Arches National Park 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2004/005 

National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 
THIS PAGE: THIS PAGE: 

Canyon, Arches NP. Canyon, Arches NP.

ON THE COVER: ON THE COVER: 

Delicate Arch, Arches NP

NPS Photo’s NPS Photo’s
Arches National Park 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2004/005 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 

November 2004 

U.S. Department of the Interior 

Washington, D.C.
The Natural Resource Publication series addresses natural resource topics that are of interest 

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gre_publications) on the internet, or by sending a request to the address on the back cover. 

Please cite this publication as: 

Graham, J. 2004. Arches National Park Geologic Resource Evaluation Report. Natural 

Resource Report NPS/NRPC/GRD/NRR—2004/005. National Park Service, Denver, 

Colorado. 

NPS D-197, November 2004 
 ARCH Geologic Resource Evaluation Report iii

Table of Contents 

List of Figures .............................................................................................................. iv

Executive Summary ...................................................................................................... 1

Introduction ................................................................................................................... 2

Purpose of the Geologic Resource Evaluation Program ............................................................................................2

Regional Information ..................................................................................................................................................2

Park History................................................................................................................................................................2

Geologic Setting .........................................................................................................................................................3

Geologic Issues............................................................................................................. 5

Hydrocarbon Development.........................................................................................................................................5

Uranium Mining ..........................................................................................................................................................5

Water Quality and Flash Flooding ..............................................................................................................................6

Preservation of Fossils ...............................................................................................................................................6

Other Geological Issues .............................................................................................................................................6

Research Projects ......................................................................................................................................................7

Interpretive Needs ......................................................................................................................................................7

Geologic Features and Processes............................................................................... 8

Formation Properties.................................................................................................. 16

Geologic History.......................................................................................................... 28

Depositional and Tectonic History ............................................................................................................................28

References Cited......................................................................................................... 41

Appendix A: Geologic Map and Cross Section ........................................................ 45

Appendix B: Scoping Summary................................................................................. 47

Attachment 1: Digital Geologic Map CD 
 NPS Geologic Resources Division iv 

List of Figures 

Figure 1: Location Map for Arches NP ...........................................................................................................................4

Figure 2: Entrada Sandstone Fins................................................................................................................................11

Figure 3: Schematic Diagram of Arch Formation. ........................................................................................................11

Figure 4: Schematic Diagram of Salt Anticline and Dissolution Structures ..................................................................12

Figure 5: Landscape Arch. ...........................................................................................................................................13

Figure 6: Balanced Rock..............................................................................................................................................13

Figure 7: Skyline Arch. .................................................................................................................................................14

Figure 8: Fiery Furnace................................................................................................................................................15

Figure 9: Stratigraphic Column.....................................................................................................................................25

Figure 10: Correlation Chart of Jurassic Period ...........................................................................................................27

Figure 11: Pangaea......................................................................................................................................................34

Figure 12: Lower Triassic Paleogeographic Map .........................................................................................................35

Figure 13: Upper Triassic.Paleogeographic Map .........................................................................................................36

Figure 14: Middle Jurassic Paleogeographic Map........................................................................................................37

Figure 15: Map of the Cretaceous Seaway. .................................................................................................................38

Figure 16: Upper Cretaceous Paleogeographic Map ...................................................................................................39

Figure 17: Geologic Time Scale...................................................................................................................................40
 ARCH Geologic Resource Evaluation Report 1

Executive Summary 

This report has been developed to accompany the digital geologic map produced by Geologic 

Resource Evaluation staff for Arches National Park in Utah. It contains information 

relevant to resource management and scientific research. 

The 76,359 acres of Arches National Park (ARCH) in 

east- central Utah preserves the greatest concentration of 

rock arches in the world. In addition to the arches, 

Arches National Park is home to an extraordinary 

collection of balanced rocks, salt dissolution structures, 

folds resulting from salt tectonics, petrified dune fields, 

and a maze of deep narrow canyons. 

Mesozoic sedimentary rocks are the primary strata 

exposed in ARCH. Arches formed mainly within the 

Entrada Sandstone, which was deposited about 150 

million years ago. The arches result from a continual 

process of weathering and erosion, and they accent the 

significant role that water plays in a semi- arid climate. 

Fins are the result of salt tectonics and wind and water 

erosion. Salt- cored anticlines form prominent features 

in ARCH. 

Geologic resource issues arise in the park due to the 

heterogeneous lithology of the rock strata, weathering 

and erosion processes, and human influence. These 

issues impact road construction and maintenance 

projects, groundwater quality, and visitor protection. 

The list of geologic issues includes: 

• Hydrocarbon development 

• Uranium mining 

• Water quality and flash flooding 

• Preservation of fossils 

• Landslides and rockfalls 

• Swelling clays 

• Radon contamination 

• Earthquakes 

• Sonic booms and arch stability 

• Livestock grazing effects on soils 

• Proposed toxic waste incinerator impact on geologic 

features 

• Viewshed issues (dust, oil/gas development) 

• Acid rain impacts 

• Preservation of Cryptobiotic soils 

Scientific research projects suggested for the park 

include: 

• Evaluation of acid rain impacts on deterioration of 

the sandstone arches 

• Connections between gypsiferous rocks and 

cryptobiotic soils 

• Erosion rate of Delicate Arch 

• Engineering studies of landslides 

• High resolution GPS and rock movement 

• Rock color studies 

• Void spaces in the Needles 

• Stratigraphic studies to identify unconformity 

contacts, planes of weaknesses, and 

porosity/permeability relationships of various strata 

• Inventory, monitoring, and protection of 

paleontological resources, especially in the Dalton 

Wells area 

• Hydrogeologic studies to identify groundwater flow, 

aquifers, and potential groundwater contamination 

For additional information regarding the contents of this 

report contact the Geologic Resources Division of the 

National Park Service, in Denver, Colorado, through the 

following website: http://www.nature.nps.gov/geology, 

or by calling 303- 969- 2090. 
 NPS Geologic Resources Division 2 

Introduction 

The following section briefly describes the regional geologic setting and the National 

Park Service Geologic Resource Evaluation program. 

Purpose of the Geologic Resource Evaluation Program 

Geologic resources serve as the foundation of park 

ecosystems and yield important information needed for 

park decision making. The National Park Service Natural 

Resource Challenge, an action plan to advance the 

management and protection of park resources, has 

focused efforts to inventory the natural resources of 

parks. The geologic component is carried out by the 

Geologic Resource Evaluation (GRE) Program 

administered by the NPS Geologic Resources Division. 

The goal of the GRE Program is to provide each of the 

identified 274 “Natural Area” parks with a digital 

geologic map, a geologic evaluation report, and a 

geologic bibliography. Each product is a tool to support 

the stewardship of park resources and each is designed 

to be user friendly to non- geoscientists. In preparing 

products the GRE team works closely with park staff and 

partners (e.g., USGS, state geologic surveys, and 

academics). 

The GRE teams hold scoping meetings at parks to review 

available data on the geology of a particular park and to 

discuss the geologic issues in the park. Park staff are 

afforded the opportunity to meet with the experts on the 

geology of their park. Scoping meetings are usually held 

in each park individually to expedite the process 

although some scoping meetings address multiple parks 

within a Vital Signs Monitoring Network. 

For additional information regarding the Geologic 

Resources of Arches National Park, see the Geologic 

Resources Division website at: 

http://www2.nature.nps.gov/geology/parks/arch 

Regional Information 

Over two thousand natural sandstone arches, the 

greatest concentration of rock arches in the world, are 

preserved in Arches National Park (ARCH). This 

74,000- acre park is located 5 miles (8 km) north of 

Moab, Utah, along Highway 191 and is about 25 miles 

northeast of Canyonlands National Park (figure 1). In 

addition to the arches, a collection of balanced rocks, 

fin- shaped rock features, rock pinnacles, folded rock 

strata draped over salt diapirs, stark exposures of 

millions of years of geologic history, petrified sand dunes 

that once swept across a desert landscape millions of 

years ago, evidence of a sea that once drowned eastern 

Utah, and a maze of deep narrow canyons grace the park. 

Cultural History 

Water, or the lack thereof, and the harsh landscape have 

long discouraged settlers to the area. Prehistoric huntergatherers migrated into the area about 10,000 years ago at 

the end of the Ice Age. They explored the area and found 

pockets of chert and chalcedony, microcrystalline 

quartz, and used these minerals to make stone tools. 

About two thousand years ago, agriculturalists, known as 

the ancestral Puebloan and Fremont people, entered the 

Four Corners region and began to raise maize, beans, and 

squash. Villages of these people were similar to those 

preserved in Mesa Verde National Park in southwestern 

Colorado. None of their dwellings, however, have been 

discovered in Arches. Instead, these ancestral settlers left 

pictographs on the rock to mark their passing and lithic 

fragments around waterholes where they may have 

shaped tools as did the people before them. Both the 

Fremont and the ancestral Puebloans left the region 

about 700 years ago. 

The first Europeans to explore the Southwest were 

Spaniards who crossed the territory in 1776. When they 

came into the country, they met nomadic Shoshonean 

peoples such as the Ute and Paiute. What they thought of 

the arches remains a mystery. Although the Old Spanish 

Trail linking Santa Fe and Los Angeles ran along the 

same route, past the park’s Visitors Center, that the 

highway does today, they left no written description of 

their impressions of the arches. The first reliable date 

regarding exploration within the Arches is from Denis 

Julien, a French- American trapper, who carved this 

description in the rocks, “Denis Julien, June 9, 1844”, but 

left no other impressions. 

The Mormons attempted to establish the Elk Mountain 

Mission in what is now Moab in 1855, but they 

abandoned the effort due to conflicts with the Utes. By 

the late 19th century, the United States government had 

restricted the Southern Ute Reservation to a small 

portion of southwestern Colorado so that ranchers, 

prospectors, and farmers permanently established the 

settlement of Moab in the 1880s and 1890s. A homestead 

cabin was built by John Wesley Wolfe, a veteran of the 

Civil War, in 1898 but was abandoned ten years later 

when he and his family returned to Ohio. The cabin 

remains on Salt wash, at the beginning of the Delicate 

Arch Trail. 

Establishment of Arches National Park 

In 1911, a young man, Loren “Bish” Taylor became owner 

of the Moab newspaper and began writing about the 

marvels of Moab and the rock wonderland just north of 

the frontier town. He explored the area with John “Doc” 

Williams, Moab’s first doctor whose name graces Doc 

Williams Point that overlooks a series of rock fins. Word 
 ARCH Geologic Resource Evaluation Report 3

spread until the government eventually sent research 

teams to investigate the area and to gather evidence to 

support preservation. In 1929, President Herbert Hoover 

signed the legislation creating Arches National 

Monument to protect the arches, spires, balanced rocks, 

and other sandstone formations. Notably, this was in the 

midst of intense oil exploration in southeastern Utah 

during the 1920s but about twenty years prior to the 

uranium boom that would strike southeastern Utah after 

World War II. Soon after the monument was created, 

geologists began to take a serious look at Arches. Carle 

H. Dane (1935) was the first geologist to make a 

comprehensive geologic study of the area in 1935 as part 

of his Ph.D. dissertation. As the unique character of the 

area became more and more apparent, more geologists 

came to the area and more visitors began arriving to see 

the arches. Eventually, in 1971, Congress elevated the 

status of Arches to a National Park. 

Additional information may be found on the Arches 

National Park web site: 

http://www.nps.gov/arch/hist.htm. 

Geologic Setting 

Located in the southeastern corner of Utah, Arches 

National Park is part of a much larger geological feature 

called the Colorado Plateau Province. Covering parts of 

Colorado, Utah, Arizona, and New Mexico, the 

Colorado Plateau is a region of high plateaus, deep 

narrow canyons, and broad, rounded uplands separated 

by vast sage lands used for cattle grazing. Beneath the 

rangelands are large, elliptical basins. 

The structural fabric of gently warped, rounded folds 

contrasts with the intense deformation and faulting of 

the terranes bordering the Colorado Plateau. Northeast 

and east of the Colorado Plateau are the jagged peaks of 

the Rocky Mountains formed by thrust faulting. 

The extensional, normal- faulted Basin- and- Range 

Province borders the Colorado Plateau to the west and 

south. The Rio Grande Rift forms the southeast border. 

The sedimentary rock layers on the Colorado Plateau, 

while gently folded into anticlines and synclines, remain 

relatively undisturbed by faulting except in areas 

associated with salt tectonics. Within the park, the arches 

and many of the unique features are associated with 

northwest- southeast trending synclines, anticlines, and 

normal faults caused by the growth of salt structures and 

the subsequent dissolution of the salt. 

Salt (evaporite) deposits date from the Permian Period 

when a shallow sea covered the region. Upper Paleozoic 

through Mesozoic sedimentary rocks are exposed in 

ARCH or the immediate area (figure 9). 

The Entrada Sandstone, which forms the arches, was 

deposited about 150 million years ago during the Jurassic 

Period. The Entrada is about 300 feet (91 m) thick and is 

believed to have been deposited by the wind in a vast 

coastal desert. Upon hardening into rock, the Entrada 

Sandstone was uplifted and fractured. After erosion 

stripped away the overlying layers, the sandstone was 

exposed to weathering, and the formation of the arches 

began. 

The southern boundary of the park is outlined by the 

Colorado River. The Colorado River’s channel has 

incised obliquely across the folds suggesting that the 

river developed independently of any structural control 

from the surrounding features. These features are 

illustrated in Doelling (2000). 
 NPS Geologic Resources Division 4 

Figure 1: Location Map for Arches NP. From Doelling (2000). 
 ARCH Geologic Resource Evaluation Report 5

Geologic Issues 

A Geologic Resource Evaluation scoping session was held for Arches National Park and 

other NPS units located in southeastern Utah on May 24- 27, 1999, to discuss geologic 

resources, to address the status of geologic mapping, and to assess resource management 

issues and needs. The following section synthesizes the scoping results, in particular, 

those issues that may require attention from resource managers. 

Hydrocarbon Development 

The combination of salt, organic- rich shale, porous 

limestone and sandstone, pressure and time resulted in 

large accumulations of oil and gas in the Paradox Basin. 

There are several oil reservoirs in the basin, the most 

prolific of which are in carbonate algal mounds in the 

Pennsylvanian age Paradox Formation. Following 

deformation in the Late Cretaceous- Mid Tertiary 

Periods, oil generated from Devonian and/or 

Mississippian- age shales migrated into these porous 

carbonate reservoirs that were sealed by the overlying 

salt. The reservoirs are found in Laramide- age anticlines 

as well as in stratigraphic pinch- outs where the porous 

reservoir rocks grade into nonporous sedimentary rocks. 

Hydrocarbons have also been discovered in Devonian 

and Mississippian limestones and sandstones and in 

Jurassic and Cretaceous sandstones. 

The major hydrocarbon producing fields lie south of the 

Colorado River in southeast Utah. Lisbon field, the 

largest field in the vicinity of Arches National Park, lies 

about 48 km (30 mi) southeast of the park. The smaller 

Salt Wash field lies about 48 km (30 mi) northwest of the 

park. Long Canyon, Big Flat, and Shafer Canyon oil fields 

surround the northern end of the northwest- southeast 

trending Cane Creek anticline about 16 km (10 mi) 

southwest of the park (Fouret, 1996). There is also oil 

production southwest of the park in the vicinity of Dead 

Horse Point State Park. 

The location of abandoned oil and gas wells in the park, 

if any, is unknown. Apparently, no oil and gas fields were 

discovered in Arches National Park prior to its 

designation as a national monument in 1929 although 

extensive exploration occurred in the Four Corners area 

during the 1920s. A project statement, ARCH- N030.000, to locate any abandoned sites is contained in 

the Water Resources Management Plan prepared for 

Arches and Canyonlands National Parks (Cudlip et al., 

1999). 

Uranium Mining 

The Paradox Basin has also been the site of uranium 

mining for most of the past century. The nuclear arms 

race spurred the first “boom” in the 1950s and early 

1960s. A discovery of a large unoxidized ore deposit on 

the flank of Lisbon Valley anticline, southeast of the 

park, kindled public excitement in 1952 (Chenoweth, 

1996). A second, short lived, “boom” came in the late 

1970s and early 1980s as a result of interest in nuclear 

power plant fuel. 

Although uranium ultimately comes from igneous rocks, 

the principal host rocks for the radium, vanadium, and 

uranium deposits are fluvial deposits in Mesozoic rocks. 

The principal host rocks are the Salt Wash member of 

the Jurassic Morrison Formation and the Triassic Chinle 

Formation. The ore bodies in the Salt Wash member 

consist of concentrations of uranium and vanadium 

minerals within the fluvial sandstones. Miners also 

sought fossilized logs because carnotite, a potassiumuranium vanadate, typically replaced the original organic 

material in the wood (Chenoweth, 1996). In the Chinle, 

gray, poorly sorted, fine- to coarse- grained, calcareous, 

arkosic, quartzose sandstone contains the uranium ore. 

With decreased interest in nuclear energy, a decrease in 

nuclear arms proliferation, foreign competition, and 

excess inventories of uranium worldwide, prices for 

uranium ore declined and with them, the interest in 

uranium mining. The impacts of uranium mining, 

however, remain. On the northwest bank of the 

Colorado River, southeast of Arches Headquarters and 3 

km (1.9 mi) northwest of Moab, sits the mill site and 

associated tailings of the now decommissioned Atlas 

Corporation Moab Mill Site. The site includes 400 acres 

(162 hectares) of processing facility, tailings pond and 10.5 

million ton (9.5 million metric ton) tailings pile (Cudlip et 

al., 1999). Cudlip et al., 1999, outlined two concerns over 

the mill site: 1) an elevated ammonia level in the Colorado 

River downstream of the pile, and 2) potential 

radioactivity in the form of alpha particle levels in the 

primary drinking water well at Arches Headquarters. 

While groundwater typically flows from the northwest to 

the southeast towards the Colorado River, the water 

level within the tailings pile is above the alluvial 

groundwater, and hydraulic pressure variations within 

the pile may change the flow patterns under the mill and 

tailing site. 

Although no official documents are known to date that 

identify the Atlas tailings pile as an issue, the eventual 

disposition of this tailings pile “will definitely affect 

Arches National Park, whether the pile is moved or 

capped” (comments from ARCH staff, July 9, 2003). 

Uranium mining has also occurred elsewhere in the area, 

particularly in the Yellow Flat area northeast of the park. 
 NPS Geologic Resources Division 6 

Water Quality and Flash Flooding 

Water plays a key role in defining and shaping the desert 

landscapes that encompass Arches National Park. The 

climate of Arches National Park is classified as semi- arid 

to arid. Typically, annual precipitation is less than 20 cm 

(8 in). The park has distinct winter and summer 

precipitation maxima (Cudlip et al., 1999). The summer 

rainy season in July and August results from an influx of 

monsoon air from the south. During the winter, 

infrequent intrusions of Pacific air bring snow. Potential 

evaporation can equal 101 cm/yr (40 in/yr). 

Because of the low precipitation and high evaporation 

rates, recharge rates to groundwater are low. The 

Entrada, Navajo and Wingate sandstones serve as 

aquifers and are underlain by relatively impermeable 

strata. The groundwater may be Pleistocene in age and if 

so, the groundwater system is vulnerable to permanent 

drawdown (Cudlip et al, 1999). Groundwater mining for 

park operations, therefore, must be carefully managed. 

Because many of the formations underlying Arches 

National Park were deposited in marine environments, 

the natural dissolved solids content in groundwater is 

high and affects water quality. The water well for the 

park headquarters, for example, is in the Navajo 

Sandstone and is relatively high in both dissolved solids 

content and high specific electrical conductance (see 

Cudlip et al., 1999, for water quality data). Since current 

flows in ionized or mineralized water, high specific 

conductance translates into high mineral content. 

Springs and seeps in Arches are not large but provide a 

vital source of water for wildlife, aquatic organisms, 

vegetation, and visitors. Discharge is typically low from 

these seeps and springs. In Arches, the seep line between 

the Moab member of the Curtis Formation and the Slick 

Rock member of the Entrada Sandstone supports 

hanging gardens containing a myriad of endemic plants 

and invertebrates (Cudlip et al., 1999). Groundwater 

removal from slowly recharged sandstone aquifers may 

impact these organisms. 

Flash flooding occurs in Arches National Park as a result 

of summer thunderstorms rather than spring snowmelt. 

During storm events, large amounts of water, debris, and 

sediment flow through channels and canyons cut by 

fluvial processes. Perennial streams in Salt Wash and 

Courthouse Wash drain into the Colorado River. 

After the storms pass, the streambeds again go dry; 

however, rainwater can still be found in the natural 

potholes that form in this slickrock country. Sculptured 

in the soft sandstone, these small catchment basins vary 

in size and carry water for a time after a storm depending 

on the intensity and duration of the storm, the size of the 

pothole, and the rate of evaporation. 

Water management is critical to Arches National Park. 

Water quality is affected by a number of sources 

including: 

• Salinity from salt dissolution by meteoric groundwater 

• Naturally high dissolved solids from geologic 

formations deposited in marine environments 

• Selenium from Mancos shale 

• Potential external threats such as increased impacts 

from irrigated agriculture, oil and gas development, 

and leaching from uranium mine spoil material 

All of these concerns are addressed in the Water 

Resources Management Plan: Arches National Park & 

Canyonlands National Park, Utah (Cudlip et al., 1999). 

Preservation of Fossils 

A detailed description of the paleontology and 

biostratigraphy of Arches National Park is beyond the 

scope of this report. A summary of some of the fossil 

discoveries within and near Arches may be found in A 

Survey of Paleontologic Resources from the National 

Parks and Monuments in Utah by Vincent Santucci 

(2000) and from the following references: 

Duffy, S., 1993, Synopsis of the dinosaur megatrack site in 

Arches National Park, in V. L. Santucci, ed., National 

Park Service Natural Resources Technical Report 

NPS/NRPO/NRTR- 93/11:4 

Engelmann, G. F. and Hasiotis, S. T., 1999, Deep 

dinosaur tracks in the Morrison Formation: sole marks 

that are really sole marks, in D. D. Gillette, ed., 

Vertebrate Paleontology in Utah: Utah Geological 

Survey Miscellaneous Publication 99- 1, p. 179- 183. 

Lockley, M. G., 1990, Tracking the Rise of Dinosaurs in 

Eastern Utah: Canyon Legacy 2: 2- 8. 

Lockley, M.C., Kirkland, J.I., DeCourten, F.L., Britt, B.B., 

and Hasiotis, S.T., 1999, Dinosaur tracks from the 

Cedar Mountain Formation of eastern Utah – a 

preliminary report, in D.D. Gillette, ed., Vertebrate 

Paleontology in Utah: Utah Geological Survey 

Miscellaneous Publication 99- 1, p. 253- 257. 

Mead, J. I., Sharp, S. E., and Agenbroad, L. D., 1991, 

Holocene Bison from Arches National Park, 

southeastern Utah: Great Basin Naturalist 51 (4), p. 

336- 342. 

Molenaar, C. M., and Cobban, W. A., 1991, Middle 

Cretaceous stratigraphy on the south and east sides of 

the Uinta Basin, northeastern Utah and northwestern 

Colorado: U.S.G.S. Bulletin 1787, 34 p 

Other Geological Issues 

The Southeast Utah Group (SEUG) Geologic Resources 

Inventory (GRI) Workshop held in 1999 identified the 

following potential geological issues related to the SEUG 
 ARCH Geologic Resource Evaluation Report 7

parks (Arches NP, Canyonlands NP, Hovenweep NM, 

and Natural Bridges NM) (SEUG, 1999). 

• Landslide and rockfall potential. These occasionally 

cause road problems, including road closures. The 

main road in Arches, just inside the Visitor’s Center, is 

of special concern. Rockfalls also occur in other areas 

of the park. Several large sandstone pieces fell from the 

bottom side of the span of Landscape Arch several 

years ago, the event was recorded by a tourist. 

• Swelling soils associated with bentonitic shale in the 

Chinle, Morrison, and Mancos formations. 

• Radon potential associated with mine openings. 

• Earthquake potential along the Moab Fault. 

In addition, a 1990 management report for Arches 

identified the following external threats that could cause 

damage to the geological resources in the park 

(Statement of Management, 1990): 

• Low flying military jet aircraft often cause sonic booms 

that could affect geological features. 

• Livestock grazing impacts springs, seeps, streams, and 

cryptobiotic soils in the park, in areas where there is 

no fencing. 

• Potential impact on geological features from a toxic 

waste incinerator proposed for Green River, Utah. 

Green River is on the northwest side of the park and 

the prevailing winds in Arches are from that direction. 

• Aesthetic impacts as a result of reduced visibility from 

dust and other particulate matter with increased 

potash mining and intrusions on the viewshed from 

regional oil and gas development. 

• Increased acid deposition from harmful chemicals and 

particulates produced by the Navajo Power Plant, 240 

km (150 mi) to the southwest; the Four Corners Plant, 

178 km (111 mi) to the southeast; and Emery and 

Huntington Plants, 150 km (94 mi) to the northwest. 

• Destruction of cryptobiotic soils by humans and 

livestock. 

Research Projects 

The SEUG/GRI workshop (1999) listed the following 

potential research topics: 

• The affect of acid rain on the deterioration of the 

sandstone arches 

• A study of the connections between gypsiferous rocks 

and cryptobiotic soils and crusts addressing why the 

crusts are healthier on gypsum- bearing rocks. 

• Erosion and weathering process study to determine 

how long Delicate Arch will stand. 

• Engineering studies of landslides and mass movements 

using a strain meter to assess hazards to visitors. 

• A project to measure and detect moving, swelling, and 

collapse of rock strata in areas of the park using high 

resolution Geographic Positioning System (GPS). 

• Studies focused on rock color. For example, some red 

rocks are the result of diagenetic processes and are not 

the result of oxidation while exposed at or near the 

surface of Earth. 

• Locate and map the unconformity between the 

Entrada Moab Tongue and adjacent formations. 

Additional geologic studies might focus on the following 

topics: 

• Identifying unconformity- bounded stratigraphic 

packages in order to better define the depositional 

systems in the past. The studies using the Book Cliffs 

outcrops, north of the park, could be used as models. 

• Detailed sedimentological analysis of the Cutler 

Formation in the region as well as geochemical and 

diagenesis analyses to study why the lower sandstones 

are mottled. 

• Hydrogeologic studies to define subsurface flow 

patterns, regional and local flow systems, and the 

conductivity and transmissivity of the various aquifers 

especially in relation to abandoned or operating mines 

within and adjacent to the park. 

• Paleontological resources need to be inventoried, 

monitored, and protected, especially in the Dalton 

Wells area. 

Interpretive Needs 

Two interpretive needs were addressed by the 

SEUG/GRI workshop (1999): 

• The development of more graphics and brochures 

emphasizing geology. These should target the average 

park enthusiast. 

• The possibility of hiring a full- time geologist to handle 

geologic issues for the SEUG.
 NPS Geologic Resources Division 8 

Geologic Features and Processes 

This section provides descriptions of the most prominent and distinctive geologic features 

and processes in Arches National Park. 

Arches, fins, salt structures, balanced rocks, folds, faults, 

and joints are displayed in Arches National Park. The 

greatest concentration of natural rock arches anywhere 

in the world grace the landscape of Arches National 

Park. In addition, few other areas in the world display the 

salt- tectonic and salt- dissolution features that are so 

magnificently displayed in Salt and Cache Valleys. The 

features are enhanced by colorful Mesozoic strata. 

Balanced rocks in the park are striking examples of 

features shaped by both wind erosion and solution. The 

arid climate discourages heavy vegetation and deep soils 

that would otherwise mask these features. 

The arches and fins at Arches National Park are the 

result of the dry climate, the massive brittle sandstones 

and their susceptibility to weathering, the vertical joints 

in the sandstones produced by folding, and the proximity 

of the sandstones to salt- cored anticlines undergoing 

dissolution. Most of the arches and fins are associated 

with the Entrada Sandstone and form where the 

formation overlies an anticline on which closely spaced 

parallel fractures developed. Good examples of 

solution- induced anticlines and Entrada Sandstone 

arches can be found at Klondike bluffs, Devils Garden, 

Fiery Furnace, and Herdina Park. Elephant Butte, in the 

Windows section of Arches National Park, is a remnant 

of Entrada Sandstone that arched over an anticline that 

was probably not formed by dissolution (Doelling, 1985). 

Because the Entrada Sandstone is a massive crossbedded 

sandstone, it is highly susceptible to a style of weathering 

called exfoliation wherein slabs of sandstone peel from 

the bedrock in a series of concentric layers (Harris et al., 

1997). The Slick Rock member of the Entrada Sandstone 

also is composed primarily of quartz grains that are 

cemented together by calcium carbonate (CaCO3). Rain 

water, charged with atmospheric carbon dioxide (CO2), 

forms weak carbonic acid that is very effective at 

dissolving CaCO3. When the cement dissolves, the 

individual sand grains accumulate on the surface of the 

parent Entrada Sandstone. 

Wind and water erosion focuses along the large joints, 

widening the gaps between the linear cracks, and carves 

fin- like structures in the large slabs of rock (figure 2). 

Further erosion of the fins creates large holes and arches 

out of the fins. The fins are assumed to have formed in 

response to the compressional tectonic forces during the 

Laramide Orogeny (Doelling, 2000). A discussion of the 

jointing in Arches National Park is found in Dyer (1983), 

Cruikshank (1993), and in Cruikshank and Aydin (1993). 

Water also seeps into fractures in the Entrada Sandstone 

and along the contacts with the Moab member of the 

Curtis Formation or the Dewey Bridge member of the 

Carmel Formation. Thin openings form along these 

partings (diagram A of figure 3). Fractures, created by 

tensional stresses in the rock, propagate upward into the 

overlying rock (diagram B of figure 3). Groundwater 

further dissolves the cement along these fractures until 

the roof of the opening collapses forming the typical 

stable arch form, neutralizing the stress, and inhibiting 

further collapse (diagram C of figure 3). Delicate Arch is 

an example of an arch formed by the contact of the 

Moab member with the Slick Rock member while 

Skyline Arch formed along a parting entirely within the 

Slick Rock member. The Windows Arch formed along 

the Dewey Bridge- Slick Rock contact. This arch enlarges 

with the erosion of the soft Dewey Bridge member 

(Doelling, 1985). 

Salt- cored anticlines (salt walls) trend northwestsoutheast through Arches National Park. The Salt Valley 

and the Moab Valley salt walls lie directly under 

anticlinal salt- cored axes. The salt walls that underlie 

Salt Valley, Cache Valley, and the Moab anticline in 

Arches are 3.2 km (2 mi) high, as much as 4.8- 6.4 km (3 to 

4 mi) wide, and 112 km (70 mi) long (Doelling, 2000). The 

Moab anticline plunges to the north and gradually dies 

out about 10 km (6 mi) northwest of Moab Valley. The 

Courthouse syncline borders the Moab anticline to the 

northeast. 

Abundant normal faults and joints parallel the trends of 

the Moab anticline, the Elephant Butte anticline, and the 

salt- cored anticlines in Salt Valley and Cache Valley 

(Doelling, 1985, 2000). 

The tilted and broken blocks of strata that parallel the 

salt valleys in ARCH are structural features resulting 

from the dissolution of subsurface salt. Development of 

salt dissolution structures mentioned above is illustrated 

in a series of diagrams in figure 4. In the first diagram, 

sandstones and shales bury the salt- rich, Pennsylvanian 

Period Paradox Formation. The layers are parallel until 

pressure change at depth causes the relatively plastic, 

buoyant salt to begin to flow upward through the rock 

column. The sedimentary strata above the salt are 

deformed into an anticline. Extensional fractures and 

normal faults develop along the crest and limbs of the 

anticline and allow water to seep downward through the 

cracks. When groundwater comes into contact with the 

salt, the salt dissolves. With dissolution, the overlying 

strata collapse and a graben valley is formed bounded by 

a normal fault. The Moab anticline, north of the 

Colorado River, is a good example of the collapse of the 

crestal part of a salt- cored anticline (Doelling, 1985). The 

strata in the hinge zone of the collapsed structure roll 

over into the graben, and large joints form to 

accommodate the movement. This process is illustrated 
 ARCH Geologic Resource Evaluation Report 9

along parts of Salt Valley, especially in the area of Fiery 

Furnace. 

Salt dissolution and salt flowage continue today. Unequal 

loading on the salt beds will cause salt to flow. Salt 

flowage may seal fractures, “heal” fault planes, fill in 

voids created by previous salt dissolution, and cause 

bulges to form at the surface. Because salt movement is 

slow, groundwater usually dissolves the salt before it 

reaches the surface. Today, the Colorado River controls 

salt dissolution by controlling the depth to which it 

allows fresh water to reach the salt, which, in turn, is 

controlled, by the depth to which the river has cut its 

canyon. 

Delicate Arch 

The Slick Rock member of the Entrada Sandstone forms 

the base and pedestals of this world- famous, freestanding arch while the Moab member of the Curtis 

Formation forms the bridge. The contact between the 

two is a plane of weakness along an unconformity. 

Delicate Arch has a horizontal span of about 10 m (32 ft) 

and a vertical span of 14 m (46 ft). The top of the arch is 

about 16 m (52 ft) over the base. 

Landscape Arch 

With an opening of 93 m (306 ft) wide and more than 27 

m (88 ft) high, Landscape Arch is the longest span in the 

park (figure 5) (Doelling, 2000). One end of the arch is 

only 1.8 m (6 ft) thick while in the center of the arch, the 

hump spreads 6 m (20 ft) wide and weighs thousands of 

tons. Originally, Landscape Arch began as a cliff- wall 

arch but is now classified as a free- standing arch. The 

arch is entirely encased within a fin of the Slick Rock 

member. 

The Windows Section 

Mostly free- standing arches, the Windows are massive 

arches formed in a wall of the Slick Rock member 

underlain by the Dewey Bridge member. Well known 

arches in this area include: the Parade of Elephants, 

North Window, South Window, and Turret Arch. This 

area is also a good place to see alcoves (Cove of Caves) 

and the erosional expression of the softer Dewey Bridge 

member of the Carmel Formation (Garden of Eden) 

(Doelling, 2000). 

Balanced Rock 

Balanced Rock (figure 6) is perched precariously near the 

Windows and is an excellent example of a feature shaped 

by wind and water (Harris et al., 1997). Weathered in 

place, the resistant block of Slick Rock sandstone 

“balances” on top of the Dewey Bridge member of the 

Carmel Formation that rests above the Navajo 

Sandstone. 

Park Avenue 

The bust of Queen Nefertiti and Popsicle Rock, two 

other balanced rocks, can be seen on the short, 1.3 km 

(0.8 mile) trail in the area of the Courthouse Towers. 

Two high monoliths of the Slick Rock member of the 

Entrada Sandstone underlain with the Dewey Bridge 

member of the Carmel Formation guard the entrance to 

the trail. The Three Gossips and the Organ can also be 

seen along the trail. Baby Arch, an opening in its 

developing stage, is at the end of the trail. 

Devils Garden 

A walk through the Devils Garden from the Fiery 

Furnace northward to Dark Angel along the northeast 

rim of Salt Valley reveals 123 arches, most of which are 

free standing or cliff- wall arches. Sand Dune Arch, 

Broken Arch, Tunnel Arch, Pine Tree Arch, Navajo Arch, 

Double O Arch, Landscape Arch (figure 5), and Skyline 

Arch (figure 7) are some of the more well- known arches 

along this 11.5 km (7.2 mi) round trip trail. 

The Great Wall 

A wall of Entrada Sandstone stretches for about 6.4 km 

(4 mi) along the highway from about a mile north of the 

Tower of Babel to Balanced Rock. Hidden along this wall 

are several arches, especially pothole arches (Doelling, 

2000). 

Klondike Bluffs 

Tower Arch is the most famous arch at Klondike Bluffs, 

an area of fins and exposures of the Entrada Sandstone 

on the southeast rim of the Salt Valley anticline. The 

Marching Men, another unique erosional feature, is also 

located in the Klondike Bluffs area (Doelling, 2000). 

Moab Fault 

The Moab fault is a major fault that parallels the Moab 

anticline just south of the Visitor’s Center. Drill holes 

have shown that this fault cuts through and parallels the 

middle of the 3.2 km (2 mile) wide Moab Valley salt wall. 

The block of rock on the northeast side of the Moab 

fault has dropped down relative to the block on the 

southwest side. At the Visitor’s Center, the 

Pennsylvanian Honaker Trail Formation rests against the 

Jurassic Entrada Sandstone, or in terms of ages, rocks 

deposited about 295 million years ago (Pennsylvanian) 

rest against rocks deposited about 150 million years ago 

(Jurassic). For such a situation to occur, displacement 

across the Moab fault was at least 732 m (2,400 ft) 

(Doelling, 2000). From the Visitor’s Center, two 

branches of the fault can be seen. Like the Moab fault, 

the primary movement along the swarm of normal faults 

located on the Moab anticline is down to the northeast 

relative to the southwest blocks (Doelling, 1985, 2000). 

The northern block has dropped down relative to the 

southern block on the normal fault located on the crest 

of the Elephant Butte anticline, also. Along the borders of 

Salt Valley and Cache Valley, normal faults are mapped 

on the surface with their down- dropped blocks on the 

valley side of the fault. Major normal faults, with 

displacements down to the northeast, have also been 

interpreted to exist in the subsurface along the crest of 

the salt- cored anticlines in Moab and Salt Valleys 

(Doelling, 1985, 2000). Where the normal fault in Salt 

Valley is exposed at the surface, isolated protrusions of 
 NPS Geologic Resources Division 10 

Paradox Formation caprock, covered by the upper 

Chinle Formation, form the southwest block of the fault, 

and these strata are juxtaposed against collapsed 

Mesozoic rocks on the northeast side of the fault 

(Doelling, 1985, 2000). Salt dissolution events have 

deformed Triassic through Cretaceous strata on the 

northeast side of the fault so displacement caused only 

by this fault cannot be accurately determined. 

Fiery Furnace 

The Fiery Furnace (figure 8) is a maze- like labyrinth 

between Entrada Sandstone fins at the south end of 

Devils Garden. Because the maze is so complex, firsttime visitors are recommended to accompany a ranger 

on a guided walk or obtain a printed trail guide. Former 

arches that have collapsed are also present in the maze 

(Doelling, 2000). 

Cache Valley 

The same salt wall extends under both Salt Valley and 

Cache Valley although the wall trends northwest under 

Salt Valley and east- west under Cache Valley (Doelling, 

2000). Cache Valley extends east of the park boundary 

and is the best place to view and study the effects of 

dissolution collapse. Unlike Salt Valley where the 

collapsed rocks are covered with unconsolidated 

Quaternary deposits, the collapsed rocks in Cache Valley 

are not buried. 

Elephant Butte Folds 

Several paralleling anticlines and synclines have 

developed on the southwest and south sides of Salt 

Valley and Cache Valley as dissolution collapse has 

begun on the crest of the Salt Valley- Cache Valley saltcored anticline (Doelling, 2000). The V- shaped 

synclines lie between sharp, linear anticlines. Eventually, 

the fold areas will become part of the Salt Valley- Cache 

Valley graben. Numerous talus piles of Morrison and 

Cedar Mountain Formation rocks line the axial areas of 

the synclines. These rocks once formed the cliffs that 

outlined the valley rims, but now, the cliffs have been 

eroded back several miles. The main paved road 

traverses the folds between Balanced Rock and 

Panorama Point. 

Petrified Dunes 

The Jurassic age sand dunes of the Navajo Sandstone are 

preserved in the area east of the Great Wall. The Navajo 

desert rivaled today’s Sahara Desert in size. Exposed on 

the bare- rock outcrops of the Navajo are sweeping 

high- angle crossbeds truncated by crossbed set 

boundaries. These ancient dunes were cemented into 

solid rock and when exposed on the surface, have been 

eroded into rounded domes called petrified dunes or 

frozen dunes (Doelling, 2000)
 ARCH Geologic Resource Evaluation Report 11

Figure 2: Entrada Sandstone fins. Joints at rollovers open and form fins along Salt Valley graben rims. Weakly cemented partings in 

fins can then weather into arches. From Doelling, 2000 

Figure 3: Diagrams illustrating the formation of an arch from a parting developing between the Entrada Sandstone and the Dewey 

Bridge member of the Carmel Formation. An explanation is in the text. Modified from Doelling, 1985. 
 NPS Geologic Resources Division 12 

Figure 4: Schematic diagrams illustrating the formation of salt anticlines and salt dissolution structures. See text for further 

explanation 
 ARCH Geologic Resource Evaluation Report 13

Figure 5: Landscape Arch with a span of 93 m (306 ft) is the longest span in the park. From Doelling (2000). 

Figure 6: Balanced Rock. Well-known and a central landmark in Arches National Park, balanced rock is a huge orange-brown bulb of 

the Slick Rock member resting on a narrow dark-brown pedestal of the Dewey Bridge member. From Doelling (2000). 
 NPS Geologic Resources Division 14 

Figure 7: Skyline Arch. The opening is 22 m (71 ft) wide and 10 m (33.5 ft) high. The arch is formed along a parting in the Slick Rock 

member of the Entrada Sandstone. From Doelling, 2000. 
 ARCH Geologic Resource Evaluation Report 15

Figure 8: Aerial view toward the Fiery Furnace. Notice how the joints in the Entrada Sandstone (Je) terminate against collapsed rock as 

Salt Valley turns to trend east-west and join with Cache Valley. The light biscuit board surface areas are the Moab member of the Curtis 

Formation (Jctm). From Doelling, 2000. 
 NPS Geologic Resources Division 16 

Map Unit Properties 

This section provides a description for and identifies many characteristics of the map 

units that appear on the digital geologic map of Arches National Park. Unit descriptions 

are highly generalized and are provided for informational purposes only. Ground 

disturbing activities should not be permitted or denied on the basis of information 

contained in this section. More detailed unit descriptions can be found in the help files 

that accompany the digital geologic map or by contacting the NPS Geologic Resources 

Division. 

Middle Pennsylvanian to Late Cretaceous- age 

sedimentary rock formations are exposed within Arches 

National Park (figure 9) (Doelling, 1985, 2000). Although 

these rocks cover a time period from 300 to 85 million 

years ago (Ma), they do not represent a period of 

continuous deposition. Rather, the contacts between the 

layers are unconformities that represent large gaps in 

time (figure 10). 

The rock formations represent both marine and 

nonmarine depositional environments. Some of the 

environments represented include warm, shallow seas, 

deep ocean basins, beach and tidal- flat areas, sand 

dunes, and fluvial channel and overbank deposits. The 

formations are identified on figure 9. 

In some places, unconsolidated deposits of sand, silt, 

gravel, and clay overlie the consolidated rock layers. 

Mixtures of these sediments are products of recent 

weathering and erosion processes and are only 

temporary deposits. Wind, water, and gravity have 

generated eolian (wind) and alluvial (river) deposits, 

terrace deposit, and landslides (Doelling, 1985, 2000). 

Paleozoic Era: 

Middle Pennsylvanian Period - 

Paradox Formation 

The Paradox Formation within the Pennsylvanian Period 

(286- 320 Ma) comprises the oldest rocks exposed in 

Arches National Park (figure 2; figure 9; Appendix A). In 

general, the Paradox Formation is made up of a series of 

cyclic deposits containing anhydrite (found in evaporite 

deposits), silty dolomite, black shale, and halite (table 

salt) (Rueger, 1996). Groundwater dissolves salt near the 

surface so that the Paradox Formation exposed in Arches 

consists of a cap rock of contorted gray shale, 

carbonaceous shale, some gypsum beds, and thin 

limestone beds that have remained in place following the 

dissolution of interbedded salts. This cap rock overlies 

thick salt deposits of anhydrite, halite, and other types of 

salt that have not been exposed to intense groundwater 

leaching. 

The Paradox Formation is more than 3,048 m (10,000 ft) 

thick in some areas of the park such as under Salt Valley, 

Cache Valley, and Moab Valley (Doelling, 2000). 

Individual salt beds can be more than 274 m (900 ft) thick 

in areas where the Paradox Formation is very extensive. 

While the Paradox Formation salt underlies large areas 

of Arches, only the cap rock is exposed at the surface. In 

the middle of Salt Valley, west of Devils Garden, cap rock 

crops out along the Klondike Bluffs access road. 

Contorted thin limestone, gray shale, and other insoluble 

rock are well displayed along the sides of the Salt Valley 

Wash. 

Upper Pennsylvanian Period - 

Honaker Trail Formation 

Overlying the Paradox Formation is the Honaker Trail 

Formation (figure 9). The most common rock types in 

the Honaker Trail Formation at ARCH are limestone and 

sandstone (Doelling, 2000). Both limestone and 

sandstone are resistant to weathering and form ledges 

and cliffs in ARCH. The gray, thin to medium bedded 

limestone is cherty, argillaceous (containing clay 

minerals), and fossiliferous. The beds commonly weather 

to hackly surfaces and to nodular shapes. The fossils 

include normal marine invertebrate fauna such as 

brachiopods, horn corals, bryozoa, and crinoids. 

Paleontologists have used trilobites and numerous 

fusulinids to date the uppermost beds in ARCH as latest 

Pennsylvanian in age (Doelling, 2000). 

The white, yellow gray, red, maroon, and lavender 

sandstones are fine to medium grained, mostly well 

sorted, and are found in beds that range from medium to 

massive (homogeneous beds containing no internal 

structures) (Doelling, 2000). The sandstones are 

subarkosic or micaceous, containing high percentages of 

feldspar and mica. Like the limestones, the sandstones 

form resistant ledges and cliffs. Minor beds of shale and 

siltstone are interlayered with the limestones and 

sandstones in the Honaker Trail Formation. 

The thickness of the Honaker Trail Formation varies 

between 0 and 671 m (2,200 ft) in Arches National Park 

(Doelling, 2000). In areas where the underlying Paradox 

Formation is very thick, the Honaker Trail Formation is 

thin or missing. On the other hand, where the Paradox 

Formation is thin, perhaps due to the dissolution or 

non- deposition of salt, the Honaker Trail Formation is 

exceptionally thick. The Honaker Trail Formation is 

only exposed near the Visitor’s Center in Arches 

(Doelling, 1985, 2000). Southwest of the Visitor’s Center, 

however, more than 182 m (600 ft) of the Honaker Trail 
 ARCH Geologic Resource Evaluation Report 17

Formation is visible on a bench above U.S. Highway 191 

and the railroad (Doelling, 2000). 

Permian Period - 

Cutler Formation 

The contact between the Cutler Formation and the 

Honaker Trail Formation is an unconformity, but the 

contact and the Cutler Formation are buried beneath 

younger formations in the park (figure 9). On the walls of 

Poison Spider Mesa, the mesa directly southwest of the 

Visitor’s Center and Highway 191, the Cutler Formation 

consists primarily of interbedded sandstone and 

conglomerate. 

The red- brown to orange brown sandstone is mostly 

fine- to medium- grained and is classified as a subarkosic 

(95% to 75% quartz) to quartzose (100% to 95% quartz) 

sandstone. The sandstones are moderately well- sorted 

but contain fragments of mica. Sedimentary structures 

include tabular- planar crossbedding and horizontal 

bedding (Doelling, 2000). The subarkose and quartzose 

sandstones are well indurated and generally more 

resistant than the red- purple arkosic sandstones and 

conglomeratic sandstones that are also found in the 

Cutler Formation. 

As the feldspar content increases, the sandstone becomes 

red- purple in color and is an arkosic sandstone, a 

sandstone that contains from 100% to 75% feldspar 

grains and less than 25% quartz grains along with some 

minor (< 10%) rock fragments. As with the subarkosic 

sandstones of the Honaker Trail Formation, the 

subarkose and arkose of the Cutler indicate that the 

sediment was deposited a relatively short distance from 

its source. Because they are deposited near the source 

area and rapidly buried by additional sediment, the 

arkosic rocks have not been severely weathered, the 

grains haven’t been rounded, and the more unstable 

minerals like feldspar have not been removed. Thus, the 

arkosic rocks are poorly sorted and medium- to coarsegrained. Sedimentary structures in the arkosic 

sandstones include trough crossbedding and cut- andfill structures where fluvial channels were cut in the 

underlying sediment and backfilled with arkosic 

sediments. 

The conglomeratic sandstones are also poorly sorted but 

the size of the grains suggests either high energy or 

deposition close to the source or both. The pebbles and 

cobbles, commonly as much as 5 cm (2 in) in diameter, 

are composed of the igneous rock, granite, and gneiss 

eroded from the Uncompahgre Highlands that rose to 

the east of ARCH during the Pennsylvanian and Permian 

Periods (Doelling, 2000). 

In the lower part of the Cutler Formation, the sandstone 

beds are mottled, a nearly white color, and are 

interbedded with a few siltstone and limestone beds. The 

thinly- bedded, slope- forming siltstones are generally 

purple, red, or green. The light gray, bioclastic limestone 

is more resistant than the interbedded siltstone and 

forms ledges of thin to medium thick beds (Doelling, 

2000). Because of the unique nature of the lower Cutler 

relative to the upper Cutler, the limestone, mottled 

sandstone, and siltstone beds were formerly divided into 

a separate geologic unit known as the Rico Formation 

(McKnight, 1940). Now, the informal lower Cutler beds 

are being applied to the Upper Pennsylvanian and Lower 

Permian strata and the Rico Formation name is being 

abandoned (Condon, 1997; Dubiel et al., 1996; Loope et 

al., 1990; Sanderson et al., 1990). 

The Cutler Formation is missing over the thick Paradox 

Formation salt that underlies Salt and Cache valleys in 

the park and Moab Valley south of the park. The 

Honaker Trail Formation is also thin or missing over the 

thick Paradox Formation. The formations may have been 

eroded from the area when the salt began to flow upward 

and the strata bowed into an anticline. The most 

accessible location of exposed Cutler Formation rocks 

lies outside of the park, northwest of the Visitor’s Center 

on Poison Spider Mesa. At the head of Little Valley, on 

the southwest side of U.S. Highway 191, the Cutler is 335 

m (1,100 ft) thick, but it pinches out at the southwest 

margin of Moab Valley, just a little south of the covered 

tailings pond southeast of the Visitor’s Center (Doelling, 

1985, 2000). The Cutler Formation probably ranges in 

thickness from 0 to 457 m (1,500 ft) or more beneath the 

park (Doelling, 2000). 

Mesozoic Era 

Triassic Period - 

Moenkopi Formation 

The chocolate- brown, sedimentary rocks of the 

Moenkopi Formation are separated from the underlying 

red- brown, orange- brown, or red- purple sedimentary 

rocks of the Cutler Formation by a slightly angular 

unconformity (figure 9) (Doelling, 2000). In the area of 

Arches National Park, the Moenkopi Formation can be 

subdivided into three members. In ascending order these 

are: the Tenderfoot member, the Ali Baba member, and 

the Sewemup member (pronounced sew- em- up). A thin 

basal conglomerate containing quartz, feldspar, and 

chert is present at the base of the formation. 

The Tenderfoot member of the Moenkopi Formation 

forms a steep, lower slope and consists of mediumchocolate- brown, silty sandstone interbedded with 

sandy mudstone, fissile (flaky) siltstone, and shale 

(Doelling, 2000). Although relatively continuous across 

Arches National Park, the bedding is thin and indistinct. 

The sandstone and siltstone are micaceous. The thin 

bedded, fine- grained sandstone beds commonly contain 

ripple marks. The thin beds of the lower steep slope 

become progressively thicker upsection and eventually 

form distinct ledges (Doelling, 2000). 

The Ali Baba member forms a ledge- forming unit that 

contains similar sedimentary rocks as the Tenderfoot 

member. The Ali Baba member is distinguished from the 

upper and lower units because of its thicker bedding and 
 NPS Geologic Resources Division 18 

ledge- forming characteristics. The change from the Ali 

Baba ledges to the Sewemup member is abrupt. The 

Sewemup member forms an upper steep slope with thin 

to fissile beds and is a lighter brown rather than the 

medium- chocolate- brown of the underlying members 

(Doelling, 2000). In the Big Bend area along the 

Colorado River just south of Mat Martin Point, the 

Moenkopi has a thin, ledge- forming member known as 

the Pariott member. Red- brown to lavender, fine- to 

medium- grained sandstone is interbedded with 

chocolate- brown, orange- brown, and red siltstone, 

mudstone, and shale. Some of the beds in the overlying 

Chinle Formation resemble those in the Pariott member 

beds. 

Exposures of the Moenkopi Formation are found at the 

Big Bend of the Colorado River and in scattered outcrops 

along the south margin of Salt Valley extending from Salt 

Wash eastward for about four miles. A complete outcrop 

of the formation is present on the cliff wall below Poison 

Spider Mesa. The Moenkopi below Poison Spider Mesa 

is about 104 m (340 ft) thick but thins southeastward until 

it pinches out adjacent to Moab Valley (Doelling, 2000). 

Where Paradox salt accumulated, the Moenkopi, like the 

Cutler Formation, is thin or missing. From drill holes in 

and adjacent to the park, the Moenkopi Formation is 

estimated to be zero to 396 m (1,300 ft) thick in the park 

area. 

Chinle Formation 

About 5 million years is missing between the end of the 

Lower Triassic, Moenkopi Formation and the beginning 

of the Upper Triassic, Chinle Formation (figure 9) 

(Dubiel, 1994; Doelling, 2000). The unconformable 

contact is marked by the change from the steep, lightchocolate- brown slope of the upper Moenkopi to the 

red and commonly ledgy slopes of the Chinle Formation 

(Doelling, 2000). Chinle beds may form a disconformity 

or a more easily recognizable angular unconformity with 

the underlying Moenkopi beds. A thin white or lightpink- gray ledge of sandstone is commonly found at the 

base of the Chinle and is a marker that is easily seen on 

most cliff faces (Doelling, 2000). A varicolored sandstone 

and conglomerate overlie the white ledge and is 

designated the lower Chinle. 

The light- green- gray, orange- pink, and pale- redbrown, interbedded sandstone, conglomerate, siltstone, 

and mudstone that make up the lower Chinle are 

commonly discolored with white, light gray, red, purple, 

yellow, orange, and red brown mottles (Doelling, 2000). 

Thin to massive ledges and cliffs of sandstone are 

separated from one another by narrow steep slopes of 

mudstone and siltstone. The quartz grains in the fine- to 

coarse- grained sandstone and conglomerate are poorly 

sorted and subrounded to round. Chert and feldspar 

grains are present, as well. 

Doelling (2000) recognizes another unconformity 

separating the upper Chinle from the lower Chinle in 

ARCH, but no unconformity is recognized within the 

Chinle of southwest Utah by Dubiel (1994). A lower 

slope- forming unit, a middle ledge- forming unit, and an 

upper slope- forming unit characterize the upper 

member on a local scale (Doelling, 2000). The lower 

slope is formed by gray- red and green- gray interbedded 

siltstone, mudstone, and sandstone. The siltstone and 

mudstone are commonly micaceous and weather into 

rectangular fragments. The medium- grained sandstone 

and brown conglomeratic sandstone form thin, 

discontinuous ledges in the lower slope. Ripple 

laminations and small- scale crossbeds are sedimentary 

structures found within the sandstone. Calcareous, 

conglomeratic sandstones contain intraformational clasts 

(clasts formed from Chinle strata) and form lenses with 

scoured bases (Doelling, 2000). 

In the middle ledge, brown- gray, green gray, and redbrown conglomeratic sandstone and non- conglomeratic 

sandstone are interbedded with red- brown siltstone and 

mudstone. Thick to massive ledges of sandstone are 

separated by thin slopes of siltstone and mudstone in the 

middle unit. Petrified wood is commonly found in the 

conglomeratic sandstone. Some of the ledges in the 

middle ledge- forming unit are not well developed and 

are not discernible east of the Park. 

The upper slope- forming unit in the upper Chinle is 

similar to the lower except for 0.3 to 11 m (3 to 35 ft) of 

light- brown to red- orange, very fine to fine- grained 

sandstones near the top of the unit (Doelling, 2000). The 

thick- bedded sandstones are mostly horizontally 

laminated but faint crossbedding is locally present. 

Interbedded with these sandstones are pale- red to redbrown siltstones and mudstones. 

Exposures of the Chinle Formation are found both 

within the park and on the cliff below Poison Spider 

Mesa southwest of Moab Valley along U.S. Highway 191 

(Doelling, 2000). On the geologic map (Appendix A), the 

Chinle Formation is mapped along the south and 

southwest margins of Salt Valley and in the Colorado 

River canyon below Mat Martin Point and around the 

Big Bend, and extending downstream for a few miles 

(Doelling, 2000). 

The thickness of the entire Chinle is variable. Like the 

Moenkopi, Cutler, and Honaker Trail Formations, the 

Chinle thins in areas where the Paradox Formation 

contains thick salt units and thickens in areas where the 

Paradox Formation lacks salt. In the Arches area, the 

Chinle Formation probably ranges from 61 to 274 m (200 

to 900 ft) in thickness (Doelling, 2000). The lower Chinle 

is 116 m (380 ft) thick opposite Mat Martin Point and the 

upper Chinle is nearly 122 m (400 ft). 

The Upper Triassic was a time of extensive fluvial valley 

systems in Utah (Dubiel, 1994) and it’s the first time 

during the Mesozoic that the continental interior 

experienced abundant volcanic ash deposits 

(Christiansen et al., 1994). 
 ARCH Geologic Resource Evaluation Report 19

Jurassic Period - 

Wingate Sandstone 

An unconformity separates the Chinle Formation from 

the Wingate Sandstone. The Wingate forms a redbrown, vertical, massive cliff stained with desert varnish 

that abruptly overlies the Chinle’s red slope. Desert 

varnish is one of the more common desert coatings and 

forms a lustrous, shiny, and smooth surface coating on 

rock surfaces of all sizes from mere pebbles to massive 

cliffs. 

Except where underlying units have dissolved and 

collapsed the unit, the Wingate Sandstone is one of the 

easiest formations to recognize in the Arches area 

(Doelling, 2000). The massive sandstone is very resistant, 

with very few partings or bedding planes. Because the 

underlying Chinle is less resistant than the Wingate 

sandstone, the supporting material for the Wingate cliff 

is gradually removed by erosion and the Wingate is 

undercut. When this happens, slabs of sandstone 

separate from the main cliff along vertical fractures that 

extend through the formation and fall onto the Chinle 

and Moenkopi slope (Doelling, 2000). Wingate rock- fall 

events occur regularly in ARCH (Doelling 2000). 

The upper surface of the Wingate forms a broad plateau. 

Dry washes and shallow swales on the surface fill with 

water after torrential summer rainstorms. Water flowing 

in the normally dry washes flows over the edge of the 

Wingate cliffs and forms waterfalls on the slopes below. 

Along the flanks of many parts of the salt valleys, the 

Wingate doesn’t form a massive cliff but rather, is 

shattered into a very ledgy and blocky, orange- brown 

cliff (Doelling, 2000). 

The gray- orange to gray- orange- pink and moderateorange- pink to pale- red- brown sandstone of the 

Wingate is mostly composed of quartz grains. In addition 

to quartz, the sandstone also contains some feldspar, 

traces of chert, and accessory minerals. The moderately 

to well- sorted, subangular to rounded quartz grains 

often have surfaces that appeared pitted, or frosted. 

Frosted grains are often the result of grains colliding with 

each other during eolian (wind) transport. The 

sandstone is cemented by calcium carbonate and silica 

that has precipitated between grains and is commonly 

stained with iron oxides. Red, dark- brown and black 

stains of desert varnish commonly cover the reddishbrown weathering exposures. Up close, flat beds and 

high- angle crossbedding can be seen on the cliff surface 

(Doelling, 2000). Fossils are rarely found in the Wingate 

Sandstone. 

Kayenta Formation 

The Kayenta Formation caps the Wingate cliffs. On 

Poison Spider Mesa, the Kayenta forms a bench, and in 

places, local drainages have incised through these 

Kayenta benches to expose the Wingate. About 61 to 91 m 

(200 to 300 ft) of Kayenta crops out in the Arches area 

(Doelling, 2000). The contact between the Wingate and 

overlying Kayenta Formation is placed where the thick 

ledges of the Kayenta Formation overlie the vertical cliff 

of the Wingate. 

Kayenta strata are more red or pale purple and 

lithologically more heterogeneous than Wingate strata . 

Although the unit is primarily reddish, individual lenses 

and beds vary considerably from purple, lavender, red, 

tan, orange, and white depending on the mineral content 

and on what trace minerals are found within the cement. 

Grain size and mineralogy apparently influence the color 

with most of the sandstone lenses being moderate orange 

pink whereas the finer grained siltstone and shale 

deposits are dark red brown to gray red (Doelling, 2000). 

Quartz is the primary constituent in the sandstones, but 

mica and lesser quantities of feldspar and dark minerals 

such as hornblende and augite are commonly present. 

Most Kayenta sandstones are fine to medium grained. 

Sedimentary features suggestive of fluvial depositional 

environments in the Kayenta include channeling, current 

ripple marks, rare slump features and high- angle and 

low- angle crossbedding. Subordinate to the fluvial 

sandstone are interbeds of eolian sandstone, 

intraformational conglomerate, siltstone, and shale 

(Doelling, 2000). 

Navajo Sandstone 

The Kayenta Formation intertongues with the Navajo 

Sandstone so the contact can be difficult to place. Thick 

sandstones near the top of the Kayenta are similar to 

sandstone in the Navajo (Doelling, 2000). The contact is 

more recognizable where light- brown or light- gray 

rocks of the Navajo Sandstone replace the dominantly 

red or lavender rocks of the Kayenta. 

High- angle crossbedding is the trademark of the Navajo 

Sandstone (figure 9). Weathering processes etch out the 

crossbeds that form the basis for the Petrified Dunes area 

of the park. Crossbed sets, generally 5 to 8 m (15 to 25 ft) 

thick, are stacked within the sandstone beds. The 

crossbedding dips up to 35 degrees between set 

boundaries. Above the deep canyons of the Colorado 

River and its tributaries, however, the Navajo is generally 

exposed as a bare rock bench. Some of the hollows on 

this surface have been filled by unconsolidated sand that 

is locally eroded from other Navajo sandstone beds 

(Doelling, 2000). 

For the most part, the orange to light- gray sandstone in 

the Navajo Sandstone is fine- grained, generally wellsorted, and massive. Along the crossbed laminae, 

however, medium to coarse grains of sand accumulate. 

The sandstone is cemented with both calcite and quartz. 

While it appears to be a well- cemented cliff former, the 

sandstone is somewhat friable in hand specimen. Locally, 

gray to pink- gray, thin, hard, lenticular limestones grade 

laterally into calcareous reddish siltstones that eventually 

become boundaries between crossbed sets. Small 

nodules of authigenic (grown in place) jasper (red 
 NPS Geologic Resources Division 20 

quartz) can be found in the limestone. Petrified wood has 

been found in the vicinity of the limestone deposits. Like 

the sandstone lenses, the limestone outcrops commonly 

form a resistant bench. This bench is covered with a dark 

sandy or rubbly soil that developed in situ from the 

Navajo Sandstone. 

The Navajo Sandstone forms the bench on much of the 

area east and northeast of Moab Valley. In the Park, the 

Navajo Sandstone is found between the Great Wall and 

the Big Bend of the Colorado River between Cache 

Valley and the Colorado River. The upper surface of the 

Navajo is a regional unconformity extending throughout 

the Colorado Plateau so that the thickness of the Navajo 

will be variable. The thickness of the Navajo varies in the 

Arches area from 61 to 168 m (200 to 550 ft) (Doelling, 

2000). 

Carmel Formation 

Dewey Bridge Member 

According to Doelling (2000), the contact between the 

Navajo Sandstone and the Dewey Bridge member 

outlines a surface of broad, topographic relief that 

formed on the Navajo Sandstone prior to deposition of 

the Dewey Bridge member. The contact is a regional 

unconformity called the J- 2 regional unconformity 

(figure 9, figure 10) (Pipiringos and O’Sullivan, 1978; 

Blakey, 1994). 

The Dewey Bridge member may be divided into lower 

and upper subunits in the Arches National Park area (not 

divided in Appendix A or figure 9). Medium to thick 

beds of resistant, yellow- gray, planar- bedded, finegrained sandstone characterizes the lower unit. In some 

areas, the unit is banded with pink to red- brown 

sandstones layered between the dominantly yellow- gray 

beds. The lower part of the Dewey Bridge member fills 

low areas in the Navajo Sandstone, and planar or flatbedded sandstones of the Dewey Bridge cover the 

surface of the high- angled crossbedded Navajo. The 

lower Dewey Bridge weathers to the same color as that of 

the Navajo Sandstone. Angular white chert clasts, 

however, are common in the Dewey Bridge member 

immediately above the contact with the Navajo 

(Doelling, 2000). 

The upper unit is a red- brown, muddy- looking, mostly 

fine- grained, silty sandstone that forms a slope or a redbrown to chocolate- brown recess between the lower 

unit and the overlying, cliff- forming Slick Rock member 

of the Entrada Sandstone (Doelling, 2000). This upper 

unit contains irregular, contorted bedding. 

The Dewey Bridge member, overall, thins to the east and 

is anywhere from 21 to 61 m (70 to 200 ft) thick. In the 

Arches area, the thickness of the lower unit varies from 5 

to 26 m (15 to 85 ft) and the upper unit varies from 18 to 

48 m (60 to 157 ft). At the Garden of Eden, the member is 

about 27 m (90 ft) thick. In the northwest corner of the 

park, at Klondike Bluffs, the member is 42 m (139 ft) thick 

and near the Visitor’s Center, about 32 m (104 ft) of 

Dewey Bridge is exposed. Where the Navajo Sandstone 

is thick, the Dewey Bridge member is thin (Doelling, 

2000). 

Exposures of the Dewey Bridge member can be seen 

along the park highway to Courthouse Towers, along the 

base of The Great Wall, and northward from the Fiery 

Furnace (Doelling, 2000). The Dewey Bridge member 

helps form some of the more unusual scenery in the Park 

including the pedestal of Balanced Rock and the base of 

The Windows arches. 

Slick Rock Member 

The Slick Rock member of the Entrada Sandstone is a 

massive, well- indurated, red- orange or brown, color 

banded, sandstone. The sandstone is primarily very fine 

to fine- grained but contains sparse and scattered 

medium to coarse sand grains. Calcite and iron oxide 

cement hold the sand grains together. Commonly, the 

Slick Rock weathers to form smooth cliffs and bare- rock 

slopes. The sandstone is both planar bedded and crossstratified (crossbedded) with small holes commonly 

aligned along crossbed laminae. The Slick Rock member 

intertongues with the Dewey Bridge in some areas while 

in others, the contact is sharp (Doelling, 2000). 

The Slick Rock member of the Entrada Sandstone is 

perhaps the most impressive geologic unit in Arches 

National Park. Most of the arches in the park are found 

along the lower and upper contacts of the Slick Rock and 

along the indentures in the middle of the unit (figure 7). 

The vertical cliffs of The Courthouse Towers and The 

Great Wall are Slick Rock sandstone above the redbrown or chocolate- brown marker beds of the Dewey 

Bridge member. The fins of the Fiery Furnace and the 

area northeast of Salt Valley where it is cut by numerous 

closely spaced joints are carved out of Slick Rock 

sandstone (figure 2). Large irregular fields of selfderived wind- blown sand cover or partly cover the Slick 

Rock where it is not exposed as a cliff, fin, or arch 

(Doelling, 1985, 2000). Where exposed in the park, the 

Slick Rock member is normally 61 to 107 m (200 to 350 ft) 

thick (Doelling, 2000). 

Curtis Formation 

Moab Member 

The resistant sandstone of the Moab member forms an 

obvious cap on many of the Entrada Sandstone cliffs. 

The massive, cliff- forming sandstone is mostly a paleorange, gray- orange, pale- yellow- brown, or light- gray 

on a fresh surface but weathers white or light gray. 

Calcium carbonate cements the fine to medium quartz 

grains and forms well- indurated sandstone. Low angle 

cross- stratification and many joints are seen in outcrop 

(Doelling, 2000). 
 ARCH Geologic Resource Evaluation Report 21

About 18 to 36 m (60 to 120 ft) of the Moab member is 

exposed in the park (Doelling, 2000). The Moab member 

crops out on the hike to Delicate Arch and culminates in 

the upper part of the Arch, supported on pedestals of the 

Slick Rock member of the Entrada Sandstone. Bare- rock 

outcrops of the Moab member form sloping, jointed 

benches on each side of Salt Valley. 

Summerville Formation and Morrison Formation 

(Tidwell Member) Undifferentiated 

Because the Middle Jurassic Summerville Formation is 

generally less than 3 m (10 ft) thick in the park, it has been 

mapped as one unit with the Tidwell member of the 

Upper Jurassic Morrison Formation on the geologic map 

(Appendix A) (Doelling, 1985, 2000). This thin, redbed 

marker unit overlying the Moab member of the Curtis 

Formation was interpreted as Summerville Formation by 

Dane (1935) and McKnight (1940) who correlated it with 

reddish beds of sandstone and siltstone present in the 

San Rafael Swell to the west (figure 10). Later work 

revealed that the redbed unit actually contained two rock 

packages that were separated by the J- 5 regional 

unconformity (figure 9, figure 10) (Pipiringos and 

O’Sullivan, 1978; O’Sullivan, 1980, 1981; Peterson, 1994). 

The lower part of this thin redbed marker unit correlates 

with the Summerville Formation while the upper and 

dominant part of the marker in the Arches area is the 

Tidwell member of the Morrison Formation (Doelling, 

2000). Although mapped as one unit, the Summerville 

and Tidwell are easily divisible by field geologists who 

have worked with the two units. 

The Summerville Formation consists of non- calcareous, 

light- tan to brown sandstone and red sandy siltstone. 

The sandstone forms thin- to medium- bedded ledges, 

and the siltstone forms steep slopes (Doelling, 2000). 

The base of the Summerville is marked by a zone of 

yellow- gray sandstone that contains dinosaur footprints 

(Lockley, 1991). The top of the formation is identified by 

a prominent thin- to medium- bedded, blocky to thin or 

platy, ripple- marked sandstone ledge (Doelling, 2000). 

The contact between the Summerville Formation and the 

Tidwell member of the Morrison Formation is placed at 

the base of thin gray limestone beds or maroon to 

lavender, calcareous siltstone of the Tidwell member. 

For the most part, the Tidwell consists or red, maroon, 

lavender, or light- gray weathering siltstone, but 

discontinuous beds of light- gray limestone are 

interspersed throughout the siltstone. The limestone 

beds are more common at the base and top of the unit. 

White chert concretions (localized nodules that are 

harder than the enclosing rock), some as much as 1.8 m 

(5.4 ft) in diameter, may be found immediately above the 

lowermost limestone bed of the Tidwell member in 

Arches (Doelling, 2000). The origin of these concretions 

is still puzzling. 

Only about 2 to 6 m (6 to 20 ft) of Summerville 

Formation is exposed in the park. The Summerville thins 

southward, but it thickens in all other directions. From 

7.5- 15 m (25 to 50 ft) of Tidwell is exposed far down on 

each side of the Salt Valley salt anticline, near the axis of 

the Moab anticline, and in down- faulted blocks on the 

north side of Cache Valley on both sides of Salt Wash 

(Doelling, 1985, 2000). 

Morrison Formation 

Salt Wash Member 

The gradational contact between the Tidwell member 

and the overlying Salt Wash member is generally placed 

below the first significantly thick, light- gray, yellowgray, or light- brown sandstone lens or bed of the Salt 

Wash member. Six or seven thick, vertically stacked, 

sandstone lenses make up about 25% to 40% of the Salt 

Wash member and alternate with 60% to 75% red, 

green- gray, maroon, and lavender muddy siltstone. 

Locally, the Salt Wash member also contains limestone 

beds and nodules in the muddy siltstones (Doelling, 

2000). The sandstone lenses form ledges that range from 

0.6 to 6.1 m (2 to 20 ft) thick although most are 0.6 to 1.2 

m (2 to 4 ft) thick (Doelling, 2000). The fine- to coarsegrained, moderately to poorly sorted quartz sandstone is 

crossbedded and calcareous. Fragments of petrified 

wood and dinosaur bones have been found in the Salt 

Wash member. Large pieces of sandstone litter the base 

of the outcrop. As the softer siltstones between the lenses 

of sandstone erode , the more resistant sandstone 

becomes unstable and unsupported and eventually falls 

onto the slopes of siltstones. 

The Salt Wash member is exposed along the western and 

northeastern boundaries of the Park, in Cache Valley, 

and in eastern Salt Valley. In Cache and Salt valleys, 

outcrops of Salt Wash are exposed in fault slices 

(Doelling, 1985, 2000). Total thickness of the Salt Wash 

member ranges from 40 to 91 m (130 to 300 ft) thick in the 

park, and averages about 55 m (180 ft) (Doelling, 2000). 

Brushy Basin Member 

Dark- colored conglomeratic sandstone lenses, brightly 

colored- banded mudstone, or bright- green mudstone 

overlie the light- gray sandstone lenses of the Salt Wash 

member of the Morrison (figure 9). The upper contact of 

the Salt Wash member is placed at the top of the interval 

dominated by the sandstone lenses. The Brushy Basin 

member is a premier Upper Jurassic volcanic ashbearing unit and consists largely of bentonitic mudstones 

(Christiansen et al., 1994). Whereas the Salt Wash 

sandstones are mostly quartzose, the Brushy Basin 

sandstone or conglomeratic sandstone lenses are lithic, 

that is, they are composed of fragments of other rocks. 

Sandstone is more common in Brushy Basin mudstone 

than in Salt Wash mudstone. 

The Brushy Basin forms smooth, variegated or green 

slopes with few ledges. The bentonite clay in the Brushy 
 NPS Geologic Resources Division 22 

Basin member adds to its landslide and slump potential 

because bentonite is a type of clay whose crystalline 

structure expands when wet and shrinks upon drying. 

Constant expanding and contracting weaken the unit 

and cause overlying strata to move downslope. The silty 

and clayey mudstone and muddy sandstone are 

interbedded with a few thin units of local conglomeratic 

sandstone lenses. Bands of various shades of maroon, 

green, gray, and lavender color the steep- sloped, 

indistinctly bedded outcrops. The slopes are a bright 

green to the southeast. The shrinking and swelling of the 

bentonitic clay causes the surface of the Brushy Basin 

member to weather to a popcorn- like texture. Locally, 

dinosaur bone and petrified wood are found in the 

member (Doelling, 2000). 

Seventy- five percent of the member is mudstone. The 

other 25% of the member is crossbedded, coarsegrained sandstone. Locally, conglomerate lenses are 

present with clasts the size of pebbles. Overall, the unit 

decreases in sandstone upsection with both the 

sandstone and conglomerate lenses generally found near 

the base of the Brushy Basin (Doelling, 2000). 

Approximately 91 to 137 m (300 to 450 ft) of Brushy Basin 

has been measured in the park (Doelling, 2000). 

Cretaceous Period - 

Cedar Mountain Formation and Dakota Sandstone 

Approximately 30 million years is missing between the 

last bed of the Morrison Formation and the first bed of 

the Lower Cretaceous, Cedar Mountain Formation 

(figure 9). The unconformity is placed at the base of a 

persistent cliff- forming sandstone about 3 to 9 m (10 to 

30 ft) thick above the top of the brightly banded or green 

slope of the Brushy Basin member of the Morrison 

Formation. Although separated by a large gap in time, the 

Cedar Mountain Formation weathers like the Brushy 

Basin member and is composed of silty and clayey 

mudstone with sandstone lenses much like the Brushy 

Basin member (figure 9). The slope of the Cedar 

Mountain, however, has a more pastel or dull coloration 

(Doelling, 2000). 

The light to dark brown sandstone of the lower Cedar 

Mountain Formation is fine- grained, medium- grained, 

coarse- grained and conglomeratic. The well- indurated 

sandstone intervals form ledges much like the one at the 

base of the formation. Many of the sandstones are so 

strongly cemented by silica that the rock breaks across 

the sand grains rather than around them (Doelling, 

2000). Quartzite (metamorphosed sandstone) fractures 

in the same manner, but the sandstone in the Cedar 

Mountain Formation has not been metamorphosed. 

Silty mudstone is interbedded with the sandstone. In 

general, the clay content in the Cedar Mountain is less 

than in the Brushy Basin member of the Morrison. 

Nodular gray or brown limestone is interbedded with the 

mudstone and sandstone. Chert nodules can be found in 

the limestone (Doelling, 2000). Scattered fossils such as 

ostracodes (small bivalved crustaceans), protistids (onecelled organisms), and snails have been found in the 

Cedar Mountain Formation. White petrified wood, 

locally abundant in the lower cliff former, and dinosaur 

bones have also been found in this unit (Kirkland et al, 

1999; Doelling, 2000). Abundant chalcedony (quartz with 

crystals too small to be seen under a light microscope) 

fragments weather out of the formation in local areas. 

In ARCH, exposures of the Cedar Mountain Formation 

are mostly confined to the tilted fault blocks in Cache 

and Salt Valleys, especially around the Wolfe Ranch 

house where Salt Wash crosses Cache Valley (Doelling, 

1985, 2000). More extensive Cedar Mountain outcrops 

are found west and north of the park boundaries 

(Doelling, 1985, 2000). 

The unconformable contact between the Lower 

Cretaceous Cedar Mountain Formation and the Upper 

Cretaceous Dakota Sandstone is placed at the base of a 

white claystone or a yellow- gray to brown sandstone, 

conglomeratic sandstone, and conglomerate of the 

Dakota Sandstone (Doelling, 2000). In eastern Colorado, 

the Dakota Sandstone is Early Cretaceous, but the 

formation doesn’t appear in western Colorado and Utah 

until the Late Cretaceous time. 

The Dakota Sandstone is a heterogeneous mixture of 

claystone, limestone, thin coal seams, shale, 

conglomeratic sandstone, and yellow- gray sandstone 

(Doelling, 2000). The unit becomes discontinuous and is 

locally missing in areas west of the park. The yellow- gray 

conglomeratic sandstone lithology is the most obvious 

Dakota unit in the Arches area. 

Most stratigraphic sections of Cedar Mountain 

Formation are only 30 to 46 m (100 to 150 ft) thick 

although the formation is 30.5 to 76 m (100 to 250 ft) 

thick in the park area (Doelling, 2000). In the park, the 

Dakota is only exposed in Salt and Cache Valley 

outcrops that are typically 6 to 24 m (20 to 80 ft) thick. A 

steeply dipping orange or brown Dakota hogback crops 

out immediately north of the highway leading to Wolfe 

Ranch and the parking area to the Delicate Arch 

overlook. 

Mancos Shale 

The youngest bedrock unit in Arches National Park is 

the slope forming, Upper Cretaceous Mancos Shale that 

is confined to Cache and Salt Valleys in Arches National 

Park (figure 9). Mancos strata is folded and perhaps 

attenuated by faulting. The transition from Dakota 

Sandstone to Mancos shale is gradational over a narrow 

interval. 

The Mancos at Arches has been subdivided into three 

units: the lower Tununk member, the Ferron Sandstone 

member, and the Blue Gate member. Mostly mediumgray, calcareous, fissile shale from the Tununk and Blue 

Gate members form the soft slopes of Mancos Shale. The 

Tununk shales crop out as the lower part of the Mancos 

in Cache and Salt Valleys. The darker brown- gray 
 ARCH Geologic Resource Evaluation Report 23

Ferron sandstone is more resistant than the surrounding 

shale. Erosion has exposed the Ferron as low ridges and 

rounded hills in Cache Valley. Most of the sandstone is 

platy or thin- bedded and very fine- grained (0.0625-

0.125 mm). The middle of the Ferron Sandstone member 

consists of dark- gray and black carbonaceous shale 

(Doelling, 2000). Rocks in the Blue Gate member are also 

primarily shale. The Blue Gate overlies the Ferron 

Sandstone, and the shale may be slightly lighter in color 

than the Tununk. 

The thickness of the members of the Mancos ranges 

from 30.5 to 122 m (100 to 400 ft) for the Tununk, 27 to 37 

m (90 to 120 ft) for the thinner Ferron Sandstone 

member, and about 152 m (500 ft) for the relatively 

complete Blue Gate member (Doelling, 2000). The 

Mancos is fossiliferous with zones of marine pelecypods 

found immediately above the Dakota Sandstone and at 

the top of the Ferron member (Doelling, 2000). 

Cenozoic Era: 

Quaternary Period - 

Modern Alluvium 

Erosion has removed the Tertiary Period deposits from 

the Arches National Park area. Sedimentation during the 

Quaternary Period (1.6 million years to present) has 

resulted in thin, discontinuous, unconsolidated deposits 

of sand, stream gravels, and silt that cover the older rocks 

(Doelling, 1985). 

Alluvial deposits found along the Colorado River contain 

cobbles of igneous rocks from the La Sal Mountains and 

gneiss from the Uncompahgre Plateau to the east. Qa1 

represents alluvium consisting of clay, silt, sand and 

gravel that has been deposited along the more important 

active rivers, streams, and washes (Doelling, 1985). 

Interbedded volcanic ashes in Qa2 date these deposits at 

620,000 and 740,000 years before present. 

Most deposits are Holocene and most are less than 7.6 m 

(25 ft) thick. The alluvium in the north part of Moab 

Valley, however, is very thick and its lower parts may be 

Pleistocene in age (Doelling, 2000). 

Cenozoic Era: Quaternary Period - Gravel Deposits, 

the larger, mappable areas of gravel deposits are of 

mostly alluvial origin (Qag), but terrace gravel deposits 

(Qat) on abandoned floodplains rise 24 m or more (80+ 

ft) above modern stream and dry wash channels. The 

alluvial deposits consist of the same materials as found in 

the modern channels. Gold is found on the terraces 

along the Colorado River but the small flakes and floursized particles are too fine and too sparse to be mined 

profitably (Doelling, 2000). Terraces in the middle of Salt 

Valley were laid down in an ancient stream that no 

longer flows in the valley. On these terraces are cobbles 

eroded from the Book Cliffs many miles to the north. 

The terrace alluvial deposits in Salt Valley are generally 

less than 4.6 m (15 ft) thick. 

Sand Deposits 

The unconsolidated sand deposits (Qeas) are mostly of 

eolian (wind) origin but are interbedded or mixed with 

various amounts of alluvial, eluvial, and colluvial sand 

(Doelling, 1985). Eluvial sand forms as the rock 

disintegrates in place while colluvium consists of a 

combination of alluvial sediments and angular fragments 

of the original rocks. 

Hollows on sandstone strata, especially on the Slick 

Rock member of the Entrada Sandstone, are filled with 

wind- blown sand (Qes). Eolian sand is also trapped in 

protected places as the sand is blown across the area by 

the prevailing wind. Dunes form in some areas and in Salt 

Valley, long fingers of eolian sand cover mixed eolian 

and alluvial (Qea) deposits (Doelling, 2000). 

The complex unconsolidated deposits of mixed eolian 

and alluvial sources form lenses of basin- fill alluvium, 

channel deposits, overbank deposits, and wind- blown 

sand sheets that are mapped in Doelling (2000), but are 

not differentiated in Doelling (1985) or Appendix A. 

Sand, silt, gravel, and clay make up most of the deposits. 

Well- developed caliche horizons have developed on 

some of the relatively old (Pleistocene?) deposits. Mostly 

less than 7.6 m (25 ft) thick, these mixed deposits are 

several hundred feet thick in Salt Valley because salt was 

being dissolved when the sediment accumulated. 

Interlayered with the unconsolidated deposits in Salt 

Valley is gypsum that was derived from the local 

outcrops of the Pennsylvanian Paradox Formation 

caprock as well as volcanic ash drifting into the area from 

the west during the Pleistocene. 

The age of these mixed deposits can be determined by 

radiometric age- dating of the volcanic ash (Doelling, 

2000). Two of the ash layers, the Bishop ash and Lava 

Creek B ash, have well- known ages. The Bishop ash was 

deposited 730,000 years ago and the Lava Creek B ash 

was deposited 610,000 years ago from volcanoes in 

California and from the current location of Yellowstone 

National Park (Coleman, et al., 1988). As salt beds 

beneath these deposits dissolved and the overlying strata 

collapsed, some of the thicker deposits were folded into 

synclines and anticlines.
 NPS Geologic Resources Division 24 

Landslide Deposits 

Periodically, blocks and slumps of bedrock detach from 

the outcrop and slide downslope, sometimes for a 

considerable distance (Doelling, 1985). These landslides 

are composed of mostly larger coherent to partly broken 

up masses of consolidated units. Water in this desert 

landscape plays an important role in generating 

landslides. In cycles of wet weather, fine- grained clayey 

bedrock outcrops collapse. The bentonite- bearing 

Morrison Formation, especially the Brushy Basin 

member, produces most landslides as the bentonite 

shrinks and swells with the addition and subsequent 

evaporation of water. Visitors to the Elephant Butte folds 

can see numerous small old landslides and slumps. What 

they can’t see is the source of these slides. The closest 

bedrock containing the slide materials is now several 

miles away (Doelling, 2000). 

Talus Deposits 

A landslide is a general term applied to any mass 

movement down a slope by rock and/or soil material. 

One form of a landslide is a rockfall in which blocks of 

rock break from a cliff and fall vertically to collect in a 

jumbled pile of rocks called talus. The talus deposits at 

ARCH are a collection of rockfall blocks, boulders, and 

smaller angular fragments lying on slopes immediately 

below the parent outcrop. In Appendix A, and in the 

digital geologic map included with this report, the talus 

deposits are mapped only where they completely cover 

the underlying units. 
 ARCH Geologic Resource Evaluation Report 25

Figure 9: Stratigraphic column for Arches National Park including the location of regional unconformities (thick red lines) and some of 

the principal sedimentary structures found in the formations. See figure 9b for a legend of rock types and sedimentary features. 
 NPS Geologic Resources Division 26 

Legend to accompany the stratigraphic column shown in figure 9. 
 ARCH Geologic Resource Evaluation Report 27

Figure 10: Correlation chart of Jurassic Period strata and unconformities in eastern Utah. Vertical lines represent times of erosion or 

non-deposition. Stratigraphy for Arches National Park is from Doelling (2000). Stratigraphic relationships in the San Rafael Swell and 

Southeast Utah are modified from Peterson, 1994. 
 NPS Geologic Resources Division 28 

Geologic History 

This section highlights the map units (i.e., rocks and unconsolidated deposits) that occur 

in Arches National Park and puts them in a geologic context in terms of the environment 

in which they were deposited and the timing of geologic events that created the present 

landscape. 

Depositional and Tectonic History 

Pennsylvanian through Cretaceous Period rocks are 

exposed in Arches National Park and represent marine, 

nearshore, and continental depositional environments. 

As the Paleozoic Era came to a close, the ancestral Rocky 

Mountains were forming and the two great landmasses, 

Laurasia and Gondwana were becoming sutured 

together in one great continent called Pangaea (figure 11). 

Gondwana included Australia, Antarctica, Africa, South 

America, and India south of the Ganges River, plus 

smaller islands. Laurasia, located in the northern 

hemisphere, is the hypothetical continent that contained 

the present northern continents. 

The most extensive mass extinction of all recorded 

geologic history occurred at the end of the Permian 

Period. In the Mesozoic Era, Pangaea began to split apart 

to form the lithospheric plates that we see today sliding 

around the globe. This section summarizes the geologic 

history represented by the rocks exposed within the 

borders of ARCH. 

Paleozoic Era 

Middle Pennsylvanian Period – Paradox Formation 

At this time, the continental margin of North America lay 

far to the west and southeast of the Colorado/Utah state 

line (De Voto, 1980). As Gondwana and Laurasia 

collided, the compression caused a northwest- southeast 

trending, shallow, subsiding trough called the Paradox 

Basin to form across the Four- Corners area (Stone, 

1986). Periodic marine incursions from the south, 

impacted by both global tectonics and Gondwana 

glaciation, flooded the Paradox Basin. 

A global climate shift from the warm humid environment 

of the Late Mississippian created a much more arid 

environment in the region of Utah during the Early 

Pennsylvanian (Rueger, 1996). During the Pennsylvanian, 

the Paradox Basin was located at 10o North paleolatitude 

(Wray, 1983). Rapid evaporation accompanied the warm 

climate so that the salt in the seawater became 

concentrated. The Middle Pennsylvanian Paradox 

Formation contains 29 evaporite cycles consisting of 

vertical sequences of organic- rich black shale, dolomite, 

anhydrite, sodium and potassium salts, anhydrite, 

dolomite and black shale (Hite, 1961; De Voto, 1980; 

Rueger, 1996). 

With burial and the weight of accumulating sediments, 

the salt flowed to areas of less confining pressure in 

much the same way as toothpaste is squeezed from a 

tube. These areas of less confining pressure paralleled 

zones created by displacements along northwesttrending faults. The salt migrated and thickened along 

these zones while, at the same time, the salt thinned in 

adjacent areas. Rock strata arched over thickened salt 

zones to form aerially extensive anticlines. These 

anticlines trapped oil that migrated from black shale into 

porous limestones. Near Dead Horse Point, the salt 

deposits are also mined for potash salts used as fertilizer 

(Doelling, 1985, 2000). 

Original salt thickness is believed to be about 1,500 m 

(5,000 ft) (Doelling, 1985). In the salt anticlines, the 

maximum known thickness is nearly 4,300 m (14,000 ft), 

and under Salt Valley in Arches National Park, the salt is 

at least 3,000 m (10,000 ft) thick (Doelling, 1985). 

Upper Pennsylvanian Period – Honaker Trail Formation 

By Late Pennsylvanian time, the Paradox Basin became 

more stable and filled with sediment. The region was 

connected to the open sea to the west and circulation 

prohibited salt deposition. Rather, limestone and 

dolomite were deposited in the open marine 

environment. 

Clastic sediments were shed from the Uncompahgre 

Mountains, part of the ancestral Rocky Mountains that 

were rising east of the park along the Uncompahgre fault, 

a major thrust fault (Doelling, 2000). Large quantities of 

gravel, arkosic sand (sand rich in feldspar), and silt 

eroded from the eastern highlands and were transported 

by streams into the sea in which the Honaker Trail 

limestones were being deposited. The carbonate/clastic 

sequence constitutes the Honaker Trail Formation. 

Permian Period – Cutler Formation 

The coarse arkosic marginal- marine and continental 

clastic sediments of the Cutler Formation represent a 

complex eolian- fluvial- alluvial fan association of 

sediments shed from the rising Uncompahgre Mountains 

(Campbell, 1980; Cole et al, 1996). Near the park, the 

Cutler Formation rests unconformably on the Honaker 

Trail Formation, but regionally, the lower Cutler clastic 

beds represent a transitional change between the Upper 

Pennsylvanian and Lower Permian formations 

(Campbell, 1980; Dubiel et al., 1996). 

While the Uncompahgre Mountains were being whittled 

away by erosion, buoyant salt of the Paradox Formation 

was rising beneath the alluvial fans. The topography 
 ARCH Geologic Resource Evaluation Report 29

changed from one of flat lowland to one of undulating 

hills around which streams diverted the sediments. As a 

result of the rising salt domes, the Cutler arkoses were 

only thinly deposited on top of the hills, if at all, and 

formed thick, complex channel deposits around the hills 

(Baars, 2000). 

Upper Permian rocks are missing from the Arches 

National Park area, but from other areas around the 

globe, geologists have documented the third, and most 

severe, major mass extinction of geologic time at the 

close of the Permian (figure 17). Geologists think a comet, 

about 6- 13 km (4 to 8 mi) in diameter, collided with the 

Earth (Becker et. al., 2001). The heat and shock waves 

generated from such an impact may have triggered vast 

volcanic eruptions that spread lava over an area twothirds the size of the United States. Imagine, for example, 

basalt flows covering the area from San Francisco to St. 

Louis and Seattle to New Orleans. 

Powerful wind updrafts would have carried dust and grit 

swirling into the upper atmosphere. The particulate 

matter would have reflected back into space and 

scattered sunlight, resulting in years of global cooling 

with freezing temperatures even during summertime. A 

recent example of this type of global cooling occurred in 

1816, “the year without a summer,” following a volcanic 

explosion in Tambora, Indonesia. The sulfuric emissions 

from the volcanoes would have mixed with atmospheric 

water to produce downpours of corrosive acid rain. 

Thousands of species of insects, reptiles, and amphibians 

perished on land. In the oceans, coral formations 

vanished, as did snails, urchins, sea lilies, some fish, and 

the once- prolific trilobites. Five million years later, at the 

dawn of the Mesozoic Era, the oceans began to evolve 

into the chemistry of the modern oceans and on land, a 

new order arose, one that the world had never seen 

before and will never see again. 

Mesozoic Era 

Lower Triassic Period – Moenkopi Formation 

Following the Permian, the Triassic Period (245- 206 Ma) 

opened onto a desolate scene. The atmosphere and the 

oceans were slowly recovering from the catastrophic 

extinction event. Shallow, marine water stretched from 

Utah to eastern Nevada over a beveled continental shelf. 

In the Early Triassic, volcanic activity decreased on the 

western margin of the supercontinent (Christiansen et 

al., 1994). The sea transgressed, or overlapped, onto the 

continent from the northwest, pushing the shoreline into 

western Wyoming and northwestern Utah (figure 12). 

The sea then regressed off the continent and red beds 

were deposited. Red beds are interpreted to represent 

terrestrial, or continental, deposition because when 

exposed to air, the trace amounts of iron in the sediment 

oxidize to the characteristic rust color seen in the 

Triassic exposures across the southwest. Abundant 

rainfall on the Uncompahgre Highlands led to increased 

weathering and rapid erosion especially if vegetation had 

been reduced significantly by acid rain resulting from 

earlier volcanic activity and extraterrestrial impact. 

The coarse- grained arkoses along the Colorado River 

and Big Bend attest to the continued erosion of the 

Uncompahgre as the red beds of the Lower Triassic, 

Moenkopi Formation were deposited in fluvial, mudflat, 

sabkha, and shallow marine environments (Christiansen 

et al., 1994; Doelling, 1985, 2000). Ripple marks and lowangle crossbeds in the Moenkopi rocks are the result of 

river processes that beveled the area into a relatively flat 

plain by eroding the higher areas and infilling the 

depressions with sediment. Gypsum in the lower part of 

the formation was a product of cyclic arid conditions 

(Huntoon et al., 2000), but the fossilized plants (reeds 

and Equiseta), trackways of reptiles and amphibians, and 

fossils of warm seawater invertebrates in the strata above 

the gypsum are evidence of a climate shift to a warm 

tropical setting (Stewart et al., 1972A; Huntoon et al, 

2000). 

Middle Triassic Period 

The Middle Triassic Period (235- 240 Ma) is a mystery in 

Utah. No rocks that span this time range from 235- 400 

Ma have been preserved in Utah. To the west, explosive 

volcanoes arose from the sea in the Middle Triassic and 

formed a north- south trending arc of islands along the 

border of what is now California and Nevada 

(Christiansen et al., 1994; Dubiel, 1994; Lawton, 1994). 

Eruptions from these stratovolcanoes were similar to the 

eruptions from Mt. Vesuvius that destroyed Pompeii in 

A.D. 79, only more violent (Christiansen et al., 1994). 

Upper Triassic Period - Chinle Formation 

Continental, Chinle Formation rocks of the Western 

Interior of North America form a complex assemblage 

of alluvial (river deposits), marsh, lacustrine (lake), playa 

(dried lake), and eolian (wind) deposits (Stewart et al., 

1972B). Sedimentologic characteristics of the Chinle 

suggest that the sediments were deposited in a densely 

vegetated flood plain or mud flat that contained localized 

shallow ponds and small, shallow, sinuous streams (Scott 

et al., 2001). Mottling in the lower Chinle represents 

gleyed (bluish gray soil horizon) paleosols (ancient soils) 

formed by fluctuating water tables (Dubiel, 1994; 

Doelling, 2000; Scott et al., 2001). Vertical tubular 

features in the rocks are probably the remains of 

fossilized root systems (Doelling, 2000). Siltstone and 

mudstones are the consolidated result of overbank or 

floodplain deposits. The sandstones and conglomerates 

represent old stream channels. The Chinle environment 

was similar to today’s subtropical to tropical areas of 

South America and Africa. 

Throughout the region, layers of bentonite, 

montmorillinite clay, formed from the alteration of 

volcanic ash. The bentonite layers indicate a period of 

renewed volcanism to the west (Christiansen et al., 1994). 

Paleovalleys cut into the Moenkopi Formation (Dubiel, 

1994). In the Arches region, the Moab paleovalley was a 
 NPS Geologic Resources Division 30 

major tributary to a northwest- trending paleovalley into 

which many drainage networks emptied. (figure 13). 

Choked with sediment, braided streams, rather than 

meandering streams, tended to occupy these paleovalley 

systems. 

During the final phases of Chinle deposition, lower water 

table conditions existed. Lacustrine mudflat siltstones 

and mudstones, ephemeral fluvial- channel sandstones, 

and eolian sand- sheet and dune deposits were deposited 

during extended dry periods (Dubiel, 1994). 

Granitic plutons in southern California, central Nevada, 

on the border of Idaho and Oregon, and in central 

Washington, along with volcanic rocks of this age, are 

remnants of a magmatic arc that developed above an 

east- dipping subduction zone in the Mesozoic. As 

highlands rose above sea level to the west and the 

continental crust was deformed, rivers that once flowed 

northwesterly now reversed their direction and flowed 

to the south and west. Lakes formed at the base of the 

rising highlands (Dubiel, 1994). 

Jurassic Period – Overview 

Southeastern Utah during the Jurassic was a time of 

extensive eolian sand seas, called ergs. The region was 

located about 18o north latitude at the beginning of the 

Jurassic and about 30- 35o north latitude at the end of the 

Jurassic (Kocurek and Dott, 1983; Peterson, 1994). This is 

the latitude of today’s trade wind belt where hot, dry air 

descends from the upper atmosphere and sweeps back to 

the equator in a southwesterly direction, picking up any 

moisture as it goes. This is the latitude, thus, of intense 

evaporation. Most modern hot deserts of the world 

occur within the trade wind belt and during the Jurassic, 

the climate of the Colorado Plateau appears similar to the 

modern Western Sahara. 

In the Sahara, the world’s largest desert, only 10% of the 

surface is sand- covered. The Arabian Desert, Earth’s 

sandiest desert, is only 30% sand- covered. The Jurassic 

deserts that stormed across the Colorado Plateau for 

roughly 40 million years (not counting the time 

represented by erosion) contained sand dunes that may 

be the largest recorded in the rock record (Kocurek and 

Dott, 1983). These ergs formed on a coastal and inland 

dune field affecting southern Montana, eastern Utah, 

westernmost Colorado, southwest Colorado, 

northeastern Arizona, and northwestern New Mexico 

(Kocurek and Dott, 1983; Peterson, 1994). The volume of 

sand in these systems was enormous. Where did it come 

from? Winds in these northern latitudes blow to the 

west, yet the sand dunes of the Jurassic migrated to the 

south. Why? Answers to these questions lie with the plate 

tectonic setting, the climate, and the potential sediment 

sources. 

To the south, the landmass that would become South 

America was splitting away from the Texas coast just as 

Africa and Great Britain were rifting away from the 

present east coast and opening up the Atlantic Ocean. 

The Ouachita Mountains, formed when South America 

collided with North America, remained a significant 

highland and rivers from the highland flowed to the 

northwest, towards the Plateau. The Uncompahgre 

Highlands in the west remained high in the Jurassic and 

also contributed sediment to the Arches area. 

Lower Jurassic Period – 

Wingate, Kayenta, Navajo formations 

The regional depositional geometry of the Wingate, the 

high- angle crossbedding, well- sorted quartz grains, and 

frosted grains identify the Wingate Sandstone as an 

eolian deposit (Peterson, 1994; Doelling, 2000). 

Regionally, six major erg sequences have been mapped in 

the Wingate (Nation, 1990; Blakey, 1994). The six erg 

units vary in detail from one another, but in general, both 

the overall Wingate succession and the individual erg 

sequences display drying- upward depositional trends in 

which small eolian dunes and sandsheets of large 

crossbedded dunes overlie sabkha and lacustrine 

deposits (Blakey, 1994). 

Channeling, low- angle cross- stratification, current 

ripple marks, and interbedded sandstone, siltstone, and 

shale suggest a fluvial environment for the Kayenta 

Formation. The rivers developed on a Wingate 

Sandstone surface. Adjacent to the Kayenta rivers were 

sand dunes with high- angled, sweeping crossbeds. These 

sand dunes became the Navajo Sandstone. As the rivers 

migrated, so did the sand dunes so that today, the fluvial 

deposits of the Kayenta Formation often intertongue 

with Navajo Sandstone (Blakey, 1994). 

At Arches, however, the Kayenta separates the Navajo 

from the Wingate Sandstone. The crossbed sets of the 

Navajo Sandstone are bounded by planar surfaces 

thought to represent former water table surfaces. Dip 

directions of the dunes indicate sand transport from 

north to south. Gray limestones and dolomites formed in 

oases, playas, or interdune lakes (Doelling, 1985, 2000). 

During the Lower Jurassic, the northern sea did not 

encroach onto the continent. At this time, erosion of 

Triassic and Upper Paleozoic sandstones from as far 

north as Montana and Alberta provided abundant 

quantities of sand to be transported by wind to the 

Colorado Plateau (Kocurek and Dott, 1983). The volcanic 

arc along the western margin of North America may have 

acted as a wall to block the southwest wind and channel 

it to the south (Kocurek and Dott, 1983). 

Middle Jurassic Period – 

Carmel, Entrada, Curtis Formations. 

When the pace of collision increased off the western 

coast in the Middle Jurassic, the rock layers on the 

continent side of the collision bulged upward, and as the 

rocks bowed, weathering and erosion stripped away the 

rocks. The unconformity surface that formed on the 

Navajo Sandstone is called the J- 2 regional 
 ARCH Geologic Resource Evaluation Report 31

unconformity surface, see figures 9 and 10 (Pipiringos 

and O’Sullivan, 1978). 

As plate tectonic activity increased, the sea began to 

onlap the continent from the north. The Dewey Bridge 

member of the Carmel Formation was deposited on 

broad tidal flats marginal to a shallow sea that lay to the 

west (Wright et al., 1962). The Dewey Bridge member 

may interfinger with the Page Sandstone member of the 

Carmel that has been suggested to be present in the 

vicinity of Ham Rock (comments from ARCH staff, July 

9, 2003). The Page Sandstone is an eolian sandstone that 

pinches out to the east on the west flank of the 

Monument uplift (Peterson, 1994). 

The Entrada Sandstone, lying above the Dewey Bridge 

member of the Carmel Formation, is the most 

widespread of the preserved late Paleozoic and Mesozoic 

eolianites and also the most important geologic unit in 

Arches National Park with respect to arch formation. 

Most of the arches in the park are associated with the 

lower and upper contacts of the Entrada. The crossstratified sandstone was deposited in an extensive dune 

field in a back- beach area (figure 14) (Kocurek and Dott, 

1983; Hintze, 1988; Doelling, 2000). 

A renewed marine incursion, less extensive than the first, 

is recorded in the marine fossils found in the Curtis 

Formation to the west of the Arches area. In western and 

central Utah, the Curtis is separated from the Entrada by 

another regional unconformity, the J- 3 unconformity 

(Pipiringos and O’Sullivan, 1978; Doelling, 2000). In 

Arches National Park, the Moab member of the Curtis 

Formation is a resistant sandstone that caps many 

Entrada sandstone cliffs. The Moab sandstones have 

been interpreted as small eolian dune fields although 

specific details on the Moab depositional environment 

are lacking (Peterson, 1994). 

Upper Jurassic Period – 

Summerville and Morrison Formations 

As lithospheric plate collision increased on the western 

margin in the Upper Jurassic, a major transgression of 

the inland seaway forever destroyed the vast eolian sand 

seas that once covered the Colorado Plateau. Tidal flats 

covered the area as marine environments encroached 

from the north. 

Two additional marine transgression/ regression 

couplets occurred in the Upper Jurassic before the seas 

finally receded to the north. During northward retreat of 

the sea, the Summerville Formation was deposited. The 

sandstones and siltstones of the thin Summerville 

Formation exposed at Arches were deposited in a delta 

that was marginal to a shallow sea to the west (Peterson, 

1994: Doelling, 2000). 

As the sea regressed to the north, the extensive Upper 

Jurassic, Morrison Formation was deposited across the 

continental Western United States. The Morrison 

Formation is world renowned for both its dinosaur 

bones and its uranium deposits (Peterson, 1994). 

Morrison environments are quite varied. Sediments were 

deposited in mudflats, overbank floodplains, stream 

channels, small eolian sand fields, and scattered lakes 

and ponds (Peterson, 1994). Today, little vegetation 

grows on the banded pink, green, and gray shales of the 

Morrison Formation that paint a vivid landscape over 

parts of the Colorado Plateau. 

The Tidwell member of the Morrison Formation 

probably represents fluvial overbank deposits and 

associated lake deposits. The Salt Wash member is also a 

fluvial deposit intertonguing with the Tidwell member. 

The sandstones represent channel deposits in a braided 

river system while the muddy siltstones are overbank 

flood deposits. The conglomeratic and lithic sandstones 

of the upper Brushy Basin member are also the products 

of a fluvial system that deposited channel sandstones and 

floodplain sediments as well as lake deposits. 

Lower Cretaceous Period – 

Cedar Mountain Formation 

Fast- flowing streams from the southwestern Mogollon 

Highlands incised into the softer shales and siltstones of 

the Upper Jurassic Morrison Formation, eroded 

sediment, and generated another gap in time between the 

Jurassic and Cretaceous Periods. Coarse- grained, Lower 

Cretaceous rocks form the Cedar Mountain Formation 

at ARCH. Paleocurrent directions show that Cedar 

Mountain sediments came from drainage systems 

coming out of central Utah (Elder and Kirkland, 1994). 

The sandstones, mudstones, and nodular limestones 

represent low- energy floodplain, fluvial, and interfluvial 

lacustrine deposits (Elder and Kirkland, 1994; Doelling, 

2000). About 15 million years is missing between the 

uppermost Cedar Mountain Formation and the base of 

the Upper Cretaceous Dakota Formation in central Utah 

(Hintze, 1988). 

Upper Cretaceous Period – 

Dakota Sandstone and Mancos Shale 

As the Late Cretaceous dawned, this continental 

landscape experienced a dramatic change. An 

epicontinental sea once again inundated Utah in the Late 

Cretaceous. Only rising mountains in western Utah 

(Sevier Orogeny) limited the westward expansion of 

marine waters. 

As the mountains rose in the west, the north- south 

trough that formed adjacent to the mountains subsided, 

and marine water began to spill into the basin from both 

the Gulf of Mexico and the Arctic Ocean. As the shallow 

sea advanced onto the continent, longshore currents 

flowing parallel to the shoreline redistributed the 

sediments deposited from river systems in much the 

same way sediments are redistributed along the 

shorelines of North America today. 
 NPS Geologic Resources Division 32 

The sea advanced, retreated, and readvanced many times 

during the Cretaceous until the most extensive interior 

seaway ever to cover the continent drowned much of 

western North America from about 95 to 65 Ma (figure 

15). The advances and retreats of the Cretaceous 

shoreline created a myriad of environments including 

incised river valley systems, estuaries, coal swamps, 

lagoons, delta systems, beaches, and offshore marine 

deposits. The interfingering of these environments is 

very complex, and the sedimentary rocks formed from 

the sediments include a variety of lithologies that have 

been grouped together into the Dakota Sandstone on the 

Colorado Plateau. 

In general, the Dakota represents deposition on a broad 

coastal plain and in lagoons shoreward of the advancing 

Western Interior Seaway. Coal swamps formed in the 

quiet backwaters of estuaries. Some of the sandstones 

may have been deposited in paleovalleys incised into the 

coastal plain during a regressive episode (Gardner and 

Cross, 1994). With burial and increased temperature, the 

organic material in the Dakota Formation began to be 

transformed into coal and hydrocarbons. The coarsegrained sandstone layers became reservoirs for oil, gas, 

and groundwater. 

Only part of the Mancos Shale is exposed at Arches 

National Park. The Mancos Shale is the youngest 

bedrock unit in Arches National Park and was deposited 

in the advancing Cretaceous seaway. The calcareous 

marine mudstones that comprise the lower part of the 

Tununk member (figure 16) were deposited during a 

transgression that flooded the Dakota Sandstone 

environments (Gardner and Cross, 1994). The 

paleobathymetry over eastern Utah was approximately 

328- 656 ft (100- 200 m) deep at this time (Sageman and 

Arthur, 1994). The lower Tununk shales represent the 

maximum extent of the Cretaceous Interior Sea (figure 

16) (Elder and Kirkland, 1994). Pluton emplacement was 

quite active on the western margin of North America and 

volcanoes erupted great quantities of volcanic ash 

(Christiansen et al., 1994). 

The sandstones of the Ferron Sandstone member were 

deposited during a regression. Although undifferentiated 

in ARCH, the Ferron Sandstone has been subdivided in 

Utah into a lower unit of shelf sandstones and an upper 

unit of nonmarine sandstone and mudstone (Gardner 

and Cross, 1994). 

The fossiliferous, marine mudstones of the Blue Gate 

member resulted from another transgressive episode. At 

this time the sea lay adjacent to the Sevier thrust belt. 

For roughly ten million years, clay, silt, sand, and shell 

debris were deposited in the Cretaceous Interior Sea. At 

first glance, the formation appears to be 2000+ ft (700 m) 

of uniform, monotonous black and gray shales with a few 

scattered limestone beds. Yet, the history of the Mancos 

on the Colorado Plateau reflects at least four major, 

dramatic changes in depositional systems where 

shoreline and near- shore environments were destroyed 

and new environments created as sea level rose and fell 

(Aubrey, 1991). In addition, fossil evidence suggests that 

ocean currents within the Cretaceous Interior Sea were 

variable. At times, the currents circulated oxygenated 

water throughout the water column allowing life to 

prosper at all levels, including within the muddy sea 

bottom. Conversely, at other times, the circulation in the 

Seaway was restricted to the upper water layer, and 

black, organic- rich muds accumulated in the oxygenpoor sea bottom. In those environments, the fossil 

material includes very few, if any, bottom fauna. As the 

organic- rich mud was buried, heat and pressure 

transformed the organic material to hydrocarbons. 

In time, these hydrocarbons would flow upward, out of 

the buried Mancos mud and into overlying and adjacent 

reservoirs. 

Late Cretaceous – Early Tertiary Laramide Orogeny 

The onset of the Laramide Orogeny (about 70 to 35 Ma) 

was marked by a pronounced eastward shift in 

deformation throughout Utah and into Colorado. Thrust 

faults produced in the Laramide Orogeny cut deeply into 

Earth’s crust, thrusting ancient plutonic and 

metamorphic basement rocks to the surface. In contrast, 

basement rocks were rarely involved in Sevier thrusting. 

The Sevier Orogeny (about 105 to 75 Ma) is an example of 

thin- skinned thrust faulting wherein just the upper 

sedimentary strata of Earth’s crust is transported on 

laterally extensive thrust planes that dip at a low angle, 

generally 10- 15 degrees, from the horizontal surface of 

Earth. Thrust faults associated with the Late CretaceousEarly Tertiary Laramide Orogeny are an example of 

thick- skinned deformation. The faults have steeply 

dipping fault planes at the surface of Earth that curve and 

sole out in Precambrian basement crystalline rock at 

depths up to 9 km (9000 m) (5.7 mi or 30,000 ft) below 

sea level (Gries, 1983; Erslev, 1993). 

During the Laramide Orogeny, the tectonic forces that 

folded and faulted the entire geologic column, from 

Precambrian to Cretaceous age rocks, into the northsouth trending Rocky Mountains and adjoining basins 

had seemingly little effect on the Colorado Plateau. 

Where the Rocky Mountains became basement- cored 

arches bounded by thrust faults and separated by 

sediment- filled basins, the Colorado Plateau, on the 

other hand, was primarily warped into broad anticlinal 

and synclinal folds with very little large- scale (kms) 

faulting (Dickinson and Snyder, 1978; Chapin and 

Cather, 1983; Hamilton, 1988; Erslev, 1993). 

Although not as severely deformed as rocks in the 

adjacent Rocky Mountains, the rocks in Arches National 

Park were faulted and folded during the Late Cretaceous 

and early Tertiary Laramide Orogeny. The regional dip 

of the park is 2 to 4 degrees northwards towards the 

Uinta Basin and away from the Monument upwarp to the 

south. 
 ARCH Geologic Resource Evaluation Report 33

Cenozoic Era 

Tertiary Period – Overview 

No Tertiary- age rocks are exposed in ARCH, but for 

about 35 million years during the Laramide Orogeny, the 

collision of the tectonic plates transformed the extensive 

basin of the Cretaceous Interior Seaway into smaller 

interior basins bordered by rocky mountains. The 

Colorado Plateau, as a whole, was uplifted and tilted in 

the latest Cretaceous- early Tertiary so that streams, 

flowing to the northwest, began to erode the underlying 

sedimentary rocks and deposit gravels and sandstones 

across the area (Fassett, 1985; Aubrey, 1991). 

Quaternary Period – Overview 

The Quaternary Period is subdivided into two epochs: 1) 

the Pleistocene, which ranges from about 1.6 Ma to 

10,000 years before present (B.P.), and 2) the younger 

Holocene Epoch that extends from 10,000 years B.P. to 

the present. The Pleistocene Epoch is known as the Ice 

Age and is marked by multiple episodes of continental 

and alpine glaciation. Great continental glaciers, 

thousands of feet thick, advanced and retreated over 

approximately 100,000- year cycles. Huge volumes of 

water were stored in the glaciers during glacial periods so 

that sea level dropped as much as 91 m (300 ft) (Fillmore, 

2000). When sea level lowered, land bridges emerged 

such as the Bering Land Bridge that linked North 

America and the Eurasian continents. During interglacial 

periods, Earth warmed and the glaciers retreated toward 

the polar regions. Sea level rose and the great land masses 

were once again isolated. 

Geologically, the Colorado Plateau has not changed 

much during the Holocene, the Age of Man. The 

Colorado Plateau as a whole has been subjected to 

repeated minor uplifts and stream rejuvenation since the 

end of the ice age. During the cooler, more humid 

climates of Pleistocene time, streams cut headward into 

canyons, developing the drainage pattern seen today. 

Today, the climate is drier; yet, the intermittent streams 

in the canyons are still in a period of active downcutting, 

only at a slower rate than in the past. The prehistoric 

floods that once scoured the canyons are mostly an event 

of the past since the construction of Glen Canyon dam, 

Hoover dam, and the other dams on the Colorado River 

drainage. 
 NPS Geologic Resources Division 34 

Figure 11: Schematic reconstruction of Pangaea showing the approximate Permian location of the Colorado Plateau (black box) and

the United States (green). The rest of the land mass is shown in white. Round inset: Partial reconstruction of Pangaea depicting 

different orientation and thus rotation of the Colorado Plateau. From Dubiel et al., 1996. 
 ARCH Geologic Resource Evaluation Report 35

Figure 12: Lower Triassic paleogeography. Moenkopi Formation in the Four-Corners region is deposited during the second 

transgressive episode of the Early Triassic. Other formations include the Thaynes, Sinbad, and Timpoweap. ARCH: Arches National

Park. Modified from Dubiel, 1994. 
 NPS Geologic Resources Division 36 

Figure 13: Paleogeographic map of the Upper Triassic. UN: Uncompahgre uplift; SL: San Luis uplift; FR: Front Range uplift. Highlands 

are shaded a solid gray. Modified from Dubiel, 1994. 
 ARCH Geologic Resource Evaluation Report 37

Figure 14: Middle Jurassic Period paleogeography during deposition of the Entrada Sandstone. Note that the northern marine 

environments have eliminated the sand source to the north, yet Entrada-age ergs are widespread. ARCH: Arches National Park. 

Modified from Peterson, 1994. 
 NPS Geologic Resources Division 38 

Figure 15: Location of the Cretaceous seaway. Shaded areas indicate land above sea level. “S.O.B.” and inverted “V”s indicate the 

Sevier Orogenic belt. “M.H.?” is the Mogollon Highland in southwestern Arizona. ARCH: Arches National Park. North indicates the

Cretaceous north. Modified from Rice and Shurr, 1983. 
 ARCH Geologic Resource Evaluation Report 39

Figure 16: Upper Cretaceous paleogeography at the time of Tununk Shale member, Mancos Shale, deposition. Solid triangles mark the 

leading edge of thrust faulting with the triangles on the overriding plate. A lacuna is an unrecorded stratigraphic record at an erosion 

surface caused by either erosion or non-deposition. ARCH: Arches National Park. Diagram modified from Elder and Kirkland, 1994.
 NPS Geologic Resources Division 40 

Figure 17: Geologic time scale. Red lines indicate major unconformities between eras. Absolute ages shown are in millions of years. 

Scale is from the U.S.G.S. 
 ARCH Geologic Resource Evaluation Report 41

References 

This section provides a listing of references cited in this report. A more complete geologic 

bibliography is available and can be obtained through the NPS Geologic Resources 

Division. 

Aubrey, W. M., 1991, Geologic framework and 

stratigraphy of Cretaceous and Tertiary rocks of the 

southern Ute Indian Reservation, southwestern 

Colorado: USGS Professional Paper 1505- B, 24 p. 

Baars, D. L., 2000, The Colorado Plateau: University of 

New Mexico press, Albuquerque, NM, 254 p. 

Becker, L., Poreda, R. J., Hunt, A. G., Bunch, T. E., and 

Rampino, M., 2001, Impact event at the PermianTriassic boundary: Evidence from extraterrestrial 

noble gases in fullerenes, in Science, Feb. 23, p. 1530-

1533. 

Blakey, R. C., 1994, Paleogeographic and tectonic 

controls on some Lower and Middle Jurassic erg 

deposits, Colorado Plateau, in Mario V. Caputo, James 

A. Peterson, and Karen J. Franczyk, eds., Mesozoic 

Systems of the Rocky Mountain Region, USA: Rocky 

Mountain Section, SEPM (Society for Sedimentary 

Geology), Denver, CO., p. 273- 298. 

Campbell, J. A., 1980, Lower Permian depositional 

systems and Wolfcampian paleogeography, 

Uncompahgre Basin, eastern Utah and southwestern 

Colorado, in T. D. Fouch and E. R. Magathan, eds., 

Paleozoic Paleogeography of the West- Central United 

States, SEPM (Society for Sedimentary Geology), p. 

327- 340. 

Chapin, C. E. and Cather, S. M., 1983, Eocene tectonics 

and sedimentation in the Colorado Plateau – Rocky 

Mountain area, in James Lowell, ed., Rocky Mountain 

Foreland Basins and Uplifts: Rocky Mountain 

Association of Geologists, Denver, CO., p. 33- 56. 

Chenoweth, W. L., 1996, The Uranium industry in the 

Paradox Basin, in A.C. Huffman, Jr., W.R. Lund, and 

L.H. Godwin, eds., Geology and Resources of the 

Paradox Basin: Utah Geological Association 

Guidebook 25, p. 95- 108. 

Christiansen, E. II, Kowallis, B. J., and Barton, M. D., 

1994, Temporal and spatial distribution of volcanic ash 

in Mesozoic sedimentary rocks of the Western 

Interior: an alternative record of Mesozoic 

magmatism, in Mario V. Caputo, James A. Peterson, 

and Karen J. Franczyk, eds., Mesozoic Systems of the 

Rocky Mountain Region, USA: Rocky Mountain 

Section, SEPM (Society for Sedimentary Geology), 

Denver, CO., p. 73- 94. 

Cole, R.D., Moore, G.E., Trevena, A.S., Armin, R.A., and 

Morton, M.P., 1996, Lithofacies definition in Cutler 

and Honaker Trail Formations, Northeastern Paradox 

Basin, by sedimentologic observations and spectral 

gamma- ray data, in A.C. Huffman, Jr., W.R. Lund, and 

L.H. Godwin, eds., Geology and Resources of the 

Paradox Basin: Utah Geological Association 

Guidebook 25, p. 169- 178. 

Condon, S. M., 1997, Geology of the Pennsylvanian and 

Permian Cutler Group and Permian Kaibab Limestone 

in the Paradox Basin, Southeastern Utah and 

Southwestern Colorado: U.S.G.S. Bulletin 2000- P, 46 

p. 

Cruikshank, K.M., 1993, Fracture patterns associated 

with Salt Valley anticline: Stanford, California, 

Stanford University Proceedings of the Rock Fracture 

Project, v. IV, 10 p. 

Cruikshank, K.M., and Aydin, A., 1993, Joint patterns in 

Entrada Sandstone, southwest limb of Salt Valley 

anticline, Arches National Park, Utah, USA: Stanford, 

California, Stanford University, 25 p. 

Cudlip, L., Berghoff, K., and Vanna- Miller, D., 1999, 

Water resources management plan: Arches National 

Park and Canyonlands National Park: National Park 

Service, Water Resources Division, Fort Collins, CO., 

153 p. 

Dane, C.H., 1935, Geology of the Salt Valley anticline and 

adjacent areas, Grand County, Utah: U.S.G.S. Bulletin 

863, 184 p. 

De Voto, R. H., 1980, Pennsylvanian stratigraphy and 

history of Colorado, in Harry C. Kent and Karen W. 

Porter, eds., Colorado Geology: Rocky Mountain 

Association of Geologists, p. 71- 102. 

Dickinson, W. R., and Snyder, W.S., 1978, Plate tectonics 

of the Laramide orogeny, in V. Matthews III, ed., 

Laramide folding associated with basement block 

faulting in the western United States: Geological 

Society of America, Memoir 151, p. 355- 366. 

Doelling, H.H., 1985, Geologic map of Arches National 

Park and vicinity, Grand County, Utah: Utah 

Geological and Mineral Survey Map 74, 15 p., scale 

1:50,000. 
 NPS Geologic Resources Division 42 

Doelling, H. H., 2000, Geology of Arches National Park, 

Grand County, Utah, in D.A. Sprinkel, T.C. Chidsey, 

Jr., and P.B. Anderson, eds., Geology of Utah’s Parks 

and Monuments: Utah Geological Association 

Publication 28, p. 11- 36. 

Dubiel, R. F., 1994, Triassic deposystems, 

paleogeography, and paleoclimate of the Western 

Interior, in Mario V. Caputo, James A. Peterson, and 

Karen J. Franczyk, eds., Mesozoic Systems of the 

Rocky Mountain Region, USA: Rocky Mountain 

Section, SEPM (Society for Sedimentary Geology), 

Denver, CO., p. 133- 168. 

Dubiel, R. F., Huntoon, J. E., Condon, S. M., Stanesco, J. 

D., 1996, Permian deposystems, paleogeography, and 

paleoclimate of the Paradox Basin and vicinity, in 

M.W. Longman and M.D. Sonnenfeld, eds., Paleozoic 

Systems of the Rocky Mountain Region: Rocky 

Mountain Section, SEPM (Society for Sedimentary 

Geology), p. 427- 444. 

Duffy, S., 1993, “Synopsis of the dinosaur megatrack site 

in Arches National Park”, in V. L. Santucci, ed., 

National Park Service Natural Resources Technical 

Report NPS/NRPO/NRTR- 93/11:4 

Dyer, J.R., 1983, Jointing in sandstones, Arches National 

Park, Utah: Stanford, Stanford University, Ph.D. 

dissertation, 202 p. 

Elder, W. P. and Kirkland, J. I., 1994, Cretaceous 

paleogeography of the southern Western Interior 

Region, in Mario V. Caputo, James A. Peterson, and 

Karen J. Franczyk, eds., Mesozoic Systems of the 

Rocky Mountain Region, USA: Rocky Mountain 

Section, SEPM (Society for Sedimentary Geology), 

Denver, CO., p. 415- 440. 

Engelmann, G. F. and Hasiotis, S. T., 1999, “Deep 

dinosaur tracks in the Morrison Formation: sole marks 

that are really sole marks”, in D. D. Gillette, ed., 

Vertebrate Paleontology in Utah: Utah Geological 

Survey Miscellaneous Publication 99- 1, p. 179- 183. 

Erslev, E. A., 1993, Thrusts, back- thrusts, and 

detachment of Rocky Mountain foreland arches, in C. 

J. Schmidt, R. B. Chase, and E. A. Erslev, eds., 

Laramide Basement Deformation in the Rocky 

Mountain Foreland of the Western United States: 

Geological Society of America, Special Paper 280, p. 

339- 358. 

Fassett, J. E., 1985, Early Tertiary paleogeography and 

paleotectonics of the San Juan Basin area, New Mexico 

and Colorado, in R.M. Flores and S.S. Kaplan, eds., 

Cenozoic Paleogeography of West- Central United 

States: Rocky Mountain Section, SEPM (Society for 

Sedimentary Geology), p. 317- 334. 

Fillmore, R., 2000, The Geology of the Parks, 

Monuments and Wildlands of Southern Utah: The 

University of Utah Press, 268 p. 

Fouret, K. L., 1996, Depositional and diagenetic 

environments of the Mississippian Leadville 

Limestone at Lisbon Field, Utah, in A.C. Huffman, Jr., 

W.R. Lund, and L.H. Godwin, eds., Geology and 

Resources of the Paradox Basin: Utah Geological 

Association Guidebook 25, p. 133- 138. 

Gardner, M. H. and Cross, T. A., 1994, Middle 

Cretaceous paleogeography of Utah, in Mario V. 

Caputo, James A. Peterson, and Karen J. Franczyk, 

eds., Mesozoic Systems of the Rocky Mountain 

Region, USA: Rocky Mountain Section, SEPM 

(Society for Sedimentary Geology), Denver, CO., p. 

1471- 502. 

Gries, R., 1983, North- south compression of Rocky 

Mountain foreland structures, in James D. Lowell and 

Robbie Gries, eds., Rocky Mountain Foreland Basins 

and Uplifts: Rocky Mountain Association of 

Geologists, p. 9- 32. 

Hamilton, W. B., 1988, Laramide crustal shortening: 

Geological Society of America, Memoir 171, p. 27- 39. 

Harris, A. G., Tuttle, E., Tuttle, Sherwood D., 1997, 

Geology of National Parks, 5th edition, Kenkall/Hunt 

Publishing Company, pg. 80- 91. 

Hintze, L.F., 1988, Geologic history of Utah: Brigham 

Young University Studies Special Publication 7, 202 p. 

Hite, R.J., 1961, Potash- bearing evaporite cycles in the 

salt anticlines of the Paradox basin, Colorado and 

Utah: US.G.S. Professional Paper 424D, p. D136- D138. 

Huntoon, J. E., Stanesco, J. D., Dubiel, Russell F., and 

Dougan, J., 2000, Geology of Natural Bridges National 

Monument, Utah, in D.A. Sprinkel, T.C. Chidsey, Jr., 

and P.B. Anderson, eds., Geology of Utah’s Parks and 

Monuments: Utah Geological Association Publication 

28, p. 233- 250. 

Kirkland, J.I, Cifelli, R.L., Britt, B.B., Burge, D.L., 

DeCourten, F.L., Eaton, J.G., and Parrish, J.M., 1999, 

Distribution of vertebrate faunas in the Cedar 

Mountain Formation, east- central Utah, in D.D. 

Gillette, ed., Vertebrate paleontology of Utah: Utah 

Geological Survey Miscellaneous Publication 99- 1, p. 

201- 217. 

Kocurek, G. and Dott, R. H. Jr., 1983, Jurassic 

paleogeography and paleoclimate of the central and 

southern Rocky Mountain region, in Mitchell W. 

Reynolds and Edward D. Dolly, eds., Mesozoic 

Paleogeography of the West- Central United States: 

Rocky Mountain Section, SEPM (Society for 

Sedimentary Geology), Denver, CO., p. 101- 118. 
 ARCH Geologic Resource Evaluation Report 43

Lawton, T. F., 1994, Tectonic setting of Mesozoic 

sedimentary basins, Rocky Mountain region, United 

States, in Mario V. Caputo, James A. Peterson, and 

Karen J. Franczyk, eds., Mesozoic Systems of the 

Rocky Mountain Region, USA: Rocky Mountain 

Section, SEPM (Society for Sedimentary Geology), 

Denver, CO., p. 1- 26. 

Lockley, M. G., 1990, Tracking the Rise of Dinosaurs in 

Eastern Utah: Canyon Legacy 2: 2- 8. 

Lockley, M.G., 1991, The Moab megatracksite: A 

preliminary description and discussion of millions of 

Middle Jurassic tracks in eastern Utah, in W.R. 

Averett, ed., Dinosaur quarries and tracksites tour, 

western Colorado and eastern Utah: Grand Junction 

Geological Society, Grand Junction, Colorado, p. 59-

65. 

Lockley, M.C., Kirkland, J.I., DeCourten, F.L., Britt, B.B., 

and Hasiotis, S.T., 1999, Dinosaur tracks from the 

Cedar Mountain Formation of eastern Utah – a 

preliminary report, in D.D. Gillette, ed., Vertebrate 

Paleontology in Utah: Utah Geological Survey 

Miscellaneous Publication 99- 1, p. 253- 257. 

Loope, D.B., Sanderson, G.A., and Verville, G.J., 1990, 

Abandonment of the name Elephant Canyon 

Formation in southeastern Utah: Physical and 

temporal implications: Mountain Geologist, v. 27, no. 

4, p. 119- 130. 

McKnight, E.T., 1940, Geology of an area between Green 

and Colorado Rivers, Grand and San Juan Counties, 

Utah: U.S.G.S. Bulletin 908, 147 p. 

Mead, J. I., Sharp, S. E., and Agenbroad, L. D., 1991, 

Holocene Bison from Arches National Park, 

southeastern Utah: Great Basin Naturalist 51 (4), p. 

336- 342. 

Molenaar, C.M., and Cobban, W.A., 1991, Middle 

Cretaceous stratigraphy on the south and east sides of 

the Uinta Basin, northeastern Utah and northwestern 

Colorado: U.S.G.S. Bulletin 1787- P, 34 p. 

Nation, M.J., 1990, Analysis of eolian architecture and 

depositional systems in the Jurassic Wingate 

Sandstone, central Colorado Plateau: unpublished 

M.S. thesis, Northern Arizona University, 222 p. 

O’Sullivan, R.B., 1980, Stratigraphic sections of Middle 

Jurassic San Rafael Group and related rocks from the 

Green River to the Moab area in east- central Utah: 

U.S.G.S. Map MF- 1247. 

O’Sullivan, R.B., 1981, Stratigraphic sections of Middle 

Jurassic San Rafael Group and related rocks from Salt 

Valley to Dewey Bridge in east- central Utah: U.S.G.S. 

Oil and Gas Investigations Chart OC- 113. 

Peterson, F., 1994, Sand dunes, sabkhas, stream, and 

shallow seas: Jurassic paleogeography in the southern 

part of the Western Interior Basin, in Mario V. Caputo, 

James A. Peterson, and Karen J. Franczyk, eds., 

Mesozoic Systems of the Rocky Mountain Region, 

USA: Rocky Mountain Section, SEPM (Society for 

Sedimentary Geology), Denver, CO., p. 233- 272. 

Pipiringos, G.N., and O’Sullivan, R.B., 1978, Principal 

unconformities in Triassic and Jurassic rocks, western 

interior United States – a preliminary survey: U.S.G.S. 

Professional Paper 1035- A, 29 p. 

Rice, D. D. and Shurr, G. W., 1983, Patterns of 

sedimentation and paleogeography across the Western 

Interior Seaway during time of deposition of Upper 

Cretaceous Eagle Sandstone and equivalent rocks, 

northern Great Plains, in Mitchell W. Reynolds and 

Edward D. Dolly, eds., Mesozoic Paleogeography of 

the West- Central United States: Rocky Mountain 

Section, SEPM (Society for Sedimentary Geology), p. 

337- 358. 

Rueger, B. F., 1996, Palynology and its relationship to 

climatically induced depositional cycles in the Middle 

Pennsylvanian (Desmoinesian) Paradox Formation of 

Southeastern Utah: U.S.G.S. Bulletin 2000- K, 4 plates, 

22 p. 

Sageman, B. B. and Arthur, M. A., 1994, Early Turonian 

paleogeographic/paleobathymetric map, Western 

Interior, U.S., in Mario V. Caputo, James A. Peterson, 

and Karen J. Franczyk, eds., Mesozoic Systems of the 

Rocky Mountain Region, USA: Rocky Mountain 

Section, SEPM (Society for Sedimentary Geology), 

Denver, CO., p. 457- 470. 

Sanderson, G.A. and Verville, G.J., 1990, Fusulinid 

zonation of the General Petroleum No. 45- 5- G core, 

Emery County, Utah: Mountain Geologist, v. 27, no. 4, 

p. 131- 136. 

Santucci, V. L., 2000, A survey of paleontologic resources 

from the National Parks and Monuments in Utah: in

Mario V. Caputo, James A. Peterson, and Karen J. 

Franczyk, eds., Mesozoic Systems of the Rocky 

Mountain Region, USA: Rocky Mountain Section, 

SEPM (Society for Sedimentary Geology), Denver, 

CO., p.535- 556. 

Scott, R. B., Harding, A. E., Hood, W. C., Cole, R. D., 

Livaccari, R. F., Johnson, J. B., Shroba, R. R., 

Dickerson, R. P., 2001, Geologic map of Colorado 

National Monument and adjacent areas, Mesa County, 

Colorado: U.S. Geological Survey, Geologic 

Investigations Series I- 2740, 1:24,000 scale. 

SEUG/GRI Workshop, 1999, Geologic Resources 

Inventory Workshop Summary: Southeast Utah Group 

National Park, Utah: National Park Service, Geologic 

Resources and Natural Resources Information 

Divisions, 18 p. 
 NPS Geologic Resources Division 44 

Statement of Management Report, 1990, Arches National 

Park: National Park Service, 34 p. 

Stewart, J.H., Poole, F.G., and Wilson, R. F., 1972A, 

Stratigraphy and origin of the Triassic Moenkopi 

formation and related strata in the Colorado Plateau 

region: USGS Prof Paper 690, 336p. 

Stewart, J.H., Poole, F.G., and Wilson, R.F., 1972B, 

Stratigraphy and Origin of the Chinle Formation and 

related Triassic strata in the Colorado Plateau region: 

U.S.G.S. Professional Paper 690, 336 p. 

Stone, D. S., 1986, Seismic and borehole evidence for 

important pre- Laramide faulting along the axial arch 

in northwest Colorado, in Donald S. Stone, ed., New 

Interpretations of Northwest Colorado Geology: 

Rocky Mountain Association of Geologists, p. 19- 36. 

Wray, J.L., 1983, Pennsylvanian algal carbonates and 

associated facies, central Colorado: International 

Symposium on Fossil Algae, 3rd, Field Guide, 29 p. 

Wright, J.C., Shawe, D.R., and Lohman, S.W., 1962, 

Definition of members of Jurassic Entrada Sandstone 

in east- central Utah and west- central Colorado: 

American Association of Petroleum Geologists 

Bulletin, v. 46, no. 11, p. 2057- 2070. 
 ARCH Geologic Resource Evaluation Report 45

Appendix A: Geologic Map and Cross Section Graphics 

This image provides a preview or “snapshot” of the geologic map and cross section for 

Arches National Park. For a detailed digital geologic map, see included CD. 

The original maps digitized by NPS staff to create this product was: Doelling, D.M., 1985, Geologic map of the Arches National Park 

and vicinity, Grand County, Utah, Utah Geological Survey, UGS 74, 1:50000 scale. For a detailed digital geologic map and cross 

sections, see included CD. 
 NPS Geologic Resources Division 46 
 ARCH Geologic Resource Evaluation Report 47

Appendix B: Scoping Summary 

The following excerpts are from the GRE scoping summary for Arches National Park 

and other parks located in southeastern Utah. The scoping meeting occurred May 24- 27, 

1999; therefore, the contact information and Web addresses referred to herein may be 

outdated. At the time of this meeting the GRE program was known as the Geologic 

Resources Inventory (GRI).Please contact to the Geologic Resources Division for current 

information. 

Executive Summary 

An inventory workshop was held for national park 

service units in the Southeast Utah Group (Arches NP, 

Canyonlands NP, Hovenweep NM, and Natural Bridges 

NM) from May 24- 27, 1999 to view and discuss the 

geologic resources, to address the status of geologic 

mapping by the Utah Geological Survey (UGS) for 

compiling both paper and digital maps, and to assess 

resource management issues and needs. Cooperators 

from the NPS Geologic Resources Division (GRD), 

Natural Resources Information Division (NRID), 

Southeast Utah Group NPS staff (interpretation, natural 

resources, deputy superintendents), UGS, United States 

Geological Survey (USGS), and Utah Geological 

Association (UGA) were present for the two day 

workshop. 

• Monday May 24th involved a field trip to Natural 

Bridges NM (NABR) led by Red Rocks College 

geologist Jack Stanesco with additions from Christine 

Turner and Pete Peterson (both of the USGS). 

• Tuesday May 25th involved a field trip to Canyonlands 

NP (CANY) led by USGS geologist George Billingsley, 

again with additions from Christine Turner and Pete 

Peterson also of the USGS. 

• Wednesday May 26th involved a field trip to Arches 

NP (arch) led by UGS geologist Hellmut Doelling with 

additions from Grant Willis (UGS) and Vince Santucci 

(NPS- GRD). 

An on- line slide show of the highlights of these field 

trips can be found at 

http://www.nature.nps.gov/grd/geology/gri/ut/seug/field

_trip_seug 

• Thursday May 27th involved a scoping session to 

present overviews of the NPS Inventory and 

Monitoring (I&M) program, the Geologic Resources 

Division, and the ongoing Geologic Resources 

Inventory (GRI) for Colorado and Utah. Round table 

discussions involving geologic issues for the Southeast 

Utah Group included interpretation, the UGA 

Millennium 2000 guidebook featuring the geology of 

Utah's National and State parks, paleontological 

resources, the status of cooperative geologic mapping 

efforts, sources of available data, geologic hazards, 

potential future research topics, and action items 

generated from this meeting. Brief summaries of each 

follows. 

Overview of Geologic Resources Inventory 

After introductions by the participants, Joe Gregson 

(NPS- NRID) presented an overview of the NPS I&M 

Program, the status of the natural resource inventories, 

and the geological resources inventory. 

He also presented a demonstration of some of the main 

features of the digital geologic map for the Black Canyon 

of the Gunnison NM and Curecanti NRA areas in 

Colorado. This has become the prototype for the NPS 

digital geologic map model as it ideally reproduces all 

aspects of a paper map (i.e. it incorporates the map notes, 

cross sections, legend etc.) with the added benefit of 

being a GIS component. It is displayed in ESRI ArcView 

shape files and features a built- in help file system to 

identify the map units. It can also display scanned JPG or 

GIF images of the geologic cross sections supplied with 

the map. The cross section lines (ex. A- A') are 

subsequently digitized as a shape file and are hyperlinked 

to the scanned images. 

For a recap on this process, go to: 

http://www.nature.nps.gov/grd/geology/gri/blca_cure/ 

and view the various files in the directory. 

The geologists at the workshop familiar with GIS 

methods were quite impressed with this method of 

displaying geologic maps digitally; Gregson is to be 

commended for his accomplishments. 

Bruce Heise (NPS- GRD) followed with an introduction 

to the NPS GRD group. 

Interpretation 

The GRI also aims to help promote geologic resource 

interpretation within the parks and GRD has staff and 

technology to assist in preparation of useful materials 

including developing site bulletins and resource 

management proposal (RMP) statements appropriate to 

promoting geology. Jim Wood (GRD) and Melanie 

Moreno (USGS- Menlo Park, CA) have worked with 

several other NPS units in developing web- based 

geology interpretation themes, and should be considered 

as a source of assistance should the park desire. 

Along the lines of interpretation of geology for the 

SEUG, it was suggested that they consider hiring a fulltime geologist to be on staff to evaluate research 

proposals and generally assist all interpretive areas 

within the SEUG to find out what issues should be 
 NPS Geologic Resources Division 48 

addressed. A geologist could add greatly to NABR, 

CANY, and ARCH because the primary theme of these 

parks is geologic; there would be no bridges, arches, or 

canyon (lands) without the underlying influence of 

geology and geologic processes upon this part of the 

world. A geologist would also certainly be active in 

establishing the most effective wayside exhibits aimed at 

informing the public about the geologic wonders of the 

area. A geologist can certainly assist in the presentation 

and interpretation of paleontologic resources and issues 

also. 

Such a position could act as a liaison among various tour 

groups, researchers, field camps and professional 

organizations that visit the area because of the 

spectacular geology. Geologic hazards would also be able 

to be more fully understood. Obviously, effective 

communication skills are a highly desirable quality for 

any applicant. 

In the absence of such a position, the GRD is most 

willing to assist the SEUG in any geologic matters and 

issues should they desire. Please contact Bruce Heise or 

Tim Connors to discuss further matters regarding 

geologic resources. 

UGA Guidebook on Utah’s National and State Park 

Areas 

Doug Sprinkel of the UGA announced that a guidebook 

treating the geology of 27 of Utah's national and state 

parks and monuments will be compiled for publication 

in September 2000. This compilation will be a snapshot 

into the geology of each park and covers most facets of 

what the GRI is trying to develop for each park for a final 

report (i.e. cross sections, simplified geologic map, 

general discussions of rocks, structure, unique aspects of 

park geology, classic viewing localities). Each author will 

be encouraged to get with NPS staff interpreters to 

develop a product that aims at a wide audience (the 

common visitor, the technical audience and the teaching 

community). Authors for SEUG parks are as follows: 

• Arches NP: Hellmut Doelling (UGS) 

• Canyonlands NP: Donald Baars 

• Natural Bridges NM: Jackie Huntoon, Russell Dubiel, 

Jack Stanesco 

Also, a CD- ROM will be distributed with the publication 

featuring road and trail logs for specific parks as well as a 

photo glossary and gallery. Park authors are strongly 

encouraged to get with NPS staff to make sure that any 

trail logs do follow maintained trails and do not take 

visitors into unauthorized areas, or places where 

resources are fragile and would be disturbed by 

increased visitation (i.e. areas with crytptogamic soils). 

The photo glossary will describe certain geologic features 

(i.e. what is crossbedding?). These will also be available 

as web- downloadable Adobe Acrobat PDF files. The 

UGA cannot copyright this material because it is funded 

with state money, so it can be distributed widely and 

freely, which will also benefit the purposes of the GRI. 

Additional reprints are not a problem because of the 

digital nature of the publication and the UGA board is 

committed to additional printings as needed. UGA 

normally prints 1000 copies of their publications because 

they become dated after about five years; that will 

probably not be an issue for this publication. Prices for 

the full- color guidebook are estimated to be 

approximately $25/copy, and sales are expected to be 

high (exact estimates for Capitol Reef NM were 125 

copies/year). A website for the guidebook is forthcoming 

in October 1999. 

Field Trips will be held in September 2000. Currently, 

four field trips are scheduled: 

1. Arches NP, Canyonlands NP, Dead Horse Point State 

Park (SP) 

2. type of project could serve as a model for other states 

to follow to bolster Antelope Island SP and Wasatch 

Mountain SP 

3. Southeast Utah Group NP, Cedar Breaks NM, Snow 

Canyon SP and Quail Creek SP 

4. Dinosaur NM, Flaming Gorge NRA, and Red Fleet SP 

Note: Trips 1 and 2 will run concurrently and Trips 3 and 

4 will also run concurrently. 

Many other benefits are anticipated from this publication 

and are enumerated below: 

• This tourism and book sales promoting their state and 

its geologic features. 

• Sandy Eldredge (UGS) will be targeting teaching 

communities for involvement in the field trips; 

hopefully teachers will pass on what they have learned 

to their young audience. 

• The language is intended to appeal to someone with a 

moderate background in geology and yet will be very 

informative to the educated geologist. 

• The publication may be able to serve as a textbook to 

colleges teaching Geology of National Parks (in Utah). 

• A welcomed by- product could be roadlogs between 

parks in Utah for those visiting multiple parks, perhaps 

with a regional synthesis summarizing how the overall 

picture of Utah geology has developed. 

Disturbed Lands 

GRD's John Burghardt has done work in Lathrop 

Canyon on reclaiming abandoned mineral lands (AML). 

His reports should be studied as a significant source of 

data for this area to determine if additional work needs 
 ARCH Geologic Resource Evaluation Report 49

to be performed. Dave Steensen (GRD) heads the AML 

program and can also be contacted. 

Paleontological Resources 

The field trip at Arches NP provided glimpses into the 

paleontological resources (dinosaur bones) near Delicate 

Arch. It has been suggested to keep this location low 

profile to minimize disturbances and potential theft or 

vandalism. 

During the scoping session, the importance of a 

paleontological resource inventory for the Cedar 

Mountain and Morrison Formations near the Dalton 

Wells Quarry was discussed as being a priority. The 

important resources are likely to be dinosaur bones. A 

staff geologist or paleontologist would surely be useful 

for this purpose. 

Vince Santucci (NPS- GRD Paleontologist) will be coauthoring a "Paleontological Survey of Arches National 

Park" and detailing findings of resources within the park. 

Plants, invertebrates, and vertebrate tracksites are among 

the recognized paleontological resources within the 

Southeast Utah Group area parks. 

Similar surveys have been done for Yellowstone and 

Death Valley NP's and have shed valuable new 

information on previously unrecognized resources. 

These surveys involve a literature review/bibliography 

and recognition of type specimens, species lists, and 

maps (which are unpublished to protect locality 

information), and also make park specific 

recommendations for protecting and preserving the 

resources. 

The Death Valley Survey will be available soon. The 

Yellowstone Survey is already available on- line at: 

http://www.nature.nps.gov/grd/geology/paleo/yell_surve

y/index.htm 

and is also available as a downloadable PDF at 

http://www.nature.nps.gov/grd/geology/paleo/yell.pdf 

Paleontological resource management plans should be 

produced for Southeast Utah Group involving some 

inventory and monitoring to identify human and natural 

threats to these resources. Perhaps someone on the park 

staff could be assigned to coordinate paleontological 

resource management and incorporate any findings or 

suggestions into the parks general management plan 

(GMP). It would be useful to train park staff (including 

interpreters and law enforcement) in resource 

protection, as the fossil trade "black market" has become 

quite lucrative for sellers and often results in illegal 

collecting from federal lands. 

Collections taken from this area that now reside in 

outside repositories should be tracked down for 

inventory purposes. Fossils offer many interpretive 

themes and combine a geology/biology link and should 

be utilized as much as possible in interpretive programs. 

Status of Geologic Mapping Efforts for the SEUG 

Status of Existing Maps 

It should be noted that the following paper geologic 

maps exist: 

• Arches NP ("Geologic Map of Arches National Park 

and vicinity, Grand County, Utah" by Hellmut H. 

Doelling, 1985) at 1:50,000. The area was mapped at 

1:24,000 scale, but compiled at 1:50,000 scale. 

• Canyonlands NP ("Geologic Map of Canyonlands 

National Park and Vicinity, Utah" by George 

Billingsley, Peter Huntoon, and William J. Breed, 1982) 

at 1:62,500 

• Canyonlands NP ("Bedrock Geologic Map of 

Upheaval Dome, Canyonlands NP, Utah" by Gene 

Shoemaker, Herkenhoff and Kriens, 1997); scale 

unknown. 

George Billingsley noted that when he worked on the 

Canyonlands map, he mostly compiled previous 

material. He thought several additions to the Quaternary 

deposits and the placement of joints/fractures on the 

maps would improve the quality of the 1982 Canyonlands 

map. There are also some issues regarding assignment of 

the Page Sandstone, and the controversy of the Dewey 

Bridge Member of the Entrada versus the Carmel 

Formation being within the map area. He thinks 

eventually, the entire area should be compiled at 1:24,000 

to better enhance features and add to resource 

management. 

Jackie Huntoon has told Bruce Heise that she is working 

on a digital coverage for Natural Bridges, but needs the 

hypsography (contour lines) to complete her work. 

Desired quadrangles that NRID has this coverage for are 

the following: 

• The Cheesebox 

• Woodenshoe Buttes 

• Kane Gulch 

• It is not sure if the coverage exists for the Moss Back 

Butte quadrangle; Joe Gregson will look into it. 

Digitized Maps 

The 1985 Arches map has been digitized into an ArcInfo 

coverage by SEUG staff. The attribute quality is 

unknown however, and will be researched. NPS- GRI 

folks will work with SEUG GIS Specialist Gery 

Wakefield to learn more about this coverage 

The 1982 Canyonlands map is not known to have been 

digitized at this point and hopefully can be done by the 

SEUG GIS staff. George Billingsley says that the 

Canyonlands Natural History Association has the 

original line work and mylars; Diane Allen said she will 

contact them to see if they still have this work. 
 NPS Geologic Resources Division 50 

The 1997 Upheaval Dome map is digitized as an ArcInfo 

coverage and a copy was given to Craig Hauke (CANY) 

from George Billingsley. It also contains cross sections 

and a report. A website exists for this work at: 

http://www.seismo.unr.edu/ftp/pub/louie/dome/98seism

o/index.html 

UGS Mapping Activities in SEUG area 

Currently, the UGS is mapping in Utah at three different 

scales: 

• 1:24,000 for high priority areas (i.e. National and State 

parks) 

• 1:100,000 for the rest of the state 

• 1:500,000 for a compiled state geologic map 

The UGS plans to complete mapping for the entire state 

of Utah within 10- 15 years at 1:100,000 scale. For 

1:100,000 scale maps, their goal is to produce both paper 

and digital maps; for 1:24,000 scale maps, the only digital 

products will be from "special interest" areas (i.e. areas 

such as Southeast Utah Group and growing metropolitan 

St. George). Grant Willis mentioned that the UGS simply 

does not have enough manpower and resources to do 

more areas at this scale. He also reiterated that UGS 

mapping goals are coincident with those of the National 

Geologic Mapping Program. 

Grant Willis talked about the status of UGS mapping 

activities within the Southeast Utah Group area. 30 x 60 

sheets (at 1:100,000) for the area include the La Sal 

(greater Canyonlands area) and Moab (Arches NP) 

sheets, which are currently in progress (paper and digital 

format). 

Below is a brief summary of various mapping projects for 

SEUG parks from the UGS: 

Park Quadrangle Status 

Klondike Bluffs UGS (Doelling) mapping in Progress 

Mollie Hogans UGS (Doelling) mapping in Progress 

Cisco SW Slated for future work 

Big Bend Paper map published 1998; not digitized 

The Windows Section UGS (Doelling) mapping in Progress 

Merrimac Butte In publication 

Gold Bar Canyon Published 

Moab- 16 Ready for press 

Arches NP 

Moab (30x60) Digital and printed map in progress 

Hanksville Nothing currently; hopefully in a few years Canyonlands NP La Sal Digital and printed map in progress 

Natural Bridges NM Hite Crossing 

Blanding Nothing slated at this time 

Other Sources of Natural Resources Data for SEUG 

• The UGS has a significant quadrangle database that 

they have furnished to NRID for the entire state of 

Utah. 

• NRID has compiled a geologic bibliography for 

numerous parks and monuments, including all parks in 

the Southeast Utah Group. Visit the website at: 

http://165.83.36.151/biblios/geobib.nsf; user id is 

"geobib read", password is "anybody". 

• SEUG GIS specialist showed a digitized version of 

Hellmut Doelling's 1985 map as and ArcInfo coverage; 

attribution needs to be checked; other coverage's 

should be sought that may exist from the previous GIS 

specialist. 

• GRD has several entries regarding abandoned mineral 

land (AML) sites in their database that should be 

checked for data validity and compared with park 

records; John Burghardt (GRD) should be contacted 

regarding this 

• The Arches NP visitor center sells a publication that 

has an inventory of all the arches of Arches 

• The UGS has compiled a CD- ROM with well 

locations, pipelines, etc. for the state of Utah; GRD 

should obtain a copy of this. Parks may also desire 

copies too. 
 ARCH Geologic Resource Evaluation Report 51

Geologic Hazards 

There are numerous issues related to geologic hazards in 

and around the Southeast Utah Group parks. Below is a 

brief list of some mentioned during the scoping session: 

• Landslide and rockfall potential along all roads that 

occasionally cause road closures; of special note was 

the problem with the main road in Arches, just above 

the visitor center 

• Landscape Arch (arch) collapsed in a few places 

several years ago and was recorded by a tourist 

• Swelling soils associated with bentonitic shale's of the 

Chinle, Morrison, and Mancos formations 

• Radon potential associated with mine closures 

• Earthquake potential along the Moab Fault 

Potential Research Topics for SEUG NP 

A list of potential research topics includes studies of the 

following: 

• What are the connections between gypsiferous rocks 

and cryptobiotic soils/crusts?; why were the crust 

healthier on the gypsum- bearing rocks? 

• How long will Delicate Arch stand? 

• Engineering studies to determine hazards to visitors; 

use strain meter 

• Use High resolution GPS to detect moving, swelling, 

and collapse in areas of the parks 

• Rock color studies 

• Subsurface seismic work for voids in the Needles 

around synclines and salt dome structures 

• Locate real unconformity between Entrada Moab 

Tongue and abutting formations 

Action Items 

Many follow- up items were discussed during the course 

of the scoping session and are reiterated by category for 

quick reference. 

Interpretation 

• More graphics and brochures emphasizing geology 

and targeting the average enthusiast should be 

developed. If Southeast Utah Group NP needs 

assistance with these, please consult GRD's Jim Wood 

(jim_f._wood@nps.gov) or Melanie Moreno at the 

USGS- Menlo Park, CA (mmoreno@usgs.gov). 

• Consider the possibility of hiring a full- time geologist 

to handle geologic issues for the SEUG; in the absence 

of this consult with GRD for assistance in geologic 

matters 

UGA Guidebook 

• Attempt to plant the seeds of this concept to other 

states for similar publications involving local area 

geology. Such publications are especially useful for the 

GRI 

• Have authors prepare logs that are "sensitive" to 

delicate areas in the park (i.e. where less user impact is 

desired) 

Paleontological Resources 

• For now, try to minimize location disclosure of 

vertebrate sites to minimize disturbances and the 

potential for theft or vandalism 

• Develop an in- house plan to inventory, monitor and 

protect significant paleontological resources from 

threats; assign staff to oversee especially in regard to 

the Dalton Wells area 

• Locate collections taken from the park residing in 

outside repositories 

Geologic Mapping 

• Attempt to complete digital coverage for the entire 

SEUG area from existing maps 

• Locate already existing digital coverage's (like that of 

Doelling's 1985 Arches map) 

• Work closely with UGS to finish paper and digital 

coverage of SEUG area where maps are lacking 

• Work with cooperators (NABR- Jackie Huntoon) to 

ensure there work could be incorporated into the 

master plan of the GRI. 

Natural Resource Data Sources 

• Examine GRD databases for AML and disturbed lands 

for data validity 

• Attempt to locate other digital coverage's from the 

previous SEUG GIS specialist (Eric) for Gery 

Wakefield's (current SEUG GIS specialist) inventory 

Miscellaneous 

• Review proposed research topics for future studies 

within Southeast Utah Group NP 

• Promote sensitivity to delicate resources (crusts, etc.) 

to researchers, and visiting park groups 
 NPS Geologic Resources Division 52 

Participants 

NAME AFFILIATION PHONE E- MAIL 

Joe Gregson NPS, NRID (970) 225- 3559 Joe_Gregson@nps.gov 

Tim Connors NPS, GRD (303) 969- 2093 Tim_Connors@nps.gov 

Bruce Heise NPS, GRD (303) 969- 2017 Bruce_Heise@nps.gov 

Christine Turner USGS (303) 236- 1561 Cturner@usgs.gov 

Fred Peterson USGS (303) 236- 1546 Fpeterson@usgs.gov 

Jack Stanesco Red Rocks CC (303) 914- 6290 Jack.Stanesco@rrcc.cccoes.edu 

Craig Hauke NPS, CANY (435) 259- 3911 

ext. 2132 Craig_hauke@nps.gov 

Grant Willis UGS (801) 537- 3355 Nrugs.gwillis@state.ut.us 

George Billingsley USGS- Flagstaff, 

AZ (520) 556- 7198 Gbillingsley@usgs.gov 

Vince Santucci NPS, GRD (307) 877- 4455 Vince_Santucci@nps.gov 

Jim Dougan NPS, NABR (435) 692- 1234 Jim_Dougan@nps.gov 

Al Echevarria Red Rocks CC (303) 985- 5996 Ale44@juno.com 

Dave Wood NPS, CANY (435) 259- 3911 

ext. 2133 Dave_Wood@nps.gov 

Traci Kolc NPS, CANY (435) 259- 4712 

ext. 18 Traci_Kolc@nps.gov 

Margaret Boettcher NPS, ARCH SCA (435) 259- 1963 Margaret_arches@hotmail.com 

Clay Parcels NPS, ARCH (435) 259- 8161 

ext. 245 Clay_Parcels@nps.gov 

Alicia Lafever NPS, ARCH (435) 259- 8161 

ext. 242 Alicia_Lafever@nps.gov 

Adrienne Gaughan NPS, ARCH (435) 259- 8161 

ext. 286 Adrienne_Gaughan@nps.gov 

Shawn Duffy NPS, ARCH (435) 259- 7223 Shawn_Duffy@nps.gov 

Murray Shoemaker NPS, ARCH (435) 259- 8161 

ext. 244 Murray_Shoemaker@nps.gov 

Helmut Doelling UGS (435) 835- 3652 None 

Doug Sprinkel UGS / UGA (801) 782- 3398 Sprinkel@vii.com 

Jim Webster NPS, ARCH (435) 259- 8161 

ext. 220 Jim_Webster@nps.gov 

Gery Wakefield NPS, SEUG 

GIS coordinator 

(435) 259- 3911 

ext. 2180 Gery_Wakefield@nps.gov 

Phil Brueck NPS, SEUG (435) 259- 3911 

ext. 2102 Phil_Brueck@nps.gov 

Bruce Rodgers NPS, SEUG (435) 259- 3911 

ext. 2130 Bruce_Rodgers@nps.gov 

Diane Allen NPS, ARCH (435) 259- 8161 Diane_Allen@nps.gov 

Paul Henderson NPS, SEUG (435) 259- 3911 

ext. 2140 Paul_Henderson@nps.gov 
 ARCH Geologic Resource Evaluation Report 53

Overview of Geologic Resources Inventory 

The NPS Geologic Inventory is a collaborative effort of 

the NPS Geologic Resources Division (GRD) and 

Inventory and Monitoring Program (I&M) with 

assistance from the U.S. Geological Survey (USGS), 

American Association of State Geologists (AASG), and 

numerous individual volunteers and cooperators at NPS 

units, colleges, and universities. 

From the perspective of the servicewide I&M Program, 

the primary focus (Level 1) of the geological inventory is 

1. to assemble a bibliography of associated geological 

resources for NPS units with significant natural 

resources, 

2. to compile and evaluate a list of existing geologic maps 

for each unit, 

3. to develop digital geologic map products, and 

4. to complete a geological report that synthesizes much 

of the existing geologic knowledge about each park. 

The emphasis of the inventory is not to routinely 

initiate new geologic mapping projects, but to 

aggregate existing information and identify where 

serious geologic data needs and issues exist in the 

National Park System. 

The NPS Geologic Resources Division is an active 

participant in the I&M Program and has provided 

guidance and funding in the development of inventory 

goals and activities. GRD administers the Abandoned 

Mine Lands (AML) and Geologists In Parks (GIP) 

programs which contribute to the inventory. NPS 

paleontologists, geologists, and other natural resource 

professionals also contribute to inventory planning and 

data. A major goal of the collaborative effort is to provide 

a broad baseline of geologic data and scientific support 

to assist park managers with earth resource issues that 

may arise. 

For each NPS unit, a cooperative group of geologists and 

NPS personnel (the Park Team) will be assembled to 

advise and assist with the inventory. Park Teams will 

meet at the each NPS unit to discuss and scope the 

geologic resources and inventory, which is the subject of 

this report. If needed, a second meeting will be held at a 

central office to evaluate available geologic maps for 

digital production. After the two meetings, digital 

geologic map products and a geologic report will be 

produced. The report will summarize the geologic 

inventory activities and basic geology topics for each 

park unit. Due to the variety of geologic settings 

throughout the NPS, each report will vary in subject 

matter covered, and section topics will be adapted as 

needed to describe the geologic resources of each unit. 

Whenever possible the scientific sections of the report 

will be written by knowledgeable cooperators and peer 

reviewed for accuracy and validity. 
 NPS Geologic Resources Division 54 
 ARCH Geologic Resource Evaluation Report 55
 NPS Geologic Resources Division 56 
The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and other 

information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated Island 

Communities. 

Arches National Park 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2004/005 

NPS D-197, November 2004 

National Park Service 

Director • Fran P. Mainella 

Natural Resource Stewardship and Science 

Associate Director • Michael A. Soukup 

Natural Resource Program Center 

The Natural Resource Program Center (NRPC) is the core of the NPS Natural Resource Stewardship and 

Science Directorate. The Center Director is located in Fort Collins, with staff located principally in 

Lakewood and Fort Collins, Colorado and in Washington, D.C. The NRPC has five divisions: Air 

Resources Division, Biological Resource Management Division, Environmental Quality Division, Geologic 

Resources Division, and Water Resources Division. NRPC also includes three offices: The Office of 

Education and Outreach, the Office of Inventory, Monitoring and Evaluation, and the Office of Natural 

Resource Information Systems. In addition, Natural Resource Web Management and Partnership 

Coordination are cross-cutting disciplines under the Center Director. The multidisciplinary staff of NRPC 

is dedicated to resolving park resource management challenges originating in and outside units of the 

national park system. 

Geologic Resources Division 

Chief • David B. Shaver 

Planning Evaluation and Permits Branch Chief • Carol McCoy 

Credits 

Author • Dr. John Graham

Editing • Sid Covington and Lisa Norby 

Digital Map Production • Stephanie O’Meara 

Map Layout Design • Melanie Ransmeier
Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, CO 80225 

http://www.nature.nps.gov/geology/inventory/ 

(303) 969-2090 

EXPERIENCE YOUR AMERICATM 

National Park Service 

U.S. Department of the Interior