the transverse dunes at CPSDSP ately upwind of the cliff that acts to “sweep out” a corri- have a prominent northwest-southeast orientation, indi- dor between the cliff and the slipface of the dune (Cooke cating a prevailing southwesterly wind, and rise 30 to 50 and others, 1993). The result is the slipface of the dune feet (9–15 m) above their adjacent interdune swales. tends to parallel, or echo, the shape of the cliff face. Echo Two of the three major types of transverse dunes are dunes are best developed where the prevailing wind is present in the Coral Pink Sand Dunes (isolated barchans near perpendicular to the trend of the cliff or escarpment. are not present here). In the southern portion of the map Since the sand-transporting winds within the park strike unit, the dunes have relatively straight crests and are thus the bedrock escarpment obliquely, only the eastern end of classified as transverse ridges (figure 7). The crest-to-crest the barchanoid ridges display this echo morphology. spacing of the ridges is typically 600 to 700 feet (183–213 Small Marginal Parabolic Dunes (Qemp) m). Simple transverse ridges are relatively rare. Appar- ently, minor surface irregularities commonly create Along the western margin of the dune field, approxi- corkscrew-like vortices in the airflow over a transverse mately a quarter mile south of the “cattle guard” area (see ridge. These vortices distort the ridge into a sinuous form Classic Geological Sites section) is an area dominated by called a barchanoid ridge (Summerfield, 1991). The trans- small parabolic dunes (figure 8). Parabolic dunes are U- or verse ridges at CPSDSP grade downwind (to the north) V-shaped in plan with two trailing arms that point upwind into classic barchanoid ridges (figure 10), with an increase (figure 7). Typically, there is a large mound of sand with a

382 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

outcrops of Navajo Sandstone poking through the sand ramp. The area of climbing dunes is more heavily vege- tated than the active core of transverse dunes. The dune morphology is a mixture of poorly developed transverse and parabolic forms. Large Parabolic Dunes (Qelp) Where the climbing dunes reach the top of the escarp- ment they grade into an extensive geomorphic unit domi- nated by parabolic dunes (figure 8). This geomorphic unit, essentially the northern half of the dune field, lies beyond the park on land administered by the BLM. Slipface ori- entation in this part of the dune field indicates a more westerly prevailing wind (S. 50˚ W.) compared to the area of transverse dunes (S. 40˚ W.), probably owing to deflec- tion as the regional wind is funneled through the gap be- tween the eastern escarpment and Esplin Point. The top of Figure 11. View to the east of a barchanoid ridge (modern dune sand) impinging on an outcrop of Navajo Sandstone (Jurassic dune sand). the escarpment appears to act as a flow-expansion point, Local airflow has modified the barchanoid ridge into an echo dune. which reduces wind velocity and promotes deposition. Young field assistant in the lower left corner is approximately 4.6 feet These parabolic dunes are much larger than those (1.5 m) tall. along the margin of the dune field farther south. The com- plex pattern of coalesced and nested dunes in this area, steep slipface at the downwind end of the dune. The out- typical of most occurrences of vegetated parabolic dunes, side slopes of the trailing arms are almost always vegetat- is suggestive of alternating periods of dune migration and ed (Pye and Tsoar, 1990). Parabolic dunes are common in stabilization (Cooke and others, 1993). Here the rows of sand accumulations stabilized by vegetation. Localized coalesced dunes have an average crest-to-crest spacing of disturbance of the vegetative cover and subsequent eolian approximately 1,300 feet (396 m). Large circular to ellipti- erosion can give rise to circular or elliptical depressions cal blowouts are present upwind of many of the dunes. A called blowouts. The eroded sand is then deposited characteristic feature of this part of the dune field is the downwind, near the edge of the disturbed area, as a para- presence of small groves of ponderosa pines in the inter- dune swales. Unlike the ponderosa pines present at the bolic dune (Summerfield, 1991). extreme southern end of the dune field, these occur at The orientation of these parabolic dunes suggest they more typical elevations of 6,100 to 6,500 feet (1,859 to 1,981 are controlled by the same wind regime responsible for the m). large area of transverse dunes. However, these are much Most of the eastern and western boundaries of this ge- smaller features, generally less than 12 feet (3.7 m) in omorphic unit are marked by what is best termed a vege- height. tated linear dune. The western feature is quite evident as Climbing Dunes (Qecd) one travels on Hancock Road. Linear dunes are oriented roughly parallel to the prevailing wind (figure 7). There Wind encountering the windward face of a topo- are many subtypes and their origin is generally poorly un- graphic obstacle, such as a hill or scarp, with a slope of 30 derstood (Cooke and others, 1993). However, these fea- to 50 degrees will be decelerated such that a dune is de- tures are clearly the remnant arms of vegetated parabolic posited upwind of the obstacle. In this situation, unlike an dunes, the noses and other arms having been blown away. echo dune, the fixed eddy or vortex is small or absent. Thus, the dune can bank up against the scarp as a sandy Fluvial Deposits (Qa, Qp, Qae) ramp, creating a so-called climbing dune. When the ramp Besides the eolian deposits and landforms, a variety of attains an equilibrium profile sand can then be carried up unconsolidated water-laid deposits occur in the park area and over it (Cooke and others, 1993). This is the process (figures 3 and 4). The sand and gravel associated with ac- that has taken place at the north end of the park where the tive stream courses are mapped as alluvium (Qa). The active transverse dunes obliquely converge with the fault- largest accumulation of alluvium within the park coin- line scarp of the Sevier fault (figure 8). Figure 12 is a cides with the channel of Sand Wash, located along the ground-penetrating-radar (GPR) transect from the area eastern margin of the dune field. The most widespread that clearly shows a bedrock scarp buried by a ramp of group of unconsolidated deposits in the park area is best climbing dunes. The climbing dunes have a slope of 5 to classified as mixed eolian and alluvial deposits (Qae) (fig- 12 degrees and display well preserved internal slip faces. ure 3). These deposits form when accumulations of wind- The original slope of the bedrock scarp is estimated to blown sand are later reworked by sheetwash or channel have been 45 to 50 degrees, based on the profile of small flooding during torrential rains (Doelling and others,

383 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

SW NE 25 m

20 m

15 m

e climbing dune r u t foresets a 10 m e f

e k i l -

p r a 5 m dune-bedrock interface c S

vertical exaggeration 10x 0 m 100 m 200 m 300 m 400 m 500 m

Figure 12. 500-m GPR transect within the area of climbing dunes (Qecd). The transect crossed bedrock outcrops whose locations were used to in- terpret the subsurface contact between the active dunes and the underlying bedrock (dashed line). Note the internal radar stratigraphy within the climbing dune.

1989). These mixed deposits cover much of the area im- United States with similar sequences and a pronounced mediately west of the dune field, including the park camp- topographic control on dune successions include the Lyn- ground. Unconsolidated gravel deposits lying on bedrock ndyl Dunes of Utah and Great Sand Dunes National Mon- at elevations significantly above the active channels are ument, Colorado (Sack, 1987). pediment or terrace deposits (Qp). These remnant de- The northern subsequence, climbing dunes to para- posits indicate that the valley floor once stood at a higher bolic dunes, reflects a decrease in sand accumulation elevation and has since been lowered by erosion. In the downwind of the source area, owing to a progressive de- park area, pediment gravels are located along both the crease in the sediment supply and an accompanying in- base of the fault-controlled escarpment to the east and the crease in vegetation. Similar controls affect the sequence base of Esplin Point to the west (figure 3). The pediment of dunes at the Killpecker Dunes of Wyoming and White gravels (Qp) are the oldest of the Quaternary deposits in Sands National Monument, New Mexico (Sack, 1987). the area, probably deposited during the Pleistocene Epoch (approximately 2.6 million to 10,000 years ago). All of the STRUCTURAL GEOLOGY other Quaternary units, both aeolian and fluvial, were most likely deposited during the Holocene Epoch, or the Regional Setting last 10,000 years. Coral Pink Sand Dunes State Park (CPSDSP) lies with- Succession of Dune Forms at Coral Pink Sand Dunes in the zone of structural transition between two major ge- The succession of dune types within this dune field ologic or geomorphic provinces of western North Ameri- can be generalized as a downwind sequence (south to ca; the Great Basin section of the Basin and Range north) of stabilized and partially stabilized sand sheets Province, and the Colorado Plateau province (figure 13). and dunes, transverse ridges, barchanoid ridges, climbing These two provinces are distinguished from one another dunes, and parabolic dunes. This is a complex sequence based on differences in their depositional history and style that reflects the interplay between topography, sediment of structural deformation and related differences in their supply, vegetation, and possibly age. The progression of topography. West of Cedar City and the Hurricane Cliffs forms at Coral Pink Sand Dunes is best understood by con- (figure 13) lies the Great Basin, an area characterized by sidering it to be two subsequences with different primary north-south-trending fault-block mountain ranges sepa- controls. rated by broad intervening basins with internal drainage The southern half of the sequence represents adjust- and filled with Tertiary to Quaternary alluvium and lake ments in form and process to a topographically controlled deposits. The boundary between the transition zone and increase in sand accumulation with increasing distance the Great Basin coincides with the trend of the Paragonah, from the source area. This subsequence culminates in the Gunlock, and Grand Wash faults (figure 13). The bound- deposition of the climbing dunes against the fault-line ary between the transition zone and the more stable Col- scarp of the Sevier fault. Other dune fields of the western orado Plateau interior to the east is not as sharply demar-

384 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

EXPLANATION

CPSDSP = Coral Pink Sand

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Figure 13. Basin and Range/Colorado Plateau structural transition zone in southwest Utah (modified from Anderson and Christenson, 1989). Note the location of Coral Pink Sand Dunes State Park along the trace of the Sevier fault. cated, but generally coincides with the Paunsaugunt fault Pink Sand Dunes State Park lies astride the Sevier fault (Anderson and Christenson, 1989). (figures 3 and 13), the central of the three major Basin-and- The transition zone, designated the High Plateaus sec- Range faults of southern Utah. tion (of the Colorado Plateau) by some workers (for exam- ple Davis, 1999), lies between the core areas of the Basin Sevier Fault and Range and Colorado Plateau and thus displays char- The Sevier fault in Utah is the northern portion of a acteristics of both major provinces. In simplest terms, the 300-mile-long (500 km) fault zone that includes the transition zone is that part of the Colorado Plateau that Toroweap and Aubray faults in Arizona (Anderson and was affected by Basin and Range extensional faulting, more characteristic of the style of deformation further to Christenson, 1989; Davis, 1999; Lund and others, 2008). the west. Basin and Range extension was initiated during The fault extends from the Grand Canyon to central Utah, Miocene time (approximately 15 million years ago) and is where it loses its discrete character within Miocene vol- still active today (Davis, 1999). This deformation created canic rocks. The north-south trace of the Sevier fault cuts east-west-tilted structural blocks bounded by widely CPSDSP into two roughly equal halves (figure 3). spaced, north-south-trending, high-angle normal faults; In the vicinity of the park, the Sevier fault strikes ap- namely the Hurricane, Sevier, and Paunsaugunt faults proximately N. 30˚ E. and dips about 75˚ W. It is not a sin- (Anderson and Christenson, 1989; Davis, 1999). Coral gle fault plane but rather a complex zone of braided fault

385 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah segments (figures 3 and 4). As a normal fault, the Sevier pocenter) is located at a major left step in the trace of the fault was created by extensional stresses that produced rel- Sevier fault. The local stress field has apparently created a ative motion along the fault zone such that rocks lying small pull-apart basin that interrupts the northward trans- above the fault plane and west of the fault’s surface trace port of sediment by ephemeral streams in Yellow Jacket moved down relative to the up-thrown block of rocks be- and Sethys Canyons. In order to maintain such a local de- neath the dipping fault zone and east of the surface trace pocenter, active fault movement and related subsidence (figure 4). Strata within the western down-thrown block during the late Quaternary is probably required (Ander- dip very gently (< 5˚) to the north, as evidenced by the ex- son and Christenson, 1989). posures in the face of Esplin Point. The blocks between the Coral Pink Sand Dunes State Park lies within the fault braids, within the up-thrown eastern block, are local- southern end of the Intermountain Seismic Belt (ISB), the ly tilted up to 60˚ (Doelling and others, 1989). Farther east, north-south-trending zone of seismicity extending from away from the fault zone, the strata again display a very northwestern Montana to the Las Vegas, Nevada, area. gentle north to northeast dip. The Wasatch fault of northern Utah is the most infamous Total normal displacement along the Sevier fault zone feature within this zone of active earthquake activity. increases from south to north, ranging from approximate- Earthquakes in the southern portion of the ISB are gener- ly 1,560 feet (475 m) at the Utah-Arizona border to 4,920 ally small to moderate in size, typically less than Richter feet (1,500 m) in southern Sevier County. The stratigraph- magnitude (ML) 4.0, and in many cases are not associated ic displacement within the park is obvious because beds of with the mapped Quaternary faults of the area (Anderson the upper portion of the Navajo Sandstone (Lower Juras- and Christenson, 1989). The largest historic earthquake in sic), exposed on the western down-thrown side of the the vicinity of CPSDSP was the magnitude 6.3 (ML) Pine fault, are abutted against rocks of the up-thrown block Valley earthquake in 1902, located 21 miles (33 km) north ranging from Moenave Formation (Lower Jurassic) to of St. George. Estimated magnitude-5.7 and 5.5+ (ML) lower portions of the Navajo Sandstone (figures 3 and 4). earthquakes occurred east of the park near Kanab in 1887 Anderson and Christenson (1989) estimated the total dis- and 1959, respectively. Compared to the Hurricane fault placement in the vicinity of CPSDSP at 1,560 feet (475 m). 40 miles (64 km) to the west, which generated the 1992 St. This fault offset has produced the prominent west-facing George earthquake (Mw = 5.8), the Sevier fault has had a bedrock escarpment, a fault-line scarp, east of the camp- much lower level of seismicity during historic time. Only ground and main area of active dunes (figure 2). two historic (1900-1985) earthquakes have been recorded Movement along the Sevier fault probably began 15 to along the main trace of the Sevier fault in Utah (Davis, 12 million years ago, corresponding to the beginning of 1999), neither of them within the park. Anderson and Basin and Range deformation in this area (Davis, 1999). Christenson (1989) raise the possibility that the Sevier fault Assessing the recent history of movement along this fault has proven to be difficult (Lund and others, 2008). may be locally deforming by continuous aseismic fault Throughout most of its length in southern Utah, the Sevi- creep, as opposed to large ground-rupturing earthquakes. er fault cuts through Mesozoic-age bedrock. This limits Either way, the low-level earthquake activity, coupled with the opportunity to document the recent history of move- the geomorphic character of the fault-line scarp noted ment, which is typically accomplished through the study above, suggest that the Sevier fault is still active today. of fault scarps and stratigraphic offset within unconsoli- Deformation-Band Shear Zones dated surficial deposits (Quaternary age). However, stud- ies of the Sevier fault north and south of the park area sug- The Navajo Sandstone of southwestern Utah displays gest movements resulting in surface faulting during the a variety of outcrop-scale structures that resemble veins or late Tertiary to Pleistocene (approximately 4 to 0.56 million dikes weathering out in positive relief from their host years ago) (Anderson and Christenson, 1989; Lund and sandstone. These features, called deformation bands, have others, 2008). Two geomorphic aspects of the fault in the been recently studied and analyzed in careful detail by general vicinity of the park provide indirect support for Davis (1999) and Fossen and others (2007). Deformation Pleistocene deformation (Anderson and Christenson, bands are the result of porosity reduction, grain crushing, 1989). First, the west-facing bedrock scarp displays a dis- grain fracturing, and grain flow that occur during the de- tinctive profile, with a moderately sloping rounded upper formation of porous granular materials. Davis recognizes part and steeper cliff-forming lower part. In several places two varieties of deformation bands, cataclastic and non- within the park these two slope elements are separated by cataclastic, both of which are present in the Navajo Sand- a small bench or step in the scarp profile. Anderson and stone within the vicinity of CPSDSP. Cataclastic deforma- Christenson (1989) suggest that recent movement, rather tion bands are closely associated with the regional faults than differential erosion, is responsible for these profile and folds of the area, including the Sevier fault. Slip with- characteristics. The second feature suggestive of recent in these features is indicated by slickensides, and a dis- movement along the fault is the presence of a small but tinctive ladder structure is common. The most distinctive distinctive closed basin at Clay Flat, approximately 1 mile manifestation of cataclastic deformation bands are the for- (1.6 km) north of the park. This area of deposition (de- mation of “fault fins,” triangular blades of sandstone up

386 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28 to 26 feet (8 m) tall (see cover photograph of Davis, 1999). Fault fins are produced by differential weathering and ero- sion; the reduced porosity within the deformation bands increases their resistance. Tilted deformation bands then serve to protect underlying sandstone from erosion (Davis, 1999). The second or noncataclastic type of deformation band is present in almost every outcrop of the uppermost 33 to 50 feet (10–15 m) of the Navajo Sandstone (Davis, 1999). The noncataclastic deformation bands are vein-like structures that weather in positive relief but show minimal evidence of grain-scale fracturing and no slickensides. Davis (1999) concludes that noncataclastic deformation bands formed in Jurassic time by the loading of under- compacted dune sand of the Navajo Sandstone by sedi- ments that now make up the Carmel Formation. Aided by groundwater infiltration, the Navajo sands failed by verti- Figure 14. Noncataclastic deformation bands in a boulder of Navajo cal compaction. The deformation bands mark the zones Sandstone along the campground loop, Coral Pink Sand Dunes State where this volume reduction took place. The uppermost Park. part of the Navajo Sandstone outcrops near the northwest corner of the park. Large blocks of sandstone, apparently formations of the Glen Canyon Group were deposited in a quarried from that area, have been placed at camp sites sedimentary basin that formed between these two high- and along the loop road. “These blocks are museum lands, dominated by terrestrial depositional environ- pieces of . . . noncataclastic deformation bands” (Davis, ments. The Mesocordilleran High blocked moisture-lad- 1999, p. 66) (figure 14). den air masses and served to enhance arid conditions in Utah by creating a rainshadow. The Mesocordilleran High GEOLOGIC HISTORY was also a source area for rivers flowing eastward and car- A complete geologic history of the area around Coral rying sediment into the basin. Pink Sand Dunes State Park (CPSDSP) is beyond the scope Fluvial and lacustrine deposition during theLate-Tri- of this paper. Interested readers should consult Peterson assic and Early Jurassic resulted in the sandstones, silt- and Turner-Peterson’s (1989) overview of the Colorado stones, and freshwater limestone of the Moenave Forma- Plateau, as well as other papers in this volume. We will tion. During this time (approximately 200 to 196 million focus on those geologic events that have specifically left years ago) the North American continent was drifting their mark on the landscape of the park. The most impor- northward through equatorial latitudes. The rock types tant events are the Triassic-Jurassic deposition of the Glen and sedimentary structures preserved within the Moenave Canyon Group (Moenave, Kayenta, and Navajo Forma- Formationsuggest a landscape of low-gradient stream tions), the Cretaceous to Cenozoic structural deformation channels with broad floodplains containing lakes and of the Colorado Plateau, and the Quaternary formation mudflats. Fossil remains of large freshwater fish, similar and evolution of the active dunes. This selective history is to sturgeon, as well as numerous dinosaur footprints and primarily abstracted from the work of Baars (1983), Stokes tracks (see Milner and others, 2006), have been found in (1986), Harris and Tuttle (1990), Patton and others (1991), the Whitmore Point Member. Barnes (1993), Morris and Stueben (1994), Elias (1997), As North America drifted north away from the equa- Davis (1999), and Blakey and Ranney, 2008). tor, the climate in what is now southern Utah became cool- er with wet summers and dry winters (Barnes, 1993). Jurassic Environmental Change Streams deposited silt and sand in channels and on flood- For much of the Paleozoic Era (about 54 to 250 million plains; dinosaurs left their footprints in the damp sedi- years ago), Utah was situated on the western edge of the ments that would become the Kayenta Formation (196 to North American continent and dominated by shallow-ma- 190 million years ago). rine deposition. During Middle Triassic time (245 to 230 Continued northward drift brought a large portion of million years ago) western Utah was cut off from the ocean North America under the influence of subtropical high to the west by a highland barrier, termed the Meso- pressure, resulting in increasing aridity and the establish- cordilleran High (Stokes, 1986), which was located in what ment of a huge Jurassic sand sea or erg. One estimate in- is now eastern Nevada. To the east, in what is now west- dicates that the erg may have covered 256 million square 2 ern Colorado, was another highland area called the Un- miles (6.63 x 105 km ) (Marzolf, 1988). However, the inter- compahgre uplift, an eroded remnant of the Ancestral tonguing of the Kayenta and Navajo Formations repre- Rocky Mountains. Thus, the subsequent Triassic-Jurassic sented by the Lamb Point and Tenney Canyon indicates an

387 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah initial period of time during which fluvial and eolian sys- Tropic Shale and Dakota Sandstone located near Mt. tems vied for dominance in southern Utah. A Jurassic Carmel. Thus, the modern sand dunes of the park lie di- desert, represented by the Lamb Point Tongue, appears to rectly on Lower Jurassic formations, most notably the have advanced from the east, burying and replacing the Navajo Sandstone. The boundary between the two aeolian fluvial channels and floodplains of the Kayenta Forma- units, one lithified and one still moving, represents a hia- tion. The margins of the sandy desert temporarily reced- tus or gap in the stratigraphic record of approximately 180 ed back to the east, replaced by fluvial environments of the million years. Tenney Canyon Tongue. The desert once again advanced and overwhelmed the fluvial landscape. Eolian deposi- Cretaceous to Cenozoic Tectonics tion, represented by the main body of the Navajo Sand- Towards the end of Mesozoic time, and continuing stone, then dominated this area for approximately 15 mil- into the Cenozoic, western North America was subjected lion years (190 to 175 million years ago). to a mountain-building episode known as the Laramide Paleogeographic reconstructions suggest that the erg orogeny (approximately 90 to 50 million years ago). This was situated near the western edge of the continent be- orogeny was the result of compressional stresses generat- tween approximately 18˚ and 25˚ north latitude, under the ed by plate-tectonic convergence between the North influence of onshore north-northwesterly winds associat- American plate and the oceanic Farallon plate to the west. ed with the eastern edge of a subtropical high (Marzolf, Subduction of the Farallon plate, and related folding and 1988; Peterson, 1988; Blakey, 2008; Blakey and Ranney, thrust faulting, gave rise to the Rocky Mountains. The 2008). A shallow marine shelf, estuary, or large lake bor- Colorado Plateau was also greatly affected by this defor- dered the lowland desert on the west. Peterson (1988) sug- mational event (see Davis and Bump, 2009). Compression gests that the source area for the sand was an uplifted area of the Colorado Plateau region was accommodated by in central Montana. Rivers carried sediment westward to basement-cored reverse faulting and associated folding the coast from this upland, longshore currents moved the which produced the Kaibab uplift, the San Rafael Swell, sediment southward, and then waves and northwesterly and the numerous broad anticlines and synclines of the winds delivered the sediment to Utah. Marzolf (1988) sug- Kaiparowits Plateau, among other major structures. Since gests a different source for the sand. He suggests that the beginning of the Laramide orogeny the nearly circular rivers draining northwestward from upland areas in Ari- Colorado Plateau has acted as a coherent structural block zona delivered sediment to the head of the marine embay- and has been uplifted more than 6,600 feet (2,012 m) (Mor- ment to the west, where the silt and clay was winnowed ris and Stubben, 1994). and the sand was returned inland by the onshore winds. One hypothesis (Beghoul and Barazangi, 1989) sug- Navajo Sandstone deposition ended, possibly the re- gests the Farallon plate may have been key to this uplift, sult of climate change, in the vicinity of CPSDSP when becoming attached during subduction to the bottom of the streams, loaded with red mud, flooded the dunes and par- North American plate in the vicinity of the Colorado tially truncated them. For wind-blown sediments to be Plateau. During mid-Cenozoic time the Farallon plate sep- preserved as eolian sandstones, they must be deposited in arated from the North American plate and sank into the an actively subsiding basin. In the case of a coastal erg, if mantle. As the Farallon plate remnant sank, hot material deposition does not keep pace with subsidence, the sea from the asthenosphere rose to fill the void. This material will transgress or flood the lowland. This is what occurred thermally expanded as it rose and some of it intruded the along the western edge of the Navajo erg during Middle lower continental crust, thereby increasing its thickness Jurassic time, resulting in a major unconformity (J-1) (fig- and temperature. The Colorado Plateau is thus seen to ure 6). A shallow seaway extended into southwestern have been uplifted by isostatic compensation resulting Utah from the north. from a combination of heating and increased crustal thick- The mostly marine sediments flooded the region and ness. became the Sinawava Member of the Temple Cap Sand- A second deformational event, Basin and Range ex- stone (Middle Jurassic). Sea level fluctuated during Tem- tension, also had a pronounced effect on the geology of the ple Cap deposition, which allowed eolian deposition to park. This episode of normal faulting and crustal exten- quickly resume producing the White Thrown Member of sion began approximately 15 million years ago, in mid- the Temple Cap Sandstone. Sea level rose again, but this Miocene time, and is still active today (Davis, 1999). There time the sea flooded farther inland completely inundating is no consensus among geoscientists as to the plate-tecton- the erg field resulting in deposition of limestone beds of ic explanation for this extension. Some (for example Stew- the Co-op Creek Member of the Carmel Formation (Mid- art, 1971) suggest that a slowing of convergence between dle Jurassic). the Farallon and North American plates coupled with a Upper Jurassic through Lower Cretaceous beds are rollback of the subducting Farallon plate essentially creat- not present in the vicinity of the park and were probably ed back-arc spreading within the continental crust. Others removed by a long period of uplift and erosion associated (for example Dickinson, 1979) have suggested that the with the Laramide orogeny. The nearest outcrops of Cre- North American plate completely overrode the mid-ocean taceous rocks are poor exposures of Upper Cretaceous ridge along the western boundary of the Farallon plate,

388 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28 thus creating a window in the subducting slab through during the late Pleistocene. Notably, ponderosa pine was which heat and magma from the asthenosphere could rise apparently absent from the Colorado Plateau during this to lift and thin the overlying continental crust. Either way, time, due to a lack of summer moisture and/or a reduction the beginning of this extensional deformation was coinci- of thunderstorm activity and lightning strikes; ponderosa dent with the cessation of subduction along the California pine distribution is in part linked to fire (Betancourt, 1990). coast and the initiation of the transform boundary be- The Pleistocene-Holocene transition on the Colorado tween the North American and Pacific plates marked by Plateau is generally marked by gradual changes in vegeta- the San Andreas fault. tion that indicate warming and a progressive decrease in Whatever its cause, this extensional deformation cre- effective moisture. Macrobotanical remains from the Es- ated the distinctive topography of the Basin and Range calante River basin indicate decreased abundances of mes- Province, including the Great Basin section in Nevada and ophytic plants and an upslope retreat of Douglas fir and western Utah, as well as the three major high-angle nor- spruce (Withers and Mead, 1993). However, the early to mal faults located within the southwestern margin of the mid-Holocene (10,000 to 6,000 years ago) on the Colorado Colorado Plateau—namely the Hurricane, Sevier, and Plateau saw a significant increase in summer precipitation Paunsaugunt faults (figure 13). Movement along the Sevi- (and thunderstorm activity?) (Betancourt, 1990). Pon- er fault has had a major influence on the geologic history derosa pine expanded during this period beyond even its of the park, creating the fault-line scarp that dominates the present distribution. Even during the latter part of this pe- present topography. Without this fault scarp, the varied riod, commonly associated with hot-dry conditions in Mesozoic strata would not be exposed within the park. In other parts of the southwest (the altithermal), the Col- addition, this scarp is in part responsible for the concen- orado Plateau appears to have been wetter than today. tration and accumulation of wind-blown sand at this loca- The most likely explanation is more abundant subtropical tion. moisture from an intensified Bermuda High and south- The uplift of the Colorado Plateau caused a major west monsoon (Betancourt, 1990). Pollen evidence from change in the nature of the dominant geologic processes. Posy Lake on the Aquarius Plateau, north of the park, in- Whereas the Mesozoic Era was dominated by deposition, dicates that the period of enhanced summer precipitation the subsequent Cenozoic geologic history of the Colorado persisted until 5,500 years before present (B.P.) (Shafer, Plateau has been dominated by erosion, producing the 1989). Lake levels were lowest at this site from about 5,000 world-renowned canyonlands and cliff-and-bench topog- to 3,500 years B.P., indicating greater aridity than today. . raphy. This erosion is very evident in the landscape of The oldest dates that we have obtained from the deposits CPSDSP, exposing the picturesque formations of the Glen in the dune field, approximately 4000 yr B.P. (discussed Canyon Group. However, localized eolian deposition dur- below) coincide with this period of regional aridity. ing the Holocene Epoch has created the features for which Late Holocene Geochronology and Dune Activity the park is named. Using a combination of dating methods, including ra- Late Holocene History of the Dune Field diocarbon dating, optically stimulated luminescence The Quaternary Period is subdivided into the Pleis- (OSL) dating, and dendrochronology, we have been able to tocene and Holocene Epochs, with the boundary between reconstruct the changes in the environment and resulting the two occurring approximately 10,000 years ago. The changes in dune activity over the past several millennia Pleistocene is noted for its alternating glacial and inter-gla- preserved within the Holocene stratigraphy of the dune cial conditions. The Holocene is essentially the most re- field (Wilkins and others, 2005; 2007). cent and on-going inter-glacial time period that began Dune migration and erosional lowering of the upwind when the last ice age (the Wisconsin glaciation) ended. surfaces of some of the tallest transverse dunes (Qetd) has Late Pleistocene full-glacial (22,000 to 18,000 years ago) uncovered the tops of several large ponderosa pine snags, conditions on the Colorado Plateau probably inhibited in situ and upright, presumably killed through deep bur- major eolian transport and deposition. Paleobotanical ev- ial by passing dunes. Radiocarbon dating (note: all ages are reported at the 2 level and calibrated using int- idence suggests that late Wisconsin winters were wetter σ and summers were cooler and drier than present (Betan- cal09.14c; Stuiver and Reimer, 1993) of the outer rings of a court, 1990). Drier summers probably reflect a decrease in branch near the top of a ten meter-tall snag gives an age of 14 the availability of subtropical moisture via the southwest death of 190±50 C yr BP (Cal. 1643–1950 CE; Beta 181947); monsoon, whereas wetter winters were caused by a south- ring counting revealed 188 rings, indicating that the stand ern shift in the polar jet and an increased occurrence of Pa- of trees was established for several hundred years before it cific storms and associated frontal precipitation over the was buried. Plateau. The result was coniferous woodlands, including In a swale (approximately 500 meters north of the limber pine, juniper, Colorado blue spruce, Douglas-fir, snags) between active transverse dunes, a fallen and heav- and sagebrush, were present in areas that now support ily weathered ponderosa pine rooted in bedrock has been pinyon-juniper woodlands. The area of the Coral Pink uncovered by dune migration. Radiocarbon dating of the Sand Dunes may have supported a coniferous woodland pith, or center rings, at its base yields an age germination

389 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

14 of 250±40 C yr BP (Cal. 1485–1950; Beta 181943); counting Great Sand Dunes (Colorado; Forman and others, 2006) the rings from the pith to the outer edge of the stem indi- and the Tusayan Dunes (Arizona; Stokes and Breed, 2003). cated a minimum age of 75 years before its death The termination of eolian activity and apparently One hundred meters west of the downed ponderosa, abrupt transition to wetter conditions—as recorded in the recent dune movement has also exhumed a paleosurface waterlain muds over the eolian sediments, expansion of consisting of a muddy soil capping older eolian sediments. the pinyon-juniper woodland into the dunes, and estab- The older sediments are two to three meters of friable lishment of the ponderosa in the dune field—is dated to cross-bedded eolian sand comprised of three units, each the start of the Little Ice Age (LIA). The onset of dune sta- one to two meters thick, all with very similar grain miner- bility corresponds to a period of valley deposition in the alogy, color, and sorting. The uppermost eolian unit is un- surrounding region, as reported by Hereford (2002), as conformably overlain by a more resistant silty mud layer. well as an absence of prolonged, multidecadal drought The mud and soil layer, 0.25 meters thick, exhibits flow (Cook and others, 2004). Hereford (2002) proposes that the features at the base, including rip-up clasts, in the silty ma- accumulation of valley fill resulted from a general absence trix characteristic of a sheetflood deposit. The mud layer of large floods. In the area of the Coral Pink Sand Dunes, is topped by an organic layer consisting of what appears to the Little Ice Age appears to have been a time of landscape be a duff layer from woodland forest floor, including char- stability and diminished eolian transport, interspersed coal and plant macrofossils of juniper berries, cones (Pinus with periods of drought and resurgence of eolian activity edulis), stems and roots in situ, indicating a pinyon-ju- such as that which led to the burial and death of pon- niper woodland had once occupied the site. derosa pines in the active core of the dune field. The ages 14 A method of dating, called optically stimulated lumi- of the snags in the dunes (250±50 and 190±50 C yr BP) nescence (OSL) dating, is a useful tool in desert environ- correspond to a period of eolian activity at the Great Sand ments to date the time since sand was last exposed to sun- Dunes in Colorado (Forman and others, 2006), centered light and buried. Samples of sand for OSL dating were col- around 1800 CE that is attributed to a period of reduced lected at the upper contact of each buried eolian unit precipitation in the region. below the exhumed soil. Dating of the samples record an The last half of the 19th century marked the end of the upper limiting age for the termination of eolian activity Little Ice Age in the Colorado Plateau region (Hereford, and deposition related to that unit. The OSL ages for dep- 2002). Data from Cook and others (2004) and Stahle and osition and burial are in the proper stratigraphic order, others (2007) both report a number of short-term severe with the upper unit terminating 0.51±0.06 ka (1435–1555 droughts during this period; tree rings in cores collected in CE) at a depth of 0.7 m below the surface. The two lower CPSDSP also record these droughts as very narrow rings, units had ages of 2.8±0.22 ka (2.0 m, 1015–525 BCE) and most notably a severe drought in the 1890s that lasted sev- 4.1±0.19 ka (2.8 m, 2205–1905 BCE), respectively (Wilkins eral years. and others, 2007). Radiocarbon dates were also obtained from this site. The end of the Little Ice Age is also marked by a return A sample of the silty mud was collected from the base of of frequent large floods in the region (Hereford, 2002; Ely, the layer and was dated using the bulk organic carbon 1997)—the early 20th century is marked by a prolonged 14 component, yielding an age of 470±50 C yr B.P. (Cal. period of increased moisture termed a “pluvial” by Stahle 1400–1490 CE; Beta 190240). A pinecone embedded in the and others (2007), and is recorded in CPSDSP tree cores as 14 surface soil and duff layer yielded an age of 200±40 C yr very wide rings. The pluvial was followed immediately by B.P. (Cal. 1761–1803 CE; Beta 181944; Wilkins and others, the extreme continental-scale drought of the 1930s known 2005). as “the Dust Bowl” (Stahle and others, 2007). H.E. Grego- The OSL dating of the eolian sand and radiocarbon ry (1950), the first geologist to record a visit to the Coral dating of the exhumed soil, plant matter, and tree snags Pink Sand Dunes, reported a highly active dune field in provide the basis for reconstructing the latest Holocene en- 1937; this activity was likely a response to the drought con- vironments in the Coral Pink Sad Dunes. The lumines- ditions still present from the early part of that decade. Aer- cence dates indicate that eolian activity has been present in ial photos of the dunes acquired in 1957 and 1960 also the park area for at least the last 4000 years, though our show very active dunes, likely a response to the extreme understanding is still limited as to how episodic or per- drought in the southwestern U.S. in the 1950s (Stahle and sistent the earlier periods of eolian activity were. The others, 2007). youngest eolian unit, initiating some time prior to its 500 In the four decades since those photos, 1961–2000, OSL yr BP age, is likely related to one or more of the local climate records record a slight increase in mean an- megadroughts in the western US in the 13th, 14th, and nual precipitation over the previous three decades, early 15th centuries (Oviatt, 1988; Stahle and others, 2007; 1931–1960. In response, the vegetation at the margins of Mensing and others, 2008) and also coincides with the re- the dune field expanded and become more broadly estab- gional abandonment of Anasazi farming settlements (Ben- lished in the dunes—aerial photos acquired in 1997 show son and others, 2007). Eolian activity in the park area dur- a contraction of active dune areas since 1960 (Wilkins and ing that time is broadly similar to activity reported for the Ford, 2007).

390 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

GEOLOGIC UNIQUENESS OF THE PARK Kane County has many aeolian deposits though most are quite small. In addition to the Coral Pink Sand Dunes, Naturalist Freeman Tilden (1970) concluded that sand the Sand Hills, which extend across U.S. 89 between the dunes are nature’s nudes. Indeed, there is something very Sevier fault and Kanab Creek, are large enough to be por- pleasing, even sensual, about the curves and bare contours trayed on regional geologic maps (Sargent and Philpott, of active dunes. Dunes bring to mind romantic adventures 1987; Doelling and others, 1989). Of the many Jurassic in Old World deserts, as well as frontier tales from the sandstone units exposed in the vicinity, the Navajo, Page, American West. It is no wonder then that the Coral Pinks and Entrada Sandstones are thought to be especially pro- Sand Dunes have been used as locations for several Holly- ductive in supplying sand for dunes. Doelling and others wood films: Arabian Nights (1942)—“corny escapist stuff” (1989) suggest that the friable and poorly cemented mid- with an enslaved Sheherazade and a retired Sinbad the dle portion of the Navajo Sandstone provided the bulk of Sailor; Mackenna’s Gold (1969)—“overblown adventure the reddish sand for the Coral Pink Sand Dunes. The red- saga about search for lost canyon of gold,” and One Little dish orange (coral pink) color of the quartz sand is likely Indian (1973)—“AWOL cavalry corporal escaping through inherited from iron oxide grain coatings and cement of the the desert with young Indian boy and a camel” (Maltin, Navajo Sandstone (Chan, 2010, personal communication). 1997). Geologic history, OHV recreation, film making, and Although Gregory (1950) indicates a western source wildlife habitat (to be discussed below)—all make this is (South Mountain) for the sand, the prominent southwest- an interesting, important, and valuable landscape. northeast orientation of the dune field and prevailing southwesterly winds suggests to us a source to the south- Source of the Sand west. The middle pink portion of the Navajo Sandstone is Although the commercial use of the Coral Pink Sand exposed extensively across the Moccasin Terrace, south- Dunes dates to 1942, the earliest scientific treatment of the west of the park. In addition, extensive surficial deposits, dune field is Herbert Gregory’s (1950) description of the primarily deposits of fine-grained sand deposited by dunes in his general survey of the geology and geography mixed alluvial and eolian processes (Qae), cover the Moc- of the Zion National Park area: casin Terrace (Doelling and others, 1989). These unconsol- idated deposits are a likely source for the sand that com- Likewise the disintegrated products from the bare sand- prises the Coral Pink Sand Dunes. stones of South Mountain are carried eastward across This suggested source indicates a very interesting path Moccasin Terrace to form the dunes along the cliffs at through the rock cycle for these sand grains—ancient eo- Sand Canyon and the great sand flats at the head of lian sandstones weathering to produce modern aeolian Three Lakes Canyon. With local accretions en route sediments. Recall that recent studies (Dickinson and these deposits are redistributed over Wygaret Terrace Gehrels, 2003) suggest that rocks as far away as the Ap- and eastward to the base of the Kaiparowits plateau. palachian Mountains were weathered and eroded to pro- During sandstorms great quantities of the finest dust duce sediment that was transported westward by rivers to a marine embayment during Jurassic time. This sediment rise high into the air and move eastward to distant was transported southward by ocean currents, progres- places or after darkening the skies with whirling clouds sively winnowed by wave and tidal action, and eventual- return to the place from which they came. . . . Another ly transported back to land by onshore winds. These sand large area of dunes extends from the head of Cotton- grains were then deposited in large dunes of a lowland wood and Water Canyons northwestward across Sand erg. The dunes were buried by younger sediments and and Yellow Jacket Valleys to the base of the Block Mesas eventually lithified to sandstone, what we now call the near Esplin Point. For a distance of about 8 miles Navajo Sandstone. These eolian sandstones remained northwest of Riggs Spring dunes as much as 200 feet buried for perhaps 125 million years or more. Uplift of the high are nearly stationary; they support growths of Colorado Plateau during the Tertiary Period set the stage piñon and juniper and in wet seasons hold lakes and for the recent and on going weathering and erosion, re- give rise to springs. At the head of Sand Canyon they leasing the sand grains from the ancient rocks. Once are in motion and in their migration are burying and again, perhaps 170 million years latter, the sand grains are eroded and again transported by wind. The modern wind uncovering trees and converting the original escarp- regime has concentrated many of these sand grains in the ment of the Sevier fault into a slope (Gregory, 1950, p. Coral Pink Sand Dunes and continues to slowly transport 188). them to the northeast, to encroach on and bury Jurassic Botanist Elias Castle (1954) may have been the first to Navajo Sandstone outcrops (figure 11). use the term “coral pink” to describe the color of the dunes. His report, probably the first to focus specifically Formation of the Dune Field on the dunes in the park area, summarizes the soil condi- An obvious question is why have these modern eolian tions and their influence on the various vegetation com- sediments been concentrated here? Although no local munities within the dune field. wind data are available, a park brochure (Utah State Parks

391 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah and Recreation, no date) and interpretative signage de- scribe the existence of several regional winds that con- verge in the vicinity of the park. A break in the Vermillion Cliffs south of the park, due to offset on the Sevier fault, likely allows winds to accelerate through the gap between the Moquith and Moccasin Mountains and to entrain loose sediment on the Moccasin Terrace. As the gap widens in the vicinity of the park and the winds impinge upon the bedrock scarp of the Sevier fault, velocity may decrease to allow deposition. Named for an Italian physicist, the ac- celeration of air or liquid as it is forced through a narrow constriction is called the Venturi effect. The southern por- tion of the dune field has a distinct north-south orienta- tion, possibly reflecting the influence of this southerly wind. About 2 miles (3.2 km) north of the southern end of the dune field, in the generally vicinity of the park camp- Figure 15. View to the west of a nebkha (shrub-coppice dune), anchored ground, the orientation of the dune field changes to south- by Wyethia scabra (known commonly as mule ears), within the active west-northeast. This may reflect the influence of prevail- core of transverse dunes (Qetd). Young field assistant is approximate- ing southwesterly winds blowing up from Rosy Canyon, ly 4.6 feet (1.5 m) tall. another wind gap in the Vermillion Cliffs to the southwest. These southwesterly winds may be funneled between the this example is that it is the result of complex airflow along Moccasin Mountains to the south and the Block Mesas, in- the boundary between the dunefield and the vegetated cluding Esplin Point, to the north. The fault-related scarp valley floor. on the eastern edge of the dune field may act to slow these From this vantage point one can look to the south and winds as well, thus initiating deposition at the base of the see the gap between the Moquith Mountains (east, left) scarp. The sand deposited at the base of the scarp is the and Moccasin Mountain (west, right) through which obvious source for the dunes that climb the fault scarp and southerly winds may be accelerated by the Venturi effect. extend approximately 4 miles (6.4 km) northeast onto BLM One can also look to the southwest across much of the land. This secondary sand movement may be facilitated Moccasin Terrace, the probable source area for much of the by an acceleration of the wind as it flows through the nar- sand in the dunes. To the north-northeast is the narrow row, 1-mile (1.6 km) gap between Esplin Point and the gap between Esplin Point and the west-facing escarpment scarp of the Sevier fault. Thus, the Coral Pink Sand Dunes of the Sevier fault, which may facilitate acceleration of the appear to owe their existence to an abundant supply of wind and the transport of sand over the escarpment to fine-grained sand from the Navajo Sandstone and other form the large parabolic dunes at the northern end of the units, strong prevailing southerly and southwesterly dune field (Qelp). Directly east of the overview are the ac- winds, and the decelerating influence of the Sevier fault- tive core of the dune field (Qetd) and the prominent line scarp. Specific data about the local wind regime are bedrock escarpment of the Sevier fault (figure 2). needed to confirm the highly speculative hypothesis pre- Nebkhas sented above. A short nature trail begins beyond the boardwalk LOCATION AND DESCRIPTION overview and traverses into the dune field. Interpretative OF CLASSIC GEOLOGICAL SITES signs along the trail focus on the relationships between vegetation and certain dune forms. Here one can see ex- WITHIN THE PARK cellent examples of nebkhas (also called shrub-coppice Overview Area and Nature Trail dunes), mounds or hummocks of sand trapped by clumps of vegetation (figure 15). Although present in each geo- A parking lot and overview area (figure 8) is located morphic unit of the dune field, nebkhas are particulary on the east side of the campground road between the abundant here along the soutwestern margin of the active ranger station and the campground. Most non-OHV visi- core of transverse dunes (Qetd). tors to the park utilize the boardwalk here to access the On flat surfaces wind velocities may decrease as much dune field. The overview is built atop what is best termed as 50 percent on the downwind side of a bush or shrub a vegetated linear dune (Tsoar and Moller, 1986) that (Francis, 1994). Both the decrease in velocity and the phys- marks the eastern boundary of this portion of the dune ical obstruction of the stems or branches cause deposition field. Unlike the vegetated linear dunes along the margins of wind-blown particles within the plant, including sand, of the dune field to the north, the origin of this feature is silt, organic debris, and nutrients attached to dust nuclei. not obvious. The best interpretation we can provide for Such accumulations may locally improve the soil fertility.

392 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28

Transectransect DistanceDistance (m) 1010 20 30 40 50 6070 80 90 100

5 OHV disturbance?

10 ) ) 15 Dune Trough NE dipping foresets m m ( ( h t p e D 20 Truncation surfaces

25 Dune-Bedrock Interface

30

Figure 16. 100-m GPR transect from the base to crest of the star dune, oriented SW-NE. The dune-bedrock contact was confirmed with a hand auger. The internal radar stratigraphy shows high-angle slip faces and truncation surfaces that record multiple generations of migrating dunes. The re- flectors below the dune-bedrock contact are suggestive of southwest dipping cross-beds within the Navajo Sandstone.

A nebkha will develop where the plants grow fast enough verse dunes, as is the case in the Coral Pink Sand Dunes. to remain on top of the accumulating mound. Nebkhas Star dunes typically achieve heights of 45 to 450 feet may eventually reach 3 to 15 feet (1–3 m) in height and 6 (14-137 m), though some modern star dunes in the Namib to 30 feet (2–5 m) in diameter. Typically they are oval or el- Desert are reported to rise as much as 900 feet (274 m) liptical in plan form. The nebkhas in the Coral Pink Sand above their interdune base (McKee, 1982). The large star Dunes are generally less than 6 feet (2 m) in height. Here, dune at CPSDSP rises approximately 100 feet (30 m) above several different plant species at are adapted to the stress its base and has three sinuous arms and several smaller of progressive burial by wind-blown sand, but Wyethia secondary arms. scabra (mule ears) is by far the most common. Wyethia We were surprised to learn, through the study of aeri- scabra nebkhas are particularly abundant along the mar- al photographs, that the star dune did not exist in 1960, but gins of the dune field. In some areas the relief of the is clearly evident on photographs from 1997 (Wilkins and nebkha has been increased by deflation or eolian erosion others, 2003). The photographs suggest that several trans- of the ground adjacent to the nebkha, locally exposing the verse dunes merged, sometime between 1960 and 1997, to matted and twisted stems and roots of the mound-forming form the lone star dune. We have collected data from sev- plant for a considerable depth below the top of the dune eral ground-penetrating radar (GPR) transects in the area (Castle, 1954). of the star dune since 2000 (Wilkins and others, 2002; 2003). Data quality is excellent with strong reflectors up to Star Dune 60 feet (20 m) below the surface being recorded. The pres- The large dune directly east of the boardwalk ence of unidirectional, high-angle cross-bedding in a GPR overview is an excellent example of a star dune (figures 2 transect that crosses an arm of the star dune (figure 16) and 8). Star dunes commonly have a high central peak supports the transverse-dune parentage of this feature. and three or four curving arms, with multiple slip faces, Most star dunes are thought to be composed of low- to that radiate outward from the central mass. Star dunes moderate-angle ripple-laminated sand (Nielson and Ko- form where winds from more than two directions have curek, 1987). Thus the internal structure and recent histo- contributed to dune growth. They tend to grow vertically, ry of this dune suggests a distinctive mode of star dune rather than migrating horizontally, and contain a greater formation. volume of sand than any other dune type (Lancaster, Barchan (Current Crescent) 1995). McKee (1982) noted that most of the star dunes of the Namib Desert, southwestern Africa, developed from Also visible from the boardwalk overview is a large linear dunes, although some are associated with trans- barchan-like dune, approximately 0.2 miles (0.3 km)

393 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah south-southwest of the star dune. Barchans are character- ginia) and James Hill. The following account is summa- ized by a distinctive crescentic shape in plan view, a steep rized from their work, primarily Knisley and Hill (2001). concave slipface, and “horns” extending downwind from Tiger beetles are predatory insects that prefer open, the central mass of the dune (figure 8). Barchans are the sparsely vegetated habitats, such as sand dunes. Many stable dune type in areas where the directional variability species of the genus Cicindela inhabit dune fields of the of the wind is less than 15˚. Isolated barchans generally western United States and several are endemic to specific occur in areas with a limited sand supply; as the sand sup- dune fields, including the CPSD tiger beetle. Surprisingly, ply increases barchans coalesce to form barchanoid ridges the CPSD tiger beetle appears to regularly inhabit only a (Lancaster, 1995). However, it is puzzling that this dune small portion (approximately 200 acres or 81 ha) of the type so indicative of a unidirectional wind regime is in total dune field, making its geographical range one of the such close proximity to a star dune, indicative of multidi- smallest of any organism known to science. rectional winds. A mitigating factor may be the fact that In 1994 the Southern Utah Wilderness Alliance peti- the isolated barchan at CPSDSP is not a freely migrating tioned the U.S. Fish and Wildlife Service (USFWS) to list dune, but instead has formed largely upwind of a small the CPSD tiger beetle as an endangered species. Current- knob of Navajo Sandstone, which can be observed in the ly, the CPSD tiger beetle is recognized as a candidate for dune’s slip face and GPR transects. We believe this dune listing as an endangered or threatened species. In 1998 is not a true barchan, but instead is best termed a current the USFWS, BLM, Utah Department of Natural Resources, crescent. Current crescents are horseshoe-shaped dunes and Kane County signed an agreement that established a that accumulate where winds are deflected around and 200-acre (81 ha) conservation area within CPSD State Park. over topographic obstacles such as boulders, escarpments, Off-highway vehicles are not permitted in the western or hills (Pye and Tsoar, 1990). Sand is deposited both in portion of the conservation area where most of the tiger front of the obstacle and on either side in two tapering beetles are found. The eastern portion of the conservation wings that resemble the horns of a true barchan. The 1960 area serves as a travel corridor between the southern and and 1997 aerial photography support this interpretation, northern portions of the dune field. An additional 370 acre as the current crescent formed when a migrating trans- (121 ha) conservation area has been established on BLM- verse dune impinged onto and wrapped around the administered land at the extreme northern end of the dune bedrock knob. We speculate that the formation of the cur- field where a small number of dispersing tiger beetles rent crescent may have modified the local wind regime, have been observed. The CPSD tiger beetle was once con- concentrating flow immediately downwind and leading to sidered a subspecies of the Sandy Tiger Beetle (Cicindela the formation of the isolated star dune (Wilkins and oth- limbata). DNA studies published in 2000 (Morgan and oth- ers, 2003). ers, 2000) show it to be a distinct and separate species and highlight the importance of the conservation measures Tiger Beetle Conservation Area taken within the park. (“Cattle Guard Turnout”) Although the range of the CPSD Tiger beetle is quite small, as is its total population, there is no evidence of a Approximately 1.6 miles (2.6 km) north of the ranger progressive decline in CPSD tiger beetles during the time station, on the east side of the road, is a turnout and small that Knisley and Hill (2001) have monitored their popula- parking area locally referred to as the “cattle guard” area tion (1992-present). They believe that the implementation (figure 8). This site provides easy access to the active core of the conservation plan in 1998, which protects the bee- of transverse dunes (Qetd) and the area of small marginal tles’ primary habitat, will promote the long-term existence parabolic dunes (Qemp). From this area one can also see of this species within the Coral Pink Sand Dunes. the barchanoid ridges (figure 10) impinge upon the A puzzling question, for which there is presently no bedrock escarpment, transforming into echo dunes and definitive answer, is why is the distribution of the CPSD climbing dunes. This is also an excellent location to ob- tiger beetle so restricted within the overall dune field? serve the ecological differences between the largely un- Knisley and Hill (2001) point out that there is significant vegetated dune ridges and the vegetated interdune variation in the geomorphology, vegetation, prey insects, swales. Some of the interdune swales are incised, expos- and OHV activity throughout the dune field. They note ing their shallow stratigraphy. This stratigraphy, which in- that the percent vegetation cover in the interdune swales cludes mudcracks and darker, organic-rich (?) layers, indi- of the primary habitat/conservation area is significantly cates cycles of water ponding and desiccation and periods greater than in the swales of other areas of the dune field. of weak soil development within these interdune areas. Probably related, the numbers and types of prey species This general location is also the habitat of the Coral are also significantly greater in the conservation area com- Pink Sand Dunes (CPSD) tiger beetle (Cicindela limbata al- pared to other areas of the dune field. Are these differences bissima), which is only known to inhabit this dune field. related to purely natural factors, such as the geomorphic The biology and ecology of the CPSD tiger beetle has been transition from more active, less vegetated barchanoid largely revealed through the research of entomologists dunes in the southern portion of the dune field to the less Barry Knisley (Randolph-Macon College, Ashland, Vir- active, more vegetated climbing and parabolic dunes to

394 D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors 2010 Utah Geological Association Publication 28 the north? Or are the habitat differences related to OHV ical Society of America); NASA; and The Royal Society activity? Knisley and Hill (2001) suggest that high OHV Lastly, we thank the park staff, especially Rob Quist (for- use contributes to the highly dynamic nature of the south- mer Park Manager) and Carl Davis (retired ranger), for fa- ern portion of the dune field, decreasing the cover of veg- cilitating our field work and, more importantly, for their etation in interdune swales. These questions point out the professional management of this important site. Their job distinctly interdisciplinary (biology and geology in this is not easy as the constituencies who use and value this case) nature of many of the resource and land-use issues or park are diverse. We all owe them our gratitude. concerns now faced by human societies. REFERENCES Final Comments Anderson, R.E., and Christenson, G.E., 1989, Quaternary This paper has attempted to summarize our current faults, folds, and selected volcanic features in the understanding of the particular geomorphic system Cedar City 1°x 2° quadrangle, Utah: Utah Geological known as the Coral Pink Sand Dunes. We know of no and Mineral Survey Miscellaneous Publication 89-6, other dune field in Utah, with the possible exception of the 29 p. Lynndyl Dunes (BLM Little Sahara Recreation Area) (Sack, Baars, D.L., 1983, The Colorado Plateau - a geologic histo- 1987), that contains the diversity of eolian landforms pres- ry: Albuquerque, University of New Mexico Press, 279 ent here. Hopefully we have shown that much can be p. learned at Coral Pink Sand Dunes State Park, both infor- Bagnold, R.A., 1942, The physics of blown sand and desert mally and individually by observant visitor-naturalists dunes: New York, William Morrow & Company, 265 p. and formally and cooperatively by professional scientists. Barnes, F.A., 1993, Geology of the Moab area: Moab, Coral Pink Sand Dunes will continue to provide a natural Canyon Country Publications, 264 p. laboratory in which to observe and discern the complex in- Beghoul, N., and Barazangi, 1989, Mapping high Pn veloc- teractions among atmospheric, geomorphic, and ecologi- ity beneath the Colorado Plateau constrains uplift cal processes. The authors plan to continue research here models: Journal of Geophysical Research, v. 94, p. in the hopes of developing a more complete chronology of 7083-7104. dune formation and evolution during the Holocene. Of Beitler, B., Chan, M.A., and Parry, W.T., 2003, Bleaching of course one doesn’t have to be a scientist to appreciate the Jurassic Navajo Sandstone on Colorado Plateau importance and beauty of this landscape. Laramide highs: evidence of exhumed hydrocarbon supergiants?: Geology, v. 31, p. 1041-1044. To stand in the midst of a sea of great dunes is to have Beitler, B., Parry, W.T., and Chan, M.A., 2005, Fingerprints the sensation of being utterly alone, and vulnerable, in a of fluid flow: chemical diagenetic history of the Juras- world of scorching elements and soul-shaking beauty. sic Navajo Sandstone, southern Utah: Journal of Sedi- mentary Research, v. 75, p. 545-559. — Jan DeBlieu, 1999 Benson, L., Peterson, K., and Stein, J., 2007, Anasazi (pre- Columbian native-American) migrations during the middle-12th and late-13th centuries—were they ACKNOWLEDGMENTS drought induced? Climatic Change, v. 83, p. 187-213. We would like to thank Margie Chan (University of Betancourt, J.L., 1990, Late Quaternary biogeography of Utah), Greg Schlenker (Kleinfelder), and Sarah George the Colorado Plateau, in Betancourt, J.L., Van Deven- (Utah Museum of Natural History) for their careful and der, T.R., and Martin, P.S., editors, Packrat middens - thoughtful review of our manuscript. In addition, the the last 40,000 years of biotic change: Tucson, The Uni- comments and suggestions of editors Doug Sprinkel and versity of Arizona Press, p. 259-292. Paul Anderson greatly improved the final paper. Barry Blakey, R.C., 2008, Pennsylvanian-Jurassic sedimentary Knisley (Randolph-Macon College) generously shared his basins of the Colorado Plateau and Southern Rocky knowledge of tiger beetle ecology and dune environments Mountains, in Miall, A.D., editor, Sedimentary basins and materials related to the park. Stephanie Rodgers do- of the United States and Canada: Amsterdam, Elsevi- nated her time and expertise in preparing some of the fig- er, p. 245-296. ures. Thanks are also due to the staff of the Utah State Blakey, R., and Ranney, W., 2008, Ancient landscapes of the Film Commission for researching the use of the park area Colorado Plateau: Grand Canyon Association, 176 p. as a film location. Stuart Ford provided assistance and Bradley, R.S., and Jones, P.D., 1993, ‘Little Ice Age’ summer comic relief during several of the early field sessions. temperature variations: their nature and relevance to Weber State undergraduates Spencer Riley and Scott recent global warming trends: The Holocene, v. 3, p. Wheeler provided field assistance during the initial GPR 367-376. surveys. We thank the following entities for their funding Castle, E.S., 1954, The succession of vegetation on a south- of our post-2000 studies in the park: Weber State Universi- ern Utah sand dune: Provo, Brigham Young Universi- ty; Boise State University; Gladys W. Cole Award (Geolog- ty, M.S. thesis, 98 p.

395 R.L. Ford and S.L. Gillman Geology of Coral Pink Sand Dunes State Park, Utah

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