National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 

Grand Teton National Park 

and John D. Rockefeller, Jr. Memorial Parkway 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/230 
THIS PAGE: 

Bison graze on Antelope Flats, below 

the Teton Range, which rises more 

than 2,100 m (7,000 ft) above the 

floor of Jackson Hole. Tectonic forces 

raised the Teton Range and dropped 

Jackson Hole along the Teton fault. 

National Park Service photograph by 

R. Wiles. 

ON THE COVER: 

Visitors at the Mountain View Turnout take in the stunning views of the 

Cathedral Group covered in snow.(L 

to R: Teewinot Mountain, Grand Teton, Mount Owen) . 

National Park Service photograph 
August 2010 

U.S. Department of the Interior 

National Park Service 

Natural Resource Program Center 

Ft. Collins, Colorado

Grand Teton National Park 

and John D. Rockefeller, Jr. Memorial Parkway 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/230 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 
The National Park Service, Natural Resource Program Center publishes a range of reports that 

address natural resource topics of interest and applicability to a broad audience in the National 

Park Service and others in natural resource management, including scientists, conservation and 

environmental constituencies, and the public. 

The Natural Resource Report Series is used to disseminate high-priority, current natural 

resource management information with managerial application. The series targets a general, 

diverse audience, and may contain NPS policy considerations or address sensitive issues of 

management applicability. 

All manuscripts in the series receive the appropriate level of peer review to ensure that the 

information is scientifically credible, technically accurate, appropriately written for the 

intended audience, and designed and published in a professional manner. This report received 

informal peer review by subject-matter experts who were not directly involved in the 

collection, analysis, or reporting of the data. 

Views, statements, findings, conclusions, recommendations, and data in this report do not 

necessarily reflect views and policies of the National Park Service, U.S. Department of the 

Interior. Mention of trade names or commercial products does not constitute endorsement or 

recommendation for use by the U. S. Government. 

Printed copies of this report are produced in a limited quantity and they are only available as 

long as the supply lasts. This report is available from the Geologic Resources Inventory website 

(http://www.nature.nps.gov/geology/inventory/gre_publications.cfm) and the Natural 

Resource Publications Management website (http://www.nature.nps.gov/publications/

NRPM). 

Please cite this publication as: 

KellerLynn, K. 2010. Grand Teton National Park and John D. Rockefeller, Jr. Memorial 

Parkway: geologic resources inventory report. Natural Resource Report NPS/NRPC/GRD/

NRR—2010/230. National Park Service, Fort Collins, Colorado. 

NPS 136/105347, 642/105347, August 2010 

ii NPS Geologic Resources Division 
GRTE Geologic Resources Inventory Report iii

Contents

Lists of Figures and Tables ........................................................................................... iv

Executive Summary ....................................................................................................... v

Acknowledgements...................................................................................................... vi

Introduction ................................................................................................................... 1

Purpose of the Geologic Resources Inventory ...............................................................................................................1

Park and Parkway Setting.............................................................................................................................................1

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

Seismic Activity ............................................................................................................................................................5

Mass Wasting ..............................................................................................................................................................6

Fluvial Features and Processes ......................................................................................................................................7

Glaciers and Climate Change........................................................................................................................................8

Mineral Resources and Management............................................................................................................................9

Bentonite...................................................................................................................................................................11

Cave and Karst Resources ..........................................................................................................................................11

Climbing....................................................................................................................................................................11

Jackson Lake Dam......................................................................................................................................................12

Paleontological Resources ..........................................................................................................................................12

Geologic Features and Processes................................................................................ 17

Ancient Rocks............................................................................................................................................................17

Young Mountains......................................................................................................................................................17

Dikes.........................................................................................................................................................................17

Geothermal Features..................................................................................................................................................17

Glacial Features..........................................................................................................................................................18

Lakes.........................................................................................................................................................................19

Loess .........................................................................................................................................................................19

Oxbows.....................................................................................................................................................................20

Terraces.....................................................................................................................................................................20

Unconformities..........................................................................................................................................................20

Volcanic Features.......................................................................................................................................................20

Map Unit Properties .................................................................................................... 26

Geologic History .......................................................................................................... 39

Glossary........................................................................................................................ 42

Literature Cited............................................................................................................ 47

Additional References ................................................................................................. 52

Appendix A: Overview of Digital Geologic Data....................................................... 53

Appendix B: Scoping Session Participants ................................................................. 57

Attachment 1: Geologic Resources Inventory Products CD
iv NPS Geologic Resources Division 

List of Figures

Figure 1. Location Map of Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway...............................3

Figure 2. Teton Fault......................................................................................................................................................13

Figure 3. Gros Ventre Slide. ...........................................................................................................................................14

Figure 4. Gros Ventre Slide Boulders. .............................................................................................................................14

Figure 5. Middle Teton Glacier.......................................................................................................................................15

Figure 6. Model of Geomorphic Changes to Snake River System. ...................................................................................16

Figure 7. Archean Rocks of North America.....................................................................................................................22

Figure 8. Diabase Dike on Mount Moran........................................................................................................................22

Figure 9. Jackson Lake Hot Springs. ...............................................................................................................................23

Figure 10. Glacially Carved Landscape............................................................................................................................23

Figure 11. Snake River Terraces......................................................................................................................................24

Figure 12. Snake River Overlook.....................................................................................................................................25

Figure 13. Geologic Timescale........................................................................................................................................28

List of Tables

Table 1. Fossiliferous Paleozoic Strata in Grand Teton National Park ...............................................................................16
GRTE Geologic Resources Inventory v

Executive Summary

This report accompanies the digital geologic map data for Grand Teton National Park and 

John D. Rockefeller, Jr. Memorial Parkway in Wyoming, produced by the Geologic 

Resources Division in collaboration with its partners. It contains information relevant to

resource management and scientific research. This document incorporates preexisting 

geologic information and does not include new data or additional fieldwork.

The NPS Geologic Resources Division held a Geologic 

Resources Inventory (GRI) scoping meeting for Grand 

Teton National Park and John D. Rockefeller, Jr. 

Memorial Parkway on June 21–22, 2005. This report 

expands upon the scoping summary (Covington and 

Ransmeier 2005) and ties geologic issues, features, and 

processes to the geologic maps of the park and parkway. 

During scoping, participants prioritized the following 

geologic issues:

1. Geologic hazard assessment and response, particularly 

as related to earthquakes

2. Streamflow, stream channel morphology, and 

dynamics

3. Glacial and climate change monitoring 

4. Disturbed lands restoration.

This report addresses these issues, which are 

characterized as follows:

• Seismic Activity. The Teton fault is the most important 

factor contributing to the spectacular topography and 

scenery of the Teton Range. The topographic relief 

between Jackson Hole and the summits of the Teton 

Range was probably caused by numerous (10–50) 

magnitude-7 or greater earthquakes during the past 

25,000 to 75,000 years. The most likely seismic hazards 

in the Teton region are ground shaking and

deformation, and associated secondary effects, 

including rock and snow avalanches, landslides, and 

flood inundation of low-lying areas.

• Mass Wasting. The conditions that produce landslides 

in the park and parkway are (1) vulnerable rock, (2) 

slopes parallel to dipping strata, (3) saturated ground, 

(4) seismic activity, and (5) removal of base support by 

undercutting of the slope toe. In addition to landslide 

deposits, talus and related deposits are widespread 

throughout the Teton Range.

• Fluvial Features and Processes. The Snake River and 

its tributaries make up the fluvial system at Grand 

Teton National Park and John D. Rockefeller, Jr. 

Memorial Parkway. The Snake River has both roaring 

rapids and gentle meanders. The high rates of 

aggradation and lateral migration of the Snake River 

system confound attempts to restrict the flow path to 

fixed bridge openings. Levee control along segments 

of the river has changed sedimentation patterns and 

habitat. 

• Glaciers and Climate Change. The 1968 USGS 

topographic map of Grand Teton National Park shows 

nine named glaciers and approximately 136 

undifferentiated glaciers or perennial snow fields. A 

thorough inventory of the park’s glaciers, however, 

has not been conducted to date, and long-term 

documentation is sparse. Past records of glacier extent 

indicate both advance and retreat, although the overall 

trend is one of retreat. Models that simulate the 

response of alpine glaciers in Wyoming to projected 

climate change predict the near-complete 

disappearance of Teton Glacier within 30 to 75 years.

• Mineral Resources and Management. Mineral 

resources of interest in the park and parkway are oil 

and gas, gold, phosphate, coal, gypsum, building stone, 

soapstone, and sand and gravel. Most of the 

abandoned mines in the park are not considered safety 

hazards to park visitors. Grand Teton National Park

contains 38 borrow pits, many of which predate the 

park. Most have been abandoned, but some are still in 

use, primarily for storage. The National Park Service 

has been involved in restoration efforts to reclaim 

some of the abandoned borrow pits, particularly those 

that impact wetlands.

Other issues of management interest are bentonite, cave 

and karst resources, climbing, Jackson Lake Dam, and 

paleontological resources.

In addition to geologic issues of management concern, 

this report highlights the distinctive geologic features and 

processes occurring at Grand Teton National Park, 

including ancient rocks, young mountains, dikes, 

geothermal features, glacial features, lakes, loess, 

oxbows, terraces, unconformities, and volcanic features. 

Of particular interest for John D. Rockefeller, Jr.

Memorial Parkway are geothermal, glacial, and volcanic 

features.

The glossary contains explanations of many technical 

terms used in this report, including terms used in the 

Map Unit Properties Table. Refer to figure 13 for a 

geologic timescale.
vi NPS Geologic Resources Division 

Acknowledgements

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National 

Park Service Inventory and Monitoring Program. The GRI is administered by the 

Geologic Resources Division of the Natural Resource Program Center.

The Geologic Resources Division relies heavily on 

partnerships with institutions such as the U.S. Geological 

Survey, Colorado State University, state geologic surveys, 

local museums, and universities in developing GRI 

products.

Credits

Author

Katie KellerLynn (Colorado State University)

Review

Jack Reed (U.S. Geological Survey)

Jason Kenworthy (NPS Geologic Resources Division)

Editing

Jennifer Piehl (Write Science Right)

Digital Geologic Data Production

Jim Chappell (Colorado State University)

Ethan Schaefer (Colorado State University)

Digital Geologic Data Overview Layout Design

Phil Reiker (NPS Geologic Resources Division)
GRTE Geologic Resources Inventory Report 1

Introduction

The following section briefly describes the National Park Service Geologic Resources 

Inventory and the regional geologic setting of Grand Teton National Park and John D. 

Rockefeller, Jr. Memorial Parkway.

Purpose of the Geologic Resources Inventory 

The Geologic Resources Inventory (GRI) is one of 12 

inventories funded by the National Park Service (NPS) 

Inventory and Monitoring Program. The GRI, 

administered by the Geologic Resources Division of the 

Natural Resource Program Center, is designed to 

provide and enhance baseline information available to 

park managers. The GRI team relies heavily on 

partnerships with institutions such as the U.S. Geological 

Survey, Colorado State University, state geologic surveys, 

local museums, and universities in developing GRI 

products.

The goals of the GRI are to increase understanding of the 

geologic processes at work in parks and to provide sound 

geologic information for use in park decision making. 

Sound park stewardship requires an understanding of 

the natural resources and their role in the ecosystem. 

Park ecosystems are fundamentally shaped by geology. 

The compilation and use of natural resource information 

by park managers is called for in section 204 of the 

National Parks Omnibus Management Act of 1998 and in 

NPS-75, Natural Resources Inventory and Monitoring 

Guideline. 

To realize these goals, the GRI team is systematically 

conducting a scoping meeting for each of the 270 

identified natural area parks and providing a parkspecific digital geologic map and geologic report. These 

products support the stewardship of park resources and 

are designed for nongeoscientists. Scoping meetings 

bring together park staff and geologic experts to review 

available geologic maps and discuss specific geologic 

issues, features, and processes. 

The GRI mapping team converts the geologic maps 

identified for park use at the scoping meeting into digital 

geologic data in accordance with their Geographic 

Information Systems (GIS) Data Model. These digital 

data sets bring an interactive dimension to traditional 

paper maps. The digital data sets provide geologic data 

for use in park GIS and facilitate the incorporation of 

geologic considerations into a wide range of resource 

management applications. The newest maps contain 

interactive help files. This geologic report assists park 

managers in the use of the map and provides an overview 

of park geology and geologic resource management 

issues.

For additional information regarding the content of this 

report and current GRI contact information please refer 

to the Geologic Resources Inventory website at 

http://www.nature.nps.gov/geology/inventory/.

Park and Parkway Setting

The iconic peaks of the Teton Range are woven into our 

nation’s identity. They have served as a landmark for 

American Indians, trappers, prospectors, explorers, 

scientists, pilots, and vacationers. More than 2 million 

visitors have come to the park each year since 1993 to 

experience this spectacular landscape, which “captures 

the essence of Grand Teton National Park’s and John D. 

Rockefeller, Jr. Memorial Parkway’s importance to our 

natural and cultural heritage” (National Park Service 

1995, p. 7).

Dynamic geologic forces created these dramatic 

landscape features. Tectonic forces raised the Teton 

Range and dropped Jackson Hole along the Teton fault. 

This active fault extends more than 70 km (40 mi) from 

north to south along the eastern base of the range. 

The Teton Range and Jackson Hole are two halves of a 

landscape meant to be protected and managed as a unit 

(fig. 1). When Grand Teton National Park was 

established in 1929, only the Teton Range and six glacial 

lakes at the foot of the mountains were included within 

its boundaries. The present-day park evolved through a 

complicated process requiring three governmental acts 

and a series of compromises, including (1) protection of 

existing grazing rights and stock driveways,

(2) reimbursement to Teton County for lost tax 

revenues, (3) provision for the controlled reduction of 

elk within park boundaries, (4) agreement that future 

presidential proclamations could not be used to create a 

national monument in Wyoming, and (5) allowance for 

continuation of certain existing uses and access rights to 

forest lands and inholder properties (Skaggs 2000).

Before World War II, strong anti-park sentiment from 

local citizens, stemming from perceived expansion of 

government control and loss of personal freedoms, 

stymied park creation. This sentiment began to change

after World War II, as local citizens realized that tourism 

offered a more attractive economic opportunity than 

ranching, which was difficult in northern Jackson Hole 

(Skaggs 2000).

Established in 1972, the 132-km (82-mi) John D. 

Rockefeller, Jr. Memorial Parkway links Grand Teton 

and Yellowstone national parks. It commemorates the 

efforts of John D. Rockefeller, Jr., who supported an 

integrated national park and in 1927 began to purchase 

and hold land until it could be administered by the 

National Park Service (Harris and Tuttle 1990). 

The parkway is a mountainous region with moderate to 

steep slopes. Situated between the volcanic plateaus of 

Yellowstone National Park and the jagged fault-block 

mountains of Grand Teton National Park, the geology of 
2 NPS Geologic Resources Division 

the parkway largely reflects influences of extraregional 

origin. Sedimentary layers of Cretaceous sandstone and 

shale are present, but lava and ash from Yellowstone 

volcanic features cover much of the Cretaceous bedrock. 

The most prominent volcanic event was the caldera 

eruption that created Yellowstone Lake 600,000 years 

ago (Rodman et al. 1992). This event deposited thick 

layers of rhyolite in the parkway. The Teton fault, so 

significant for Grand Teton National Park, has also 

uplifted the topography and influenced seismic activity 

in the parkway. Glaciers originating in Yellowstone 

National Park entirely covered the parkway during the 

Pleistocene Epoch (2.6 million to 11,700 years ago), 

creating its gouged valleys and rounded mountains 

(Rodman et al. 1992).
GRTE Geologic Resources Inventory Report 

3

Figure 1. Location Map of Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway. The park encompasses nearly 125,460 ha (310,000 ac) of wilderness and some of the most beautiful 

mountain scenery in the world. The road in John D. Rockefeller, Jr. Memorial Parkway extends 132 km (82 mi) between the West Thumb in Yellowstone National Park and the south entrance of Grand 

Teton National Park. The parkway includes approximately 9,700 ha (24,000 ac) of land. National Park Service graphic.

GRTE Geologic Resources Inventory Report 5

Geologic Issues

The Geologic Resources Division held a Geologic Resources Inventory scoping session for

Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway on June 

21–22, 2005, to discuss geologic resources, address the status of geologic mapping, and 

assess resource management issues and needs. This section synthesizes the scoping 

results, in particular those issues that may require attention from resource managers.

Contact the Geologic Resources Division for technical assistance.

During scoping, participants prioritized the following 

geologic issues of concern for management: (1) geologic 

hazards, including seismic activity and mass wasting;

(2) fluvial features and processes; (3) glaciers and climate 

change; and (4) disturbed lands restoration, described in 

the “Mineral Resources and Management” section. 

These issues are presented first, followed by other issues 

of resource management interest.

Seismic Activity

The Teton fault “is the single most important factor 

contributing to the spectacular topography and scenery 

of the Teton Range—hence to the essence of the Grand 

Teton National Park” (Smith et al. 1990b, p. 1). This

major normal fault bounding the east side of the Teton 

Range is the primary structure responsible for the more 

than 2,100 m (7,000 ft) of topographic relief along the 

range front (fig. 2). The Teton Range is part of the 

upthrown footwall block of the fault, and Jackson Hole is 

situated on the downdropped hanging-wall block. The 

Teton fault is a single fault line in some locations, but

splits into a number of separate, closely spaced strands in 

many places (Love et al. 2003). While its development 

began during the deposition of the Colter Formation (24

million to 13 million years ago; see Map Unit Properties 

Table), the modern Teton Range and Jackson Hole are 

largely the results of fault movements within the last 5 

million years. The last 2 million years have been 

particularly significant, given the passage of the 

Yellowstone hot spot close to the northern end of the 

Teton Range (Love et al. 2003; see “Volcanic Features” 

section).

The topographic relief between Jackson Hole and the 

summits of the Teton Range is probably the result of 10 

to 50 magnitude-7 or greater earthquakes during the past 

25,000 to 75,000 years (Byrd 1995). Gilbert et al. (1983) 

and Smith et al. (1990a) estimated offset rates of 1.0 mm 

to 1.5 mm (0.04 in to 0.06 in) per year. These rates do not 

indicate constant fault movement; they likely reflect a 

number of sudden offsets, each accompanied by an 

earthquake, some perhaps of magnitude-7.5 or greater, 

that produced the net displacement along the fault (Love 

et al. 2003). 

The isolated population of Jackson Hole reported 

numerous mild to moderate earthquakes around the time 

of the 1925 Gros Ventre slide, but no one has felt major 

seismic shaking along the Teton fault (particularly the 

northern portion) since Jackson Hole was settled more 

than 100 years ago (Good and Pierce 1996; Smith and 

Siegel 2000). The Teton fault probably occupies a zone of 

seismic quiescence for earthquakes greater than 

magnitude-3 (Byrd et al. 1994). 

A possible implication of the aseismic creep (gradual 

movement on a fault without the generation of seismic 

waves) on the Teton fault is that it is currently 

undergoing stress buildup prior to a large earthquake. 

This interpretation is consistent with the concept that 

the seismic quiescence on the Teton fault is a seismic gap 

that may end with a large-magnitude earthquake (surface 

wave magnitude [Ms] ≥ 6.3), which would most likely 

result in significant ground deformation and disruption 

of roads and structures (Smith et al. 1993). 

A preliminary assessment by Smith et al. (1990b) 

characterized the most probable general seismic hazards 

in the Teton region:

• Ground shaking accompanying a large earthquake that 

results in strong acceleration of the ground surface 

and structures.

• Ground deformation resulting from surface rupture 

along the fault trace and possible subsidence of the 

valley floor.

• Secondary effects associated with ground deformation 

and shaking, including rock and snow avalanches, 

landslides, and flood inundation of low-lying areas.

In addition, scoping participants identified dam failure 

(see “Jackson Lake Dam” section), liquefaction of loosely 

packed sediment or fill, flooding, and building and 

bridge collapse as risks associated with seismic activity 

(Covington and Ransmeier 2005). 

The development of an earthquake hazard response plan 

is a high priority for Grand Teton National Park 

(Covington and Ransmeier 2005). In addition to the 

National Park Service, U.S. Geological Survey, and 

academic partners, such planning would likely involve 

state and local governments, the National Guard, U.S.

Forest Service, Bureau of Reclamation, and possibly the 

U.S. Fish and Wildlife Service. It may also be appropriate 

to solicit ideas, suggestions, and perhaps leadership from

the Federal Emergency Management Agency (FEMA). 

Scoping participants recommended that the hazard 

response plan include a review of possible scenarios, 

strategies for response, an inventory of available 

resources (human and other), and identification of 

responsibilities. 
6 NPS Geologic Resources Division 

As part of the Geoscientist-in-the-Parks (GIP) Program 

administered by the NPS Geologic Resources Division,

Patrice Cobin of Michigan Technological University

served a 90-day assignment at Grand Teton National 

Park in 2009. Cobin updated information on the natural 

hazards, associated risks, and the state of the park’s 

emergency response preparedness. Park officials intend 

for this project to prompt a new hazard response plan 

with engagement of park rangers and the appropriate 

county officials (Sue Consolo-Murphy, Grand Teton 

National Park, Chief of Science and Resource 

Management, e-mail, October 9, 2009).

Other ongoing research and monitoring projects seek to 

better understand seismic activity in the Teton region. 

These projects are examining the historic return time of 

earthquakes on the Teton fault, investigating the 

intermountain seismic belt as a system, and synthesizing 

monitoring data to improve earthquake prediction (Jean 

et al. 2005). Three seismic monitoring stations and one 

continuously recording GPS receiver are currently in 

place within Grand Teton National Park (Jean et al. 

2005). Real-time data from the seismic monitoring 

network are available at http://quake.utah.edu/

helicorder/yell_webi.htm (accessed October 30, 2009). 

The monitoring effort is coordinated by the University of

Utah Seismograph Stations (UUSS) regional and urban 

seismic network, and the stations in the Teton region are 

maintained and operated by the U.S. Geological Survey. 

Braile (2009) suggested methods for monitoring seismic 

activity including: monitoring earthquakes, analysis and 

statistics of earthquake activity, analysis of historical and 

prehistoric earthquake activity, earthquake risk 

estimations, geodetic monitoring and ground 

deformation, and geomorphic and geological indicators 

of active tectonics.

Mass Wasting

Although the majority of mapped landslide deposits are 

located in the upland area east of Grand Teton National 

Park, such deposits also cover areas within the park such 

as Colter Bay, Moose Creek, and Two Ocean and Emma 

Matilda lakes. In addition, geotechnical engineers 

evaluated four slope failures about 1.5 km (0.9 mi) east of 

Moran Junction (fig. 1). These particular failures are 

related to a shallow, perched groundwater aquifer, which 

is concentrated near the surface as a result of an 

underlying drainage barrier (Prellwitz 1998).

Furthermore, while mapping the state’s landslide threat, 

Wyoming officials determined that the Snake River 

drainage was one of the state’s highest risk areas for 

landslides (Smith and Siegel 2000). Between 1989 and 

1991, Marston (1993) documented 53 slope failures in 

the upper Snake River drainage, including slow-moving 

deep slumps, earthflows, and debris flows, and rapidly 

moving shallow debris avalanches and wet debris flows. 

In John D. Rockefeller, Jr. Memorial Parkway, Rodman 

et al. (1992) used slope steepness, evidence of historical 

landslides, shale bedrock, clay content, and the presence 

of seeps and water-loving vegetation to identify map 

units susceptible to landslide hazards. Of the 15 

identified map units, four had landslide potential (units 

23, 30, 31, and 41). These units cover roughly one-third 

of the parkway’s surface and are characterized by glacial 

till and weathered bedrock on gently sloping to very 

steep topography (≤30% to 70% slopes). Predominant 

bedrock from which these units formed is andesite, 

rhyolite, sandstone, shale, and limestone.

During the Pleistocene Epoch, when large glaciers 

advanced and retreated and meltwater ebbed and 

flowed, mass wasting (landsliding) was prevalent, as 

evidenced by abundant Pleistocene-aged landslide 

deposits mapped by Love et al. (1992). However, mass 

wasting continued after the retreat of the large-scale 

glaciers, and continues to the present time. The most 

notorious historic example of mass wasting is the Gros 

Ventre landslide east of the park boundary on June 23, 

1925 (fig. 1). An estimated magnitude-4 earthquake 

triggered the landslide after several weeks of heavy rain 

compounded by late snow melt (Smith and Siegel 2000). 

Some 38 million m3 (50 million yd3

) of rock (Tensleep 

Sandstone over the slippery shale of the Amsden 

Formation) slid 640 m (2,100 ft) down the side of Sheep 

Mountain (fig. 3) (Alden 1926; Lageson and Spearing 

1988; Smith and Siegel 2000). The material traveled

2.4 km (1.5 mi) within 3 to 4 minutes. The fast-moving 

slide crossed the Gros Ventre River and continued 122 m 

(400 ft) up the opposite bank, forming a dam across the 

Gros Ventre River that measured 610 m (2,000 ft) in 

width and 69 m to 76 m (225 ft to 250 ft) in height. In 

1927, this natural dam failed, flooding the town of Kelly. 

The flood killed six people and hundreds of livestock, 

left 40 families homeless, and washed away the fertile 

fields on the floodplain, leaving gravel and boulders

(fig. 4) in its wake (Lageson and Spearing 1988; Smith 

and Siegel 2000). 

The Gros Ventre slide illustrates the landslide-producing 

conditions in the park and parkway: (1) vulnerable rock, 

(2) slopes parallel to dipping strata, (3) saturated ground, 

(4) seismic activity, and (5) removal of base support by 

undercutting the slope toe. In this case, fluvial 

undercutting by the meandering Gros Ventre River

contributed to the loss of base support. According to 

Lageson and Spearing (1988, p. 219), “the situation was 

inevitable; it happened in the past, and will happen again 

when conditions are right.”

In addition to landslide deposits, Love et al. (1992) 

mapped talus and related deposits. These deposits are 

widespread throughout the Teton Range, notably along 

Paintbrush Divide into Paintbrush Canyon, in Granite 

Canyon, and surrounding Middle Teton, Grand Teton, 

and Cloudveil Dome (Love et al. 1992). Love et al. (2003, 

p. 13) described the talus and related deposits as 

“constant reminders that the land surface is restless;” 

these deposits are “the ever-changing piles of rock debris 

that mantle the mountain slopes, the creeping advance of 

rock glaciers, the devastating snow avalanches and the 

thundering rock falls.”

Loosened by freeze-thaw processes, intense rain storms 

(Caine 1974, 1986), and seismic activity, angular blocks 

of talus and abundant smaller rock fragments fall from 

the cliffs and accumulate on the slopes below. Once 
GRTE Geologic Resources Inventory Report 7

deposited, talus can move by the slow process of creep or 

as part of a snow avalanche (Harris and Tuttle 1990). 

Flash floods also efficiently move talus deposits: torrents 

of water running down mountain slopes onto unstable 

deposits of talus can trigger enormous rockslides and 

mudflows. During the summer of 1941, for example, 

more than 100 of these flows occurred in the park. More 

recently, major slides occurred in Granite and Cascade 

canyons in the 1980s (Love et al. 2003). Wieczorek and 

Snyder (2009) suggested five methods and “vital signs” 

for monitoring slope movements: types of landslides, 

landslide triggers and causes, geologic materials in 

landslides, measurement of landslide movement and 

assessing landslide hazards and risks.

Fluvial Features and Processes

The Snake River and its tributaries make up the fluvial 

system at Grand Teton National Park and John D. 

Rockefeller, Jr. Memorial Parkway. Although the Snake 

River is one of the smallest major drainages in Wyoming, 

it carries the largest average volume of any river in the 

state (Kiefling 1978). 

The Snake River begins as a trickle within the Absaroka 

volcanics (Wiggins Formation; see Map Unit Properties 

Table) near the southern boundary of Yellowstone 

National Park. The river flows north into Yellowstone,

where it meanders westward and is joined by the Lewis 

River before looping south into John D. Rockefeller, Jr. 

Memorial Parkway. It flows into Grand Teton National 

Park at the northern end of Jackson Lake, and empties 

out of the lake at the Jackson Lake Dam. The river then 

travels southwest through Jackson Hole. 

The Snake River has both roaring rapids and gentle 

meanders. Marston (1993) characterized the stream 

channel as having pools (slow, deep water with little or 

no surface agitation), glides (fast, deep water with little or 

no surface agitation), riffles (fast, shallow water with 

surface agitation but no standing waves), and rapids (fast, 

deep water with considerable surface agitation, including 

standing waves). Depending on gradient and sediment 

load, stretches of the river can be meandering, braided, 

channelized, or have compound channels that are

transitional between meandering and braiding (Graf 

1988). Sections of the streambed can be bedrock or made 

of boulders, cobbles, gravel, sand, silt, or clay (Marston 

1993).

Sediment load in the system depends on the erodibility 

of bedrock and the availability of glacial outwash. Mass 

wasting contributes large volumes of bedload to streams 

draining from the east (Wyoming State Engineer’s Office 

1972). Additionally, large alluvial fans of quartzite 

cobbles provide a ready input of material where Pilgrim 

Creek and Spread Creek flow into the Snake River 

(Pierce and Good 1992). The Ditch Creek fan, one of the 

largest alluvial fans in the western United States, was 

deposited at the creek’s emergence from the mountains 

east of Jackson Hole. This fan constitutes another 

significant supply of sediment in the park (Smith and 

Siegel 2000). Streams crossing alluvial fans are 

considered chronically unstable because they may shift 

tens of meters in a single, high-flow event (Mott 1998).

The high aggradation and lateral migration rates of the 

Snake River system confound attempts to restrict its flow 

path to bridge openings, such as that over Spring Creek. 

Future damage may best be avoided by redesigning or 

relocating this bridge (Mott 1998). Aggradation also 

causes boat launch areas (e.g., Deadmans Bar) to fill with 

sediment. The National Park Service allows minor 

dredging operations in the immediate vicinity of launch 

areas to provide visitor access to the river (Mott 1998). 

Pleistocene topographic features control the course of 

the Snake River through Grand Teton National Park. It 

follows the giant glacial scour filled by Jackson Lake, and 

flows out of Jackson Lake to the east rather than to the 

west (expected under control of the Teton fault)

following a basin excavated by the westward-flowing 

Pacific Creek glacial lobe during the Burned Ridge 

glaciation (see “Geologic History” section). The river 

runs through a rib of glacially eroded bedrock 

(Mesaverde Formation) just below the mouth of Pacific 

Creek, and passes through a topographic low between 

two outwash fans of different glacial phases (Burned 

Ridge and Hedrick Pond) between Deadmans Bar and 

Moose (Pierce and Good 1992).

Now, anthropogenic features also control the river’s 

course. Below Moose, the U.S. Army Corps of Engineers 

built a 48-km- (30-mi-) long system of levees that blocks 

the river’s lateral spread, reducing floodplain width and 

channel braiding. The levee system also changes 

sedimentation patterns. Fine material is moved through 

the system rather than being deposited in lower-energy 

secondary channels, which would be present in an 

unmodified system. Bedload is also moved more 

frequently in the main channel. Furthermore, levee 

maintenance necessitates almost annual channelization, 

which is especially destructive to trout habitat (Kiefling 

1978).

Another levee system is located along Pilgrim Creek, just 

east of Jackson Lake Dam. The left abutment of Jackson 

Lake Dam rests on the alluvial fan deposited by Pilgrim 

Creek. After construction of the dam, Pilgrim Creek 

changed course and flowed below the dam to merge with 

the Snake River. This realignment brought Pilgrim Creek 

close to the town of Moran, occasionally flooding the 

town site. The Bureau of Reclamation subsequently built 

levees to push Pilgrim Creek north into Jackson Lake 

and alleviate the local flooding problem (Gary Smillie, 

NPS Water Resources Division, Hydrologist, personal 

communication in Mott 1998, p. 41).

While Bureau of Reclamation concerns over dam safety 

have served to justify the maintenance of the Pilgrim 

Creek levee system, such maintenance now may be 

unnecessary for three reasons: (1) the town of Moran no 

longer exists in its former town site, (2) flood control on 

the Snake River can be accommodated through modified 

dam releases, and (3) armoring of the dam abutment is a 

viable alternative. The park’s desired future conditions 

for the Snake River system specify that natural processes 
8 NPS Geologic Resources Division 

should be allowed to occur unimpeded to the maximum 

possible extent, and that existing and future 

development of facilities should minimize the effects on 

or alteration of such processes (Sue Consolo-Murphy, 

Grand Teton National Park, Chief of Science and 

Resource Management, written communication, 2006).

An analysis and declaration by the U.S. Army Corps of 

Engineers that maintenance of the levee system is 

unnecessary would allow restoration of the natural 

migration dynamics associated with Pilgrim Creek (Mott 

1998). Lord et al. (2009) suggested six “vital signs” and 

monitoring methods for fluvial geomorphology: 

watershed landscape, hydrology, sediment transport,

and channel cross section, plan form, and longitudinal 

profile.

Glaciers and Climate Change

The 1968 U.S. Geological Survey topographic map of 

Grand Teton National Park (scale 1:62,500) shows nine 

named glaciers. Mount Moran hosts five of these 

glaciers: the three Triple Glaciers on the north face, 

prominent Skillet Glacier on the east face, and Falling Ice 

Glacier on the southeast face. Teton Glacier lies in the 

shadow of Grand Teton, and Middle Teton Glacier lies 

east of the ridge between Middle Teton and Grand 

Teton (fig. 5). Schoolroom Glacier lies on the park 

boundary east of Hurricane Pass, and Petersen Glacier is 

situated above Mica Lake along the park’s western 

boundary. The 1968 map also identifies approximately 

136 other undifferentiated glaciers or perennial snow 

fields. 

During a warm period following the Pleistocene ice ages, 

the glaciers in this region melted completely. Thereby, 

the park’s extant glaciers are not remnants of the large 

Pleistocene glaciers that once filled the valleys in the 

Teton Range, but vestiges of ice masses built up during 

the Little Ice Age (1400–1850 C.E. [Common Era; 

preferred to “A.D.”]). These modern glaciers can be 

conceived as small-scale models of the great ice masses 

that shaped and sharpened the Tetons during the 

Pleistocene (Love et al. 2003). They are also significant 

reservoirs of water, supplying late-summer agricultural 

and recreational needs. Moreover, the timing and 

intensity of peak flow of glacial meltwater affects 

ecological systems (Elder et al. 1994). 

With the exception of Falling Ice Glacier, which has 

southeast exposure, the glaciers in the national park face 

north or east. All lie in the shadow of major peaks, 

“whose sheer walls, rising to the south and west and 

towering hundreds, or even thousands of feet above 

them, have furnished the protection without which they 

would long since have dwindled to snow fields” (Fryxell 

1935, p. 385). Falling Ice Glacier persists because of the 

depth of its cirque and the protection it receives from the 

huge horns along the southeastern slope of Mount 

Moran, which block direct sunlight from hitting the 

glacier’s surface for a significant portion of the day 

(Fryxell 1935). 

Snow added to glacier mass is supplied in at least three 

ways. First, seasonal snow adds mass. These inputs may

greatly exceed expected quantities for the region, at least 

on the Teton Glacier (Elder et al. 1994). Second, 

avalanches nourish some of the glaciers (e.g., Teton 

Glacier) (Reed 1964). Third, abundant light, dry winter 

snow drifts with the prevailing southwest winds and 

collects in catchment basins on the lee side of the range. 

The park’s glaciers are often characterized as small or 

dwindling; anecdotal evidence provided by park 

employees during scoping suggests that their surface area 

perceptibly diminishes each year (Covington and 

Ransmeier 2005). However, a thorough inventory of the 

park’s glaciers has not been conducted to date, and longterm documentation is sparse. Past records of glacier 

extent show both advance and retreat, although the 

overall trend is one of retreat. 

In 1935, Fritiof Fryxell of Augustana College (Illinois) 

published his observations of seven glaciers in Grand 

Teton National Park—Middle Teton, Teton, Falling Ice, 

Skillet, and the Triple glaciers. The study provided the 

geomorphic/geographic setting, described the glaciers 

and glacial features, and presented the history of 

Pinedale advances in each glacier’s valley (Fryxell 1935). 

In the mid-1960s, Jack Reed of the U.S. Geological 

Survey published his observations (sketch maps, profiles, 

and reports) of the Teton Glacier (Reed 1964, 1965, 

1966, 1967). Reed (1966) discussed photographs from 

1898 showing the terminus of the Teton Glacier situated 

level with the crest of the conspicuous terminal moraine 

that was probably deposited during a Neoglacial 

advance. At that time, the glacier was about 1,220 m 

(4,000 ft) long; the terminus retreated about 150 m

(500 ft) between 1898 and 1954. 

Analysis by Reed (1964) used a 1929 photo by Fryxell 

(Fryxell 1930) that shows the ice surface of the Teton 

Glacier at 12 to 15 m (40 to 50 ft) below the crest of the 

terminal moraine. The change in glacier extent between 

this 1929 photograph and the photos and map provided 

by Reed (1964) show that the glacier had retreated about 

183 m (600 ft) and stood as much as 61 m (200 ft) below 

the crest of the terminal moraine in 1963. Between 1963 

and 1966, the ice increased in thickness by a few feet and 

the glacier advanced about 15 m (50 ft). 

Findings by Williams (1999) showed that the Teton 

Glacier was advancing after 31 years (1924–1955) of 

retreat. Between 1955 and 1998, the Teton Glacier 

increased approximately 8 m (26 ft) in thickness and 20 

m (66 ft) in length. A 5-m (16-ft) increase in thickness in 

the upper part of the glacier since 1990 suggested that the 

terminus would continue to advance temporarily

(Williams 1999). 

In 2009 Glenn Tootle (University of Wyoming) 

presented findings of a preliminary analysis of aerial 

photographs and remote-sensing images, suggesting that 

the Teton Glacier had lost 17% of its areal extent 

between 1967 and 2006 (Glenn Tootle, University of 

Wyoming, Assistant Professor, unpublished abstract, 

September 2009).
GRTE Geologic Resources Inventory Report 9

Plummer (2004) and Plummer and Cecil (2005) used 

mathematical models to simulate the response of alpine 

glaciers in Wyoming to projected climate change. Their 

findings showed that most of the Teton Glacier will have 

melted within 30 to 75 years. Karpilo (2009) suggested 

four “vital signs” and monitoring methods for glaciers: 

glacier mass balance, glacier terminus position, glacier 

area, and glacier velocity.

Globally, retreating glaciers provide evidence for the 

“unequivocal” warming of the climate system (IPCC 

2007). For information regarding climate change impacts 

in the United States, refer to Karl et al. (2009). The 2007 

Intergovernmental Panel on Climate Change (IPCC) 

assessment report contains detailed scientific climate 

change information, viewable on their website at

http://www.ipcc.ch/ (accessed July 30, 2010). The 

National Park Service Climate Change Response 

Program website hosts Servicewide climate change 

information at http://www.nature.nps.gov/

climatechange/index.cfm (accessed July 30, 2010). 

Mineral Resources and Management

According to Antweiler et al. (1989, p. 12), “the mineral 

commodities most worthy of study [in the Teton region] 

are those in sedimentary rocks and include oil and gas, 

gold in placers derived from conglomerates deposited in 

Laramide time, phosphate, metals in black shales, coal, 

gypsum, building stone, sand, and gravel.” However, 

these authors found only low to moderate resource 

potential for these commodities. 

Oil and Gas

Although there are no current oil and gas activities or 

leases in the park or parkway, development outside park 

boundaries could impact park resources. For instance, 

one of the largest onshore natural gas discoveries in the 

United States is Jonah Field, located in the Green River 

Basin southeast of the park and parkway. Geologists 

estimate that this field contains 297 billion cubic meters 

(10.5 trillion cubic feet) of gas. In 2007, the Bureau of 

Land Management approved a plan that would allow 

more than 3,000 wells to be drilled in the field over 75 

years. The gas occurs in tight sands, allowing a higher

well density for oil and gas recovery than that used in 

traditional oil and gas field development (Bureau of Land 

Management and State of Wyoming 2010). The Jonah 

Field is about 48 km (30 mi) south of Pinedale, Wyoming, 

and 160 km (100 mi) southeast of the national park, so air 

quality is the primary resource-management concern 

(Pat O’Dell, Geologic Resources Division, Petroleum 

Engineer, e-mail, October 26, 2009).

Oil and gas activity, including coal bed methane 

development, is currently taking place just northeast of 

the park boundary in the Bridger-Teton National Forest. 

The potential for hydrocarbon occurrence is high in the 

four Forest Service management areas of the BridgerTeton National Forest: the Hoback, Moccasin, Wind 

River, and Green River basins (USDA Forest Service 

1997). 

The Hoback Basin drains directly into the Snake River, 

but the confluence of these rivers is downstream from 

Grand Teton National Park. The Moccasin, Wind River, 

and Green River basins lie immediately east of the Snake 

River drainage and abut the drainage divide, which is 

composed of carbonate strata (Noland and Miller 1995; 

Mott 1998). Cave systems could allow interbasin transfer 

of groundwater, carrying contaminants generated by 

drilling and oil and gas production outside the park to 

springs within the Snake River drainage and Grand 

Teton National Park (Mott 1998).

Gold

Exploration for gold in the mid- to late-1800s was

minimally successful in the Teton region, and did not 

generate a “rush” to the area. Most gold prospectors 

engaged in placer mining, which left little lasting impact 

on the landscape. A few abandoned mine structures, pits, 

and ditches used in placer mining are the only remaining

evidence of this past mining activity.

Phosphate

The Permian Phosphoria Formation contains large 

deposits of phosphorite (calcium phosphate) that is 

commercially mined in Wyoming, Idaho, Utah, and 

Montana for the manufacture of fertilizer and the 

production of phosphorus. The Phosphoria Formation 

crops out in the northern part of the park near Jackass 

Pass and Harem Hill (Love et al. 1992).

Coal

Miners had more success with coal extraction than with 

gold in this region. Coal in the Bacon Ridge Sandstone 

and Sohare Formation has economic potential 

(Antweiler et al. 1989). The Frontier and Mesaverde 

formations also contain coal, but the beds are thin and 

the coal is impure (Antweiler et al. 1989). Within the 

park, subbituminous coal was excavated from an area 

near the Jackson Lake Dam during construction and 

from a mine on Blacktail Butte. 

Gypsum

The Chugwater and Gypsum Springs formations contain 

gypsum (used in drywall), but the beds exposed in the 

Teton–Jackson Hole area are thin and inaccessible 

compared to the large deposits in the Bighorn and Wind 

River basins to the southeast (Antweiler et al. 1989).

Building Stone

The Cambrian Flathead Formation and Mississippian 

Madison Limestone can serve as attractive building 

stones for patios, walkways, and garden walls. The 

geologic map shows two areas where outcrops are 

accessible from U.S. Route 89: Madison Limestone crops 

out north of Moose Junction, and the Flathead 

Formation is accessible near the picnic area northwest of 

Arizona Island, along the shoreline of Jackson Lake. 

Residents of Teton County have also used Huckleberry 

Ridge Tuff for building stone; it is colorful (red, orange, 

pink, purple, and gray), lightweight, moderately durable, 

and easily cut and shaped. Significant sections of U.S. 
10 NPS Geologic Resources Division 

Route 89 were cut through the Huckleberry Ridge Tuff 

in John D. Rockefeller, Jr. Memorial Parkway (Appendix 

A). The Bureau of Reclamation opened a large quarry at 

the northwestern end of Signal Mountain that produced 

riprap for the adjacent Jackson Lake Dam (Antweiler et 

al. 1989). 

Mineral Crystals

Rock collectors may be tempted by the soapstone in the 

park, as well as mica- and garnet-studded gneiss and 

pegmatite. American Indians were the first to mine 

soapstone (talc) in this area. Scientists have documented 

several archaeological sites associated with these mines 

in the Teton Range, at least one of which is within the 

park (Sue Consolo-Murphy, Grand Teton National Park, 

Chief of Science and Resource Management, written 

communication, 2006). Soapstone is dark green or black, 

serpentinized, and heavy. Rock collectors remove 

soapstone pebbles from streams draining the west side of 

the Tetons, cut and polish them, and sell them as “Teton 

jade” (Love et al. 2003). Ultramafic rocks (“Wu” on Map 

Unit Properties Table and Appendix A) are the source of 

Teton jade.

Pegmatite is an exceptionally coarse-grained rock with 

interlocking crystals. Some pegmatite contains plates or 

tabular crystals of silvery white mica (muscovite) up to 15 

cm (6 in) wide, which can be split easily into transparent 

sheets. Other forms of pegmatite contain dark-brown 

mica (biotite) in thin, blade-shaped crystals. In Garnet 

Canyon, some pegmatite bodies contain scattered redbrown garnet crystals. These crystals have a distinctive 

“soccer ball” shape and range from roughly 8 mm (0.3 in) 

to more than 8 cm (3 in). The garnets are fractured and 

many are partly altered to chlorite (a dull-green 

micaceous mineral), so they are of no value as gems 

(Love et al. 2003). The Archean Mount Owen Quartz 

Monzonite, granitic rocks of the Gros Ventre Range, and 

Webb Canyon Gneiss all contain intrusions of pegmatite 

(Love et al. 1992).

To protect these resources from unauthorized collecting, 

scoping participants suggested that park staff monitor 

the accessible areas known to contain these minerals 

(Covington and Ransmeier 2005). Several soapstone 

prospects are located west of the park, near Rammel 

Mountain (Love et al. 2003). Garnet Canyon hosts 

garnets of geologic interest, and mica occurs in pegmatite 

exposures.

Sand and Gravel

According to the Federal Highway Administration 

(1991), Grand Teton National Park and John D. 

Rockefeller, Jr. Memorial Parkway contain 396 km

(246 mi) of roads. This road system is maintained by the 

National Park Service in cooperation with the Federal 

Highway Administration and Wyoming Department of 

Transportation. Road maintenance requires aggregate 

(i.e., sand and gravel). An estimated 1.4 million m3 (1.8 

million yd3) of suitable materials is required over a 20-

year period to preserve and maintain the integrity of 

roads and other infrastructure in the park and parkway

(Federal Highway Administration 1991). Ironically, 

glacial deposits and the Snake River tributaries supply an 

abundance of these materials within the park, but there is 

a shortage of external commercial sources within 

reasonable hauling distance (National Park Service 

1986). NPS policy prohibits the development of new 

borrow pits on NPS lands and stipulates that present 

borrow pits not be utilized unless economic factors make 

it impractical to import materials.

In 1987, 30,582 m3 (40,000 yd3

) of material were 

excavated from the Gros Ventre River on National Elk 

Refuge lands immediately upstream from the bridge over 

U.S. Route 89. Future aggregate needs may be satisfied by 

materials from the Spread Creek drainage on USDA 

Forest Service lands adjacent to the park (Mott 1998). 

The Spread Creek drainage area covers about 280 km2

(108 mi2

) and enters the Snake River about 13 km (8 mi) 

downstream from Jackson Lake Dam. The upper reaches 

of Spread Creek cut through landslides and transport 

large volumes of alluvial material downstream. 

Transported material is deposited behind and 

downstream of a diversion structure located 1.6 km

(1 mi) upstream of the park–national forest boundary, 

adjacent to the proposed mining site (National Park 

Service 1997). The stream gradient decreases, water 

velocity slows, and sediment (i.e., sand, gravel, and 

cobble) deposition increases below the diversion. The 

proposed extraction and staging area is outside the base 

floodplain on an elevated glacial outwash deposit 

(National Park Service 1997). Environmental assessment 

of future aggregate mining in the area does not anticipate 

any impacts to wetlands (Mott 1998).

Abandoned Mine Lands

The National Park Service Abandoned Mine Lands 

(AML) database (accessed August 11, 2010), there are 40 

AML features at 39 sites within Grand Teton National 

Park. One feature at one site is listed for John D. 

Rockefeller, Jr. Memorial Parkway. Most of the 

abandoned mines in the park are not considered safety 

hazards to park visitors. However, scoping participants 

suggested that the National Park Service evaluate the 

Webb Canyon adit for possible closure (Covington and 

Ransmeier 2005). Such an inspection could be completed 

by staff from the NPS Geologic Resources Division.

Grand Teton National Park contains 38 borrow pits

from which at least 76 m3 (100 yd3) of material have been 

excavated. The pits range in size from 0.04 ha to 16 ha 

(0.1 ac to 40 ac) (National Park Service 1986). Many of 

these pits predate the park, and most have been 

abandoned. However, some borrow pits are still in use, 

primarily for storage of aggregate and other materials, 

vehicle storage, and construction staging (John Moeny, 

Grand Teton National Park, Biologist, e-mail, February 

19, 2010). 

The National Park Service has been involved in 

restoration efforts to reclaim some of the abandoned 

borrow pits, primarily those that impact wetlands 

(Covington and Ransmeier 2005). For example, the 

Snake River pit (lower) was a gravel mine from the 1960s 

through 1990s; the National Park Service is currently 
GRTE Geologic Resources Inventory Report 11

restoring the former borrow pit to a wetland, although a 

2-ha (5-ac) portion will be retained as road-construction 

staging (John Moeny, Grand Teton National Park, 

Biologist, e-mail, February 19, 2010).

John D. Rockefeller, Jr. Memorial Parkway managers are 

restoring a 3-ha (8-ac) abandoned gravel mine on the 

Snake River floodplain to a mosaic of willow thickets, 

marshes, wet meadows, ponds, and associated uplands. 

The restored site will provide important wildlife habitat 

for grizzly bears, trumpeter swans, moose, sandhill 

cranes, western boreal toads, and many other wildlife 

species (Wagner 2009). In spring and early summer 2010, 

Intermountain Aquatics, an NPS contractor, planted 

approximately 130,000 nursery-grown, native wetland 

grasses and sedges, as well as willow stakes as part of this

ongoing restoration effort (Joel Wagner, NPS Water 

Resources Division, Wetland Program Leader, e-mail, 

July 29, 2010).

Bentonite

Chemical weathering alters volcanic ash into bentonite, a 

claystone with the ability to absorb large quantities of 

water by greatly increasing in volume (Neuendorf et al. 

2005). Rocks containing bentonite swell when wet and 

shrink when dry, causing the ground surface to heave 

and buckle. Such shrink-and-swell processes can impact 

structures, roads, and trails constructed on bentonite 

beds, producing heaved sidewalks and roads, cracked 

and failed foundations, and slippery and treacherous

trails. Bentonitic clays occur near the park boundary in 

the Toby Pass area and in isolated lenses near Ditch 

Creek and Lost Creek (Covington and Ransmeier 2005).

Covington and Ransmeier (2005) stated that the corner 

of the Jackson Lake Lodge built on the Teewinot 

Formation had apparently been affected by bentonite

shrink and swell. However, neither Love et al. (1992) nor 

Antweiler et al. (1989) identified bentonite in the 

Teewinot Formation. Heaving and subsidence may thus 

be a result of other factors, such as the location of 

building sites on improperly compacted fill material or 

improper drainage around foundations (Pete Biggam, 

Geologic Resources Division, Soil Scientist, e-mail, 

February 23, 2007). A site visit by a soil scientist could 

confirm the source of the problem. The proper 

identification of areas with clay soils is especially 

important for future infrastructure development. Rock 

units with bentonite beds can serve as salt licks for deer 

and elk. For example, bentonite in the Frontier 

Formation contains a bitter salt, and ungulates have 

licked 0.6-m (2.0-ft) holes into some hillside sites

(Antweiler et al. 1989). 

Bentonite is also a mineral resource, although the 

bentonite lenses in the rocks of the Teton region are 

probably insufficiently thick, pure, or accessible for

economic use (Antweiler et al. 1989). 

Cave and Karst Resources 

Because the central Teton Range is composed almost 

completely of insoluble Precambrian rock, it does not 

contain cave or karst features. However, thick sequences 

of Paleozoic strata north and south of the central range 

contain soluble limestone and dolomite. These rocks—

notably the Madison Limestone, the Death Canyon 

Limestone Member of the Gros Ventre Formation, and 

the Bighorn Dolomite—are known to contain caves. The 

National Park Service has documented 17 caves within

Grand Teton National Park and John D. Rockefeller, Jr. 

Memorial Parkway (Ron Kerbo, NPS Geologic 

Resources Division, Cave Specialist, personal 

communication in Covington and Ransmeier 2005, p. 

10).

Most of the caves south of the crystalline core (uplifted 

Precambrian rocks) are located outside of Grand Teton 

National Park in the Targhee National Forest, but Plantz 

(1978) identified caves in the Death Canyon–Spearhead 

karst area in the southern part of the park. Rendezvous 

Peak Cave, the deepest known cave in Wyoming, is also 

located in this southern limestone area (Hill et al. 1976). 

This vertical cave formed in the Death Canyon 

Limestone Member of the Gros Ventre Formation. 

Plantz (1978) also identified caves in The Wall and 

Moose Basin Divide limestone areas north of the 

crystalline core. 

Most of the caves are small and only Hole-In-The-Wall 

Cave receives significant traffic and requires

management (Plantz 1978). Plantz (1978) found evident

damage to speleothems in the cave that constitutes an 

ongoing management concern.

In addition to cave resources, karst topography and 

associated hydrologic conditions are present to the north 

and south of the central Tetons. Sound and responsible 

infrastructure planning requires awareness of 

groundwater flow patterns and areas susceptible to 

sinkhole formation (Covington and Ransmeier 2005). 

Toomey (2009) suggested 11 “vital signs” and monitoring 

techniques for caves and kart landscapes: cave 

meteorology, airborne sedimentation, direct visitor 

impacts, permanent or seasonal ice, cave drip and pool 

water, microbiology, stability, mineral growth, surface 

expression and processes, groundwater levels and 

quality, and fluvial processes.

Climbing 

The Teton Range has played a pivotal role in the 

development of climbing and mountaineering in the 

United States. Authors have called the region “the home 

of American mountaineering” and “the center of United 

States alpinism,” highlighting its importance in the 

evolution of American climbing (Jones 1976). 

The designation of appropriate climbing equipment for 

use in Grand Teton National Park is currently a matter of 

intense debate. Many climbers believe that the 

installation of permanent hardware (e.g., pitons and 

bolts) along climbing routes compromises the integrity of 

the rock and poses a potential safety risk. Drilling to 

install hardware is not allowed in the park, nor are 

scarring, chiseling, or gluing holds. Included in “good 

climbing practices” at Grand Teton National Park are 

not leaving fixed protection and anchors and pre-trip
12 NPS Geologic Resources Division 

planning of climbs, including review of route 

descriptions to determine the locations of rappels, belay 

stations, and fixed pitons (National Park Service 2010). 

The changing conditions of glaciers and snowfields can 

endanger climbers. While alpine climbers in the park are 

accustomed to planning for daily and seasonal changes in 

snow and ice conditions, glacial retreat due to long-term 

changes in climatic conditions may remove the support 

provided to unconsolidated moraine material and cliff 

walls by glacial ice. These landscape changes could prove 

hazardous to unsuspecting climbers.

Jackson Lake Dam

Jackson Lake is the largest piedmont lake in Jackson 

Hole. In 1906, the Bureau of Reclamation modified the 

natural lake by damming the outlet with a small timber 

crib dam, which failed in 1910. The following year, the 

Bureau of Reclamation replaced the dam with a larger 

structure and associated concrete spillway and earthen 

embankments. Huckleberry Ridge Tuff supports the 

south end of the concrete section, but the long dike to 

the north was built on unconsolidated sediments at least 

180 m (600 ft) thick (Gilbert et al. 1983). 

The Teton Dam, located on the Teton River west of the 

Teton Range, ruptured in 1976. The resulting 

catastrophic flood killed 11 people. This disaster 

prompted the Bureau of Reclamation to evaluate the 

safety of other dams in the area, including the Jackson 

Lake Dam. The ensuing study revealed that the Jackson 

Lake Dam was susceptible to failure during an 

earthquake larger than magnitude-5.5. The upper 30 m 

(100 ft) of glacial fill contains sand beds that are subject 

to liquefaction (Pierce and Good 1992). Hence, between 

1986 and 1989, the Bureau of Reclamation upgraded the 

dam to withstand the maximum credible earthquake, 

which is magnitude-7.5 on the Teton fault (Bureau of 

Reclamation and National Park Service 1984). The 

liquefiable sediments were strengthened by a 

combination of dynamic compaction, achieved by 

repeatedly dropping a 27,000-kg (30-ton) weight from a 

height of 30 m (100 ft), and by in-situ injection and auger 

mixing of cement to form concrete pilings (Pierce and 

Good 1992). Structural improvements to the dam in the 

late 1980s have greatly reduced the possibility of its 

failure (Mott 1998).

Failure of the Jackson Lake Dam would flood a 130-km 

(80-mi) downstream area extending to the Palisades 

Dam. The town of Jackson, situated away from the river, 

would not be flooded. However, flooding would impact 

the area south of town, possibly destroying bridges and 

impeding access to Jackson. Total collapse of the dam 

and reservoir would produce an outflow exceeding 

11,300 m3 (400,000 ft3

) per second, with peak flows 

sustained by the large volume of Jackson Lake (Mott 

1998). The reservoir currently covers approximately 

10,270 ha (25,370 ac) at full pool, and stores more than

1 billion m3 (847,000 ac-ft) of water (Mott 1998). If 

failure occurred during heavy spring runoffs and the 

Palisades Reservoir downstream was nearly full, the 

necessary release of large volumes of water from this 

reservoir could flood agricultural land farther 

downstream, along the Snake River Plain in Idaho (Smith 

and Siegel 2000). Flooding could also cause sediment and 

bacterial contamination of water supply wells (Mott 

1998), and destruction of buildings and floodplain 

vegetation in locations where velocity, depth of flow, and 

debris movement were significant (Glass et al. 1974). 

An earthquake of sufficient magnitude to cause the dam’s 

failure could also produce a seiche on Jackson Lake. The 

resulting 1.8-m- (6-ft-) high waves (Smith and Siegel 

2000) would affect water recreationists and moored 

boats, as well as people and infrastructure in the vicinity 

of the lake.

The primary geomorphic changes of the Snake River 

system due to the impoundment of Jackson Lake are the 

decline in magnitude and frequency of peak flows and 

reduced channel avulsion (Marston 1993). These 

changes occurred after the Palisade Reservoir began

operating in 1957 (fig. 6). The decline in peak flows has 

reduced the Snake River’s ability to transport bedloads.

The river aggrades and avulses in areas of sediment input 

(e.g., near cut banks and tributaries), but does not 

transport sediment from these unstable (more sinuous) 

areas to stable (less sinuous) areas with less avulsion and

lower sediment inputs (Marston 1993; Mott 1998). 

These geomorphic changes have altered the distribution 

and character of riparian resources at Grand Teton 

National Park. Forested vegetation communities, used by 

raptors, have expanded at the expense of willow-alder 

shrub swampland, which constitutes prime habitat for 

moose (Marston 1993). The decline in channel avulsions 

has eliminated numerous side channels that formerly 

served as spawning and rearing habitat for cutthroat 

trout (Marston 1993). 

Paleontological Resources

Tracy (2003) conducted a comprehensive 

paleontological survey of Grand Teton National Park 

that listed 160 species: five trilobites, 71 brachiopods, 28 

gastropods, three cephalopods, three lagomorphs, four

insects, 10 rodents, two artiodactyla, and 34 plants. The

plant species included a cycad-like species, 

gymnosperms, vascular plants with spores, ferns, 

sequoia, deciduous trees, ficus, flowering plants, tropical 

chestnut-like trees, and evergreen trees and shrubs. 

Twenty-eight rock units that occur in the park are 

considered fossiliferous, and many have yielded fossil 

specimens (see Map Unit Properties Table). Tracy (2003) 

inventoried and documented fossil localities in 13 of 

these rock units. 

The oldest fossils discovered in the park are trilobites 

from the Cambrian Period (500 million years ago) and 

the youngest are 9,000-year-old gastropods from the

Holocene. Paleozoic rocks contain the most fossils 

(table 1), and the Mississippian Madison Limestone is 

the most fossiliferous unit in Grand Teton National Park

(Tracy 2003).
GRTE Geologic Resources Inventory Report 13

The 2009 Paleontological Resources Preservation Act 

outlines a science-based management, education, and 

interpretation plan for fossil resources, which are 

nonrenewable. Tracy (2003) identified areas in Grand 

Teton National Park where paleontological resources are 

at high risk because of fossil abundance and ease of 

access. At least one of these areas contained evidence of 

deliberate fossil poaching. Paleontological resource 

monitoring strategies should focus on those areas. The 

sites may also provide opportunities for interpretation 

and education regarding the National Park Service 

resource stewardship mission.

The National Park Service has compiled guidance 

documents to help resource managers manage

paleontological resources (National Park Service 2004). 

Santucci et al. (2009) identified “vital signs” for 

monitoring impacts to paleontological resources: 

geologic and climatic variables affecting natural erosion 

rates, catastrophic geologic processes or geohazards, 

hydrology and bathymetry (i.e., changes in water level 

affecting resources near water bodies), and human 

impacts. Plans to reduce human impacts could include 

locating future development (e.g., trails and 

infrastructure) away from fossil localities and increasing 

the frequency of park-staff presence at these sites. 

Because paleontological localities vary widely, all of these 

processes may not be relevant at each fossil site. 

Figure 2. Teton Fault. The Teton Range rises more than 2,100 m (7,000 ft) above the floor of Jackson Hole. The Teton Range is part of the 

upthrown footwall block of the fault, while Jackson Hole is situated on the downdropped hanging-wall block. Modified from Lillie 

(2005) by Trista Thornberry-Ehrlich (Colorado State University).
14 NPS Geologic Resources Division 

Figure 3. Gros Ventre Slide. The 1925 Gros Ventre slide displaced 38 million cubic meters (50 million cubic yards) of rock 640 m (2,100 ft)

down the side of Sheep Mountain. This slide is just east of the park (see fig. 1). National Park Service photograph by Cooper. Available 

online: http://www.nps.gov/grte/photosmultimedia/photogallery.htm (accessed July 16, 2010).

Figure 4. Gros Ventre Slide Boulders. Large boulders of Tensleep Sandstone are visible near the toe (bottom) of the Gros Ventre slide 

(fig. 3). U.S. Geological Survey photograph. Available online at the 3-D Geology of National Parks website: 

http://3dparks.wr.usgs.gov/grte/index.html (accessed July 16, 2010).
GRTE Geologic Resources Inventory Report 15

Figure 5. Middle Teton Glacier. The present-day glaciers in Grand Teton National Park lie in the shadows of major peaks. National Park 

Service photograph from 2005 by K. Finch. Available online: http://www.nps.gov/grte/photosmultimedia/photogallery.htm (accessed 

July 16, 2010).
16 NPS Geologic Resources Division 

Figure 6. Model of Geomorphic Changes to Snake River System. The primary geomorphic changes to the Snake River system resulting 

from impoundment of Jackson Lake are the decline in magnitude and frequency of peak flows and decreased channel avulsion. These 

geomorphic changes have altered the distribution and character of riparian resources at Grand Teton National Park. Graphic from 

Marston (1993), NPS project no. GRTE-W89-0110.

Table 1. Fossiliferous Paleozoic Strata in Grand Teton National Park

Age Rock Unit Fossils

Permian Phosphoria Formation Marine fossils (e.g., bivalves)

Trace fossils

Mississippian Madison Limestone* Bivalves, brachiopods, crinoids, corals, and gastropods

Ordovician Darby Formation

Bighorn Dolomite

Marine fossils: crinoids, brachiopods, and ostracodes 

Darby Formation also contains stromatolites

Cambrian Gallatin Formation

Gros Vente Formation Trace fossils, trilobites, and bivalves

Source: Tracy (2003). 

*Most fossiliferous unit in Grand Teton National Park

Closing of Palisades Reservoir 

1957

Lower Peak Flows 

from Jackson Lake Dam

Near Tributaries and Cut 

Banks

Fewer Flushing Flows 

and Continued Sediment 

Deposition

Increased Braiding and 

Meandering

Increased Total 

Sinuosity

(Instability)

Away from Tributaries and 

Cut Banks

Fewer Avulsions

Decreased Braiding and 

Meandering

Decreased Total 

Sinuosity

(Stability)
GRTE Geologic Resources Inventory Report 17

Geologic Features and Processes

This section describes the most prominent and distinctive geologic features and processes 

in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway.

Ancient Rocks

Although a number of National Park System units host 

Precambrian (Archean and Proterozoic) rocks, only two 

contain Archean rocks (the oldest rocks on Earth): 

Voyageurs National Park in Minnesota (Graham 2007) 

and Grand Teton National Park. Grand Teton National 

Park thus contains some of the oldest rocks in the 

National Park System. 

Archean rocks are 4 billion to 2.5 billion years old. 

During the Archean Eon, masses of rock called cratons 

formed the initial structures of continents. Today, 

Archean rocks are found in areas such as the Superior 

Upland, including Voyageurs National Park, and the 

Rocky Mountains, including Grand Teton National Park 

(fig. 7). 

The oldest known rocks in the Superior Upland region 

are between 3.7 and 3.5 billion years old (Peterman 

1979). These metamorphic rocks (gneiss) crop out in the 

Minnesota River Valley between New Olm and 

Ortonville, Minnesota (Boerboom 1994). However, the 

oldest rocks yet to be dated in Voyageurs National Park 

are tonalite, which Goldich and Fischer (1986), Davis et 

al. (1982), and Davis et al. (1989) dated as 2,729 million to 

2,695 million years old.

The oldest rocks in Wyoming, located in the Beartooth 

Mountains, are 3.3 billion years old (Peterman 1979).

Frost and Fanning (2006) obtained dates of 3,253 ± 10 

million years old from zircon grains from these gneisses. 

However, the oldest rocks yet dated in Grand Teton 

National Park are the Webb Canyon Gneiss, which 

Zartman and Reed (1998) dated to 2,680 ± 12 million 

years old. 

Both Voyageurs and Grand Teton national parks host 

rocks that are older than those for which dates have been 

obtained. The ages of the rocks predating the Webb 

Canyon Gneiss in Grand Teton National Park and the 

tonalite in Voyageurs National Park, however, remain 

unknown.

Young Mountains

In contrast to the age of its rocks, the Teton Range is

geologically young. The range is the youngest in 

Wyoming and among the youngest of the Rocky 

Mountain ranges. For example, in the vicinity of the 

park, the Washakie, Gros Ventre, and Gallatin ranges 

and the Beartooth Mountains formed 70 million to 50 

million years ago during Laramide mountain building. 

The Snake River Range is another young mountain 

range, although it is older than the Teton Range. Major 

displacement in the Snake River Range occurred during 

the Neogene (23 million to 2.6 million years ago) and 

movement has since ceased (Lageson et al. 1999). By 

contrast, the Teton Range is seismically active and 

continues to rise. Although Laramide uplift did influence 

the Teton Range, its present height was primarily created 

by uplift during the last 5 million years, as a result of 

activation of the Teton fault, which elevated the Tetons 

while dropping Jackson Hole (see “Seismic Activity” 

section). 

A distinctive feature of “young” mountains is their steep 

slopes, sharp ridges, and pointed peaks yet to be muted 

by erosion. This craggy appearance contrasts greatly with 

the mound-shaped peaks, gentle ridges, and gradual 

slopes of “old” mountains. In the case of the Teton 

Range, these sharp features were enhanced by the 

sculpting of alpine glaciers. 

Dikes

Cross-cutting dikes form distinctive lithologic features at 

Grand Teton National Park. It is impossible to miss the 

“ribbonlike black dikes” (Love et al. 2003, p. 9) that 

splice the east face of Middle Teton or the “glittering 

mica-studded dikes” (Love et al. 2003, p. 8) along the 

Cascade Canyon Trail to Hidden Falls and Inspiration 

Point. Perhaps the most impressive dike in the park is 

exposed on the face of Mount Moran (fig. 8). As a result 

of differential erosion, this diabase dike protrudes from 

the surrounding gneiss. In contrast, diabase dikes on the 

Middle Teton are recessed in the surrounding granite. 

Dikes in the park cut across rocks as old as the Webb 

Canyon Gneiss (Archean) and as young as Cody Shale 

(Cretaceous). Tertiary basalt breccia also forms some 

dikes and flows (Love et al. 1992).

Dikes form when magma wells up into fissures in the 

country rock, cutting across the bedding or foliation of 

preexisting rocks. Composed of various types of igneous 

rock, dikes can be diabase, like that on Mount Moran, or 

pegmatite, such as those in Cascade Canyon. 

Geothermal Features 

Geothermal features—primarily hot and warm springs 

and associated pools—are present in Grand Teton 

National Park and John D. Rockefeller, Jr. Memorial 

Parkway. The Jackson Hole area hosts Huckleberry, 

Jackson Lake, Granite, and Astoria hot springs, as well as 

Kelly, Teton Valley Ranch, Abercrombie, and Boyles Hill 

warm springs, North Buffalo Fork Springs, and Camp 

Creek and Driggs wells (Love et al. 2003). Granite and 

Astoria hot springs have been commercially developed, 

and Teton Valley Ranch Warm Springs is privately 

owned. The two geothermal wells were encountered 

during oil and gas exploration. The map by Love et al. 

(1992) identifies “the hottest spring in the hot-springs 

area” on the western shore of Jackson Lake (fig. 9).
18 NPS Geologic Resources Division 

In 2004 the National Park Service conducted an 

inventory that documented 103 geothermal features.

These features were located primarily at Huckleberry 

Hot Springs, but also at Polecat Hot Springs (both in 

John D. Rockefeller, Jr. Memorial Parkway), and at

Jackson Lake Hot Springs, Kelly Warm Springs, and 

Abercrombie Warm Springs in Grand Teton National 

Park (Ann Rodman and Carrie Guiles; Yellowstone 

Center for Resources, Resource Information Exchange;

Supervisory GIS Specialist and Cartographic Technician; 

PowerPoint presentation, 2006). The pH of these 

features varied from 6.5 to 7.9, and the temperature 

varied from 26°C to 67°C (79°F to 153°F). The 

investigators measured electrical conductivity ranging 

from 100 to 2,000 micromhos per centimeter (Ann 

Rodman, Yellowstone National Park, Supervisory GIS 

Specialist, e-mail to Sue Consolo-Murphy, 2005). 

Electrical conductivity is a measure of the concentration 

of dissolved minerals in the water; higher concentrations 

of dissolved materials produce higher electrical 

conductivity. The investigators also documented these

features with digital photography, written descriptions, 

and GPS location data. These data are now part of the 

park’s GIS (Sue Consolo-Murphy, Grand Teton 

National Park, Chief of Science and Resource 

Management, e-mail, October 9, 2009).

Some springs (e.g., Huckleberry Hot Springs) formed 

where groundwater is heated by igneous rock bodies at 

shallow depths, while others (e.g., Kelly Warm Springs) 

are probably heated by the downward movement of 

groundwater along permeable rock layers to depths 

where the increased temperature is sufficient to heat the 

water and cause it to rise toward the surface, possibly 

along faults (Love et al. 2003). Previous studies 

associated the thermal springs on the west side of 

Jackson Lake with the Teton fault (National Park Service 

1986). 

Glacial Features

“The Teton Range is unique and spectacular, not because 

it has been glaciated, for almost all mountains in the 

Rockies have been glaciated, but because of the 

tremendous magnitude of glacial carving” (Lageson and 

Spearing 1988, p. 212). Second only to faulting, glacial 

processes shaped the topography of Grand Teton 

National Park. Glaciation, particularly associated with 

the Pinedale glaciation (30,000 to 12,000 years ago), also 

created the topography and surficial features of the John 

D. Rockefeller, Jr. Memorial Parkway. Glacial ice 

completely covered the parkway during this time. Alpine 

glaciers sculpted the canyons and peaks in the Teton 

Range and larger glaciers flowed south through Jackson 

Hole.

Arêtes, Cirques, and Horns

Mountains that are, or have been, surrounded by glaciers 

tend to exhibit characteristic sharp ridges, craggy spires, 

and basins created by glacial sculpting (fig. 10). Glaciers 

carved canyons on all sides of the mountains in Grand 

Teton National Park, creating the striking glacial horns 

of Grand Teton, Middle Teton, and South Teton. Steep, 

straight ridges, called arêtes, often link horns, for 

example between Grand Teton and Mount Owen (the 

two highest peaks in the park). Arêtes also separate 

glacially gouged valleys. 

Glacial cirques—amphitheater-like hollows eroded into 

a mountain mass—head many valleys in the park. The 

extant small glaciers occupy cirques once excavated by 

their large predecessors. For example, the Teton Glacier 

lies in a cirque at the head of Glacier Gulch, shaded by 

the arêtes of Grand Teton, Mount Owen, and Mount 

Teewinot.

Erratics

In many glaciated areas, large boulders called erratics 

become stranded when glaciers recede. These out-ofplace rocks, some with glacial striations (see “Polish and 

Striations” section), demonstrate the effectiveness of 

glacial erosion and transport. They also exemplify glacial 

deposition, as they are scattered on bedrock surfaces 

different from their own lithologies. During the Bull 

Lake glaciation (160,000–130,000 years ago, and perhaps 

as early as 190,000 years ago), glaciers flowed out of the 

Tetons and joined the huge south-flowing glacier in 

Jackson Hole. The smaller valley glaciers left a train of 

erratics composed of Precambrian crystalline rock along 

the west side of Jackson Hole (Love et al. 2003). 

Hanging Valleys

Few landscape features are more aesthetically beautiful 

than a hanging valley with a cascading waterfall spilling 

over its lip. Before glacial and fluvial sediment began to 

fill Jackson Hole, hanging valleys cut into the Teton 

Range above the main glacial valley of Jackson Hole. 

Today, however, the distribution of such hanging valleys

above main valley floors is restricted to smaller, higherelevation valleys in canyons such as Avalanche and

Garnet. The discordant levels of the valley floors and 

their size differences are due to the greater erosive power 

of the main, trunk glacier. Differential erosion (between 

rock units of differing resistance) also contributed to the

creation of the “stair steps” of Avalanche Canyon (Good 

and Pierce 1996).

Moraines

A glacier carries all sizes of debris at its base, surface, and 

within its body of ice, and deposits this material along its 

sides and snout. “Till” is the general term for the poorly 

sorted mixture of fine to coarse rock debris deposited 

directly from glacial ice. The most obvious landforms 

composed of till are moraines. Moraines can be rounded 

mounds or sharp ridges, depending on the presence of 

surrounding topographic features that may have 

constrained a flowing glacier, the duration of a glacier’s

stability in a particular position, and the amount of

erosion that has taken place since deposition.

An end moraine forms at the lower end of a glacier. A 

terminal moraine is a form of end moraine that extends 

across a glacial valley and marks the farthest advance or 

maximum extent of a glacier. An end moraine commonly 

dams meltwater to create a lake. Such moraines impound 

the piedmont lakes at the base of the Teton Range. 

Jackson Lake was originally impounded by a terminal 
GRTE Geologic Resources Inventory Report 19

moraine, which is now supplemented by a dam 

constructed by the Bureau of Reclamation. The islands in 

Jackson Lake (Elk, Dollar, and Marie islands, and 

Donoho Point) are composed of debris of the Jackson 

Lake moraine (Love et al. 1992). 

Lateral moraines form along the sides of glaciers and 

merge with an end moraine. Notable lateral moraines in 

the park occur along Buffalo Fork. Recessional moraines 

are end or lateral moraines formed during a temporary 

but significant pause in the final retreat of a glacier. Such 

moraines extend across the floor of Jackson Hole south 

of Jackson Lake (Love et al. 1992).

Outwash and Kettles

Meltwater “washes out” sediment from a glacier and 

deposits the material in a flat area in front of the glacier’s 

snout. Glacial outwash covers Antelope and Baseline 

flats. In some areas of the park, outwash material is so 

thick (60 m [200 ft]) that it obscures the underlying 

deposits of previous glaciations (Elias 1996). 

Depressions called kettles commonly pockmark outwash 

plains, such as in the Potholes area of the park. Kettles 

form when a block of stagnant ice becomes wholly or 

partially buried in outwash and ultimately melts, leaving 

behind a pit. Kettles can be a few or hundreds of feet 

long, but are generally wider or longer than they are 

deep. In many cases, water eventually fills the depression 

and forms a kettle pond or lake. Hedrick Pond, for which 

the middle advance of the Pinedale glacial phase was 

named, is a kettle lake (Pierce and Good 1992). Cow 

Lake, part of the hummocky pothole terrain seen from 

Jackson Point Overlook on Signal Mountain (Smith and 

Siegel 2000), is another example of a kettle lake. 

Polish and Striations

Rocks and sediment adhering to the base and sides of 

glaciers act like sandpaper, scratching and smoothing the 

rock surfaces over which they pass. Though small in 

scale, glacial polish exemplifies glaciation in Grand 

Teton National Park. Striations are multiple, generally 

parallel, scratches inscribed on a rock surface that mark a 

glacier’s flow path. Both smoothly polished and 

scratched rock faces below Inspiration Point identify

glacial ice as shaping this landscape. 

U-shaped Valleys

Stream-cut valleys are typically V-shaped prior to the 

appearance of glaciers. A glacier’s movement down a 

valley straightens and widens it into a U shape. 

Avalanche, Garnet, Cascade, and Paintbrush canyons are 

classic examples of U-shaped glacial valleys. When 

glaciers retreat, the bottoms of U-shaped valleys 

commonly become flat, as they are filled by sediment 

deposited in lakes impounded by the terminal moraines.

Lakes

More than 100 lakes are nestled in the alpine area of

Grand Teton National Park. These lakes range in size 

from 0.4 ha to 24 ha (1 ac to 60 ac) and occur primarily 

above 2,700 m (9,000 ft) of elevation (Mott 1998). 

The piedmont (“foot-of-the-mountain”) lakes of 

Jackson, Leigh, String, Jenny, Bradley, Taggart, and 

Phelps comprise the majority of surface water at Grand 

Teton National Park (Mott 1998). The largest of these,

Jackson Lake, originally covered about 6,920 ha

(17,100 ac) (National Park Service 1986). Jackson Lake 

Dam has expanded the lake to 10,336 ha (25,540 ac) at 

full pool (Mott 1998) (see “Jackson Lake Dam” section). 

Additionally, approximately 75 kettle ponds of less than 

0.2 ha (0.5 ac) to more than 14 ha (35 ac) punctuate the 

glacial drift south and east of Jackson Lake (Mott 1998).

Glacial processes during the three phases of Pinedale-age

glaciation created these lakes and ponds. The trough 

along the front of the Teton Range, which formed during 

Miocene activation of the Teton fault, initiated the 

formation of the deep Jackson Lake basin. An ancestral 

Jackson Lake may have existed during the Miocene 

(Smith and Siegel 2000). A combination of faulting and 

glacial scouring created the deepest part of Jackson Lake 

(i.e., the western trough), which is 133 m (437 ft) deep. 

The shallowest eastern trough, which is 43 m (142 ft) 

deep, was primarily carved by glaciers (Smith et al. 1993; 

Smith and Siegel 2000). 

Loess

Loess (windblown dust) commonly forms when winds 

blow across exposed outwash deposits. The geologic 

map of Grand Teton National Park shows notable loess 

deposits on Timbered Island and between Phelps and 

Taggart lakes (Appendix A) (Love et al. 1992). Loess 

deposits near the Snake River are thicker than 3 m (10 ft) 

(Glenn et al. 1983), and those on the high terraces south 

of Jackson reach 6 m (20 ft) in thickness (Good and 

Pierce 1996).

Although loess is underrepresented on most geologic 

maps, investigators of Quaternary climate change have 

renewed scientific interest in this sediment type (Madole 

1995). Thick loess sequences contain detailed records of 

Quaternary glacial-interglacial cycles. Like the 

foraminiferal oxygen isotope record of deep-sea 

sediments, these loess deposits document long-term 

climate change (Muhs et al. 1999). Loess is also a direct 

record of atmospheric circulation, supplying paleowind 

data that researchers can use to test atmospheric general 

circulation models (Muhs et al. 1999). In addition, 

widespread eolian deposits are important sources of 

information for reconstructing the history of 

aridification in the interior of North America during the 

Quaternary (Madole 1995).

Soil development, mapped moraine sequences, and loess 

data allowed investigators to correlate local Munger 

glaciation deposits with the regional Bull Lake glaciation

(Pierce and Good 1992). In Grand Teton National Park, 

these deposits are characterized by a well-developed soil 

that is commonly buried by loess of the Pinedale 

glaciation (Pierce and Good 1992).
20 NPS Geologic Resources Division 

Oxbows

The influence of the Teton fault on the Snake River 

system is illustrated by the unusually deep water (5 m

[15 ft]) at Oxbow Bend. “This deep, tranquil stretch of 

the Snake River may result from backtilting on the Teton 

fault, elevating the bedrock threshold just downstream 

from where Pacific Creek joins the Snake River” (Pierce 

and Good 1992, p. 38) With the exception of depth, the 

oxbows at this location are classic examples of this 

geomorphic form. As the river migrates across the 

floodplain, it creates closely looping stream meanders. 

The piece of land left between the two endpoints of the 

meander is the “ox’s neck.” Eventually, the stream will 

cut across the narrow neck, abandoning the meander 

and creating an oxbow lake. An abandoned oxbow thus 

marks a former course of the river.

Terraces

The gravel terraces along the Snake River are among the 

most striking geomorphic features in Grand Teton 

National Park. These ancient floodplains flank the Snake 

River as it flows south through Jackson Hole, rising 43 m 

(140 ft) on either side of the river (figs.11 and 12). 

Terraces are evidence of the dynamic nature of the Snake 

River over thousands of years and reflect the active 

history of glaciation and tectonic movement in Jackson 

Hole (Marston 1993). During glacial advances, excessive

debris in meltwater streams leads to rapid aggradation of

their beds through thick accumulations of sand and 

gravel. When glaciers retreat, streams swollen with 

meltwater cut trenches into the accumulated outwash, 

thereby deepening their channels and producing 

terraces. Terrace tops are therefore built during glacial 

advances, and terrace faces are cut during glacial retreat 

(Harris and Tuttle 1990). Paired terraces on opposite 

sides of the stream channel represent the same former 

floodplain. Unpaired terraces indicate the erosional 

removal or depositional burial of the terrace on one side 

of the valley. Tectonics may also disturb terrace forms. 

Love et al. (1992) mapped the terraces in Grand Teton 

National Park as terrace gravel (Qtg) and outwash gravel 

forming terraces graded to the Burned Ridge (Qo4b) and 

Jackson Lake moraines (Qo4j). Notable examples of 

these deposits comprise Baseline and Antelope flats; 

older terrace gravel (Qtg) underlies Jackson Hole 

Airport. 

Marston (1993) constructed 11 topographic profiles 

across the Snake River between Deadmans Bar and 

Moose to identify the relative ages of the terraces. The 

exercise tentatively identified 10 terrace levels based on 

relative position below the uppermost geomorphic 

surface, which corresponds to the end of Pinedale 

glaciation. Each level represents a period of river 

incision, which can be triggered by a drop in river base 

level or a change in climate that shifts the balance 

between water and sediment discharge. 

Unconformities

Unconformities are gaps in the rock record. The absence 

of rocks of a certain age in a stratigraphic sequence 

represents a time during which sediment was not 

deposited or was subsequently eroded. The stratigraphic 

record in Grand Teton National Park is very 

comprehensive, representing all but one major divisions 

of geologic time from the Archean to the present. The 

Silurian Period is not represented. 

The most notable unconformity in the park is between 

the Precambrian and the Middle Cambrian; this surface 

represents 2.2 billion years. Other unconformities cover 

the Lower Ordovician (488 million to 471 million years 

ago), the entire Silurian Period (443 million to 416 

million years ago), the Lower and Middle Devonian (416

million to 385 million years ago), the Middle 

Mississippian (345 million to 328 million years ago), the 

Middle Triassic (245 million to 228 million years ago), 

and the Lower Jurassic (199 million to 175 million years 

ago). These gaps represent half of all geologic time, most 

represented by the unconformity between the 

Precambrian rocks and the Middle Cambrian Flathead 

Sandstone. 

Volcanic Features

The volcanic features at the park and parkway can be 

divided into four groups. From oldest to youngest, these 

rocks are related to Absaroka volcanism, Basin and 

Range extension, the Heise volcanic field, and the 

Yellowstone hot spot.

Absaroka Volcanics

The present Absaroka volcanic province is an erosional 

remnant of the largest Eocene (55 million to 33 million 

years ago) volcanic field in the northern Rocky 

Mountains, which covered 23,300 km2 (9,000 mi2

). The 

rocks within this province belong to the Absaroka 

Volcanic Supergroup, including the Langford, Hominy 

Peak, and Wiggins formations in the park and parkway. 

The Wiggins Formation is the youngest deposit in the 

sequence. 

Today, the Absaroka Range is a rugged, northwesttrending mountain range to the northeast of the park and 

parkway. The inferred depositional setting was a belt of 

large andesitic stratovolcanoes flanked by coalescing 

alluvial fans (Sundell 1993). Zones of Precambrian 

structural weakness that were reactivated during the 

Laramide Orogeny (~70 million to 50 million years ago) 

likely formed two belts of Absaroka volcanic eruptive 

centers (Sundell 1993). These volcanoes produced highly 

explosive eruptions that triggered numerous mudflows, 

called lahars. In addition to mass wasting, fluvial and 

eolian processes rapidly and continuously reworked and 

mixed the volcanic material.

Basin and Range Extension

The Colter Formation is a unit of volcanic transition 

between Absaroka and Basin and Range volcanism. This 

unit contains recycled fragments of Absaroka volcanic 

rocks but also represents the beginning of Basin and 

Range extension, which expanded the western United 

States by 50% to 100% in the past 15 million years. The 

Teton Range lies at the eastern edge of the Basin and 

Range province, while the province’s western edge is in 
GRTE Geologic Resources Inventory Report 21

California. Like the Tetons, mountain ranges within the 

province are typically bounded by normal faults.

As a result of extension, volcanic vents (now buried 

beneath younger deposits) produced the Colter 

Formation, which is composed of tuff, basalt, volcanic 

conglomerate, mafic andesite, and some rhyolitic welded 

tuff, as well as other rocks such as pumice breccia, flow 

breccia, scoria, and some flows and intrusive masses of 

andesite (Love et al. 1992). The vents seem to have 

initially produced andesitic rocks, then rhyolitic and 

basaltic compositions as Basin and Range extension 

became dominant. These vents were likely located along 

zones of weakness; one of these zones became the locus 

of the Teton fault (Love et al. 2003).

Heise Volcanic Field

The Heise volcanic field, now buried beneath the Snake 

River Plain, is the precursor to the present-day 

Yellowstone Plateau volcanic field. It was actively 

erupting 5 million years ago. The framework of the field 

is composed of four rhyolitic ignimbrites formed by ash 

flows and nuées ardentes. The two youngest ignimbrites 

occur in the park and parkway: the Conant Creek Tuff is 

visible at the northern end of the Teton Range and in 

Jackson Hole, and the Kilgore Tuff is exposed on Signal 

Mountain and in the Gros Ventre Range (Morgan and 

McIntosh 2005). Most of the Conant Creek Tuff mapped 

by Love et al. (1992) is actually a distal facies of the 4.45-

million-year-old Kilgore Tuff (Morgan and McIntosh 

2005).

Both of these eruptions/rock units help to determine the 

timing of tectonic events in the Grand Teton–

Yellowstone region. The 5.5-million-year-old Conant 

Creek Tuff includes massive slide blocks that could not 

have formed or flowed without significant relief, 

indicating that the Snake River Plain was characterized 

by such relief at that time. These landslides were 

probably seismically triggered and flowed 

catastrophically. The southward flow of the Kilgore Tuff 

was unrestricted, indicating that the Teton Range was 

not a significant topographic feature before 4.45 million 

years ago.

Yellowstone Hot Spot

Like the earlier Heise volcanic field, the Yellowstone hot 

spot was formed by continental crust overriding a plume 

of rising mantle material. This hot spot is atypically 

located in the interior of a continental plate, distant from 

ocean ridges, volcanic arcs, and other expressions of 

dynamic plate boundaries. As the North American plate 

moved southwestward over this stationary plume, 

massive amounts of volcanic rock were deposited at the 

surface. The plate’s course is marked by a track of lava 

(Eastern Snake River Plain) from southeastern Oregon 

and northeastern Nevada to the plume’s present-day 

location under Yellowstone National Park. The hot spot 

first surfaced 16 million years ago, and is likely linked to 

the extraordinary eruptions of basaltic lava that 

blanketed much of northern Oregon and southern 

Washington. Craters of the Moon National Monument 

and Preserve in Idaho interprets volcanism along the 

Snake River Plain.

In Grand Teton National Park and John D. Rockefeller, 

Jr. Memorial Parkway, three rock units and a portion of a 

fourth owe their origins to the Yellowstone hot spot. The 

2.05-million-year-old Huckleberry Ridge Tuff 

documents the first major hot spot–related event in the 

park and parkway. This tuff was probably deposited 

during a single eruption (Love et al. 2003). Lewis Canyon 

Rhyolite (900,000 years ago) and Lava Creek Tuff 

(630,000 years ago) mark more recent eruptions. In 

addition, the final sedimentary layer of Lake Teewinot 

(Teewinot Formation) was ash associated with hot-spot 

activity.
22 NPS Geologic Resources Division 

Figure 7. Archean Rocks of North America. The Superior Upland and Rocky Mountains host some of the oldest rocks on Earth. Grand Teton 

National Park (star) hosts Archean rocks, some of the oldest in the National Park System. Archean rocks span from 4.0 billion to 2.5 billion 

years ago. U.S. Geological Survey graphic from the North American Tapestry of Time and Terrain website: 

http://nationalatlas.gov/articles/geology/legend/ages/archean.html (accessed February 22, 2010).

Figure 8. Diabase Dike on Mount Moran. The distinct black feature on the peak of Mt. Moran is a diabase dike (arrow). This previously molten 

material was injected into cracks of the Archean rocks that form the mountain. The dike is about 46 m (150 ft) wide and cross-cuts the Teton 

Range for about 16 km (10 mi). U.S. Geological Survey photograph, available online at the 3-D Geology of National Parks website: 

http://3dparks.wr.usgs.gov/grte/index.html (accessed July 16, 2010).
GRTE Geologic Resources Inventory Report 23

Figure 9. Jackson Lake Hot Springs. A 2004 survey of the springs obtained pH readings of 6.5 to 7.2 and temperatures ranging from 22°C to

61°C (72°F to 142°F). National Park Service photograph.

Figure 10. Glacially Carved Landscape. During the Pleistocene Epoch, valley glaciers carved horns, arêtes, cirques, and U-shaped valleys in the 

Teton Range. National Park Service photograph.

Arête

Horn

Cirque
24 NPS Geologic Resources Division 

Figure 11. Snake River Terraces. Representing past floodplains, terraces flank both sides of the present-day, actively migrating Snake River in 

Grand Teton National Park. The green star marks the location of the Snake River Overlook (fig. 12). Graphic compiled by Jason Kenworthy 

(NPS Geologic Resources Division) from ESRI ArcImage Service, World Shaded Relief Imagery.
GRTE Geologic Resources Inventory Report 25

Figure 12. Snake River Overlook. Terraces are plainly visible in this view from the Snake River Overlook (green star on fig. 11). National Park 

Service photograph, available online: http://www.nps.gov/grte/photosmultimedia/photogallery.htm (accessed July 16, 2010).

Snake River Terraces
26 NPS Geologic Resources Division 

Map Unit Properties

This section identifies characteristics of map units that appear on the Geologic Resources 

Inventory digital geologic map of Grand Teton National Park and John D. Rockefeller, 

Jr. Memorial Parkway. The accompanying table is highly generalized and for 

background purposes only. Ground-disturbing activities should not be permitted or 

denied on the basis of information in this table. 

Geologic maps facilitate an understanding of Earth, its 

processes, and the geologic history responsible for its 

formation. Hence, the geologic map for Grand Teton 

National Park and John D. Rockefeller, Jr. Memorial 

Parkway provided information for the “Geologic Issues,” 

“Geologic Features and Processes,” and “Geologic 

History” sections of this report. Geologic maps are twodimensional representations of complex threedimensional relationships; their color coding illustrates

the distribution of rocks and unconsolidated deposits. 

Bold lines that cross or separate the color patterns mark 

structures such as faults and folds. Point symbols 

indicate features such as dipping strata, sample localities, 

mines, wells, and cave openings. 

Incorporation of geologic data into a Geographic 

Information System (GIS) increases the usefulness of 

geologic maps by revealing the spatial relationships 

among geologic features, other natural resources, and 

anthropogenic features. Geologic maps are indicators of 

water resources because they show which rock units are 

potential aquifers and are useful for finding seeps and 

springs. Geologic maps are not soil maps, and do not 

show soil types, but they do show parent material—a key 

factor in soil formation. Furthermore, resource managers 

have used geologic maps to make connections between 

geology and biology; for instance, geologic maps have 

served as tools for locating sensitive, threatened, and 

endangered plant species, which may prefer a particular 

rock unit. 

Although geologic maps do not show where earthquakes 

will occur, the presence of a fault indicates past 

movement and possible future seismic activity. Similarly, 

map units show areas that have been susceptible to 

hazards such as landslides, rockfalls, and volcanic 

eruptions. Geologic maps do not show archaeological or 

cultural resources, but past peoples may have inhabited 

or been influenced by depicted geomorphic features. For

example, alluvial terraces may have been preferred use 

areas and formerly inhabited alcoves may occur at the 

contact between two rock units.

The GRI digital geologic maps reproduce essential 

elements of the source maps including the unit 

descriptions, legend, map notes, graphics, and report. 

The following references provided the source data for 

the GRI digital geologic maps for Grand Teton National 

Park and John D. Rockefeller, Jr. Memorial Parkway: 

Christiansen, R. L., H. R. Blank, J. D. Love, and J. C. 

Reed. 1978. Geologic map of the Grassy Lake 

Reservoir quadrangle, Yellowstone National Park and 

vicinity, Wyoming (scale 1:62,500). Geologic 

Quadrangle Map GQ-1459. U.S. Geological Survey, 

Reston, Virginia, USA. 

Love, J. D. 2003. Digital geologic map of the Huckleberry 

Mountain quadrangle, Yellowstone National Park and 

vicinity, Wyoming (scale 1:62,500). Unpublished data. 

U.S. Geological Survey, Reston, Virginia, USA. 

Love, J. D., J. C. Reed Jr., and A. C. Christiansen. 1992. 

Geologic map of Grand Teton National Park, Teton 

County, Wyoming (scale 1:62,500). Miscellaneous 

Investigations Series Map I-2031. U.S. Geological 

Survey, Reston, Virginia, USA.

U.S. Geological Survey. 2007a. Digital geologic map of 

the Grassy Lake Reservoir quadrangle, Yellowstone 

National Park and vicinity, Wyoming (scale 1:62,500). 

U.S. Geological Survey, Reston, Virginia, USA.

The GRI team implements a geology–GIS data model 

that standardizes map deliverables. This data model 

dictates GIS data structure including data layer 

architecture, feature attribution, and data relationships 

within ESRI ArcGIS software, increasing the overall 

utility of the data. GRI digital geologic map products 

include data in ESRI personal geodatabase, shapefile, 

and coverage GIS formats, layer files with feature 

symbology, Federal Geographic Data Committee 

(FGDC)–compliant metadata, a Windows HelpFile that 

contains all of the ancillary map information and 

graphics, and an ESRI ArcMap file that easily displays the 

map. These data are included on the attached CD and 

available through the NPS Data Store at 

http://science.nature.nps.gov/nrdata/. Data will be 

available on the Natural Resource Information Portal 

when the portal goes online. As of September 2010, 

access is limited to NPS computers at 

http://nrinfo/Home.mvc.

The geologic units listed in the following table 

correspond to the accompanying digital geologic data. 

Map units are listed in the table from youngest to oldest. 

Please refer to the geologic timescale (fig. 13) for the age 

associated with each time period. In 2009, the 

International Commission on Stratigraphy updated the 

international stratigraphic chart, which included an 

expansion of the length of time covered by the 

Quaternary Period; therefore, several units listed as 
GRTE Geologic Resources Inventory Report 27

Pliocene on Love et al. (1992) now fall within the 

boundary of the Quaternary (starting 2.588 million years 

ago); these units are Huckleberry Ridge Tuff (Th), 

drift(?) probably related to glaciation 1 (Tg1), and

Shooting Iron Formation (Tsi). Similarly the Tertiary 

Period nomenclature was replaced by Paleogene and 

Neogene periods. Hence, the Tertiary is now considered 

an informal time unit (fig. 13).

The following table highlights characteristics of map 

units in the park and parkway, including susceptibility to 

erosion and hazards; the occurrence of paleontological 

resources (fossils), cultural resources, mineral resources, 

and caves or karst; and use as habitat or for recreation. 

Some information on the table is conjectural but serves 

as suggestions for further investigation. Santucci and 

Wall (1998) and Tracy (2003) provided information 

about paleontological resources. Antweiler et al. (1989) 

yielded information regarding mineral resources. Young 

(1982) provided information about suitability for 

recreation and infrastructure.
28 NPS Geologic Resources Division 

Figure 13. Geologic Timescale. Included are major life history and tectonic events occurring on the North American continent. Red lines 

indicate major unconformities between eras. Isotopic ages shown are in millions of years (Ma). Compass directions in parentheses indicate 

the regional location of individual geologic events. Adapted from the U.S. Geological Survey, http://pubs.usgs.gov/fs/2007/3015/, with 

additional information from the International Commission on Stratigraphy, http://www.stratigraphy.org/view.php?id=25.
GRTE Geologic Resources Inventory Report 29

Map Unit Properties Table: Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway

Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

QUATERNARY

Alluvium, gravel and sand, and 

floodplain deposits (Qa)

Alluvium—Gravel, sand, silt, and clay along modern streams. In places includes alluvial fan, glacial outwash, and 

stream-laid ice-contact deposits. In forest-covered areas may include other types of surficial deposits.

Gravel and sand—Along and adjacent to active channelways of major streams. Composed chiefly of quartzite 

roundstones.

Floodplain deposits—Sand and gravel overlain by silt and clay in low terraces. 

Groundwater aquifer. Inundated 

during modern floods Unknown Placer gold. Sand and gravel.

Swamp deposits (Qs) Dark-gray and brown clay, silt, and fine sand. Rich in debris. Wetlands Carbonized wood None known

Lacustrine and related deposits (Qla) Thinly laminated white marl, ash, and clay. May have accumulated in kettles. Dated at 8,800 and 9,580 years old. Unknown Gastropods None known

Travertine (Qtr) Gray limestone Spring deposits Unknown None known

Colluvium (Qc) Silt to boulder-sized rocks derived from underlying and adjacent units. Locally includes glacial drift. Unstable Unknown None known

Alluvial-fan deposits (Qf)

Crudely stratified deposits of boulders, gravel, sand, silt, and clay, generally coarse at apices and fine at distal margins.

Commonly gradational into talus in mountain areas. Along Spread Creek includes fan deposits composed of white ash, 

silt, clay, and sand derived largely from Colter (Tc) and Teewinot (Tte) formations.

Often-unstable fluvial deposits Unknown Sand and gravel

Alluvium of modern channels and 

floodplains (Qal) Alluvium of modern channels and floodplains (no additional description given in source map) Inundated during modern floods Unknown Sand and gravel

Talus and related deposits (Qt) Coarse, angular, poorly sorted rock debris in talus slopes, talus fans, rock glaciers, and moraines of Holocene glaciers Mass-wasting hazard. Habitat for 

pikas. Unknown None known

Alluvium and glaciofluvial deposits 

(Qag)

Alluvium and glaciofluvial deposits (no additional description given in source map). Glaciofluvial deposits associated 

with meltwater streams from glacial ice. Often-unstable fluvial deposits Unknown Sand and gravel

Landslide debris (Qls)

Chaotically mixed boulders and finer rock debris:

Unit 1 (Qls1)—Locally active (Holocene)

Unit 2 (Qls2)—Stabilized, overgrown with vegetation, unmodified topography (Holocene and Pleistocene)

Unit 3 (Qls3)—Stabilized, overgrown with vegetation, subdued topography (Pleistocene)

Mass-wasting hazard Unknown None known

Talus, colluviums, and avalanche 

deposits (Qtca)

Locally derived coarse angular rock fragments that accumulate on steep slopes and at the base of cliffs; slope wash of 

silt- to boulder sized fragments derived from underlying and adjacent formations. Mass-wasting hazard Unknown None known

Ice-contact deposits localized by hot 

springs (Qhi) Ice-contact deposits localized by hot springs (no additional description given in source map) Not suitable for infrastructure Unknown Unknown

Siliceous hot spring deposits (Qhs) Siliceous hot spring deposits (no additional description given in source map) Not suitable for infrastructure Unknown Silicate minerals

Landslide and glacial debris, intermixed 

or undivided (Qlg) Mixed boulders and finer rock debris of gravity-driven and glacial origins Mass-wasting hazard Unknown None known

Loess (Ql) Light-gray, homogenous, wind-deposited silt, without sedimentary structures. Dated at 13,000 and 19,000 years old. Not suitable for infrastructure Unknown None known

Loess and boulders (Qlb)

Chiefly on higher hills in National Elk Refuge between Flat Creek and Gros Ventre River. Chalky-white, formless 

unstratified, deposits consisting of glacial erratics of many sizes and compositions. Derived from till of glaciation 2 and 

embedded in matrix of white calcareous loess.

Loess not suitable for infrastructure Unknown None known

Leidy Formation (Qly)

Intertonguing lacustrine, fluvial, and glacial deposits. Chiefly very fine-grained, chocolate-brown, pink, and gray clay, 

laminated in part, interbedded with unlithified gray sand. Lenticular quartzite pebble gravels. Basal quartzite boulder 

conglomerate in some places. Intertongues laterally with drift and outwash deposits of glaciation 2 (Qg2). Normal 

polarity and lack of volcanic debris indicate age younger than about 750,000 years. Thickness <137 m (450 ft).

Used for wildlife habitat and 

recreation Unknown None known
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 30

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

QUATERNARY

Drift (Qg4)

Debris of the Jackson Lake moraine 

(Qg4j)

Debris of the Burned Ridge moraine 

(Qg4b)

Deposits related to glaciation 4

Qg4—On west side of Jackson Hole composed mostly of Precambrian rocks from Teton Range. On southeast side 

consists of a wide variety of rocks derived from the north and east. Locally may include older glacial deposits on lower 

eastern slopes of Teton Range. Displays little or no soil development. Topography generally characterized by steepsided moraine ridges and small closed depressions.

Qg4j—South and east of Jackson Lake. Originates from Teton Range and Yellowstone National Park.

Qg4b—Slightly older than debris of the Jackson Lake moraine (Qg4j), although recessional deposits may be the same 

age. Extends across the floor of Jackson Hole south of Jackson Lake. Northeastern and eastern source contributed 

finer debris that resulted in more subdued topography than that of the Jackson Lake moraine.

Supports abundant coniferous trees 

except in eastern part of Jackson 

Hole, where debris contains more 

quartzite and shale and supports 

fewer trees. Used for wildlife habitat 

and recreation.

Unknown None known

Outwash gravel forming terraces graded 

to Jackson Lake moraine (Qo4j)

Outwash gravel forming terraces graded 

to Burned Ridge moraine (Qo4b)

Deposits related to glaciation 4

In related outwash terraces and local depressions within moraines of glaciation 4. Outwash plains and terraces display 

numerous braided channel scars left by meltwater streams. 

Qo4j—East of Snake River Overlook, also includes gray sand and white, brown, pink, and gray silt <15 m (50 ft) thick in 

local depressions. May be ice-margin deposits.

Qo4b—Slightly older than debris of the Jackson Lake moraine (Qg4j), although recessional deposits may be the same 

age. Extends across the floor of Jackson Hole south of Jackson Lake. Northeastern and eastern source contributed 

finer debris that resulted in more subdued topography than that of the Jackson Lake moraine.

Generally not forested. Used for 

wildlife habitat and recreation. Unknown Gravel

Terrace gravel (Qtg) Deposit related to glaciation 4

Outwash gravel composed predominantly of quartzite roundstones. Deposited by glacial meltwater.

Used for wildlife habitat and 

recreation Unknown Gravel

Drift (Qg3)

Deposit related to glaciation 3

Till containing moderately weathered granite erratics and capped by loess in many places. Contains some rocks from 

northeastern part of Jackson Hole. Subdued topography.

Used for wildlife habitat and 

recreation. Capped by loess 

(unstable).

Unknown None known

Outwash gravel (Qo3)

Deposit related to glaciation 3

Crudely stratified gravel composed chiefly of quartzite roundstones. Top characteristically planar and commonly 

capped by loess resting on a buried soil.

Used for wildlife habitat and 

recreation. Capped by loess 

(unstable).

Unknown Gravel

Drift and outwash deposits (Qg2)

Deposit related to glaciation 2

Till containing large and small erratics, in places mixed with outwash gravel, sand, silt, and colluvial debris. Most 

erratics are not locally derived. Soil development is extensive in some places and erratics of Paleozoic sedimentary and 

Tertiary volcanic rocks are deeply weathered. Lacks topographic expression and commonly recognized only as lag 

deposits. 

Generally does not support 

coniferous trees. Used for wildlife 

habitat and recreation.

Unknown Sand and gravel

Plateau Rhyolite, Central Plateau 

member, Pitchstone Plateau flow 

(Qpcp)

Large rhyolite lava flow, variety of lithologies. Most exposures are dark pitchstone or obsidian vitrophyre of rhyolite. 

Gray to red pumiceous rhyolite and gray, brown, or varicolored crystalline rhyolite are also common. All flows contain 

abundant phenocrysts of quartz, sanidine, opaque oxides and, in glassy zones, sparse clinopyroxene and fayatlitic 

olivine. Youngest lava flow associated with Yellowstone, about 72,000 years old. 

Plateau Rhyolite members 

extensively mapped throughout 

central Yellowstone National Park.

Unknown Obsidian, quartz, sanidine, opaque 

oxides, clinopyroxene, olivine

Lava Creek Tuff, member B 

(Yellowstone Group) (Qlab) Gray to brown dense hard-welded rhyolite ash flows. 630,000 years old. Thickness ≥30 m (100 ft). Erosion control likely needed Unknown None known

Lewis Canyon Rhyolite (Qlc) Crystal-rich flows, locally glassy, containing phenocrysts of quartz, plagioclase, sanidine, and clinopyroxene. 900,000 

years old. Thickness ≥183 m (600 ft). Erosion control likely needed Unknown Quartz, plagioclase, sanidine, and clinopyroxene

Obsidian sandstone, siltstone and 

claystone (Qslt) Obsidian sandstone, siltstone and claystone (no additional description given in source map) Erosion control likely needed Unknown Obsidian
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 31

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

TERTIARY–QUATERNARY

Red and gray sequences of clay, silt, 

sand, conglomerate, till, and (or) loess 

(QTs)

Red sequence—Lacustrine(?) and fluvial clay, silt, sand, and conglomerate similar to Shooting Iron Formation (Tsi).

Conglomerate is chiefly of Tertiary rhyolite and Precambrian rocks. Unconformably overlies gray sequence. Thickness 

≥6 m (20 ft).

Gray sequence—Lacustrine(?), fluvial, and glacial silt, till, loess, and clay of uncertain correlation. Numerous striated 

quartzite boulders and andesite clasts. Lack of rhyolite clasts suggests that deposit may be older than Huckleberry 

Ridge Tuff (Th). Thickness ≥9 m (30 ft).

Loess and clay typically not suitable 

for infrastructure Unknown None known

Conglomerate (QTc) Partly lithified conglomerate consisting of gray limestone clasts but also containing sparse clasts of Precambrian rocks 

from unknown source. May be related to later phases of glaciation 1 (Tg1). Thickness <122 m (400 ft). Unknown Unknown None known

Glacial drift (QTgd)

In northern and northeastern part: Ice that moved south from the Yellowstone National Park area or east from the 

Teton Range deposited drift

In eastern part: Westward-moving ice deposited drift. Most drift has more subdued topography and is probably older 

than drift of glaciation 4 (Qg4); some may be as old as drift(?) of glaciation 1 (Tg1).

Used for wildlife habitat and 

recreation Unknown None known

TERTIARY

(MIOCENE)

Andesite and basalt (Tab)

Gray dense porphyritic andesite flows containing hypersthene phenocrysts. Several thin, gray basalt flows north of 

Teton Pass. Rhyolite and black obsidian nodules at base of unit on the Teton Pass mountains. 8.1 million years old. 

Thickness <244 m (800 ft).

Basalt prone to rockfall on steep 

slopes Unknown Obsidian

Rhyolite (Tr) Large intrusive body southwest of Wilson. Light-gray to tan, fine-grained, phenocryst-rich. Includes several intrusions 

of black, glassy, translucent obsidian. 8.06 million years old. Erosion control likely needed Unknown Obsidian

Obsidian pipes (To) Black to gray glassy translucent obsidian. South and southeast of Teton Pass. 8.48 million years old. Unknown Unknown Obsidian

TERTIARY

Dacite flows/Intrusive dacite(?) (Td)

East and northeast of Jackson Hole (Pliocene): Medium- to dark-gray fine-grained dense dacite. Trachytic texture.

East and West Gros Ventre buttes (Eocene): Dark-gray coarse-grained porphyritic dacite(?). Contains abundant 

hornblende and fragments of Late Archean amphibolites.

Unknown Unknown None known

Conglomerate containing no volcanic

material (Tcgn)

Boulders of Tensleep Sandstone and Phosphoria Formation and smaller clasts of Chugwater, Madison, and Gallatin 

formations. Underlies volcanic rocks north of Teton Pass. Eocene age? Thickness <15 m (50 ft). Likely suitable for infrastructure Unknown None known

Andesite (Ta) Pink, brown, and black coarsely porphyritic andesite. Chiefly flows and intrusive masses. Thickness ≥30 m (100 ft). Unknown Unknown None known

Perlite (Tp) Dark-gray granular soft perlite. Contains abundant obsidian fragments. Thickness ≥30 m (100 ft). Forms soft substrate Unknown Perlite and obsidian

Felsite porphyry (Tfp) Light-gray intrusive felsite porphyry Unknown Unknown None known

Scoria (Ts) Lightweight frothy black rock containing masses of dark-green glass and gray pumiceous rock. Thickness ~3 m (10 ft). Highly vesicular and thin walled Unknown None known

Flow-breccia and pumice (Tbxp)

At top, red dense lava flow <61 m (200 ft) thick, underlain by 15–30 m (50–100 ft) of red flow-breccia and pumice. 

Locally, at base, 30 m (100 ft) of ribbon-laminated red and gray hard densely welded tuff containing angular fragments 

of black obsidian.

Highly vesicular and thin walled Unknown Obsidian

Pumice breccia and sandstone (Tbxs) Pale-pink and white pumice breccia composed of frothy pumice chunks and black obsidian in a soft massive shard 

matrix. Some perlite. Underlain by gray tuff and sandstone, in part very calcareous. Thickness ~37 m (120 ft).

Pumice highly vesicular and thin 

walled Unknown Obsidian and perlite

Intrusive dacite (Tdi) Dark-gray coarse-grained porphyritic dacite(?); contains abundant hornblende and fragments of Late Archean 

amphibolite. Unknown None Dacite, hornblende, amphibolite.

Pumice breccia and sandstone (Tbxc)

Upper half is dense red flow breccia and welded tuff containing abundant gray and black obsidian fragments <5 cm (2 

in) in diameter. Lower half is pink well-bedded conglomerate containing clasts of Nugget and Tensleep sandstones, 

Late Archean gneiss, and chunks of white pumice <15 cm (6 in) across. Near base, coarse-grained gray sandstone. 

Thickness ≥30 m (100 ft).

Pumice highly vesicular and thin 

walled Unknown Obsidian
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 32

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

TERTIARY

Mafic dike (Tm) Dull-green dense hard brittle igneous rock. Intrudes Cody Shale (Kc) on west flank of Mount Reid. Unknown Unknown None known

Basalt (Tb)

Near Teton Pass (youngest unit): Dark-gray fine-grained basalt

East and West Gros Ventre buttes: Dense fine-grained gray homogeneous basalt(?); slabby structure in flows. 

Greenish-yellow to black scoria locally at base and in other layers. Apparently similar to gray basalt included in 

andesite and basalt (Tab) north of Teton Pass (Schroeder 1972). Maximum thickness ~152 m (500 ft).

East and northeast of Jackson Hole (Eocene): Sills and flows of red and black basalt. Vuggy scoriaceous basalt intrudes 

Teewinot Formation (Tte) along Flat Creek.

Prone to rockfall on steep slopes Unknown None known

Trachyte porphyry (Ttrp)

Gray vesicular volcanic rock containing abundant plagioclase phenocrysts <10 mm (0.4 in) in length, pyroxene 

phenocrysts 1–2 mm (0.04–0.08 in) in diameter, and phenocrysts of olivine altered to iddingsite 1–2 mm (0.04–0.08 in) 

in diameter. In plug cutting Hominy Peak Formation (Thp) north of Two Ocean Lake.

Vesicular Unknown Mineral crystals

TERTIARY (PLIOCENE*)

Huckleberry Ridge Tuff (Yellowstone 

Group) (Th)

Member C (Thc)

Member B (Thb)

Member A (Tha)

Compound cooling unit of gray to brown rhyolitic ash-flow tuff, generally densely welded and devitrified but locally 

glassy or partly welded. Most parts contain abundant phenocrysts of quartz, sanidine, and sodic plagioclase, sparse 

opaque oxides, clinopyroxene, and fayalitic olivine. 2.059 ± 0.004 million years old (Lanphere et al. 2002).

Member C—Strongly foliated and lineated, entirely devitrified, containing glassy quartz phenocrysts smaller than those 

in members B and A. Conspicuous layering. Abundant lithic inclusions.

Member B—Coarsely porphyritic, entirely devitrified, light-brown to gray, welded tuff. Phenocrysts abundant and <5 

mm (0.2 in) long in upper part. Two types of welded pumice in upper part, one very dark and scoriaceous, the other 

light-colored and compact. Thickness <152 m (500 ft).

Member A—Mainly devitrified, but containing black vitrophyre at base. Phenocrysts abundant in lower part, but 

progressively less abundant upward. Thickness <213 m (700 ft).

* In 2009, the time spanned by the Quaternary Period was expanded. Therefore, several units listed as Pliocene on Love 

et al. (1992) now fall within the boundary of the Quaternary (starting 2.588 million years ago) including Th.

Erosion control likely needed. 

Pumice highly vesicular and thin 

walled.

Unknown Building stone

Drift(?) probably unrelated to glaciation 

1 (Tg1)

Unstratified gray till-like deposits of rounded to angular fragments of Mesozoic, Paleozoic, and sparse Precambrian 

rocks in matrix of gray clay, silt, and sand. In places tightly cemented with gray calcium carbonate and in places 

uncemented. Some quartzite clasts are striated. Many quartzite clasts were derived from considerable distances when 

present drainage systems were either nonexistent or buried by ice. Thickness ≥24 m (80 ft) in exposures below 

Huckleberry Ridge Tuff (Th) at north end of Signal Mountain.

* In 2009, the time spanned by the Quaternary Period was expanded. Therefore, several units listed as Pliocene on Love 

et al. (1992) now fall within the boundary of the Quaternary (starting 2.588 million years ago) including Tg1.

Used for wildlife habitat and 

recreation Unknown None known

Shooting Iron Formation (Tsi)

Pink, red, green, yellow, dark-gray, and brown bentonitic mollusk-bearing lacustrine and fluvial claystone, gray and 

yellow tuffaceous sandstone and siltstone, and pebble conglomerate of volcanic rock fragments in bentonitic matrix.

Exposed north of Flat Creek along east edge of map area and locally on south ends of East and West Gros Ventre 

buttes. 2.4–1.9 million years ago (Leopold et al. 2007). Thickness 91.5 m (300 ft) (Leopold et al. 2007).

* In 2009, the time spanned by the Quaternary Period was expanded. Therefore, several units listed as Pliocene on Love 

et al. (1992) now fall within the boundary of the Quaternary (starting 2.588 million years ago) including Tsi.

Bentonite

Mammal teeth, mollusks (some indicate 

deep-water environment), and pollen 

(see Leopold et al. 2007)

None known

TERTIARY

(PLIOCENE)

Conant Creek Tuff (Tcc)

In Jackson Hole: “Conant Creek Tuff” mapped by Love et al. (1992) is actually the distal facies of Kilgore Tuff. 4.45 

million years old (Morgan and McIntosh 2005).

Northern Teton Range: Gray to buff and pale-lavender phenocryst-poor slabby hard-welded rhyolite tuff. Black 

welded-tuff obsidian near base, underlain in places by white to gray friable tuff. 5.51 million years old (Morgan and 

McIntosh 2005). Thickness <91 m (300 ft).

Erosion control likely needed Unknown Obsidian

TERTIARY

(MIOCENE)

Conglomerate (Tcg)

Gray poorly cemented conglomerate underlying Conant Creek Tuff (Tcc) on northeast and east sides of Signal 

Mountain. Consists chiefly of quartzite roundstones, some Paleozoic and Mesozoic sedimentary rock fragments, and 

some Tertiary andesite clasts. Thickness 366 m (1,200 ft).

Unknown Unknown None known

Teewinot Formation (Tte)

Chalky-white to light-gray soft porous limestone, claystone, and pumicite. Upper part is very fossiliferous thin-bedded 

claystone, marlstone, and tuff. Lower two-thirds, chiefly nodular porous limestone in beds 30–60 m (100–200 ft) thick 

interbedded with pumicite in beds 6–23 m (20–75 ft) thick. In middle part of formation is a 34-m- (110-ft-) thick 

conglomerate of limestone, quartzite, and obsidian clasts. 12 million to 7.5 million years old (Perkins and Nash 1994). 

Thickness >1,829 m (6,000 ft).

Forms soft, porous substrate

Snails; clams; ostracodes; diatoms; fish 

bones; teeth of aquatic mice, beaver, and 

shrews. Coniferous wood and pollen 

fossils.

Obsidian
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 33

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

TERTIARY (MIOCENE)

Detachment mass of Madison 

Limestone within Teewinot Formation 

(Ttem)

About 5 km (3 mi) northeast of Jackson Peak Unknown Unknown None known

Basalt intruded into Colter Formation 

(Tbc)

Gray sugary breccia and dense black and red basalt on Ditch Creek. Relation to Colter Formation uncertain but could 

be contemporaneous.

Basalt prone to rockfall on steep 

slopes Unknown None known

Colter Formation (Tc)

Light-gray, green, and brown water-laid tuff, sandstone, claystone, and mafic volcanic conglomerate. Light-gray 

tuffaceous soft massive to irregularly bedded poorly cemented sandstone beds in lower part.Locally, an upper 

conglomerate, <18 m (60 ft) thick, consists of 50% roundstones of mafic volcanic rocks and 50% quartzite. Some 

rhyolitic welded tuff in upper part. A middle tuffaceous sandstone and claystone sequence contains many layers of grit 

and pebble conglomerate of mafic andesite and basalt clasts. Some thick beds of pale-green, pink, and white bentonitic 

claystone. In some places basal beds are of quartzite, andesite, and basalt clasts in a drab tuff and sandstone matrix. 24 

million–3 million years old (Love et al. 2003). Thickness <1,494 m (4,900 ft).

Bentonite Mammalian fossils None known

TERTIARY

(OLIGOCENE)

White River Formation (Twr) White nodular calcareous siltstone and pale-green bentonitic claystone. Exposed locally along East Fork Pilgrim Creek 

north of west end of Two Ocean Lake. 35.8 million years old. Thickness <9 m (30 ft). Bentonite Vertebrate fossils None known

TERTIARY (EOCENE)

Wiggins Formation (Thorofare Creek 

Group, Absaroka Volcanic Supergroup) 

(Twi)

Yellow, chalky-white, and bright-red claystone, underlain by green and pink waxy claystone. Exposed along East Fork 

Pilgrim Creek north of west end of Two Ocean Lake. 45.9 million years old. Thickness <21 m (70 ft).

Bentonite, weathering with puffy 

surface. Absaroka volcanic known 

for mass-wasting phenomena. 

Headwaters of Snake River within 

this unit.

Fossil wood, vertebrate fossils Overlies oil-and-gas-producing strata

Hominy Peak Formation (Absaroka 

Volcanic Supergroup) (Thp)

East and northeast of Jackson Hole: Brown to dull-green andesitic mudflow breccia, vent breccia, conglomerate, and 

sandstone. Light-gray tuff and thin claystone zones near top and at base. In northwestern part of map area, contains 

slide blocks of Proterozoic, Paleozoic, and Mesozoic rocks 3–46 m (10–150 ft) in diameter. 48.6 million years old. 

Thickness <610 m (2,000 ft).

In and east of Jackson Hole: Brown to dull-green andesitic mudflow breccia, vent breccia, conglomerate, and 

sandstone. Light-gray tuff and thin claystone zones near top and at base. Lenses of gold-bearing quartzite boulder 

conglomerate in lower part. Thickness <610 m (2,000 ft).

Absaroka volcanic known for masswasting phenomena. Contains 

ancient slide blocks.

Fossil wood

Overlies oil-and-gas-producing strata

Gold

TERTIARY

Tuff of Boone Creek (Ttbc) Tuff of Boone Creek (no additional description given in source map). Unknown Unknown Unknown

TERTIARY

(EOCENE)

Basalt breccia (Tbb)

Red, brown, and purple basalt breccia of large and small angular fragments in matrix of same material. Some dikes and 

flows. May be an upper igneous facies of Langford Formation (Tl). Eposed on summit of Pinyon Peak and along Colter 

Creek 5.6 km (3.5 mi) to the west. 49.4 million years old. Thickness ≥122 m (400 ft).

Unknown Unknown Sand and gravel

Langford Formation (Thorofare Creek 

Group, Absaroka Volcanic Supergroup) 

(Tl)

Light-gray, volcanic conglomerate and tuff composed of andesite and basalt boulders with lesser amounts of quartzite, 

granite, and, locally, huge masses of limestone and dolomite. Tuff is dull-green to chalky-white, soft, sandy, blocky in 

part. Exposed on Pinyon Peak and in local areas to south and southwest. Thickness ≥152 m (500 ft).

Absaroka volcanic known for masswasting phenomenaMany fossil tree stumps. Vertebrate 

fossils.

Overlies oil-and-gas-producing strata. 

Rich in magnetite.

CRETACEOUS

–TERTIARY

Pinyon Conglomerate (TKp)

Rusty-brown conglomerate composed of quartzite roundstones in matrix of rusty coarse-grained sandstone containing 

tiny flakes of gold. Sporadic boulders of older conglomerate and quartzite 1.5–2.4 m (5–8 ft) in diameter. Thickness 

<1,158 m (3,800 ft).

Conglomerate beds mapped as linear features (TKpc).

Unknown Mollusks and plant fossils Gold and mercury

CRETACEOUS

Harebell Formation (Kh)

Conglomerate, sandstone, claystone, and tuff. Conglomerate consists of quartzite roundstones in matrix of brown 

gold-bearing sandstone. Sandstone is brown, gray, and dull-green, silty, hard, tuffaceous, rich in magnetite. Claystone 

is gray, dark-green, black, and mustard-yellow, silty, tuffaceous. Thickness < 3,048 m (10,000 ft).

Conglomerate beds mapped as linear features (Khc)

Bentonite

Marine or brackish water fossils at some 

horizons. Triceratops tracks east of park. 

Leaf fossils.

Gold, silver, and gravel. Hydrocarbon 

source rock.

Meeteetse Formation (Kme)

Chalky-white to gray salt-and-pepper soft sandstone, interbedded with yellow, pale-green, and dark-gray 

carbonaceous shale, thin coal beds, white slabby tuff, and yellow to gray bentonite beds. Conglomerate is composed of 

quartzite cobbles in gold-bearing sandstone matrix at several horizons. K-Ar age 73.1 ± 0.7 million years old. Thickness 

~305 m (1,000 ft).

Bentonite Plant fossils Gold and coal
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 34

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

CRETACEOUS

Mesaverde Formation (Kmv)

White massive- to thick-bedded soft porous medium- to coarse-grained sandstone containing abundant pink and 

green grains. Interbedded with thin gray shale and sparse impure coal and bentonite beds. Section near Elk Ranch 

Reservoir southwest of Moran Junction contains conglomerate beds of quartzite cobbles in gold-bearing matrix, one 

conglomerate as thick as 15 m (50 ft).

Bentonite Nonmarine mollusks. Fossil flora. Coal. Gold. Oil and gas reservoir (Jonah 

Field).

Sohare Formation (Ks) Lenticular gray and brown fine-grained, largely nonmarine sandstone interbedded with light- and dark-gray shale and 

siltstone. Contains thin coal beds. Thickness < 732 m (2,400 ft). Shale may result in slippage. Unknown Thin coal beds

Bacon Ridge Sandstone (Kb) Tan to gray thick-bedded fine-grained sandstone. Interbedded with gray marine and brackish-water shale and 

siltstone. Thickness 305–457 m (1,000–1,500 ft). Bentonite near top and in lower part 

Abundant marine fossils, leaf 

impressions (Trapa microphyyla), and 

fossil seeds

Coal (several beds have been mined). 

Gold. Ferruginous concretions with 

<14% zircon. Hydrocarbon source 

rock.

Sohare Formation and 

Bacon Ridge Sandstone (Ksb) See descriptions above. Shale may result in slippage; bentonite.

Abundant marine fossils, leaf 

impressions (Trapa microphyyla), and 

fossil seeds in Bacon Ridge Sandstone.

Coal (see descriptions above).

Cody Shale (Kc) Dull-gray marine shale, interbedded with lesser amounts of gray and black siltstone and fine-grained slabby glauconitic 

sandstone. Thickness 428–671 m (1,400–2,200 ft). Bentonite Mollusks None known

Frontier Formation (Kf) Gray fine- to coarse-grained sandstone, pebbly and highly glauconitic near top, interbedded with gray and black shale 

and thin coal beds. Thickness ~305 m (1,000 ft).

Bentonite in lower part. Landslides. 

Salt lick for deer and elk.

Oyster coquina, foraminifera, and plant 

fossils

Thin coal beds. Porcellanite beds in 

lower part. Hydrocarbon source rock.

Aspen Shale (Ka) Dull-green to black siliceous shale and claystone, interbedded with gray and greenish-gray hard brittle siliceous saltand-pepper sandstone and dull-green claystone Shale may result in slippage. Marine fossils. None known

Mowry Shale (Kmr) See description below. Bentonite in Mowry Shale Plant fossils. Fish fossils and ammonites 

elsewhere. Hydrocarbon source rock

Mowry and Thermopolis shales (Kmt)

Mowry Shale—Dark-gray to black, weathering silvery gray, very hard brittle silicified thin-bedded shale. Several 

cream-colored bentonite beds. Secondarily silicified fine-grained sandstone common. K-Ar age 99.7 ± 1.0 million years. 

Thickness 152–213 m (500–700 ft).

Thermopolis Shale—Black fine-grained flaky soft shale. Muddy Sandstone Member at top of formation is 6- to 30-m-

(20- to 100-ft-) thick rusty-brown to gray sandstone, interbedded with black and gray siltstone and shale. Thickness 

generally 45–60 m (150–200 ft), except north of Jackson Lake where it is only 17 m (55 ft).

Bentonite in Mowry Shale

Plant fossils. Fish fossils and ammonites 

elsewhere.

Plesiosaur bones and foraminifera 

elsewhere

Hydrocarbon source rock

Bear River Formation (Kbr) Greenish-gray calcareous sandstone, interbedded with dark-gray shale. Near base are cliff-forming gray sandstone 

beds, black shale beds, and, at base, slabby rusty sandstone. Thickness ~305 m (1,000 ft). Shale may result in slippage. Unknown None known

Gannett Group (Kg)

White to dark-gray limestone, variegated claystone, and reddish-brown siltstone in upper part. Maroon to red siltstone 

and sandstone, thin limestone, and ledge-forming conglomeratic sandstone beds in lower part. Lower part of sequence 

may be of Jurassic age (Eyer 1969; Furer 1970; Love and Christiansen 1985). Thickness ~213 m (700 ft).

Likely suitable for infrastructure Unknown None known

CRETACEOUS–

JURASSIC

Cloverly Formation (Lower 

Cretaceous) and Morrison(?) 

Formation (Upper Jurassic) (KJc)

Upper unit—Olive-green, gray, and buff thin-bedded sandstone that weathers with a conspicuous rusty color. 

Commonly known as the “rusty beds member” of the Cloverly Formation. Thickness 30–61 m (100–200 ft).

Middle unit—Variegated red, gray, lilac-colored, and pink bentonitic claystone weathering with a puffy surface.

Contains thin beds of hard nodular dense cream-colored limestone. Thickness 88–166 m (290–545 ft).

Lower unit—Buff and gray chloritic, in part sparkly, sandstone interbedded with red, green, and gray siltstone 

correlative with Morrison Formation. Thickness 56–76 m (185–250 ft).

Bentonite Fossiliferous elsewhere (dinosaur fossils 

and tracks) None known

JURASSIC

Upper Sundance Formation (Jus)

Glauconitic gray, buff, and green very calcareous sandstone. A few thin shale and very fossiliferous limestone beds. 

Forms ridges. Thickness 23–43 m (75–140 ft).

Unit not mapped within the park or parkway. Undivided Sundance and Gypsum Spring formations (unit Jsg; see 

below) mapped within Grand Teton National Park.

Shale may result in slippage. Abundant marine fossils: bryozoans, 

oysters, gastropods, and brachiopods Glauconite

Sundance and Gypsum Spring 

formations (Jsg)

Sundance Formation—Upper part (Upper Jurassic) is glauconitic gray, buff, and green very calcareous sandstone. A

few thin shale and very fossiliferous limestone beds. Forms ridges. Thickness 23–43 m (75–140 ft). Lower part (Upper 

and Middle Jurassic) is gray calcareous plastic to splintery shale, clayey limestone, hard oolitic limestone, and one or 

more zones of red soft plastic shale. Marine in origin. Thickness 122–168 m (400–550 ft).

Gypsum Spring Formation (Middle Jurassic)—Dark-red soft shale, underlain by and interbedded with slabby gray 

dolomite and white gypsum. In most outcrops the gypsum has been leached, leaving lithified carbonate breccia that 

forms rounded cliffs. Thickness 15–46 m (50–150 ft), depending on amount of gypsum leaching.

Shale may result in slippage. 

Dissolution possible in gypsum beds.

Abundant marine fossils: bryozoans, 

oysters, gastropods, and brachiopods

Bivalves, gastropods, ostracodes, 

crinoids, ammonites, and pelecypods

Oolitic limestone (building stone)

Gypsum
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 35

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

JURASSIC

Lower Sundance Formation (Jls)

Gray limy soft shale interbedded with shaly limestone; one or two red shale zones 35-70 feet (11-21 m) thick, 

commonly present in middle part. "Lower Sundance" of many reports. Thickness about 400 feet (120 m).

Unit not mapped within the park or parkway. Undivided Sundance and Gypsum Spring formations (unit Jsg; see 

above) mapped within Grand Teton National Park.

Shale may result in slippage.

Abundant marine fossils: bryozoans, 

oysters, gastropods, and brachiopods Oolitic limestone (building stone)

Gypsum Spring Formation (Jgs)

Dark-red soft shale, underlain by and interbedded with slabby gray dolomite and white gypsum. In most outcrops the 

gypsum has been leached, leaving lithified carbonate breccia that forms rounded cliffs. Thickness 15–46 m (50–150 ft), 

depending on amount of gypsum leaching.

Unit not mapped within the park or parkway. Undivided Sundance and Gypsum Spring formations (unit Jsg; see 

above) mapped within Grand Teton National Park.

Dissolution possible in gypsum beds. Bivalves, gastropods, ostracodes, 

crinoids, ammonites, and pelecypods Gypsum

Stump Formation and Preuss Redbeds 

(Jsp)

Stump Formation (Upper and Middle Jurassic)—Greenish- to brownish-gray cross-bedded fine- to medium-grained 

calcareous glauconitic sandstone. Limestone bed at top. Thickness ~40 m (130 ft).

Preuss Redbeds (Middle Jurassic)—Red shaly sandstone and siltstone. Thickness ~15 m (50 ft).

Likely suitable for infrastructure Unknown None known

Twin Creek Limestone (Jt)

Upper half is light-gray shaly limestone that fractures into pencil-shaped fragments. Lower half is red siltstone, shaly 

limestone, and oolitic limestone. Near base is Gypsum Spring Member, consisting of red and gray shale, dolomitic 

breccia, and gypsum. Thickness 244–274 m (800–900 ft).

Potential for fracture and dissolution Unknown Oolitic limestone (building stone). 

Gypsum.

JURASSIC–

TRIASSIC

Nugget Sandstone (JTRn)

North of Jackson thrust fault: Light-tan to salmon-pink fine-grained cross-bedded hard brittle cliff-forming sandstone 

characterized by large frosted rounded quartz grains in a finer matrix. Softer and more porous than unit south of 

Jackson thrust fault. Sequence wedges out 8 km (5 mi) north of Gros Ventre River. Thickness <61 m (200 ft).

South of Jackson thrust fault: Thickness 113–171 m (375–560 ft)

Porous but likely suitable for 

infrastructure Unknown Rounded quartz grains

TRIASSIC

Chugwater Formation (TRc)

North of Jackson thrust fault:

Popo Agie Member—Ocher and purple claystone, red shale, lenticular purple limestone-pellet conglomerate, and red 

siltstone. Thickness 23–91 m (75–300 ft).

Crow Mountain Sandstone Member—Red to salmon-pink soft porous sandstone containing large rounded quartz 

grains in a finer matrix. Thickness 15–30 m (50–100 ft).

Alcova Limestone Member—Gray and purple thin-bedded hard limestone and dolomite with interbeds of white 

gypsum. Thickness 6.2–18 m (10–60 ft).

Red Peak Member—Red gypsiferous siltstone and very fine-grained sandstone containing some red shale partings. 

Thickness 244–389 m (800–1,275 ft).

South of Jackson thrust fault: Red Peak Member contains some beds of gray silty limestone and gray quartzitic 

sandstone. Thickness 445–536 m (1,460–1,760 ft).

Shale may result in slippage. 

Dissolution possible in gypsum beds. Reptile tracks

Rounded quartz grains (Crown 

Mountain Sandstone Member)

Gypsum (Red Peak Member)

Ankareh Shale (TRa) Red to purple calcareous siltstone and shale with greenish-white polka-dot mottling in several layers. Thickness 137–

168 m (450–550 ft). Shale may result in slippage. Unknown None known

Thaynes Formation (TRt) Upper half is gray bioclastic limestone underlain by yellowish-gray limy siltstone and sandstone. Lower half is red 

siltstone underlain by slabby dark-brown fossiliferous silty limestone. Thickness 76–91 m (250–300 ft). Likely suitable for infrastructure Fossiliferous limestone None known

Woodside Formation (TRw) Red-brown siltstone, shale, and fine-grained sandstone. Thickness 244–305 m (800–1,000 ft). Shale may result in slippage. Unknown None known

Dinwoody Formation (TRd)

North of Jackson thrust fault: Brownish-gray to olive-drab hard slabby thin-bedded dolomitic siltstone. Contains thin 

partings of fine-grained dolomitic sandstone and silty limestone. Thickness 61–76 m (200–250 ft).

South of Jackson thrust fault: Thickness 137–183 m (450–600 ft)

Likely suitable for infrastructure Conodonts None known
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 36

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

PERMIAN

Phosphoria Formation and related 

rocks (Pp)

North of Jackson thrust fault: Black phosphatic shale (top); mudstone, carbonate rock, and sandstone; gray cherty 

dolomite, mudstone, and sandstone; black phosphorite, mudstone, and shale (base). Thickness 55–61 m (180–200 ft).

South of Jackson thrust fault: Thickness 70–79 m (230–260 ft) 

Radioactive layers. Petroliferous 

odor.

Trace fossils (e.g., burrows such as 

Thalassinoides), mollusks, and sponge 

spicules

Phosphorite. Chert geodes and chips. 

Calcite crystals and rinds. Hydrocarbon 

source rock.

PERMAIN–

PENNSYLVANIAN

and 

MISSISSIPPIAN

Wells and Amsden Formations 

(PPNMwa)

Wells Formation (Lower Permian, Upper and Middle Pennsylvanian)—Light-gray hard fine-grained sandstone. 

Contains gray limestone beds, which are more abundant in lower part. In places, uppermost part contains chalky-white 

brittle very fine-grained dolomite and gray chert. Grades into Amsden Formation. Thickness 137–305 m (450–1,000 ft).

Amsden Formation (Middle and Lower Pennsylvanian, Upper Mississippian)—Bluish-gray hard limestone,

interbedded with red and green shale and tan to white fine-grained sandstone. Thickness 137–213 m (450–700 ft).

Likely suitable for infrastructure Brachiopods, cephalopods, gastropods, 

and trilobithes

Hydrocarbon source rock. Chert.

Conspicuous red and mustard-yellow 

chert nodules and thin lenses.

PENNSYLVANIAN–

MISSISSIPPIAN

Tensleep Sandstone and Amsden 

Formation (PNMta)

Tensleep Sandstone (Upper and Middle Pennsylvanian)—Light-gray, weathering yellowish-brown, fine-grained hard 

brittle sandstone. Some zones of quartzite. Middle and lower parts contain many beds of gray hard fine-grained 

limestone and dolomite. Transitional with underlying Amsden Formation. Thickness 122–137 m (400–450 ft).

Amsden Formation (Middle and Lower Pennsylvanian, Upper Mississippian)—Upper part: Brick-red, red-brown, and 

green shale and siltstone, interbedded with white to pink dolomite and limestone. Thickness 70–137 m (230–450 ft).

Darwin Sandstone Member

Landslide potential (e.g., Gros Ventre 

slide)

: Gray to brownish-pink fine- to medium-grained cross-bedded moderately soft and 

porous sandstone. Red shale partings near top. Thickness 23–30 m (75–100 ft).

Moderately soft, porous sandstone

Foraminifera and bryozoans

Crinoids Several zones contain ocher and red 

chert nodules and lenses. Some large 

rounded frosted quartz grains.

MISSISSIPPIAN

Madison Limestone (Mm)

North of Jackson thrust fault: Light- to dark-gray limestone, thick-bedded to massive in upper part, thin-bedded and 

dolomitic in lower part, especially near base. Vuggy brown cherty dolomite near base. Many layers and lenses of black 

chert. Thickness 335–457 m (1,100–1,500 ft). Bull Ridge Member—Red shale and siltstone interbedded with orangered to tan sandstone, tan to pink dolomite breccia, and blue-gray ledge-forming limestone that contains highly 

distinctive red and gray-and-black-striped chert nodules. Occurs locally at top of formation. Thickness 15–30 m (50–

100 ft).

South of Jackson thrust fault: Thickness 335–457 m (1,100–1,500 ft)

Caves and karst Most fossils of any map unit. Abundant 

horn corals in massive beds, crinoids, 

gastropods, and brachiopods. At base, 

discontinuous thin marine black shale 

containing fish fragments.

Building stone. Chert lenses and 

nodules.

MISSISSIPPIAN–

DEVONIAN

Madison Limestone and Darby 

Formation (MDmd) East of Signal Mountain: See descriptions above and below Cave potential. Shale may result in slippage.

Madison Limestone contains most fossils 

of any map unit. Abundant horn corals in 

massive beds, crinoids, gastropods, and 

brachiopods. At base, discontinuous thin 

marine black shale containing fish 

fragments. Brachiopods, corals, 

bryozoans, crinoids, ostracodes, and 

stromatolites in Darby Formation.

Building stone. Chert lenses and 

nodules in Madison Limestone.

DEVONIAN

Darby Formation (Dd)

North of Jackson thrust fault: Upper part is dull-yellow, gray, pink, and black thin-bedded dolomitic siltstone and 

shale. Lower part is brown fetid vuggy siliceous brittle dolomite containing sparse thin limestone beds and thin 

sandstone beds. Thickness 87–107 m (285–350 ft).

South of Jackson thrust fault: Thickness 87–137 m (285–450 ft)

Shale may result in slippage. Brachiopods, corals, bryozoans, crinoids, 

ostracodes, and stromatolites None known

ORDOVICIAN

Bighorn Dolomite (Ob)

Light- and dark-gray mottled siliceous dolomite. Forms ragged gray cliffs. Thickness variable, 61–152 m (200–500 ft).

Leigh Dolomite Member: Chalky-white very fine-grained brittle dolomite. Forms slope at top of cliffs. Thickness about 

15 m (50 ft).

Caves and karst Corals (e.g., Rugosa), crinoids, 

brachiopods, and bryozoans None known

ORDOVICIAN

-CAMBRIAN

Bighorn Dolomite and Gallatin 

Limestone (OCbg) See descriptions above and below.

Caves and karst in Bighorn Dolomite. 

Gallatin Limestone Likely suitable 

for infrastructure but fossiliferous

Corals (e.g., Rugosa), crinoids, 

brachiopods, and bryozoans in Bighorn 

Dolomite. Trilobites, sponges, 

brachiopods, and conodonts in Gallatin 

Limestone.

None known
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 37

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

CABMRIAN

Gallatin Limestone (Cg) Dark-gray hard limestone, weathering tan mottled with yellow splotches. Some green shale near middle. Lower part 

contains flat-pebble “edge-wise” conglomerate. Some beds glauconitic. Forms cliffs. Thickness 61–76 m (200–250 ft).

Likely suitable for infrastructure but 

fossiliferous

Trilobites, sponges, brachiopods, and 

conodonts None known

Gallatin Limestone and Park Shale 

Member of Gros Ventre Formation 

(Cgg)

Gallatin Limestone—Dark-gray hard limestone, weathering tan mottled with yellow splotches. Some green shale near 

middle. Lower part contains flat-pebble “edge-wise” conglomerate. Some beds glauconitic. Forms cliffs. Thickness 61–

76 m (200–250 ft).

Park Shale Member—Olive-green soft flaky micaceous shale. Contains thin beds of flat-pebble limestone 

conglomerate. Thickness 46–107 m (150–350 ft).

Shale may result in slippage. Basal part has numerous large and small 

algal heads (reefs). None known

Gros Ventre Formation (Cgv)

Park Shale Member (Upper and Middle Cambrian)—Olive-green soft flaky micaceous shale. Contains thin beds of flatpebble limestone conglomerate. Thickness 46–107 m (150–350 ft).

Death Canyon Limestone Member (Cgd) (Middle Cambrian)—Blue- to dark-gray, mottled with brown and tan 

irregular splotches, fine-grained hard dense thin-bedded cliff-forming limestone. Locally, at base, a distinctive bed of 

brown-weathering dolomite. Thickness 91–113 m (300–370 ft).

Wolsey Shale Member (Middle Cambrian)—Green to gray-green soft highly fissile micaceous shale. More silty near 

base. Lower part is very glauconitic and interbedded with sandstone. Glauconite weathers to red hematitic color.

Contact transitional with underlying Flathead Sandstone (Cf). Thickness 30–40 m (100–130 ft).

Shale may result in slippage.

Caves and karst

Basal part has numerous large and small 

algal heads (reefs).

Plant fossils (Tetonophyeus blackwelderi). 

Middle part contains 9 m (30 ft) of flaky 

green shale with abundant trilobites. 

Worm borings.

Brachiopod fossils and bivalves

None known

Wolsey Shale Member of Gros Ventre

Formation and Flathead Sandstone 

(Cgf)

South of Jackson thrust fault:

Wolsey Shale Member of Gros Ventre Formation (see description above) 

Flathead Sandstone (see description below)

Shale may result in slippage. Brachiopod fossils None known

Flathead Sandstone (Cf)

North and (or) south of Jackson thrust fault: Indurated white, tan, brown, and maroon cross-bedded hard sandstone, 

locally quartzitic, and locally conglomeratic near base. Forms cliffs. Thin partings of green micaceous shale in upper 

part. Thickness 61–91 m (200–300 ft).

Shale may result in slippage. Horizontal feeding traces and vertical 

burrows Building stone

PROTEROZOIC

Quartz veins (PCq) White to light-pink quartz, massive to strongly foliated and lineated. Emplaced after 2,450 million years ago. Used for recreation (e.g., climbing). 

Erosion control may be needed. None None known

Diabase dikes (PCd)

Dikes composed of medium- to dark-gray or gray-green fine- to medium-grained diabase. Commonly contain tabular 

phenocrysts of plagioclase 1–5 mm (0.04–0.2 in) long. Undeformed but slightly metamorphosed and display chilled 

margins. Probably emplaced before 1,450 million years ago, likely 765 million years old (Love et al. 2003).

Used for recreation (e.g., climbing). 

Erosion control may be needed. None None known

Mount Owen Quartz Monzonite and 

associated pegmatite (Xmo); (Wmo in 

Love et al. 2003)

Medium- to fine-grained light-colored massive to weakly flow-foliated biotite quartz monzonite containing dikes, 

pods, and irregular masses of muscovite- and biotite-bearing pegmatite. Quartz monzonite is relatively uniform in 

central parts of larger plutons. Near margins and in smaller bodies, pegmatite is very abundant and tabular inclusions 

of wallrocks a few inches to tens of feet across comprise nearly 50% of the volume of the rock. Near large plutons of 

quartz monzonite, pegmatite and aplite dikes comprise nearly 50% of the volume of the wallrocks; in these areas, 

contacts between Mount Owen Quartz Monzonite containing abundant inclusions of country rock and country rocks 

containing abundant dikes of pegmatite and aplite are largely arbitrary. Emplaced at about 2,450 million years ago (age 

recalculated from Reed and Zartman [1973], using new constant). Love et al. (2003) reports 2,545 million years old and 

suggests Wmo (Archean) as symbol.

Used for recreation (e.g., climbing). 

Erosion control may be needed. None Pegmatite

Granitic rocks of the Gros Ventre 

Range (Xg); same age as Wmo (Love et 

al. 2003)

Fine- to medium-grained massive to faintly foliated light-colored biotite quartz monzonite containing abundant 

inclusions of migmatitic biotite gneiss, foliated granitic gneiss, and layered biotite and amphibole gneiss. May be 

equivalent to Mount Owen Quartz Monzonite of Teton Range.

Used for recreation (e.g., climbing). 

Erosion control may be needed. None

Locally contains conspicuous large 

crystals of potassium feldspar 12–25 

mm (0.5–1.0 in) in diameter. Cut by 

abundant dikes of muscovite- and 

biotite-bearing pegmatite.

ARCHEAN

Rendezvous Metagabbro (Wr)

Gray to dark-green coarse-grained nonlayered weakly foliated metagabbro, typical blotchy appearance produced by 

irregular clots of dark-green hornblende 2–5 cm (0.8–2 in) in diameter in a matrix of light-gray plagioclase. Locally 

contains layers and inclusions of wallrocks. Pods and lenses of similar metagabbro, probably fragments of deformed 

dikes and sills, are abundant in nearby country rocks.

Used for recreation (e.g., climbing). 

Erosion control may be needed. None None known

Ultramafic rocks (Wu) Pods and small tabular bodies of serpentinized dunite or peridote and associated uralitized gabbro, a few feet to a few 

hundred feet in diameter

Used for recreation (e.g., climbing). 

Erosion control may be needed. None Teton jade, soapstone, and asbestos

Amphibolite (Wa) Fine- to medium-grained massive to well-foliated and well-lineated dark-green to greenish-gray amphibolite Used for recreation (e.g., climbing). 

Erosion control may be needed. None Locally contains large crystals of plagioclase or garnet.
Rows shaded in gray are included in the digital geologic data but are not mapped within Grand Teton National Park or John D. Rockefeller, Jr. Memorial Parkway

GRTE Geologic Resources Inventory Report 38

Age Unit Name

(Symbol) Description and Features Use for Habitat, Recreation, and Infrastructure Paleontological Resources Mineral Occurrence

ARCHEAN

Layered gneiss and migmatite (Wgm)

Magnetite iron-formation and 

associated rocks (Wi)

Biotite gneiss with magnetite eyes 

(Woo)

Pods and lenses of metagabbro (Wom)

Complexly interlayered fine- to medium-grained biotite gneiss and schist, quartz-plagioclase gneiss, amphibole gneiss 

and schist, and amphibolites. Layers range from 1.3 cm (0.5 in) to tens of feet in thickness. Some extend only a few feet 

and others are continuous for hundreds of feet. Adjacent to larger masses of Mount Owen Quartz Monzonite (Xmo), 

the gneisses grade into light-colored less conspicuously layered migmatites.

i—Layered gneiss and migmatite, magnetite iron-formation, and associated anthophyllite schist, cordierite gneiss, and 

impure marble

oo—Medium-gray biotite gneiss containing magnetite aggregates 0.5–1 cm (0.2–0.4 in) in diameter surrounded by 

bleached haloes lacking biotite (“bright-eyed” gneiss of Bradley [1956])

++—Areas where gneiss contains abundant pods and lenses of metagabbro

Used for recreation (e.g., climbing). 

Erosion control may be needed. None

Microcline crystals and lenses of quartz 

and feldspar in migmatite

Magnetite crystals form bright augen 

crystals (“eyes”)

Webb Canyon Gneiss (Ww)

Medium- to coarse-grained strongly foliated nonlayered biotite- and hornblende-bearing quartz monzonite gneiss 

containing abundant allanite. Commonly cut by small discordant dikes of hornblende-bearing pegmatite. Rock 

mapped as Webb Canyon Gneiss in the large body north and east of Eagles Rest Peak and the easternmost small body 

near mouth of Snowshoe Canyon is very strongly foliated migmatitic biotite gneiss that lacks hornblende and allanite. 

These bodies, and perhaps some of the rocks mapped as Webb Canyon Gneiss near Rammel Mountain, probably form

a separate unit. 2,680 million years old (Zartman and Reed 1998).

Used for recreation (e.g., climbing). 

Erosion control may be needed. None Pegmatite

Augen gneiss (Wag) Medium-grained, strongly foliated and lineated, rudely layered to nonlayered, medium- to dark-gray biotite gneiss.

Locally contains thin layers of amphibolite and biotite gneiss lacking feldspar augen.

Used for recreation (e.g., climbing). 

Erosion control may be needed. None

Conspicuous ovoid crystals (augen) of 

white microcline 1–4 cm (0.4–1.6 in) 

long

PRECAMBRIAN

Shear Zone (PCsz) Broad zone of sheared and discolored rocks near Dead Horse Pass. Used for recreation (e.g., climbing). 

Erosion control may be needed. None Unknown
GRTE Geologic Resources Inventory Report 39

Geologic History

This section describes the rocks and unconsolidated deposits that appear on the digital 

geologic map of Grand Teton National Park and John D. Rockefeller, Jr. Memorial 

Parkway, the environment in which those units were deposited, and the timing of geologic 

events that created the present landscape.

Grand Teton National Park hosts rocks ranging in age 

from Archean to Quaternary (fig. 13). In John D. 

Rockefeller, Jr. Memorial Parkway, rocks of Cretaceous 

age, Tertiary volcanics, and Quaternary sediments have 

primary significance. The Teton Range consists of an 

uplifted core of igneous and metamorphic Archean and 

Proterozoic rocks. Paleozoic and Mesozoic sedimentary 

rocks surround the central core, excepting the Cenozoic 

deposits that dominate the land surface immediately east 

of the core, in Jackson Hole. 

Archean and Proterozoic Eons (4 billion to 542 million 

years ago)

The oldest rocks in Grand Teton National Park are also 

some of the oldest rocks in the National Park System and 

the world. These rocks represent Archean (4.0 billion to 

2.5 billion years old) crust, part of the North American 

protocontinent. The Archean suite is composed of 

gneiss, amphibolites, ultramafic rocks, and metagabbro. 

These rocks also contain iron formations, which provide 

evidence for the evolution of oxygen in the atmosphere 

and hydrosphere. 

A major episode of regional deformation and 

metamorphism occurred at the end of the Archean Eon,

when massive amounts of granitic rock intruded older 

metamorphic rock. Isotopic dating of the Mount Owen 

Quartz Monzonite shows that this invasion occurred 

about 2,545 million years ago (Love et al. 2003). The next 

significant event recorded in the rocks at Grand Teton 

National Park was the Late Proterozoic intrusion of 

mafic magma (i.e., diabase dikes). These dikes, which cut 

across the general metamorphic grain of older Archean 

rocks, are nearly vertical sheets that range in thickness 

from a few centimeters to more than 46 m (150 ft) (Love 

et al. 2003). The most prominent of these dikes is located 

on the east face of Mount Moran (fig. 8). Analysis of 

similar rocks from other locations has suggested that the 

diabase dikes were emplaced about 765 million years ago 

(Love et al. 2003). These black dikes are the youngest 

Precambrian rocks in the park and represent the last 

event of the Proterozoic Eon (2.5 billion to 542 million 

years ago).

Erosion flattened the Archean and Proterozoic rocks of 

the Teton region into a relatively flat plain before the 

deposition of the Flathead Sandstone (510 million years 

ago), the first Paleozoic rock unit in the park.

Paleozoic Era (542 to 251 million years ago)

At the beginning of the Paleozoic Era, the area of the 

future Tetons began to subside and a shallow sea 

advanced from the west. Sedimentation into this basin 

resulted in the Flathead Sandstone and Gros Ventre 

Formation (Upper and Middle Cambrian). Exposures of 

Flathead Sandstone atop Mount Moran attest to later 

uplift and movement along the Teton fault. The 

nearshore sands of the Flathead Formation graded into 

the mud and marine debris of the Gros Ventre 

Formation as the sea advanced. The three members of 

the Gros Ventre Formation (Wolsey Shale, Death 

Canyon Limestone, and Park Shale) reflect transgression 

and regression of the shallow sea; limestone was 

deposited in deeper water (>30 m [100 ft]), while shale 

was deposited in shallower water (<30 m [100 ft]). The 

shale beds (lithified mud) contain body fossils of 

brachiopods and trilobites and trace fossils (trails and 

burrows) of a wormlike creature (Love et al. 2003). 

Sea level fluctuated throughout much of the Paleozoic 

with the deposition of the Gallatin Limestone (Middle to 

Late Cambrian), Bighorn Dolomite (Middle to Late 

Ordovician), dolomite and shale of the Darby Formation 

(Devonian), and Madison Limestone (Mississippian). 

Corals and other marine animals were abundant in the 

clear, warm seas when the Bighorn Dolomite was 

deposited. Fossil scales and bones in the Darby 

Formation indicate that fish were abundant at that time. 

The remains of corals, crinoids, gastropods, and 

brachiopods, which inhabited warm, tranquil seas, 

became the Madison Limestone (Love et al. 2003). 

Volcanic arcs developed toward the end of the Paleozoic 

(Pennsylvanian and Mississippian periods), and the 

Ancestral Rocky Mountains rose to the east in what is 

now central Wyoming. The shallow sea became 

increasingly restricted, creating a broad embayment 

between the offshore volcanoes and the rest of North 

America (Love et al. 2003). Limestone of the Wells and 

Amsden formations and the Tensleep Sandstone were 

deposited in this restricted bay. Material from the flanks 

of the Ancestral Rockies contributed to these formations 

(Love et al. 2003). The Paleozoic Era ends with the 

Permian Period, which is represented in Grand Teton 

National Park by the Phosphoria Formation. This

formation accumulated in a shallow-water zone near 

deep, upwelling, nutrient-rich water (Love et al. 2003).

Mesozoic Era (251 to 65.5 million years ago)

Love et al. (1992) mapped more than two dozen rock 

units from the Mesozoic Era (Triassic, Jurassic, and 

Cretaceous periods) with a combined thickness of more 

than 3,050 m (10,000 ft) in the Teton–Jackson Hole area 

(see Map Unit Properties Table). Deposition of 

sediments in relatively shallow seas that covered the 

Teton area continued throughout the Mesozoic Era,
40 NPS Geologic Resources Division 

creating alternating beds of sandstone, shale, limestone, 

and dolomite. The areal extent of the inland seas reached 

a maximum in the Cretaceous Period when the 

Cretaceous Interior Seaway extended from the Arctic to 

the tropics, covering the entire west-central part of the 

North American continent. The Cretaceous sea left thick 

deposits of shale and sandstone such as the Thermopolis, 

Mowry, Aspen, and Cody shales and the Frontier 

Formation (sandstone). Toward the end of the 

Cretaceous Period, mountains rose to the west and

sedimentation increased with the transition from a 

marine to a terrestrial setting. This type of sedimentation 

included conglomerate, which was mostly fluvial; 

sandstone and shale, which accumulated along muddy 

coasts; coal formed from organic-rich sediments of 

marsh environments; and bentonite derived from the 

alteration of volcanic ash. As the sea retreated, the 

sediments of the Sohare, Mesaverde, Meeteetse, and 

Harebell formations, and the Bacon Ridge Sandstone,

were deposited along the western shore (Love et al. 

2003).

The late Cretaceous and early Tertiary (Paleogene) were 

characterized by orogeny in the Teton region. This era of 

uplift and mountain building displaced the interior 

seaway and ultimately formed the Rocky Mountains 

(Smith and Siegel 2000). The Sevier Orogeny compressed 

the terrain and carried massive sheets of sedimentary 

rock eastward, producing extensive highlands and 

mountains from which sediment was shed into the Teton 

region. The Laramide Orogeny formed the Rocky 

Mountains in Wyoming, Colorado, New Mexico, and 

southwestern Montana. These mountains differ from 

those formed by the shallow thrust sheets of the Sevier 

Orogeny; they are upthrown blocks of sedimentary rock 

with cores of Precambrian metamorphic rocks and 

granite. During this time, a large northwest–southeasttrending uplift rose where the Teton and Gros Ventre 

ranges are today. This probably extended north into the 

Yellowstone area (Love et al. 2003). 

Cenozoic Era (the past 65.5 million years)

Laramide uplift and thrusting continued to shed large 

quantities of sediment from the highland areas to fill 

Jackson Hole during the Cenozoic Era (65.5 million years 

ago to the present time). Jackson Hole subsided as the 

sediment accumulated in the basin, creating space for a 

thick sequence of sedimentary rock. According to Love 

et al. (2003), few other regions of North America contain 

a thicker or more complete, nonmarine Tertiary 

(Paleogene and Neogene periods) record. Furthermore, 

“the character and volume of the Tertiary strata are clear 

evidence of the instability of the Earth’s crust in the 

Teton region during much of the Tertiary” (Love et al. 

2003, p. 62).

Most of the Cenozoic Era at the park and parkway has 

been characterized by volcanism, excepting the White 

River Formation, which was deposited in the Oligocene 

Epoch during a time of quiescence. The Tertiary 

(Paleogne) volcanics and the Absaroka Volcanic 

Supergroup (e.g., Langford, Hominy Peak, and Wiggins 

formations) began erupting 53 million to 43 million years 

ago during the Eocene Epoch. The Absaroka volcanic 

field, northeast of the present-day park and parkway, 

contains huge volumes of volcanic material, including 

tuff formed from consolidated ash. Some of this material

is interbedded with conglomerate and sandstone 

containing fossilized leaves and petrified wood, notably 

in the fossil forests of Yellowstone National Park. 

Volcanism continued in the Miocene Epoch with the 

deposition of the Colter Formation, as well as flow 

breccia, dacite, pumice, scoria, basalt, perlite, andesite, 

rhyolite, and obsidian (Love et al. 1992) related to Basin 

and Range extension. 

Huge lakes formed during the Miocene and Pliocene 

epochs. Lake Teewinot (1,800 km2 [700 mi2

]) formed 

near the southern boundary of the park during the 

Miocene. Downwarping of the trough that contained the 

Colter Formation interrupted south-flowing drainage 

and impounded the lake. Volcanic ash and richly 

fossiliferous (e.g., snails, clams, ostracodes, diatoms, 

pollen, fish bones, and teeth of aquatic mice, beaver, and 

shrews) sediments accumulated in the lake. Shooting 

Iron Lake, represented by the Shooting Iron Formation, 

occupied southern Jackson Hole during the Pliocene 

(Leopold et al. 2007). Mammal teeth and fossil mollusks 

indicate a deepwater environment (Love et al. 1992), and 

pollen data suggest a climate like that of present-day 

Jackson Hole and the surrounding foothills (Leopold et 

al. 2007). 

The Pliocene Epoch marks another phase of volcanic 

activity in the Teton region, with the formation of the 

Heise volcanic field north of Idaho Falls, Idaho. This 

field preceded the present-day Yellowstone Plateau 

volcanic field on the Snake River Plain (Morgan and 

McIntosh 2005). The 5.5-million-year-old Conant Creek 

Tuff and the 4.45-million-year-old Kilgore Tuff 

document Heise volcanism in the park and parkway. 

The first manifestations of the Yellowstone hot spot in 

the Teton region occurred 2.05 million years ago, and are 

recorded in the rock record by the Huckleberry Ridge 

Tuff and the final layer of ash in Lake Teewinot 

(Teewinot Formation). The 900,000-year-old Lewis 

Canyon Rhyolite and the 630,000-year-old Lava Creek 

Tuff document the continuation of volcanic (hot-spot) 

activity into the Pleistocene Epoch.

The Laramide Orogeny provided the first uplift of the 

Teton Range. Compression forces drove a reverse fault 

(the Buck Mountain fault) that elevated the rocks of the 

central Teton Range. The range’s second uplift occurred 

after 4.5 million years ago, when significant movement

began on the Teton fault (Morgan and McIntosh 2005; 

Leopold et al. 2007). Seismic activity increased into the 

Pleistocene, but post-glacial (non-tectonic) displacement 

may also have contributed to further uplifting of the crest 

of the Teton Range (Susong et al. 1987; Smith et al. 

1990a, 1993). Most (~80%) of the displacement along the 

Teton fault is a result of the dropping of the JacksonHole block along the fault. Uplift of the Teton-Range 

block along the fault accounts for the remaining 20% of 

displacement (Love et al. 2003) (see fig. 2). Unlike the 

Laramide Orogeny, which uplifted the rocks through 
GRTE Geologic Resources Inventory Report 41

compression, the rise of the Teton Range along the 

Teton fault is a result of extension. Laramide 

deformation caused thrust and reverse faults, while the 

more recent uplift of the Teton Range occurred along a 

normal fault.

Although some evidence attests to several periods of 

glaciation in the Teton–Jackson Hole area during the last 

2.5 million years, subsequent glaciations have destroyed 

most of these older features. Eight or more glaciations 

may have preceded the Bull Lake glaciation in the region, 

but little is known about these early processes (Good and 

Pierce 1996). “Glaciation 1” is represented only by 

preserved evidence of drift within and east of Jackson 

Hole (Love et al. 1992). 

The Bull Lake (160,000–130,000 years ago, but possibly 

beginning 190,000 years ago) and Pinedale (70,000–

15,000 years ago) glaciers produced most of the Ushaped valleys, jagged peaks, and piled moraines in the 

region. Geologists named these glaciations for areas in 

the Wind Rivers of Wyoming where they were first 

studied and mapped, and the terms now have regional 

use in Colorado and Utah. Glaciation 2 (Qg2) and 

glaciation 3 (Qg3) of Love et al. (1992) are Bull Lake 

deposits. In the Teton region, investigators refer to Bull 

Lake glacial deposits as “Munger,” after Munger 

Mountain at the southern end of Jackson Hole (Pierce 

and Good 1992). This glaciation entirely filled Jackson 

Hole with ice (Pierce and Good 1992). A blanket of loess 

blown from the bare glacial outwash plains during the 

subsequent Pinedale glaciation covers most Bull Lake 

deposits (Love et al. 2003). 

Love et al. (1992) mapped Pinedale deposits as glaciation 

4 (Qg4). The Pinedale glaciations are divided into three 

phases in the Teton region: Burned Ridge (70,000–30,000 

years ago), Hedrick Pond (~35,000 years ago), and 

Jackson Lake (ended by 15,000 years ago) (Pierce and 

Good 1992). Three lobes of ice moved into the Jackson 

Hole area during Pinedale glaciation: (1) the Snake River 

lobe entered the region from the north and moved south;

(2) the Pacific Creek lobe came from the northeast and 

advanced to the southwest; and (3) the Buffalo Fork lobe 

flowed into Jackson Hole from the east and moved west.

The size of these three lobes kept changing throughout 

Pinedale time, with a general trend in mass from east 

(Buffalo Fork lobe) to west (Snake River lobe). Smaller 

mountain glaciers also flowed from the Teton Range. 

North of Jenny Lake, glaciers from the Teton Range 

joined the south-flowing Snake River lobe. The smaller

Teton valley glaciers extended only about 2.5 km (1.5 mi) 

beyond the mountain front. The surface area of the 

Teton Range was too small to host the development of 

large glaciers, so most ice (and outwash debris) came 

from the much larger area of high terrain to the north 

and east (Pierce and Good 1992). Significantly, however, 

valley glaciers carved many glacial features and formed 

the end moraines that dammed Jenny, Bradley, Taggart, 

and Phelps lakes. The three lobes of ice also left 

substantial outwash and enormous quantities of gravel. 

During the Burned Ridge (first) phase of Pinedale 

glaciation, glaciers scoured basins into Jackson Hole 

valley, including those for Two Oceans and Emma 

Matilda lakes. These glaciers also deposited abundant 

outwash debris that covered much of the previous Bull 

Lake (Munger) moraine material (Pierce and Good 

1992). During the Hedrick Pond and Jackson Lake 

(second and third) phases of glaciation, the southflowing Snake River lobe completed the excavation 

begun by faulting, carving the Jackson Lake basin into its 

present shape. Glacial activity during the Hedrick Pond 

phase created kettle (“pothole”) terrain. Glaciers from 

the Teton Range carved basins for the other piedmont 

lakes during the Jackson Lake phase. Moraines from this 

phase dammed the piedmont lakes, including the 

southern end of Jackson Lake. This forced the Snake 

River, which feeds and drains Jackson Lake, to exit on 

the lake’s east side (Pierce and Good 1992; Elias 1996).

According to Love et al. (2003), a complex array of 

alluvial fans and stream terraces built up during and after 

glaciers covered most of the Jackson Hole floor. These 

landforms are situated outside the Pinedale terminal 

moraines and record much of the latest history of the 

southern parts of the valley. Alluvium occurs as 

floodplain deposits and alluvial fans in valleys; it 

commonly consists of well-sorted beds of silt, sand, and 

gravel. Much of the alluvium in this area is glacial

outwash that has been reworked by modern streams but 

greatly resembles the parent material. Alluvial fans have 

formed along the margins of Jackson Hole where streams 

enter the valley from surrounding uplands. Relatively 

large amounts of groundwater occur within the alluvium 

of the park (Cox 1974). Frost action pries loose blocks of 

exposed rock that tumble down and come to rest in the 

form of fan-shaped talus aprons draping many of the 

lower mountain slopes and canyon walls (Love et al. 

2003). Landslides form, move, and can temporarily dam 

rivers and impound lakes. Lakes and wetlands dot the 

landscape. Debris-rich deposits of clay, silt, and fine sand 

or thinly laminated white marl, ash, and clay accumulate 

in kettles. In addition, springs deposit travertine. Love et 

al. (2003) identified 11 hot springs, warm springs, and 

thermal wells in and near Jackson Hole.
42 NPS Geologic Resources Division 

Glossary

This glossary contains brief definitions of technical geologic terms used in this report. Not all 

geologic terms used are referenced. For more detailed definitions or to find terms not listed

here please visit: http://geomaps.wr.usgs.gov/parks/misc/glossarya.html. Definitions are 

based on those in the American Geological Institute Glossary of Geology (fifth edition; 2005).

aggradation. The building-up of Earth’s surface by 

depositional processes, specifically the upbuilding 

performed by a stream in order to establish or 

maintain uniformity of grade or slope.

alluvial fan. A fan-shaped deposit of sediment that 

accumulates where a hydraulically confined stream 

flows to a hydraulically unconfined area. Commonly 

out of a mountainous area into an area such as a valley 

or plain.

alluvium. Stream-deposited sediment.

alpine glacier. A glacier occurring in a mountainous 

region; also called a valley glacier.

amphibole. A common group of rock-forming silicate 

minerals. Hornblende is the most abundant type.

amphibolite. A metamorphic rock consisting mostly of 

the minerals amphibole and plagioclase with little or 

no quartz. 

andesite. Fine-grained volcanic rock commonly 

associated with subduction zone volcanoes. Named 

for the subduction zone volcanoes of the Andes 

Mountains.

aquifer. A rock or sedimentary unit that is sufficiently 

porous that it has a capacity to hold water, sufficiently 

permeable to allow water to move through it, and 

currently saturated to some level.

artiodactyla. Any of the order Artiodactyla of ungulates 

(as camel or pig) with an even number of functional 

toes on each foot. 

ash (volcanic). Fine material ejected from a volcano (also 

see “tuff”).

augen. Describes large lenticular mineral grains or 

mineral aggregates that have the shape of an eye in 

cross-section. Found in metamorphic rocks such as 

schists and gneisses.

avulsion. The sudden cutting off or separation of land by 

a flood or by an abrupt change in the course of a 

stream, as by a stream breaking through a meander or 

by sudden change in current whereby the stream 

deserts its old channel for a new one.

basalt. A dark-colored, often low-viscosity, extrusive 

igneous rock.

base flow. Stream flow supported by groundwater; flow 

not attributed to direct runoff from precipitation or 

snow melt.

base level. The lowest level to which a stream can erode 

its channel. The ultimate base level for the land surface 

is sea level, but temporary base levels may exist locally. 

basin (sedimentary). Any depression, from continental to 

local scales, into which sediments are deposited.

basin (structural). A doubly plunging syncline in which 

rocks dip inward from all sides.

bed. The smallest sedimentary strata unit, commonly 

ranging in thickness from one centimeter to a meter or 

two and distinguishable from beds above and below.

bedding. Depositional layering or stratification of 

sediments.

bed load. The part of the total stream load that is moved 

on or immediately above the stream bed such as the 

larger or heavier particles (boulders, pebbles, and 

gravel) transported by traction or saltation along the 

bottom; the part of the load that is not continuously in 

suspension or solution. 

bedrock. A general term for the rock that underlies soil 

or other unconsolidated, surficial material.

biotite. A widely distributed and important rock-forming 

mineral of the mica group.

block (fault). A crustal unit bounded by faults, either 

completely or in part.

brachiopod. Any marine invertebrate belonging to the 

phylum Brachiopoda, characterized by two bilaterally 

symmetrical valves that are commonly attached to a 

substratum but may also be free. Range—Lower 

Cambrian to the present.

braided stream. A sediment-clogged stream that forms 

multiple channels which divide and rejoin.

breccia. A coarse-grained, generally unsorted 

sedimentary rock consisting of cemented angular 

clasts greater than 2 mm (0.08 in).

caldera. A large bowl- or cone-shaped depression at the 

summit of a volcano. Formed by explosion or collapse.

carbonate. A mineral that has CO3

-2 as its essential 

component (e.g., calcite and aragonite).

carbonate rock. A rock consisting chiefly of carbonate 

minerals (e.g., limestone, dolomite, or carbonatite).

cephalopod. A marine mollusk of the class Cephalopoda, 

characterized by a head surrounded by tentacles and, 

in most fossil form, by a straight, curved, or coiled 

calcareous shell divided into chambers by transverse 

septa. Range—Cambrian to the present. 

chemical weathering. Chemical breakdown of minerals 

at Earth’s surface via reaction with water, air, or 

dissolved substances; commonly results in a change in 

chemical composition more stable in the current 

environment.

clast. An individual grain or rock fragment in a 

sedimentary rock, produced by the physical 

disintegration of a larger rock mass.

clastic. Describes rock or sediment made of fragments of 

pre-existing rocks (clasts).

clay. Can be used to refer to clay minerals or as a 

sedimentary fragment size classification (less than 

1/256 mm [0.00015 in]).
GRTE Geologic Resources Inventory Report 43

claystone. Lithified clay having the texture and 

composition of shale but lacking shale’s fine layering 

and fissility (characteristic splitting into thin layers).

colluvium. A general term applied to any loose, 

heterogeneous, and incoherent mass of rock fragments 

deposited by unconcentrated surface runoff or slow 

continuous downslope creep, usually collecting at the 

base of gentle slopes or hillsides.

conglomerate. A coarse-grained, generally unsorted, 

sedimentary rock consisting of cemented, rounded 

clasts larger than 2 mm (0.08 in).

conodont. One of a small number of small, disjunct fossil 

elements assigned to the order Conodontophorida, 

phosphatic in composition, and commonly toothlike 

in form but not in function; produced in bilaterally 

paired, serial arrangement by small marine animals of 

uncertain affinity. Range—Cambrian (possibly Late 

Precambrian) to Upper Triassic.

continental shield. A continental block of Earth’s crust 

that has remained relatively stable over a long period 

of time and has undergone minor warping compared 

to the intense deformation of bordering crust.

coquina. Limestone composed of cemented shell 

fragments.

country rock. The rock surrounding an igneous intrusion 

or pluton. Also, the rock enclosing or traversed by a 

mineral deposit.

craton. The relatively old and geologically stable interior 

of a continent (also see “continental shield”).

creep. The slow, imperceptible downslope movement of 

mineral, rock, and soil particles under gravity.

crust. Earth’s outermost compositional shell, 10 to 40 km 

(6 to 25 mi) thick, consisting predominantly of 

relatively low-density silicate minerals.

crystalline. Describes a regular, orderly, repeating 

geometric structural arrangement of atoms.

cycad. An ancient group of extant seed plants that 

flourished during the Jurassic, characterized by a large 

crown of compound leaves and a stout trunk; 

resembles palms or ferns in appearance, but is 

unrelated to either.

dacite. A fine-grained extrusive igneous rock similar to 

andesite but with less calcium-plagioclase minerals and 

more quartz.

deformation. A general term for the processes of faulting, 

folding, and shearing of rocks as a result of various 

Earth forces such as compression (pushing together) 

and extension (pulling apart).

devitrification. Conversion of glass to crystalline 

material.

diabase. An intrusive igneous rock consisting primarily 

of the minerals labradorite and pyroxene.

diatom. A microscopic, single-celled alga that secretes 

walls of silica, called frustules. Diatoms live in 

freshwater or marine environment.

differential erosion. Erosion that occurs at irregular or 

varying rates, caused by differences in the resistance 

and hardness of surface material.

dip. The angle between a bed or other geologic surface 

and horizontal.

dip-slip fault. A fault with measurable offset where the 

relative movement is parallel to the dip of the fault.

dolomite. A carbonate sedimentary rock of which more 

than 50% by weight or by areal percentages under the 

microscope consists of the mineral dolomite (calciummagnesium carbonate).

drainage basin. The total area from which a stream 

system receives or drains precipitation runoff.

drift. All rock material (clay, silt, sand, gravel, boulders) 

transported by a glacier and deposited directly by or 

from the ice, or by running water emanating from a 

glacier.

escarpment. A steep cliff or topographic step resulting 

from vertical displacement on a fault or by mass 

movement. Also called a “scarp.”

extrusive. Describes molten (igneous) material that has 

erupted onto Earth’s surface.

facies (metamorphic). The pressure and temperature 

conditions that result in a particular, distinctive suite 

of metamorphic minerals.

facies (sedimentary). The depositional or environmental 

conditions reflected in the sedimentary structures, 

textures, mineralogy, fossils, etc. of a sedimentary 

rock.

fault. A break in rock along which relative movement has 

occurred between the two sides.

feldspar. A group of abundant (more than 60% of Earth’s 

crust), light-colored to translucent silicate minerals 

found in all types of rocks. Usually white and gray to 

pink. May contain potassium, sodium, calcium, 

barium, rubidium, and strontium along with 

aluminum, silica, and oxygen.

felsic. Describes an igneous rock having abundant lightcolored minerals such as quartz, feldspars, or 

muscovite. Compare to “mafic.”

footwall. The mass of rock beneath a fault surface (also 

see “hanging wall”).

formation. Fundamental rock-stratigraphic unit that is 

mappable, lithologically distinct from adjoining strata, 

and has definable upper and lower contacts.

fracture. Irregular breakage of a mineral; also any break 

in a rock (e.g., crack, joint, or fault).

frost wedging. The breakup of rock due to the 

expansion of water freezing in fractures.

gabbro. A group of dark-colored, intrusive igneous 

rocks. The intrusive equivalent of basalt. 

garnet. A hard mineral that has a glassy luster, often with 

well defined crystal faces, and a variety of colors, dark 

red being characteristic. Commonly found in 

metamorphic rocks.

gastropod. Any mollusk belonging to the class 

Gastropoda, characterized by a distinct head with eyes 

and tentacles and, in most, by a single calcareous shell 

that is closed at the apex, sometimes spiraled, not 

chambered, and generally asymmetrical (e.g., a snail). 

Range—Upper Cambrian to the present. 

geology. The study of Earth including its origin, history, 

physical processes, components, and morphology.

glauconite. A green mineral, closely related to the micas. 

It is an indicator of very slow sedimentation.

glaze. A fired glassy surface on lava features.

granite. An intrusive igneous (plutonic) rock composed 

primarily of quartz and feldspar. Mica and amphibole 

minerals are also common. Intrusive equivalent of 

rhyolite.
44 NPS Geologic Resources Division 

gypsum. The most common sulfate mineral (calcium 

sulfate). Frequently associated with halite and 

anhydrite in evaporites.

hanging wall. The mass of rock above a fault surface 

(also see “footwall”).

hornblende. The most common mineral of the 

amphibole group. Hornblende is commonly black and 

occurs in distinct crystals or in columnar, fibrous, or 

granular forms.

hot spot. A volcanic center that is thought to be the 

surface expression of a rising plume of hot mantle 

material.

igneous. Refers to a rock or mineral that originated from 

molten material; one of the three main classes of 

rocks—igneous, metamorphic, and sedimentary.

ignimbrite. The rock formed by the widespread 

deposition and consolidation of ash flows and nuées 

ardentes. The term includes welded tuff and 

nonwelded but recrystalized ash flows.

intrusion. A body of igneous rock that invades (pushes 

into) older rock. The invading rock may be a plastic 

solid or magma.

joint. A break in rock without relative movement of 

rocks on either side of the fracture surface.

karst topography. Topography characterized by 

abundant sinkholes and caverns formed by the 

dissolution of calcareous rocks.

lagomorph. Any of the order Lagomorpha of gnawing, 

herbivorous mammals having two pairs of incisors in 

the upper jaw one behind the other and comprising 

rabbits, hares, and pikas.

lamination. Very thin, parallel layers.

landslide. Any process or landform resulting from rapid, 

gravity-driven mass movement.

liquefaction. The transformation of loosely packed 

sediment into a more tightly packed fluid mass.

lithology. The physical description or classification of a 

rock or rock unit based on characters such as its color, 

mineral composition, and grain size.

loess. Windblown silt-sized sediment, generally of glacial 

origin.

mafic. Describes dark-colored rock, magma, or minerals 

rich in magnesium and iron. Compare to “felsic.”

magma. Molten rock beneath Earth’s surface capable of 

intrusion and extrusion. 

mantle. The zone of Earth’s interior between the crust

and core.

marl. An unconsolidated deposit commonly with shell 

fragments and sometimes glauconite consisting chiefly 

of clay and calcium carbonate that formed under 

marine or freshwater conditions.

mass wasting. A general term for the downslope 

movement of soil and rock material under the direct 

influence of gravity.

maximum credible earthquake. The largest hypothetical 

earthquake that may be reasonably expected to occur 

along a given fault.

meander. Sinuous lateral curve or bend in a stream 

channel. An entrenched meander is incised, or carved 

downward into the surface of the valley in which a 

meander originally formed. The meander preserves its 

original pattern with little modification.

member. A lithostratigraphic unit with definable 

contacts; a member subdivides a formation.

meta–. A prefix used with the name of a sedimentary or 

igneous rock, indicating that the rock has been 

metamorphosed.

metamorphic. Describes the process of metamorphism 

or its results. One of the three main classes of rocks—

igneous, metamorphic, and sedimentary.

metamorphism. Literally, a change in form. 

Metamorphism occurs in rocks through mineral 

alteration, formation, and/or recrystallization from 

increased heat and/or pressure.

mica. A prominent rock-forming mineral of igneous and 

metamorphic rocks. It has perfect basal cleavage 

meaning that it forms flat sheets.

migmatite. Literally, “mixed rock” with both igneous 

and metamorphic characteristics due to partial melting 

during metamorphism.

mineral. A naturally occurring, inorganic crystalline solid 

with a definite chemical composition or compositional 

range.

moraine. A mound, ridge, or other distinct accumulation 

of unsorted, unstratified glacial drift, predominantly 

till, deposited by glacial ice movement.

muscovite. A mineral of the mica group. It is colorless to 

pale brown and is a common mineral in metamorphic 

rocks such as gneiss and schist, igneous rocks such as 

granite, pegmatite, and sedimentary rocks such as 

sandstone.

neoglacial. Describes the period of glacial readvance 

during the late Holocene, the most recent being the 

Little Ice Age (from the 1500s until the mid 1800s).

normal fault. A dip-slip fault in which the hanging wall 

moves down relative to the footwall.

nuée ardente. A swiftly flowing, turbulent gaseous cloud, 

sometimes incandescent, erupted from a volcano and 

containing ash and other pyroclastic materials in its 

lower part.

obsidian. A black or dark-colored volcanic glass, usually 

of rhyolite composition with conchoidal fracture. Can 

be used as a raw material for arrowheads, jewelry, and 

art objects.

oolite. A sedimentary rock, usually limestone, made of 

ooliths—round or oval grains formed by accretion 

around a nucleus of shell fragment, algal pellet, or sand 

grain. These laminated grains can reach diameters of 2 

mm (0.08 in), but 0.5–1 mm (0.02–0.04 in) is common.

orogeny. A mountain-building event.

ostracode. Any aquatic crustacean belonging to the 

subclass Ostracoda, characterized by a two-valved 

(shelled), generally calcified carapace with a hinge 

along the dorsal margin. Most ostracodes are of 

microscopic size.

outcrop. Any part of a rock mass or formation that is 

exposed or “crops out” at Earth’s surface.

outwash. Glacial sediment transported and deposited by 

meltwater streams.

paleontology. The study of the life and chronology of 

Earth’s geologic past based on the fossil record.

parent material. Geologic material from which soils 

form.
GRTE Geologic Resources Inventory Report 45

pegmatite. An exceptionally coarse-grained intrusive 

igneous rock, with interlocking crystals, usually found 

in irregular dikes, lenses, and veins, especially at the 

margins of batholiths.

perlite. A volcanic glass having the composition of 

rhyolite and generally higher water content than 

obsidian; commercially used to form a lightweight 

aggregate (e.g., used in gardening).

phenocryst. A coarse (large) crystal in a porphyritic

igneous rock.

piedmont glacier. A thick, continuous sheet of ice at the 

base of a mountain range on land, formed by spreading 

out and coalescing of valley glaciers from the higher 

elevations of the mountains.

piedmont lake. An oblong lake occupying a partly 

overdeepened basin excavated in rock by, or dammed 

by a moraine of, a piedmont glacier.

pitchstone. A variably colored volcanic glass with a waxy 

dull resinous luster. Contains a higher percentage of 

water than obsidian.

plastic. Capable of being deformed permanently without 

rupture.

pluton (plutonic). A body of intrusive igneous rock that 

crystallized at some depth beneath Earth’s surface.

porphyritic. Describes an igneous rock texture 

characterized by large crystals (phenocrysts) 

surrounded by a finer-grained groundmass (matrix).

pumice. Solidified “frothy” lava. It is highly vesicular and 

has very low density.

pyroclast. An individual particle ejected during a volcanic 

eruption.

regression. A long-term seaward retreat of the shoreline 

or relative fall of sea level.

reverse fault. A contractional high-angle (greater than 

45°

) dip-slip fault in which the hanging wall moves up 

relative to the footwall (also see “thrust fault”).

rhyolite. A group of extrusive volcanic rocks, typically 

porphyritic and commonly exhibiting flow texture, 

with phenocrysts of quartz and alkali feldspar in a 

glassy to cryptocrystalline groundmass. The finegrained extrusive equivalent of granite.

rock. A solid, cohesive aggregate of one or more minerals.

rodent. Any of the order Rodentia of relatively small, 

gnawing animals (as a mouse, squirrel, or beaver) that 

have in both jaws a single pair of incisors with a chiselshaped edge.

roundstone. Any naturally rounded rock fragment larger 

than a sand grain.

sand. A clastic particle smaller than a granule and larger 

than a silt grain, having a diameter in the range of 1/16 

mm (0.0025 in) to 2 mm (0.08 in).

sandstone. Clastic sedimentary rock of predominantly 

sand-sized grains.

scarp. A steep cliff or topographic step resulting from 

displacement on a fault, or by mass movement, or 

erosion. Also called an “escarpment.”

scoria. A bomb-size pyroclast that is irregular in form and 

generally very vesicular.

scour. The powerful and concentrated clearing and 

digging action of flowing air, water, or ice.

sediment. An eroded and deposited, unconsolidated 

accumulation of rock and mineral fragments.

sedimentary rock. A consolidated and lithified rock 

consisting of clastic and/or chemical sediment(s). One 

of the three main classes of rocks—igneous, 

metamorphic, and sedimentary.

seiche. An oscillation of a body of water in an enclosed or 

semi-enclosed basin that varies in period, depending 

on the physical dimensions of the basin, from a few 

minutes to several hours, and in height from several 

centimeters to a few meters. It is caused chiefly by local 

changes in atmospheric pressure, aided by winds, tidal 

currents, and occasionally earthquakes. 

sequence. A major informal rock-stratigraphic unit that 

is traceable over large areas and defined by a sediments 

associated with a major sea level transgressionregression.

shale. A clastic sedimentary rock made of clay-sized 

particles that exhibit parallel splitting properties.

sill. An igneous intrusion that is of the same orientation 

as the surrounding rock.

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay (1/256 to 

1/16 mm [0.00015 to 0.002 in]).

siltstone. A variably lithified sedimentary rock composed 

of silt-sized grains.

slope. The inclined surface of any geomorphic feature or 

measurement thereof. Synonymous with “gradient.”

slump. A generally large, coherent mass movement with a 

concave-up failure surface and subsequent backward 

rotation relative to the slope.

soil. Surface accumulation of weathered rock and 

organic matter capable of supporting plant growth and 

often overlying the parent material from which it 

formed.

speleothem. Any secondary mineral deposit that forms in 

a cave.

spring. A site where water issues from the surface due to 

the intersection of the water table with the ground 

surface.

strata. Tabular or sheet-like masses or distinct layers of 

rock.

stratigraphy. The geologic study of the origin, 

occurrence, distribution, classification, correlation, 

and age of rock layers, especially sedimentary rocks.

stratovolcano. A volcano that is constructed of 

alternating layers of lava and pyroclastic deposits, 

along with abundant dikes and sills.

stream. Any body of water moving under gravity flow in 

a clearly confined channel.

stream channel. A long, narrow depression shaped by the 

concentrated flow of a stream and covered 

continuously or periodically by water.

stream terrace. Step-like benches surrounding the 

present floodplain of a stream due to dissection of 

previous flood plain(s), stream bed(s), and/or valley 

floor(s).

structural geology. The branch of geology that deals with 

the description, representation, and analysis of 

structures, chiefly on a moderate to small scale. The 

subject is similar to tectonics, but the latter is generally 

used for the broader regional or historical phases.

structure. The attitude and relative positions of the rock 

masses of an area resulting from such processes as 

faulting, folding, and igneous intrusions.
46 NPS Geologic Resources Division 

subbituminous. A black coal, intermediate in rank 

between lignite and bituminous coal. It is distinguished 

from lignite by higher carbon and lower moisture 

content. 

subduction zone. A convergent plate boundary where 

oceanic lithosphere descends beneath a continental or 

oceanic plate and is carried down into the mantle.

subsidence. The gradual sinking or depression of part of 

Earth’s surface.

talus. Rock fragments, usually coarse and angular, lying 

at the base of a cliff or steep slope from which they 

have been derived.

tectonic. Relating to large-scale movement and 

deformation of Earth’s crust.

terrace. A relatively level bench or steplike surface 

breaking the continuity of a slope (also see “stream 

terrace”).

terrane. A large region or group of rocks with similar 

geology, age, or structural style.

thrust fault. A contractional dip-slip fault with a 

shallowly dipping fault surface (less than 45°

) where 

the hanging wall moves up and over relative to the 

footwall.

tonalite. A type of plutonic (intrusive) rock.

topography. The general morphology of Earth’s surface, 

including relief and locations of natural and 

anthropogenic features.

trace (fault). The exposed intersection of a fault with 

Earth’s surface.

trace fossil. Tracks, trails, burrows, coprolites (dung),

etc., that preserve evidence of organisms’ life activities, 

rather than the organisms themselves.

transgression. Landward migration of the sea as a result 

of a relative rise in sea level.

travertine. A limestone deposit or crust, often banded, 

formed from precipitation of calcium carbonate from 

saturated waters, especially near hot springs and in 

caves.

trend. The direction or azimuth of elongation of a linear 

geologic feature.

trilobite. Any marine arthropod belonging to the class 

Trilobita, characterized by a three-lobed ovoid outer 

skeleton, divided lengthwise into axial and side regions 

and transversely into cephalon (“head”), thorax 

(middle), and pygidium (“tail”). Range—Lower 

Cambrian to Permian.

tufa. A chemical sedimentary rock composed of calcium 

carbonate, formed by evaporation as an incrustation 

around the mouth of a spring, along a stream, or 

exceptionally as a thick, concretionary deposit in a 

lake or along its shore. It may also be precipitated by 

algae or bacteria. A hard, dense variety of travertine. 

tuff. Generally fine-grained, igneous rock formed of 

consolidated volcanic ash.

ultramafic. Describes rock composed chiefly of mafic 

(dark-colored, iron and magnesium rich) minerals.

unconformity. An erosional or non-depositional surface 

bounded on one or both sides by sedimentary strata.

An unconformity marks a period of missing time.

uplift. A structurally high area in the crust, produced by 

movement that raises the rocks.

vitrophyre. A porphyritic igneous rock with a glassy 

matrix.

volcanic. Describes anything related to volcanoes. Can 

refer to igneous rock crystallized at or near Earth’s 

surface (e.g., lava).

volcanic arc. A commonly curved, linear, zone of 

volcanoes above a subduction zone. 

vug. A small cavity in a vein or in rock, usually lined with 

crystals of a different mineral composition from the 

enclosing rock.

water table. The upper surface of the saturated zone; the 

zone of rock in an aquifer saturated with water.

weathering. The physical, chemical, and biological 

processes by which rock is broken down.
GRTE Geologic Resources Inventory Report 47

Literature Cited

This section lists references cited in this report. A more complete geologic bibliography is 

available from the National Park Service Geologic Resources Division.

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52 NPS Geologic Resources Division 

Additional References

This section lists additional references, resources, and web sites that may be of use to 

resource managers. Web addresses are current as of September 2010.

Geology of National Park Service Areas

National Park Service Geologic Resources Division 

(Lakewood, Colorado). http://nature.nps.gov/geology/

NPS Geologic Resources Inventory. 

http://www.nature.nps.gov/geology/inventory/gre_pu

blications.cfm

U.S. Geological Survey Geology of National Parks 

(includes 3D photographs). 

http://3dparks.wr.usgs.gov/

Harris, A. G., E. Tuttle, and S. D. Tuttle. 2003. Geology of 

National Parks. Sixth Edition. Kendall/Hunt 

Publishing Co., Dubuque, Iowa, USA.

Kiver, E. P. and D. V. Harris. 1999. Geology of U.S. 

parklands. John Wiley and Sons, Inc., New York, New 

York, USA.

Lillie, R. J. 2005. Parks and plates: The geology of our 

national parks, monuments, and seashores. W.W. 

Norton and Co., New York, New York, USA.

[Geared for interpreters].

NPS Geoscientist-in-the-parks (GIP) internship and 

guest scientist program. 

http://www.nature.nps.gov/geology/gip/index.cfm

Resource Management/Legislation Documents

NPS 2006 Management Policies (Chapter 4; Natural 

Resource Management).

http://www.nps.gov/policy/mp/policies.html#_Toc157

232681

NPS-75: Natural Resource Inventory and Monitoring 

Guideline.

http://www.nature.nps.gov/nps75/nps75.pdf.

NPS Natural Resource Management Reference Manual 

#77: http://www.nature.nps.gov/Rm77/

Geologic Monitoring Manual

R. Young and L. Norby, editors. Geological 

Monitoring. Geological Society of America, Boulder, 

Colorado, USA.

[Website under development]. Contact the Geologic 

Resources Division to obtain a copy.

NPS Technical Information Center (Denver, repository 

for technical (TIC) documents): http://etic.nps.gov/

Geological Survey Websites

Wyoming State Geological Survey.

http://www.wsgs.uwyo.edu/

U.S. Geological Survey. http://www.usgs.gov/

Geological Society of America.

http://www.geosociety.org/

American Geological Institute. http://www.agiweb.org/

Association of American State Geologists.

http://www.stategeologists.org/

Other Geology/Resource Management Tools

Bates, R. L. and J. A. Jackson, editors. American 

Geological Institute dictionary of geological terms.

Third edition. Bantam Doubleday Dell Publishing 

Group, New York, New York, USA.

U.S. Geological Survey National Geologic Map Database 

(NGMDB). http://ngmdb.usgs.gov/

U.S. Geological Survey Geologic Names Lexicon 

(GEOLEX; geologic unit nomenclature and summary).

http://ngmdb.usgs.gov/Geolex/geolex_home.html

U.S. Geological Survey Geographic Names Information 

System (GNIS; search for place names and geographic 

features, and plot them on topographic maps or aerial 

photos). http://gnis.usgs.gov/

U.S. Geological Survey GeoPDFs (download searchable 

PDFs of any topographic map in the United States).

http://store.usgs.gov (click on “Map Locator”).

U.S. Geological Survey Publications Warehouse (many 

USGS publications are available online).

http://pubs.usgs.gov

U.S. Geological Survey, description of physiographic 

provinces. http://tapestry.usgs.gov/Default.html
GRTE Geologic Resources Inventory Report 53

Appendix A: Overview of Digital Geologic Data

The following pages show an overview of the digital geologic data for Grand Teton 

National Park and John D. Rockefeller, Jr. Memorial Parkway. For poster-size PDFs of 

this overview and complete digital data, please see the included CD or visit the Geologic 

Resources Inventory publications website at http://www.nature.nps.gov/geology/

inventory/gre_publications.cfm.



GRTE Geologic Resources Inventory Report 57

Appendix B: Scoping Session Participants

The following is a list of participants from the GRI scoping session for Grand Teton 

National Park and John D. Rockefeller, Jr. Memorial Parkway, held on June 21–22, 

2005. The contact information and e-mail addresses in this appendix may be outdated; 

please contact the Geologic Resources Division for current information. The scoping 

meeting summary was used as the foundation for this GRI report. The original scoping 

summary document is available on the GRI publications website at

http://www.nature.nps.gov/geology/inventory/gre_publications.cfm (accessed July 30, 

2010.

Name Affiliation Position Phone E-mail

Jim Bellamy Grand Teton 

National Park

Deputy 

Superintendent 307-739-3410 jim_bellamy@nps.gov

Tim Connors NPS Geologic

Resources Division Geologist 303-969-2093 tim_connors@nps.gov

Sue ConsoloMurphyGrand Teton 

National Park

Chief of Science and 

Natural Resources 307-739-3481 sue_consolo-murphy@nps.gov

Sid Covington NPS Geologic 

Resources Division Geologist 303-969-2154 sid_covington@nps.gov

Richard 

Easterbrook

Grand Teton 

National Park GIS Specialist 307-739-3493 richard_easterbrook@nps.gov

Alice Hart Grand Teton 

National Park Curation Specialist 307-739-3494 alice_hart@nps.gov

Cheryl 

Jaworowski

Yellowstone 

National Park Geologist 307-344-2208 cheryl_jaworowski@nps.gov

Cathie Jean

NPS Greater 

Yellowstone 

Network

Network Coordinator 406-994-7530 cathie_jean@nps.gov

Susan O’Ney Grand Teton 

National Park Hydrologist 307-739-3666 susan_o’ney@nps.gov

Ken Pierce U.S. Geological 

Survey Geologist 406-994-5085 kpierce@usgs.gov

Melanie 

Ransmeier

NPS Geologic 

Resources Division GIS Specialist 303-969-2315 melanie_ransmeier@nps.gov

Jack Reed U.S. Geological 

Survey Geologist 303-236-1276 jreed@usgs.gov

Bob Smith University of Utah Geophysicist 801-557-2239 r.smith@earth.utah.gov

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