National Park Service

U.S. Department of the Interior

Natural Resource Stewardship and Science

Ozark National Scenic Riverways

Geologic Resources Inventory Report

Natural Resource Report NPS/NRSS/GRD/NRR—2016/1307
ON THE COVER: Mineral-laden waters emerge at Blue Spring along the Current River. High dissolved solids in the 

spring water lend a brilliant blue color to the water in sunlight. National Park Service photograph by Alianora 

Walker (Ozark National Scenic Riverways).

THIS PAGE: Steep bluffs of the Roubidoux Formation fronting the Jacks Fork. Photograph by J. Sigler (Creative 

Commons Attribution 2.0 [CC by 2.0] Generic License) available at https://commons.wikimedia.org/wiki/

Category:Ozark_National_Scenic_Riverways (accessed 11 November 2015).
Ozark National Scenic Riverways

Geologic Resources Inventory Report

Natural Resource Report NPS/NRSS/GRD/NRR—2016/1307

Trista L. Thornberry-Ehrlich

Colorado State University Research Associate

National Park Service Geologic Resources Division

Geologic Resources Inventory

PO Box 25287

Denver, CO 80225

September 2016

U.S. Department of the Interior

National Park Service

Natural Resource Stewardship and Science 

Fort Collins, Colorado
ii

The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a 

range of reports that address natural resource topics. These reports are 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 comprehensive information and analysis about natural 

resources and related topics concerning lands managed by the National Park Service. The series supports the 

advancement of science, informed decision-making, and the achievement of the National Park Service mission. The 

series also provides a forum for presenting more lengthy results that may not be accepted by publications with page 

limitations.

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. 

This report is available from the Geologic Resources Inventory website (http://go.nps.gov/gripubs), and the Natural 

Resource Publications Management website (http://www.nature.nps.gov/publications/nrpm/). To receive this report in 

a format optimized for screen readers, please email irma@nps.gov.

Please cite this publication as:

Thornberry-Ehrlich, T. L. 2016. Ozark National Scenic Riverways: Geologic Resources Inventory report. Natural 

Resource Report NPS/NRSS/GRD/NRR—2016/1307. National Park Service, Fort Collins, Colorado.

NPS 614/134533, September 2016
iii

Contents

Page

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Products and Acknowledgments . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

GRI Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

Geologic Setting and Significance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Park Establishment and Landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Geologic Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Geologic Significance and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Ecosystem Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Geologic Features and Processes . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Current River and Jacks Fork Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Cave and Karst Features and Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Surficial Geologic Map Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Bedrock Weathering and Residuum Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Slope Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Periglacial Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Sedimentary Rock Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Paleontological Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Volcanic Rocks and the Eminence Caldera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Radiometric Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Faults and Fractures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Folds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Geologic Resource Management Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Management Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Flooding and Fluvial Geomorphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Climate Change Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Caves and Associated Landscape Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Ozarks Aquifer and Springs Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Paleontological Resource Inventory, Monitoring, and Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Slope Movement Hazards and Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Seismic Activity Hazards and Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Abandoned Mineral Lands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

External Mineral Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Geologic History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Mesoproterozoic Era (1.6–1.0 billion years ago): Building the Ozark Dome, Volcanism, Deformation, and Erosion . . . . . . . . . . . . . . . . 53

Paleozoic Era (541–252 million years ago): Marine Inundation, Deposition, and Erosion, Assembling Pangaea . . . . . . . . . . . . . . . . . . 56

Mesozoic Era (252 million–66 million years ago): Pangaea Separation, Local Erosion, and Mississippi Embayment Subsidence . . . . . . . . . . 59

Cenozoic Era (the past 66 million years): River Valley Evolution and Ice Age Glaciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Geologic Map Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Geologic Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Source Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

GRI GIS Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

GRI Map Posters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Map Unit Properties Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Use Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
iv

Contents (continued)

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Additional References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

NPS Geologic Resources Division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Geology of NPS Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

NPS Resource Management Guidance and Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Climate Change Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Geological Surveys and Societies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

US Geological Survey Reference Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Appendix A: Scoping Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2001 Scoping Meeting Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2015 Conference Call Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Appendix B: Geologic Resource Laws, Regulations, and Policies . . . . . . . . . . . . . . . . . . . . . . . . . 75

Page

GRI Poster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .in pocket

Map Unit Properties Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .in pocket
v

Figures

Figure 1. Map of Ozark National Scenic Riverways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . in pocket

Figure 2. Map of physiographic provinces in Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Figure 3. Geologic time scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 4. Stratigraphic column. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 5. Cross-sectional illustration of a typical riparian area or floodplain of the Current River. . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 6. Illustration of fluvial processes of meandering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 7. Aerial image of the confluence of the Current River and Jacks Fork.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 8. Graphic of the Alley Spring cave profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 9. Photograph of dissolution conduits forming in the Eminence Dolomite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 10. Illustration of stratigraphy and cave development. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 11. Photographs of speleothems and other bedrock features of Round Spring Cavern . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 12. Photographs of Big Spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 13. Map of spring recharge areas over the surface-water and groundwater basins of the Current River and Jacks Fork . . . . . . . . . 18

Figure 14. Illustration of Alley Spring conduit system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 15. Three-dimensional illustration of karst landscape formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 16. Illustration of sinkhole types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 17. Cross-sectional illustration of Devils Well sinkhole and subterranean lake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 18. Illustrations of slope movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 19. Photograph looking downstream along Jacks Fork east of Jam Up Cave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 20. Illustration of Rocky Falls over rhyolite of Shut-In Mountain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 21 (facing page). Map of Mesoproterozoic Era map units near the confluence of the Jacks Fork and Current rivers . . . . . . . . . . . 31

Figure 22. Illustration of caldera formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Figure 23. Illustrations of fault types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 24. Photographs of flood conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 25. Photograph of gravel bars in the Jacks Fork. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 26. Photographs of eroded streambanks at unauthorized access points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Figure 27. Photographs of erosion along roads and social trails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Figure 28. Probability map of the occurrence of earthquakes with magnitudes greater than 5.0 . . . . . . . . . . . . . . . . . . . . . . . . 50

Figure 29A–C. Illustration of the evolution of the landscape and geologic foundation of Ozark National Scenic Riverways . . . . . . . . . . . 54

Figure 29D–E. Illustration of the evolution of the landscape and geologic foundation of Ozark National Scenic Riverways . . . . . . . . . . . 55

Figure 30. Aerial image of Mesoproterozoic rhyolite knob of the Upper Coot Mountain unit (Ycu) surrounded by Cambrian dolomites . . . . . 56

Figure 31. Paleogeographic maps of North America. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Figure 32. Photograph of unconformity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Page

Tables

Page

Table 1. Clastic sedimentary rock classification and characteristics. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 2. Volcanic rocks classification and relative characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 3. Seismic scale and list of notable earthquakes that affected the park and surrounding area. . . . . . . . . . . . . . . . . . . . . . . . 49

Table 4. GRI GIS data layers for Ozark National Scenic Riverways (ozar_geology.mxd; ozar_geology.kmz). . . . . . . . . . . . . . . . . . . . . 62

vii

Executive Summary

The Geologic Resources Inventory (GRI) provides geologic map data and pertinent geologic 

information to support resource management and science-informed decision making in more than 270 

natural resource parks throughout the National Park System. The GRI is one of 12 inventories funded 

by the National Park Service (NPS) Inventory and Monitoring Program. The Geologic Resources 

Division of the NPS Natural Resource Stewardship and Science Directorate administers the GRI.

This report synthesizes discussions from a scoping meeting held in 2001 and a follow-up conference 

call in 2015 (see Appendix A). Chapters of this report discuss the geologic setting, distinctive geologic 

features and processes within Ozark National Scenic Riverways, highlight geologic issues facing 

resource managers, describe the geologic history leading to the present-day landscape, and provide 

information about the previously completed GRI map data. Posters (in pocket) illustrate these data. 

The Map Unit Properties Table (in pocket) summarizes report content for each geologic map unit. 

Soaring bluffs and cliffs; free-flowing rivers; cold, clearblue springs; vast caverns, and rolling, forested uplands 

are the heart of Ozark National Scenic Riverways—the 

first designated national riverway. Authorized on August 

27, 1964 and dedicated on June 10, 1972, the long and 

linear park protects the natural, Ozark cultural, and 

recreational resources along 216 km (134 mi) of the 

Current River and Jacks Fork. The rivers are the primary 

natural resources in the park, followed by springs, caves 

and karst features, bedrock bluffs, riparian zones, and 

rugged uplands. 

Ozark National Scenic Riverways—hereafter referred to 

as “the park”—is part of a dissected karst plain on the 

Salem Plateau within the Ozark Plateaus physiographic 

province. The rivers and their tributaries cut through 

layers of soluble sedimentary rock punctuated by 

knobs of older, volcanic rock and create a landscape of 

picturesque low mountains, rolling hills, hollows, and 

bluff-flanked valleys. This landscape reflects where 

longstanding weathering and erosion have acted on 

two different types of bedrock: igneous (mostly 

volcanic) and sedimentary. The older igneous rocks are 

granite and rhyolite formed at the edge of an ancient 

rift via explosive caldera eruptions about 1.5 billion 

years ago. The younger sedimentary rocks, chiefly 

dolomite with minor amounts of quartz sandstone and 

chert, were deposited in an early Paleozoic shallow sea 

about 500 million years ago. 

The park’s karst features are outstanding, including 

one of the world’s largest collection of first magnitude 

springs. The volcanic rocks are relatively insoluble and 

resistant to weathering contrasted with the soluble 

carbonate (dolomite) sedimentary rocks. In the soluble 

dolomite, dissolution created a karst landscape with 

myriad caves, sinkholes, and over 400 freshwater 

springs which empty thousands of gallons of cold, clear 

water into the park’s waterways. 

The geologic foundation of the park supports a vast 

and varied ecosystem with habitats ranging from 

forested uplands, caves, springs, and riparian zones. 

The geologic foundation has also influenced human 

history, from pre-contact American Indians who left 

a rich archeological record, to logging and resource 

extraction in the late 1800s, through the modern era of 

recreational land use.

This GRI report was written for resource managers 

to support science-informed decision making. It 

may also be useful for interpretation. The report was 

prepared using available geologic information, and 

the NPS Geologic Resources Division conducted no 

new fieldwork in association with its preparation. This 

report is supported by GRI-compiled GIS geologic map 

of the park and surrounding areas. The US Geological 

Survey produced the data used to create the GRI GIS 

data set (Weary et al. 2014 and 2016). The Geologic 

Map Data chapter of this report contains additional 

information about the map and GIS data.

Geologic features and processes include the following:

● Current River and Jacks Fork Systems. The park’s 

rivers are largely spring fed, which helps stabilize

water levels and maintain a robust baseline flow

despite regional climate change. Warm season
viii

water temperatures are relatively low. Fluvial 

features include meandering channels, gravel bars, 

low and high floodplains, and low terraces or 

uplands. These landforms are maintained through 

differential erosion and deposition that accompany 

past and contemporary floods.

● Cave and Karst Features and Processes.

Caves, sinkholes, losing streams, and springs are

prominent karst features at the park. Karst features

form where, over time, soluble rocks, flowing

groundwater, and a suitable gradient act in concert

to dissolve solid bedrock. Bedrock features such as

bedding planes and cracks control, in part, the

location and nature of cave and karst features. At

least 402 caves exist within the park. The caves

exhibit beautiful formations called speleothems.

The park’s springs are world class in terms of sheer

number, discharge, and water quality. Spring

recharge areas bring in water from kilometers away

through an underground network of conduits. The

largest springs are Big, Alley, Blue, Round, Pulltite,

and Welch springs. Sinkholes, formed either through

slow subsidence or sudden collapse, are common

along the Jacks Fork corridor. Streams that lose the

bulk of their surficial flow to underground drainages

are called losing streams. Many kilometers of

designated losing streams exist in the Current River

watershed.

● Surficial Geologic Map Units. Unconsolidated

surficial deposits flank most of the river and stream

valleys within the park. They record the most recent

chapter of the park’s geologic history. Earth surface

processes of erosion and weathering formed these

surficial deposits. In areas where the Gunter

Sandstone member of the Gasconade Dolomite or

the basal sandstone of the Roubidoux Formation

are exposed, their differential resistance to erosion

resulted in topographic benches on hillsides, small

waterfalls, and streams “perched” on the sandstone.

● Bedrock Weathering and Residuum Formation.

Long-term weathering of bedrock can produce

residuum—a distinctive remnant or residual

material left behind after the bedrock has eroded

completely away. This residuum commonly includes

large clasts of more or less intact bedrock parent

material in a clay- and sand-rich matrix.

● Slope Movements. Mapped deposits of colluvium

and talus mark areas that experienced slope

movements or the downslope transfer of earth

material. These areas may have the potential for

future slope failures. Differential weathering 

created steep slopes and unconsolidated material. 

In areas where resistant blocks of sandstone were 

undercut by dissolution of carbonate rocks, rockfall 

hazards exist.

● Periglacial Features. Periglacial features form

at the margins of glaciers under the influence of

cold temperatures. Pleistocene glacial events and

the accompanying cold global climate profoundly

affected the Ozark landscape by accelerating frost

weathering. Frost weathering occurs when

repeated freezing and expanding of water within

rocks or minerals wedges the rocks apart. Other

periglacial features in the park include slope

deposits and wind-blown glacial loess.

● Sedimentary Rock Features. The Paleozoic 

bedrock within the park is sedimentary and

features relatively flat, undeformed bedding.

Bedding becomes inclined near knobs of older,

volcanic rocks that were islands during deposition

of the sedimentary rocks. Sedimentary features

within the rocks such as fossiliferous chert, oolites,

and orthoquartzite provide clues about the original

depositional environment and the history of the

rocks since deposition.

● Paleontological Resources. The shallow seas that

accumulated the park’s sedimentary bedrock were

filled with life during the Cambrian and Ordovician

periods. This ancient life is now preserved as fossils

in the park. Fossils are visible on cave walls and in

loose blocks of rock and bedrock exposures along

the river corridors. More recent, Pleistocene fossils

are preserved in cave sediments. Park fossils are

also found in cultural contexts at archeological

sites.

● Volcanic Rocks and the Eminence Caldera. The 

volcanic rocks at the park are primarily rhyolites

that were erupted during violent volcanism

associated with the Eminence caldera. Collapse of

the volcano caused some units to be tilted and later

volcanism covered these units in untilted layers.

● Radiometric Ages. Radiometric dating methods

compare the abundance of a naturally occurring

radioactive isotope of a mineral with the abundance

of its decay products, which form at a known

constant rate of decay. Some igneous rocks in

the park are dated, but additional dates would give

geologists valuable information about the

Mesoproterozoic (more than 1 billion years ago)

geologic history of the park.
ix

● Faults and Fractures. Faults in the bedrock are

part of the GRI GIS data for the park. Most of

the park’s faults are nearly vertical and probably 

experienced lateral (strike-slip) motion. The

faults are predominantly oriented northeast and

northwest. Faults and through-going fractures

influence groundwater movement in a highly 

permeable karst system.

● Folds. Minor folds—synclines, anticlines, and

monoclines—are included in the park’s GRI GIS

data. At the park, folding occurred near faults

during compression of the rocks or near dissolution

of large voids that are part of the karst landscape.

Geologic resource management issues identified during 

the GRI scoping meeting and follow-up conference call 

include the following:

● Flooding and Fluvial Geomorphology. The park 

was established in part to preserve the Current

River and Jacks Fork as free-flowing streams

whose courses are largely unimpaired by dams

or other control methods. The morphology of

a stream channel is integral to the fluvial and

riparian ecosystem. Human modifications to the

streambanks and floodplains have altered the

natural system, affecting discharge, sediment supply,

and erosional resistance of the banks. The riparian

zones are among the most disturbed ecosystems in

the park. Seasonal flooding is a natural process in

the riparian corridor, but also threatens some park

infrastructure.

● Climate Change Impacts. Climate change may 

impact fluvial processes; models predict increased

temperatures and frequency of strong storms.

This may increase water temperature, sediment

load, and channel morphology thereby affecting

dependent ecosystems.

● Caves and Associated Landscape Management.

Caves are nonrenewable resources and integral

to the park’s landscape. Caves also pose specific

resource management challenges including

sinkhole flooding and collapse, cave breakdown,

radon, vandalism and dumping, white-nose

syndrome in bats, and slippery surfaces, precipitous

drops, and drowning hazards. Cave breakdown is

a natural process by which cave ceilings or walls

collapse. Sinkholes occur throughout the park

and are part of the GRI GIS data. Some mapped

units and geologic settings are more susceptible

to sinkhole formation such as the Gasconade 

Dolomite over the Eminence Dolomite. Because 

of the discovery of white-nose syndrome, all park 

caves, except for guided trips to Round Spring 

Cavern, are closed for recreational entry. Several 

park cave entrances are gated. This restriction limits 

some of the dumping, vandalism, and overuse of 

park caves. The park prepared a cave management 

plan in 2010 to provide strategies for dealing with 

cave-specific issues. 

● Ozarks Aquifer and Springs Protection. The 

Ozarks aquifer is unconfined and supplies water to 

the park’s many springs. Groundwater at the park 

travels up to 5 km (3 mi) per day. Because

of the characteristically high infiltration rates

and permeability of karst landscapes, little to no

adsorption of any surficial contaminants occurs in

karst-forming rocks. Therefore, in order to protect

the park’s springs, the aquifer recharge areas should

also be protected, delineated, and studied; land use 

changes in adjacent areas should be carefully 

monitored.

● Erosion. The construction of roads, trails, parking

lots, and other infrastructure; logging of forests with 

subsequent agricultural development; and human 

impacts from foot traffic, vehicles, and domestic 

animals can increase erosion throughout the park. 

Erosion can increase sediment load in streams 

which in turn can cause enhanced channel

meandering.

● Paleontological Resource Inventory, Monitoring,

and Protection. Theft and erosion threaten fossils 

from the park. All paleontological resources are 

nonrenewable and subject to science-informed 

inventory, monitoring, protection, and

interpretation. To achieve this goal, a field-based,

park-specific paleontological resource survey could

be completed for the park.

● Slope Movement Hazards and Risks. The park’s 

steep river bluffs, fractured rocks, and processes of 

erosion and weathering have created a settingwhere 

slope movements are possible. Slope deposits such 

as colluvium and landslide deposits mark areas most 

prone to natural slope movements.

● Seismic Activity Hazards and Risks. The park 

experiences infrequent earthquakes, including one

in October 2015. The park’s proximity to the New

Madrid Seismic Zone should be an item of concern.

Ground shaking could damage park infrastructure 
x

including bridges and building foundations, as 

well as delicate cave formations. 

● Abandoned Mineral Lands. The park has one

listed abandoned mineral lands feature—the

Partney dolomite quarry. This feature is 

considered historic. Other abandoned mineral

lands may exist within the park, but have yet to be

catalogued.

● External Mineral Development. The park is near

active lead and zinc mines within the Viburnum

Trend. Pumping associated with mining practices

could affect groundwater quantity nourishing

the springs. Additionally, further exploration for

mineral resources occurs on lands adjacent to the

park, including Mark Twain National Forest and the

Eleven Point River area.
xi

Products and Acknowledgments

The NPS Geologic Resources Division partners with the Colorado State University Department of 

Geosciences to produce GRI products. The US Geological Survey developed the source maps and 

reviewed GRI content. This chapter describes GRI products and acknowledges contributors to this 

report.

GRI Products

The GRI team undertakes three tasks for each park in 

the Inventory and Monitoring program: (1) conduct a 

scoping meeting and provide a summary document, 

(2) provide digital geologic map data in a geographic

information system (GIS) format, and (3) provide a GRI

report (this document). These products are designed

and written for nongeoscientists.

Scoping meetings bring together park staff and geologic 

experts to review and assess available geologic maps, 

develop a geologic mapping plan, and discuss geologic 

features, processes, and resource management issues 

that should be addressed in the GRI report. Following 

the scoping meeting, the GRI map team converts the 

geologic maps identified in the mapping plan to GIS 

data in accordance with the GRI data model. After the 

map is completed, the GRI report team uses these data, 

as well as the scoping summary and additional research, 

to prepare the GRI report. The GRI team conducts no 

new field work in association with their products.

The compilation and use of natural resource 

information by park managers is called for in the 1998 

National Parks Omnibus Management Act (§ 204), 2006 

National Park Service Management Policies, and the 

Natural Resources Inventory and Monitoring Guideline 

(NPS-75). The “Additional References” chapter and 

Appendix B provide links to these and other resource 

management documents and information.

Additional information regarding the GRI, including 

contact information, is available at http://go.nps.gov/gri. 

The current status and projected completion dates of 

products are available at http://go.nps.gov/gri_status.

Acknowledgments

The GRI team thanks the participants of the 2001 

scoping meeting and 2015 conference call (see 

Appendix A) for their assistance in this inventory. 

Jonathan Beard (Springfield Plateau Grotto of the 

National Speleological Society), Justin Tweet (NPS 

Geologic Resources Division), and Scott House (Cave 

Research Foundation) provided additional information.

Review

David Weary (US Geological Survey)

Kimberly Houf (NPS Ozark National Scenic Riverways)

Victoria Grant (NPS Ozark National Scenic Riverways)

Jason Kenworthy (NPS Geologic Resources Division)

Dale Pate (NPS Geologic Resources Division)

Editing

Rebecca Port (NPS Geologic Resources Division)

Report Formatting and Distribution

Jason Kenworthy (NPS Geologic Resources Division)

Rebecca Port (NPS Geologic Resources Division)

Source Maps

David Weary, Randall Orndorff, Richard Harrison, and 

Robert Weems (US Geological Survey)

GRI Digital Geologic Data Production

Derek Witt (Colorado State University)

Stephanie O’Meara (Colorado State University)

GRI Poster Design

Chase Winters (Colorado State University)

Georgia Hybels (Colorado State University)

GRI Poster Editing

Georgia Hybels (Colorado State University)

Rebecca Port (NPS Geologic Resources Division)

Jason Kenworthy (NPS Geologic Resources Division)

1

Geologic Setting and Significance

This chapter describes the regional geologic setting of the park and summarizes connections among 

geologic resources, other park resources, and park stories.

Park Establishment and Landscape

Ozark National Scenic Riverways encompasses a 

landscape of picturesque rivers, low mountains, rolling 

hills, hollows, and bluff-flanked valleys in southeastern 

Missouri. The landscape contains spectacular karst 

features including some of the nation’s—and world’s—

largest springs. Caves and sinkholes are other classic 

karst features prominent in the park. 

In the 1940s, the US Army Corps of Engineers 

suggested the Current River and Jacks Fork valleys 

were ideally located for a dam (White 1985). Following 

public outcry and a lengthy campaign, Ozark National 

Scenic Riverways was authorized on 27 August 1964 

and dedicated on 10 June 1972 as the first designated 

national scenic riverway “for the purpose of conserving 

and interpreting unique scenic and other natural values 

and objects of historic interest, including preservation 

of portions of the Current River and the Jacks Fork 

in Missouri as free-flowing streams, preservation 

of springs and caves, management of wildlife, and 

provisions for use and enjoyment of the outdoor 

recreation resources” (Public Law 88-492). The park’s 

mission is to protect the natural, Ozark cultural, and 

recreational resources along 216 km (134 mi) of riverine 

corridor through Shannon, Carter, Dent, and Texas 

counties in southeastern Missouri. About 1.5 million 

visitors come to the park each year (National Park 

Service 2015). 

The Current River and Jacks Fork are the primary fluvial 

(riverine) resources at the park, lending to its sideways 

Y-shaped boundary (fig. 1, in pocket), but many smaller

tributaries are also important throughout the nearly 

32,800 ha (81,000 ac). The park includes the Current

River corridor from Montauk State Park, near Salem,

Missouri on the northwest, to the Ripley County line at

the southeast end, and along the Jacks Fork from near

the community of Mountain View northeast, to the

confluence with the Current River. The rivers meander

through the Courtois Hills, the most rugged landscape

in the Ozarks (Stevens Jr. 1991). Two 6-km (4-mi) gaps

in the park occur along the Current River near Van

Buren and along the Jacks Fork near Eminence.

From its source at the confluence of Pigeon Creek and 

Montauk Springs near Montauk, Missouri, the Current 

River flows approximately 296 km (184 mi) southeast 

to its junction with the Black River near Pocahontas 

in northeast Arkansas. The Current River watershed 

drains a land area of approximately 6,788 km2 (2,621 

mi2) in 11 counties in Missouri and Arkansas. About 

18% of this watershed is the Jacks Fork drainage. The 

park manages less than 3% of the total watershed area 

(Vana-Miller 2007). The confluence of the park’s two 

large rivers is 8 km (5 mi) east-northeast of Eminence, 

Missouri (National Park Service 2015). The Current 

River system, including Jacks Fork, drains the welldeveloped karst terrane along the southeastern margin 

of the Salem Plateau. One hundred and sixty named 

tributaries join the river system; many of these are 

“losing streams,” meaning they are above the water 

table and contribute water to the saturated zone. These 

streams often flow only after rainfall events (VanaMiller 2007). Incision of these drainages has produced 

a relatively steep, rugged topography with local relief 

reaching 50 m (160 ft) or more (Lowell et al. 2010). 

The dissected and forested nature of the region makes 

accessibility a challenge (Lowell et al. 2010). 

Geologic Setting

The landscape in Missouri is divisible into three broad 

physiographic regions from north to south: the Central 

Lowlands, the Ozark Plateaus, and the Coastal Plain 

(fig. 2). The northern and west-central part of Missouri, 

the Central Lowlands, has gently rolling hills and 

broad valleys. It was glaciated during the Pleistocene 

ice ages and still has mantles of glacial deposits over 

the subdued topography (Gillman 2013). The park is 

within the Ozark Plateaus, which includes much of 

central and southern Missouri and covers a broad, 

uplifted region of about 130,000 km2 (50,000 mi2) that

extends into northern Arkansas, southeastern Kansas, 

and northeastern Oklahoma. Thick sequences of 

Paleozoic limestone and dolomite underlie much of the 

plateau and the weathering of these units resulted in the 

characteristic steep-bluffed valleys, large springs, and 

cave networks. In areas of the plateau, ancient volcanic 

rocks punctuate the sedimentary rocks (Gillman 
2

2013). In the extreme southeast corner of Missouri, 

a thick accumulation of fluvial deposits underlies the 

coastal plain. Today, large rivers such as the Mississippi 

continue to build the plain southward into the Gulf of 

Mexico (Gillman 2013). 

Within the Ozark Plateaus province are the Boston 

Mountains (in Arkansas and Oklahoma), the Springfield 

Plateau, and the Salem Plateau (both in Missouri). The 

Eureka Springs escarpment separates the Springfield 

Plateau and the dissected karst plain (see “Cave and 

Figure 2. Map of physiographic provinces in Missouri. Ozark National Scenic Riverways (green-lined area) is within 

the Salem Plateau of the Ozarks Plateaus province. Although during the most recent ice age (Wisconsinan) glacial ice 

did not extend as far south as Missouri, the terminal extent or limit of earlier Pleistocene glaciation is marked by the 

dashed purple line. Bold red lines indicate regional escarpments. The yellow dashed area is the approximate location 

of the Viburnum Trend (a lead and zinc mining district). Graphic by Trista L. Thornberry-Ehrlich (Colorado State 

University) using ESRI ArcMap basemap and information from the Missouri Department of Natural Resources (2002), 

Gillman (2013), and Weary (2015).
3

Karst Features and Processes” section) of the Salem 

Plateau. The park traverses the Salem Plateau which 

is characterized by rolling uplands and rugged hills 

ranging between about 305 and 425 m (1,000 and 1,400 

ft) in elevation with deeply entrenched stream valleys at 

about 155 m (510 ft) in elevation (National Park Service 

2007). 

Three main categories of rock are mapped within and 

surrounding the park (figs. 3 and 4; Weary et al. 2014; 

see also National Park Service 2007 and Lowell et al. 

2010):

● (1) Very old igneous (previously molten) rocks

that are approximately 1.4 billion years old

(Mesoproterozoic Era; “Y” map units). These rocks

formed when magma cooled beneath the surface of

the earth (intrusive igneous rocks such as granite)

or where lava erupted onto the surface by violent

volcanic eruptions (extrusive igneous rocks such

as rhyolite). The oldest igneous rocks are exposed

as subtle, eroded hills. They also form an irregular

bedrock “basement” upon which the younger

sedimentary rocks were deposited.

● (2) Up to 550 m (1,800 ft) of relatively flat-lying

sedimentary rocks about 500 to 470 million years

old (Cambrian and Early Ordovician periods; “C”

and “O” map units) such as dolomite, sandstone,

and chert. Dissolution of the dolomite formed the

caves, sinkholes, springs, and other karst features.

Over 400 freshwater springs—one of the world’s

largest collection of first magnitude springs—empty 

millions of liters of cold, clear water into the park’s

waterways (Vana-Miller 2007; Bowles et al. 2011;

National Park Service 2015).

● (3) Much younger unconsolidated surficial deposits

and accumulations of material derived from deeply 

weathered older bedrock (Quaternary and Tertiary 

periods “Q” and “QT” map units). These rocks

and deposits mostly formed in the past few tens or

hundreds of thousands of years.

Geologic Significance and Connections

The geologic resources at Ozark National Scenic 

Riverways have supported varied human habitats and 

human history for thousands of years. There is a rich 

record of Archaic (8,000 to 1,000 BCE [Before Common 

Era]), Woodland (1,000 BCE to 1000 CE [Common 

Era]), and Mississippian (900 to 1500 CE) archeological 

resources along the Current River (Stevens Jr. 1991). 

Prior to European settlement around 1800, Ozark caves 

sheltered hunter-gatherer American Indians who used 

the caves for shelter and storage and built small villages 

and farms on the river terraces (Panfil and Jacobson 

2001; White 1985). During dry periods, people 

inhabited the lowest floodplains and terraces. During 

wetter times, the higher terraces were favored (Stevens 

Jr. 1991). American Indians used chert for chippedstone dart points and plant collecting tools. Bedrock 

and clay deposits were used to make limestonetempered cord-marked ceramics (Stevens Jr. 1991). By 

the late 1700s, the inhabitants of the Current River 

valley had mostly migrated to larger settlements in the 

lowlands of southeast Missouri and northeast 

Arkansas. The park area was intermittently used for 

hunting until permanent settlement (Stevens Jr. 1991). 

The Spanish were among the earliest European 

explorers to the Ozarks in the 1500s and were looking 

for precious ores. Some lead deposits were uncovered, 

but the region was too remote and isolated to support 

large settlements. Beginning in the 1720s, the famous 

Missouri lead resources (lead-bearing galena is the state 

mineral) were exploited by the French; mining in areas 

such as the Viburnum Trend, north of the park, started 

in the 1950s and continues today (Stevens Jr. 1991; 

Missouri Department of Natural Resources 2016).

Eminence, Missouri was founded and named for 

its elevation; lending its name later to the Eminence 

Dolomite (Ce) upon which it is perched. Both the 

Eminence Dolomite and Gasconade Dolomite (Og) 

contain caves, which are also part of local history 

(Eaton 1918). During the American Civil War, caves 

in the park were used as a source of saltpeter for 

gunpowder (e.g., Powder Mill Cave), a center of 

recuperation (e.g., Hospital Cave), a hiding place for 

town records (e.g., Courthouse Cave), and places to 

hide or seek refuge (White 1985).

After about 1800, European settlers cleared riparian 

areas and floodplains along the Current River and Jacks 

Fork for pasture and row crops, and logged timber 

from valley slopes (Panfil and Jacobson 2001). When 

a railroad reached the area in the 1870s, increased 

logging spawned a population increase between 1880 

and 1920. This clearing of stabilizing vegetation would 

have caused a period of erosion and soil loss in the 

upland, sloped, and floodplain areas (White 1985). The 

fast-moving, larger rivers were used to facilitate the 

transfer of logs from site to mill (Buck et al. 2000). After 
4

Figure 3. Geologic time scale. The divisions of the geologic time scale are organized stratigraphically, with the oldest 

divisions at the bottom and the youngest at the top. GRI map abbreviations for each time division are in parentheses. 

Boundary ages are millions of years ago (MYA). Major geologic events affecting southeast Missouri are highlighted, 

as well as geologic map units that appear within park boundaries. National Park Service graphic using dates from the 

International Commission on Stratigraphy (http://www.stratigraphy.org/index.php/ics-chart-timescale).
5

Figure 4. Stratigraphic column. Ozark National Scenic Riverways includes exposures of ancient volcanic bedrock (“Y” 

geologic map units), early Paleozoic sedimentary rocks (Cp, Ce, Og, Or, and Ojc), and younger, unconsolidated surficial 

deposits (Qa, Qm, Qls, Qc, Qt, Qtl, Ql, and QTg) and weathered bedrock remnants (QTrr, QTtrc, and QTr). Colors are 

standards defined by the US Geological Survey. White dashed lines on photographs represent approximate geologic 

contacts between units. Asterisks indicate units that are not mapped within park boundaries. Graphic by Trista 

L. Thornberry-Ehrlich (Colorado State University) with information from and after figure 2 in Weary et al. (2014).

Photographs are, from top to bottom, cover image from Weary et al. (2014) taken by Victoria Grant (National Park

Service), and figures 3 and 5 from Weary (2015).
6

the timber boom, residents returned to agriculture, 

annually burning upland areas to increase open range 

for grazing (Panfil and Jacobson 2001). The impacts of 

this past land use on the hydrogeologic system at the 

park are not well understood (Buck et al. 2000). 

The karst spring system at the park provided many 

functions for human use including mills (e.g., Alley 

Spring and Mill, Pulltite Spring complex, and Welch 

Spring), fishing resorts (e.g., Pulltite and Welch 

springs), and mineral spa resorts (e.g., Welch Spring) 

(National Park Service 2015). Alley Spring was a Civilian 

Conservation Corps (CCC) work camp for World 

War I veterans in the 1930s (Lowell et al. 2010). CCC 

crews constructed state park facilities at Alley and Big 

springs (White 1985). The crews used local Cambrian or 

Ordovician rocks to construct many of the facilities.

A thorough examination of the park’s cultural resources 

is beyond the scope of this report. Valuable references 

regarding the park’s human history include Stevens Jr. 

(1991), and cultural landscape inventory reports such as 

National Park Service (2013a, 2013b). 

Ecosystem Connections

Ozark National Scenic Riverways is part of the Current 

River Hills ecological subsection with moderately 

rolling to steeply dissected hills associated with the 

major rivers and their tributaries. The geology is karstic 

(see “Cave and Karst Features and Processes” section).

According to National Park Service significance 

statements presented in Vana-Miller (2007), five 

fundamental natural resources are associated with the 

park:

● The high water quality and clarity in the freeflowing Current River and Jacks Fork

● The high density of caves and springs

● The fragile, karst-based hydrogeological system

● A significant diversity of high-quality ecosystems

within the river corridors

● The assemblage of unique plants and animals.

These resources are either purely geologic or have 

strong ties to the geologic foundation of the park. 

Cave environments are relatively stable with regards 

to temperature and humidity, generally have fewer 

food sources, and low biodiversity; nevertheless they 

provide important habitat for a variety of specially 

adapted species (Baker et al. 2015). The constant water 

temperatures and distinctive water chemistry of the 

many karst springs at the park are important for plants 

and sensitive animals not otherwise found in the local 

rivers (Bowles et al. 2011; National Park Service 2015). 

Aquatic plants provide sustenance and habitat for at 

least 38 animal species found only in Ozark springs and 

subterranean waters (Vana-Miller 2007; National Park 

Service 2015). The springs support fish species such as 

sculpins and bleeding shiners that require clean gravel 

and cobble substrates (Bowles et al. 2011). Caves shelter 

cave-obligate species, including the Ozark big-eared bat, 

46 cave-aquatic species, and 31 cave-terrestrial species 

(Vana-Miller 2007; Baker et al. 2015). Many cave species 

are largely unknown due to their small populations, 

restricted ranges, and low rates of reproduction. 

In addition to supporting cave ecosystems, the bedrock 

in the park creates cliffs and ledges for raptors, rockyslope exposures for more than 184 taxa of lichen, and 

open glades that support distinctive plant communities 

at the contacts between rock units (specifically between 

the Eminence Dolomite (Ce), Gasconade Dolomite 

(Og), and Roubidoux Formation (Or) (Weary et al. 

1999; Bennett and Wetmore 2005). The rocky slopes 

provide substrate for native vegetation, mainly oakhickory and oak-shortleaf pine forests and woodlands 

(Buck et al. 2000). Weathering of bedrock gives rise, in 

part, to the development of soils. A detailed soils map

of the park was produced by the NPS Soil Resources 

Inventory and is available at https://irma.nps.gov/App/

Reference/Profile/1048949.

Wetlands within the park include marshes, doline lakes 

(sinkhole ponds), bottomland forests, riparian lowlying areas, and groundwater seeps (Vana-Miller 2007). 

Sinkholes that have collected substantial debris and 

wetland deposits are mapped as “muck” (Qm) in the 

GRI GIS data (Weary et al. 2014). Some of these areas, 

such as Tupelo Gum Pond and Cupola Pond in Mark 

Twain National Forest, support rare flora and fauna 

(Dave Weary, US Geological Survey, geologist, written 

communication, 24 June 2016). Groundwater seeps 

tend to be found at the base of slopes and where 

groundwater contacts an impermeable unit and flows 

horizontally until it emerges at the surface. Alkaline 

groundwater produces seeps called fens, which may 

contain plants more typical of northern states and are 

rare or endangered in Missouri. More than 30 fens are 
7

known from the Current and Jacks Fork watersheds 

(Vana-Miller 2007). Little is known about the size, 

extent, and species composition of the park’s wetlands 

(Vana-Miller 2007). A wetlands inventory study could 

be a potential project for the Geoscientists-in-the-Parks 

program (http://www.nature.nps.gov/geology/gip/).

Riparian habitats are a major natural component of 

the park, and are considered some of the most diverse, 

dynamic, and complex habitats in the terrestrial 

environment (Vana-Miller 2007; National Park Service 

2015). The riparian area encompasses the stream 

channel between low and high water levels meaning it is 

susceptible to floods. Flood frequency, soil and regolith 

characteristics, and elevation above and distance from 

the river channel are important determinants of plant 

species distributions (Buck et al. 2000). Some of the 

more stable riparian and floodplain areas support 

second- and third-growth bottomland hardwood 

forests (Buck et al. 2000). The riparian areas support 

at least 66 woody species of plants and 442 species of 

ground plants (Buck et al. 2000). Cane (Arundinaria

gigantea), a riparian plant that forms canebreaks or 

areas of ground covered with a dense growth of canes, 

was once widespread but is now considered critically 

endangered (Vana-Miller 2007). The watersheds 

provide habitat for 43 species and subspecies of mussels 

(two of which are federally listed as endangered) and 

14 species of crayfish, including the Salem cave crayfish 

(Cambarus hubrichti) which is a species of conservation 

concern (Vana-Miller 2007).

The ancient Ozark highlands is a significant biodiversity 

center in North America with over 200 endemic species 

(Vana-Miller 2007). This diversity is due to the integrity 

and protection of its connected region and the richarray of geology-supported aquatic, terrestrial, and 

subterranean habitats that are concentrated within the 

Current River and Jacks Fork corridors (Vana-Miller 

2007). The Ozarks region may be one of the oldest 

continuously exposed land masses that make up North 

America; it served as refugium for organisms exposed to 

climatic extremes associated with ice ages. In its history, 

it has been a mixing zone of boreal, prairie, desert, 

deciduous forest, and alluvial floodplain ecosystems 

(Vana-Miller 2007).

9

Geologic Features and Processes

These geologic features and processes are significant to the park’s landscape and history.

During the 2001 scoping meeting (see National Park 

Service 2001) and 2015 conference call, participants 

(see Appendix A) identified the following geologic 

features and processes:

● Current River and Jacks Fork Systems

● Cave and Karst Features and Processes

● Surficial Geologic Map Units

● Bedrock Weathering and Residuum Formation

● Slope Movements

● Periglacial Features

● Sedimentary Rock Features

● Paleontological Resources

● Volcanic Rocks and the Eminence Caldera

● Radiometric Ages

● Faults and Fractures

● Folds

Weary et al. (2014) provided a comprehensive 

overview of the geology of the Current River and 

Jacks Fork drainages in a report that accompanies the 

1:100,000-scale map used to develop the GRI GIS data. 

That publication is a key resource to understanding 

the geologic framework of the area, particularly with 

regards to groundwater flow through the karst drainage 

basin. 

Current River and Jacks Fork Systems

Long and linear, Ozark National Scenic Riverways 

encompasses portions of the Jacks Fork and Current 

rivers, two of the three designated Outstanding National 

Resource Waters in Missouri. The Jacks Fork flows 55 

Figure 5. Cross-sectional illustration of a typical riparian area or floodplain of the Current River. Green text refers to 

habitat types associated with each level above the river channel. Soil composition varies with age and distance from 

and above the river. Annual and occasional flood levels are indicated by blue areas. Colors are standard US Geological 

Survey designations for different units of geologic time. Graphic by Trista Thornberry-Ehrlich (Colorado State 

University) adapted from an unnumbered figure in appendix C of Buck et al. (2000).
10

Figure 6. Illustration of fluvial processes of meandering. River meandering creates abandoned channels that infill 

with fine-grained sediments. Floodplain and riparian areas are characteristic landforms of meandering rivers. They 

are visible along the channels of the Current River and Jacks Fork (see also fig. 5). Graphic by Trista Thornberry-Ehrlich 

(Colorado State University) with information from Allen (1964).
11

km (34 mi) through the park at a gradient of 1.8 m/km 

(9.5 ft/mi) and the Current River courses 161 km (100 

mi) at a gradient of 1.12 m/km (5.92 ft/mi). The overall

gradient of their channels is relatively steep compared

to the state average of 0.65 m/km (3.45 ft/mi), creating

swifter currents (Wilson 2001; Vana-Miller 2007). This

also creates the possibility of large, flood-producing

flows accompanying east-moving precipitation systems

(Wilson 2001).

As much as 90% of the flow in the major rivers, streams, 

and tributaries of the system comes from karst springs, 

therefore the drainage system is considered karstic 

(see “Cave and Karst Features and Processes” section); 

it is characterized by dendritic and radial drainages 

(Mugel et al. 2009; Buck et al. 2000). The high input 

from springs creates a relatively stable base flow and 

cool water temperatures (Wilson 2001; Vana-Miller 

2007). Suspended sediment and dissolved minerals 

give the river waters distinctive blue colors. With the 

exception of exposures of Potosi Dolomite (Cp) near 

Eminence-Stegall Mountain and downstream near Van 

Buren, the main channel of the Current River flows 

over Eminence Dolomite (Ce) and Gasconade Dolomite 

(Og) throughout the length of the park (Lowell et al. 

2010; Weary et al. 2014). The Jacks Fork flows over the 

Roubidoux Formation (Or), Gasconade Dolomite (Og), 

Eminence Dolomite (Ce), and Potosi Dolomite (Cp) 

through the map area (Weary et al. 2014). 

Seasonal floods are a major driving force of landscape 

evolution at the park; along the river, landforms are 

maintained through the differential erosion and 

deposition that accompany past and contemporary 

floods (Buck et al. 2000). Typical, yearly floods raise 

water levels on both major rivers from 2 to 3 m (6.5 to 

9.8 ft) above baseflow; 25- to 50-year floods reach 4 to 6 

m (13.1 to 19.7 ft) above baseflow (Jacobson and Primm 

1994; Buck et al. 2000).

The rivers contain typical fluvial landforms such 

as meandering channels, gravel bars, low and high 

floodplains, and low terraces or uplands (figs. 5, 6, 

and 7; Buck et al. 2000). At the park, river channels are 

Figure 7. Aerial image of the confluence of the Current River and Jacks Fork. Both rivers are meandering across their 

floodplains, creating sharp bends and gravel bars on the inside of the bends and near confluences of tributaries. Thick 

red line is the park boundary for Ozark National Scenic Riverways. Graphic by Trista Thornberry-Ehrlich (Colorado State 

University) using ESRI World Imagery basemap (accessed 9 May 2016).
12

gravelly, and are mostly eroding although deposition 

in gravel bars does occur. Gravel and sand bars occur 

within active channels, typically in point bar settings 

along the inside of bends or where tributaries join, and 

may be submerged or emergent. Low floodplains have 

sandy and very gravelly sandy soils, a wavy to smooth 

surface, and flood annually to elevations between 2 

and 5 m (6 and 15 ft) above the active channel. High 

floodplains are characterized by loamy, gravelly loamy, 

and silty soils, smooth to flat surfaces. They flood 

occasionally to elevations between 5 and 10 m (15 and 

30 ft) above the active channel. The surfaces of high 

floodplains are hundreds to thousands of years old 

while low floodplain surfaces can be a few decades to

100 years old. Terraces have distinctive soil 

development, loamy to silty soils, elevated flat surfaces, 

and rarely flood (Buck et al. 2000). They are perched 10 

to 15 m (30 to 45 ft) above the channel and are 

remnants of former floodplains above former activechannel levels, thousands or tens of thousands of years 

ago (Buck et al. 2000). 

Cave and Karst Features and Processes

Caves are naturally occurring underground voids 

such as solutional caves (commonly associated with 

karst), lava tubes, sea caves, talus caves (a void among 

collapsed boulders), regolith caves (formed by soil 

piping), and glacier caves (ice-walled caves) (Toomey 

2009). Karst is a landscape that forms through the 

dissolution of soluble rock, most commonly carbonates 

such as limestone or dolomite (Toomey 2009). Caves, 

sinkholes, “losing streams,” springs, and internal 

drainage are characteristic features of karst landscapes. 

As of July 2016, cave or karst resources are 

documented in at least 160 parks, including Ozark 

National Scenic Riverways. Baker et al. (2015) included 

the park among those in the National Park System that 

contain notable solution caves. According to Land et al. 

(2013), 99% of the park is karst. The NPS Cave and 

Karst website, https://www.nps.gov/subjects/caves/

index.htm, provides more information. Weary and 

Doctor (2014) compiled a karst database for the United 

States; Ozark National Scenic Riverways is mapped in 

the “carbonate rocks at or near the land surface” unit, 

which is typically karst. 

Since 2010, all caves in the park are closed to visitation 

with the exception of guided tours of Round Spring 

Cavern. The closure is to minimize the spread of whitenose syndrome, a fungal disease that has killed millions 

of bats in North America. See the “Geologic Resource 

Management Issues” chapter for more information.

Nearly 7,000 caves have been documented in the state 

of Missouri (Missouri Speleological Survey 2016) 

and more than 402 solution caves are within Ozark 

National Scenic Riverways (Kimberly Houf, terrestrial 

ecologist, Ozark National Scenic Riverways, email, 8 

September 2016). The park ranks first for the greatest 

number of solution caves in a unit of the National Park 

System (statistics compiled by Dale Pate, cave and 

karst program coordinator, NPS Geologic Resources 

Division, 9 September 2016). The caves in the park 

range from simple rock overhangs to extensive, 

networks of passages, including Powder Mill Cave 

with more than 14.2 km (8.8 mi) of mapped passages; 

all together the mapped passages in the park total 45 

km (28 mi) (Scott House, Ozark operations manager, 

Cave Research Foundation, email, 9 September 2016). 

Sixty caves in the park have perennial streams, 33 have 

intermittent water sources, and seven have lakes (VanaMiller 2007). Notable cave examples include Bear 

Cave and Bunker Hill Cave along the Jacks Fork, Devils 

Well near Pulltite, and Round Spring Cavern near the 

crossing of Highway 19 and the Current River. The lake 

in Devils Well Cave is about 122 m (400 ft) long, up to 

15 m (50 ft) wide, and up to 61 m (200 ft) deep—one of 

the largest cave lakes in the country (Vana-Miller 2007). 

Cave divers explored the underground conduit of 

Blue Spring reaches to a depth of at least 90 m (300 ft) 

(National Park Service 2015). More than 900 m (3,000 

ft) of Alley Spring Cave has been mapped by divers (fig. 

8; Ozark Diving Alliance 2005; Lowell et al. 2010). 

The Missouri Speleological Society maintains a 

database (available at http://www.mospeleo.org/) of 

cave information which includes the number of caves in 

the state and cave maps (Crews 2008).

Development of Caves and Karst Features

Caves, sinkholes, losing streams, and springs are 

prominent karst features that formed in the Paleozoicage carbonate bedrock at the park (National Park 

Service 2015). Cave and karst development requires 

four geologic conditions:

● soluble rocks;

● solvent (flowing groundwater);

● hydrogeologic framework (hydraulic gradient); and

● time.
13

Soluble Rocks

First among these conditions is the existence of a 

suitable body of rock, in this case Paleozoic carbonate 

rocks (geologic map units Ojc, Og, Ce, and Cp), which 

occur in flat-lying to gently inclined beds (Hack 1966; 

Weary et al. 2014). Limestone and dolomite are ideal 

for the formation of karst features because they are 

highly soluble in carbonic acid (White 1988). The upper 

Gasconade Dolomite (Og) contains the most caves in 

the park area, with the upper part of the Eminence 

Dolomite (Ce) also containing significant caves (Lowell 

et al. 2010). Caves tend to form beneath sandstone 

layers, with the cave passages trending more or less 

parallel to bedding (Weary and Orndorff 2001; Lowell 

et al. 2010).

Solvent (Groundwater)

The second condition required for extensive cave 

development is the presence of abundant solvent—

acidic groundwater. Located in a temperate climate, 

southern Missouri receives an average of 115.75 cm 

(45.57 in) precipitation per year which provides a 

substantial amount of water to the hydrogeologic 

system (National Weather Service 2015). Cave 

formation occurs below the water table where acidic 

groundwater reacts with carbonate rocks along 

subterranean cracks and fractures (Toomey 2009). Most 

meteoric water is slightly acidic (relatively low pH) due 

to the reaction between atmospheric carbon dioxide 

(CO2

) and water (H2O). The product of this reaction 

is carbonic acid (H2CO3). Groundwater may become 

even more acidic as it flows through decaying plant 

debris and soils. The increased saturation of water with 

carbon dioxide augments the ability of groundwater 

to dissolve limestone and dolomite (White 1988). The 

acid reacts with calcium carbonate (CaCO3

) or dolomite 

(CaMg(CO3)2) in the carbonate rocks to produce 

soluble calcium (Ca2+) or magnesium (Mg2+) and 

bicarbonate (HCO3-) ions. The result is the dissolution 

of carbonate rocks, which are considered to be “in 

solution.”

Anthropogenic sulfur and nitrogen compounds in the 

air contribute to the formation of acid rain, which may 

have a pH of 3.0 or lower. Acid rain has the potential 

to increase the rate of dissolution by approximately 

1,000 times (Volesky 2009). Sullivan (2016) ranked 

the park’s estimated acid pollutant exposure and 

exposure to sulfur and nitrogen emissions as “high.” 

The NPS Air Resources Division provides guidance for 

servicewide air quality monitoring (see http://nature.

nps.gov/air/Monitoring/index.cfm). Ozark National 

Scenic Riverways is not a participating park. The closest 

participating parks are Mammoth Cave National Park 

(Kentucky) and Buffalo National River (Arkansas). Both 

of those parks have similar karst landscapes. Although 

acid rain greatly increases the rate of carbonate rock 

solution, in terms of a human time-scale, it is still a fairly 

slow process.

Hydrogeologic Framework

The third basic element required for cave formation is 

a hydrogeologic framework which provides a sufficient 

hydraulic gradient as well as permeability and porosity 

within the bedrock to allow water to flow through the 

rock. When carbonic acid dissolves soluble bedrock, 

the solution quickly reaches saturation, preventing 

further dissolution. For this reason, a high hydraulic 

gradient, inherent in steep slopes such as those that 

exist between the uplands and the valley floors within 

the Ozark Plateau, must be present to provide sufficient 

Figure 8. Graphic of the Alley Spring cave profile. The western edge of the known cave system is 30 m (100 ft) 

below the spring pool surface. Hydrostatic pressure from a confined aquifer forces the water from depth up to the 

surface to emerge in the spring pool. Regional faults may also facilitate groundwater movement. The cave is in both 

the Eminence Dolomite (Ce) and the Gasconade Dolomite in areas where the Gunter Sandstone member has been 

breached and/or collapsed. Graphic by Trista Thornberry-Ehrlich (Colorado State University) redrafted after figure 6.2 in 

Lowell et al. (2010).
14

energy to rapidly move the solvent through the rock 

(Kuehn et al. 1994). In some cases the solutional 

“aggressiveness” of the groundwater can be rejuvenated 

when dissimilar groundwater masses mix. This mixing 

may be controlled by features in the hydrogeologic 

framework, like fractures and faults. Detailed mapping 

suggests initial dissolution and the beginning of cave 

branching development was controlled by bedding 

planes and stratigraphic variations within the bedrock 

of the Salem Plateau (fig. 9; Orndorff et al. 2006). 

The gentle regional dip of the dolomite layers to the 

southeast, toward the base drainage of the Black River 

(and eventually the Mississippi River), influenced 

groundwater circulation. Because cave passages tended 

to form parallel to bedding, or sedimentary layers 

within the dolomite, the bedding structures may have 

controlled the orientation of cave system formation 

(Hack 1974). 

Caves in the park are either hypogenic or epigenic and 

this relates to their position relative to the sandstone 

layers. Hypogenic caves form in and follow bedrock 

beneath impermeable sandstone layers. They form 

below the water table, possibly under enhanced 

hydrostatic pressure. Epigenic caves, a more common 

type of cave, form in layers above sandstone where 

water flows downward and along the top of an 

impermeable sandstone layer (Vana-Miller 2007). 

Orndorff et al. (2006) suggested the park’s cave 

development is driven by confining conditions beneath 

Figure 9. Photograph of dissolution conduits forming in the Eminence Dolomite. Dissolution of dolomite layers into 

caves and smaller conduits tends to be concentrated in subhorizontal carbonate bedrock below prominent sandstone 

layers such as within the Eminence Dolomite (Ce). As the outcrop slowly weathers away, blocks fall to litter the toe of 

the slope as colluvium or talus. National Park Service photograph courtesy of Alianora Walker; annotation by Trista L. 

Thornberry-Ehrlich (Colorado State University).
15

prominent sandstone layers that occur within the 

Eminence Dolomite (Ce; fig. 10), at the base of the 

Gasconade Dolomite (Og), and within the Roubidoux 

Formation (Or). This setting creates hydrostatic 

pressure that affects the chemistry and solvent strength 

of groundwater (see “Springs” subsection). The contact 

between the Eminence Dolomite (Ce) and the overlying 

Gunter Sandstone member of the Gasconade Dolomite 

(part of Og) is visible at Baptist Camp and perhaps 

most spectacularly, in parts of the Left-Hand Route of 

Round Spring Cavern (Lowell et al. 2010). The contact 

between the Gasconade Dolomite (Og) and Roubidoux 

Formation (Or) may be seen on State Highway 106, 1.2 

km (0.73 mi) west of Alley Spring (Lowell et al. 2010). 

Time

Time is the final condition necessary for the formation 

of extensive cave-passage networks. Karst landscapes 

form through dissolution and erosion, which take 

geologic-scale periods of time (White 1988). Yearly 

dissolution rates are low, but when this is multiplied 

by hundreds of thousands or millions of years, huge 

cavities may form. Eventually, all of the rock will be 

dissolved away to become part of the base level of the 

Current River’s and Jacks Fork’s valleys. At the park, 

groundwater first came into contact with the Jefferson 

City Dolomite (Ojc), the uppermost soluble unit (Weary 

et al. 2014). Over hundreds of thousands of years, 

dissolution occurred among the intergranular pores 

and along fractures in the bedrock, creating voids 

(Ojc, Og, Ce, and Cp) (Crews 2008; Weary et al. 2014). 

Continued dissolution enlarged the voids, culminating 

in the formation of large caverns and extensive springdrainage networks. Dissolution and cavern formation 

continue today (Crews 2008). 

Speleothems

Cave formations or deposits known as speleothems 

may form in passages that are above the water table. 

Lowering of the water table occurs via downcutting 

of surface streams. Groundwater trickling through 

overlying soluble bedrock is saturated with dissolved 

minerals. Upon reaching the air in the cave, it releases 

carbon dioxide (degasses) and the minerals that were 

in solution precipitate out to form dripstones (e.g., 

stalagmites and stalactites) and flowstone (e.g., rimstone 

Figure 10. Illustration of stratigraphy and cave development. Dissolution of dolomite layers into karst features such as 

caves and sinkholes tends to be concentrated in carbonate bedrock below prominent sandstone layers such as within 

the Roubidoux Formation (geologic map unit Or), Gasconade Dolomite (Og), and Eminence Dolomite (Ce). The most 

complex cave networks form beneath the thick Gunter sandstone member at the base of the Gasconade Dolomite. 

The units depicted are also all part of the Ozarks aquifer above an underlying confining unit. Colors are standard US 

Geological Survey designations for different units of geologic time. Graphic by Trista Thornberry-Ehrlich (Colorado 

State University) redrafted after figure 7 in Orndorff et al. (2006).
16

dams, mineral crusts, and draperies; fig. 11). Impurities 

within the solution such as iron, manganese, and 

organic tannins will stain the otherwise white minerals 

into shades of red, orange, brown, gray, and black 

(Crews 2008). 

Caves within the park are well known for their 

speleothems (fig. 11). Since commercial tours began 

in 1932, visitors have marveled at the cave formations 

within Round Spring Cavern (Lowell et al. 2010). 

Speleothems such as stalactites, stalagmites, flowstone, 

Figure 11. Photographs of speleothems and other bedrock features of Round Spring Cavern. Cave formations such as 

these form drip by drip as minerals precipitated out of groundwater exposed to the atmosphere of an underground 

cavern. Round Spring Cavern has been a tourist attraction for decades and is the only cave currently open to visitors 

(guided hikes only). Visitors can damage cave formations and make incremental, but significant changes to the cave 

environment. Photographs by Sid Covington (NPS Geologic Resources Division) taken in February 2002.
17

dripstone, rimstone and rimstone dams, soda straws, 

helictites, and columns are well known from the 

park caves. Speleothems have been vandalized and 

some have been restored (see “Caves and Associated 

Landscape Management” section; National Park 

Service 2015; Jonathan Beard, Springfield Plateau 

Grotto of the National Speleological Society, secretary/

treasurer, written communication, 10 July 2016). Some 

of the speleothems are not common to caves outside the 

park, including spathites (Dave Weary, US Geological 

Survey, geologist, written communication, 21 June 

2016). Spathites are tubular stalactites consisting of 

a vertical succession of overlapping, delicate, petalshaped cones. 

Interest in the park’s speleothems extends to seismic 

studies. During earthquakes, speleothems may be 

broken. Dating these fractures may help determine 

paleoseismicity. Speleothems in Round Spring Cavern 

are being researched for determining when earthquakes 

occurred (Tinsley 2014; Dave Weary, US Geological 

Survey, geologist, written communication, 21 June 

2016). 

Springs

Ozark National Scenic Riverways contains one of the 

world’s largest collection of first magnitude springs, 

defined as those which discharge more than 245 million 

L (65 million gallons) of water daily, among more than 

400 total known springs (Vana-Miller 2007; Bowles et 

al. 2011; National Park Service 2015). The largest of 

these “Jewels of the Ozarks” include Big, Alley, Blue, 

Round, Pulltite, and Welch springs. As one of the largest 

single-orifice karst springs in the world, Big Spring 

(fig. 12) discharges about 1.1 billion L (288 million 

gallons) of water per day and has a peak flow of about 

3 billion L (800 million gallons) per day. Alley Spring 

flows at an average of 307 million L per day (81 million 

gallons). Round Spring averages 98 million L (26 million 

gallons) per day (Vineyard and Feder 1982; National 

Park Service 2015). During base flow conditions, the 

13 largest springs in the park area account for over 

80% of the Current River flow measured downstream 

of Big Spring. Including discharge from other springs, 

the cumulative discharge from springs is over 90% 

of the river flow (Mugel et al. 2009). Because of their 

stable, year-round temperatures and distinct water 

chemistry, springs provide habitat for flora and fauna 

not otherwise associated with the Current River and 

Jacks Fork corridors (see “Geologic Significance and 

Connections” section; National Park Service 2015). 

Resource managers monitor aquatic vegetation, aquatic 

invertebrates, fish, habitat, and water quality for spring 

communities at six springs within the park (Bowles et al. 

2011). 

Dissolved carbonate minerals in the spring water, in 

conjunction with spring depth and the blue of the 

sky, create a vivid blue color for many of the springs. 

Fine-grained sediments flushed into the springs from 

subterranean conduits after precipitation can create a 

“milky” appearance of the springs and rivers (National 

Park Service 2015). 

Karst dissolution has regionally created a vast network 

of caves, cracks, and passages that funnel water from the 

recharge areas at the surface to the Ozark springs. For 

example, the recharge area for (1) Blue Spring is about 

277 km2

 (107 mi2), (2) Pulltite Spring encompasses 418.2 

km2 (161.5 mi2), and (3) Welch Spring includes about 

313 km2 (121 mi2) (Aley and Aley 1987; National Park 

Service 2015). Dye tracing tests revealed groundwater 

Figure 12. Photographs of Big Spring. (A) Big Spring has flowed from different conduits through time, some of which 

are left as cave openings. (B) Gushing flows are forced from underground under hydrostatic pressure in a confined 

groundwater setting. (C) Clear, blue-colored water from Big Spring flowing down the Big Spring branch toward the 

Current River. Photographs by Sid Covington (NPS Geologic Resources Division) taken in February 2002.
18

travels from as far as 80 km (50 mi) away and takes up 

to 14 days to flow from the surface to Big Spring (fig. 

13; Imes and Kleeschulte 1995; Kleeschulte 2000). 

Geologists estimate that 55 m3 (1,950 ft3) of dissolved 

carbonate rock flows out of Big Spring every day (Imes 

et al. 2007; National Park Service 2015). This means the 

total volume of cave passages increases by 224,000 m3

(7,920,000 ft3) per year (Harrison et al. 1997).

The water flowing out of the park’s springs is not 

merely meteoric water trickling downward through 

the bedrock. At Alley Spring, along the Jacks Fork, 

the source of water is from a lower cave passage (fig. 

14). Artesian pressure causes the upward movement 

of groundwater from cavernous bedrock beneath the 

dissolution-resistant sandstone layers. 

Sinkholes

A sinkhole, or doline, is a depression that has no natural 

external surface drainage—when it rains, all of the water 

Figure 13. Map of spring recharge areas over the surface-water and groundwater basins of the Current River and Jacks 

Fork. Spring recharge areas (blue polygons) for the major springs of Ozark National Scenic Riverwaysare complex, 

overlap, and cross both the groundwater basin (yellow outline, defined by water-well measured potentiometric 

surface) and the surface-water basin (pink outline). Recharge areas that cross the potentiometric groundwater basin 

are examples of interbasin transfers of groundwater. The park is the white translucent areas. Much of the recharge 

areas are well beyond park boundaries. Graphic by Trista Thornberry-Ehrlich (Colorado State University) redrafted after 

figure 23 in Mugel et al. (2009) using ESRI World Imagery basemap (accessed 8 October 2015).
19

stays inside the sinkhole and typically drains into the 

subsurface. In general, sinkholes can vary from a few 

square meters to hundreds of hectares in area and from 

less than one to hundreds of meters deep. Some are 

shaped like shallow saucers or bowls with gently sloping 

walls whereas others have vertical walls; some hold 

water indefinitely and form natural ponds (Kaufman 

2007). Sinkholes typically form at least in part by 

collapse or slow subsidence of dissolved bedrock 

fragments into an underground conduit or void (e.g., 

cover-subsidence, and cover-collapse sinkholes; figs. 15 

and 16). The bottom conduits (“throat”) of the park’s 

sinkholes are often blocked by debris and other material 

(Lowell et al. 2010). Where dissolution creates a large 

enough void beneath a capping sandstone layer, the 

surface collapses to form a sinkhole. Sinkholes in the 

park are commonly rimmed with sandstone or chert 

blocks suggesting bedrock collapse of sandstone into 

dissolution voids below (Weary and Orndorff 2001; 

Orndorff et al. 2006). Sinkholes mapped on the lower 

part of the Roubidoux Formation collapsed through 

the basal sandstones into caves of the underlying 

Figure 14. Illustration of Alley Spring conduit system. Brown contour lines are 15 m (50 ft) intervals with the highest 

contour at 270 m (900 ft) elevation and the lowest at 200 m (650 ft). Hydrostatic pressure caused from confining 

sandstone layers in the overlying bedrock pushes water from below the surface upwards toward the rise pool of 

Alley Spring. Prominent sandstone layers occur within the Roubidoux Formation (geologic map unit Or), Gasconade 

Dolomite (Og), and Eminence Dolomite (Ce). Graphic by Trista Thornberry-Ehrlich (Colorado State University) redrafted 

after figure 6 in Orndorff et al. (2006).
20

Gasconade Dolomite. Sinkholes in the lower part of 

the Jefferson City Dolomite are collapsed into caves 

beneath the upper sandstone of the Roubidoux 

Formation. 

Sinkhole collapse may be more common during times 

of flooding or other high water or high flow events 

but it can happen anytime. Human activity may also 

trigger sinkhole collapse. For example, groundwater 

pumping can lower the water table thereby reducing 

Figure 15. Three-dimensional illustration of karst landscape formation. Resistant cap rocks such as sandstone layers in 

the Roubidoux Formation (Or) overlie caves and sinkhole plains. Sinkholes are common throughout the area of Ozark 

National Scenic Riverways, where karst landscapes dominate and continue to develop today in the Ordovician and 

Cambrian dolomite and limestone (geologic map units Cp, Ce, Og, Or, and Ojc). Graphic by Trista L. Thornberry-Ehrlich 

(Colorado State University), created using information from Hack (1974). 
21

buoyant support of the overlying rock which may lead 

to subsidence or collapse into a sinkhole. Refer to the 

“Geologic Resource Management Issues” chapter for 

additional information.

Sinkholes in the Roubidoux Formation, Jefferson City 

Dolomite, Gasconade Dolomite, Eminence Dolomite, 

and Potosi Dolomite (geologic map units Or, Ojc, Og, 

Ce, and Cp, respectively) are mapped in the “Hazard 

Figure 16. Illustration of sinkhole types. Dissolution, cover-subsidence, and cover-collapse sinkholes develop from 

dissolution and downward erosion of unconsolidated material into the underlying cavities. Sinkholes can be a 

combination of the three types or may form in several overlapping phases. The type of sinkhole that forms is 

controlled in part by the thickness and type of overburden and the local hydrology. Graphic by Trista L. ThornberryEhrlich (Colorado State University) after figures by Tihansky (1999:126–127). 
22

Area Features” layer within the GRI GIS data. Muck 

(Qm) accumulated in many sinkholes when they were 

filled with water (Vana-Miller 2007; Weary et al. 2016). 

In the park, sinkholes occur near Blue Spring, Rymers, 

Horse Camp, and Shawnee Creek on the Jacks Fork, 

and near Akers, Devils Well, Bee Bluff, Blue Spring, Big 

Spring, and Cataract Landing along the Current River 

(Weary et al. 2016). High concentrations of sinkholes 

are located in areas of “weak” rock such as rocks 

adjacent to major fault zones and in areas underlain by 

the fractured or deformed Roubidoux Formation and 

Jefferson City Dolomite (see “Faults and Fractures” 

section; Orndorff et al. 2006). 

At least 339 sinkholes occur in the Big Spring recharge 

area, 312 occur within the recharge area for Alley 

Spring, and 284 are within the recharge area for Welch 

Spring (Mugel et al. 2009; Dave Weary, US Geological 

Survey, geologist, written communication, 21 June 

2016). The Devils Well sinkhole formed when the 

roof (supported by the Gunter Sandstone member 

of the Gasconade Dolomite) of a large cavern within 

the Eminence Dolomite containing a subterranean 

lake collapsed (fig. 17; Lowell et al. 2010; Weary et al. 

2014). A 24 m- (80 ft-) deep lake is now visible through 

the sinkhole and is about 30 m (100 ft) below the 

viewing platform; a small natural bridge of the Gunter 

Sandstone member of the Gasconade Dolomite is just 

above the viewing platform (Lowell et al. 2010; National 

Park Service 2015). Many sinkholes are filled or covered 

by residuum (e.g., QTr, QTtrc, and QTrr) left from intense 

weathering of the bedrock (Lowell et al. 2010).

Losing Streams

Losing or “sinking” streams are karst features wherein 

surficial drainage sinks relatively rapidly underground 

to flow through the subterranean conduits and caves. 

Sinking streams seem to disappear. Some streams 

may flow along the surface of an insoluble caprock 

until reaching a layer of karst rock, at which point the 

drainage almost entirely flows underground. Within the 

Current River watershed, 340 km (211 mi) of streams 

are designated losing streams—those which distribute 

30% or more of their flow through permeable geologic 

materials into a bedrock aquifer within 4 km (2 mi) 

distance downstream of an existing discharge (Missouri 

Figure 17. Cross-sectional illustration of Devils Well sinkhole and subterranean lake. The conduit system is forming 

within the Eminence Dolomite (Ce) beneath the Gunter Sandstone member of the Gasconade Dolomite (Og). Devils 

Well formed where a large chunk of the roof collapsed beneath the sandstone. Future collapse is possible. Graphic by 

Trista Thornberry-Ehrlich (Colorado State University) redrafted after figure 4.2 in Lowell et al. (2010).
23

Department of Natural Resources 1999). Within the 

Jacks Fork watershed, 13 km (8 mi) of streams are 

designated losing streams (Missouri Department of 

Conservation 2016). 

Cave Habitats

According to Baker et al. (2015), caves support many 

aquatic and terrestrial habitats defined by a variety of 

environmental parameters, including 

● zonation (the level within the cave; e.g., entrance

zone, twilight zone, and deep cave or phreatic and

vadose zones above and below the water table,

respectively)

● available light (any light allows some plant species

to exist)

● humidity (deep cave levels routinely exceed 99%)

● temperature

● gases (e.g., carbon dioxide, hydrogen sulfide,

methane, and radon)

● water in cave streams, drips, drip pools, and seeps

● morphology of the cave passage (i.e., abundance of

ledges or ceiling cracks, ceiling height, domes)

● substrate (e.g., dry rock areas to shelter spiders or

drip pools supporting tiny ostracods)

● connectivity (connections with the surface can

introduce nutrients.

The “Geologic Setting and Significance” chapter lists 

some of the endemic or significant cave flora and 

fauna that inhabit caves in the park. Cave habitats are 

particularly sensitive to changing conditions and take a 

long time to recover from disturbance. 

Surficial Geologic Map Units

Unlike bedrock units that are typically described 

and mapped by age and rock type, surficial deposits 

are described and mapped (“Q” and “QT” units) 

primarily by their process of deposition and resulting 

geomorphology. Surficial deposits cover nearly all 

(about 95%) of the drainage basins in the Ozarks 

area including the Current River and Jacks Fork 

valleys (Weary et al. 2014). The surficial deposits 

mapped within the park resulted from the following 

processes (see the Map Unit Properties Table for more 

information):

● flowing water (Qa, Qt, and QTg)

● standing water (Qm)

● blowing wind (Ql and Qtl)

● slope movements (Qc and Qls)

● and frost weathering or deep weathering (QTtrc,

QTr, and QTrr).

Alluvium and terrace deposits (Qa and Qt, respectively) 

are the most common surficial units by area (Weary et 

al. 2016). Qm is further discussed in the “Sinkholes” 

subsection. Ql and Qtl figure prominently in the 

“Periglacial Features” section. Qc and Qls collect at the 

bases of slopes (see “Slope Movements” section). For 

a discussion about QTtrc, QTr, and QTrr, see “Bedrock 

Weathering and Residuum Formation” section.

Bedrock Weathering and Residuum 

Formation

Carbonate minerals make up the majority of the 

Paleozoic bedrock. While those minerals and rocks 

dissolve to create karst features, insoluble components 

of the bedrock, such as chert, sand, and clay, are left 

behind. These “leftovers” can accumulate to great 

depths and are called “residuum.” Residuum in the 

park area is commonly red or reddish-orange sandy clay 

and includes all sizes of particles from small clays up 

to cobbles and boulders up to 1.8 m (6 ft) in diameter 

(Weary et al. 2014). Of all the surficial units mapped 

by Weary et al. (2014), they consider residuum as the 

greatest surficial deposit volumetrically with some 

deposits more than 30 m (100 ft) thick although it is 

typically about 12 m (40 ft) thick in the park (Weary et 

al. 2014). 

Most of the residuum was derived from the Roubidoux 

Formation (Or) and was mapped as QTrr although 

unmapped Roubidoux residuum occurs nearly 

everywhere the formation was found (Weary et al. 

2014). The Peck Ranch unit (QTr) is also a residuum unit 

but was only mapped outside the park, south of Rocky 

Falls. Some residuum is also present in map unit QTrc, 

mapped near Rock Falls and south of Roberts Field. 

Residuum units were mostly mapped on ridge tops; 

being clay rich, they are rather “sticky” (Dave Weary 

and Randy Orndorff, US Geological Survey, conference 

call, geologists, 20 October 2015).

Slope Movements

Steep slopes, which increase the potential for slope 

movements, characterize the bluffs and cliffs adjacent 

to the park’s rivers, streams, and tributaries. Colluvium 

(Qc) and landslide deposits (Qls) are part of the GRI 
24

Figure 18. Illustrations of slope movements. Different categories of slope movement are defined by material type, 

nature of the movement, rate of movement, and moisture content. Grayed areas represent conditions that may not 

exist at Ozark National Scenic Riverways. Graphic by Trista Thornberry-Ehrlich (Colorado State University) redrafted 

after a graphic and information in Varnes (1978).
25

GIS data (see the Map Unit Properties Table for more 

details; Weary et al. 2014). Soil creep, rockfalls, debris 

flows, and avalanches are common types of slope 

movement (fig. 18). These processes and the resultant 

deposits are also known as “mass wasting” and 

commonly grouped as “landslides.” Slope movements 

occur on time scales ranging from seconds to years. 

Refer to figure 18 for illustrations of slope movements. 

Hazards and risks associated with slope movements 

in the park are described in the “Geologic Resource 

Management Issues” chapter.

Differential weathering or erosion is the process by 

which earth materials wear away or break down at 

different rates based on their composition, structural 

integrity, geographic location, exposure, and the local 

climate. For example, a coarse-grained, well-cemented, 

quartz-rich sandstone is much more resistant to erosion 

than a weakly cemented shale or soluble limestone 

or dolomite. Differential weathering created the 

steep slopes and unconsolidated material, which are 

susceptible to slope movements, at the park.

In areas where the Gunter Sandstone member of 

the Gasconade Dolomite (part of Og) is exposed, its 

resistance to erosion produces benches on hillsides (fig. 

19), small waterfalls, and streams that are “perched” 

on the sandstone. Dissolution and erosion removes the 

soluble carbonate rocks above and below this and other 

thick sandstone layers (e.g., those within the Roubidoux 

Formation [Or]) (Lowell et al. 2010). This situation may 

result in increased likelihood for rockfall (see fig. 19) 

which creates hazards where trails or the river pass near 

the ledges. Large chunks of sandstone are wedged apart 

by processes such as frost weathering and tree-root 

wedging and tumble downslope. 

Periglacial Features

Repeated glaciations (ice ages) during the Pleistocene 

Epoch (2 million to approximately 20,000 years 

ago) scoured and reshaped the landscape of the 

northeastern United States and northern Missouri. 

The great continental ice sheets did not reach the park; 

their maximum southern extent was the Missouri 

River (see fig. 2). However, the cold global climates 

associated with the glacial events (and to a lesser extent, 

Figure 19. Photograph looking downstream along Jacks Fork east of Jam Up Cave. Differential weathering in the 

Gasconade Dolomite (lower portion of bluff) and Roubidoux Formation (upper portion of bluff) creates cliffs, ledges, 

and overhangs that are susceptible to slope movements, particularly rockfall. A relatively fresh rockfall “scar” is visible. 

Approximate contact between the two units is shown as a white dashed line. National Park Service photograph by 

Victoria Grant (Ozark National Scenic Riverways), March 2007. Cover photograph from Weary et al. (2014).
26

modern winters) altered the Ozark landscape. The 

term “periglacial” describes features that were never 

buried by glaciers, but were subject to cold climates and 

associated frost weathering. Frost weathering occurs 

via the freezing and thawing of water within rocks or 

minerals.

Apart from cores taken in the fluvial terraces to 

understand paleogeomorphology, the periglacial 

features at the park have yet to be comprehensively 

inventoried, described, or mapped (Joe Gilman, 

Missouri Geological Survey, geologist, conference 

call, 20 October 2015). The GRI GIS data include 

colluvium (Qc) and landslide deposits (Qls) that date to 

the Holocene and Pleistocene, the bulk of both units 

could have formed via periglacial processes (Weary 

et al. 2014; Joe Gilman, Missouri Geological Survey, 

geologist, conference call, 20 October 2015). Loess 

(Ql) and loess-covered terrace deposits (Qtl) also 

record periglacial environments. Loess forms as fine, 

winnowed, wind-blown silt that accumulates in ridges 

and layers when vegetation is sparse and sediment is 

abundant, such as during a glacial retreat. It can be 

derived from the floodplains of glacial braided outwash 

rivers that carried large volumes of glacial meltwater 

and sediments from the melting glaciers. Loess covers 

terrace deposits (Qtl) just upstream from Van Buren, 

Missouri. Another loess deposit (Ql) is mapped atop 

rhyolite of Shut-In Mountain (Ysi) near Rocky Falls 

beyond park boundaries. Loess is an aeolian feature. 

Aeolian processes refer to wind-blown erosion, 

transportation, and deposition of sediments (Lancaster 

2009). The NPS Geologic Resources Division Aeolian 

Resource Monitoring website, http://go.nps.gov/

monitor_aeolian, provides additional information. The 

field study of periglacial features at the park would be 

a potential project for the Geoscientists-in-the-Parks 

program (http://go.nps.gov/gip).

Sedimentary Rock Features

The vast majority of rocks in Ozark National Scenic 

Riverways are sedimentary. They comprise the cliffs in 

the park and host the caves and karst features. At the 

park, the sedimentary rocks are mostly either clastic or 

chemical. Clastic sedimentary rocks are the products 

of weathering, erosion, transportation, and deposition 

of rock fragments called “clasts.” Clastic sedimentary 

rocks are named after the size of clasts (table 1). Highenergy depositional environments, such as fast-moving 

streams, leave behind larger (heavier) clasts while 

transporting smaller (lighter) clasts. Where water 

moves slowly or is stagnant, such as in lakes, the water 

cannot transport even the smallest clasts and they are 

deposited. Wind also transports and deposits sand-sized 

or smaller clasts (table 1). Chemical sedimentary rocks 

form when ions (microscopic particles of rock dissolved 

during chemical weathering) precipitate out of water. 

For example, carbonate rocks, such as limestone 

(calcium) or dolomite (calcium and magnesium) have a 

carbonate (CO3

2-) ion.

In the park, clastic and chemical sedimentary rocks 

are commonly interbedded, such as with the dolomite, 

quartz sandstone, and chert-rich layers of the Eminence 

Dolomite (geologic map unit Ce), Roubidoux Formation 

(Or), and Jefferson City Dolomite (Ojc) (Weary et al. 

2014). The Gasconade and Potosi dolomites (Og and 

Cp) are mostly dolomite; these units contain the greatest 

degree of karst development (see “Cave and Karst 

Features and Processes” section; Weary et al. 2014). 

Table 1. Clastic sedimentary rock classification and characteristics.

Rock Name Clast Size Depositional Environment Park Examples

Conglomerate 

(rounded clasts) or 

Breccia (angular 

clasts)

>2 mm (0.08 in) [larger]

The relative energy levels in the 

depositional environments ranges from 

higher energy (conglomerate and breccia) 

to lower energy (claystone).

Lamotte Sandstone (buried at the park)

Sandstone 1/16–2 mm (0.0025–0.08 in)

Roubidoux Formation (Or); Gunter Sandstone 

member of the Gasconade Dolomite (Og); 

layers in the Eminence Dolomite (Ce)

Siltstone 1/256–1/16 mm (0.00015–

0.0025 in) Bonneterre Formation (buried at the park)

Claystone <1/256 mm (0.00015 in) 

[smaller] Not prominent in park area rocks

Note: Claystones and siltstones can also be called “mudstone,” or if they break into thin layers, “shale."
27

Dolomite is a carbonate rock (has a CO3

2- ion) with a 

high percentage of magnesium in addition to calcium. 

Limestone is another common carbonate but has 

nearly no magnesium. Carbonate rocks are indicative of 

deposition in relatively shallow seas, often in equatorial 

areas. Those conditions are inferred for the park and 

much of the southeast during the Paleozoic Era (see 

“Geologic History” chapter).

Features within the sedimentary rocks provide 

additional information about their depositional 

environment and history. Marine invertebrate fossils 

are common in many of the layers as discussed in 

the “Paleontological Resources” section. Particularly 

noteworthy is the Cryptozoon chert layer in the 

Gasconade Dolomite (see fig. 4). As chert, the layer is 

hard, extremely dense or compact, microcrystalline, 

quartz-rich rock, composed of the remains of primitive 

reef life (fossil algae). Also within the Gasconade 

Dolomite are layers of oolites or rocks composed 

of spherical grains of ooliths that formed as layer upon 

layer of minerals adhered to a central nucleus, 

typically in shallow water with oscillating waves. 

The orthoquartzite sandstone layers in the Eminence 

Dolomite, Gasconade Dolomite, and Roubidoux 

Formation are almost pure quartz; other original 

mineral constituents either dissolved or were carried 

away during deposition. The Potosi Dolomite has 

vugs or cavities lined with druse or crusts of quartz 

crystals. “Vuggy” dolomite is also part of the 

Gasconade Dolomite (Weary et al. 2014).

Figure 20. Illustration of Rocky Falls over rhyolite of ShutIn Mountain. Sedimentary layering (bedding) within the 

Eminence Dolomite (Ce) adjacent to a Mesoproterozoic 

knob of rhyolite of Shut-In Mountain (Ysi) dips away 

from the knob. The knob was an island during original 

deposition of the dolomite. The Denning Hollow shear 

zone crosses through the Rocky Falls. It may have provided 

a zone of weakness across the resistant igneous rock. Top 

photograph by Sid Covington (NPS Geologic Resources 

Division) taken in February 2002. Graphic by Trista 

Thornberry-Ehrlich (Colorado State University using GRI 

map data from Weary et al. (2016) and ESRI World Imagery 

basemap (accessed 8 October September 2015).
28

Most of the sedimentary layers are nearly horizontal, 

little disturbed since deposition. The regional average 

is just 3° of dip to the southeast. The gradient of the 

Current River follows this regional geological incline. 

Contrary to the overall trend are the much steeper, 

radially dipping beds formed near the “knobs” of 

very old volcanic rock (see “Volcanic Rocks and the 

Eminence Caldera” section and “Geologic History” 

chapter) where sediments accumulated and covered 

the knobs (Weary et al. 2014). This is visible along 

the west side of Rocky Creek along a stretch of the 

Current River section of the Ozark Trail where the 

Eminence Dolomite (Ce) was deposited on the flank of 

the rhyolite of Shut-In Mountain (Ysi). Here, the dip of 

the sedimentary layers is away from the summit of the 

mountain in a radial pattern (fig. 20; Lowell et al. 2010). 

Strike (orientation of rock layers) and dip (degree of 

tilt) measurements are included in the GRI GIS data 

“Geologic Attitude Observation Localities” layer.

Paleontological Resources

Paleontological resources (fossils) are any evidence 

of life preserved in a geologic context (Santucci et al. 

2009). All fossils are nonrenewable. Body fossils are 

any remains of the actual organism such as bones, 

teeth, shells, or leaves. Trace fossils are evidence of 

biological activity; examples include burrows, tracks, or 

coprolites (fossil dung). Fossils in NPS areas occur in 

rocks or unconsolidated deposits, museum collections, 

and cultural contexts such as building stones or 

archeological resources. As of August 2016, 263 parks, 

including Ozark National Scenic Riverways, had 

documented paleontological resources in at least one of 

these contexts. The park contains examples of all three. 

Resource management issues are documented in that 

chapter of this report.

Hunt et al. (2008) provided a summary of the 

paleontological resources for the entire Heartland 

Inventory and Monitoring Network, which includes 

the park. See the Map Unit Properties Table for more 

details. The NPS Fossils and Paleontology website, 

http://go.nps.gov/fossils_and_paleo, provides more 

information. 

Bedrock Fossils

Fossils have been discovered within the Eminence 

Dolomite, Gasconade Dolomite, and Roubidoux 

Formation (geologic map units Ce, Og, and Or, 

respectively) within the boundaries of the park. The 

fossils include stromatolites (fossil algae), gastropods, 

brachiopods, trilobites, cephalopods, conodonts, and 

some crinoid fragments all of which are common in 

rocks from Paleozoic Era shallow seas (see “Geologic 

History” chapter) (Repetski et al. 2000; Weary and 

Schindler 2004). Fossils have been discovered outside 

the park within the Potosi Dolomite (Cp), as well as in 

unconsolidated surficial deposits (“QT” and “Q” map 

units) suggesting that such fossils might also be found in 

those units in the park.

According to Justin Tweet (NPS Geologic Resources 

Division, guest scientist, written communication, 

24 August 2016), two nautiloid species and three 

monoplacophoran species were named from specimens 

found within the park. Three additional nautiloid 

species, two trilobite species, and a gastropod species 

were named from specimens potentially found within 

the park.

Cave Fossils

Ozark National Scenic Riverways is one of at least 35 

NPS units that preserve fossils within caves. Santucci et 

al. (2001) described how fossils in caves occur in two 

contexts: (1) as part of the bedrock in which the cave is 

formed, or (2) as Pleistocene and/or Holocene remains 

of organisms that died in or were transported into the 

cave. Caves and other karst features can attract and trap 

animals; other fossils may have been transported into 

the cave via flooding, habitation by organisms such as 

packrats, or humans. If the remains were transported 

into the cave by humans, they may also be considered 

cultural resources. With more than 402 known caves 

(see “Cave and Karst Features and Processes” section), 

the park has abundant cave fossil resources and the 

potential for future discoveries is excellent (Hunt et al. 

2008). Oscar “Oz” Hawksley, of Central Missouri State 

University, collected many of fossils between the 1950s 

and 1980, which are now curated in the Illinois State 

Museum Vertebrate Paleontology Collection. Examples 

of notable fossil animals from park caves include the 

following, as reported by Santucci et al. (2001): 

● American black bear (Ursus americanus) (Tucker

1984)

● short-faced bear (Arctodus simus)

● jaguar (Panthera onca)

● stilt-legged deer Sangamona (or Odocoileus)

● beaver (Castor canadensis)
29

● dire wolf (Canis (Aenocyon) dirus) (Galbreath 1964)

● parts of a giant armadillo carapace.

All Pleistocene vertebrate fossils from the caves of 

Missouri are Wisconsinan (last major glaciation, 

culminating 50,000 years ago) or younger (Reams 1968; 

Weary and Schindler 2004).

Fossils in Museum Collections

Fossils from the park are in the collections of the 

following museums or institutions as reported by Hunt 

et al. (2008):

● Ozark National Scenic Riverways

● NPS Midwest Archeological Center

● College of the Ozarks

● Illinois State Museum

● Smithsonian Institution, National Museum of

Natural History

● University of Michigan Museum of Paleontology

● University of Missouri-Columbia

● US Geological Survey. 

Fossils in Cultural Contexts

Fossils discovered in archeological settings are 

considered cultural as well as natural resources. For 

example, a Nodena arrow point was discovered 

embedded in the pelvis of black bear (Ursus 

americanus) remains. A fossil snail was collected 

during excavation of a late prehistoric feature at a 

site, clearly anthropogenically brought to this area 

about 1000-1100 CE (D. Bringelson, Archeologist, 

Midwest Archeological Center [MWAC], personal 

communication from May 2008 as reported in Hunt 

et al. 2008). Another fossil shell was collected from the 

surface of an archeological site in Dent County (M. 

Lynott, MWAC, archeologist, personal communication 

from June 2008 as reported in Hunt et al. 2008). Fossils 

are associated with at least 14 MWAC catalog numbers 

(Justin Tweet, NPS Geologic Resources Division, guest 

scientist, written communication, 24 August 2016). 

Kenworthy and Santucci (2006) provided an overview 

of NPS paleontological resources in cultural resource 

contexts.

Volcanic Rocks and the Eminence Caldera

By far the oldest rocks in the park, and some of the 

oldest rocks in Missouri, are igneous rocks more than 

1.4 billion years old (1,400,000,000 years; “Y” geologic 

map units). The vast majority of them erupted from 

a chain of caldera-forming volcanos that extended 

from Michigan to southeastern Missouri and included 

the Eminence Caldera. The St. Francois Mountains 

to the northeast are similar in age and composition. 

Igneous rocks are those that formed from molten 

material. Where molten material erupts from volcanoes, 

cools and solidifies at the Earth’s surface, extrusive 

(“volcanic”) igneous rocks form. Where molten material 

cools beneath the surface, intrusive (“plutonic”) igneous 

rocks form. See table 2 for a simple classification of 

igneous rocks.

Table 2. Volcanic rocks classification and relative characteristics.

Rock Name: Rhyolite Rhyodacite Dacite Andesite Basaltic 

Andesite Basalt

Silica (SiO2)

content* ≥72% 68%–72% 63%–68% 57%–63% 52%–57% ≤52%

Color Color ranges from lighter (for silica-rich rhyolite) to darker (for lower silica basalt)

Viscosity of 

magma Viscosity ranges from high (thicker) for rhyolite to low (more fluid) for basalt.

Typical style of 

eruption Eruption style ranges from explosive for rhyolite to effusive for basalt.

Park Examples

Lower and Upper 

Coot Mountain 

units (Ycl and Ycu);

Rhyolites of Shut-In 

Mountain (Ysi), 

Sutton Creek 

(Ysc), and Russell 

Mountain (Yrm)

Rhyolite of Russell 

Mountain (Yrm)

Not mapped in 

park.

Not mapped in 

park.

Not mapped in 

park.

Not mapped in 

park.

* from Bacon (2008).
30
31

Figure 21 (facing page). Map of Mesoproterozoic Era map units near the confluence of the Jacks Fork and Current 

rivers. Tuff of little Thorny Mountain (Yltm), the rhyolite of Russell Mountain (Yrm), the rhyolite of Sutton Creek (Ysc), 

and the upper and lower Coot Mountain units (Ycu and Ycl, respectively) compose the lower, volcanic sequence in 

the area, whereas the other units are part of the upper sequence after the caldera collapse. Lower map shows the 

approximate extent of the Eminence caldera. Graphic by Trista Thornberry-Ehrlich (Colorado State University) redrafted 

after figure 8.3 in Lowell et al. (2010) using GRI map data from Weary et al. (2016) and ESRI World Imagery basemap 

(accessed 29 September 2015). Caldera extent from figure 3 in Weary et al. (2014).

Figure 22 (above). Illustration of caldera formation. The volcanic geologic map units associated with the Eminence 

Caldera demonstrate both concurrent and post-caldera collapse features (e.g., tilted flow layering juxtaposed with 

more-or-less horizontal layering). Graphic by Trista L. Thornberry-Ehrlich (Colorado State University) after Smith and 

Bailey (1968, figure 5).
32

With the exception of the Big Spring Granite (Yg) 

mapped between Big Spring and Van Buren, the igneous 

rocks at the park are volcanic rocks. They are mapped 

between Logyard to the southeast and Eminence to the 

west in the area of the confluence of the Current River 

and Jacks Fork (fig. 21; see GRI poster; Weary et al. 

2014, 2016). See the Map Unit Properties Table for more 

details. Rocky Falls flows over the Rhyolite of Shut-In 

Mountain (Ysi).

Geologists use silica (silicon dioxide, SiO2) content 

as a means for classifying volcanic rocks (table 2). 

The percentage of silica influences many properties 

of magma, including viscosity and explosiveness. In 

general, lavas with more silica are more viscous and 

explosive (table 2). The volcanic rocks at the park are 

primarily rhyolites (Yrm, Ysc, and Ysi) and ash-flow or 

air-fall tuffs (Ysm, Ymm, Yltm, Ycu, and Ycl) of broadly 

rhyolitic composition. The type of magma that forms 

rhyolite is very viscous and can erupt during the most 

explosive type of eruptions—caldera forming eruptions. 

For comparison, Yellowstone National Park is atop 

a massive caldera (a “supervolcano”) and a caldera 

eruption formed the crater at Crater Lake National 

Park (see GRI report by KellerLynn 2013). A caldera is 

a volcanic feature that forms as a large, basin-shaped 

depression that collapsed during a massive eruption (fig. 

22). In the geologic record, these are marked by faults 

that surround volcanic rocks.

The Eminence caldera erupted 1.48 billion years ago. 

Today, the caldera is denoted by faults oriented to the 

northeast and northwest (see “Faults and Fractures” 

section). More than 50 isolated “knobs” of ignimbrite 

(the deposit of an explosive volcanic flow) and lava—

relatively hard rocks compared to the surrounding 

sedimentary rocks—are all that remains of the caldera 

(Lowell 2000; Weary et al. 2014). Sedimentary layers 

in younger, adjacent rocks, tilt away from these knobs 

indicating that they were a topographic high and 

probably formed islands when the area was underwater 

during the Paleozoic Era (see fig. 20 and “Geologic 

History” chapter). In general, the volcanic rocks do 

not show any sign of being buried more than a few 

kilometers or of other extensive deformation so they 

have likely been high points for more than 500 million 

years (Weary et al. 2014). 

Steeply dipping, rotated blocks of depositional flowbanding are characteristic of caldera eruptions. The 

volcanic rocks have a banded texture called “foliation” 

that was created while the rocks erupted, as well as 

postdepositional deformation (Weary et al. 2014). The 

bands formed because the lava was heterogeneous and 

the different materials flowed, were ejected, and/or 

cooled in different ways. Successive eruptions created 

repeated layers of banded material. Molten material 

associated with these volcanoes that cooled slowly 

beneath the surface but did not erupt, formed granite 

plutons. Where these buried masses are juxtaposed 

with Paleozoic sedimentary rocks (e.g., Bonneterre 

Formation) are favorable sites for finding minerals such 

as those mined from the Viburnum Trend (see “External 

Mineral Development” section) which accumulated 

as saturated, geothermal fluids percolated through the 

rocks in the late Paleozoic (Lowell et al. 2010).

Radiometric Ages

In geology, radiometric dating methods compare 

the abundance of a naturally occurring radioactive 

isotope of a mineral with the abundance of its decay 

products, which form at a known constant rate of 

decay (Boltwood 1907). Radiometric dating is now 

the principal source of information about the absolute 

age of rocks and other geological features. Igneous 

rocks and volcanic ash layers are prime candidates for 

radiometric dating because they contain the necessary 

radioactive minerals. Sedimentary rocks rarely 

contain the appropriate minerals and are often dated 

relatively—based on their relationship with other rocks. 

The ages of several igneous rock units in the park have 

been determined via radiometric dating techniques. 

The GRI GIS data include uranium-lead ages for 

the Big Spring quad granite (Yg) and the Rhyolite of 

Shut-In Mountain (Ysi) (Weary et al. 2014). Dates are 

reported on the Map Unit Properties Table. Additional 

radiometric dating could reveal more about the 

complicated history of the igneous rocks of the area and 

constrain the timing of the Eminence caldera’s eruption 

and collapse. 

Faults and Fractures

A fault is a fracture along which rocks have moved. At 

the park, faults are commonly obscured by vegetation 

and residuum (e.g., QTr, QTtrc, and QTrr). Their 

presence is inferred from vertical offset of strata and 

cataclastic (severely, brittlely deformed) bands observed 

in outcrop or in blocks of sandstone (Lowell et al. 

2010). The three primary types of faults are normal 

faults, reverse faults, and strike-slip faults. They are 
33

classified based on motion of rocks on either side of the 

fault plane as described in fig. 23. Reverse and vertical 

faults of unknown offset/displacement (probably strikeslip) are mapped in GRI GIS data (Weary et al. 2014a). 

The GRI GIS data include 29 named faults; typically 

these faults are named for their geographic location and 

are probably strike-slip faults (see posters, in pocket).

Regionally, the faults are oriented along two dominant 

strikes: northeast and northwest (Lowell et al. 2010). 

The faults are divisible into three broad age groups 

corresponding to periods of volcanism, mountain 

building, and other regional-scale deformation (see 

“Geologic History” section): (1) those showing 

evidence of only being active in the Mesoproterozoic 

Era, (2) those that were active at one or more times 

prior to the deposition of the Ordovician sedimentary 

rocks, and (3) those that were active at one or more 

times in the Phanerozoic Eon and probably during the 

Proterozoic Eon (Weary et al. 2014). 

In the early 1800s, movement along faults in the 

New Madrid Seismic Zone southeast of the park 

were responsible for some of the largest earthquakes 

ever recorded in North America. Smaller magnitude 

earthquakes occasionally shake the region, including 

one in October 2015 while this report was being written. 

See the “Seismic Activity Hazards and Risk” section. 

The Denning Hollow and Mud Spring Hollow shear 

zones are linear areas of deformation, possibly active 

as left-lateral strike-slip zones during the Proterozoic 

Eon and later reactivated. They are characterized by 

features such as closely spaced fractures, mineralized 

veins, a foliation or banded appearance, and reduced 

grain-size (Weary et al. 2014). The two zones are 

roughly parallel, striking northeast to southwest, and 

are about 2.3 km (1.4 mi) apart in the vicinity of Roberts 

Field campground. The western Denning Hollow shear 

zone forms a contact between the Eminence and Potosi 

dolomites (Ce and Cp). An unnamed, northwest to 

southeast striking, vertical fault truncates the Denning 

Hollow shear zone; this fault is in turn truncated by the 

Mud Spring Hollow shear zone. 

Vertical joints, or fractures along which movement 

has not occurred, are oriented north-south and eastnortheast (National Park Service 2007). These joints 

formed during the buckling of Earth’s crust associated 

with the Ouachita orogeny, and possibly the Alleghany 

orogeny, that constructed mountains to the south in 

Pennsylvanian–Permian time (Cox 1995; Weary and 

Orndorff 2001). The joint sets are oriented parallel 

to the direction of the sedimentary layering (bedding 

planes), and because most of the park’s bedrock is 

soluble (see “Caves and Karst Features and Processes” 

section), the joints are enlarged by surface and 

Figure 23. Illustrations of fault types. Movement occurs along a fault plane. Footwalls are below the fault plane and 

hanging walls are above. In a normal fault, crustal extension (pulling apart) moves the hanging wall down relative 

to the footwall. In a reverse fault, crustal compression moves the hanging wall up relative to the footwall. A thrust 

fault is similar to a reverse fault, but has a dip angle of less than 45°. In a strike-slip fault, the relative direction of 

movement of the opposing plate is lateral. When movement across the fault is to the right, it is a right-lateral (dextral) 

fault, as illustrated above. When movement is to the left, it is a left-lateral (sinistral) fault. A strike-slip fault between 

two plate boundaries is called a transform fault. Graphic by Trista Thornberry-Ehrlich (Colorado State University).
34

groundwater dissolution (Weary and Orndorff 2001). 

Fractures, joints, faults, and fault zones such as the 

Wilderness-Handy fault zone provide permeable and/

or porous substrates which facilitate groundwater 

movement. Rocks along large deformation zones are 

intensely silicified and brecciated with almost complete 

carbonate dissolution. In the past, mineral-laden 

fluids flowing through these permeable and porous 

zones deposited valuable ores including lead (e.g., the 

Mississippi Valley-type mineralization; see “External 

Mineral Development” section) (Lowell et al. 2010). 

Folds

Despite being difficult to locate due to lack of exposure 

and extensive vegetative cover, small folds are mapped 

in the park. Folds are curves or bends in originally 

flat structures, such as rock strata, bedding planes, or 

foliation. The two primary types of folds are anticlines 

which are “A-shaped” (convex) and synclines which 

are “U-shaped” (concave). Both types of folds can be 

overturned or tilted past vertical. Folds can “plunge” 

meaning the fold axis tilts. As bedrock is compressed, 

anticlines and synclines form adjacent to each other like 

wrinkles in a blanket. A monocline is a local steepening 

of rock layers in an otherwise uniform gentle dip. 

Small-scale anticlines, synclines, and monoclines are 

identified in the GRI GIS data (see posters, in pocket). 

Adjacent and parallel synclines and anticlines deform 

the Gasconade and Eminence dolomites (geologic map 

units Og and Ce, respectively) in the northwesternmost 

corner of the park near Baptist Access on the Current 

River where the fold axes are only about 100 m (330 ft) 

apart. Several fold axes occur in the southernmost reach 

of the park near Kelley Bluff. A monocline occurs just 

northwest of park boundaries in the Waymeyer area. In 

general, gentle, open folds formed during compression 

near faults and in subsidence features related to 

large dissolution (karstic) voids (see “Cave and Karst 

Features and Processes” section). 
35

Geologic Resource Management Issues

Some geologic features, processes, or human activities may require management for human safety, 

protection of infrastructure, and preservation of natural and cultural resources. The NPS Geologic 

Resources Division provides technical and policy assistance for these issues.

During the 2001 scoping meeting (see National Park 

Service 2001) and 2015 conference call, participants 

(see Appendix A) identified the following resource 

management issues.

● Flooding and Fluvial Geomorphology

● Climate Change Impacts

● Caves and Associated Landscape Management

● Ozarks Aquifer and Springs Protection

● Erosion

● Paleontological Resource Inventory, Monitoring, 

and Protection

● Slope Movement Hazards and Risks

● Seismic Activity Hazards and Risks

● Abandoned Mineral Lands

● External Mineral Development

Management Resources

The Additional References section and Appendix B 

list resources available to park managers to support 

science-informed decision making. The park’s Water 

Resources Foundation Document (Vana-Miller 2007) 

and Cave Management Guide (National Park Service 

2010) are primary sources of information for resource 

management within the park. The park’s foundation 

document is forthcoming. Cultural landscape 

restoration and management are also addressed in a 

number of publications.

Flooding, slope movements (including rockfall along 

cliffs or in caves), and earthquakes are examples of 

geologic hazards—a natural or human-caused geologic 

condition or process that may impact park resources, 

infrastructure, or visitor safety. Risk is the probability 

of occurrence combined with the expected degree 

of damage or loss that may result from exposure to a 

hazard, or the likelihood of a hazard causing losses (see 

also Holmes et al. 2013).

The Missouri Department of Natural Resources lists 

information about geologic hazards (e.g., abandoned 

mines, earthquakes, landslides, and karst), mineral 

resources, and geologic maps at their geologic resources 

section website (http://dnr.mo.gov/geology/geosrv/

geores/index.html).

The Heartland Network is monitoring land-cover 

changes at the park. More information about the 

network’s vital signs monitoring program is available at: 

http://science.nature.nps.gov/im/units/htln/monitor/

index.cfm. 

The American Geosciences Institute maintains 

a critical issues program website (http://www.

americangeosciences.org/critical-issues) with 

information on topics including climate, energy, 

hazards, mineral resources, and water. The US 

Geological Survey’s Columbia Environmental Research 

Center maintains a robust website (http://www.cerc.

usgs.gov/) with information about water quality, climate 

change, energy development, environmental chemistry, 

the Ozark Highlands, and ecosystem health.

Resource managers may find Geological Monitoring

(Young and Norby 2009; http://go.nps.gov/

geomonitoring) useful for addressing geologic resource 

management issues. The manual provides guidance for 

monitoring vital signs—measurable parameters of the 

overall condition of natural resources. Each chapter 

covers a different geologic resource and includes 

detailed recommendations for resource managers, 

suggested methods of monitoring, and case studies.

The Geoscientists-in-the-Park and Mosaics in Science 

programs are internship programs to place scientists 

(typically undergraduate students) in parks to complete 

geoscience-related projects that may address resource 

management issues. Projects at Ozark National Scenic 

Riverways have included (as of August 2016):

● Cave/karst inventory and monitoring (1997, 1998, 

2000, 2002)

● Cave/karst research (2001)

● Hydrology inventory and monitoring (2002).

Projects are listed on the GIP website: http://go.nps.

gov/gip_products. Products created by the program 
36

participants may be available on that website or by 

contacting the Geologic Resources Division. Refer to 

the programs’ websites at http://go.nps.gov/gip and 

https://www.nps.gov/subjects/youthprograms/mosaics.

htm for more information.

Flooding and Fluvial Geomorphology 

The fluvial resources associated with the Current River 

and Jacks Fork are the major natural-resource features 

at Ozark National Scenic Riverways. The park was 

established in part to preserve the Current River and 

Jacks Fork as free-flowing rivers. Their courses are 

largely unimpaired by dams or other control methods 

and flow is dependent on rainfall and input from the 

karst subterranean network (e.g., from springs; see 

“Caves and Associated Landscape Management” 

section). Average annual precipitation is 114 cm (45 

in) for Eminence, Missouri (Jacobson and Pugh 1992; 

US Climate Data 2016). Following heavy rainfall, 

rapid surface runoff on the steep valley slopes and 

subterranean recharge contributes to flash flooding 

(Alexander 1990). Water levels in the Current River 

and Jacks Fork can rise as fast as 0.6 m/hour (2 ft/hour) 

(Wilson 2001). 

Streamflow is the most fundamental variable for 

understanding physical, chemical, and biological 

dynamics in the riverine ecosystem (Covington 2002). 

Streamflow data are collected at seven sites within the 

Current River’s and Jacks Fork’s drainages:

(1) Montauk State Park, (2) Highway 17 near Mountain 

View, (3) Alley Spring, (4) Eminence, (5) Akers Ferry, 

(6) Van Buren, and (7) Doniphan (south of the park) 

(Vana-Miller 2007). A stage-only gage was established 

on the Powdermill Bridge in 2015. The highest flows 

occur from April to May (fig. 24). Floods are least 

common from late August to early September. Floods 

typically last at least 2 to 3 days (Wilson 2001). Since 

record keeping began at Van Buren in 1921, 25-year 

floods (flows greater than about 24,900 m3

/sec [87,800 

ft3/sec]) happened in 1935 and 1993. A 50-year flood 

(a discharge that has a 2% chance of being equaled 

or exceeded in any given year with discharge of more 

than 3,000 m3/sec [105,000 ft3/sec]) has not occurred 

(Alexander 1990; Vana-Miller 2007). Flood discharge 

for a 100-year flood (a 1% chance of being equaled 

or exceeded in any given year) for the Current River 

drainage area would be over 3,500 m3/sec (123,000 

ft3/sec). Compare those flows to the Current River’s 

average annual discharge of about 56 m3/sec (2,000 ft3/

sec) at Van Buren (US Geological Survey 2016a). Higher 

in the watershed, above Akers, Missouri, the normal 

flow is about 14 m3/sec (500 ft3/sec) (Alexander 1990; 

Vana-Miller 2007; US Geological Survey 2015, 2016b). 

Because park boundaries and infrastructure closely 

border most of the river corridor, large floods could 

cause safety issues and damage infrastructure. Floods 

of the 25-year magnitude have caused major damage to 

park infrastructure (Wilson 2001). 

The shape or morphology of a stream channel is integral 

to the fluvial and riparian ecosystem, which depends 

on the size, shape, and bottom characteristics of the 

channel and its change through time (Jacobson et al. 

2001; Covington 2002). Riparian zones affect slope 

movements (e.g., interplay of alluvium Qal, landslide 

deposits Qls, and colluvium Qc; see “Slope Movements” 

sections) and channel morphology (Vana-Miller 2007). 

Changes to the rivers’ channels are mostly a natural 

result of meandering; however, human modifications 

Figure 24. Photographs of flood conditions. Floods may occur rapidly after heavy precipitation. Floods are an 

important natural process in maintaining the diversity and health of the riparian zones flanking the rivers. 

Photographs by Victoria Grant (NPS Ozark National Scenic Riverways) taken in April 2011.
37

to the streambanks and floodplain areas have altered 

the system affecting discharge, sediment supply, and 

erosional resistance of the banks (see “Erosion” 

section). As channel morphology changes, spatial and 

temporal distributions of depth, velocity, substrate, and 

alluvial deposits within the stream itself also change. 

Aquatic plants and animals (e.g., mussels) that cannot 

migrate with the changing habitats are negatively 

impacted (Jacobson and Primm 1997; Covington 2002). 

Riparian zones, underlain by alluvium, terrace, and 

slope deposits (Qa, Qls, Qc, Qt, and Qtl) are among the 

most disturbed ecosystems in the park; disturbance 

is accelerated by land clearing, logging, and overuse 

(Vana-Miller 2007). Current land-use stressors to the 

Current River’s and Jacks Fork’s drainage basins include 

the effects of tailing disposal, increased recreational 

use, poorly engineered road crossings, renewed timber 

clearing, land conversion to grazing, and channel 

gravel mining (Jacobson and Primm 1997; Covington 

2002; Vana-Miller 2007). Analysis of drainage-basin 

variables such as channel morphology, bottom sediment 

type, and indicators of channel stability demonstrated 

connections among geology, physiography, and landuse patterns (Panfil and Jacobson 2001). Cleared land 

area is negatively correlated with drainage-basin 

average slope. Bankfull (the point at which the flow 

begins to enter the active floodplain) channel geometry, 

residual pool (the depth that, if flow were reduced 

to zero, water would fill pools just up to their rims) 

dimensions, and bottom sediment particle size correlate 

positively with drainage area and topographic relief 

(Panfil and Jacobson 2001). Channels are shallower 

with finer-grained bedloads in the less rugged, western 

basins of the Current River tributaries, than in the 

steeper, middle and eastern basins (Panfil and Jacobson 

2001). 

Park infrastructure and recreational-use areas are also 

at risk for loss or damage when streams change their 

courses or flooding inundates low areas. Channel 

engineering (e.g., boat ramps, bridge abutments, and 

levees) and river crossings, such as in Eminence on the 

Jacks Fork and Van Buren on the Current River, have 

changed the local flow of the rivers and, consequently, 

their channel morphology by creating scouring in 

some areas and gravel deposits in others (Covington 

2002). While planning for streambank infrastructure, 

the park should consult NPS planning documents 

including Director’s Orders 77-1 (Wetland Protection) 

and 77-2 (Floodplain Management), as well as the 

other laws, regulations, and policies listed in Appendix 

B and available at https://www.nps.gov/applications/

npspolicy/index.cfm.

For areas within the park with flooding concerns 

or other potential changes to channel morphology, 

additional study and monitoring protocols may be 

needed. The protocols used by Panfil and Jacobson 

(2001) identified subtle land-use impacts on channel 

morphology and sediment characteristics in Current 

River tributaries. Jacobson and Pugh (1997) outlined 

stream restoration guidelines that show where 

inherent instability is likely to overwhelm restoration 

activities; these guidelines are now being used by 

the State of Missouri (Covington 2002). McKenney 

(2001) defined spatial and temporal controls on the 

creation and degradation of stream habitats, based 

in part on monitoring data from Jacobson and Pugh 

(1997) from the Ozarks. Park resource managers can 

contact the Heartland I&M network and/or consult 

existing standard operating procedures such as those 

defined in the Geological Monitoring chapter about 

fluvial geomorphology by Lord et al. (2009). They 

described methods for inventorying and monitoring 

geomorphology-related vital signs, including: 

(1) watershed landscape (vegetation, land use, surficial

geology, slopes, and hydrology), (2) hydrology 

(frequency, magnitude, and duration of stream flow

rates), (3) sediment transport (rates, modes, sources,

and types of sediment), (4) channel cross section,

(5) channel planform, and (6) channel longitudinal

profile.

Covington (2002) noted the need to (1) inventory the 

status and vulnerability of campgrounds to flooding, 

(2) incorporate stream-profile data into the park’s GIS,

(3) use historical aerial photographs to measure changes

in stream morphology through time, and (4) study the

impacts of levees, bridge abutments, and armoring to

channel morphology.

Additional data sources and methodologies include:

● US Geological Survey’s existing stream-gauge

network provides a record of aggradation,

degradation, and morphology changes (Jacobson

1995). This could be expanded to include more

gages on tributary streams. Real-time water

resources data are available at

http://mo.water.usgs.gov/.
38

● Low-altitude aerial photography and LiDAR,

particularly useful to document the spatial

distribution of gravel bars (fig. 25) and sediment

routing (Jacobson and Gran 1999).

● Establish a network of monitored cross sections

throughout the park with resurvey/monitor to

provide rates of erosion, deposition, and habitat

alteration (McKenney and Jacobson 1996).

● Continue and expand Global Change network

surveys (McKenney and Jacobson 1996) to include

tributaries and downstream parts of the Jacks

Fork and Current rivers. Two sites are already 

benchmarked on the Jacks Fork (Victoria Grant,

Ozark National Scenic Riverways, natural resources

program manager, conference call, 20 October

2015).

Surface water quality, impacted by runoff, increased 

surrounding urbanization, and mining can have effects 

on the park ecosystem (see “Ozarks Aquifer and Springs 

Protection” section; Covington 2002). Water quality 

discussions are beyond the scope of this report. VanaMiller (2007) presented the water resources report for 

the park. Schmitt et al. (2008) presented protocol for 

heavy-metal monitoring at the park. Davis and Barr 

(2006) detailed possible sources of microbiological 

contamination of the park’s water column and 

streambed sediment. The NPS Water Resources 

Division (http://www.nature.nps.gov/water/) can 

provide technical and regulatory assistance to resource 

managers at the park regarding water-related issues. 

Stream Sediment Storage and Load

In addition to their dissolved minerals (see “Caves and 

Karst Features and Processes” section), the streams 

and rivers at the park transport clastic material from 

fine clays to coarse gravels. As noted in the “Erosion” 

section, fine sediment can remain in suspension, causing 

turbidity and clouding the water which adversely 

affects riverine ecosystems (Covington 2002). Human 

use stirs up the bottom sediments, resuspending them 

and facilitating downstream transport (see “Erosion” 

section; Covington 2002; Vana-Miller 2007).

Stream bottom sediments are changing from finer 

grained to more gravel-rich, chert sediments because 

bank erosion removes the finer-grained components 

while the gravels remain (Vana-Miller 2007). Finer 

sediment sizes are “easier” for streams to transport. 

Gravel moves the most during high energy flow such 

as storms and flooding. Additionally, because chert 

does not dissolve like the carbonate bedrock, it is “left 

behind” and forms much of the gravel in park stream 

beds (Panfil and Jacobson 2001). 

Increased gravel content can lead to shallower streams 

because base flow moves more easily through gravel 

than finer sediments (Panfil and Jacobson 2001). A 

three-year study to better understand the geomorphic 

drivers of best habitat for mussel restoration should 

develop or update models of gravel transport (time 

frame of decades to centuries after human land 

disturbance) within the major rivers. This will help park 

resource managers understand how fast the gravel is 

moving through the system and address future issues 

(Victoria Grant, Ozark National Scenic Riverways, 

natural resources program manager, conference call, 20 

October 2015). 

To understand the changes in sediment storage and 

load and to predict future trends, park resource 

managers need an understanding of sediment influx 

(e.g., from breached or leaking tailings ponds, natural 

bank erosion, agriculture runoff) (Covington 2002). 

Stream flow regime models may help to determine why 

sediment loads are changing within the park. Sedimentload monitoring data (suspended and bed loads), 

though widely variable over space and time, are vital to 

understanding stream ecosystem dynamics. 

Figure 25. Photograph of gravel bars in the Jacks Fork. 

Finer grained material is washed away downstream leaving 

the coarsest material behind in the river channel. This 

changes the morphology of the channel and the fluvial 

habitat. If the bars persist above the water level long 

enough, vegetation stabilizes the feature. Photograph by 

Sid Covington (NPS Geologic Resources Division) taken in 

February 2002.
39

Climate Change Impacts

Historical climate data trends in the park vicinity are 

highly variable, both seasonally and annually (Fisichelli 

2013). Climate projections by Fisichelli (2013) for midcentury (2041–2070) suggest: 

● a 2.6°C (4.7°F) rise in temperature compared to

1971–2000 average,

● a 3-week longer frost-free period, and

● strong interannual and seasonal variability for

precipitation, including a 20% increase in the

annual number of >2.5 cm (1-in) rain events.

Potential impacts of climate change to natural and 

cultural resources at the park are pervasive and farreaching. Increasing temperatures will cause certain 

species to shift their range northward. The populations 

of some park species may decline because of limited 

dispersal abilities and specific habitat requirements 

(Fisichelli 2013). Because the park has been a refuge for 

relict species from ice age glaciations, these species may 

be especially sensitive to changing parameters (Fisichelli 

2013). Fisichelli (2015) summarizes forest vulnerability 

to different climate-change scenarios. 

More variable precipitation will cause both increased 

drought and flooding and in turn cause more frequent 

erosional disturbance to aquatic and streambank 

communities, as well as potential degradation of cultural 

resources (see “Flooding and Fluvial Geomorphology” 

and “Erosion” sections; Fisichelli 2013). Stretches of 

the river near springs with relatively consistent flow 

and cool temperatures (such as near source springs) 

will increasingly function as refugia or vital habitat for 

sensitive species (Fisichelli 2013).

If storm flows increase, bottom sediment will be more 

frequently mobilized. Peak discharges may be more 

erosive and likely to destabilize stream banks. If this 

causes stream widening, the channel sinuosity would 

be reduced and overall canopy cover may be affected. 

Increased storm flows would also disturb benthic 

habitats; a shallower and warmer benthic habitat with 

lower diversity would be expected (Panfil and Jacobson 

2001). 

Climate-change could also affect visitation at the 

park (Fisichelli 2013). Temperature strongly predicts 

visitation at the park and explained 99% of the variation 

in monthly visitation (Fisichelli and Ziesler 2015). 

Based on mid-century temperature projections, annual 

park visitation could potentially increase as much as 

46% (Fisichelli and Ziesler 2015). This increase in 

visitation could produce a correlative increase in landuse disturbances and negatively impact park natural 

resources and strain the capacity of park infrastructure. 

Case studies detailing how archeology can reveal 

paleoenvironmental data and illustrating ways in which 

archeological studies can advance efforts to better 

understand and respond to climatic shifts are ongoing 

at the park (Bringelson 2013). These studies integrate 

archeological and paleoclimate data sets to understand 

how environmental change has affected the human past 

(Dempsey and Bringelson 2013). The studies require 

thorough knowledge of late Quaternary landscape 

evolution in order to predict where people were at 

different times and what they were doing, as well as how 

climate change has influenced where the archeological 

resources may be preserved (Dempsey and Bringelson 

2013). If the park is interested in studying past change, 

understanding how the river corridors have changed 

along with shifting climates through time is an 

important component. This will increase understanding 

of the human-landscape interactions of the past, 

which may serve as a proxy for developing strategies 

to understand modern climate change (Dempsey and 

Bringelson 2013). Refer to the NPS Climate Change 

website for additional information: https://www.nps.

gov/subjects/climatechange/index.htm.

Caves and Associated Landscape 

Management

Cave features are nonrenewable resources and, with 

402 known caves, they are a fundamental component of 

the Ozarks landscape. See the “Cave and Karst Features 

and Processes” section. With the exception of guided 

tours in Round Spring Cavern, all caves in the park are 

closed to recreational access to minimize the spread of 

white-nose syndrome. Primary management issues 

associated with caves include the following concerns 

that are summarized below:

● sinkhole flooding and collapse,

● cave breakdown,

● slippery surfaces, precipitous drops, and drowning,

● radon,

● vandalism and dumping, and

● white-nose syndrome.
40

The Federal Cave Resources Protection Act of 1988 

requires the identification of “significant caves” in NPS 

areas, the regulation or restriction of use as needed to 

protect cave resources and inclusion of significant caves 

in land management planning. The act also imposes 

penalties for harming a cave or cave resources and 

exempts park managers from releasing specific location 

information for significant caves in response to a FOIA 

request (see also Appendix B). Documentation of caves 

provides a baseline for future management planning. 

Many park caves were only recently discovered 

and have yet to be surveyed; mapping of park caves 

continues (House 2015).

The regional karst features also contribute to the Ozarks 

aquifer (geologic map units Cp, Ce, Og, Or, and Ojc), 

which represents nearly 42% of Missouri’s usable 

groundwater (Orndorff et al. 2006; Vana-Miller 2007) 

and thus are important for groundwater quantity and 

quality considerations (see “Ozarks Aquifer and Springs 

Protection” section. Even slight disturbances can cause 

major impacts to the delicately balanced cave-aquatic 

and cave-terrestrial ecosystems. Damage or distortion 

to cave ecosystems can come from varied sources, close 

by (e.g., artificial lighting or groundwater pumping) or 

far away (e.g., acid rain or air pollution). 

Sinkhole Flooding and Collapse

Sinkholes occur throughout the park; sinkholes are part 

of the GRI GIS data, mapped as “Hazard Area Features” 

(Weary et al. 2016). Sinkhole flooding is a natural 

hydrologic process that occurs during intense rainfall 

when the quantity of storm water flowing into the 

sinkhole exceeds its capacity to drain into underlying 

conduits. The presence of muck and clayey silt (geologic 

map unit Qm), deposited in intermittently ponded 

sinkholes, attest to this process. The flow of water 

into and out of a sinkhole may change its morphology, 

potentially widening and/or deepening it. 

Most sinkholes form slowly through solution and 

subsidence and thus can be identified and avoided. 

The Jefferson City Dolomite and Roubidoux 

Formation (Ojc and Or, respectively) have the highest 

concentration of sinkholes in this part of Missouri. 

Most are closed-throat sinkholes; however, collapses 

have occurred historically (Orndorff et al. 2006). For 

example, a collapse created the opening to Devils Well 

and therefore, another large collapse is possible there 

(Lowell et al. 2010). Sudden sinkhole collapse could 

damage roads and other infrastructure within the 

monument with little to no warning. The depth of such 

a collapse is limited to the depth of the conduit below; 

however, the collapsed area may spread laterally over a 

significant distance. Areas most susceptible to collapse 

are shallow conduits at or just beneath the water table 

(Palmer 1990). Lowering of the water table may also 

contribute to sinkhole formation. Aley and Creath 

(1989) described instances of mine-related pumping 

contributing to “litters of sinkholes” forming. 

Geologists suspect many more unrecorded sinkholes 

exist in the park’s forests. The current data only include 

those that were identified on 6-m (20-ft) contour maps 

and fieldwork discoveries. There is a need to acquire 

bare-earth LiDAR to accurately identify and better 

characterize sinkhole areas in the park (Dave Weary, US 

Geological Survey, geologist, written communication, 

21 June 2016). 

Cave Breakdown

The term “cave breakdown” refers to the collapse of 

a cave ceiling or wall, or to the debris accumulated 

through such collapse. Collapse chambers exist at 

Round Spring Cavern (Lowell et al. 2010). The caves at 

the park continue to change over time. Cold weather 

(frost weathering), changes in airflow patterns, 

earthquakes, groundwater fluctuations, mineral growth, 

and anthropogenic activities contribute to breakdowns 

at scales ranging from small rocks to large boulders 

or slabs. In addition to earthquakes, mining, blasting, 

quarrying, or drilling may trigger cave breakdown. 

The following characteristics can signal areas of past or 

potential breakdown: (1) irregular patterns of wall and 

ceiling fractures with visible gypsum veins following 

the fractures; (2) breakdown debris containing thin, 

irregular splinters and shards of bedrock; (3) curved 

plates of bedrock hanging from the ceiling at steep 

angles; and (4) vertical gradation of collapse debris 

size, with irregular blocks at the base and symmetrical 

mounds of rock flour at the top (White and White 

2003). The breakdown process can be slowed in some 

cave areas by the installation of roof bolts into the 

cave roof and walls. These bolts anchor loose slabs to 

the adjacent intact rock in an attempt to stabilize the 

cave ceiling. Detailed cave mapping and assessment 

of potential hazards would help resource managers 

identify areas at particular risk. Refer to the “Slope 

Movement Hazards and Risk” section for additional 

information.
41

Slippery Surfaces, Precipitous Drops, and Drowning

Slippery surfaces and drowning dangers attest to the 

omnipresent dripping, flowing, and standing water 

in many of the park caves. Unauthorized cave use, 

particularly in closed caves, continues to be an issue 

for resource managers at the park (see “White-Nose 

Syndrome” subsection). 

Radon

Radon (222Rn) is a colorless, odorless, radioactive gas 

that naturally accumulates in buildings and enclosed 

underground spaces, such as caves and basements. 

Radon is created through the decay of uranium-238 

and thorium-232, which occur naturally in the park 

bedrock. Airflow can concentrate or transport radon 

throughout caves. Airflow in caves is a function of 

interior cave and exterior ambient temperatures and 

of the cave’s configuration. Temperature gradients 

produce pressure differences between the cave interior 

and exterior, causing air to move (Yarborough 1980, 

1981).

Uranium-enriched granites and rhyolites, and residuum 

developed on carbonate rocks in the Ozark Plateau 

Province are likely to produce radon and the province 

has a “moderate” overall radon potential according 

to a preliminary US Geological Survey assessment 

(Schumann 1993). According to the park website, 

elevated levels of radon occur in the park at Round 

Spring Cavern. Although this is perfectly normal in 

a limestone cave, the health effects, if any, are not 

currently known and therefore the park “discourages 

babies and pregnant women from participating” in the 

tour (see https://www.nps.gov/ozar/learn/education/

visiting.htm). Field (2007) discussed risks to cave 

workers (e.g., “tour guides”) from exposure to radon 

and noted that many NPS caves, including Round 

Spring Cavern, had elevated radon measurements. 

If concerns do arise, managers can contact the 

NPS Geologic Resources Division or the Missouri 

Geological Survey for assistance in developing a radon 

study plan. Information about residential exposure to 

radon in Missouri is available at the state’s Department 

of Health and Senior Services website (http://health.

mo.gov/living/environment/radon/index.php). Radon 

exposure is monitored at many NPS areas in the 

Midwest Region, including Hot Springs National Park 

in Arkansas (see GRI report by Thornberry-Ehrlich 

2013) and Mammoth Cave National Park in Kentucky 

(see GRI report by Thornberry-Ehrlich 2011). 

Vandalism, Visitor Access, and Dumping

Cave formations, or speleothems, are commonly 

fragile, and easily damaged by intentional vandalism 

or unintentional damage by humans. Touching the 

cave formations introduces lint and oils from the body 

and alters the character of the cave-formation system 

(Covington 2002). Speleothems and other features in 

the park have been broken and vandalized, and cultural 

resources in the cave have been stolen or damaged, 

and graffiti is an additional concern (Kimberly Houf, 

Ozark National Scenic Riverways, terrestrial ecologist, 

email, 16 December 2015). Other cave-use issues 

include trampling, muddy tracks on cave formations, 

littering, and bat disturbance (White 1985). The cave 

environment is slow to recover from damage and 

damaged speleothems many never “recover.” The 

Springfield Plateau Grotto (SPG), a chapter of the 

National Speleological Society (NSS) and the Cave 

Research Foundation (CRF) have been active in the 

park reattaching at least 78 speleothems in Shannon 

County (Jonathan Beard, SPG of the NSS, secretary/

treasurer, written communication, 10 July 2016). 

Social trails lead to the most popular caves and cause 

erosion, vegetation deterioration, and soil compaction 

(see also “Erosion” section; White 1985). Caves are 

also popular climbing destinations and park staff 

members working with the CRF continue to remove 

illegally-installed climbing gear from park caves, as 

well as identify and monitor cultural resources within 

the caves (House 2015). Looters have dug illegally 

at several park caves and many of these areas were 

refilled by volunteers from the SPG and CRF (Jonathan 

Beard, SPG of the NSS, secretary/treasurer, written 

communication, 10 July 2016). 

In the mid-1980s, park resource managers gated some 

cave entrances and installed educational signs to 

promote responsible cave behavior and talk about the 

importance and fragility of the cave ecosystem (White 

1985). Today, even though the majority of caves are 

closed to the general public, the park continues this 

style of educational management with closure postings 

throughout the park and at several well-known cave 

entrances. 

Sinkholes and caves throughout the region have 

historically been used as garbage dumps. Sinkholes 

are also the sites of some septic systems discharge 

(Covington 2002). Graffiti removal, trash collection, and 
42

trail marking and restoration are all projects in which 

volunteers with the SPG and CRF engage at Ozark 

National Scenic Riverways; as many as 13 park caves 

have experienced some restoration or improvements 

(Jonathan Beard, SPG of the NSS, secretary/treasurer, 

written communication, 10 July 2016). 

White-Nose Syndrome

White-nose syndrome (WNS) is a disease in bats 

caused by the fungus Pseudogymnoascus destructans. 

Discovered in the winter of 2006–2007 in a cave in New 

York, WNS has devastated hibernating bat colonies 

throughout the eastern United States and Canada. WNS 

has killed over 6 million bats within various species 

including Indiana and gray bats. WNS was discovered 

in gray bats in Shannon County, Missouri in May 2010. 

With this discovery, park managers closed all caves 

to recreational activities, except for guided trips into 

Round Spring Cave. While bats themselves are the 

primary way this fungus is spread, the closure of caves 

helps to ensure that people do not accidently transfer 

the fungus to new locations. (Castle and Cryan 2010; 

National Park Service 2012). See also

http://nature.nps.gov/biology/WNS/index.cfm and 

http://www.whitenosesyndrome.org/.

Once bats in a hibernating colony contract WNS, 

the colony usually suffers a 90% or greater loss in bat 

numbers. The disease thrives in colder temperatures 

such as those found in a hibernaculum and causes skin 

infections that prematurely awakens hibernating bats. 

This uses their stored reserves sooner than needed 

and the bats die of starvation. Since its discovery, 

research has helped biologists better understand this 

disease, but there is still much to know and there are 

no easy solutions to this problem. (Castle and Cryan 

2010; National Park Service 2012). Over the winter of 

2014–2015, members of the Cave Research Foundation 

noted that most of the caves visited in the park showed 

multiple species with obvious signs of fungus. As the 

disease spreads, bats are moving from known locales 

to other caves for hibernation (House 2015). To help 

prevent the spread of the disease and to better educate 

the public, visitors’ shoes are treated after Round Spring 

cave tours and more interpretive and educational signs, 

posters, and pamphlets are being developed (House 

2015).

Cave and Karst Management

A park-specific cave management plan was completed 

for the park in 1988 and revised in 2010 to reflect the 

cave closures associated with WNS (National Park 

Service 1988, 2010). 

The cave management plan provided strategies to 

achieve the following management goals (National Park 

Service 1988):

● Complete an inventory, evaluation and

classification of caves in the park and develop a

resource database integrated with information from

cooperating agencies and organizations.

● Establish guidelines for restrictions, access and

use of popular caves for recreational, interpretive

and scientific purposes that will assure resource

preservation.

● Assure the preservation of identified rare and

endangered cave species and their habitat.

● Provide opportunities for recreational cave use and

integrate park interpretive programs and materials

with resources protection, visitor safety and

resource management concerns.

● Evaluate existing problems of vandalism, overuse, impact on cave biota, safety hazards and

information needs identified in current surveys and

implement corrective actions.

● Establish a long-term monitoring system for cave

resources and visitor use which will document

impact and indicate need for management

response.

● Cooperate with other agencies, educational

institutions and organizations to increase public

awareness and appreciation of cave resources.

● Encourage investigations and scientific research

which will improve existing knowledge of Ozark

Riverways’ cave resources and further the park’s

management objectives for preservation, use and

interpretation.

As reported in the plan’s environmental assessment 

(National Park Service 1988), the preferred approach to 

the plan was to 

● extend basic inventory and classification to all park

caves;

● conduct comprehensive biological survey on major

and significant caves;

● increase cave ecology research;

● increase visitor information program;
43

● establish monitoring system; and

● establish an advisory cave management team.

For a servicewide perspective on cave management, 

refer to Land et al. (2013). That publication was part of 

a National Cave and Karst Research Institute

(http://www.nckri.org/) effort to compile survey results 

from NPS park units with cave and karst resources 

to help identify and prioritize research, remediation, 

interpretation, and other activities to best understand 

and manage cave and karst resources. As part of their 

goal to “identify the most critical needs in cave and karst 

research, management, and education/interpretation 

and provide recommendations on a general park-wide 

level and for specific parks”, they noted that Ozark 

National Scenic Riverways had (1) threatened and/

or endangered species, but critical habitats have not 

yet been identified; and (2) have recreational use of 

caves, but possess neither general nor cave-specific 

safety and rescue plans. They recommended having 

the US Fish and Wildlife Service (http://www.fws.gov/

endangered/) establish critical habitat for the threatened 

and endangered species found within the park, as well 

as establishing a general safety and rescue plan for all 

caves regardless of size (Land et al. 2013).

Baker et al. (2015) produced a guide to assist NPS 

cave managers in deciding what to inventory and 

monitor in caves and provides ways to do this work in a 

nationwide, cohesive manner. Their recommendations 

take into account the rare and/or cryptic nature of cave 

species, as well as the complex logistics often involved 

with the cave environment. They stress the importance 

of completing an inventory of cave resources before 

embarking on a monitoring plan. 

In the Geological Monitoring chapter about caves 

and associated landscapes, Toomey (2009) described 

methods for inventorying and monitoring caverelated vital signs, including the following: (1) cave 

meteorology, such as microclimate and air composition; 

(2) airborne sedimentation, including dust and lint;

(3) direct visitor impacts, such as breakage of cave

formations, trail use in caves, graffiti, and artificial cave

lighting; (4) permanent or seasonal ice; (5) cave drip and

pool water, including drip locations, rate, volume, and

water chemistry, pool microbiology, and temperature;

(6) cave microbiology; (7) stability issues associated with

breakdown, rockfall, and partings; (8) mineral growth

of speleothems, such as stalagmites and stalactites;

(9) surface expressions and processes that link the

surface and the cave environment, including springs,

sinkholes, and cracks; (10) regional groundwater levels

and quantity; and (11) fluvial processes, including

underground streams and rivers.

Ozarks Aquifer and Springs Protection

The Ozarks aquifer provides nearly 42% of Missouri’s 

usable groundwater (Vana-Miller 2007). The aquifer 

extends from the buried Cambrian confining unit 

below the Potosi Dolomite (geologic map unit Cp) to 

the surface including the Potosi Dolomite, Eminence 

Dolomite (Ce), Gasconade Dolomite (Og), Roubidoux 

Formation (Or), and Jefferson City Dolomite (Ojc) in the 

park (Aley and Creath 1989). This aquifer is unconfined 

and supplies water for domestic use and to the park’s 

springs; local surface waters are supplied in large part by 

groundwater springs (Aley and Creath 1989; Lowell et 

al. 2010). Groundwater at the park has been measured 

to travel up to 5 km (3 mi) per day (Vana-Miller 2007). 

Because of the characteristically high infiltration 

rates and permeability of karst landscapes (i.e., large 

subterranean conduits), as well as the presence of faults, 

little to no adsorption of any surficial contaminants 

occurs. This means that contaminants are readily 

transported through the system. 

Missouri’s noted thunderstorms introduce water and 

pollutants into the hydrogeologic system in “slugs” 

via discrete recharge zones (42% of the recharge 

to springs), losing streams (11% of the recharge to 

springs), sinkholes (10% of the recharge to springs), and 

other solution openings (Aley and Aley 1987; Aley and 

Creath 1989; Vana-Miller 2007). These contaminants 

flow quickly through the karst conduit system, emerge 

at springs, and into the Jacks Fork and Current rivers’ 

watersheds. Dye-tracing studies have also revealed 

complex and vast groundwater flow patterns crossing 

surface drainage divides and crisscrossing flow paths 

commonly far beyond park boundaries (see fig. 13; 

Aley and Creath 1989; Covington 2002; Mugel et 

al. 2009; Lowell et al. 2010). This lends an added 

element of unpredictability to the system’s response 

to contamination or adjacent land-use change. It also 

makes the management and protection of springs and 

rivers, whose flow emanates largely from springs, a 

resource management challenge at the park (Aley and 

Creath 1989). 
44

Land-use practices, especially land clearing, mining, 

and associated increases in sediment and nutrient 

loads, as well as other point and nonpoint discharges, 

present the greatest long-term threat to springs 

in the Ozarks (Bowles et al. 2011). Other threats 

to the spring ecosystem include disrupted stream 

channel geomorphology (see “Flooding and Fluvial 

Geomorphology” section), increased sediment 

deposition and bank erosion (see “Erosion” section), 

increased light penetration and water temperature, 

nutrient loading, and decreased leaf litter and woody 

debris. Dewatering of local aquifers, even the deepest 

ones, due to urbanization, mining operations, or 

agricultural use can cause loss of spring flow in the park 

and may contribute to sinkhole formation (see “Caves 

and Associated Landscape Management” section) Aley 

and Creath 1989; Covington 2002).

Mugel et al. (2009) provided quantitative landscape 

characteristics of areas within the spring, groundwater, 

and surface-water recharge areas. The recharge areas 

with the most open land and the least forest land per 

unit recharge area are Blue Spring (on Jacks Fork), 

Welch Spring, and Alley Spring. Similarly, the recharge 

areas with the least amount of publicly owned land 

per unit recharge area are Blue Spring (on Jacks Fork), 

Cave Spring, Welch Spring and the spring complex 

at Pulltite Spring. These areas may be more at risk for 

contamination or misuse.

The Heartland Network commissioned a land-use 

study in an effort to inventory and monitor land-use 

change. A resulting report by Hansen and Gryskiewicz 

(2003) presented (1) a characterization of the current 

landscape surrounding the park, (2) a summary of 

patterns of land-use change over time, (3) conceptual 

models showing links between ecological functioning 

within the park and land-use change, and (4) indicators 

and methods for monitoring landscape changes in the 

future. For the park, their study reinforced the idea that 

ecological functioning within the park depends heavily 

on the maintenance of surrounding habits. Conversion 

to urban (disturbed) landscapes may be a significant 

threat to park ecosystems. The most relevant land-use 

changes to monitor are those which reduce functional 

ecosystem size or eliminate unique habitats outside 

of park boundaries (Hansen and Gryskiewicz 2003). 

Land-cover change source data include the National 

Land Cover Dataset (available at: http://landcover.

usgs.gov/landcoverdata.php); Landsat satellite imagery, 

park-specific mapping with frequent updates; and the 

US Census Bureau (available at: http://www.census.

gov/).

As mentioned in the “Geologic Significance and 

Connections” section, the many springs at the park 

are vital water sources for the park’s rivers and harbor 

special habitats for specific species. These small and 

delicate ecosystems are more sensitive to disturbance 

than the adjacent waterways (National Park Service 

2015). Wading, swimming, and fishing, which may 

dislodge aquatic plants and disturb sediments, are 

prohibited in the park’s springs and spring branches. 

A list of laws and regulations protecting Ozark springs 

is available at: http://www.nps.gov/ozar/learn/nature/

spring-laws.htm. There is relatively little information 

on the physical and biological impacts of contaminated 

groundwater within springs or within surface water fed 

by springs (Bowles et al. 2011).

Lowell et al. (2010) presented a method using watertable data, detailed geologic mapping, and dye tracing 

to create a regional potentiometric surface and improve 

understanding about the flow towards Big Spring. 

Their approach showed the irregular nature of the 

groundwater flow, particularly in areas near prominent 

regional faults (e.g., the Wilderness Handy fault zone) 

that can act as highly permeable zones. A similar 

approach could be applied to other springs within 

the park to understand the source area and nature of 

groundwater flow. 

Audio-magnetotelluric (AMT) data, collected at Alley 

Spring, helped delineate the actual path of groundwater 

flow and could be collected for other park springs as 

well (Pierce and Weary 2009; Weary and Pierce, 2009). 

AMT soundings consist of electric and magnetic field 

measurements over a range of frequencies to identify 

the electromagnetic signature of a conduit and to map 

its location. Karst conduits are relatively low-resistivity 

areas in the AMT data (Weary and Pierce, 2009). 

Bowles et al. (2008, 2011) detailed the methodology of 

the Heartland Inventory and Monitoring Network’s 

spring monitoring program collecting data on aquatic 

vegetation, aquatic invertebrates, fish, habitat, and 

water quality from six large springs at the park. Using 

detailed geologic map data (e.g., GRI GIS data) with 

groundwater flow data and spring monitoring data 

could yield quantitative measures on the influence 

of geology and habitats at the park’s major springs. 
45

Expanding the monitoring to other key springs would 

increase the scope of understanding along the river 

corridors. 

The Missouri Geological Survey is involved in a multiyear project to redefine the recharge areas of springs 

across the state. Within the park, work was done on Big 

Spring, Mammoth, and Greer springs. Future projects 

focus on Alley and Welch springs. Publications on 

their results are forthcoming (Joe Gilman, Missouri 

Geological Survey, geologist, conference call 20 October 

2015). 

Erosion

Erosion is an ongoing natural weathering process 

on the landscape at the park. On average, 43% of all 

streambanks (alluvium and low terraces; geologic 

map units Qa, Qt, and Qtl) in a study of the Current 

and Buffalo rivers are moderately or severely eroding; 

cutbanks and protruding roots denote areas of erosion 

(see “Flooding and Fluvial Geomorphology” section; 

Panfil and Jacobson 2001). 

Human activities can impact erosion rates throughout 

the park. Examples of such activity in the Ozark region 

include the construction of roads, trails, parking 

lots, and other infrastructure; logging of forests with 

subsequent agricultural development; and human 

impacts from foot traffic, vehicles, domestic animals, 

river fords, and watercraft access points or put-in areas 

(Panfil and Jacobson 2001; Covington 2002; Greco 

2002). These activities increase erosion in three ways 

(1) Land surface disturbances can remove stabilizing

vegetation (2) When impervious or compacted surfaces

(e.g., roads and parking lots) are installed, they cause

increased runoff and sheet flow which may form rills

or channels on the sides of the structure. (3) Increased

river erosion (meandering) and formation of gravel

bars.

Erosion contributes to the sediment load of the rivers 

and streams. During very high precipitation, compacted, 

unpaved roads become sources of sediment and gravel 

roads can contribute 100 times more sediment than 

paved or abandoned roads (Panfil and Jacobson 2001; 

Covington 2002; Greco 2002; Vana-Miller 2007). 

Access points for canoes, rafts, and boats can be areas 

of high soil and sediment erosion because of human 

foot traffic, vehicles and trailers, and putting the 

watercraft into the river (fig. 26). Up to 20 fords are 

used in the park and, in many reaches, shallow depths 

permit crossings (Greco 2002). Unofficial roads and 

fords were created in some areas and contribute to local 

erosion (fig. 27; Greco 2002). Riparian land use also 

leads to increased gravel influx which homogenizes the 

aquatic habitat and fills in pools and interstices among 

cobbles (Covington 2002). Cobble and gravel beds are 

fish nesting sites and residences for aquatic insects and 

certain species of fish (e.g., darters) (Greco 2002). 

Where the stream banks become destabilized by human 

activity, stream meandering can increase, causing 

additional erosion and the formation of gravel bars. As 

the fine-grained material is carried away downstream 

in suspension and the gravel remains in the channel 

(see fig. 25; Covington 2002). Excessive sediment 

loads in rivers and streams can have negative impacts 

on the ecosystem (see the “Flooding and Fluvial 

Geomorphology” section) and impact the cave and 

karst system within the park. 

Covington (2002), Greco (2002), and GRI conference 

call participants, suggested the following action items 

for management of erosion at the park:

● Map and inventory roads and trails (active and

abandoned). This would supplement a 1991 roads

and trails study and environmental assessment.

● Use GPS to identify locations on drainages,

hillslopes, and other natural and cultural resources

impacted by erosion along roads and trails.

● Use GPS locations in a GIS to categorize and rank

road and trail locations based on impacts.

● Perform repeat photography at designated photo

points to monitor changes (see http://go.nps.gov/

grd_photogrammetry for information about using

photogrammetry for resource management).

● Develop a reclamation program for abandoned

roads and trails, including road closures, paving

high-use roads, upgrading artificial drainages,

reconstructing stream crossings, placing culverts or

water bars in strategic locations.

As detailed in the “Geologic Setting and Significance” 

section, land-use practices within and adjacent to 

the park have a controlling influence on the park’s 

ecosystem These landscape-scale changes have the 

potential to affect larger areas than the localized impacts 

also discussed in this section (see “Ozarks Aquifer and 

Springs Protection” section). 
46

Figure 26. Photographs of eroded streambanks at unauthorized access points. Human use at these areas can accelerate 

erosion and stream bank degradation. Photographs by Deanna Greco (NPS Geologic Resources Division) taken in April 

2002.
47

Paleontological Resource Inventory, 

Monitoring, and Protection

Fossils are common in Ozark National Scenic Riverways 

and are found in the rocks of the park, within caves, and 

associated with cultural resources. There are fossils in 

park and outside repository museum collections. Refer 

to the “Paleontological Resources” section for more 

information. 

All paleontological resources are nonrenewable and 

subject to science-informed inventory, monitoring, 

protection, and interpretation as outlined by the 

2009 Paleontological Resources Preservation Act (see 

Appendix B). As of August 2016, National Park Service 

regulations associated with this act had been signed. 

Regulations for other agencies in the Department of 

Interior were awaiting signatures.

Similar to cave formation damage and theft, fossil theft 

is an issue of concern for park resource managers 

(Victoria Grant, Ozark National Scenic Riverways, 

natural resources program manager, conference call, 

20 October 2015). Formal paleontological resource 

monitoring is not occurring within the park; however, 

current cave-focused archeological monitoring would 

detect fossil-resource disturbances in cave sediments 

and cave forming units (e.g., in the Eminence Dolomite, 

Gasconade Dolomite, and Jefferson City Dolomite [Ce, 

Og, and Ojc]).

A field-based paleontological resource survey can 

provide detailed, site-specific descriptions and resource 

management recommendations that are beyond the 

scope of this report. Although a park-specific survey 

has not yet been completed for the park, a variety of 

publications and resources provide park-specific or 

servicewide information and paleontological resource 

management guidance. 

● The GRI source map Weary et al. (2016) and

published map (Weary et al. 2014) summarized

fossil content in geologic units mapped in the park

and surrounding area.

● Santucci et al. (2001) compiled information

about fossils in caves in 35 parks, including Ozark

National Scenic Riverways.

● Hunt et al. (2008) summarized paleontological

resources for Ozark National Scenic Riverways

and other parks in the Heartland Inventory and

Monitoring Network and provided the following

Figure 27. Photographs of erosion along roads and social 

trails. Some areas are crisscrossed with trails and further 

use widens areas of impact along the streambanks. 

Photographs by Deanna Greco (NPS Geologic Resources 

Division) taken in April 2002.
48

preliminary recommendations for paleontological 

resource management: 

□ Conduct field inventories for paleontological resources to more fully document in situ

and karst (cave and overhang) occurrences of

fossils. Consider a formal site documentation

and condition assessment for significant fossil

localities. Monitor significant sites at least once

a year in the future.

□ Have park staff members observe exposed

cliffs, other erosional bedrock, rivers and

streams (especially during times of low water

levels) and karst features for fossil material

while conducting their usual duties. Document

any observations with photographs using a

common item (e.g., pencil) for scale. Fossils and

their associated geologic context (surrounding

rock material) should be documented but left

intact. Except for permitted scientific research,

paleontological resources should remain in situ

unless they are subject to imminent threats by 

artificially accelerated earth surface processes

or anthropogenic impacts.

□ Contact the NPS Geologic Resources Division

for paleontological resource management or

interpretation assistance.

● In the Geological Monitoring chapter about

paleontological resources, Santucci et al. (2009)

described five methods and vital signs for

monitoring in situ paleontological resources: (1)

erosion (geologic factors), (2) erosion (climatic

factors), (3) catastrophic geohazards, (4) hydrology/

bathymetry, and (5) human access/public use.

Slope Movement Hazards and Risks

As described in the “Slope Movements” section, slope 

processes—primarily rockfalls—occur at the park. 

Slope deposits such as colluvium and landslide deposits 

(geologic map units Qc and Qls, respectively), as well as 

residual and colluvial material on terrace-like landforms 

(QTtrc) attest to areas of past slope movement; these 

areas could experience future slope movements (Weary 

et al. 2014). Landslide scars attest to long-past slope 

movements where there has been no sizeable movement 

in recent years (Dave Weary and Randy Orndorff, 

US Geological Survey, conference call, geologists, 20 

October 2015). Slope movements, typically in the form 

of small slumps, and rockfalls are an ongoing item of 

concern for park resource managers (Conference call 

participants, 20 October 2015). Slope movements also 

affect caves (e.g., cave breakdown or sinkhole slumping; 

see “Caves and Associated Landscape Management” 

section). 

These processes are natural elements of landscape 

change. They become hazards when visitors hike or 

boat near the base of cliffs or in caves (see “Caves 

and Associated Landscape Management” section). 

Particularly hazardous areas are those with visible 

cracks, loose material, or overhangs.

There are many options that park managers can 

consider to reduce risk associated with slope movement 

hazards. One is visitor and staff education regarding 

the potential risks. Verbal warnings by park rangers, 

or signs and other written notices posted at visitor 

centers, trailheads, and/or websites is one option to 

educate visitors. Another option is limiting access to 

potentially hazardous sites via fencing, ropes, or other 

barriers. These options should be assessed by NPS 

staff with regards to impacts to the natural experience, 

fiscal limitations, visitor access, and maintenance 

requirements.

If funding permits, resource managers could consider 

obtaining quantitative information to assess the 

frequency and magnitude of rockfall and other slope 

movements in high visitation areas. A photomonitoring 

program is one possibility. The Geoscientist-in-theParks program (http://go.nps.gov/gip) is an option to 

support such a project. The NPS Geologic Resources 

Division Photogrammetry website (http://go.nps.gov/

grd_photogrammetry) provides examples of how 

photographic techniques support structural analysis of 

rockfall areas.

The following references provide additional 

background information, suggested vital signs, and 

resources for assessing and documenting slope 

movements:

● Weary et al. (2014) provided park-specific examples

and photographs of rockfall and other hazards.

● In the Geological Monitoring chapter about

slope movements, Wieczorek and Snyder (2009)

described five vital signs for understanding

and monitoring slope movements: (1) types of

landslide, (2) landslide causes and triggers, (3)

geologic materials in landslides, (4) measurement

of landslide movement, and (5) assessment of

landslide hazards and risks.
49

● US Geologic Survey publication The landslide

handbook—A guide to understanding landslides

(Highland and Bobrowsky 2008).

● US Geological Survey landslides website

(http://landslides.usgs.gov/).

● NPS Geologic Resources Division Geohazards

website (http://go.nps.gov/geohazards).

● NPS Geologic Resources Division Slope Movement

Monitoring website

(http://go.nps.gov/monitor_slopes).

Seismic Activity Hazards and Risks

Faults crisscross much of the park (see “Faults and 

Fractures” section). The majority of these faults are 

ancient structures and no longer active (Dave Weary, US 

Geological Survey, geologist, written communication, 

21 June 2016). Earthquakes are ground vibrations 

or shaking that occur when rocks suddenly move 

along a fault, releasing accumulated energy (Braile 

2009). Earthquake intensity or magnitude ranges 

from imperceptible by humans to total destruction of 

urbanized areas and alteration of the landscape(table 

3). The “Richter magnitude” is a measure of the energy 

released by an earthquake. Earthquakes can damage 

park infrastructure such as bridges, roads, and building 

foundations directly or trigger other hazards, such as 

slope movements on the steep bluffs along Current 

River or Jacks Fork or ceiling collapse within park caves, 

which may impact park resources, infrastructure, or 

visitor safety. Braile (2009), the NPS Geologic Resources 

Division Seismic Monitoring website (http://nature.

nps.gov/geology/monitoring/seismic.cfm), and the US 

Geological Survey Earthquakes Hazards website

(http://earthquake.usgs.gov/) provide more information.

Large earthquakes are not common in south-central 

Missouri; however, the region—and most of the eastern 

United States—shook during epic earthquakes 200 

years ago. From 1811–1812, the largest earthquakes 

ever recorded in the continental United States 

(approximately magnitude 8.0) occurred along the 

New Madrid fault. The massive earthquakes were felt 

throughout an area of 130,000 km2 (50,000 mi2). The 

New Madrid Seismic Zone (red and orange area on fig. 

28) is centered along the Mississippi River valley where

Arkansas, Missouri, Illinois, Kentucky, and Tennessee

converge, about 150 km (93 mi) southeast of the park.

Intra-plate seismic zones such as the New Madrid

Seismic Zone are far from plate boundaries, which are

the typical locations of earthquakes (Chapman et al. 

2002). The US Geological Survey created a variety of 

general interest publications marking the bicentennial 

of the New Madrid earthquakes (e.g., Williams et 

al. 2010, 2011). See also http://earthquake.usgs.gov/

earthquakes/states/events/1811-1812.php and the 

earthquakes page by the Missouri Geological Survey 

http://dnr.mo.gov/geology/geosrv/earthquakes.htm. 

Table 3. Seismic scale and list of notable earthquakes that 

affected the park and surrounding area.

Notable Local 

Earthquakes Modified Mercalli Scale

none reported I: Detectable only by sensitive instruments 

(Imperceptible shaking)

none reported II: Detectable by few persons at rest, especially

on upper floors; suspended objects may swing

none reported

III: Detectable noticeably indoors, but not always 

recognized as earthquake; standing autos rock 

slightly; vibration like passing machinery

June 18, 2002

IV: Detectable indoors by many persons, 

outdoors by few; at night, some may awaken; 

dishes, windows, doors disturbed, autos rock 

noticeably

June 10, 1987

November 9, 1968

1976

V: Detectable by most people; some breakage

of dishes, windows, and plaster; disturbance of 

tall objects

January 4, 1843

October 31, 1895

VI: Detectable by everyone, many frightened and 

run outdoors; falling plaster and chimneys, minor 

damage

December 16, 1811

January 23, 1812

February 7, 1812

VII: Everyone runs outdoors; damage to buildings 

varies depending on quality and material of 

construction; noticed by auto drivers

none reported

VIII: Panel walls thrown out of frames; fall of 

walls, monuments, chimneys; sand and mud 

ejected from ground; auto drivers disturbed

none reported

IX: Buildings shifted off foundations, cracked, 

thrown out of plumb; ground fractured; 

underground pipes broken

none reported X: Most masonry and frame structures destroyed; 

ground fractured, rails bent, landslides triggered

none reported

XI: Few structures remain standing; bridges 

destroyed; ground fissures, pipes broken, 

landslides, rails bent

none reported

XII: Total damage; waves seen on ground 

surface, lines of sight and level distorted, objects 

thrownup in air

(Catastrophic destruction)

The Modified Mercalli scale details the physical effects of different 

earthquake magnitudes. The 1811 and 1812 earthquakes were the 

major New Madrid earthquakes. Information from Johnston and 

Schweig (1996), and Williams et al. (2011).
50

The US Geological Survey’s earthquake probability 

maps indicate that the probability of a moderate 

(magnitude-5.0) or greater earthquake within 100 years 

in this area is 2% to 10% (fig. 28; Petersen et al. 2008).

More recent earthquakes have been much smaller. On 

Friday, 16 October 2015, a magnitude 3.4 earthquake 

was felt at the park. It shook park headquarters 

building, rattled windows, and was felt by people 

throughout the area. The epicenter was 40 km (25 mi) 

away from the park (Larry Johnson, Ozark National 

Scenic Riverways, superintendent, conference call, 20 

October 2015). The US Geological Survey event page 

for the earthquake provides additional information: 

http://earthquake.usgs.gov/earthquakes/eventpage/

nm60119416#general_region. 

A US Geological Survey emeritus geologist (John 

Tinsley) is currently studying caves in the central 

and eastern United States for evidence of ancient 

earthquakes (“paleoseismicity”) contained in cave 

formations (e.g., breakage and “healing” or new growth 

of speleothems). Caves in the Ozarks have revealed a 

500-year recurrence interval for “large” (magnitude

>6) earthquakes (Tinsley 2014; Dave Weary and Randy 

Orndorff, US Geological Survey, geologists, conference

call, 20 October 2015).

For parks interested in monitoring earthquakes 

and understanding seismic history, the Geological 

Monitoring chapter about earthquakes and seismic 

activity described the following methods and vital 

signs for understanding earthquakes and monitoring 

seismic activity: (1) monitoring earthquakes, (2) 

analysis and statistics of earthquake activity, (3) analysis 

of historical and prehistoric earthquake activity, (4) 

earthquake risk estimation, (5) geodetic monitoring and 

ground deformation, and (6) geomorphic and geologic 

indications of active tectonics (Braile 2009). Missourispecific information is available at http://earthquake.

usgs.gov/earthquakes/states/?region=Missouri. The 

Missouri Geological Survey’s website http://dnr.

mo.gov/geology/geosrv/

earthquake.htm is another 

resource for information 

about seismicity in Missouri. 

Abandoned Mineral 

Lands

According to the NPS 

abandoned mineral lands 

(AML) database (accessed 14 

July 2015) and Burghardt et al. 

(2014), the park contains one 

AML feature at one site. The 

Partney quarry was a surface 

mine for dolomite building 

stone; it was approximately 90 

m (300 ft) long and 30 m (100 

ft) wide. This quarry was used 

by the Civilian Conservation 

Corps during construction of 

infrastructure at Big Spring 

in the 1930s. This quarry 

could provide replacement 

stone if repair of historic 

structures was needed. Big 

Spring Granite (geologic map 

unit Yg) was quarried locally 

south and east of Van Buren, 

Missouri, about 100 m (330 

Figure 28. Probability map of the occurrence of earthquakes with magnitudes 

greater than 5.0. This probability assumes a 100-year timespan and a 50-km (30-mi) 

radius around Eminence, Missouri. Ozark National Scenic Riverways is northwest 

of the New Madrid Seismic Zone (warm colors to the east), whose recent (> 5.0 

magnitude) epicenters are the solid black circles. Graphic was generated by the 

US Geological Survey’s Probabilistic Seismic Hazards Assessment (PSHA) mapping 

program (https://geohazards.usgs.gov/eqprob/2009/index.php). 
51

ft) north of the park boundary on Brown Road (Lowell 

et al. 2010). There are numerous prospecting pits and 

some mine workings in areas within and near the park 

typically around the periphery of the igneous rock 

outcrops. Most of these are pre-World War II prospects 

for iron, copper, and manganese (Grawe 1943; Dave 

Weary, US Geological Survey, geologist, written 

communication, 21 June 2016).

Abandoned mineral lands are lands, waters, and 

surrounding watersheds that contain facilities, 

structures, improvements, and disturbances associated 

with past mineral exploration, extraction, processing, 

and transportation, including oil and gas features and 

operations, for which the NPS takes action under 

various authorities to mitigate, reclaim, or restore in 

order to reduce hazards and impacts to resources.

AML features and disturbed lands include adits, 

prospects, shafts, structures, open pits, tunnels, waste 

rock piles, mills, wells, and landform modifications such 

as service roads, drainage diversions, and drill pads. 

AML features pose a variety of resource management 

issues such as visitor and staff member safety and 

environmental quality of air, water, and soil. AML 

features can also provide habitat for bats and other 

animals, some of which may be protected under the 

Endangered Species Act or state species listings.

Resource management of AML features requires an 

accurate inventory and reporting. All AML features 

should be recorded in the Servicewide AML Database 

(the NPS Geologic Resources Division will provide 

assistance). An accurate inventory identifies human 

safety hazards and contamination issues, and facilitates 

closure, reclamation, and restoration of AML features. 

When appropriate for resource management and visitor 

safety, AML features can also present opportunities for 

interpretation as cultural resources. No AML features 

within the park have been mitigated and no additional 

features at the site are in need of mitigation (Burghardt 

et al. 2014). The NPS AML website, http://go.nps.

gov/aml, provides more information. The Missouri 

Geological Survey’s website (http://dnr.mo.gov/geology/

geosrv/index.html) offers “GeoSTRAT”—a geosciences 

technical resource assessment tool with features such 

as the locations of springs, mines, and sinkholes on an 

interactive map. Their website also includes an oil and 

gas database with permit locations for more than 12,000 

wells. 

External Mineral Development

Ozark National Scenic Riverways is immediately south 

of the world’s largest lead and zinc mining district—the 

Viburnum Trend (see fig. 2). Mining in this “New Lead 

Belt” began in the early 1950s. Tailings from past mining 

and potential future exploration or development are 

possible sources of contamination and other impacts 

to the park’s river and karst ecosystems (see also the 

“Ozarks Aquifer and Springs Protection” section; 

Schmitt et al. 2008; Schumacher 2008). 

Mining and oil and gas extraction is conducted 

adjacent to dozens of National Park Service areas. 

The National Park Service works with adjacent land 

managers and other permitting entities to help ensure 

that National Park System resources and values are not 

adversely impacted by external mineral exploration and 

development. Potential impacts include groundwater 

and surface water contamination, erosion and siltation, 

introduction of exotic plant species, reduction of 

wildlife habitat, impairment of viewsheds and night 

skies, excessive noise, and diminished air quality. Visitor 

safety and overall degradation of the visitor experience 

are particular concerns. The NPS Geologic Resources 

Division Energy and Minerals website,

http://go.nps.gov/grd_energyminerals provides 

additional information. 

In the Viburnum Trend, mine waste (tailings) is 

held in large ponds impounded by earthen dams. 

Complete or partial failure of those structures could 

cause vast amounts of toxic sediment containing lead, 

zinc, cadmium, cobalt, and nickel, acidic water, and 

mineral-extraction chemicals to be introduced into the 

surface waters, and through the karst system into the 

groundwater (Covington 2002; Vana-Miller 2007). 

Karst systems are particularly susceptible to the 

introduction and transportation of contaminants 

because rock is fractured and has rapid connections 

between surface and subsurface water. Sinkholes, 

conduits, and springs are probably facilitating the 

transport of mine-related contaminants from runoff 

and discharge (Schmitt et al. 2008). Abandoned 

tailings from historic mining are already making their 

way into park streams. They are differentiated from 

natural, local-sourced sediment by their size, shape, 

composition, and quality. These tailings are either 

leaking from beneath the tailing ponds impoundment 

or from ponds that have been breached (Covington 
52

2002). Dye-tracing in 2008 revealed a subsurface 

connection between a losing reach of Logan Creek, 

downstream from the active Sweetwater Mine, and Blue 

Spring, 16 km (10 mi) to the southwest, on the Current 

River. Discharge from the mine complex composes 

as much as 68% of the discharge into upper Logan 

Creek, which eventually resurges at Blue Spring. This is 

changing water chemistry within Blue Spring and also 

the mineralogy and concentrations of trace elements in 

streambed sediments in Blue Spring and downstream 

in Current River (Schumacher 2008). Sediments are 

enriched in cobalt and nickel, as well as galena and 

cerrusite minerals. Three breaches from the Sweetwater 

Mine tailings pile in 1977 and 1978 released mine waste 

into the karst system. Increased turbidity from these 

releases extended more than 64 km (40 mi) downstream 

in Logan Creek and into Blue Spring on the Current 

River (Schumacher 2008). 

Mining can also involve significant groundwater 

pumping that, because of the complicated, 

interconnected, karstic groundwater system at the 

park, could impact flow at the major springs and 

consequently within the rivers themselves (see “Ozarks 

Aquifer and Springs Protection” section; Aley and 

Creath 1989). 

Areas around the park are being explored for potential 

mining (National Park Service 2015). Future mining 

potential needs to remain an issue of attention for park 

resource managers (Joe Gilman, Missouri Geological 

Survey, geologist, conference call 20 October 2015). 

More than 300 exploration holes were drilled for 

lead and zinc in the Mark Twain National Forest west 

of Big Spring. Most of these holes are in the spring’s 

recharge area and could introduce toxic drilling fluids 

into the karst conduit system (Covington 2002; Schmitt 

et al. 2008). Lead and zinc exploration is occurring 

in the Eleven Point River area, just south of the park. 

A company formerly interested in prospecting there 

has withdrawn their proposal; however, many leases 

may become active again with changes in the mineral 

economy (Dave Weary, US Geological Survey, geologist, 

conference call, 20 October 2015). There may be 

economically viable lead, zinc, copper, and cobalt 

deposits on Missouri Department of Conservation 

lands within the recharge areas for major springs on the 

Current River upstream of the confluence with Jacks 

Fork and elsewhere (Vana-Miller 2007; Joe Gilman, 

Missouri Geological Survey, geologist, conference call, 

20 October 2015). Orndorff et al. (2006) and Weary et 

al. (2010) performed detailed mapping to show how 

cave, spring, and sinkhole formation in the Ozarks 

occurs within the geologic framework (see “Cave 

and Karst Features and Processes” section). Those 

publications provide important information about 

the potential effects of land-use decisions (including 

mining) in a karstic terrain. Schmitt et al. (2008) 

presented protocols for monitoring mining-related 

metals in the park’s river system. In 1989, a Sole Source 

Aquifer designation was pursued for the Big Spring 

recharge area to protect the aquifer from mineral 

leases and mining permits (Aley and Creath 1989). The 

Environmental Protection Agency denied the petition 

in 1992 based on the questionable conclusion that 

alternative sources of domestic water supplies were 

available (Chilman et al. 1996). 

Regionally, the lead and zinc deposits occur in the 

Cambrian Bonneterre Formation (not mapped in the 

GRI GIS data as the unit is not exposed at the surface 

within the park; however, the unit is shown on crosssections through throughout the park area; see Weary 

et al. 2014, sheet 2). Mineralization occurred in the 

Bonneterre near the buried Proterozoic igneous rocks 

(igneous knobs; “Y” geologic map units) throughout the 

area because of a contrast in permeability between the 

igneous protrusions and overlying sedimentary rocks 

during the injection of mineral-laden fluids in the late 

Paleozoic (Lowell et al. 2010; Mouat and Clendenin 

1975). Weary et al. (2014) show the proposed 

prospecting-permit-applications area in Mark Twain 

National Forest. 

The Missouri Geological Survey’s website (http://

dnr.mo.gov/geology/geosrv/index.html) offers 

“GeoSTRAT”—a geosciences technical resource 

assessment tool. Relevant to external mineral 

development are the locations of drill areas, oil and 

gas wells, wells, mines, prospects, and metallic mineral 

waste management areas.
53

Geologic History

This chapter describes the chronology of geologic events that formed the present landscape.

The geologic foundation of the park reveals a long 

history of landform development and change spanning 

more than 1.5 billion years. The oldest rocks in Ozark 

National Scenic Riverways were created when calderas 

erupted as an ancient supercontinent was pulled 

apart. Hundreds of millions of years later, shallow seas 

inundated the area. Over millennia, thick stacks of 

fossiliferous sedimentary rocks accumulated atop and 

adjacent to the volcanic rocks. In more recent history, 

erosion, weathering, and slope movements shaped 

the river valleys of the park. Trickling groundwater 

dissolved vast conduits in the soluble carbonate rocks 

to form the characteristic karst features of southeastern 

Missouri. Today, slope deposits collect at the base of 

slopes and the Current River and Jacks Fork continually 

modify their channels and adjacent floodplain areas. 

Water continues to dissolve bedrock, enlarging caves, 

forming sinkholes, and flowing from springs. 

Mesoproterozoic Era (1.6–1.0 billion years 

ago): Building the Ozark Dome, Volcanism, 

Deformation, and Erosion

Basement rocks across southern Missouri record 

tectonic events that occurred more than 1.5 billion 

years ago along the southern margin of the North 

American craton. At this time, a continental rift began 

to form as the ancient supercontinent of Rodinia began 

to break apart. Rocks from this time period are found 

in a northwest-oriented, 12–20 km- (7–20 mi-) thick 

wedge of granite, rhyolite, and clastic sedimentary rocks 

across southern Missouri (Lowell et al. 2005; Darnell 

et al. 1995). The Mesoproterozoic igneous rocks 

exposed within the park (“Y” geologic map units) were 

likely associated with massive volcanoes that erupted 

along the edges of that rift (fig. 29A; Lowell et al. 2010; 

Weary et al. 2014). Within the Current River basin, 

a cluster of about 50 rhyolite and two granite knobs 

(fig. 30) protrude to the surface through the adjacent 

Paleozoic sedimentary rocks; many other knobs likely 

remain buried. These make up the Eminence-Van 

Buren volcanic field which is part of the core of the 

Ozark dome—an asymmetrical structure in which the 

center is high and the rock layers slope (dip) away from 

the center (Lowell et al. 2010; Weary et al. 2014). The 

volcanic field erupted more or less contemporaneously 

with movement along strike-slip faults about 1.48 and 

1.38 million years ago (Lowell and Clendenin 2003; 

Lowell et al. 2010). The oldest geologic structures in the 

park, the faults that only deform the Mesoproterozoic 

rocks, are additional evidence of these cataclysmic 

events (Weary et al. 2014). 

The Eminence caldera erupted violently because of its 

high silica content, and eventually amassed an expansive 

lava plateau with some peaks (Unklesbay and Vineyard 

1992; Schaper 2015). Volcanic rocks on the surface 

cooled as fine-grained or porphyritic (conspicuous 

crystals in a fine-grained or glassy matrix) rhyolite lava, 

tuff, and breccia (Yrm, Yvc, Ysc, Ysi, Ysm, Ymm, Yltm, 

Ycu, and Ycl; Weary et al. 2014; Schaper 2015). Molten 

rocks which cooled below ground between eruptions 

formed shallow bodies of granite (Yg; Weary et al. 2014; 

Schaper 2015). Caldera eruptions blew away entire 

mountaintops and fractured surrounding rocks where 

additional volcanoes erupted. Following eruptions, the 

caldera subsided or collapsed incrementally (Lowell 

2000). This left subsurface plutons of granite closer 

to the surface than before (Unklesbay and Vineyard 

1992; Schaper 2015). The Coot Mountain units (Ycl and 

Ycu, tuff of Little Thorny Mountain (Yltm), rhyolite of 

Russell Mountain (Yrm), and rhyolite of Sutton Creek 

(Ysc) are associated with these eruptions, caldera 

formation, and collapse (Lowell et al. 2010; Weary et 

al. 2014). The rocks were rotated and steeply inclined, 

about 65°–90°, when the caldera collapsed (Lowell et 

al. 2010). Contemporaneous, steep-walled domes of 

granitic rock (e.g., Big Spring quad granite; Yg) intruded 

the volcanic rocks about 1.47 billion years ago (Lowell 

et al. 2010; Weary et al. 2014). The rhyolite of ShutIn Mountain and the Mule Mountain tuff (Ysi and 

Ymm, respectively) were erupted onto an intra-caldera 

surface after rotation and collapse so they remain, 

nearly horizontal (Lowell et al. 2010). Post-collapse, 

volcaniclastic (sedimentary rocks made up of clasts 

of volcanic rocks) unconformably overlie the volcanic 

rocks elsewhere in Missouri but are not mapped in the 

GRI GIS data. The boundary is marked by a distinct airfall tuff unit (Lowell et al. 2010). After about 100 million 

years of intense volcanic activity, weathering and 

erosion proceeded for at least a few hundred million 

years and there are no rocks from this time period 

mapped in the GRI GIS data (Schaper 2015; Weary et al. 

2016).
54

Figure 29A–C. Illustration of the evolution of the landscape and geologic foundation of Ozark National Scenic 

Riverways. Continued on next page. Graphics are not to scale. Colors are standard colors approved by the US 

Geological Survey to indicate different time periods on geologic maps, and correspond to the colors on the Map Unit 

Properties Table. Map symbols are included for the geologic map units mapped within the park. Graphic by Trista L. 

Thornberry-Ehrlich (Colorado State University) with information from Lowell et al. (2010) and Weary et al. (2014). 
55

Figure 29D–E. Illustration of the evolution of the landscape and geologic foundation of Ozark National Scenic 

Riverways. Continued from previous page. Graphics are not to scale. Colors are standard colors approved by the US 

Geological Survey to indicate different time periods on geologic maps, and correspond to the colors on the Map Unit 

Properties Table. Map symbols are included for the geologic map units mapped within the park. Graphic by Trista L. 

Thornberry-Ehrlich (Colorado State University) with information from Lowell et al. (2010) and Weary et al. (2014). 
56

Paleozoic Era (541–252 million years ago): 

Marine Inundation, Deposition, and Erosion, 

Assembling Pangaea

More than 500 million years ago, global sea level rose 

and shallow seas inundated much of southeastern 

North America. Thick marine carbonates (dominantly 

limestone and minor amounts of terrestrial (sandy) 

sediments were deposited on the seafloor and in 

valleys surrounding the topographic highs formed by 

the Mesoproterozoic rocks (figs. 29B and 31; Lowell et 

al. 2010; Schaper 2015).This irregular surface resulted 

in great variations in the thicknesses and distributions 

of contemporaneous Cambrian units (Lowell et al. 

2010). It also represents a tangible time-gap in the 

geologic rock record that can be spanned with a human 

hand—at the unconformable contact between older, 

volcanic rocks and marine sedimentary rocks hundreds 

of millions of years younger (fig. 32; Unklesbay and 

Vineyard 1992; Thompson 1995; Schaper 2015). 

By the late Cambrian, most of North America was 

very near Earth’s equator (Levin 1999; Unklesbay 

and Vineyard 1992; Schaper 2015). Shallow, tropical 

seas still covered the park and the open ocean was 

only a few hundred kilometers away, near what is now 

central Arkansas (fig. 29C; Unklesbay and Vineyard 

1992; Thompson 1995; Schaper 2015). Terrestrial 

sediment sources were scarce and shallow-water 

carbonate deposition piled up layers that eventually 

became the upper Cambrian Potosi Dolomite (Cp) and 

Eminence Dolomite (Ce), and the lower Ordovician 

Gasconade Dolomite (Og), Roubidoux Formation 

(Or), and Jefferson City Dolomite (Ojc) (Repetski 

et al. 1998; Lowell et al. 2010; Weary et al. 2014). A 

second group of faults in the park were active at one or 

more times prior to the deposition of the Ordovician 

Gasconade Dolomite (Og), Roubidoux Formation 

(Or), and Jefferson City Dolomite (Ojc) (Weary et al. 

2014). These deformed the Cambrian and older rocks 

(Ce, Cp, and “Y” units). Fossil trilobites, gastropods, 

Figure 30. Aerial image of Mesoproterozoic rhyolite knob of the Upper Coot Mountain unit (Ycu) surrounded by 

Cambrian dolomites. Image is near the confluence of Current River and Jacks Fork. Bedrock exposures are more 

common on the igneous knobs and vegetation is qualitatively sparser. Bold red line is the boundary of Ozark National 

Scenic Riverways. Dashed black lines are contacts between the geologic map units. Graphic by Trista Thornberry-Ehrlich 

(Colorado State University) using GRI map data from Weary et al. (2016) and ESRI World Imagery basemap (accessed 9 

May 2016).
57

and other mollusks in the Cambrian and Ordovician 

rocks record the new types of ecosystems that 

followed the “Cambrian explosion” of new groups of 

marine organisms that evolved in the early Cambrian 

(Thompson 1995; Hunt et al. 2008; Schaper 2015). 

The Potosi Dolomite and Eminence Dolomite circle 

knobs of Mesoproterozoic rock, indicating that these 

knobs were likely islands jutting above the sea. Quartzrich sandstone layers and lenses within the Eminence 

Dolomite indicate periods of marine regression, 

when the seas retreated and nearshore, beach-like 

depositional environments prevailed (Lowell et al. 

2010). The exposed Mesoproterozoic igneous rocks 

may have provided a terrestrial sediment source for 

these layers. Following longstanding limestone and 

Figure 31. Paleogeographic maps of North America. The red star indicates the approximate location of Ozark National 

Scenic Riverways. Graphic complied by Trista L. Thornberry-Ehrlich (Colorado State University). Base paleogeographic 

maps created by Ron Blakey (Colorado Plateau Geosystems, Inc.), which are available at http://cpgeosystems.com/index.

html.
58

dolomite deposition, was a period of nondeposition or 

erosion. During this period, the top of the Eminence 

Dolomite was weathered into an irregular surface prior 

to the deposition of the Gasconade Dolomite. At this 

time, North America was moving north, away from the 

equator (Unklesbay and Vineyard 1992; Levin 1999; 

Schaper 2015). 

The Gunter Sandstone member of the Gasconade 

Dolomite (lower part of Og) was the first Ordovician 

unit deposited atop the erosional surface of the 

Eminence Dolomite. It signals a period of relatively 

rapid transgressive-regressive sea level changes with 

multiple unconformities within Og (periods when no 

rocks were deposited, or were subsequently eroded 

away) (Repetski et al. 2000; Lowell et al. 2010). Sands 

accumulated in high energy, nearshore, subtidal 

environments (Lowell et al. 2010). Eventually, deeper 

water settings returned and deposition of limestones 

(dolomites) and siliceous cherts resumed forming the 

rest of the Gasconade Dolomite. Sea level fluctuations 

and shifting environments alternately deposited 

sandstone, chert, and dolomite of the Roubidoux 

Formation and the more dolomite-rich Jefferson 

City Dolomite (Thompson 1995; Lowell et al. 2010; 

Weary et al. 2014; Schaper 2015). Mud cracks within 

the Roubidoux Formation formed during periods of 

exposure when sea level dropped (Lowell et al. 2010).

Bedrock units younger than the early Ordovician Period 

are not mapped at the park (Weary et al. 2014, 2016). 

Whatever units were deposited atop the Jefferson City 

Dolomite (Ojc) have since been removed by erosion. 

There is no evidence in the Cambrian and Ordovician 

rocks that they were ever buried by more than about 

1,500 to 2,700 m [5,000 to 9,000 ft] of rocks (Epstein et 

al. 1977; Repetski et al. 1998; Lowell et al. 2010). This 

is despite major tectonic events occurring as close as 

a few hundred kilometers of the park (fig. 29D; Cox 

1995; Lowell et al. 2010). During the late Paleozoic 

Figure 32. Photograph of unconformity. Thick beds of dark gray Eminence Dolomite (in background) dip off of a 

knob of lighter-colored Mesoproterozoic rhyolite (foreground) along Rocky Creek, about 14 km (9 mi) east-southeast 

of the town of Eminence. The contact between the two rock units is significantly unconformable, with about 980 

million years of missing record between them. This locality is described in Lowell and others (2010) as field trip stop 

7. US Geological Survey photograph by Richard Harrison, taken in 1998. Caption and photo courtesy David Weary (US 

Geological Survey).
59

Era, mountains were forming across much of eastern, 

southern, and western North America. About 200 km 

(124 mi) south of the park, the Ouachita Mountains 

were uplifted. At the same time, the Appalachian 

Mountains rose during the final Appalachian orogeny. 

Ancestral Rocky Mountains were also forming at this 

time. These tectonic forces likely fractured rocks in 

the park and moved them along strike-slip faults that 

correspond to the third and youngest group of faults 

mapped in the GRI GIS data (Weary et al. 2016). In 

the late Paleozoic Era, mineral-saturated, geothermal 

fluids flowed upward from deep below Earth’s surface 

to deposit lead-rich minerals along fractures and within 

pores that would later become mining areas such 

as the Viburnum Trend (Lowell et al. 2010). During 

this same event, other geothermal fluids altered the 

limestones that had been deposited earlier in the park 

to dolomite—the bedrock formations seen today. Heavy 

mineral deposition occurred at the interface between 

the Mesoproterozoic volcanic rocks and the adjacent 

Paleozoic sedimentary rocks. 

Mesozoic Era (252 million–66 million years 

ago): Pangaea Separation, Local Erosion, and 

Mississippi Embayment Subsidence

There are no rocks from the Mesozoic Era mapped 

within the park, however geologic events during the 

time period played a role in shaping the southeastern 

United States. At the dawn of the Mesozoic Era, 

all landmasses on Earth were assembled into the 

supercontinent Pangaea (fig. 31). Just a few tens of 

millions of years later, during the Triassic and Jurassic 

periods, rifting began to pull apart Pangaea. Africa 

and South America separated from North America, 

forming the still-widening Atlantic Ocean. This rifting 

also opened the Gulf of Mexico basin in the late 

Triassic or early Jurassic (Saucier 1994). The Gulf of 

Mexico continued to widen through the Cretaceous 

Period. During the Cretaceous, global sea level rose 

to the extent that the North American continent was 

divided by the Western Interior Seaway that stretched 

from the Gulf of Mexico to the Arctic Ocean. As 

the gulf expanded, the Earth’s crust between the 

southern Appalachians and Ouachita Mountains 

subsided creating the Mississippi Embayment. The 

topographically low Mississippi Embayment was 

inundated when sea levels were high (Unkelsbay and 

Vineyard 1992; Levin 1999; Schaper 2015). As sea levels 

fluctuated during the Late Cretaceous, the embayment 

alternated between shallow marine and fluvial 

environments. Sediments eroded from the Ouachita 

Mountains collected within the embayment. Although 

the waters of the embayment did not reach what is 

now the park, they did extend to near Cape Girardeau, 

Missouri, 120 km (75 mi) east of Eminence. Marine and 

near-marine sands, sandstones and clay were deposited 

across southeastern Missouri. Weathering, erosion, and 

fluvial incision were the dominant geologic processes 

operating in the park by the end of the Mesozoic Era, 

and the Ozarks continued to be an area of erosion and 

weathering continuing throughout the Cenozoic Era 

which followed (Unkelsbay and Vineyard 1992; Schaper 

2015). 

Cenozoic Era (the past 66 million years): River 

Valley Evolution and Ice Age Glaciation

Throughout the early Cenozoic Era (fig. 29E), periodic 

incursions from the Gulf of Mexico inundated the 

lower Mississippi Embayment, depositing thick layers 

of marine sediments that would eventually fill the 

embayment during the Paleocene and Eocene epochs 

(Saucier 1994). This had impacts on the development of 

the entire Mississippi River system, including Current 

River and Jacks Fork. Higher sea levels yield higher 

base levels and overall less incision by rivers upstream. 

By contrast, when sea level is lowered or the upstream 

land uplifted, the drop in base level causes incision and 

river-channel entrenchment. Fluvial geologic units (e.g., 

QTg and Qt) “perched” as terrace deposits above the 

modern floodplains record prior river levels (Weary et 

al. 2014a) that occurred when the base level was higher.

At the beginning of the Pleistocene Epoch, the system 

experienced a major change. Ice age glaciation was 

the single most significant geologic process to affect 

the modern geomorphology and geologic history 

of the lower Mississippi River valley (Saucier 1994). 

During repeated continental glaciations (ice ages) 

of the Pleistocene Epoch (between 2.6 million years 

ago and approximately 12,000 years ago) thick sheets 

of ice advanced and retreated over much of North 

America. Glacial ice never reached farther south than 

central Missouri (see fig. 2), but the global effects of 

their presence are recorded in the geologic units in the 

Ozarks. Weathering was accelerated in the colder, less 

vegetated settings causing more accumulation of slope 

deposits such as landslides (Qls) and colluvium (Qc). 

A cover of Pleistocene, wind-blown loess (Qtl and Ql) 

of varying thicknesses extends over all of the park area 

except for the highest parts of the Ozarks (Bunker et al. 
60

1988; Weary et al. 2014; Schaper 2015). In some places, 

ancient soil horizons are buried beneath the loess, 

representing a warmer period 75,000 and 125,000 years 

ago (Weary et al. 2014). 

Ice advance and retreat rearranged the preexisting 

drainages in the midcontinent, and the Mississippi, 

Ohio, and Missouri rivers emerged as the continent’s 

major drainage systems (Fisk 1944; Saucier 1994). 

The Mississippi River valley repeatedly functioned as 

a sluiceway, funneling immense quantities of glacial 

meltwater and outwash sediments to the Gulf of 

Mexico (Saucier 1994). During glacial intervals, vast 

amounts of water were entrained as ice, resulting 

in a lower global sea level. Erosional processes 

dominated the exposed landscape, causing breaks in 

the stratigraphic record (Saucier 1994). Rivers carved 

canyons into the continental shelves. The entrenched 

valleys of the Mississippi, Arkansas, and White 

rivers formed during the most recent glaciation—the 

Wisconsinan (Fisk 1944; Waterways Experiment Station 

1951). 

Geologic processes are still changing the landscape at 

Ozark National Scenic Riverways. Since the Mesozoic 

Era, residuum (QTrr, QTtrc, and QTr), otherwise known 

as soil, clay, and rock fragments, has weathered from 

exposed (and subsurface) bedrock (Bunker et al. 

1988; Weary et al. 2014; Schaper 2015). This process 

continues to wear away the bedrock and slowly mute 

the relief. The Current River, Jacks Fork, and their 

tributaries continue to incise their channels and deposit 

mantles of alluvium (Qal) along their courses (Weary 

et al. 2014a, 2014b). Gravity, wind, and flowing water 

move this residuum, depositing it in graded layers 

(Bunker et al. 1988; Schaper 2015). Slope deposits such 

as landslide and colluvium (Qls and Qc, respectively) 

continue to accumulate at the base of slopes and cliffs. 

Muck and clayey silt are slowly filling undrained karst 

sinkholes within the Roubidoux Formation (Or) and the 

Jefferson City Dolomite (Ojc) at the park (Weary et al. 

2014).
61

Geologic Map Data

A geologic map in GIS format is the principal deliverable of the GRI program. GRI GIS data produced 

for the park follows the source maps listed here and includes components described in this chapter. 

Posters (in pocket) display the data over imagery of the park and surrounding area. A Map Unit 

Properties Table (in pocket) summarizes report content for each map unit. Complete GIS data are 

available at the GRI publications website: http://go.nps.gov/gripubs.

Geologic Maps

A geologic map is the fundamental tool for depicting 

the geology of an area. Geologic maps are twodimensional representations of the three-dimensional 

geometry of rock and sediment at or beneath the 

land surface (Evans 2016). Colors and symbols on 

geologic maps correspond to geologic map units. The 

unit symbols consist of an uppercase letter indicating 

the age (see fig. 3) and lowercase letters indicating the 

formation’s name. Other symbols depict structures such 

as faults or folds, locations of past geologic hazards 

that may be susceptible to future activity, and other 

geologic features. Anthropogenic features such as 

mines or quarries, as well as observation or collection 

locations, may be indicated on geologic maps. The 

American Geosciences Institute website, http://www.

americangeosciences.org/environment/publications/

mapping, provides more information about geologic 

maps and their uses.

Geologic maps are typically one of two types: surficial 

or bedrock. Surficial geologic maps encompass 

deposits that are unconsolidated and formed during 

the past 2.6 million years (the Quaternary Period). 

Surficial map units are differentiated by geologic 

process or depositional environment. Bedrock geologic 

maps encompass older, typically more consolidated 

sedimentary, metamorphic, and/or igneous rocks. 

Bedrock map units are differentiated based on age 

and/or rock type. GRI produced a bedrock map with 

surficial units for Ozark National Scenic Riverways.

Source Maps

The GRI team does not conduct original geologic 

mapping. The team digitizes paper maps and compiles 

and converts digital data to conform to the GRI GIS 

data model. The GRI GIS data set includes essential 

elements of the source maps such as map unit 

descriptions, a correlation chart of units, a map legend, 

map notes, cross sections, figures, and references. 

These items are included in the ozar_geology.pdf. The 

GRI team used data from Weary et al. (2014) clipped 

to the park and immediate vicinity to craft the GRI GIS 

product for the park. Seamless digital data are now 

available digitally as Weary et al. (2016). Map sheets and 

pamphlet are published as Weary et al. (2014). These 

maps provided information for the report as well.

GRI GIS Data

The GRI team standardizes map deliverables by 

using a data model. The GRI GIS data for the park 

was compiled using data model version 2.1, which is 

available is available at http://go.nps.gov/gridatamodel. 

This data model dictates GIS data structure, including 

layer architecture, feature attribution, and relationships 

within ESRI ArcGIS software. The GRI Geologic Maps 

website, http://go.nps.gov/geomaps, provides more 

information about the program’s map products.

GRI GIS data are available on the GRI publications 

website http://go.nps.gov/gripubs and through the NPS 

Integrated Resource Management Applications (IRMA) 

portal https://irma.nps.gov/App/Portal/Home. Enter 

“GRI” as the search text and select a park from the unit 

list.

The following components are part of the data set:

● A GIS readme file (ozar_gis_readme.pdf) 

that describes the GRI data formats, naming 

conventions, extraction instructions, use 

constraints, and contact information.

● Data in ESRI geodatabase GIS format;

● Layer files with feature symbology (table 4);

● Federal Geographic Data Committee (FGDC)–

compliant metadata;

● An ancillary map information document (ozar_

geology.pdf) that contains information captured 

from source maps such as map unit descriptions, 

geologic unit correlation tables, legends, crosssections, and figures;
62

● An ESRI map document (ozar_geology.mxd) that 

displays the GRI GIS data; and

● A version of the data viewable in Google Earth 

(ozar_geology.kmz; table 4).

GRI Map Posters

Three posters of the GRI GIS draped over a shaded 

relief image of the park and surrounding area are 

included with this report. Not all GIS feature classes 

are included on the posters (table 4). The posters 

also include photographs of the park’s landscape 

and historic resources. A cross section from Weary 

et al. (2014) is provided on the “Jacks Fork to Two 

Rivers” sheet. Geographic information and selected 

park features have been added to the posters. Digital 

elevation data and added geographic information are 

not included in the GRI GIS data, but are available 

online from a variety of sources. Contact GRI for 

assistance locating these data.

Map Unit Properties Table

The Map Unit Properties Table lists the geologic 

time division, symbol, and a simplified description 

for each of the geologic map units in the GRI GIS 

data. Following the structure of the report, the table 

summarizes the geologic features, processes, resource 

management issues, and history associated with each 

map unit.

Use Constraints

Graphic and written information provided in this 

report is not a substitute for site-specific investigations. 

Ground-disturbing activities should neither be 

permitted nor denied based upon the information 

provided here. Please contact GRI with any questions.

Minor inaccuracies may exist regarding the locations 

of geologic features relative to other geologic or 

geographic features on the poster. Based on the source 

map scale (1:24,000) and US National Map Accuracy 

Standards, geologic features represented in the geologic 

map data are expected to be horizontally within 12 m 

(40 ft) of their true locations.

Table 4. GRI GIS data layers for Ozark National Scenic 

Riverways (ozar_geology.mxd; ozar_geology.kmz).

Data Layer On Poster? Google Earth 

Layer?

Geologic Attitude and 

Observation Localities 

(strike and dip)

No No

Folds Yes Yes

Faults Yes Yes

Hazard Area Feature 

Boundaries (sinkholes)

Yes Yes

Hazard Area Features 

(sinkholes)

Yes Yes

Surficial Contacts Yes Yes

Surficial Units Yes Yes

Bedrock Contacts Yes Yes

Bedrock Units Yes Yes
63

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71

Additional References

These references, resources, and websites may be of use to resource managers. Refer to Appendix B 

for laws, regulations, and policies that apply to NPS geologic resources. The US Geological Survey 

compiled a glossary for geologic terms (http://geomaps.wr.usgs.gov/parks/misc/glossarya.html).

NPS Geologic Resources Division

The Geologic Resources Division (http://go.nps.gov/

geology) provides technical and policy support for 

geologic resource management issues in three emphasis 

areas:

● geologic heritage,

● active processes and hazards, and

● energy and minerals management.

Contact the division for assistance with resource 

inventories, assessments and monitoring; impact 

mitigation, restoration, and adaptation; hazards risk 

management; law, policy, and guidance; resource 

management planning; data and information 

management; and outreach and youth programs 

(Geoscientists-in-the-Parks and Mosaics in Science).

Park staff can formally request assistance via

https://irma.nps.gov/Star/.

Geology of NPS Areas

● NPS Geologic Resources Division Education 

Website: http://go.nps.gov/geoeducation

● NPS Geologic Resources Inventory:

http://go.nps.gov/gri

● NPS Geoscientists-In-the-Parks (GIP) internship 

and guest scientist program: http://go.nps.gov/gip

● NPS Views program (geology-themed modules are 

available for Geologic Time, Paleontology, Glaciers, 

Caves and Karst, Coastal Geology, Volcanoes, and a 

variety of geologic parks): http://go.nps.gov/views

NPS Resource Management Guidance and 

Documents

● Management Policies 2006 (Chapter 4: Natural 

resource management):

http://www.nps.gov/policy/mp/policies.html

● 1998 National parks omnibus management act: 

http://www.gpo.gov/fdsys/pkg/PLAW-105publ391/

pdf/PLAW-105publ391.pdf

● 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 (Young, R., and 

L. Norby, editors. 2009. Geological monitoring. 

Geological Society of America, Boulder, Colorado): 

http://go.nps.gov/geomonitoring

● NPS Technical Information Center (TIC) (Denver, 

Colorado; repository for technical documents): 

https://www.nps.gov/dsc/technicalinfocenter.htm

Climate Change Resources

● NPS Climate Change Response Program Resources: 

http://www.nps.gov/subjects/climatechange/

resources.htm

● US Global Change Research Program:

http://www.globalchange.gov/home 

● Intergovernmental Panel on Climate Change:

http://www.ipcc.ch/

Geological Surveys and Societies

● Missouri Geological Survey:

http://dnr.mo.gov/geology/

● The Geology of Missouri:

http://members.socket.net/~joschaper/geo.html

● Missouri Watershed Inventory and 

Assessment: http://mdc.mo.gov/

your-property/greener-communities/

missouri-watershed-inventory-and-assessment

● US Geological Survey: http://www.usgs.gov/

● Geological Society of America:

http://www.geosociety.org/

● American Geophysical Union: http://sites.agu.org/

● American Geosciences Institute:

http://www.americangeosciences.org/

● Association of American State Geologists:

http://www.stategeologists.org/
72

US Geological Survey Reference Tools

● Geologic glossary (simplified definitions): http://

geomaps.wr.usgs.gov/parks/misc/glossarya.html

● National geologic map database (NGMDB):

http://ngmdb.usgs.gov/ngmdb/ngmdb_home.html

● Geologic names lexicon (GEOLEX; geologic unit 

nomenclature and summary):

http://ngmdb.usgs.gov/Geolex/search

● Geographic names information system (GNIS; 

official listing of place names and geographic 

features): http://gnis.usgs.gov/

● GeoPDFs (download PDFs of any topographic map 

in the United States): http://store.usgs.gov (click on 

“Map Locator”)

● Publications warehouse (many publications 

available online): http://pubs.er.usgs.gov

● Tapestry of time and terrain (descriptions of 

physiographic provinces): http://pubs.usgs.gov/

imap/i2720/
73

2001 Scoping Meeting Participants

Name Affiliation Position

Zelda Bailey NPS National Cave and Karst Research Institute not recorded

Tim Connors NPS Geologic Resources Division Geologist, GRI maps coordinator

Sid Covington NPS Geologic Resources Division Geologist

Bill Duley Missouri Geological Survey not recorded

Victoria Grant NPS Ozark National Scenic Riverways Resource management

Deanna Greco NPS Geologic Resources Division Geologist

Bruce Heise NPS Geologic Resources Division Geologist, GRI program coordinator

Bob Higgins NPS Geologic Resources Division Geologist

Scott House NPS Ozark National Scenic Riverways Resource management

Jeff Imes USGS Water Resources Division Hydrologist

Robert Jacobsen US Geological Survey Geologist

Ron Kerbo NPS Geologic Resources Division Cave Specialist

Dennis M. Meinert DRS Soil and Water Conservation Program not recorded

Mark Middendorf Missouri Geological Survey not recorded

Bill O’Donnell NPS Ozark National Scenic Riverways not recorded

Randall Orndorff US Geological Survey Geologist

James Price NPS Ozark National Scenic Riverways Archeologist

Charles Putnam NPS Ozark National Scenic Riverways Resource management

Chris Ward NPS Ozark National Scenic Riverways not recorded

Appendix A: Scoping Participants

The following people attended the GRI scoping meeting, held on 5–6 December 2001, or the follow-up 

report writing conference call, held on 20 October 2015. Discussions during these meetings supplied a 

foundation for this GRI report. The scoping summary document is available on the GRI publications 

website: http://go.nps.gov/gripubs.

2015 Conference Call Participants

Name Affiliation Position

Joe Gilman Missouri Geological Survey State geologist, survey director

Victoria Grant NPS Ozark National Scenic Riverways Natural resource program manager

Larry Johnson NPS Ozark National Scenic Riverways Superintendent

Jason Kenworthy NPS Geologic Resources Division Geologist, GRI reports coordinator

Randall Orndorff US Geological Survey Geologist

Trista L. Thornberry-Ehrlich Colorado State University Geologist, author, and graphic designer

Dave Weary US Geological Survey Geologist

75

Appendix B: Geologic Resource Laws, Regulations, and Policies

The NPS Geologic Resources Division developed this table to summarize laws, regulations, and policies 

that specifically apply to National Park Service minerals and geologic resources. The table does not 

include laws of general application (e.g., Endangered Species Act, Clean Water Act, Wilderness Act, 

National Environmental Policy Act, or National Historic Preservation Act). The table does include the 

NPS Organic Act when it serves as the main authority for protection of a particular resource or when 

other, more specific laws are not available. Information is current as of August 2016. Contact the NPS 

Geologic Resources Division for detailed guidance.

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Paleontology

National Parks Omnibus Management 

Act of 1998, 16 USC § 5937 protects the 

confidentiality of the nature and specific 

location of paleontological resources and 

objects.

Paleontological Resources Preservation 

Act of 2009, 16 USC § 470aaa et 

seq. provides for the management and 

protection of paleontological resources on 

federal lands.

36 CFR § 2.1(a)(1)(iii) prohibits destroying, 

injuring, defacing, removing, digging or 

disturbing paleontological specimens or 

parts thereof.

Prohibition in 36 CFR § 13.35 applies 

even in Alaska parks, where the surface 

collection of other geologic resources is 

permitted.

Regulations in association with 2009 PRPA 

are being finalized (August 2016).

Section 4.8.2 requires NPS to protect 

geologic features from adverse effects of 

human activity.

Section 4.8.2.1 emphasizes Inventory and 

Monitoring, encourages scientific research, 

directs parks to maintain confidentiality of 

paleontological information, and allows 

parks to buy fossils only in accordance with 

certain criteria.

Rocks and Minerals

NPS Organic Act, 16 USC § 1 et seq.

directs the NPS to conserve all resources 

in parks (including rock and mineral 

resources), unless otherwise authorized by 

law.

36 CFR § 2.1 prohibits possessing, 

destroying, disturbing mineral resources...

in park units.

Exception: 36 CFR § 13.35 allows some 

surface collection of rocks and minerals 

in some Alaska parks (not Klondike 

Gold Rush, Sitka, Denali, Glacier Bay, 

or Katmai) by non-disturbing methods 

(e.g., no pickaxes), which can be stopped 

by superintendent if collection causes 

significant adverse effects on park 

resources and visitor enjoyment.

Section 4.8.2 requires NPS to protect 

geologic features from adverse effects of 

human activity.

Park Use of Sand and Gravel

Materials Act of 1947, 30 USC § 601

does not authorize the NPS to dispose of 

mineral materials outside of park units.

None applicable.

Section 9.1.3.3 clarifies that only the 

NPS or its agent can extract park-owned 

common variety minerals (e.g., sand and 

gravel), and:

-only for park administrative uses;

-after compliance with NEPA and other 

federal, state, and local laws, and a 

finding of non-impairment;

-after finding the use is park’s most 

reasonable alternative based on 

environment and economics;

-parks should use existing pits and create 

new pits only in accordance with parkwide borrow management plan;

-spoil areas must comply with Part 6 

standards; and

-NPS must evaluate use of external 

quarries.

Any deviation from this policy requires a 

written waiver from the Secretary, Assistant 

Secretary, or Director.
76

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Upland and Fluvial Processes

Rivers and Harbors Appropriation 

Act of 1899, 33 USC § 403 prohibits the 

construction of any obstruction on the 

waters of the United States not authorized 

by congress or approved by the USACE.

Clean Water Act 33 USC § 1342 requires 

a permit from the USACE prior to any 

discharge of dredged or fill material 

into navigable waters (waters of the US 

[including streams]). 

Executive Order 11988 requires federal 

agencies to avoid adverse impacts to 

floodplains. (see also D.O. 77-2)

Executive Order 11990 requires plans for 

potentially affected wetlands (including 

riparian wetlands). (see also D.O. 77-1)

None applicable.

Section 4.1 requires NPS to manage 

natural resources to preserve fundamental 

physical and biological processes, as well 

as individual species, features, and plant 

and animal communities; maintain all 

components and processes of naturally 

evolving park ecosystems.

Section 4.1.5 directs the NPS to reestablish natural functions and processes 

in human-disturbed components of natural 

systems in parks, unless directed otherwise 

by Congress.

Section 4.4.2.4 directs the NPS to allow 

natural recovery of landscapes disturbed by 

natural phenomena, unless manipulation of 

the landscape is necessary to protect park 

development or human safety. 

Section 4.6.4 directs the NPS to (1) 

manage for the preservation of floodplain 

values; [and] (2) minimize potentially 

hazardous conditions associated with 

flooding.

Section 4.6.6 directs the NPS to manage 

watersheds as complete hydrologic systems 

and minimize human-caused disturbance 

to the natural upland processes that deliver 

water, sediment, and woody debris to 

streams.

Section 4.8.1 directs the NPS to allow 

natural geologic processes to proceed 

unimpeded. Geologic processes...include...

erosion and sedimentation...processes. 

Section 4.8.2 directs the NPS to protect 

geologic features from the unacceptable 

impacts of human activity while allowing 

natural processes to continue.

Caves and Karst Systems

Federal Cave Resources Protection Act 

of 1988, 16 USC §§ 4301 – 4309 requires 

Interior/Agriculture to identify “significant 

caves” on Federal lands, regulate/

restrict use of those caves as appropriate, 

and include significant caves in land 

management planning efforts. Imposes 

civil and criminal penalties for harming 

a cave or cave resources. Authorizes 

Secretaries to withhold information about 

specific location of a significant cave from 

a Freedom of Information Act (FOIA) 

requester. 

National Parks Omnibus Management 

Act of 1998, 16 USC § 5937 protects the 

confidentiality of the nature and specific 

location of cave and karst resources.

36 CFR § 2.1 prohibits possessing/ 

destroying/disturbing...cave resources...in 

park units.

43 CFR Part 37 states that all NPS caves 

are “significant” and sets forth procedures 

for determining/releasing confidential 

information about specific cave locations to 

a FOIA requester.

Section 4.8.1.2 requires NPS to maintain 

karst integrity, minimize impacts.

Section 4.8.2 requires NPS to protect 

geologic features from adverse effects of 

human activity.

Section 4.8.2.2 requires NPS to protect 

caves, allow new development in or on 

caves if it will not impact cave environment, 

and to remove existing developments if 

they impair caves.

Section 6.3.11.2 explains how to manage 

caves in/adjacent to wilderness.
77

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Soils

Soil and Water Resources Conservation 

Act, 16 USC §§ 2011–2009 provides for 

the collection and analysis of soil and 

related resource data and the appraisal of 

the status, condition, and trends for these 

resources.

Farmland Protection Policy Act, 7 USC 

§ 4201 et. seq. requires NPS to identify 

and take into account the adverse effects 

of Federal programs on the preservation 

of farmland; consider alternative actions, 

and assure that such Federal programs 

are compatible with State, unit of local 

government, and private programs 

and policies to protect farmland. NPS 

actions are subject to the FPPA if they 

may irreversibly convert farmland (directly 

or indirectly) to nonagricultural use and 

are completed by a Federal agency or 

with assistance from a Federal agency. 

Applicable projects require coordination 

with the Department of Agriculture’s 

Natural Resources Conservation Service 

(NRCS).

7 CFR Parts 610 and 611 are the US 

Department of Agriculture regulations 

for the Natural Resources Conservation 

Service. Part 610 governs the NRCS 

technical assistance program, soil erosion 

predictions, and the conservation of private 

grazing land. Part 611 governs soil surveys 

and cartographic operations. The NRCS 

works with the NPS through cooperative 

arrangements.

Section 4.8.2.4 requires NPS to

-prevent unnatural erosion, removal, and 

contamination;

-conduct soil surveys;

-minimize unavoidable excavation; and

-develop/follow written prescriptions 

(instructions).
78

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Climate Change

Secretarial Order 3289 (Addressing 

the Impacts of Climate Change on 

America’s Water, Land, and Other Natural 

and Cultural Resources) (2009) requires 

DOI bureaus and offices to incorporate 

climate change impacts into long-range 

planning; and establishes DOI regional 

climate change response centers and 

Landscape Conservation Cooperatives to 

better integrate science and management 

to address climate change and other 

landscape scale issues.

Executive Order 13653 (Preparing the 

United States for the Impacts of Climate 

Change) (2013) outlines Federal agency 

responsibilities in the areas of supporting 

climate resilient investment; managing 

lands and waters for climate preparedness 

and resilience; providing information, data 

and tools for climate change preparedness 

and resilience; and planning.

Executive Order 13693 (Planning for 

Federal Sustainability in the Next Decade) 

(2015) established to maintain Federal 

leadership in sustainability and greenhouse 

gas emission reductions.

President’s Climate Action Plan (2013), 

http://www.whitehouse.gov/sites/default/

files/image/president27sclimateactionplan.

pdf 

None applicable.

Section 4.1 requires NPS to investigate 

the possibility to restore natural ecosystem 

functioning that has been disrupted by past 

or ongoing human activities. This would 

include climate change, as put forth by 

Beavers et al. (in review).

NPS Climate Change Response Strategy

(2010) describes goals and objectives to 

guide NPS actions under four integrated 

components: science, adaptation, 

mitigation, and communication.

Policy Memo 12-02 (Applying National 

Park Service Management Policies in the 

Context of Climate Change) (2012) applies 

considerations of climate change to the 

impairment prohibition and to maintaining 

“natural conditions”.

Policy Memo 14-02 (Climate Change and 

Stewardship of Cultural Resources) (2014) 

provides guidance and direction regarding 

the stewardship of cultural resources in 

relation to climate change.

Policy Memo 15-01 (Climate Change 

and Natural Hazards for Facilities) (2015) 

provides guidance on the design of facilities 

to incorporate impacts of climate change 

adaptation and natural hazards when 

making decisions in national parks.

DOI Manual Part 523,

Chapter 1 establishes policy and provides 

guidance for addressing climate change 

impacts upon the Department’s mission, 

programs, operations, and personnel.

Revisiting Leopold: Resource 

Stewardship in the National Parks

(2012) will guide US National Park natural 

and cultural resource management into 

a second century of continuous change, 

including climate change.

Climate Change Action Plan (2012) 

articulates a set of high-priority no-regrets 

actions the NPS will undertake over the 

next few years

Green Parks Plan (2013) is a long-term 

strategic plan for sustainable management 

of NPS operations.
The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and 

other information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated 

Island Communities.

NPS 614/134533, September 2016
Natural Resource Stewardship and Science 

1201 Oak Ridge Drive, Suite 150 

Fort Collins, Colorado 80525

www.nature.nps.gov

National Park Service

U.S. Department of the Interior

EXPERIENCE YOUR AMERICATM
Figure 1. Map of Ozark National Scenic Riverways. The 

Current River and Jacks Fork cut into the Ozark Plateaus in 

south-central Missouri. National Park Service map available 

at https://www.nps.gov/hfc/cfm/carto.cfm



Ozark NSR Surficial Map Unit Properties Table, Page 1 of 3 

Surficial Map Unit Properties Table: Ozark National Scenic Riverways 

Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report. 

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY PERIOD

Pleistocene and Holocene epochs

(2.6–present) 

Alluvium

(Qa)

Alluvium is deposited by water along streams, 

floodplains, riparian areas, and alluvial plains. Qa

consists of gravel, sand, silt, and clay. The larger clasts 

are slightly rounded chert, sandstone, and quartzite, 

mostly derived from the Paleozoic Era bedrock. Deposits 

of Qa range from 0 to 6 m (0 to 20 ft) in thickness. 

Qa is mapped along the channels of nearly every river, 

stream, and smaller tributaries at Ozark National Scenic 

Riverways. 

Surficial Geologic Map Units—Qa occurs along 

channels and adjacent floodplains of modern streams.

Flooding and Fluvial Geomorphology—Qa, Qt, and 

Qtl are associated with modern fluvial systems at Ozark 

National Scenic Riverways. These and slope deposits (Qls

and Qc) are integral to riparian zones and floodplains.

Erosion—stream crossings and riparian areas are among 

the most disturbed ecosystems in the park. Increased 

erosion contributes to increased river meandering, 

increased suspended sediment load in park streams, and 

formation of gravel bars as the channel migrates.

River Valley Evolution and Ice Age Glaciation—Qa is 

among the youngest geologic map units occurring on the 

landscape at Ozark National Scenic Riverways. These units 

reflect the ongoing processes of weathering and erosion 

within the Ozark Mountains, which create sediments for 

river transportation and deposition. Rivers transport 

sediments downslope toward the Coastal Plain.

QUATERNARY PERIOD

Pleistocene and Holocene 

epochs

(2.6–present) 

Muck and clayey silt

(Qm)

Qm is fine-grained silt, reworked loess (Ql), clay, and 

organic-rich muck of unknown thickness. Qm is 

intermittently water laden. 

Qm occurs in mapped karst sinkholes within Or and Ojc

in the Blue Spring to Chalk Bluff area along the Jacks 

Fork River. Some of these sinks, such as Tupelo Pond 

and Cupola Pond, support unique floral and possibly 

faunal communities.

Cave and Karst Features and Processes—Qm

accumulates in deep sinkholes.

Caves and Associated Landscape Management—Qm

collects in sinkholes that are plugged and intermittently 

flooded. 

River Valley Evolution and Ice Age Glaciation—Qm is 

slowly filling sinkholes and may contain fossil pollen 

records of past climate conditions. 

QUATERNARY PERIOD

Pleistocene and Holocene 

epochs

(2.6–present) 

Landslide deposits

(Qls)

Qls consists of a jumbled mix of dolomite, chert, 

sandstone, and quartzite clasts in a finer-grained matrix 

of clay and silt. Deposits of Qls range from 6 to 30 m 

(30 to 100 ft) thick. 

Qls is only mapped in the Van Buren North quadrangle 

near Waymeyer, but similar deposits occur in other areas 

of steep topography.

Bedrock Weathering and Residuum Formation—Qls

accumulates as large landslides and large-scale slumps 

with hummocky surface topography. Qls occurs in areas 

of steep slopes.

Flooding and Fluvial Geomorphology—Qa, Qt, and 

Qtl are associated with modern fluvial systems at Ozark 

National Scenic Riverways. These and slope deposits (Qls

and Qc) are integral to riparian zones and floodplains.

Slope Movement Hazards and Risks—Qls indicates 

areas of past slope movement. Future movement is also 

possible, creating hazards for infrastructure or recreation. 

River Valley Evolution and Ice Age Glaciation—

formation of Qc and Qls was likely accelerated during the 

colder, periglacial conditions of the Pleistocene glaciations.

QUATERNARY PERIOD

Pleistocene and Holocene 

epochs

(2.6–present) 

Colluvium

(Qc)

Colluvium consists of clast-supported, rather angular to 

slightly rounded cobbles and boulders that collect at the 

bases of slopes. Qc contains boulders, cobbles, and 

pebbles of sandstone from weathering QTrr (derived 

from Or) in deposits about 1 m (3 ft) thick. 

Qc is only mapped in the Powder Mill Ferry quadrangle 

near Two Rivers, but occurs in other areas of steep 

topography.

Bedrock Weathering and Residuum Formation—Qc

accumulates as gravity-creep deposits on steep slopes in 

the upper part of Og below QTrr.

Flooding and Fluvial Geomorphology—Qa, Qt, and 

Qtl are associated with modern fluvial systems at Ozark 

National Scenic Riverways. These and slope deposits (Qls

and Qc) are integral to riparian zones and floodplains.

Slope Movement Hazards and Risks—Qc indicates 

areas of past slope movement. Future movement is also 

possible, creating hazards for infrastructure or recreation.

River Valley Evolution and Ice Age Glaciation—

formation of Qc and Qls was likely accelerated during the 

colder, periglacial conditions of the Pleistocene glaciations. 
Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report.

Ozark NSR Surficial Map Unit Properties Table, Page 2 of 3

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY PERIOD

Pleistocene and Holocene 

epochs

(2.6–present)

Terrace deposits

(Qt)

Terrace deposits typically contain coarser sand and 

gravel perched above the modern floodplain; terraces 

represent former stream levels. Qt consists of cobble- to 

sand-size, slightly rounded chert, sandstone, and 

quartzite clasts within a finer-grained matrix of sand, 

silt, and clay. Some of the matrix material may be 

reworked Ql. Thickness of Qt is typically more than 3 m 

(10 ft) and tends to be thicker along larger streams. 

Qt is mapped along most rivers, streams, and tributaries 

in Ozark National Scenic Riverways flanking deposits of 

Qa. 

Surficial Geologic Map Units—Qt accumulates on 

relatively flat areas along modern stream valley floors and 

walls, but above the normal flood range, 2 to 3 m (6 to 10 

ft) above stream level. 

Flooding and Fluvial Geomorphology—Qa, Qt, and 

Qtl are associated with modern fluvial systems at Ozark 

National Scenic Riverways. These and slope deposits (Qls

and Qc) are integral to riparian zones and floodplains. 

Erosion—Stream crossings and riparian areas are among 

the most disturbed ecosystems in the park. Increased 

erosion contributes to increased river meandering, 

increased suspended sediment load in park streams, and 

gravel bars.

River Valley Evolution and Ice Age Glaciation—Qt

records former river levels along the Current and Jacks 

Fork rivers during the Holocene and possibly the 

Pleistocene epochs.

QUATERNARY PERIOD

Pleistocene and Holocene 

epochs

(2.6–present)

Loess-covered terrace 

deposits

(Qtl)

Qtl is mostly silt with some sand and clay in windblown 

deposits as much as 0.3 m (1 ft) thick atop welldeveloped soil horizons or clay, silt, sand, and minor 

pebbles. 

Qtl is mapped in the Stegall Mountain and Van Buren 

South quadrangles. 

Surficial Geologic Map Units—Qtl occurs on slopes 

above the valleys of various large streams and within a few 

large sinkholes. 

Periglacial Features—loess collected as winds swept 

across the landscape in colder climates associated with 

Pleistocene glaciations (“ice ages”). 

Flooding and Fluvial Geomorphology—Qa, Qt, and 

Qtl are associated with modern fluvial systems at Ozark 

National Scenic Riverways. These and slope deposits (Qls

and Qc) are integral to riparian zones and floodplains. 

Erosion—Stream crossings and riparian areas are among 

the most disturbed ecosystems in the park. Increased 

erosion contributes to increased river meandering, 

increased suspended sediment load in park streams, and 

gravel bars.

River Valley Evolution and Ice Age Glaciation—buried 

beneath the loess is a well-developed soil horizon that is 

probably recording the Sangamon Geosol. Qtl records 

former river levels along the Current and Jacks Fork rivers. 

QUATERNARY PERIOD

Pleistocene and Holocene 

epochs

(2.6–present)

Loess

(Ql)

Ql consists of finely winnowed silt in deposits as much 

as 1 m (3 ft) thick. Ql is commonly mixed with residuum 

from plant activity and other bioturbation (i.e. 

burrowing). 

Ql is mapped in the Stegall Mountain quadrangle, but 

occurs as thin veneers in other areas including 

discontinuous patches on hills and ridges such as Thorny 

Mountain.

Periglacial Features—loess collected as winds swept 

across the landscape in colder climates associated with 

Pleistocene glaciations (“ice ages”).

None documented.

River Valley Evolution and Ice Age Glaciation—buried 

beneath the loess is a well-developed soil horizon that is 

probably recording the Sangamon Geosol.

QUATERNARY PERIOD

and TERTIARY

(66.0–present)

Residuum derived 

from Roubidoux 

Formation

(QTrr)

QTrr is red and reddish-orange sandy clay with 

abundant angular boulders of sandstone and chert. The 

sandstone boulders are fine- to coarse-grained, poorly 

sorted, and contains some ripple marks. The chert 

component is gray with banded, sandy, oolitic or 

porcelaneous (microcrystalline) varieties. Boulders can 

reach 2 m (6 ft) in diameter. QTrr is up to 12 m (40 ft) 

thick. 

QTrr is a widespread unit, but not mapped in all 

quadrangles; it occurs on hilltops where Or has been 

deeply weathered atop mapped areas of Og. 

Cave and Karst Features and Processes—QTrr fills or 

covers sinkholes.

Surficial Geologic Map Units—QTrr is a residual unit, 

the result of intense weathering of bedrock (Or).

Sedimentary Rock Features—clasts in QTrr have 

symmetrical and asymmetrical ripple marks indicating 

deposition in fluvial or nearshore marine environments. 

Oolites in some chert boulders indicate deposition in 

shoreline environments.

Faults and Fractures—QTrr fills or covers faults.

Folds—QTrr fills or covers folds.

None documented.

River Valley Evolution and Ice Age Glaciation—

formation of QTrr was likely accelerated during the colder, 

periglacial conditions of the Pleistocene glaciations.
Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report.

Ozark NSR Surficial Map Unit Properties Table, Page 3 of 3

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY PERIOD and TERTIARY

(66.0–present)

Residual and colluvial 

material on terracelike landforms

(QTtrc)

QTtrc consists of silt, clay, sand, and gravel.

Unit is only mapped in the Stegall Mountain quadrangle 

in terrace-like landforms adjacent to knobs of 

Mesoproterozoic volcanic rocks. QTtrc occurs in the 

Rocky Falls and Roberts Field areas upstream from 

Logyard.

Cave and Karst Features and Processes—QTtrc fills or 

covers sinkholes.

Surficial Geologic Map Units—QTtrc occurs on slopes 

above the valleys of various large streams and within a few 

large sinkholes. It is gradational, in some areas, with Qt

and Qtl. 

Bedrock Weathering and Residuum Formation—

QTtrc is in part residual and colluvial in nature as it 

accumulates on steep slopes.

Periglacial Features—QTtrc commonly has a thin mantle 

of loess that collected as winds swept across the landscape 

in colder climates associated with Pleistocene glaciations 

(“ice ages”).

Faults and Fractures—QTtrc fills or covers faults.

Folds—QTtrc fills or covers folds.

Slope Movement Hazards and Risks—QTtrc indicates 

areas of past slope movement. Future movement is also 

possible, creating hazards for infrastructure or recreation.

River Valley Evolution and Ice Age Glaciation—

formation of QTtrc was likely accelerated during the 

colder, periglacial conditions of the Pleistocene glaciations.

QUATERNARY PERIOD and 

TERTIARY

(66.0–present)

Upland gravel deposit

(QTg)

QTg contains gravel deposits less than 3 m (10 ft) thick 

perched as high as 90 m (300 ft) above modern stream 

floodplains. The deposits are mostly rounded clasts of 

chert, sandstone, and quartzite with a silty sand matrix. 

Unit is mapped only on the Van Buren North 

quadrangle. 

Paleontological Resources—QTg contains clasts of 

fossiliferous Mississippian chert. Mississippian rocks are not 

exposed within Ozark National Scenic Riverways.

Paleontological Resource Inventory, Monitoring, and 

Protection—fossil theft is a concern of park managers. A 

field-based paleontological resource survey can provide 

detailed, site-specific descriptions and recommendations.

River Valley Evolution and Ice Age Glaciation—QTg

records former river levels and has remnants of geologic 

bedrock units no longer present on the park landscape.

QUATERNARY PERIOD,

TERTIARY, and MESOZOIC ERA?

(252–present)

Peck Ranch unit

(QTr)

QTr is brown, red, and reddish-orange sandy clay with 

abundant angular blocks, cobbles, and pebbles of 

sandstone with various chert varieties similar to QTrr. 

QTr is at least 60 m (200 ft) thick. 

Unit is mapped only in the Stegall Mountain quadrangle. 

It occurs outside park boundaries near Rocky Falls. 

Cave and Karst Features and Processes—QTr fills or 

covers sinkholes.

Surficial Geologic Map Units—QTr is a residual unit, the 

result of intense weathering of one or more bedrock units: 

Or and Ce. QTr preserves a crude stratigraphic sequence 

left over from the original bedrock. 

Faults and Fractures—QTr fills or covers faults.

Folds—QTr fills or covers folds.

None documented.

River Valley Evolution and Ice Age Glaciation—

formation of QTr was likely accelerated during the colder, 

periglacial conditions of the Pleistocene glaciations.
Ozark NSR Bedrock Map Unit Properties Table, Page 1 of 4 

Bedrock Map Unit Properties Table: Ozark National Scenic Riverways 

Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report. 

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

LOWER ORDOVICIAN

(485–470)

Jefferson City 

Dolomite 

(Ojc)

Ojc is light brown, medium- to fine-grained, argillaceous 

dolomite with lesser amounts of quartz sandstone lenses 

and chert beds and nodules. Bedding is thin to thick and 

weathered outcrops appear powdery-pale yellow. A 

conspicuous, ledge-forming, brown, medium-grained, 

siliceous, pitted-weathering dolomite occurs between 8 

and 12 m (25 and 40 ft) of the base of Ojc—the 

“Quarry Ledge”. Ojc is on average 61 m (200 ft) thick 

and only occurs in the park in upland areas along the 

upper Jacks Fork. 

Cave and Karst Features and Processes—Ojc contains 

thick carbonate layers that are susceptible to karst 

dissolution. Karst sinkholes are mapped in Ojc and some 

contain deposits of Qm. 

Bedrock Weathering and Residuum Formation—

weathered Ojc, that collects as the bases of exposures, 

tends to be more silty and less sandy than those from Or

with residual sandstone and orthoquartzite that are less 

tabular in shape than those from Or. These characteristics 

help to differentiate Ojc and Or when exposures are 

limited. 

Paleontological Resources—sparsely fossiliferous 

containing trilobites and conodonts. 

Caves and Associated Landscape Management—karst 

management issues include sinkhole flooding and collapse, 

cave breakdown or roof collapse, slippery surfaces, 

precipitous drops, drowning, radon, vandalism and 

dumping, and white-nose syndrome. Because white-nose 

syndrome was discovered in the park in 2010, all park 

caves are closed to entry except for tours of Round Spring 

Cavern. Ojc and Or have the highest concentration of 

sinkholes in this part of Missouri. Most are closed-throat 

sinkholes; however, collapses have occurred historically. 

Karst management issues include sinkhole flooding and 

collapse, cave breakdown, slippery surfaces, precipitous 

drops, drowning, radon, vandalism and dumping, and 

white-nose syndrome. 

Ozarks Aquifer and Springs Protection—Ojc is part of 

the Ozarks aquifer.

Paleontological Resource Inventory, Monitoring, and 

Protection—fossil theft is a concern of park managers. A 

field-based paleontological resource survey can provide 

detailed, site-specific descriptions and recommendations.

Marine Inundation, Deposition, and Erosion, 

Assembling Pangaea—Ojc is the youngest Paleozoic unit 

exposed in the park area. It was deposited in a shallow 

marine basin. Sea levels fluctuated, increasing or 

decreasing the amount of terrestrial (noncarbonate) 

sediment. 

LOWER ORDOVICIAN

(485–470)

Roubidoux Formation

(Or)

Or consists of white to pale orange, fine- to coarsegrained, thin- to thick-bedded, poorly sorted sandstone 

interbedded with medium gray, very fine- to coarsegrained, thin- to medium-bedded dolomite. Thin beds, 

lenses and nodules of white to medium gray chert are 

common. Orthoquartzite and sandy dolomite are also 

interlayered with the dominant sandstone and dolomite. 

Or ranges up to 76 m (250 ft) thick. 

Cave and Karst Features and Processes—karst 

sinkholes are mapped in Or and some contain deposits of 

Qm. Sandstone layers within Or control the location of 

cave formation.

Sedimentary Rock Features—sandstones in Or have 

symmetrical and asymmetrical ripple marks and cross beds 

indicating deposition in fluvial or nearshore environments. 

Oolites in some chert indicate deposition in shoreline 

environments.

Paleontological Resources—occasional molds and 

impressions of the gastropod Lecanospira, brachiopods, 

cephalopods, conodonts, and crinoid fragments. Some 

chert contains stromatolites. 

Caves and Associated Landscape Management—karst 

management issues include sinkhole flooding and collapse, 

cave breakdown or roof collapse, slippery surfaces, 

precipitous drops, drowning, radon, vandalism and 

dumping, and white-nose syndrome. Because white-nose 

syndrome was discovered in the park in 2010, all park 

caves are closed to entry except for tours of Round Spring 

Cavern. Ojc and Or have the highest concentration of 

sinkholes in this part of Missouri. Most are closed-throat 

sinkholes; however, collapses have occurred historically. 

Ozarks Aquifer and Springs Protection—Or is a major 

part of the Ozarks aquifer. 

Paleontological Resource Inventory, Monitoring, and 

Protection—fossil theft is a concern of park managers. A 

field-based paleontological resource survey can provide

detailed, site-specific descriptions and recommendations.

Marine Inundation, Deposition, and Erosion, 

Assembling Pangaea—Or was deposited in a shallow 

marine basin. Sea levels fluctuated, increasing or 

decreasing the amount of sandy sediment. 
Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report.

Ozark NSR Bedrock Map Unit Properties Table, Page 2 of 4

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

LOWER ORDOVICIAN

(485–470)

Gasconade Dolomite

(Og)

Og is divisible into three informal units: (1) an upper 

unit of light gray, medium- to coarse-grained, thickbedded, vuggy (contains cavities) dolomite; (2) a middle 

unit of mostly light gray, fine- to coarse-grained, 

medium- to thick-bedded dolomite grading downward 

into more chert-rich dolomite, and lower into light gray 

to yellowish gray, fine- to medium-grained, thin- to 

medium-bedded dolomite; and (3) a light gray to white 

sandstone, sandy dolomite, or orthoquartzite 

interbedded with light gray to tan, fine-grained, thinbedded dolomite called the Gunter Sandstone Member. 

The lowermost, third unit ranges in thickness from 3 to 

8 m (10 to 25 ft). The overall thickness of Og is between 

45 and 235 m (148 and 770 ft). 

Cave and Karst Features and Processes—Og contains 

thick carbonate layers susceptible to karst dissolution. Og

is the major cave-forming unit in the park with the 

majority of caves in the upper reaches of the unit forming 

below the contact with Ojc. Karst sinkholes are mapped in 

Og. Sandstone layers at the base of Og are confining units 

and control the location of cave formation.

Sedimentary Rock Features—Og chert is porcelaneous, 

oolitic, porous with druse, and stromatolitic. 

Paleontological Resources—white Cryptozoon chert 

layers, as well as mollusks (including planispiral 

gastropods), conodonts, and cephalopods. 

Caves and Associated Landscape Management—karst 

management issues include sinkhole flooding and collapse, 

cave breakdown or roof collapse, slippery surfaces, 

precipitous drops, drowning, radon, vandalism and 

dumping, and white-nose syndrome. Because white-nose 

syndrome was discovered in the park in 2010, all park 

caves are closed to entry except for tours of Round Spring 

Cavern. Og hosts the majority of park caves.

Ozarks Aquifer and Springs Protection—Og is part of 

the Ozarks aquifer.

Paleontological Resource Inventory, Monitoring, and 

Protection—Og contains fossil resources that may be 

subject to theft or degradation. Fossil theft is a concern of 

park managers. A field-based paleontological resource 

survey can provide detailed, site-specific descriptions and 

recommendations.

Marine Inundation, Deposition, and Erosion, 

Assembling Pangaea—Og is the youngest unit in 

contact with the Mesoproterozoic igneous rocks. There is 

an unconformable contact with underlying Ce indicating a 

period of erosion or nondeposition. 

UPPER CAMBRIAN

(501–485)

Eminence Dolomite

(Ce)

Dolomite, sandstone, and chert compose Ce. The 

dolomite is light gray, medium to coarse grained, 

massive to thick bedded, and contains stromatolites. 

Weathered outcrops appear bluish gray and medium 

gray with pitted surfaces and the unit occurs as small 

knobs or pinnacles. Chert stringers and nodules are 

common and some quartz sandstone and sandy 

dolomite interbeds also occur where the unit is thicker. 

Thickness of Ce ranges from 23 to 280 m (80 to 919 ft).

Cave and Karst Features and Processes—Ce contains 

thick carbonate layers that are susceptible to karst 

dissolution. Ce is one of the main cave-forming units in 

the park with the majority of caves in the upper reaches of 

the unit forming below the contact with Og. Knobs and 

pinnacles are left after the rest of the unit dissolves away. 

Karst sinkholes are mapped in Ce. Sandstone layers within 

Ce are confining units and control the location of cave 

formation.

Paleontological Resources—fossil algae (stromatolites) 

in the dolomite as well as gastropods, other mollusks, and 

trilobites.

Caves and Associated Landscape Management—karst 

management issues include sinkhole flooding and collapse, 

cave breakdown or roof collapse, slippery surfaces, 

precipitous drops, drowning, radon, vandalism and 

dumping, and white-nose syndrome. Because white-nose 

syndrome was discovered in the park in 2010, all park 

caves are closed to entry except for tours of Round Spring 

Cavern. Extensive caves occur in Ce.

Ozarks Aquifer and Springs Protection—Ce is part of 

the Ozarks aquifer.

Paleontological Resource Inventory, Monitoring, and 

Protection—Ce contains fossil resources that may be 

subject to theft or degradation. Fossil theft is a concern of 

park managers. A field-based paleontological resource 

survey can provide detailed, site-specific descriptions and 

recommendations.

Marine Inundation, Deposition, and Erosion, 

Assembling Pangaea—Ce was deposited in a shallow 

marine basin. Layers of Ce are thinner near knobs of 

Mesoproterozoic rocks suggesting the indicating their 

presence as islands during deposition in a longstanding 

shallow marine basin. 

UPPER CAMBRIAN

(501–485)

Potosi Dolomite

(Cp)

Cp is light brown and gray, fine- to medium-grained, 

massive- to thick-bedded dolomite. Vugs or cavities are 

filled with quartz druse. White to light gray chert 

nodules and stringers are common. Cp ranges in 

thickness from 15 to 175 m (50 to 575 ft). 

Cave and Karst Features and Processes—Cp contains 

thick carbonate layers that are susceptible to karst 

dissolution. Minor caves and other solutional features are 

concentrated at or near the contact between Cp and Ce. 

Karst sinkholes are mapped in Cp.

Sedimentary Rock Features—Cp, when freshly broken, 

has a fetid odor. Vugs contain in botryoidal masses of 

chalcedony and small quartz crystals coating the surface.

Paleontological Resources—stromatolites, gastropods, 

other mollusks, and trilobites. 

Caves and Associated Landscape Management—karst 

management issues include sinkhole flooding and collapse, 

cave breakdown or roof collapse, slippery surfaces, 

precipitous drops, drowning, radon, vandalism and 

dumping, and white-nose syndrome. Because white-nose 

syndrome was discovered in the park in 2010, all park 

caves are closed to entry except for tours of Round Spring 

Cavern. 

Ozarks Aquifer and Springs Protection—Cp is part of 

the Ozarks aquifer.

Paleontological Resource Inventory, Monitoring, and 

Protection—fossil theft is a concern of park managers. A 

field-based paleontological resource survey can provide 

detailed, site-specific descriptions and recommendations.

Marine Inundation, Deposition, and Erosion, 

Assembling Pangaea—Cp is the oldest sedimentary unit 

in the Ozark National Scenic Riverways map area. Like the 

other Paleozoic rocks, it was deposited in a shallow marine 

basin. 

Rocks younger than Mesoproterozoic and older than Upper Cambrian are not mapped within Ozark National Scenic Riverways. This represents a gap of nearly one billion years.
Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report.

Ozark NSR Bedrock Map Unit Properties Table, Page 3 of 4

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

MESOPROTEROZOIC ERA

(1600–1000)

Big Spring quad 

granite

(Yg)

“Granite” denotes a specific intrusive—cooled beneath 

the surface—igneous rock composition characterized by 

relatively high silica contents, rich in quartz (10 to 50%) 

and with more alkali feldspars than granodiorite. Other 

minerals include plagioclase, muscovite, biotite and/or 

hornblende. Yg is red, medium-grained with clots of 

altered, dark amphibole minerals with quartz and alkali 

feldspar. Accessory minerals include fluorite, zircon, and 

magnetite. Yg weathers to produce secondary clay, 

sericite and epidote. 

Yg is mapped in the Big Spring, Van Buren South, 

Winona, and Round Spring quadrangles. 

Radiometric Ages—samples of Yg have been dated 

using U-Pb at: 1,461±5.5, 1,473±15, 1,480±42, and 

1,473±15 million years ago. 

Abandoned Mineral Lands—Yg was quarried during the 

CCC-era developments. 

External Mineral Development—“Y” units are 

associated with economic minerals that may be targets of 

exploration.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Yg formed as magma domes that rose and 

cooled between volcanic eruptions associated with the 

Eminence caldera. There is an unconformity between Yg

and overlying Cp indicating more than 500 million years or 

erosion and/or nondeposition.

MESOPROTEROZOIC ERA

(1600–1000)

Rhyolite of Russell 

Mountain

(Yrm)

Rhyolite is an extrusive—erupted from a volcano—

igneous rock with a mineralogical composition similar to 

granite. Textures include visible crystals in a glass to 

cryptocrystalline groundmass. If the alkali feldspar 

component decreases, rhyolite grades into rhyodacite. 

Yrm is a rhyolitic ash-flow tuff. Tuff is the consolidated 

or cemented form of volcanic ash and lapilli (larger 

volcanic ejecta). Yrm contains abundant crystals of pink 

alkali feldspar, magnetite, and hematite and is at least 

1,000 m (3,000 ft) thick. Yrm may be correlative with 

Yltm. 

Yrm is mapped in the Stegall Mountain and Powder Mill 

Ferry quadrangles

Volcanic Rocks and the Eminence Caldera—Yrm is 

densely welded with flow-banding structures present in 

places. Yrm was erupted as multiple flows of simple and 

compound cooling units. Rotation of Yrm, reflected in the 

steep inclination of the banding, occurred during caldera 

collapse. 

External Mineral Development—“Y” units are 

associated with economic minerals that may be targets of 

exploration.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Yrm formed during the rift margin 

volcanism associated with the Eminence caldera. Yrm and 

Yltm may have been part of the same eruptive event. 

MESOPROTEROZOIC ERA

(1600–1000)

Volcaniclastic 

conglomerate, 

breccia, and 

sandstone

(Yvc)

A breccia is a coarse-grained rock composed of angular, 

broken rock fragments held together in a fine-grained 

matrix. In some areas of Yvc, the fragments are 

subrounded composing a conglomerate interbedded 

with coarse- to medium-grained sandstone and strongly 

silicified breccia. The 8- to 13-cm (3- to 5-in) diameter 

cobbles are derived from Ysc, Ycu, and other volcanic 

rocks. The weathered, greenish, finer-grained matrix is 

also volcaniclastic material. 

Yvc only occurs on the southern side of Coot Mountain, 

and in the Eminence and Powder Mill Ferry quadrangles. 

Volcanic Rocks and the Eminence Caldera—Yvc

contains fragments of Ysc and Ycu indicating these units 

were already in place when further eruptions exploded, 

incorporating the fragments into a new unit.

None documented.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Yvc was erupted and emplaced after Ysc

and Ycu.

MESOPROTEROZOIC 

ERA

(1600–1000)

Rhyolite of Sutton 

Creek

(Ysc)

Ysc consists of alkali rhyolite to rhyolite with 

phenocrysts (large crystals) on pink feldspar in a dark 

pink, finer-grained matrix. Ysc also contains 

conspicuous aggregates of small pink feldspar crystals in 

an apple-green matrix that alter yellowish white. 

Ysc is mapped in the Eminence quadrangle and is 

exposed along the northwest bank of the Current River 

near Tip Top Mountain and near the confluence with 

the Jacks Fork River. 

Volcanic Rocks and the Eminence Caldera—Ysc

contains aggregates of crystals that may be xenoliths, or 

fragments derived from another rock that were 

incorporated into the lava of Ysc. Fragments of Ysc are 

part of Yvc. Ysc displays some flow banding, but is 

commonly not layered. 

External Mineral Development—“Y” units are 

associated with economic minerals that may be targets of 

exploration.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Ysc formed during the rift margin 

volcanism associated with the Eminence caldera.
Gray-shaded map units are not mapped within Ozark National Scenic Riverways. Bold text refers to sections in report.

Ozark NSR Bedrock Map Unit Properties Table, Page 4 of 4

Age

(millions of 

years ago)

Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

MESOPROTEROZOIC ERA

(1600–1000)

Rhyolite of Shut-In 

Mountain

(Ysi)

Ysi is dense rhyolite to alkali trachyte lava. With alkali 

feldspar and minor mafic minerals (biotite, amphibole, 

or pyroxene), trachyte is similar to rhyolite in 

composition, but with less quartz. Ysi is relatively crystal 

rich with white to pink alkali feldspar and some quartz 

crystals. Accessory minerals include fluorite, magnetite, 

and hematite, all in a light pink to maroon red matrix. 

Ysi is at least 275 m (900 ft) thick. 

Ysi is mapped in the Stegall Mountain quadrangle. 

Rocky Falls flows Ysi.

Volcanic Rocks and the Eminence Caldera—Ysi

displays some flow banding, but is commonly not layered. 

Ysi has some small zones of hydrothermal brecciation and 

vesicles (original bubbles or cavities) filled with quartz and 

feldspar. Ysi possibly formed as coalesced lava flows and 

domes. The hydrothermal brecciation likely marks vent 

sites. 

Radiometric Ages—a sample of Ysi was been dated 

using U-Pb at 1,470±2.7 million years ago.

External Mineral Development—“Y” units are 

associated with economic minerals that may be targets of 

exploration.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Ysi was deposited atop Ymm and Yltm in 

the caldera after it collapsed and its flanks rotated. 

MESOPROTEROZOIC 

ERA

(1600–1000)

Rhyolite of Stegall 

Mountain

(Ysm)

Ysm is similar in composition to Ysi as dense rhyolite to 

alkali trachyte lava. The only difference is a lower 

quartz-phenocryst content (0.5 to 2% versus 3 to 5%). 

Ysm is at least 61 m (200 ft) thick.

Ysm is mapped in the Stegall Mountain quadrangle. 

Volcanic Rocks and the Eminence Caldera—Ysm is 

genetically related to Ysi. None documented.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Ysm is part of the Mesoproterozoic suite of 

volcanic rocks at the park. It likely erupted after the 

collapse of the Eminence caldera.

MESOPROTEROZOIC 

ERA

(1600–1000)

Tuff of Mule 

Mountain

(Ymm)

Ymm is air-fall tuff with dense, aphanitic (glassy to 

microcrystalline), finely laminated appearance. Thickness 

of Ymm ranges from 4.5 to 30 m (15 to 100 ft). 

Ymm is mapped in the Stegall Mountain quadrangle.

Volcanic Rocks and the Eminence Caldera—Ymm has 

rare angular quartz phenocrysts. Ymm has abundant 

accretionary lapilli or pellets of ash that formed by rainfall 

through a downwind ash cloud or by accretion from a 

moisture-laden eruption.

None documented.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—the contact between Ymm and overlying 

Ysm and Ysi is conformable indicating a long period of 

volcanic eruptions. The underlying contact with Yltm is 

complex and irregular. Ymm was deposited in the caldera 

after it collapsed. 

MESOPROTEROZOIC 

ERA

(1600–1000)

Tuff of Little Thorny

Mountain

(Yltm)

Yltm is dense, dark maroon to purple, moderately 

crystal-rich, and quartz-poor, ash-flow tuff. Phenocrysts 

are almost entirely alkali feldspar with some magnetite, 

hematite, and fluorite. Yltm is at least 1,000 m (3,000 

ft) thick. 

Yltm is mapped in the Stegall Mountain quadrangle.

Volcanic Rocks and the Eminence Caldera—Yltm

shows fiamme (dark, glassy lenses formed by the collapse 

of pumice fragments) and eutaxitic (banded or layered) 

textures with some flow banding. Rotation of Yltm, 

reflected in the steep inclination of the banding, occurred 

during caldera collapse.

None documented.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—an unconformity occurs between Yltm and 

overlying Ymm indicating a period of erosion and/or 

nondeposition between volcanic episodes. Yltm was 

synvolcanic. Yltm formed during the rift margin volcanism 

associated with the Eminence caldera. After deposition, it 

rotated when the caldera collapsed.

MESOPROTEROZOIC 

ERA

(1600–1000)

Upper Coot Mountain 

unit

(Ycu)

Ycu is similar in composition to Ysm and Ysi as dense 

rhyolite to alkali rhyolite to alkali trachyte, but is a 

densely welded ash-flow tuff. Sparse pink feldspar and 

rare quartz phenocrysts with some magnetite and 

fluorite. 

Ycu is mapped at the summit and northeast side of 

Coot Mountain, at Jerktail Mountain, and Wildcat 

Mountain. 

Volcanic Rocks and the Eminence Caldera—Ycu shows 

eutaxitic (banded or layered) textures with flow layering. 

Vapor-phase feldspar and quartz mineralization is common 

in pumice fragments. 

External Mineral Development—“Y” units are 

associated with economic minerals that may be targets of 

exploration.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Ycu formed during the rift margin 

volcanism associated with the Eminence caldera. After 

deposition, it rotated when the caldera collapsed.

MESOPROTEROZOIC 

ERA

(1600–1000)

Lower Coot Mountain 

unit

(Ycl)

Ycl is similar in composition to Ycu as alkali rhyolite to 

alkali trachyte to trachyte and rhyolite ash-flow tuff, airfall tuff, and perhaps lava. Ycl appears dark maroon 

with pink feldspar phenocrysts and some magnetite. Ycl

has some pumice-rich, poorly welded layers. 

Ycl is exposed and mapped along the southwestern side 

of Coot Mountain, at Jerktail Mountain, and an 

unnamed knob along Missouri Route 106 east of 

Eminence. 

Volcanic Rock Features and the Eminence Caldera—

Ycu has some flow-layering, but most of the original 

volcanic depositional (fall and flow) features have been 

destroyed or altered beyond recognition. Secondary quartz 

mineralization (veins and cavities) is common. 

External Mineral Development—“Y” units are 

associated with economic minerals that may be targets of 

exploration.

Building the Ozark Dome, Volcanism, Deformation, 

and Erosion—Ycl formed during the rift margin 

volcanism associated with the Eminence caldera. After 

deposition, it rotated when the caldera collapsed.