THE PINNACLES of the CHESLER PARK/ GRABEN REGION of CANYONLANDS NATIONAL PARK RESULT from PALEOSTREAM INDURATION and INVERTED TOPOGRAPHICAL RELIEF by Clyde L

Home , Cedar Mesa Sandstone, Druid Arch, Geology of Utah, Organ Rock Formation, Paradox Formation, White Rim Sandstone

HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/ GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF by Clyde L. Denis1

ABSTRACT

In the Needles District of Canyonlands National Park, Utah, a number of isolated Cedar Mesa Sandstone pinnacles meander across the western side of the Monument upwarp through the Chesler Park and graben regions. The pinnacles are not obviously linked to current stream erosion, and their existence has not been adequately explained. The hypothesis proposed herein is that the sinuous pattern of the pinnacles that borders the series of parks in this area (e.g., Chesler Park and Virginia Park), and that trends northwest across the grabens, is an example of inverted topographical relief. Cementation associated with early Permian rivers indurated the Cedar Mesa Sandstone when the overlying Organ Rock Formation was being deposited. Following the mass wasting that occurred upon the erosion of the Colorado Plateau and the flowage of the underlying Paradox salt into the Colorado River, the sinuous traces of the indurated Cedar Mesa Sandstone became exposed. This hypothesis is supported by several observations. The extant pattern of pinnacle orientation corresponds to the interpreted northwest trends of streambeds in the overlying Organ Rock Formation. The inferred seasonable, wet-dry semi-arid paleoclimate at the time of this proposed induration is known to induce calcrete formation of underlying sands in other units. The Organ Rock For- mation streams are considered to be moderate-load rivers characteristic of streams that favor induration. The degree of sinuosity of the pinnacles, indicative of the meanderings of the overlying streams, predicts precipitation levels consistent with low storminess and a semi-arid climate. Importantly, the pinnacle origin appears to predate the formation and erosion of the Colorado Plateau. The northwest trend of these Canyonland pinnacles can be traced west across the modern Colorado River to the Dollhouse pinnacles in the Maze District. In several cases, where erosion has been especially severe, the meandering pinnacle pattern clearly crosses both the grabens and current streams, indicating prior existence of the pinnacles.

INTRODUCTION geological investigation into the causes for the existence of the parks and their pinnacle boundaries. The Needles District of Canyonlands National Park in Chesler Park, the premier hiking destination for the southeastern Utah (figure 1) displays a number of interest- Needles District, is actually one of at least seven parks that ing geological features. It is justly famous for the grabens describe a northwest trending arc near the crest of the Mon- that are situated in the western section of the Needles and ument upwarp just south of the confluence of the Colo- that extend from the Colorado River to the Monument up- rado and Green Rivers. These parks from north to south warp axis. Nearly parallel with the Monument upwarp axis are Cyclone Park, Devils Parks North and South, Chesler are additional features from which the Needles District Park, Virginia Park, Shisler Park, and Starvation Pocket derives its name: a series of 100- to 170-meter high pin- (figure 3). There are also several mesas interspersed with nacles (figure 2). These eponymous needles of the Needles the parks: Druid Arch Mesa, Molehill Mesa, and two un- District are formed from Cedar Mesa Sandstone. The pin- named mesas south of Starvation Pocket (not shown). Each nacles circumambulate around a series of parks and subse- of these parks is circumscribed by a row of pinnacles. quently diverge in a meandering pattern west-northwest- The pinnacles of the Needles District, consisting of ward across the grabens (figures 3 to 5). Whereas a number Cedar Mesa Sandstone deposited during the Permian, are of studies have provided explanations and interpretations generally formed through fractures induced by underlying for most aspects of graben formation, there has been little joints and subsequent processes of erosion (Baars, 2000).

1Department of Molecular, Cellular, and Biomedical Sciences, University of New Denis, C.L., 2014, Hypothesis—the pinnacles of the Chesler Park/Graben region Hampshire, Durham, NH; [email protected] of Canyonlands National Park result from paleostream induration and inverted topographical relief, in MacLean, J.S., Biek, R.F., and Huntoon, J.E., editors, Geology of Utah’s Far South: Utah Geological Association Publication 43, p. 25–38. 26 HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L. Figure 2. Triassic unitsintheCanyonlandsarea.DrawingbyRussellDubiel. Figure 1. A) Map of Utah showing the approximate location of the Needles District. B) Stratigraphic diagram showing late Paleozoic and Aerial view ofCheslerParkandtheDevils Pinnacleslookingnortheast. 1A UGA Publication 43(2014) 1B —Geology of Utah'sFar South HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L

Figure 3. Canyonlands. The pinnacles and erosionally resistant forms above the “mushroom” layer of the Cedar Mesa Sandstone are . indicated in black. The pattern of the pinnacles was determined by numerous on-site visitations, from photographs of various regions, and from aerial photographs.

MacLean, J.S., Biek, R.F., and Huntoon, J.E., editors 27 28 HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L. and ”C”marksthecrossingof CheslerCanyon. Figure 4. Enlarged map of Chesler Park/graben area. The letters ”A” and ”B” mark the points where the pinnacles cross Elephant Canyon UGA Publication 43(2014) —Geology of Utah'sFar South HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF –

Figure 5. Satellite map of Chesler Park/graben area with traces of pinnacles trends. Based on the location of the pinnacles marked on figure 3, the predicted traces of the pinnacle paths are marked in white. Dotted lines indicate where the pinnacle trends are uncertain.

They exist throughout the Needles District and on both the Paradox Basin salt underneath the Chesler Park/graben eastern and western sides of the Monument upwarp. Their region flowed towards the Colorado River. height above the surrounding rocks (often up to at least 170 meters) and the fracturing gives them their particular GEOLOGICAL SETTING “needle”-like appearance. The pattern of the pinnacles on the two sides of the Monument upwarp is different, how- Canyonlands National Park resides in the Paradox ever. On the eastern side erosional processes have been Basin, an oval area in southeastern Utah and southwestern much less active, and the pinnacles are generally present Colorado. For this study, the Paradox Basin is defined as throughout the area except where streams have evidently the maximum extent of halite and potash salts in the Middle eroded the Cedar Mesa Sandstone. On the western side of Pennsylvanian Paradox Formation (Condon, 1997). These the Monument upwarp, erosion has been much more se- ancestral salt and gypsum are as much as several hundred vere, and fewer pinnacles remain. Recent data indicate that meters thick in the Canyonlands region. The Paradox Basin the region west of the Monument upwarp is subsiding by itself is a local area of reduced elevation that appears to about 2-3 mm/yr compared with no change on the eastern have become greatly accentuated with the concomitant rise side (Furuya and others, 2007). Distinctively, on the west- of the Uncompaghre uplift mountain range on its eastern ern side of the Monument upwarp the plan-view serpentine side. The Uncompaghre mountains extended southeast- pattern formed by the pinnacles in and around the parks ward from east-central Utah through Gateway, Colorado, and across the grabens (e.g., Devils Pocket, Devils Lane, toward northern New Mexico (Baars, 2000). Forces that and Cyclone Canyon) is reminiscent of patterns formed created the rise of the Uncompaghre correspondingly ac- by meandering streams (figures 3 to 5). This pattern sug- centuated a deep hollow directly to its west, the Paradox gests depositional processes operating during the Permian Basin, which became progressively less deep to the south- have influenced modern-day geomorphic relief. This study west where the Needles District now lies. The basin ended proposes induration of the Cedar Mesa Sandstone occurred just southwest of present day Canyonlands National Park, during streambed deposition of the conformably overlying for there are no salts southwest of this point (Nuccio and

Organ Rock Formation during the Late Permian Period. Condon, 1996). Denis, C.L These indurated sandstone streambed traces subsequently The strata above these Pennsylvanian rocks in Can- resisted, relative to adjacent rocks, both the erosion that fol- yonlands make up the Permian Cutler Group (figure 1B). . lowed the incision of the Colorado Plateau and the exces- The Cutler Group comprises the lower Cutler beds, the sive erosion west of the Monument upwarp that occurred as Rico Formation of some reports and the Halgaito Forma-

MacLean, J.S., Biek, R.F., and Huntoon, J.E., editors 29 30 HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L. the river in an arc that initially starts at the north running north the at starts initially that arc an in river the from eastward extending grabens the in resulted fractures Walsh,and Ela These Walsh2003). 2002; Schulz-Ela, and gan tomovewestwardand fractureintheprocess(Schulz- be and sheet brittle large a like acted rocks sandstone ing Stromquist, and overly the westward, Ely,flowed 1979; salt McGill 1989). the As 1933; (Baker, River Colorado the into westward flowed salt the uplift, Monument the of eastern side of Chesler Park to the Colorado River because downward slope (2° to 4°) of the region westward from the flow into the Colorado River (Baars, 2000). Due to a slight to began salt Formation Paradox the strata, Pennsylvanian underlying the into canyon its cut River Colorado modern the When Sandstone. Mesa Cedar the overlying mediately im layers the including away, worn were sandstones ing overly particularly, District, Needles the In Plateau. the of areas vast remove to began erosion ago, years million 5 least at elevated became Plateau Colorado the As tems. sys fluvial more and mountains Uncompaghre the of sion ero greater in resulted warmth, and precipitation, midity, hu increased with periods, Non-glacial Mountney,2006). sands were delivered to more the low,area (Langford were and Chan, levels 1989; sea when periods glacial of the result probably periods, arid more During beds. sandstone in thinlimestonebeds(Drieseandothers,2006). al floods left clay pans or semi-permanent ponds deposited shale and limestone within the dunes mark where ephemer of Lenses 2006). others, and Driese Jagger,2004; and ney floods into the dune sea (Langford and Chan, 1988; Mount fluvial by or sea dune the of stabilization by formed faces Cedar Mesa, layers of eolian sand are separated by thin sur the Within 1983). (Loope, limestone with interbedded are Below the Cedar Mesa interval, layers of eolian sandstones 2000). others, and (Stanesco Formation OrganRock the in sandstones red primarily the and Sandstone Mesa Cedar the in seen coloring salmon distinctive the gives that rial vial networks and corresponding flooding resulted in mate white sands derived from the northwest. The extensive flu resistant and mountains Uncompaghre ancestral the from pebbles and sand arkosic red eroded easily of layering or consist of the Cedar Mesa Sandstone that represents mixing today,seen as pinnacles, extensive District’s Needles The 1985). 1983, (Loope, Sandstone Mesa Cedar the of top the to Formation Halgaito the from extending beds limestone in resulting basin, the flooded periodically seas Extensive ago and from eolian sands derived from the west and north. compaghre mountains from about 305 to Un 260 million years the of erosion the to due northeast the from derived Uncompaghre Highlands. marine limestone, and fluvial strata derived in part from the and shore sands, marine and eolian of consist formations 1997). the (Condon, and Sandstone tion, Rim These White Forma Rock Organ the Sandstone, Mesa Cedar the tion, The pinnacles, therefore, are alternating red and white The Paradox Basin salt was overlain by clastic debris ------diate strata of Cedar Mesa eolian sandstone that have been have that sandstone eolian Mesa Cedar of strata diate interme the visualizing when obvious most is This 2000). (Baars, blocks rhomboidal into Sandstone Mesa Cedar the of fracturing surface extensive the for responsible are and The two joint systems are oriented northwest and northeast Stevenson,1981). and (Baars fields stress ancestral dicular cles thatwereinitiallymoreresistantcrossedthegrabens. rocks except in certain cases, as noted below, where pinna ly, within the grabens little is seen of the original overlying out the region, especially in the graben canyons. Important others, 2003). Graben formation hastened erosion through and Grosfils 1999; Schultz, and (Moore Lane) Devils and Canyon Cyclone in meters 60-90 to (up sands deposited eolian with covered were regions faulted down the within Rocks passageways. canyon long the creating wide meters hundred one as much as zone down-faulted a of consists and Schultz, 1999; Grosfils and others, 2003). Each graben 1987), but others have proposed a much earlier age (Moore and Adams, (Biggar ago years 50,000 has at constrained been formation graben for age earliest of The westward Park. and Chesler River Colorado the to parallel mainly sion of the softer shales of the Organ Rock Formation ex Formation Rock Organ the of shales softer the of sion ed remnantsthat wereinduratedbyformer streambeds. the western side of the Monument upwarp are the less erod streams themselves. It is hypothesized that the pinnacles on cles and parks. These sinuous pinnacles are reminiscent of pinna the of foundation geomorphological the describes upwarp Monument the of side western the traversing cles to streamerosion. linked directly not are and area the across meander nacles pin the located, are grabens and parks the where upwarp es of each canyon. In contrast, to the west of the Monument the pinnacles appears to be distinctly related to the drainag of pattern The canyons. distinct forming Sandstone, Mesa Cedar the through cut clearly have River Colorado the to north run that streams the Toeast the upwarp. Monument also distinct between the regions to the east and west of the eastern edge of each of the parks. The erosional patterns are the borders that pinnacles of row major a parallels exactly orientation surface in change The flat. is parks the the of east to region the while River Colorado the toward ward down slope generally upwarp Monument the of west the part of the Needles District is that the parks and the area to sponsible forformationoftheovalshapepinnacles. re are patterns joint same These 7). and 6 (figures beyond and the River Colorado the near to Center VisitorDistrict Needles Park Squaw from landscape the across stools” “toad or “mushrooms” rhomboidal white form to eroded nelig l o tee rcse ae w perpen two are processes these of all Underlying Following the erosion of the Colorado Plateau, ero Plateau, Colorado the of erosion the Following It is proposed that the serpentine pattern of the pinna Park/graben Chesler the of distinction principal A UGA Publication 43(2014) HYPOTHESIS —Geology of Utah'sFar South ------HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF –

Figure 6. Aerial photo of Chesler and Virginia Parks showing resistant “mushroom” layer of sandstone. Direction of view is north. Photo by Owen Severance. Denis, C.L . Figure 7. Aerial photo of Devils Lane and resistant mushroom layer of sandstone. Direction of view is north/northeast. Photo by Owen Severance.

MacLean, J.S., Biek, R.F., and Huntoon, J.E., editors 31 32 HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L. areas. There is no evidence, however, for increased fractur park the of erosion to leading rocks of fracturing creased below thecorrespondinglayer inthesurroundingrocks. the case, as the remnants lie locally at least 20 to 30 meters not is this downfaulting, graben or structures collapse of case the In pinnacles. surrounding coeval the in the layers sandstone as level horizontal same the on are parks the of all of interior the within remnants sandstone as rocks, layer.overlain the of collapse by formed not are parks The salt Basin Paradox the in salts of dissolution by are generated and 1981) Kitcho, and (Sugiura Park National Canyon lands around and in sporadically occur do structures Collapse structures. collapse of result the or faulting down grabens, representing sunken basins modeled on the graben Cyclone Parklackthesedistinctsalmoncoloredrocks. of perimeter the of south and north, west, just areas other contrast, In Park. Cyclone surround sandstone, hardened of layer rocks, “mushroom” the above pinnacles colored of remnants the salmon however, 8, figure in marked As Lane. Devils of west area graben the in occurred erosion has that extensive the to due sides south and east, north, its bordering pinnacles of row Cyclone distinct a only lacks today Park mentioned, parks the Of Parks. Devils in Chesler,Virginia,in and noticeable most pinnacles, of der bor eastern the at deposited and west the from transported sands modern of accumulations has substantial from grasslands resulted park the of Each above. described rocks “mushroom” resistant the up makes that sandstone the of there are small grasslands, but the bulk of the area is the top South and North Park Devils at pinnacles tall the beneath park-like areas consist of less grassland area. For example, plain. the above the that except similar are parks other The meters 200 approximately rise pinnacles These pinnacles. Sandstone Mesa Cedar the by surrounded plain eroded an Mesa Sandstone. Cedar the cemented selectively that minerals ried from ancient streambeds in the Organ Rock Formation car down percolating water the which in relief topographical inverted of instance an therefore, represent, pinnacles The pinnacles. of patterns sinuous were mushrooms of layer Needles District). The major stone elements left above this the of section this cross that rocks “mushroom” the of top the often (most sandstone of layer hardened particularly a to eroded further became Sandstone Mesa Cedar rated indu less upper the region, this in upwarp Monument the of side western the On Sandstone. Mesa Cedar the posed INVERTED TOPOGRAPHICAL RELIEF EVIDENCE FOR THE PINNACLES AS nte psil cue f h prs ol b in be would parks the of cause possible Another Day (2004) suggested that the parks are similar to the to similar is it that is Park Chesler of feature key The Park Formation ------such process is due to diagenetic calcrete (predominantly calcrete diagenetic to due is process such derives from increased cementation of the sandstones. One that is more resistant than nearby materials. This resistance stone contains caprock the exist, features Where erosion. ogy depend critically on the resistance of different strata to they noterodedtothesamelevelasparks? have why and resistant, more pinnacles the are why then, becomes, question The pinnacles. the element, second the a possible explanation for their existence must derive from the parksaredefinitelyovalinshape. and 2009), Selby, and (Howard patterns erosional shaped Moreover,sures. talon- created have would erosion stream enclo circular large their form to parks the caused have could that parks the of any for regions pinnacle the of tops the of any from emanating rivers or streams no are There upwarp. Monument the of side western the on extensively place take not does down-cutting stream example, For ing. River channels resulted in preservation of the channel and channel the of preservation in resulted channels River Gilbert the of induration the addition, In 1983). (Lattman, calcretes forming to conducive especially is cycle wet/dry intermittent This 2002). others, and (Huntoon down laid was Formation Rock Organ the when present climate ed dryness alternating with wet seasons, similar to the predict of spells seasonal to subject was that region semi-arid a in occurred This 2005). others, and (Nanson years 15,000 to Gilbert River in Australia have been hardened within 4,000 the of reaches middle the Recently, 1985). Goudie, 1983; (Lattman, today locations many in occurring is that tion forma calcrete the to conducive especially be to known is precipitation of 100 mm to 500 mm (considered semi-arid) annual An period. time particular a to hardness of degree relate to difficult is it material, cemented of type the and carbonate, calcium of availability the topography, mate, cli on depends hardening of rate the Because mentation. ce calcrete of months six within occurring process, rapid rather thanthecalcretes(calciumcarbonates). ferricrusts in resulting carbonates iron were chemicals ing harden the however, case, that In relief. topographical ed invert of mesas meandering creating as India in riverbeds behavior,this of ancient described (2008) Sheth and Ollier example an As percolation. downward this from resulted ity of the induration observed in the Cedar Mesa Sandstone themajor as cause, and Dixon and McLaren (2009) proposed the major water overlying of downflowing proposed (1983) Lattman rivers. or ponds, streams, as such water, overlying of downflowing from or groundwater of welling up either from generally derives hardening this for cause try of carbonate and other minerals into sandstones and the en The formation. sandstones) of cementation carbonate h vre faue aprn i dsr geomorphol desert in apparent features varied The then regions, eroded excessively not are parks the If Lattman (1983) showed induration to be a relatively a be to induration showed (1983) Lattman Induration ofSandstoneandCalcrete UGA Publication 43(2014) Formation —Geology of Utah'sFar South ------HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF –

Figure 8. Satellite map of Cyclone Park with pinnacle remnants. The dots indicate where salmon-colored sandstone exists above the layer of rhomboidal “mushroom rocks.” precluded extensive changes in channel placement. Once Moreover, the predicted climate at the time of Organ induration begins to take place, therefore, it results in chan- Rock Formation deposition was that of alternating dry/wet nel entrenchment. More distal reaches of the river, closer seasons in a semi-arid climate (Huntoon and others, 2002). to the sea and lacking sufficient slope, do not display indu- The location of the present Colorado Plateau region at that ration and instead form meandering riverbeds without en- time was on the western edge of Pangea at about 10° north trenchment. In contrast, upstream reaches of the river with of the equator. A change to a monsoonal weather pattern more rapid movement of water do not result in the periodic during the Late Pennsylvanian Period would have ensured drying/wetting cycle that seems critical for calcrete forma- that continental moisture-bearing winds bypass the Colo- tion. rado Plateau region, creating a climate of increased aridity and seasonal precipitation for the region (Dubiel and oth- Evidence of Pinnacles Resulting from Organ ers, 1996; Huntoon and others, 2002). The extensive eolian Rock Formation Stream Beds dune fields of Cedar Mesa and White Rim Sandstones support these observations. During the Organ Rock deposition, The strata directly overlying the Cedar Mesa Sand- however, the presence of both paleosols and rhizoliths sug- stone at the top of the present day pinnacles are Organ gests an alternating wet/dry climate. These characteristics Rock Formation shales and sandstones deposited in fluvial of semi-aridity, alternating wet and dry seasons, and me- systems deriving from the Uncompaghre uplift in western dium bed-loaded rivers are conducive to calcrete formation Colorado (Cain and Mountney, 2009). These fluvial sys- and fit a similar model as proposed for the Gilbert River in- tems had moderate inclines on a coastal plain of low-relief duration that has taken place in the last 15,000 years (Nan- and were not subject to extensive flooding characteristic of son and others, 2005). meandering streams (as observed further distal and south Evidence in support of low levels of seasonal pre- of the Uncompaghre mountains in White Canyon) (Sta- cipitation at the time these rivers were extant derives also nesco and others, 2000; Huntoon and others, 2002; Cain from the measurements of the sinuosity of the present day

and Mountney, 2009). Especially in the Needles area, the pinnacles. River sinuosity has been directly correlated with Denis, C.L streams of medium bed-load appear braided, which is very increasing storminess of the climate, irrespective of the similar to the braided pattern of pinnacles seen throughout underlying rocks through which the rivers run (Stark and . the Chesler Park/graben area (figure 5) (Stanesco and oth- others, 2010). The calculated sinuosity (curvature divided ers, 2000). by linear distance covered) for the pinnacles is 1.1 (stand-

MacLean, J.S., Biek, R.F., and Huntoon, J.E., editors 33 34 HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L. in the eastern zone of the Maze District. The comparable The District. Maze the of zone eastern the in streams these of relief) topographical inverted of results one might expect to observe pinnacle remnants (that is, the 1997), (Condon, District Maze day present the of reaches western the in present was flowed have would paleorivers trends thatthepinnaclestake acrossthegrabenarea. directional same the are These northwest. and west the to streams the forced have would Formation Rock Organ the within Mesa Sandstone Cedar the over flowed rivers the time the at upwarp Monument the of presence The times. erosional material particular deriving from any the structure at of subsequent lack the by evidenced is relief low was times these of any during upwarp paleo-Monument the of structure the That 1997). (Condon, River Green the with confluence day present the of south just ending and River Colorado the to parallel structure relief low a supporting it becomes absent in the present day Needles District, again fact, In west. the from River Colorado the approaches it as thinned noticeably is Formation, Rock Organ the overlies which Sandstone, Rim White the Furthermore, 2000). ers, oth and Stanesco 1997; (Condon, upwarp Monument tral ances an of presence the suggests Needles the of areas in material this of thinning deposition, Formation Rock gan Or during Similarly, 1985). (Loope, Mesa Cedar the out through levels sandstone between deposited limestones of layers many the by evidenced as 1997), (Condon, region Corners Four the throughout area topographical low tively rela a considered be still should what in Sandstone Mesa ment upwarp continued through the deposition of the Cedar 1997). The slight positive elevation of this ancestral Monu (Condon, time that at present and active was upwarp ment particularly sparse in this region, suggesting that the Monu and Colorado Rivers: deposition of the lower Cutler beds is Green day present the of confluence the to nearly ran that positive topographical formation was present in this region locally a that apparent was it Sandstone, Mesa Cedar the beneath beds Cutler lower the of deposition the during ago years million 300 as River.early Colorado As day present the of location the overlapping perhaps and to parallel tion not direc northeast slightly are a in run have to appears it known, elevation and location exact its Whereas 2000). others, and Stanesco 1996; others, and (Dubiel Rock Formation Organ the of time the at feature positive slightly a path. their with Studies have shown that the ancestral Monument interfered uplift was something unless southwest directed been have should they uplift, Uncompaghre the from emanating were they Since 2000). others, and nesco (Sta District Needles the of vicinity the in northwest and at the time of the Organ Rock Formation, they trended west was nearzeroforthesesandstone-embeddedrivers. time a at mm 50 than greater precipitation of and events weather stormy of likelihood the that suggests value sinuosity of low This segments). sixteen for 0.015 of error ard Because the sea to which these Organ Rock Formation Importantly, based on the deposition from these rivers ------grabens at a number of locations. They cross Devils Pocket the cross pinnacles the that in formation graben predate to appear pinnacles The salt. Paradox the into cut first River Colorado the when time the to prior areas less-eroded and pinnacles the that adjacent the to compared obvious and visible already were likely is It 2007). others, 2003; and Schulz-Ela, Furaya and (Walsh River Colorado the eastward from spread and developed rifts graben the as years 500,000 last the within accelerated exceedingly was today sides oftheColoradoRiver. both on connected been readily have probably would cles the grabens,pinna surface createdduringtheformationof erosional vast the for Except induration. paleostream same the of part were they that suggesting pinnacles, Dollhouse the to northwestward continue to appear Park) Chesler of north just (present Pinnacles Devils the fact, In 3). (figure Pinnacles Devils the do as trend northwest same the low fol River Colorado the of west just pinnacles Dollhouse erosion, resulting in the sinuous pattern of pinnacles that pinnacles of pattern sinuous the in resulting erosion, this resisted Sandstone Mesa Cedar indurated The region. Park/graben Chesler the of erosion mass significant in ed underlying the Cedar Mesa Sandstone of this region result Formation Paradox the into cutting River Colorado the by caused erosion subsequent the and Plateau Colorado the of durated the underlying Cedar Mesa Sandstone. The erosion in that Formation Rock Organ overlying conformably the in streambeds of result the be to interpreted is area graben Colorado the River, probablycommencing5to50million yearsago. of incision the during formed have would drainages current The area. Park/graben Chesler the in es drainag current the before long place took pinnacles the formed that process the suggest observations These ‘C’). (marked once Canyon ‘A’ Chesler and 4) ‘B’figure and in (marked twice this Canyon Elephant cross rows Pinnacle in area. streambeds day present the of course the predate meters lower. nacles on the adjoining horst sections, albeit now dozens of pin the with contiguous once were grabens these of each in pinnacles the that verify Sandstone Mesa Cedar of ers lay successive the of stratification the of curred. Analysis these oc formation Thus, graben when present already were pinnacles 9). figure Pocket, Devils for cases three all and 10, figure Lane, Devils north (see graben the in tant ex still are pinnacles the cases above the of several In G). and F (points twice Canyon Cyclone and E), and D (points twice least at Lane Devils C), to points A 9, (figure thrice The erosion that helped create the pinnacle relief seen The sinuous pattern of pinnacles in the Chesler Park/ Chesler the in pinnacles of pattern sinuous The to appears also pinnacles the of pattern sinuous The Timing ofPinnacleFormation UGA Publication 43(2014) CONCLUSIONS —Geology of Utah'sFar South ------HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF –

Figure 9. Satellite map of grabens with pinnacle crossings. Letters ”A” to ”G” indicate locations where the pinnacles clearly cross the grabens. Down fallen pinnacles are most obvious at points ”A” to ”D.” Denis, C.L

Figure 10. Aerial view of northern Devils Lane looking southwest. The rhomboidal sandstone blocks in the forefront and upper right are . the mushroom sandstone level described in the manuscript. The sinuous pinnacles marked “A” crossing the grabens are located at the north end of Devils Lane (marked ”D” in figure 9). Cyclone Canyon is seen in the upper right part of the picture. Photo by Matt Sobey.

MacLean, J.S., Biek, R.F., and Huntoon, J.E., editors 35 36 HYPOTHESIS: THE PINNACLES OF THE CHESLER PARK/GRABEN REGION OF CANYONLANDS NATIONAL PARK RESULT FROM PALEOSTREAM INDURATION AND INVERTED TOPOGRAPHICAL RELIEF – Denis, C.L. Langford, andJacquelineHuntoon. als: Richard Schulz, David Loope, Russell Dubiel, Richard individu following the by manuscript this and hypothesis this on comments for grateful especially also am I McGill. George with conversations in Amherst, Massachusetts, of University the of Wise Don by suggested was hypothesis streambed inverted initial The region. this of exploration aiding in support critical for Goetze Chris Turnerand Bud for numerous photos of the area. I am especially indebted to deposition of the Organ Rock Formation. the of time the at present lakes small by Sandstone Mesa Cedar underlying the of induration of result the be could interspersedparksareMolehillthethat Mesa, withas such mesas, the of formation The region. this of features other for responsible be also may induration of type This this area. in parks several the of enclosures circular-like form Driese, S. D., Medaris, L. G., Minghua, R., Runkel, A., Lang A., Runkel, R., Minghua, G., L. Medaris, D., S. Driese, Duricrusts, 2009, S.J., McLaren, and J.C., Dixon, Trails Jeep Favorite Park National Canyonlands 2004, Day,D., S. 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