CORRELATION AND AGE OF THE NUGGET SANDSTONE AND GLEN CANYON GROUP, UTAH Douglas A. Sprinkel1, Bart J. Kowallis2, and Paul H. Jensen3 ABSTRACT In northeastern Utah, we propose to discontinue use of the term Glen Canyon Sandstone, and propose to in- stead use the term Nugget Sandstone for these rocks, which are exposed in the Uinta Mountains and have been drilled in most of the Uinta Basin. The Nugget Sandstone is also exposed and has been drilled throughout the Sevier thrust belt from northern Utah into central and southwestern Utah. The Glen Canyon Group, which consists of (in ascending order) the Wingate Sandstone/Moenave Formation, Kayenta Formation, and Navajo Sandstone, is ex- posed on the Colorado Plateau and has been drilled along the leading edge of the central and southwestern sectors of the Sevier thrust belt. The Nugget Sandstone is not included as a formation of the Glen Canyon Group, and thus two terms are used for strata above the Ankareh-Chinle Formations and below the Middle Jurassic formations. The term Nugget Sandstone is used where the Kayenta Formation is not recognized and the section consists predomi- nantly of eolianite. Glen Canyon Group is used where the Kayenta is recognized. Aetosaur and dinosaur tracks preserved in the newly applied Nugget Sandstone in the eastern Uinta Mountains and in exposures throughout the Glen Canyon Group include similar assemblages in approximately similar strati- graphic positions, strongly suggesting they are correlative. In addition, well log interpretation suggests that the Nugget Sandstone correlates with the entire Glen Canyon Group and that the Kayenta Formation either pinches out or transitions from fluvial to eolian deposition under the Uinta Basin and along the thrust belt in the Provo salient and south into southwestern Utah. The age of the Nugget Sandstone is Late Triassic to Early Jurassic, which is similar to the Glen Canyon Group, and places the Triassic-Jurassic boundary within the formation/group and not at its base as previously thought. INTRODUCTION of the Kayenta Formation. The Moenave Formation con- sists of fluvial-lacustrine beds in southwestern Utah and intertongues with the Wingate Sandstone (Lucas and oth- Upper Triassic to Lower Jurassic formations are ex- ers, 2005). Geologists have long considered the Nugget posed throughout Utah. In many places they form some and Glen Canyon Sandstones and the Glen Canyon Group of Utah’s most spectacular scenery (figure 1). The rocks to correlate to one another in a general sense because of have also been drilled as primary targets for oil and gas their stratigraphic position and age control on the bound- in the Sevier thrust belt and in the northern Colorado Pla- ing formations. But the correlation between the forma- teau, although in most wells they were drilled to reach tions of the Glen Canyon Group with the Nugget and Glen deeper Paleozoic targets. Names for formations in Utah Canyon Sandstones has been uncertain. In addition, the that lie above the Upper Triassic Ankareh and Chinle For- age of the Nugget Sandstone has been reported as only mations and below Middle Jurassic strata include the Nug- Early Jurassic in some publications (e.g., Coogan and King, get Sandstone, the Glen Canyon Sandstone, and the Glen 2001) and Late Triassic to Early Jurassic in others (e.g., Canyon Group; the Glen Canyon Group consists of the Bryant, 1990; Dover, 1995; Sprinkel, 2006, 2007). Wingate Sandstone (Moenave Formation in southwestern Recent geologic mapping in northeastern Utah Utah), Kayenta Formation, and Navajo Sandstone (Sprin- (Jensen, 2005; Sprinkel, 2006, 2007, 2009), age control on kel, 1994; Hintze and Kowallis, 2009). The terms Nugget some of the poorly age-constrained formations from aeto- and Glen Canyon Sandstones were applied to the same saur and dinosaur tracks and newly discovered dinosaur package of thick eolianites with some minor interbedded bones (Lockley and others, 1992; 2004; Engelmann and fluvial-lacustrine beds. The Glen Canyon Group consists others, 2010; Chambers and others, 2011; Engelmann and of a thick eolianite at its base (Wingate Sandstone) and others, 2011; Lockley, 2011), and systematic interpreta- at its top (Navajo Sandstone) separated by fluvial beds tion of wells logs throughout Utah has shed light on the 1 Utah Geological Survey, P.O. Box 146100, Salt Lake City, UT 84114 Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H., 2011, Correlation and Email: dsprinkel@gmail.com age of the Nugget Sandstone and Glen Canyon Group, Utah, in 2 Department of Geological Sciences, Brigham Young University, Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors, Sevier Provo, UT 84602 thrust belt: northern and central Utah and adjacent areas: 3 Arch Coal Company, P.O. Box 719, Helper, UT 84526 Utah Geological Association Publication 40, p. 131-149. 132 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah Figure 1. Index map showing key geographic and geologic features mentioned in the article. (1) The Nugget and Glen Canyon Group outcrops are shown in darker brown; (2) the approximate axes of Ancestral Rocky Mountain and Laramide uplifts are in red; selected high-angle reverse faults are shown with solid boxes on up-thrown side; (3) oil fields are represented as irregular green polygons and gas fields are represented as irregular red polygons, and (4) the frontal edge and selected thrusts of the Sevier fold and thrust belt are shown with the barbs on the hanging wall. 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. 133 correlation and age of these formations. In this paper, Formation, and that the name Navajo Sandstone should we propose that: (1) the name Nugget Sandstone is the be restricted to areas south of the Uinta Basin. But, while most appropriate name for the thick, massive-weathering, mapping on the south flank of the Uinta Mountains, Kin- cross-bedded eolian sandstone exposed all around the ney (1955) used the term Navajo Sandstone; however, he Uinta Mountains and along parts of the Sevier fold and only applied this formation name to the upper part of the thrust belt, (2) the Nugget Sandstone is correlative to the sandstone where large cross-bed sets were evident. entire Glen Canyon Group (Wingate Sandstone/Moenave MacLachlan (1957) correlated the rocks mapped as Formation, Kayenta Formation, and Navajo Sandstone), Navajo Sandstone along the south flank of the Uinta Moun- and (3) the name Glen Canyon Sandstone, as proposed tains in northeastern Utah with all or part of the Glen Can- by Poole and Stewart (1964b) for northeastern Utah, be yon Group exposed to the south. Poole and Stewart 1964a, discontinued. We will discuss the distribution of and dis- 1964b) renamed the rocks previously mapped as Navajo tinction between the Nugget Sandstone and Glen Canyon in the eastern Uinta Mountains as Glen Canyon Sandstone. Group based on simple criteria, and provide evidence that They were uncertain, however, if their Glen Canyon Sand- both the Nugget Sandstone and Glen Canyon Group are stone represented all formations within the Glen Canyon Late Triassic to Early Jurassic in age. Group or only some formations. Interpretation of avail- able well-log data at that time suggested that the Wingate Sandstone thickened northward from southern Utah as the REVIEW OF PREVIOUS STRATIGRAPHIC Kayenta and Navajo thinned (Poole and Stewart, 1964a, NOMENCLATURE 1964b). They speculated that if the thickness trend con- tinued as suggested from the well-log interpretation, their The name for the Upper Triassic to Lower Jurassic suc- Glen Canyon Sandstone probably correlated with the Win- cession of mostly eolianites in Utah has changed several gate Sandstone and possibly a much thinned Navajo, with times. Powell (1876) used the name White Cliff Sandstone the Kayenta wedging out before the section surfaced along for the massive, white, cliff-forming sandstone found in the eastern Uinta Mountains. Poole and Stewart (1964b) both northern and southern Utah. This name was still in also considered that the Kayenta Formation and Navajo use in the eastern Uinta Mountains area in 1910 when Gale Sandstone may have been removed by a pre-Bajocian un- (1910) described it as a massive, light-gray to light-orange conformity. They also stated that this new Glen Canyon sandstone that “everywhere exhibits false [cross-bedded] Sandstone was equivalent to the Nugget Sandstone of the stratification in many directions and many angles.” To the western Uinta and Wasatch Mountains, but chose not to north and west in Wyoming, however, the name Nugget use the name Nugget because “the name Nugget [was] op- Sandstone had entered the stratigraphic nomenclature for posed by many geologists because of lithologic differences rocks of very similar age and character (Veatch, 1907; Gale between the Nugget in the type area in Wyoming and that and Richards, 1910; Boutwell, 1912). in the Uinta Mountains.” Unfortunately, Poole and Stewart In southern Utah, Arizona, and New Mexico, at about (1964a, 1964b) did not provide references to show which the same time, Gregory (1917) was proposing names for geologists were opposed to the name Nugget Sandstone several Mesozoic formations. A number of workers stud- and did not outline in their paper what lithologic differ- ied these formations and it was generally accepted that ences were problematic between the Nugget in the type the Nugget Sandstone in Wyoming and northern Utah was area and the rocks they called the Glen Canyon Sandstone equivalent to all or part of Powell’s White Cliff Sandstone in the eastern Uinta Mountains. and to a second formation called the Vermilion Cliff Sand- The name Nugget Sandstone was never completely stone in southern Utah and Arizona (Mansfield, 1920; abandoned for these eastern Uinta Mountain rocks (e.g., Branson, 1927; Dobbin and Reeside, 1927; Lee, 1927; High and Picard, 1975; Knapp, 1976; Doelger, 1987; Peter- Mansfield, 1927; Reeside, 1929). Starting in the 1930s, son, 1988), and recently it has been used in several pub- however, workers began to restrict the correlation of the lished geologic reports and in presentations at profession- Nugget Sandstone in the north to just the Navajo Sand- al geologic meetings (Jensen, 2005; Jensen and Kowallis, stone in the south (Gregory and Moore, 1931; Baker and 2005; Jensen and others, 2005; Sprinkel and others, 2005; others, 1936; Heaton, 1939; Kinney, 1955; Stokes and oth- Hintze and Kowallis, 2009; Engelmann and others, 2010; ers, 1955). Parry and Blamey, 2010; Chambers and others, 2011; It was also in the 1930s when the term Glen Canyon Engelmann and others, 2011). The Nugget Sandstone has first entered the stratigraphic nomenclature (Baker and also been mapped from the western Uinta Mountains and others, 1927). The Navajo Sandstone, along with strata northern Utah sector of the Sevier thrust belt eastward called the Todilto(?) Formation, and the Wingate Sand- into the eastern Uinta Mountains (Bryant, 1990, 1992; stone were determined to be one conformable package of Jensen, 2005; Sprinkel, 2006, 2007; Haddox and others, sedimentary rocks and they were grouped together into 2010a, 2010b). the Glen Canyon Group (Gregory and Moore, 1931). Rocks We believe the lithologic similarities between the Glen within the group called Todilto(?) were soon shown to not Canyon Sandstone in the eastern Uinta Mountains and the be equivalent to the type Todilto Limestone and were re- Nugget Sandstone in its type locality in the Sevier thrust named the Kayenta Formation (Baker and others, 1936). belt of southwestern Wyoming are strong and that the To the north, nomenclature in the Uinta Mountains Nugget Sandstone can be easily mapped from there into was still in flux when Imlay (1952) recommended that northeastern Utah along the flanks of the Uinta Moun- the name Nugget Sandstone was more appropriate for the tains. Thus, using another formation name for this fairly massive-weathering sandstone unit overlying the Chinle local area is unwarranted and the Nugget Sandstone is 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors 134 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah preferred over the Glen Canyon Sandstone. ajo Sandstone) thin northward across the buried ances- tral Uncompahgre uplift. Both the Navajo Sandstone and Carmel Formation are missing on the crest of the uplift at EVIDENCE FOR STRATIGRAPHIC Colorado National Monument, near Grand Junction, Colo- CORRELATION rado, where the Middle Jurassic Entrada Sandstone lies on the Kayenta Formation (Scott and others, 2001) (figure 5). We agree with the evidence of McLachlan (1957) and The Uncompahgre uplift plunges to the northwest from Poole and Stewart (1964a, 1964b) supporting a correla- Colorado National Monument and underlies the southern- tion of the Nugget Sandstone with the Glen Canyon Group. most part of the Uinta Basin. Along the down-plunge axis In fact, aetosaur and dinosaur tracks preserved in the and north of the crest of the uplift, the Navajo Sandstone Nugget Sandstone around Dinosaur National Monument is missing or too thin to identify with any confidence in and in the Glen Canyon Group south of the Uinta Basin wells, but the Wingate Sandstone and Kayenta Formation near Moab, Utah, as well as additional evidence from well are preserved, even though regionally thin (figure 6). The logs presented in this paper (figure 2), further support Glen Canyon Group thickens northward under the Uinta the notion that the Nugget Sandstone in the eastern Uinta Basin and likely northwestward toward the thrust belt, Mountains is indeed correlative to the Glen Canyon Group with the Navajo and Wingate Sandstones accounting for in total and not just part of the group. the increased thickness. The Kayenta continues to thin The Nugget Sandstone contains key aetosaur and di- northward. Somewhere between Willow Creek and the nosaur tracks at several locations around Dinosaur Na- subsurface trace of the Seep Ridge fault zone in the Seep tional Monument, north and east of Vernal, Utah (Lockley Ridge 30' x 60' quadrangle (Sprinkel, 2009), the Kayenta and others, 1992; Hamblin and others, 2000; Engelmann either pinches out or changes from fluvial to eolian litho- and others, 2010; Lockley, 2011). The tracks are located facies and cannot be identified in geophysical logs (figure near the base and in the upper half of the Nugget Sand- 6). The loss of the Kayenta strata is the criteria we use to stone. A well-preserved set of tracks identified as Brachy- define areas where the term Nugget Sandstone applies. chirotherium is located less than 10 meters above the base Our interpretation is similar to that of Poole and Stewart of Nugget Sandstone (Lockley and others, 1992; Lockley, (1964a, 1964b) except we believe the eolianite above the 2011) (figure 3). A Brachychirotherium assemblage is also thinning Kayenta (the Navajo Sandstone) continues to preserved in the Wingate Sandstone south of the Uinta Ba- thicken northward. The exact location of the transition sin, which is evidence that at least this part of Nugget Sand- from Glen Canyon Group to Nugget Sandstone is specu- stone is correlative with the Wingate (Lockley and others, lative because of limited well control; however, only the 2004). The upper part of the Nugget Sandstone contains Nugget is recognized in subsurface from the northern part several track species including Grallator, Otozoum, and Eu- of the Seep Ridge quadrangle and in the adjoining Vernal brontes (Lockley and others, 1992; Lockley, 2011) (figure quadrangle to the Uinta Mountains where it is exposed 4). This track assemblage is also preserved in the Kayenta (Sprinkel, 2007). We recommend using the term Glen Can- Formation and Navajo Sandstone south of the Uinta Basin, yon Group where the Kayenta can be recognized and Nug- and implies that the upper part of the Nugget Sandstone is get where it cannot, and the unit as a whole is essentially a correlative with that part of Glen Canyon Group (Lockley massive-weathering eolianite. and others, 2004). In addition, Otozoum tracks were re- A similar stratigraphic relation exists between the ported from the Nugget Sandstone in Wyoming (Kayser, Nugget Sandstone and Glen Canyon Group in the central 1964; Lockley, 2011). and southwestern sectors of the Sevier thrust belt, and we Poole and Stewart (1964b) used well-log data to cor- recommend that the term Nugget be extended into cen- relate between the formations above the Chinle and below tral and southwestern Utah in areas where the Kayenta the Carmel Formations on the northern Colorado Plateau Formation cannot be recognized. Formations of the Glen and along the south flank of the Uinta Mountains, mostly Canyon Group (Wingate Sandstone, Kayenta Formation, in east-central to northeast Utah. By 1965, fewer than 30 and Navajo Sandstone) are not exposed in the central Utah wells had been drilled through the Nugget and Navajo sector of the Sevier thrust belt; however, they are identi- Sandstones in their study area, with fewer than five wells fied in wells drilled along the frontal thrust faults (figure located north of the Uncompahgre uplift. This represents 7 and table 1). The Nugget Sandstone (no Kayenta) is spo- a fairly limited data set to obtain a reasonable view of radically exposed at several locations in the central Utah the correlation and predict thickness trends. Since 1965, thrust belt from the Thistle area (Spanish Fork Canyon) nearly 100 wells have been drilled through the Nugget and southward to Nephi and along the west side of the Pahvant Navajo Sandstones, and nearly 40 wells are located north Range (figure 1, map showing outcrops and geography). In of the Uncompahgre uplift. While this is still somewhat most published reports, Thistle was considered the divid- of a limited data set, we have also interpreted nearly 125 ing line between Nugget-Navajo nomenclature; the term more wells throughout Utah, mostly south of the Uinta Nugget was used north of Thistle and Navajo Sandstone Mountains (figures 2). We interpreted only a few wells in was used south of Thistle (Hintze and Kowallis, 2009). But the northern Utah thrust belt but plan to include signifi- we have not identified the Kayenta Formation in any of the cantly more wells to complete our work for a future, more outcrops south of Thistle to the Pahvant Range and thus, comprehensive report. we consider those rocks as the Nugget. The Nugget Sand- Outcrops and drill holes near Moab, Utah, show that stone is also identified in wells drilled in the central Utah the Carmel Formation and the underlying Glen Canyon thrust. The Nugget is exposed in the footwall of the Nebo Group (Wingate Sandstone, Kayenta Formation, and Nav- and Pahvant thrust faults and on the hanging wall of the 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. 135 Figure 2. Location and distribution of wells used to interpret the subsurface stratigraphic section between the Chinle-Ankareh Formations and Middle Jurassic formations. The Nugget Sandstone-Glen Canyon Group outcrops are shown in darker brown. The places identified on the map as having missing Nugget Sandstone-Glen Canyon Group are areas where the erosion has removed the Nugget Sandstone-Glen Canyon Group (and overlying formations). The eastern boundary of the area of no Jurassic in western Utah reflects the footwall cutoff of the Nugget Sandstone. 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors 136 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah A. Nugget Sandstone Triassic track bed people for scale formation of Bell Springs B. C. D. Late Triassic Brachychirotherium site Figure 3. The Nugget Sandstone contains key aetosaur and dinosaur tracks that support the age and correlation with the Glen Canyon Group. At this site the tracks are: (A) preserved in a thin, horizontal-bedded unit (yellow arrow) that is within a few meters of the base of the Nugget Sandstone (the red line); (B) preserved on the underside of this horizontal-bedded unit, (C) identified as belonging to Brachychirotherium, which is a classic Triassic track, and (D) located east of Vernal, Utah, near Dinosaur National Monument. Another site not far from here also has this species of tracks that lie about 10 m above the base of the Nugget Sand- stone. Brachychirotherium tracks are also found in the lower part of the Wingate Sandstone near Gateway, Colorado (see figure 1 for general location). Paxton thrust fault (for thrust fault locations, see Schell- Kayenta Formation in well logs from the few wells drilled ing and others, 2007). All formations of the Glen Canyon in the area. Full sections of the strata between the Chinle Group are recognized eastward on the Gunnison and Sali- and Carmel Formations are exposed in and around the na thrust faults. We believe the transition is similar to the Mineral Mountains east of Beaver, Utah, and the Kayenta transition in the southern Uinta Basin (figure 8 and table Formation is not reported in those sections (Rowley and 1). others, 2005). In addition, we have interpreted data from The Glen Canyon Group in the southwestern sector of the few wells drilled in the same area and do not recognize the Sevier thrust belt consists of the Moenave Formation, the Kayenta in the subsurface. Thus, we consider the sec- Kayenta Formation, and Navajo Sandstone. The Moenave tion above the Chinle and below the Carmel in those areas is restricted to southwestern and south-central Utah, is as the Nugget Sandstone. partially correlative to the Wingate Sandstone, and rep- resents fluvial-lacustrine deposition (Clemmensen and others, 1989; Blakey, 1994; Peterson, 1994). Excellent and AGE OF THE NUGGET SANDSTONE complete exposures of the Glen Canyon Group are in the St. George area, and attenuated sections are east of the As noted in the previous section, the Nugget Sand- Hurricane fault in the Cedar City area (figure 1) (Rowley stone contains key aetosaur and dinosaur tracks and and others, 2006; Biek and others, 2009). Outcrops of newly discovered dinosaur bones that help constrain its strata below the Carmel Formation are limited and incom- age. The lower part of the Nugget is Late Triassic in age plete west of the Hurricane fault in the Cedar City area, based on the Brachychirotherium assemblage preserved making it difficult to evaluate if these sections are Nugget near the base of the formation (Lockley and others, 1992). or Glen Canyon Group. However, we do not recognize the The upper part of the Nugget is considered Early Jurassic 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. 137 A. B. C. Early Jurassic Eubrontes site Figure 4. The Nugget Sandstone contains key aetosaur and dinosaur tracks that support the age and correlation with the Glen Canyon Group. At this site the dinosaur tracks are: (A) preserved in a fluvial lens that likely represents an interdunal wadi unit within the eolianite near the top of the Nugget Sandstone, (B), include Grallator and Eubrontes (pictured), both common Early Jurassic tracks, and (C) located along the shore of Red Fleet Reservoir, northeast of Vernal, Utah. Colorado National Monument Visitor Center Entrada Sandstone Kayenta Formation Wingate Sandstone Figure 5. The Uncompahgre uplift is a regional structural high that began to rise in Pennsylvanian time and affected Pennsylva- nian, Permian, and Triassic deposition. This photograph shows the stratigraphic succession above the Chinle Formation exposed at Colorado National Monument. The Wingate Sandstone is overlain by the Kayenta Formation, which is typical throughout the Colorado Plateau; however, lying on the Kayenta is the Middle Jurassic Entrada Sandstone. Thus, the Navajo Sandstone and Car- mel Formation are missing. 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors  SOUTH NORTH 138 A 46 miles 10 miles 15 miles 13 miles 7 miles 29 miles 32 miles A’ Tiger Oil Company JC Thompson Operator Beartooth Oil & Gas Company Wind River Resources Corporation IP Petroleum Co. Gulf Oil Corporation Phillips Petroleum Company Great Basin Petroleum Company State 12-11 Westwater Unit E5 Fence Canyon Unit 1 North Hill Creek 10-10-15-20 Agency Draw 16-3 Gray Knoll Federal 1 Johnson-Watson Fee 2 West Ashley G-21 SW¼NW¼ Sec. 11, T. 24 S., R. 20 E. NE¼NW¼ Sec. 18, T. 17 S., R. 24 E NE¼SE¼ Sec. 36, T. 15 S., R. 22 E. NW¼SE¼ Sec. 10. T., 15 S., R. 20 E. SE¼SE¼ Sec. 3, T. 13 S., R. 20 E. SW¼NE¼ Sec. 22, T. 12 S., R. 21 E. NW¼NW¼ Sec. 34, T. 9 S., R. 25 E. SW¼NE¼ Sec. 21, T. 5 S., R. 22 E. Grand County, Utah Grand County, Utah Uintah County, Utah Uintah County, Utah Uintah County, Utah Uintah County, Utah Uintah County, Utah Uintah County, Utah API: 4301930455 API: 4301930077 API: 4304716197 API: 4304734830 API: 4304731510 API: 4304730226 API: 4304710916 API: 4304730329 SP LL Cond SP Ri Rn Cond SP SFL Cond SP Rn Rln SP Ri Rn Cond 13100 SP LL Cond SP Ri LL Cond 9100 GR LL Cond 9500 3200 5000 J-3 unconformity J-3 unconformity Entrada Sandstone Entrada Sandstone 1500 Carmel Formation 3500 13500 11500 13000 Carmel Formation J-1 unconformity 9500 J-1 unconformity Navajo Sandstone 10000 5500 Nugget Sandstone 2000 Kayenta Formation 4000 14000 12000 13500 TD =12,055 10000 Wingate 5900 Sandstone TD =10,350 SP SHIFT Glen Canyon Group 10500 TD = 5957 ancestral Uncompahgre uplift TD = 13,538 Chinle Formation 2500 Chinle Formation 13900 TD =15,400 4500 14500 TD =12,357 TD = 5475 TD =15,666 Tiger Oil Company JC Thompson Operator Beartooth Oil & Gas Company Wind River Resources Corporation IP Petroleum Co. Gulf Oil Corporation Phillips Petroleum Company Great Basin Petroleum Company State 12-11 Westwater Unit E5 Fence Canyon Unit 1 North Hill Creek 10-10-15-20 Agency Draw 16-3 Gray Knoll Federal 1 Johnson-Watson Fee 2 West Ashley G-21 Nomenclature change Formation Depth Thick Formation Depth Thick Formation Depth Thick Formation Depth Thick Formation Depth Thick Formation Depth Thick Formation Depth Thick Formation Depth Thick Entrada Sandstone 1401 239 Entrada Sandstone 5028 148 Entrada Sandstone 9194 166 Entrada Sandstone 11,288 269 Entrada Sandstone 12,755 305 Entrada Sandstone 13,299 226 Entrada Sandstone 9530 222 Entrada Sandstone 3289 168 Carmel Formation 1640 110 Carmel Formation 5176 185 Carmel Formation 9360 205 Carmel Formation 11,557 88 Carmel Formation 13,060 48 Carmel Formation 13,525 155 Carmel Formation 9752 60 Carmel Formation 3457 121 Navajo Sandstone 1750 240 Kayenta Formation 5361 191 Kayenta Formation 9565 175 Kayenta Formation 11,645 105 Navajo Sandstone 13,152 69 Navajo Sandstone 13,680 107 Nugget Sandstone 9882 528 Nugget Sandstone 3578 702 Kayenta Formation 1990 146 Wingate Sandstone 5552 272 Wingate Sandstone 9740 216 Wingate Sandstone 11,750 262 Kayenta Formation 13,221 74 Kayenta Formation 13,796 109 Chinle Formation 10,410 Chinle Formation 4280 Wingate Sandstone 2136 394 Chinle Formation 5824 Chinle Formation 9956 Chinle Formation 12,012 Wingate Sandstone 13,370 495 Wingate Sandstone 13,905 384 Chinle Formation 2530 Chinle Formation 13,865 Chinle Formation 14,289 LOG CURVE ABBREVIATIONS Glen Canyon Group 5292 463 Glen Canyon Group 9406 391 Glen Canyon Group 11,610 367 SP - Spontaneous Potential Glen Canyon Group 1750 780 Glen Canyon Group 13,108 713 Glen Canyon Group 13,637 609 Rn - Resistivity Normal Rln - Resistivity Long Normal Rl - Resistivity Lateral Ri - Resistivity Induction LL - Resistivity Laterolog SFL - Spherically Focused Log GR - Gamma Ray Cond - Conductivity All depths and thicknesses reported in feet Figure 6. Cross section A-A’ shows the correlation of Middle Jurassic to Upper Triassic formations from near Moab, Utah, northward to near Vernal, Utah. It was drawn to high- light the change in nomenclature between Glen Canyon Group and the Nugget Sandstone based on regional changes of the petrophysical log signatures, supported by limited sample descriptions and cuttings. The Glen Canyon Group includes the Wingate Sandstone, Kayenta Formation, and Navajo Sandstone. The Wingate and Navajo are sandstone beds of predominantly eolian origin whereas the Kayenta is sandstone, siltstone, and minor limestone beds of fluvial-lacustrine origin. The Nugget Sandstone is predominantly of eolian origin. The cross section shows the Glen Canyon-Nugget interval thins over the ancestral Uncompahgre uplift, mostly at the expense of the Navajo Sandstone. In addi- tion, the Kayenta thins northward and eventually pinches out. The nomenclatural change between Glen Canyon Group and Nugget Sandstone is where the Kayenta Formation is no longer identified in wells. The Kayenta Formation is characterized as having a more positive SP response and higher resistivity as compared to the overlying Navajo and underlying Wingate. The cross section datum is the J-3 unconformity at the top of the Entrada Sandstone. (click for larger view) Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas  SOUTHWEST NORTHEAST B 18 miles 12 miles 40 miles B’ WOLVERINE G&O CO UT CHEVRON USA INC WOLVERINE G&O CO UT PHILLIPS PETROLEUM TENNECO OIL CO WOLVERINE FEDERAL 17-8 SALINA UNIT 1 Wolverine Federal Arapien Valley 24-1 UNITED STATES E 1 CLEAR CREEK 1 NESW SEC 17, T. 23 S., R. 1 W. NENE SEC 33, T. 22 S., R. 1 W. SWNW SEC 24, T. 20 S., R. 1 E. NWNE SEC 27, T. 19 S., R. 3 E. CNW SEC 17, T. 14 S., R. 7 E. API: 4304130047 API: 4304130020 API: 4303930030 API: 4303930004 API: 4300720068 GR SP Resistivity Density Sonic GR Resistivity Density Sonic GR Resistivity Density Sonic GR Resistivity Density Sonic GR SP Resistivity Density 5500 8500 Twelvemile Canyon 8500 Member 13500 Watton Canyon Member Boundary Ridge Member Arapien Formation Rich Member Sliderock Member 11000 Esplin Point member 6000 Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. White Throne Member 9000 9000 Formation Temple Cap Sinawava Member 14000 11500 6500 9500 9500 Navajo Sandstone 14500 12000 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors 7000 TD=15,703 feet 10000 10000 ª Glen Canyon Group 15000 Kayenta Formation TD=20,450 feet ªªª Nephi " B’ Price ª ª " Wingate Sandstone ªª ª ª *R ª 7500 TD=13,050 feet ªRªªª 10500 ªªªª ªª Manti " Castle Dale ª Gunnison " ª " Chinle Formation ª ' ª ' * Salina TD=13,760 feet ª " B'ª *ª ªª ªª TD=17,423 feet ª ª ª ª " " " ª fontal thrust Figure 7. Cross section B-B’ shows correlation of the Wingate Sandstone, Kayenta Formation, and Navajo Sandstone within the wells that parallel the ª ªfaults of the Sevier thrust belt in central Utah. The Kayenta Formation is recognized in the wells using geophysical logs supported by sample descriptions and cuttings. Thus the term Glen Canyon Group is preferred. The cross section datum is the Watton Canyon Member of the Arapien Formation (equivalent to the Paria River Member of the Carmel Formation). 139 (click for larger view)  140 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah Table 1. Tops and thickness of Nugget Sandstone and formations of the Glen Canyon Group from wells used in cross sections B-B’ (figure 7) and C-C’ (figure 8). Formation tops in age based on the Grallator, Otozoum, and Eubrontes as- for Chinle/Ankareh Top 6965 7648 10,884 10,280 12,094 8329 14,953 11,976 9518 semblages (Lockley and others, 1992; Hamblin and others, depths and have not been corrected for well-bore deviation. Reported formation thickness is an apparent thickness as the values were not corrected 2000; Lockley, 2011). In addition, recent discoveries of 8). Brasilichnium tracks on the slip faces of dune sets (Engel- (figure mann and others, 2010) and abundant bone fragments C-C' not of a coelophysoid theropod (Chambers and others, 2011; Engelmann and others, 2011) in the Nugget Sandstone 7) andwere Nugget Nugget Kayenta Kayenta Wingate Wingate near Dinosaur National Monument are supportive evi- Thick 370 436 357 330 599 313 330 0 0 dence for the upper Nugget being Early Jurassic in age. This the values age range for the Nugget is similar to what is reported for the Glen Canyon Group (Lockley and others, 2004; Lucas (figure and others, 2005; Cornet and Waanders, 2006; Kirkland Top 6595 7212 118 10,527 9950 7730 138 14,640 156 11,646 0 0 and Milner, 2006; Lucas and Milner, 2006; Lockley, 2011). B-B' as Thus, the Nugget in the Uinta Mountains is Late Triassic to thickness Early Jurassic in age. cross sections We assume that the Nugget Sandstone in the Sevier Thick 298 162 137 0 0 65 thrust belt is also Late Triassic to Early Jurassic, although inapparent no fossil evidence for a Late Triassic age has been reported. However, the contact and stratigraphic relations between the Nugget and the underlying formations (the Chinle and Top 1109 10,409 7665 6297 7050 9813 712 14,502 302 11,490 0 0 is an Ankareh Formations) in the Sevier thrust belt are the same wells used as the Chinle-Nugget contact in the Uinta Mountains. The thickness lithofacies and sedimentary features in the upper Chinle to the lower Nugget exhibit a general coarsening-up transi- Thick Navajo/ Navajo/ 1052 706 210 422 874 883 tion from predominately fluvial with some thin lacustrine Group from beds to predominately eolian beds. This transition inter- Canyonformation val has been mapped as the formation of Bell Springs in the eastern Uinta Mountains (Jensen, 2005; Haddox and Top 9300 11,042 8812 7455 5875 6176 8930 13,790 11,188 others, 2010a, 2010b) and is recognized elsewhere be- tween Ankareh Formation and Nugget Sandstone (Bran- Reported dley, 1988) and the Chinle Group and Glen Canyon Group (Lucas and others, 1997; Lucas and others, 2005) (see the of the Glen discussion of formation of Bell Springs in the next section). formationdeviation. We do not see a regional unconformity at the basal Fed Arapien Valley 24-1 Nugget contact in Utah that separates Triassic beds from Chicken Creek 16-34 Jurassic beds. Thus, the Triassic-Jurassic boundary is with- United States E-1 in the Nugget Sandstone and the J-0 unconformity of Pipir- WXC-Howard 1A andwell-bore ingos and O’Sullivan (1978) probably does not exist. The WXC-Barton 1 Clear Creek 1 Emery Unit 1 Salina Unit 1 Federal 17-8 top of the Nugget and Navajo Sandstone of the Glen Can- Well Name yon Group in the Sevier thrust belt of Utah is the regional Sandstonefor J-1 unconformity (Pipiringos and O’Sullivan, 1978). been corrected DISCUSSION OF FORMATION OF corrected for well-bore deviation or bedding attitude. BELL SPRINGS Wolverine Gas & Oil Company Wolverine Gas & Oil Company Nugget Phillips Petroleum Company Underlying the Nugget Sandstone is a succession of and haveofnot beds that contains sedimentary features that indicate a Tenneco Oil Company attitude. transition from predominately fluvial-tidal flat deposi- and thickness Placid Oil Company Placid Oil Company Skelly Oil Company as drilled tion to predominately eolian deposition of the Nugget. American Quasar Chevron USA, Inc This transitional unit has been recently mapped as the or bedding formation of Bell Springs in the eastern Uinta Mountains depths tops are reported (Jensen, 2005; Haddox and others, 2010a, 2010b). The for- Operator tops mation of Bell Springs resembles the Bell Springs Member as drilled of the Nugget (Pipiringos, 1968) in east-central Wyoming 1. Formation Formationdeviation and had been previously included in the Chinle Formation (Kinney, 1955; Poole and Stewart, 1964b) or the Nugget 4304130020 4302330007 4302330004 4302330009 4304111136 4304130047 4303930030 4303930004 4300720068 Sandstone (High and others, 1969; Picard, 1977) in the reported Uinta Mountains. It is also similar to beds described in the well-bore Church Rock Member of the Chinle Formation (Stewart and Table others, 1972; Dubiel, 1992) and the Rock Point Formation API are 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas  NORTHWEST 18 miles 12 miles 49 miles 32 miles SOUTHEAST PLACID OIL CO PLACID OIL CO AMERICAN QUASAR WOLVERINE G&O CO UT SKELLY OIL COMPANY C WXC-HOWARD 1-A WXC-BARTON 1 CHICKEN CREEK UNIT 16-34 WOLVERINE FEDERAL 17-8 EMERY UNIT 1 C’ NENW SEC 5, T. 14 S., R. 1 W. NWSE SEC 32, T. 16 S., R. 1 W. SWSE SEC 16, T .15 S., R. 1 E. NESW Sec 17, T. 23 S., R. 1 W. SWSE Sec 34, T. 22 S., R. 5 E. API: 4302330007 API: 4302330004 API: 4302330009 API: 4304130047 API: 4304111136 GR SP Resistivity Density Sonic GR Sonic GR Resistivity Density Sonic GR SP Resistivity Density Sonic SP GR Resistivity Sonic 5500 Twelvemile Canyon 6500 Member 5500 Watton Canyon Arapien Member Formation 9500 7500 Boundary Ridge Temple Cap 6000 Member Formation 7000 6000 Navajo Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. Sandstone Rich Member Arapien Formation 10000 8000 6500 7500 Kayenta Fm. 6500 Sliderock Member Glen Canyon Group Esplin Point 10500 8500 Member 7000 Wingate Sandstone 8000 7000 White Throne Member 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors Chinle Formation Temple Cap Formation 11000 Sinawava Member 9000 7500 Moenkopi Formation 8500 TD=10,740 feet ª TD=13,760 feet ªªª TD=13,515 feet Nephi " C Price 11500 ª " 9500 Nugget Sandstone ªª ª ª ª* ªRR ªªª ªªªª ªª Manti " ª Castle Dale " Gunnison " ªª TD=21,840 feet ª ª' * Salina ' ª" 12000 'ª * ªª C’ ªª ª ª ª Nomenclature change Ankareh Formation TD=12,150 feet ª ª " " " ª ªª " Figure 8. Cross section C-C’ shows the correlation and stratigraphic relations between the Nugget Sandstone and formations of the Glen Canyon Group along the transport direction of thrusting in the Sevier fold and thrust belt in central Utah. The Glen Canyon Group is recognized where the Kayenta Formation is identified in wells using geophysi- cal logs supported by sample descriptions and cuttings. The Kayenta Formation thins and either pinches or transitions to eolian lithofacies to the northwest. The term Nugget 141 Sandstone is used where the Kayenta Formation is not recognized. This somewhat simple stratigraphic relation may be complicated in some wells by thrust faults. It is possible that in some wells, the Nugget Sandstone drilled on the hanging wall may overlie the Glen Canyon Group drilled in the footwall. The cross section datum is the Watton Canyon Member of the Arapien Formation (equivalent to the Paria River Member of the Carmel Formation). (click for larger view) 142 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah of the Chinle Group in the Four Corners area (Lucas and at 260º. Sandstone beds are commonly bioturbated and others, 1997; Lucas and others, 2005). We only mention mottled. Mudcracks and small salt casts are also common the formation of Bells Springs here in our discussion of the (figures 12A and 12b). The mudstone and siltstone beds Nugget Sandstone-Glen Canyon Group correlation because are mostly purple, red, and brown, and the sandstone we believe these beds: (1) are regionally recognizable, (2) layers vary in color from reddish-purple to orange to tan show that stratigraphic relations between the upper Chin- with yellow, white, and gray mottling. Siltstone beds are le-Ankareh Formations and lower Nugget are similar to thinly bedded. those between the upper Chinle and Wingate Sandstone, In the upper half of the Bell Springs Member, two (3) imply continuous deposition from Ankareh-Chinle For- sandstone beds, separated by fine-grained, ripple-marked mation to Nugget Sandstone, and (4) corroborate a region- siltstone and thin mudstone, are present. The two sand- al Late Triassic age for the Nugget. stone beds have well-rounded quartz grains and large, In south-central Wyoming, near Rawlins, Pipiringos tabular cross-bedding and sigmoidal bedding, with some (1968) established the name Bell Springs Member of the sets reaching amplitudes of 1 meter (figure 13A). The up- Nugget Sandstone for a sequence of ripple-marked, red and gray sandstone, and red, green, and purple siltstone and shale beds. He also reported that the Bell Springs sat disconformably on top of the Popo Agie Formation (Chin- le Formation equivalent), with the basal beds of the Bell Springs commonly containing rip-up pebbles of ocher- colored, analcime-rich mudstones from the underlying Popo Agie Formation. Pipiringos (1968) also pointed out that the Bell Springs Member of Wyoming correlated with the unnamed upper member of the Chinle Formation as described by Kinney (1955) and Poole and Stewart (1964a, 1964b) in northeastern Utah. Picard (1975) also recognized two subdivisions in the Nugget Sandstone in northeastern Utah. He called the low- er unit the “thinly-bedded facies” and discussed the pos- sibility that this facies was equivalent to the Bell Springs Member of the Nugget in Wyoming. Lucas and others’ (1997) work suggests that the Rock Point (Church Rock) Formation of the Chinle Group, near the Four Corners re- gion, is correlative with formation of Bell Springs. The lithofacies and thickness range of the Bell Springs Member in the eastern Uinta Mountains are quite consist- ent (figure 9). The first resistant sandstone overlying the upper red unit of the Chinle Formation is considered the basal bed of the Bell Springs. Where this contact can be clearly seen, it may be a local angular unconformity (fig- ure 10) (High and others, 1969). This angular relationship is not observed in any other areas and most likely repre- sents a deltaic clinoform in the lacustrine sediments of the Chinle rather than a regional erosion surface. Pipiringos (1968) reported a basal bed of pebbles in the Bell Springs, composed of ocher-colored analcime rocks derived from the Chinle along with chert and other lithics from an uni- dentified source. Conglomerate beds, although not found everywhere, do occur along the south flank of the Uinta Mountains and may mark a major unconformity or may be local channel gravels in the upper Chinle. The lower half (approximately 15 meters) of the Bell Springs Member is composed of interbedded units of fine- to medium-grained sandstone and siltstone, usually 1 to 10 meters thick, and planar laminated mudstone that ranges from 0.5 to 2 meters thick. The sandstone is planar laminated and contains abundant ripple marks that vary from asymmetrical to symmetrical flaser ripples (figure Figure 9. Stratigraphic column of the Upper Triassic and 11). Mud drapes are thin (1 to 2 mm). The ripple marks Lower Jurassic formations in northeastern Utah. Sedimentary are approximately 2.5 to 3 cm from crest to crest and 0.5 and bedding features identified in the formation of Bell Springs to 1 cm in amplitude. Rippled beds are multidirectional, are interpreted as fluvial to tidal-flat deposition. In addition, but the crests average a slight southwest-northeast trend it represents a transition from predominately fluvial to eolian deposition. 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. 143 per cross-bedded sandstone contains scoured channels filled by sand (figure 13B). From north to south in the Red Fleet area northeast of Vernal, Utah, the sandstone beds of the Bell Springs Member become less resistant and change from a sheer, cliff-forming sandstone to thin- ner, flaggy-bedded silty-sandstone beds over a distance of a few 100 meters. Based upon the sedimentary struc- tures and bedding succession, Jensen (2005) interpreted the Bell Springs Member as a tidal deposit. Other stud- ies on the Bell Springs Member of the Nugget Sandstone have also interpreted it as a tidal deposit (Pipiringos, 1968; Doelger and Steidtmann, 1982). In addition, equiv- alent beds of the upper Ankareh Formation in Spanish Fork Canyon, near Diamond Fork, Utah, have been inter- preted as tidal flat deposits (Brandley, 1988). However, stratigraphically equivalent beds on the north flank of the Uinta Mountains, near Sheep Creek, Daggett County, Utah, appear to have been deposited in a deeper water system, Figure 10. The angular unconformity that separates the upper as do the equivalent beds to the west near Hannah, Utah. red unit of the Chinle Formation and the overlying formation of The Bell Springs Member at the Nugget Sandstone type Bell Springs is thought to represent structural warping before section, west of Kemmerer, Wyoming, also appears to the deposition of the Bell Springs Member (High and others, have been deposited in relatively deeper water, given the 1969); however, this relationship has not been identified else- abundant mudstone and siltstone beds, lack of sandstone where in the region and it may represent a deltaic clinoform, beds, and planar lamination within the more competent unique only to this location. Photograph taken south of Squaw Springs (northwest of Vernal, Utah). Note the black Labrador beds in all of the deeper water sections. The strata at retriever for scale. these localities are consistent with the overall regional setting and provide some control over the placement of the shoreline. Additional work is needed to determine if the formation of Bells Springs should be a member of the Nugget Sandstone (as established by Pipiringos, 1968), included in the Chinle Formation, or formalized as a new regional formation. DISTRIBUTION OF NUGGET SANDSTONE AND GLEN CANYON GROUP We have presented evidence to show that the Nug- get Sandstone correlates with the Glen Canyon Group and that both are Late Triassic to Early Jurassic age. We have suggested that the term Nugget Sandstone should be used for strata that lie between the Ankareh-Chinle For- mations and Jurassic formations where the Kayenta For- mation is not recognized. The term Glen Canyon Group should be used where the Kayenta Formation is recog- nized. Thus, the Nugget is a thick eolianite with some mi- nor interbedded fluvial-lacustrine beds, mostly near its base. The Glen Canyon Group contains a thick eolianite at its base (Wingate Sandstone) and at its top (Navajo Sandstone) separated by fluvial beds of the Kayenta For- mation. The Moenave Formation consists of fluvial-lacus- trine beds in southwestern Utah and intertongues with the Wingate Sandstone (Lucas and others, 2005). Based on the criteria above, we have examined key sections exposed throughout Utah and interpreted about 150 well logs (to date) to determine Nugget versus Glen Canyon Group sections. We have mapped a preliminary nomenclature boundary based on their distribution (figure Figure 11. Flaser ripples preserved in the lower part of the for- 14) In general, the Glen Canyon Group is restricted to much mation of Bell Springs. These sedimentary structures are char- of the Colorado Plateau, on or south of the Uncompahgre acteristic of the moderate- to high-energy facies within the in- Uplift, and into southwestern Utah. The Nugget Sandstone tertidal zone. 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors 144 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah is restricted to the Uinta Mountains, much of the Uinta Basin, ACKNOWLEDGMENTS and the Sevier thrust belt. The boundary in the central Utah sector of the thrust belt could be complicated by thrusting. We thank Jim Kirkland (Utah Geological Survey) for In some areas, the Nugget Sandstone may be on the hanging his discussion of the tracks, and Scott Madsen (Utah Ge- wall of a thrust but the Glen Canyon Group may be on the un- ological Survey), Dale Gray (U.S. Forest Service, retired), derlying footwall. and Mary Beth Bennis-Bottomley (Utah Field House of A. B. Figure 12. Sedimentary features preserved in the lower part of the formation of Bell Springs include: (A) mudcracks and (B) salt crystal casts. These features denote periods of subaerial exposure, typical of a tidal-flat system. A. B. Figure 13. Sedimentary features in sandstone beds in the upper part of the formation of Bell Springs include: (A) sigmoidal beds and cross-bedding from offshore sand bars, and (B) scour and fill from migrating sand bars. 2011 UGA Publication 40—Sevier Thrust Belt: Northern and Central Utah and Adjacent Areas Sprinkel, D.A., Kowallis, B.J., and Jensen, P.H. 145 Figure 14. Distribution of Nugget Sandstone-Glen Canyon Group nomenclature. The rock that overlies the Chinle-Ankareh For- mations and underlies the Middle Jurassic units in Utah includes the Nugget Sandstone and Glen Canyon Group. The Glen Canyon Group contains the Wingate Sandstone (and intertonguing Moenave Formation), Kayenta Formation, and Navajo Sandstone. Areas where the Kayenta Formation is not recognized, the term Nugget Sandstone is used. The places identified on the map as having missing Nugget Sandstone-Glen Canyon Group are areas where the erosion has removed the Nugget-Glen Canyon (and overlying formations). The eastern boundary of the area of no Jurassic in western Utah reflects the footwall cutoff of the Nugget. 2011 UGA Publication 40—Sprinkel, D.A., Yonkee, W.A., and Chidsey, T.C., Jr., editors 146 Correlation and Age of the Nugget Sandstone and Glen Canyon Group, Utah Natural History Museum State Park) for taking Sprinkel laneous Investigations Series Map I-1944, scale to the track site near Dinosaur National Monument. We 1:100,000. are very grateful to Grant Willis (Utah Geological Survey) for his careful review of the manuscript and figures. The Bryant, B., 1992, Geologic and structure maps of the manuscript and figures are greatly improved because of Salt Lake City 1º x 2º quadrangle, Utah and Wyo- his work. We also thank Robert Ressetar (Utah Geologi- ming: U.S. Geological Survey Miscellaneous Inves- cal Survey) for his technical review. Finally, this project tigations Series I-1997, scale 1:250,000. was supported by the Utah Geological Survey and the U.S. Geological Survey, National Cooperative Geologic Map- Chambers, M., Hales, K., Britt, B.B., Chure, D.J., Engel- ping Program, through USGS STATEMAP award numbers mann, G.F., and Scheetz, R., 2011, Preliminary 06HQAG0037, 07HQAG0141, and 08HQAG0096. Some support was also provided by the USGS EDMAP pro- taphonomic analysis of a coelophysoid theropod di- gram, award numbers 03HQAG0034, 04HQAG0055, and nosaur bonebed in the Early Jurassic Nugget Sand- 05HQAG0049 to Brigham Young University. stone of Utah [abs.]: Geological Society of America Abstracts with Programs, v. 43, no. 4, p. 16. 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