U.S. Department of the Interior

U.S. Geological Survey

Data Series 1017

Digital Geologic Map Data for the Ozark National Scenic 

Riverways and Adjacent Areas Along the Current River 

and Jacks Fork, Missouri

Digital Geologic Map Data for the Ozark 

National Scenic Riverways and Adjacent 

Areas Along the Current River and Jacks 

Fork, Missouri

By David J. Weary, Randall C. Orndorff, Richard W. Harrison, and 

Robert E. Weems

Data Series 1017

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Suggested citation:

Weary, D.J., Orndorff, R.C., Harrison, R.W., and Weems, R.E., 2016, Digital geologic map data for the Ozark National 

Scenic Riverways and adjacent areas along the Current River and Jacks Fork, Missouri: U.S. Geological Survey Data 

Series 1017, 14 p., http://dx.doi.org/10.3133/ds1017.

ISSN 2327-638X (online)
iii

Contents

Abstract...........................................................................................................................................................1

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

Purpose...................................................................................................................................................1

Scope of the Data ........................................................................................................................1

Original Data Sources.................................................................................................................1

Geologic Description.....................................................................................................................................2

Description of Map Units..............................................................................................................................6

Surficial Units ........................................................................................................................................6

Paleozoic Bedrock Units .....................................................................................................................7

Mesoproterozoic Intrusive Rocks......................................................................................................8

Mesoproterozoic Volcanic Rocks ......................................................................................................8

Upper Sequence of Mesoproterozoic Volcanic Rocks .........................................................8

Lower Sequence of Mesoproterozoic Volcanic Rocks .......................................................10

Structural Geology.......................................................................................................................................10

Paleontology.................................................................................................................................................11

Geologic Resources ....................................................................................................................................11

References Cited..........................................................................................................................................12

Figures

1. Simplified geologic map of the Ozark National Scenic Riverways area 

based on the 1:24,000-scale GIS data provided in this report...............................................3

2. Correlation of map units ..............................................................................................................4

3. Idealized stratigraphic column for the Ozark National Scenic Riverways 

area showing lithostratigraphic units which include outcropping Paleozoic 

formations and Proterozoic rocks..............................................................................................5

Table

1. List of quadrangle maps completed in the Ozark National Scenic Riverways 

and vicinity by the U.S. Geological Survey and the Missouri Geological Survey 

and used as sources for this compilation.................................................................................2
iv

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)
Digital Geologic Map Data for the Ozark National Scenic 

Riverways and Adjacent Areas Along the Current River 

and Jacks Fork, Missouri

By David J. Weary, Randall C. Orndorff, Richard W. Harrison, and Robert E. Weems

Abstract

The geology of the Ozark National Scenic Riverways 

(ONSR) in southern Missouri has been mapped at 1:24,000 

scale. This endeavor was achieved through the combined 

efforts of U.S. Geological Survey and Missouri Geological 

Survey individual quadrangle mapping and additional fieldwork by the authors of this report. Geologic data covering the 

area of the ONSR and a 1-mile (1.6-kilometer) buffer zone 

surrounding the park, as well as geologic data from a few key 

adjoining areas, have been compiled into a single, seamless 

geographic information system database. The intent is to 

provide base geologic information for natural science research 

and land management in the park and surrounding areas. The 

data are served online at ScienceBase (https://www.sciencebase.gov/catalog/), where they are provided in Environmental 

Systems Research Institute (ESRI) file geodatabase format, 

and are accompanied by metadata files. These data can be 

accessed at: http://dx.doi.org/10.5066/F7CJ8BKB. Additional 

detailed geologic information about the ONSR and surrounding areas is available in the separate 1:24,000-scale quadrangle 

maps and in a 1:100,000-scale map and report on the regional 

geology.

Introduction

Purpose

Geologic map data were created and compiled to provide 

seamless 1:24,000-scale coverage for an area that contains the 

entire Ozark National Scenic Riverways (ONSR) and completes a geologic inventory sponsored by the National Park 

Service (NPS), Geologic Resources Division. These data are 

intended to provide geologic information to ONSR personnel and their scientific cooperators for use in various natural 

resource and land classification studies. This report includes a 

brief summary of the geology of the park area; refer to http://

dx.doi.org/10.5066/F7CJ8BKB (Weary and others, 2016).

For more detailed and site-specific geologic descriptions and discussions, the reader should refer to the individual 

1:24,000-scale quadrangle reports that are the basis for most 

of this report (fig. 1; table 1). In addition, Weary and others (2014) provide a comprehensive discussion of various 

geologic aspects of the entire region, and Lowell and others 

(2010) provide detailed descriptions of selected geologic and 

karst-related features in and around the ONSR area.

Scope of the Data

The spatial extent of these data covers the ONSR as well 

as areas extending 1 mile (mi) (1.6 kilometer [km]) beyond the 

exterior park boundaries. In addition, several other areas along 

the Current River and Jacks Fork are included for continuity 

of coverage along the rivers. These areas are (1) part of the 

headwaters area of the Current River in the vicinity of Montauk Springs and Montauk State Park; (2) the headwaters area 

of Jacks Fork; (3) the reach of Jacks Fork near the town of 

Eminence that is not within the ONSR; and (4) a reach of the 

Current River near the town of Van Buren that is not within 

the ONSR (fig. 1).

Geologic data include (1) polygons describing the extent 

and distribution of bedrock units, areas of overlying surficial 

deposits, and the location and extent of karst sinkholes; (2) 

lines marking the traces of mapped faults, mapped fold axes, 

and the contacts of both the bedrock and surficial map units; 

and (3) points marking the location and measurement values 

of bedding attitude in sedimentary rocks or foliation in igneous rocks.

Geographic information system (GIS) data representing the boundaries of the ONSR and the 1:24,000-scale U.S. 

Geological Survey (USGS) topographic quadrangles are also 

included for geographic reference.

Original Data Sources

Data in this report were compiled chiefly from geologic 

map databases generated by the USGS and the Missouri Geological Survey (fig. 1; table 1). For geologic coverage of the 
2 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

ONSR and the surrounding area that lies outside of the completed quadrangle maps (fig. 1; table 1), data were compiled 

from the regional geologic map of the area (Weary and others, 

2014) and augmented by additional fieldwork by the authors.

Sinkhole location data were derived from the published 

geologic maps and from the USGS 1:24,000-scale base topographic maps with 20-foot (ft) (6-meter [m]) contour intervals. 

Sinkholes less than 10 m (33 ft) in diameter are all represented 

as 10-m-diameter circular polygons.

Some surficial units were mapped in only one or two 

quadrangles. See the Description of Map Units for notes on 

the limited distribution of these units.

Geologic Description

The ONSR lies in the southeastern part of the Ozark Plateaus physiographic province of central and southern Missouri 

(fig. 1). The geology of the ONSR comprises a Mesoproterozoic (~1.4-Ga) (giga-annum)-age basement of intrusive and 

extrusive igneous rocks, discomformably overlain by relatively flat-lying Cambrian and Lower Ordovician (~500‒470 

Ma) (mega-annum) sedimentary rocks, on which various 

surficial and residual sedimentary units are superposed (fig. 2). 

Basement rocks of Mesoproterozoic age, chiefly granite and 

rhyolite, are exposed as erosional remnant hills in an uplifted 

area near the central part of the park (fig. 1). The overlying 

Paleozoic sedimentary rocks are chiefly dolomite that contains interlayers of quartz sandstone and chert (fig. 3). Only 

geologic units exposed at the land surface in the ONSR are 

described herein. For descriptions of subsurface units in the 

project area, see the individual quadrangle reports (table 1) or 

Weary and others (2014).

The bedrock in the ONSR area is cut by numerous faults 

having northwest-southeast and northeast-southwest trends. 

These are chiefly vertical strike-slip faults resulting from 

stresses associated with the late Paleozoic ancestral Rocky 

Mountain-Ouachita-Alleghenian orogenic systems, as the 

Ouachita front is only about 200 km to the south; see Cox 

(2009) and Hudson (2000) for analyses of late Paleozoic faulting in the Ozark region. The entire exposed Paleozoic section 

is pervasively karstified.

For a more complete discussion of the geology in the 

ONSR and surrounding area, see the individual quadrangle 

source publications (listed in table 1) as well as regional 

descriptions in Lowell and others (2010) and Weary and 

others (2014).

Table 1. List of quadrangle maps completed in the Ozark National Scenic Riverways and vicinity 

by the U.S. Geological Survey and the Missouri Geological Survey and used as sources for this 

compilation. See References Cited for full citations. Numbers correspond to quadrangle locations in 

figure 1.

Quadrangle 

number in 

figure 1

Quadrangle(s) Author(s) Year of publication 

1 Montauk Weary 2015

2 Cedargrove Weary 2008

3 Round Spring Orndorff and Weary 2009

4 Alley Spring Weary and Orndorff 2012

5 Eminence Orndorff and others 1999

6 Powder Mill Ferry McDowell and Harrison 2000

7 Jam Up Cave and Pine Crest Weary and others 2013

8 Stegall Mountain Harrison and others 2002

9 Van Buren North Weary and Weems 2004

10 Van Buren South Weary and Schindler 2004

11 Big Spring Weary and McDowell 2006

12 Grandin SW Baker 1999a, 1999b
Geologic Description 3

Figure 1. Simplified geologic map of the Ozark National Scenic Riverways area based on the 1:24,000-scale geographic information 

system (GIS) data provided in this report. The various Mesoproterozoic igneous rock and Cenozoic surficial map units identified in the 

GIS data are not differentiated. The geology in the subdued part of the figure, outside of the report area (that is, outside the boundary of 

geologic data in this report), is modified from Weary and others (2014; available online at: http://pubs.er.usgs.gov/publication/sim3280). 

Also shown are the locations of individual geologic maps (gray rectangles) published by the U.S. Geological Survey and the Missouri 

Geological Survey from 1999 to 2015. Bold numbers in the rectangles correspond to quadrangle maps listed in table 1. See References 

Cited for full citations.

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9 10 KILOMETERS

10 MILES

UTM Projection

North American Datum of 1983

37o 15’ 00”

37o 07’ 30”

37o 00’ 00”

36o 52’ 30”

91o 45’ 00” 91o 37’ 30” 91o 30’ 00” 91o 22’ 30” 91o 15’ 00” 91o 07’ 30” 91o 00’ 00” 90o 52’ 30”

37o 22’ 30”

37o 30’ 00”

1 2

3

4

5

7 8 9

10 11

12

6

Van Buren

Montauk Springs

Montauk

State Park

Eminence

Jacks Fork

 River

 River

Current 

Current 

Blair Creek

Study

Area

MISSOURI

OZARK PLATEAUS

Map Location

Surficial deposits

Jefferson City Dolomite

Roubidoux Formation

Gasconade Dolomite

Eminence Dolomite

Potosi Dolomite

Mesoproterozoic igneous rocks

Map Units

Ozark National Scenic Riverways boundary

Boundary of geologic data in this report

Fault

Area of reported base-metal deposits in the 

subsurface

EXPLANATION
4 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

CORRELATION OF MAP UNITS

ORDOVICIAN

CAMBRIAN

MESOPROTEROZOIC

Lower

Ordovician

Upper 

Cambrian

Unconformity

Ycu

Ycl

Yltm

Ysc Ysi Ysm

Ymm

Yrm

Yvc

Yg

Unconformity

Unconformity

Og

Or

Ojc

QUATERNARY Holocene and

Pleistocene

TERTIARY

MESOZOIC?

Qm Qls

QTg

Qt

Qa

Ql

QTrr

Qtl

QTtrc

QTr

Qc

Figure 2. Correlation of map units exposed in the Ozark National Scenic Riverways and adjacent 

areas along the Current River and Jacks Fork, within the boundary of geologic data in this report.
Geologic Description 5

PROTEROZOIC 

IGNEOUS ROCKS 

are locally exposed 

adjacent to overlying

units upsection into

the Gasconade Dolomite.

200 Feet

50 Meters

x

x x x x

x x

Gasconade Dolomite (Og)

LOWER ORDOVICIAN

Upper unit Lower unit Middle unit

Gunter

Sandstone

Member

lower

part

middle

part

upper

part

Eminence

Dolomite

Potosi

Dolomite

Roubidoux 

Formation

(Or)

Jefferson City

Dolomite 

(Ojc)

x x

x x

x

“Quarry 

 ledge”

UPPER CAMBRIAN

Formation

Age

(map unit) Lithology

Cryptozoon chert

(p)

(e)

Thin oolite bed (<1ft)

EXPLANATION 

Dolomite

Cryptozoon chert

Dolomite with quartz druse in vugs

Shaly dolomite

Sandy dolomite

Cherty dolomite

x x

x x

Sandstone and orthoquartzite

()

Figure 3. Idealized stratigraphic column for the Ozark National Scenic 

Riverways area showing lithostratigraphic units which include outcropping 

Paleozoic formations and Proterozoic rocks. Abbreviation: , Precambrian 

(Mesoproterozoic) rocks.
6 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

Description of Map Units

Surficial Units

Qa Alluvium (Holocene)—Gravel, sand, and clay 

confined to the bed and active flood plains of 

modern stream valleys. Material consists mostly 

of subrounded to subangular chert, sandstone, and 

quartzite clasts in a matrix of sand containing silt 

and clay. Thickness ranges from 0 to as much as 20 

ft (6 m)

Qc Colluvium (Holocene and Pleistocene)—Boulders, cobbles, and pebbles of sandstone derived 

from weathering of the Roubidoux Formation. 

Commonly forms gravity-creep deposits a few feet 

thick on steep slopes in the upper part of the Gasconade Dolomite immediately below the Roubidoux 

residuum. Mapped as a unit in the Powder Mill 

Ferry quadrangle only (McDowell and Harrison, 

2000). Widely distributed and common on steep 

slopes; shown on map only where thickest and most 

extensive

Qm Muck and clayey silt (Holocene and Pleistocene?)—Silt, reworked loess, clay, and organic-rich 

muck filling sinkholes that intermittently retain 

water. Mapped as a unit in the Jam Up Cave and 

Pine Crest quadrangles only (Weary and others, 

2013). Thickness unknown

Qls Landslide deposits (Holocene and Pleistocene?)—Chaotic jumble of dolomite, chert, 

sandstone, and quartzite clasts in a clayey and silty 

matrix. Includes large landslides and large-scale 

slump bodies with hummocky topography, 20 to 

100 ft (6 to 30 m) thick. Mapped in the Van Buren 

North quadrangle only (Weary and Weems, 2004), 

but similar deposits are found in areas of steep 

topography in other quadrangles

Qt Terrace deposits (Holocene and Pleistocene?)—

Large cobble-size to sand-size, subrounded to 

subangular chert, sandstone, and quartzite clasts 

within a matrix of sand, silt, and clay. In some locations a significant fraction of the matrix is reworked 

silt-size loess. Occurs on margins of modern stream 

valleys, but above normal seasonal floods of present 

streams. Terraces along the major streams usually 

stand at least 6 to 10 ft (2‒3 m) above stream level. 

Thickness at least 10 ft, and possibly more along 

larger stream courses

Qtl Loess-covered terrace deposits (Pleistocene?)—

Predominantly silt with lesser sand and clay. 

Mapped as a unit only in the Stegall Mountain 

quadrangle (Harrison and others, 2002) and the 

Van Buren South quadrangle (Weary and Schindler, 

2004). Occurs on slopes above the valleys of various large streams and also is preserved in a few 

large sinkholes. A well-developed soil horizon 

(probably equivalent to the Sangamon Geosol) 

occurs beneath the loess. Windblown silt, as much 

as 1 ft (0.3 m) thick, mantles clay, silt, and sand, 

with minor pebbles. May be as much as 40 ft (12 m) 

thick

Ql Loess (Pleistocene)—Silt. This unit was mapped 

in only one location, in the Stegall Mountain 

quadrangle, but it also occurs as small areas of 

thin veneer elsewhere in the study area (Harrison 

and others, 2002). Discontinuous patches occur on 

hillcrests and ridges, including some of the highest 

parts of Thorny Mountain. Silt is commonly mixed 

with residuum, probably because of bioturbation. As 

much as 5 ft (1.5 m) thick

QTtrc Residual and colluvial material on terrace-like 

landforms (Quaternary and Tertiary)—Silt, clay, 

sand, and gravel. Unit was mapped in the Stegall 

Mountain quadrangle only (Harrison and others, 

2002). Occurs as terrace-like landforms that are 

found most commonly adjacent to knobs of Mesoproterozoic volcanic rocks in the northern part of 

the quadrangle. In part residual and in part colluvial 

in nature. Commonly covered by a thin veneer 

of loess, as much as 5 ft (1.5 m) thick. A welldeveloped soil horizon (possibly equivalent to the 

Sangamon geosol) commonly occurs beneath the 

loess. Gradational into Quaternary terrace deposits 

(Qt, Qtl). As much as 60 ft (18 m) thick

QTrr Residuum derived from Roubidoux Formation 

(Quaternary and Tertiary)—Red and reddishorange sandy clay containing angular sandstone 

and chert cobbles and boulders as much as 6 ft 

(2 m) in diameter. Sandstone cobbles and boulders, fine- to coarse-grained, poorly sorted, and 

locally containing symmetrical and asymmetrical 

ripple marks. Chert cobbles and boulders, light- to 

medium-gray, consisting of banded, sandy, oolitic, 

and porcelaneous varieties. Unit is widespread but 

was not mapped in all quadrangles; however, where 

mapped, only locations where it was identified via 

ground traverse are indicated. Occurs on hilltops 

where bedrock of the Roubidoux Formation has 

been deeply weathered. Roubidoux residuum was 

mapped only in areas where it directly overlies 

older formations, and no in-situ Roubidoux bedrock 

was inferred; unmapped Roubidoux residuum exists 
Description of Map Units 7

virtually everywhere that the Roubidoux Formation 

occurs. As much as 40 ft (12 m) thick

QTg Upland gravel deposit (Quaternary and Tertiary)—Gravel deposits, as high as 300 ft (91 m) 

above the modern-stream flood plains, containing mostly subrounded to rounded clasts of chert, 

sandstone, and quartzite in a matrix of silty sand. 

Mapped only in the Van Buren North quadrangle 

(Weary and Weems, 2004). Clasts of fossiliferous 

Mississippian chert are rare to abundant. Thickness 

generally less than 10 ft (3 m)

QTr Peck Ranch unit (Quaternary and Tertiary, 

and Mesozoic?)—Brown, red, and reddish-orange 

sandy clay containing angular blocks, cobbles, and 

pebbles of sandstone, and various varieties of chert. 

Insoluble, residual material derived from intense insitu weathering of Paleozoic rocks, largely from the 

Roubidoux Formation downward through the upper 

Eminence Dolomite. Unit was mapped only in the 

Stegall Mountain quadrangle (Harrison and others, 

2002). Crude stratigraphic sequence is generally 

preserved. At least 200 ft (61 m) thick

Paleozoic Bedrock Units

Ojc Jefferson City Dolomite (Lower Ordovician)—

Dolomite, quartz sandstone, and chert. Dolomite is 

light brown, medium to fine grained, argillaceous, 

and thin to thick bedded; commonly weathers 

powdery pale yellow. Lenses of quartz sandstone 

and orthoquartzite as well as beds and nodules of 

white chert are also common. In some areas an 

interval of brown, medium-grained, thick-bedded 

to massive, pitted-weathering siliceous dolomite 

informally known as the “Quarry Ledge” crops 

out. The “Quarry Ledge” occurs between 25 and 

40 ft (8–12 m) above the base of the Jefferson 

City Dolomite, making it a useful marker for the 

Roubidoux-Jefferson City contact, which is seldom 

exposed. The Jefferson City Dolomite weathers to a 

characteristic yellowish color and produces a more 

silty, less sandy soil than the underlying Roubidoux 

Formation. Residual sandstone and orthoquartzite 

float from the Jefferson City are usually less tabular 

in shape than those produced from the Roubidoux. 

These characteristics enable differentiation between 

Roubidoux and Jefferson City bedrock in areas 

having no outcrop. The Jefferson City Dolomite 

is sparsely fossiliferous, but has yielded trilobites 

and conodonts as reported by Repetski and others 

(1998). This formation has an average thickness of 

about 200 ft (61 m) (Thompson, 1995). Typically, 

considerably less than the full thickness of this unit 

is exposed in the ONSR area

Or Roubidoux Formation (Lower Ordovician)—

Sandstone, orthoquartzite, dolomite, sandy dolomite, and chert. Sandstone is white to pale orange, 

fine to coarse grained, thin to thick bedded, generally poorly sorted, and commonly crossbedded and 

ripple marked; weathers light brown to reddish 

brown. Dolomite is light to medium gray, very fine 

to coarse grained, and thin to medium bedded. Chert 

is white to medium gray, locally sandy and oolitic; 

occurs in thin beds, lenses, and nodules. Typically 

formation is highly weathered and not well exposed. 

Thickness ranges up to 250 ft (76 m)

Og Gasconade Dolomite (Lower Ordovician)—

Dolomite, chert, sandstone, and orthoquartzite. 

Formation can be divided into three informal units, 

the lower, middle, and upper (fig. 3), which are 

not shown separately in figure 1. Upper unit is 

typically light-gray, medium- to coarse-grained, 

thick-bedded, vuggy dolomite. Weathered surfaces 

are commonly pitted. Middle unit is further divided 

into lower, middle, and upper parts. The upper part 

of the middle unit is typically light-gray, fine- to 

coarse-grained, medium- to thick-bedded dolomite, 

and contains white to light-gray chert nodules and 

lenses. The uppermost bed of the upper part of the 

middle unit is a regionally persistent white Cryptozoon chert, 2 to 10 ft (0.6–3 m) thick, commonly 

used to map the Roubidoux/Gasconade contact, 

which rarely is exposed. This contact is placed at 

approximately 80 to 100 ft (24–30 m) above the 

Cryptozoon chert, which is an average of observed 

intervals. The middle part of the middle unit is lightgray to very light gray, medium- to coarse-grained, 

medium-bedded dolomite containing chert as 

nodules, stringers, and beds. Chert varieties are porcelaneous, oolitic, porous with druse, and stromatolitic. A locally persistent oolite bed, occurring at the 

base of the middle part of the middle unit (Orndorff 

and Harrison, 2001), defined the top of the Van 

Buren Formation of Bridge (1930). Beds of the 

lower part of the middle unit, formerly called the 

Van Buren Formation by Bridge (1930), are lightgray to yellowish-gray, fine- to medium-grained, 

thin- to medium-bedded dolomite. The lower unit of 

the Gasconade Dolomite, called the Gunter Sandstone Member, is a light-gray to white sandstone, 

sandy dolomite, or orthoquartzite interbedded with 

light-gray to tan, fine-grained, thin-bedded dolomite. The Gunter Sandstone Member ranges from 

10 to 25 ft (3–8 m) in thickness. In some localities 

the sandstones in the Gunter thin and exist only as 

discontinuous thin lenses. In some locations there 
8 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

is no quartz sandstone, making identification of the 

base of the Gasconade difficult. The thickness of the 

Gasconade Dolomite ranges from as much as about 

770 ft (235 m) to as little as 148 ft (45 m) in areas 

adjacent to the Proterozoic volcanic knobs. The 

Gasconade is the youngest Paleozoic unit observed 

in contact with Mesoproterozoic igneous rocks in 

the Current River basin. Contact with the underlying Eminence Dolomite, which is unconformable, is 

placed at the base of the lowest sandstone or sandy 

dolomite of the Gunter Sandstone Member

Єe Eminence Dolomite (Upper Cambrian)—Dolomite, sandstone, and chert. Dolomite is light gray, 

medium to coarse grained, massive to thick bedded 

and commonly stromatolitic. It typically weathers 

bluish gray and medium gray, has a pitted surface, and commonly crops out as small knobs or 

pinnacles. Many fresh surfaces contain oxidized 

rust-colored mottles. Unit contains variable amounts 

of chert throughout, commonly as light-gray and 

white stringers and nodules. In downstream areas 

of the Current River basin a 10- to 20-ft (3–6 m)-

thick interval consisting of interbedded thin, friable 

to silicified quartz sandstone and sandy dolomite 

occurs 50 to 80 ft (15–24 m) below the upper 

contact. The thickness of the Eminence Dolomite is 

variable, in part because of the unconformity at the 

top of the unit and in part because of thinning near 

knobs of Mesoproterozoic volcanic rocks; thickness 

ranges from about 80 ft (24 m) to as much as about 

919 ft (280 m). Contact with the underlying Potosi 

Dolomite is indistinct, a condition that is likely 

related to secondary alteration (silicification) rather 

than to primary deposition

Єp Potosi Dolomite (Upper Cambrian)—Dolomite 

with chert. Dolomite is light brown, brown, and 

light gray, fine to medium grained, massive to thick 

bedded, with vugs that contain quartz druse. Brown 

dolomite has fetid odor when freshly broken. Quartz 

druse is developed as botryoidal masses of chalcedony and small quartz crystals coating surfaces. 

White to light-gray chert forms nodules and stringers. Locally, a 1- to 3-ft (0.3–1 m)-thick bed of 

rusty-weathering porous chert occurs at or close to 

the contact with the overlying Eminence Dolomite. 

The Potosi is the oldest sedimentary unit exposed in 

the ONSR area. The thickness of the Potosi ranges 

from about 50 to 575 ft (15–175 m) in the Current 

River basin; however, in the map area only about 

180 ft (55 m) of the upper Potosi is exposed

Mesoproterozoic Intrusive Rocks

Yg Granite of Sims’ (1990) Y1g province and 

Kisvarsanyi’s (1981) Silvermine-Slabtown-type 

granite (Granite of Weary and McDowell (2006), 

known informally as Big Spring granite)—Granite, red, medium-grained and seriate, with clots of 

altered amphibole set in a semi-graphic intergrowth 

of quartz and alkali feldspar. The alkali feldspar 

exhibits Carlsbad twinning and some relict perthite 

of the herringbone type. Most perthite is disturbed 

and shows patch texture, chessboard character, and 

swapped rims. Accessory mineral phases include 

fluorite, zircon, and magnetite accompanied by secondary clay, sericite, and epidote. The only outcrop 

in the report area is in the Big Spring quadrangle 

(sec. 29, T. 27 N., R. 1 E.) (Weary and McDowell, 

2006). This outcrop has a U-Pb age of 1,461.8±5.5 

Ma (Harrison and others, 2000). Other reported 

U-Pb ages for unit Yg from drill-hole samples 

collected outside of but near the report area are 

1,473±15 Ma (Van Schmus and others, 1993) in the 

Van Buren South quadrangle (Weary and Schindler, 

2004); 1,480±42 Ma (Van Schmus and others, 1993) 

in the Winona quadrangle (Orndorff and Harrison, 

2001); and 1,473±15 Ma (Bickford and others, 

1981) in the Round Spring quadrangle (Orndorff 

and Weary, 2009). These ages are consistent with 

other reported ages for unit Yg elsewhere in the 

Missouri Ozarks (see Van Schmus and others, 1993; 

Bickford and others, 1981).

Mesoproterozoic Volcanic Rocks

Upper Sequence of Mesoproterozoic Volcanic 

Rocks

Yrm Rhyolite of Russell Mountain—Ash-flow tuff. 

Named for exposures on Russell Mountain, which 

spans sec. 2, T. 28 N., R. 2 W. of the Stegall Mountain quadrangle (Harrison and others, 2002) and 

sec. 35, T. 29 N., R. 2 W. of the Powder Mill Ferry 

quadrangle (McDowell and Harrison, 2000). Unit is 

moderately crystal rich, containing 10 to 20 percent 

(by volume) pink alkali feldspar phenocrysts that 

are locally altered pale green, with sparse to no 

quartz, and 5 to 10 percent magnetite and hematite grains. Unit is typically densely welded with 

well-developed flow banding and eutaxitic texture, 

although locally it is massive with poorly developed 

or no flow banding. This ash-flow tuff is interpreted 

to consist of multiple flows of both simple and compound cooling units. Primary foliations are typically 

steeply dipping and generally strike N. 40 ̊–50 ̊ W. 
Description of Map Units 9

The steep dip of foliations (ranging from 25 ̊ to 90 ̊ 

and averaging about 76 ̊; n=27) is interpreted to 

have been produced from rotation during caldera 

collapse (Harrison and others, 2000). Relation to the 

Tuff of Little Thorny Mountain (Yltm) is uncertain 

but is possibly, in part, correlative. Thickness of this 

unit is difficult to determine because of rotation, but 

it is at least several thousand feet (1,000 m)

Yvc Volcaniclastic conglomerate, breccia, and sandstone—Interbedded volcaniclastic conglomerate, 

breccia, and sandstone. Conglomerate consists of 

subrounded cobbles, 3 to 5 inches (in.) (8–13 centimeters [cm]) in diameter, and large pebbles derived 

from the rhyolite of Sutton Creek (Ysc), the upper 

unit of Coot Mountain (Ycu), and other unidentified 

volcanic rocks, with a strongly altered, greenish, 

fine-grained volcaniclastic matrix. Conglomerate 

is overlain by strongly silicified volcanic breccia, 

possibly an autobrecciated flow, that consists of 

aphanitic pink rhyolite and quartz clasts in a quartz 

matrix. Sandstone is coarse to medium grained. 

Grains consist of quartz, lithic fragments, and minor 

feldspar. Volcaniclastic unit was observed only on 

the southern side of Coot Mountain, in secs. 22 and 

23, T. 29 N., R. 3 W., in the Eminence and Powder 

Mill Ferry quadrangles (Orndorff and others, 1999; 

McDowell and Harrison, 2000). Contacts with other 

units not exposed

Ysc Rhyolite of Sutton Creek—Lava(?) of alkali 

rhyolite to rhyolite composition that is generally 

not flow layered, although flow layering is observed 

locally. Phenocrysts of 7 to 15 percent pink feldspar 

in a dark-pink matrix; 15 to 20 percent disseminated 

magnetite. Contains trace to 10 percent conspicuous, large (as much as 0.4 in.) (1 cm) aggregates 

(possibly xenoliths) of small pink feldspar phenocrysts in an apple-green matrix, which alter yellowish white. Named for exposures 0.25 mi (0.4 km) 

north of Sutton Creek in the Eminence quadrangle 

(Orndorff and others, 1999), in sec. 12, T. 29 N., 

R. 4 W. Unit is also exposed along the northwest 

bank of the Current River in a knob 0.5 mi (0.8 

km) southeast of the summit of Tip Top Mountain, 

and along the south bank of the Current River in an 

unnamed knob 1.0 mi (1.6 km) upstream from the 

confluence with Jacks Fork. Thickness unknown

Ysi Rhyolite of Shut-In Mountain—Dense lava of 

rhyolite to alkali trachyte. Named for exposures 

on and around Shut-In Mountain in the Stegall 

Mountain quadrangle (secs. 2 and 11, T. 28 N., R. 

3 W.). Unit varies from moderately crystal rich to 

crystal rich, with phenocrysts ranging from 12 to 

30 percent by volume. This unit typically contains 

approximately 10 to 15 percent white to pink alkali 

feldspar; 3 to 5 percent anhedral to euhedral quartz 

phenocrysts; common (but sporadic) blebs, pods, 

or disseminations of fluorite; and <1 to 3 percent 

disseminated magnetite-hematite grains in a dense, 

light-pink to maroon-red matrix that consists of 

a cryptocrystalline aggregate of quartz, alkali 

feldspar, and iron oxides. Flow banding is generally non-existent to poorly developed; however, 

where present, it typically swirls and commonly 

displays flow folding. Locally, this unit is autobrecciated. Small zones of hydrothermal brecciation 

also occur locally. Vesicles mineralized with quartz 

and feldspar are common. This unit is interpreted 

as coalesced lava flows and domes. Areas of 

hydrothermal brecciation and inclusion of exotic 

aphanitic volcanic clasts are interpreted as marking 

probable vent sites. U-Pb analyses of one multiplecrystal and five single-crystal fractions from this 

unit yielded an age of 1,470.4±2.7 Ma (Harrison 

and others, 2000). In part, this unit is the same 

as the Stegall Rhyolite of Tolman and Robertson 

(1969, p. 14–15). Minimum thickness 900 ft (275 

m)

Ysm Rhyolite of Stegall Mountain—Dense lava of 

rhyolite to alkali trachyte. Named for exposures on 

Stegall Mountain in secs. 19 and 20, T. 28 N., R. 2 

W., in the Stegall Mountain quadrangle (Harrison 

and others, 2002). This unit is a variation of the 

rhyolite of Shut-In Mountain in that it has a lower 

quartz phenocryst content of 0.5 to 2 percent. Otherwise, it is identical and is interpreted as genetically 

related. Minimum thickness is 200 ft (61 m)

Ymm Tuff of Mule Mountain—Air-fall tuff. Mapped on 

Mule Mountain and the southern flanks of Stegall 

Mountain in secs. 19, 20, 21, 29, and 30, T. 28 N., 

R. 2 W., and sec. 24, T. 28 N., R. 3 W., in the Stegall 

Mountain quadrangle. Unit is dense, aphanitic, 

finely laminated, and commonly silicified. Phenocrysts are rare and consist dominantly of angular 

quartz. Accretionary lapilli (lapilli-size pellets of 

ash formed by rainfall passing through a downwind 

ash cloud or by accretion from a moisture-laden 

eruption column) are relatively common. Base of 

this unit marks an angular unconformity between 

the upper and lower sequences of volcanic rocks in 

the Stegall Mountain area. The contact with overlying units (Ysm and Ysi) is sharp and conformable. 

The contact with the underlying unit (Yltm) is 

complex and irregular. Unit was mapped only where 

its thickness exceeds 30 ft (9 m), but it is present 

everywhere between upper and lower sequences. 

Thickness ranges from 15 ft (4.5 m) to perhaps as 

much as 100 ft (30 m)
10 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

Lower Sequence of Mesoproterozoic Volcanic 

Rocks

Yltm Tuff of Little Thorny Mountain—Ash-flow tuff. 

Named for exposures on Little Thorny Mountain, 

in sec. 22, T. 28 N., R. 2 W., in the Stegall Mountain quadrangle (Harrison and others, 2002). Unit 

is dense, dark maroon to purple, moderately crystal 

rich to crystal rich, and quartz poor. Phenocryst content varies from 5 to 20 percent and consists almost 

exclusively of alkali feldspar; quartz is very rare to 

absent. Magnetite and hematite grains constitute 2 

to 10 percent of the rock; fluorite blebs and disseminations are common. Sinha and Kisvarsanyi (1976) 

describe euhedral phenocrysts of relict fayalite, or 

possibly an iron pyroxene, which are now altered to 

hematite, calcite, sericite, and epidote. Unit contains fiamme and eutaxitic texture, is moderately to 

densely welded, and is commonly, but not everywhere, flow banded. Primary foliations are typically 

steeply dipping and generally strike N. 40 ̊–50 ̊ W. 

Steeply dipping foliations are interpreted as having 

been produced by rotation during caldera collapse 

(Harrison and others, 2000). Thickness of unit is 

difficult to determine because of rotation, but unit is 

at least several thousand feet thick (1,000 m)

Ycu Upper Coot Mountain unit—Rhyolite to alkali 

rhyolite to alkali trachyte ash-flow tuff, densely 

welded, with well-developed flow layering and 

eutaxitic texture; locally, flow layering is poorly 

developed. Primary foliations are typically steeply 

dipping. Generally less than 10 percent phenocrysts of pink feldspar and sparse to no quartz; 4 

to 10 percent disseminated magnetite throughout; 

locally contains disseminated fluorite. Vapor-phase 

feldspar and quartz mineralization are common in 

pumice. Unit is exposed principally at the summit 

and along the northeast side of Coot Mountain, 

along the eastern side of Jerktail Mountain, and on 

the summit and slopes of Wildcat Mountain in the 

Eminence and Powder Mill Ferry quadrangles. Unit 

is approximately the same as the upper unit of Coot 

Mountain of Fisher (1969)

Ycl Lower Coot Mountain unit—Dominantly ash-flow 

tuff interbedded with air-fall tuff and lava(?). Ashflow tuff is composed of alkali rhyolite to alkali 

trachyte to trachyte to rhyolite; commonly massive 

and dense. Flow layering weakly developed or 

nonexistent, although moderately developed locally. 

Five to 25 percent phenocrysts of pink feldspar and 

sparse to no quartz in a dark-maroon matrix, with 

4 to 10 percent disseminated magnetite throughout. 

Commonly contains quartz occurring as veins and 

infillings of miarolitic cavities, locally spherulitic. 

Locally, poorly welded to non-welded, pumicerich, phenocryst-poor ash-flow tuff is interbedded 

in this interval. Ash-flow tuff is approximately 

the same as the middle unit of Coot Mountain of 

Fisher (1969). Air-fall tuff is composed of rhyolite; 

is aphanitic, thin to massive bedded, dark maroon, 

locally silicified, and contains disseminated pyrite. 

Petrographically consists of microlites less than 

0.0004 in. (0.01 mm) in size and devitrified glass 

shards. Generally, all primary depositional features 

have been destroyed. Air-fall tuff is approximately 

the same as the lower unit of Coot Mountain of 

Fisher (1969). Unit is best exposed in the Eminence 

quadrangle and central west edge of the Powder 

Mill Ferry quadrangle, along the southwestern 

side of Coot Mountain, the western side of Jerktail 

Mountain, and on an unnamed knob exposed along 

Missouri Route 106, 1.25 mi (2.0 km) east of the 

town of Eminence

Structural Geology

The Mesoproterozoic volcanic rocks exposed in the 

ONSR area exhibit foliation related to original subaerial 

deposition, gravity flows, and post-depositional shearing of the 

rocks. Measured planes of foliation strike in various directions 

and typically dip steeply to vertical, with the lowest recorded 

dip value being 30°. Some of these steep to vertical dips are 

related to strike-slip shearing and to rotation of blocks during 

caldera collapse of the Eminence caldera (Kisvarsanyi, 1977, 

1984).

Most of the sedimentary strata in the ONSR are flatlying to subhorizontal, with the vast majority of bedding 

measurements indicating dips of less than 3° locally. The 

regional dip direction for the entire ONSR is generally 

to the southeast, and the gradient of the Current River 

follows this incline. The sedimentary rocks commonly dip 

radially away from exposed and buried igneous knobs in the 

Mesoproterozoic basement. The highest dip value measured 

in the study area was 57° in beds adjacent to a buried igneous 

knob in the Powder Mill Ferry quadrangle (McDowell and 

Harrison, 2000).

Folds are difficult to identify in the map area due to 

lack of exposure and to vegetative cover; however, where 

observed, these folds are open and symmetrical. Individual 

folds were mapped in only a few quadrangles. These include 

the Montauk, Cedargrove, Pine Crest, Round Spring, Van 

Buren North, and, Grandin SW quadrangles.

Faults in the map area are also difficult to observe 

directly due to vegetation and residuum cover, and usually 

have to be identified on the basis of indirect evidence. This 

evidence includes (1) vertical offset of stratigraphically 

equivalent strata in which observed dip angles are insufficient 
Geologic Resources 11

to explain the change, and (2) cataclastic deformation bands 

observed in float blocks of sandstone. Although only vertical 

offset was observed on faults in the map area, the faults are 

interpreted to be predominantly strike-slip on the basis of 

observations of similar faults exposed in subsurface basemetal mines in nearby quadrangles. Fault movement has taken 

place over time, with most strike-slip movement probably 

occurring during the Ouachita orogeny.

Similar to Mesoproterozoic rocks in the St. Francois 

Mountains, basement rocks in the map area also lack any 

penetrative structural fabric, indicating that these rocks have 

never been buried more than a few kilometers (Kisvarsanyi, 

1981). In the field area, the observed and inferred fault pattern 

developed in Paleozoic rocks is similar to that found in 

basement rocks, leading to the conclusion that the Proterozoic 

basement fabric exerted a controlling influence on younger 

Paleozoic structures. Regionally there are two dominant 

fault trends, one oriented northeast and the other oriented 

northwest. Lesser north-trending and east-trending faults have 

been mapped locally. Similar trends in regional strike patterns 

are described elsewhere in southeastern Missouri (McCracken, 

1971; Harrison and Schultz, 2002). This northeast-northwest 

bimodal structural trend is widely thought to be inherent from 

structures in the Proterozoic basement rocks (McCracken, 

1971; Kisvarsanyi, 1974; Kisvarsanyi and Kisvarsanyi, 1976; 

Clendenin and others, 1989, 1993; Lowell, 2000; Harrison and 

Schultz, 2002).

On the basis of tectonically disturbed strata, three 

broad age groups of faults are discernible: (1) those 

showing evidence that they were active only during the 

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

times prior to deposition of the Ordovician section (that is, 

Neoproterozoic through Late Cambrian), and (3) those that 

were active at one or more times in the Phanerozoic and 

probably during the Proterozoic. From field relations observed 

in the map area, we can determine that the youngest faulting 

is post-Ordovician in age. Faults of age group 3, in part, are 

likely associated with the late Paleozoic ancestral Rocky 

Mountain-Ouachita-Alleghenian orogenic systems, as the 

Ouachita front is only about 125 mi (200 km) to the south; see 

Cox (2009) and Hudson (2000) for analyses of Late Paleozoic 

faulting in the Ozark region. Tectonic features (Craig and 

Connor, 1979) show that uplift in northwestern and central 

Missouri had begun in the Late Mississippian, producing 

an elongated northwest-trending ridge that projects through 

the map area along the central Missouri tectonic zone of 

Kisvarsanyi (1981, 1984).

Paleontology

The igneous rocks comprising the Proterozoic basement 

complex beneath the ONSR are devoid of fossils. The 

Paleozoic sedimentary rocks contain a variety of fossils of 

various types. Algal structures such as laminae, stromatolites, 

and other Cryptozoon buildups are ubiquitous and common 

locally throughout the dolomite and chert parts of the section. 

They are particularly well preserved in chert beds, one 

notable example being the Cryptozoon chert that occurs in 

the uppermost part of the middle interval of the Gasconade 

Dolomite (Bridge, 1930; Lowell and others, 2010).

Trace fossils such as marine worm burrows and arthropod 

feeding traces are locally common in all Paleozoic rock types, 

although in the Potosi Dolomite they are relatively rarer, being 

obscured by more extreme recrystallization of the rock fabric 

in that unit (Bridge, 1930; Lowell and others, 2010).

Invertebrate macrofossils are relatively rare in the 

Paleozoic rocks of the ONSR. The depositional environments 

for most of the units were probably somewhat hypersaline and 

with restricted circulation, and were not conducive for diverse 

faunas. In addition, pervasive dolomitization has obscured 

much of the shelly record that did exist. Mollusks are the 

most abundant and diverse of these macrofossils. Trilobites 

are known from relatively few intervals; and brachiopods 

have been very useful in some of the Cambrian units. Most 

of these faunas were described in a very few works in the 

1930s, 1940s, and 1950s. Occasional beds in the Gasconade 

Dolomite and the Roubidoux Formation yield molds and casts 

of gastropods and trilobite fragments (Harrison and others, 

1996; Heller, 1954).

Residual chert and quartz sandstone cobbles in the larger 

streams and in high-level terrace deposits occasionally contain 

crinoids and brachiopods of Mississippian age. These cobbles 

are derived from Mississippian units that once lay over the 

Ordovician rocks exposed in the ONSR, but have been largely 

removed by weathering and erosion (Unklesbay and Vineyard, 

1992).

Conodont microfossils have been recovered and provide 

age control for the Eminence and Gasconade Dolomites, 

the Roubidoux Formation, and the Jefferson City Dolomite 

(Kurtz, 1981; Repetski and others, 1998; Repetski and others, 

2000a, 2000b).

Geologic Resources

Potential geologic resources in the ONSR and adjacent 

areas include dimension stone, aggregate, and gravel. 

Decorative stone was once quarried from a granite body 

exposed just to the north of Big Spring, in an operation that 

took advantage of the easy transport provided by a nowabandoned narrow-gauge railroad.

Significant Mississippi Valley-type base-metal deposits, 

predominantly lead and zinc minerals hosted in the subsurface 

Bonneterre Formation, are known to exist near the ONSR. 

The closest reported occurrences are (1) below the Blair Creek 

drainage, a tributary of the Current River about 12 mi (19 

km) northeast of the town of Eminence (fig. 1) (Kisvarsanyi, 

1977); and (2) an area beneath the small drainages of Becky 

Hollow, Mine Hollow, McCormack Hollow, and Threemile 
12 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

Hollow, about 21 mi (34 km) south of the town of Eminence 

(fig. 1). These drainages are tributaries of the Eleven Point 

River, located south of the map area. See Weary and others 

(2014) for further discussion of these deposits.

Small, low-grade deposits of iron and manganese occur 

sporadically across the region (Crane, 1910; Grawe, 1943).

References Cited

Baker, H.W., 1999a, Bedrock geologic map of the Grandin 

SW 7.5-minute quadrangle: Missouri Geological Survey 

Map OFM-99-342-GS, 1 sheet, scale 1:24,000.

Baker, H.W., 1999b, Surficial material geologic map of the 

Grandin SW 7.5-minute quadrangle: Missouri Geological 

Survey Map OFM-99-343-GS, 1 sheet, scale 1:24,000.

Bickford, M.E., Harrower, K.L., Hoppe, W.J., Nelson, 

B.K., Nusbaum, R.L., and Thomas, J.J., 1981, Rb-Sr and 

U-Pb geochronology and distribution of rock types in the 

Precambrian basement of Missouri and Kansas: Geological 

Society of America Bulletin, v. 92, p. 323–341.

Bridge, Josiah, 1930, Geology of the Eminence and Cardareva 

quadrangles: Missouri Geological Survey [Reports], 2d 

Series, v. 24, 228 p., 3 pls. in pocket, scale 1:62,500.

Clendenin, C.W., Lowell, G.R., and Niewendorp, C.A., 1993, 

Sequencing Reelfoot extension based on relations from 

southeast Missouri and interpretations of the interplay 

between offset preexisting zones of weakness: Tectonics, 

v. 12, no. 3, p. 703–712.

Clendenin, C.W., Niewendorp, C.A., and Lowell, G.R., 1989, 

Reinterpretation of faulting in southeast Missouri: Geology, 

v. 17, p. 217–220.

Cox, R.T., 2009, Ouachita, Appalachian, and ancestral Rockies 

deformations recorded in mesoscale structures on the 

foreland Ozark plateaus: Tectonophysics, v. 474, no. 3-4, 

p. 674–683.

Craig, L.C., and Connor, C.W., coordinators, 1979, 

Paleotectonic investigations of the Mississippian System 

in the United States, Part III: U.S. Geological Survey 

Professional Paper 1010, pls. 1–15.

Crane, G.W., 1910, The iron ores of Missouri: Missouri 

Geological Survey [Reports], 2d Series, v. 10, 434 p.

Fisher, H.H., 1969, Stratigraphy and correlation of 

Precambrian volcanic rocks, Eminence (Shannon County), 

Missouri: Rolla, Mo., University of Missouri-Rolla, 

unpublished M.S. thesis, 77 p.

Grawe, O.R., 1943, Manganese deposits of Missouri: Missouri 

Geological Survey and Water Resources, 62d Biennial 

Report, Appendix 6, 77 p.

Harrison, R.W., Lowell, G.R., and Unruh, D.M., 2000, 

Geology, geochemistry, and age of Mesoproterozoic 

igneous rocks in the Eminence-Van Buren area: a major 

structural outlier of the St. Francois terrane, south-central 

Missouri [abs.]: Geological Society of America Abstracts 

with Programs, v. 32, no. 3, p. A–14.

Harrison, R.W., Orndorff, R.C., and Weems, R.E., 1996, 

Geology of the Fort Leonard Wood Military Reservation 

and adjacent areas, south-centralMissouri: U.S. Geological 

Survey Open-File Report 96‒60, 255 p., 10 pls. in pocket, 

scales vary.

Harrison, R.W., Orndorff, R.C., and Weary, D.J., 2002, 

Geology of the Stegall Mountain 7.5-minute quadrangle, 

Shannon and Carter Counties, south-central Missouri: U.S. 

Geological Survey Geologic Investigations Series Map 

I–2767, scale 1:24,000, http://pubs.usgs.gov/imap/i2767/.

Harrison, R.W., and Schultz, A.P., 2002, Tectonic framework 

of the southwestern margin of the Illinois basin and its 

influence on neotectonism and seismicity: Seismological 

Research Letters, v. 73, issue 75, p. 685–718.

Heller, R.L., 1954, Stratigraphy and paleontology of the 

Roubidoux Formation of Missouri: Missouri Geological 

Survey and Water Resources [Reports], 2d Series, v. 35, 

118 p., 2 pls. in pocket.

Hudson, M.R., 2000, Coordinated strike-slip and normal 

faulting in the southern Ozark dome of northern Arkansas; 

deformation in a late Paleozoic foreland: Geology, v. 28, 

no. 6, p. 511–514.

Kisvarsanyi, E.B., 1974, Operation basement; buried 

Precambrian rocks of Missouri; their petrology and 

structure: American Association of Petroleum Geologists 

Bulletin, v. 58, no. 4, p. 674–684.

Kisvarsanyi, E.B., 1981, Geology of the Precambrian St. 

Francois terrane, southeastern Missouri (Contribution to 

Precambrian Geology 8): Missouri Geological Survey 

Report of Investigations 64, 58 p.

Kisvarsanyi, E.B., 1984, The Precambrian tectonic framework 

of Missouri as interpreted from the magnetic anomaly map: 

Missouri Geological Survey, Contribution to Precambrian 

Geology 14, part B, 19 p.

Kisvarsanyi, Geza, 1977, The role of the Precambrian igneous 

basement in the formation of the stratabound lead-zinccopper deposits in southeast Missouri: Economic Geology, 

v. 72, no. 3, p. 435–442.
References Cited 13

Kisvarsanyi, Geza, and Kisvarsanyi, E.B., 1976, Orthopolygonal tectonic patterns in the exposed and buried 

Precambrian basement of southeast Missouri, in Hodgson, 

R.A., ed., Proceedings of the 1st International Conference on 

the New Basement Tectonics: Utah Geological Association 

Publication 5, p. 169–182.

Kurtz, V.E., 1981, The Cambrian-Ordovician boundary in 

Missouri as determined by conodonts, in Taylor, M.E., ed., 

Short papers for the Second International Symposium on the 

Cambrian System, 1981: U.S. Geological Survey Open-File 

Report 81‒743, p, 115‒117.

Lowell, G.R., 2000, Eruptive styles of Mesoproterozoic 

A-type calderas in southeastern Missouri, U.S.A: Revista 

Brasileira de Geociências, v. 30, no. 4, p. 745–748.

Lowell, G.R., Harrison, R.W., Weary, D.J., Orndorff, R.C., 

Repetski, J.E., and Pierce, H.A., 2010, Rift-related 

volcanism and karst geohydrology of the southern 

Ozark dome, in Evans, K.R., and Aber, J.S., eds., From 

Precambrian rift volcanoes to the Mississippian shelf 

margin; geological field excursions in the Ozark Mountains: 

Geological Society of America Field Guide 17, p. 99–158. 

Digital Object Identifier: 10.1130/2010.0017(06).

McCracken, M.H., 1971, Structural features of Missouri: 

Missouri Geological Survey and Water Resources Report of 

Investigations 49, 99 p.

McDowell, R.C., and Harrison, R.W., 2000, Geologic map of 

the Powder Mill Ferry quadrangle, Shannon and Reynolds 

Counties, Missouri: U.S. Geological Survey Geologic 

Investigations Series Map I–2722, scale 1:24,000, http://

pubs.usgs.gov/imap/i-2722/.

Orndorff, R.C., and Harrison, R.W., 2001, Geologic map of 

the Winona quadrangle, Shannon County, Missouri: U.S. 

Geological Survey Geologic Investigations Series Map 

I–2749, scale 1:24,000, http://pubs.er.usgs.gov/publication/

i2749.

Orndorff, R.C., Harrison, R.W., and Weary, D.J., 1999, 

Geologic map of the Eminence quadrangle, Shannon 

County, Missouri: U.S. Geological Survey Geologic 

Investigations Series Map I–2653, scale 1:24,000, http://

pubs.usgs.gov/imap/i-2653/.

Orndorff, R.C., and Weary, D.J., 2009, Geologic map of the 

Round Spring quadrangle, Shannon County, Missouri: U.S. 

Geological Survey Scientific Investigations Map 3073, scale 

1:24,000, http://pubs.usgs.gov/sim/3073/.

Repetski, J.E., Loch, J.D., and Ethington, R.L., 1998, 

Conodonts and biostratigraphy of the Lower Ordovician 

Roubidoux Formation in and near the Ozark National 

Scenic Riverways, southeastern Missouri, in Santucci, 

V.L., and McClelland, Lindsay, eds., National Park Service 

Paleontological Research: National Park Service, Geologic 

Resources Division, Technical Report NPS/NRGRD/

GRDTR-98/01, p. 109–115.

Repetski, J.E., Loch, J.D., Ethington, R.L., and Dresbach, R.I., 

2000a: A preliminary re-evaluation of the stratigraphy of the 

Roubidoux Formation of Missouri and correlative Lower 

Ordovician units in the southern Midcontinent, in Johnson, 

K.S., ed., Platform carbonates in the southern Midcontinent, 

1996 Symposium: Oklahoma Geological Survey Circular 

101, p. 103–106.

Repetski, J.E., Orndorff, R.C., Weary, D.J., and Ethington, 

R.L., 2000b, Conodont bistratigraphy of the Eminence 

Dolomite-Gasconade Dolomite contact interval in the 

Missouri Ozarks [abs.]: Geological Society of America 

Abstracts with Programs, v. 32, no. 3, p. A-39‒A-40.

Sims, P.K., 1990, Precambrian basement map of the 

northern midcontinent, U.S.A: U.S. Geological Survey 

Miscellaneous Investigations Series Map I–1853–A, 

1 sheet, scale 1:1,000,000.

Sinha, B.N., and Kisvarsanyi, Geza, 1976, Precambrian 

volcanic rocks exposed on Stegall and Mule Mountains, 

Carter and Shannon Counties, Missouri, in Kisvarsanyi, 

E.B., ed., Studies in Precambrian geology of Missouri 

(Contribution to Precambrian Geology 6): Missouri 

Geological Survey Report of Investigations 61, p. 114–121.

Thompson, T.L., 1995, The stratigraphic succession in 

Missouri: Missouri Department of Natural Resources, 

Division of Geology and Land Survey, v. 40, 2d Series, 

revised, 190 p.

Tolman, C.F., and Robertson, F., 1969, Exposed Precambrian 

rocks in southeast Missouri (Contributions to Precambrian 

Geology 1): Missouri Geological Survey and Water 

Resources Report of Investigations 44, 68 p.

Unklesbay, A.G., and Vineyard, J.D., 1992, Missouri geology; 

three billion years of volcanoes, seas, sediments, and 

erosion: Columbia, University of Missouri Press, 189 p., 

9 pls.

Van Schmus, W.R., Bickford, M.E., Sims, P.K., Anderson, 

R.R., Shearer, C.K., and Treves, S.B., 1993, Proterozoic 

geology of the western midcontinent basement, in Reed, 

J.C., Jr., and others, eds., Precambrian: Conterminous U.S., 

v. C-2 of The Geology of North America: Boulder, Colo., 

Geological Society of America, p. 239–259.
14 Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas

Weary, D.J., 2008, Geologic map of the Cedargrove 

quadrangle, Dent and Shannon Counties, Missouri: U.S. 

Geological Survey Scientific Investigations Map 2980, scale 

1:24,000, http://pubs.usgs.gov/sim/2980/.

Weary, D.J., 2015, Geologic map of the Montauk quadrangle, 

Dent, Texas, and Shannon Counties, Missouri: U.S. 

Geological Survey Scientific Investigations Map 3320, scale 

1:24,000, http://dx.doi.org/10.3133/sim3320.

Weary, D.J., Harrison, R.W., Orndorff, R.C., Weems, R.E., 

Schindler, J.S., Repetski, J.E., and Pierce, H.A., 2014, 

Bedrock geologic map of the Spring Valley, West Plains, 

and parts of the Piedmont and Poplar Bluff 30′×60′ 

quadrangles, Missouri, including the upper Current River 

and Eleven Point River drainage basins: U.S. Geological 

Survey Scientific Investigations Map 3280, 2 sheets, scale 

1:100,000, and 55-p. pamphlet, http://dx.doi.org/10.3133/

sim3280.

Weary, D.J., and McDowell, R.C., 2006, Geologic map of 

the Big Spring quadrangle, Carter County, Missouri: U.S. 

Geological Survey Scientific Investigations Map 2804, scale 

1:24,000, http://pubs.usgs.gov/sim/2006/2804/.

Weary, D.J., and Orndorff, R.C., 2012, Geologic map of the 

Alley Spring quadrangle, Shannon County, Missouri: U.S. 

Geological Survey Scientific Investigations Map 3161, scale 

1:24,000, http://pubs.usgs.gov/sim/3161/.

Weary, D.J., Orndorff, R.C., Harrison, R.W., and Weems, R.E., 

2016, Digital geologic map data for the Ozark National 

Scenic Riverways and adjacent areas along the Current 

River and Jacks Fork, Missouri: U.S. Geological Survey 

data release, http://dx.doi.org/10.5066/F7CJ8BKB.

Weary, D.J., Orndorff, R.C., and Repetski, J.E., 2013, 

Geologic map of the Jam Up Cave and Pine Crest 

quadrangles, Shannon, Texas, and Howell Counties, 

Missouri: U.S. Geological Survey Scientific Investigations 

Map 3248, scale 1:24,000, http://pubs.usgs.gov/sim/3248/.

Weary, D.J., and Schindler, J.S., 2004, Geologic map of the 

Van Buren South quadrangle, Carter County, Missouri: U.S. 

Geological Survey Geologic Investigations Series Map 

2803, scale 1:24,000, http://pubs.usgs.gov/imap/i2803/.

Weary, D.J., and Weems, R.E., 2004, Geologic map of the Van 

Buren North quadrangle, Carter, Reynolds, and Shannon 

Counties, Missouri: U.S. Geological Survey Geologic 

Investigations Series Map 2802, scale 1:24,000, http://pubs.

usgs.gov/imap/i2802/.

Weary and others—Digital Geologic Map Data for the Ozark National Scenic Riverways and Adjacent Areas—Data Series 1017

ISSN 2327-638X (online)

http://dx.doi.org/10.3133/ds1017