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THE MIDCONTINENT EXPOSED: PRECAMBRIAN BASEMENT
TOPOGRAPHY, AND FAULT-AND-FOLD ZONES, WITHIN
THE CRATONIC PLATFORM OF THE UNITED STATES
BY
STEFANIE L. DOMROIS
THESIS
Submitted in partial fulfillment of the requirements
for the degree of Master of Science in Geology
in the Graduate College of the
University of Illinois at Urbana-Champaign, 2013
Urbana, Illinois
Adviser:
Professor Stephen Marshak
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ABSTRACT ______________________________________________________________________________
The Midcontinent region of the United States is part of the cratonic platform of the North
American craton. This region is underlain by Precambrian basement formed dominantly during
Proterozoic accretionary orogenies. It was modified by Proterozoic anorogenic felsic
magmatism and was cracked by several episodes of rifting. Subsequently, when North America
was part of a supercontinent, the region underwent extensive Late Precambrian erosion and
exhumation. Marine transgressions during the Phanerozoic buried the region with sequences
Phanerozoic sedimentary strata. The continent-wide contact between Precambrian crystalline
rock and the overlying cover of Phanerozoic strata is known as the "Great Unconformity."
Though the cratonic platform has been relatively stable, tectonically, for over a billion
years, it has been affected by epeirogenic movements that produced regional-scale basins, domes
and arches. Also, faults within the region have been reactivated, displacing crustal blocks and
warping overlying strata into monoclinal folds—these faults may be relicts of Proterozoic rifting.
How can this Phanerozoic tectonism be represented visually in a way that can provide a basis for
interpreting new lithospheric features being revealed by EarthScope's USArray seismic network?
In the Appalachian and Cordilleran orogens, ground-surface topography provides insight into the
character and distribution of tectonic activity, because topography is structurally controlled. This
is not the case in the Midcontinent, a region of broad plains where surface topography does not
reflect the structure beneath. Fortunately, the Great Unconformity makes an excellent marker
horizon for mapping intracratonic structures.
In order to create an intuitive visual image of the basement topography and of fault-and-
fold distribution in the cratonic platform of the United States, I constructed two maps of the
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region using ArcGIS software. My study area extends from the Wasatch front on the west to the
Appalachian front on the east, and from the Ouachita front and Gulf coastal plain on the south to
the southern edge of the Canadian Shield on the north. The first map portrays the top of the
Precambrian basement surface in shaded relief, and the second map portrays the distribution of
major faults and folds within the region. Production of the maps required compiling and
digitizing a variety of data, which was imported into ArcGIS and processed to produce a 3-D
surface. The shaded-relief map provides new insight into the crustal architecture of the cratonic
platform, by visually emphasizing that the region consists of distinct provinces: the Midcontinent
Sector (a broad area of low relief, locally broken by steep faults); the Rocky Mountain Sector
(with structural relief of up to 10 km, and relatively short distances between uplifts), the
Colorado Plateau Sector (a moderate-relief area containing fault-bounded crustal blocks), and the
Bordering Basins Sector (deep rift basins, linked at crustal bridges, and locally amplified by
flexural loading). Overlaying the fault map and a map of earthquake epicenters over the shaded
relief map emphasizes that seismicity is concentrated in the bordering basins, particularly where
steep gradients in basement topography coincide with major faults.
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ACKNOWLEDGEMENTS ______________________________________________________________________________
First of all, I would like to express my warmest gratitude to my adviser, Prof. Stephen
Marshak, for his guidance and support throughout the research, and for his editing of the
manuscript. I would have never completed the ArcGIS maps without the expertise of Curt Abert
at the Illinois State Geological Survey. Tim Larsen of the Illinois State Geological Survey also
provided valuable criticism of my presentation and maps. Hersh Gilbert, Michael Hamburger,
Gary Pavlis, and the others from the EarthScope team helped to make my research possible, and
I extend my heartfelt thanks to them. Partial funding for this research was provided by NSF
grant EAR 10-53551, through the EarthScope 'OIINK' project. Additional funding was provided
by the College of Liberal Arts & Sciences of the University of Illinois.
My research would have never been completed without help from University of Illinois
library staff, especially from Jenny Johnson and Jim Cotter from the Map and Geography
Library and Mary Schlembach and Lura Joseph from the Geology Department Library. I would
also like to thank the following people for their help in providing me the necessary maps and
literature for my research: Julie Chang (Oklahoma Geological Survey), Sigrid Clift (University
of Texas Bureau of Economic Geology), Ray Anderson and Bob McKay (Iowa Geological
Survey), Tom Evans and Linda Deith (Wisconsin Geological and Natural History Survey), Ranie
Lynds (Wyoming State Geological Survey), Dale Bird (for the USGS basement maps), and
others. I greatly appreciate the moral support and friendship with my two Structural Geology
office mates: Stephanie Mager and Pragnyadipta (Deep) Sen, and the other graduate and
undergraduate students at the University of Illinois. Lastly, I thank my parents and extended
family, who always encourage me to achieve my goals in life.
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TABLE OF CONTENTS
______________________________________________________________________________
CHAPTER 1: Introduction…………………………………………………………………1
CHAPTER 2: Methodology……………………………………………………………….10
CHAPTER 3: Observations………………………………………………………………..55
CHAPTER 4: Discussion and Conclusions………………………………………………..65
REFERENCES …………………………………………………………………………….73
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— CHAPTER 1 —
INTRODUCTION ______________________________________________________________________________
1.1 Geology of the Cratonic Platform of the United States
The craton of North America includes the Canadian Shield, where Precambrian igneous
and metamorphic rocks are exposed at the surface, and the cratonic platform, where Precambrian
igneous and metamorphic rocks (basement) are buried beneath Phanerozoic sedimentary strata
(cover). The thickness of sedimentary strata range from 0 km (where basement is exposed) to
over 7.5 km. North America’s cratonic platform extends from the Wasatch Front in the west to
the Appalachian front in the east, and from the Ouachita front and Gulf coastal plain in the south
to the southern edge of the Canadian Shield in the north (Fig. 1.1). Between the Wasatch front
and the Rocky Mountain front, the cratonic platform has been uplifted and deformed by
Mesozoic and Cenozoic faulting and folding, and now comprises the Rocky Mountains (to the
north) and the Colorado Plateau (to the south). East of the Rocky Mountain front, the cratonic
platform forms a broad region of low relief, known as the Great Plains or the Midcontinent. The
region outside of the cratonic platform includes the Appalachian, Ouachita, and Cordilleran
orogens, and the Atlantic and Gulf coastal plains.
In the Midcontinent, the only exposure of Precambrian basement south of the Canadian
Shield occurs in the St. Francis Mountains of the Ozark Plateau in eastern Missouri, in the
Adirondack Dome of northeastern New York, and in isolated exposures of exhumed
Precambrian islands in Wisconsin and Minnesota. Surface exposures of the Phanerozoic cover,
west of a longitude of about 97°W, consist dominantly of Mesozoic and Cenozoic strata. East of
this longitude line, surface exposures consist of Paleozoic strata. Variations in thickness of
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Phanerozoic strata define broad basins, domes, and arches; these structures formed by
epeirogenic uplift and subsidence during the Paleozoic. The major intracratonic basins of the
Midcontinent are the Michigan basin, the Illinois basin, and the Williston basin. Locally, strata
of the Midcontinent have been warped into monoclinal folds and/or have been cut by localized
high-angle faults.
The basement of the North American craton assembled during the Proterozoic (Fig. 1.2).
According to the synthesis by Whitmeyer and Karlstrom (2007), the earliest stage of craton
assembly involved growth of several Archean lithospheric blocks. These Archean nuclei sutured
together during the Paleoproterozoic (2.0 to 1.8 Ga). Later in the Proterozoic, progressively
younger terranes accreted to the outer edges of the Paleoproterozoic continent, forming two
distinct accretionary orogenic belts that have a general northeast trend. The older of this, which
fringes the Archean cratonic nucleus, is the Yavapai terrane, which was accreted between 1.71
and 1.69 Ga. The Mazatzal terrane accreted to the edge of the Yavapai between 1.65-1.60 Ga.
Subsequently, intracratonic magmatism between 1.5 and 1.3 Ga produced anorogenic granites
and rhyolites; the region affected by this magmatism is known as the Granite-Rhyolite Province.
Rocks of the Llano-Grenville province attached to North America during the Grenville orogeny
(1.3 and 0.9 Ga). By the end of the Grenville orogeny, North America lay in the interior of a
large supercontinent, Rodinia, which broke apart and reassembled as Pannotia. Pannotia
survived until the end of the Precambrian, when it broke apart leaving Midcontinent North
America as part of Laurentia.
Rifting occurred at several times during the Precambrian, and produced distinct, narrow
rift basins filled with sediments, and in some cases, volcanics. The largest rift is the 1.1 Ga
Midcontinent Rift System, consisting of one arm of which cuts NW from Kansas across Iowa to
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Lake Superior, and another arm which cuts SE across Michigan. Other, younger rifts associated
with the breakup of the late Precambrian supercontinent include the Oklahoma aulacogen, the
Reelfoot Rift and the Rome Trough (e.g., Whitmeyer and Karlstrom, 2007; Marshak et al.,
2003). Extensional tectonism led to widespread intrusion of dikes and normal faulting, even in
areas outside of the particularly distinctive rifts.
While in the interior of the supercontinent, North America was emergent, and thus its
surface was eroded and rocks that had been kilometers below the surface were exhumed. This
erosion may have stripped away the fill of smaller rifts, though the associated basement-
penetrating normal faults still remained. Though the craton of North America’s Midcontinent
has been relatively tectonically stable and unmetamorphosed for the past 1 billion years, it has
not been totally inactive. Rather, structures within it have undergone pulses of reactivation that
are roughly coeval with Paleozoic orogenic events in the Appalachian/Ouachita orogens. During
these events, domes and arches have gone up, basins have undergone subsidence pulses, and
faults have been reactivated (Marshak and Paulsen, 1997). At the end of the Paleozoic, hot
brines migrated though the sedimentary basins causing mineralization, anthracitization, and
dolomitization (Bethke and Marshak, 1990).
1.2 Statement of Purpose
Topography can be used as a tool for identifying and characterizing tectonic features, for
the geologic structures they yield can control the shape of landforms directly and/or can control
erosion over time, so that the shapes of structures stand out in the landscape. Digital Elevation
Maps (DEMs) increasingly have been used to study landforms, for by using shading to simulate
shadows cast by the Sun, they can convey a sense of the 3-D shape of the land surface. The
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1:3,500,000-scale DEM map, Landforms of the Conterminous United States (Thelin and Pike,
1991) serves as an example. This map portrays topography in shaded relief by varying tints of
gray. More recent versions of this map add colors (usually a palette ranging from green through
tan, to white) to add visual information about relative elevation. A shaded-relief DEM can
clearly show tectonically controlled textures of the terrain, if the map has sufficient resolution.
For example, on Thelin and Pike's map, the Valley and Ridge Province in the Northern
Appalachians stands out and its morphology allows interpretation of the wavelength and
amplitude of the underlying folds and even inference of principle stress directions at the time the
folds formed (Fig. 1.3). Similarly, the distribution and orientation of Laramide basement-cored
uplifts in the United States can be delineated by the morphology of the Rocky Mountains, and
the area and extension direction of Cenozoic rifting in the Cordillera is indicated by the
topographic characteristics of the Basin and Range Province.
Geologic maps can provide additional perspective on continent-scale tectonic features.
For example, one can identify continental-interior basin or domes based on the bulls-eye pattern
of stratigraphic units—in a dome, older units crop out in the center, whereas in a basin, younger
units crop out in a center. The Tapestry of Time and Terrain map, published by the United States
Geological Survey in 2000, combines a DEM and the geologic map of King and Beikman (1974)
to emphasize the relationships between bedrock distribution and landforms. Notably, however,
in the Midcontinent, the landforms are largely independent of the distribution of geologic
formations. Tectonic maps (e.g., P.B. King's 1969 Tectonic Map of North America, and W.
Muehlberger's 1992 Tectonic Map of North America) provide further insight grouping geologic
map units according to their tectonic meaning and by including contours on the top of the
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Precambrian, but these maps include many types of data that create a clutter that makes it hard,
in some cases, to focus on basement data, and they do not show features in shaded relief.
Digital elevation maps, geologic maps, and existing tectonic maps do not provide a clear
picture of tectonic movements across the Midcontinent. Specifically, DEMs of the Midcontinent
display primarily plains, locally incised by Cenozoic drainage or covered by Cenozoic fans and
glacial deposits, so intracratonic domes and basins, with few exceptions (e.g., the Ozark Plateau)
do not control the details of landscape features. In other words, they do not provide insight into
the aerial extent of upwarped or downwarped crust resulting from epeirogenic movements.
Similarly, while geologic and tectonic maps clearly outline epeirogenic structures and display the
surface manifestation of faults in the Midcontinent, they do not provide direct insight into the
magnitudes of differential vertical movements.
How, then, can the tectonic character of the Midcontinent be portrayed on a map to give a
clear visual impression of differential movements, localization of deformation, and the role that
Precambrian tectonic features have played in controlling Phanerozoic structure? To address this
question, I have developed two digital maps of the Midcontinent region that display the tectonic
character of the Midcontinent visually. The first map is a shaded-relief map of the depth to the
Precambrian surface. The map was first produced as a 2-D image, but with additional processing
it can be converted into a 3-D surface that provides an excellent visual tool for interpreting
structures (both surface and subsurface). The second map shows the distribution of major faults
and folds in the region. I provide examples of how my new maps can be merged with other
digital data sets (e.g., distribution of seismicity; geophysical potential field; crustal and mantle
tomography) to provide a basis for interpreting relationships among lithospheric features and to
provide insight into how pre-existing crustal structures in the cratonic platform.
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1.3 Strategy and Organization of this Thesis
In this thesis, I first present a brief outline of published maps that show the depth to the
Precambrian basement within the study area. I will then discuss the reasons why I chose the
depth to the Great Unconformity (the Precambrian/cover contact) as a marker horizon for my
maps. Following these two sections, I provide greater detail on the procedure of constructing my
maps. In the procedure section, I outline how I acquired the data necessary for developing the
maps, and then show how I constructed both the 2-D and 3-D versions of the shaded relief map.
Section 2.4 illustrates how I produced the map of faults and folds, and of other features discussed
in this thesis.
My next chapter (Chapter 3) incorporates observations for both maps. I will first discuss
visual observations based on examination of the shaded-relief map, and show how different
tectonic domains of the Midcontinent can be delineated based on the morphology of the Great
Unconformity surface. Next, I provide observations on the different structures within the study
area, and introduce the data spreadsheet that I developed for analyzing these structures.
Following this section, I discuss the dominant trends of Midcontinent structures. The final
chapter (Chapter 4) provides the discussion and conclusions of this thesis, with a focus on the
relationships among basement topography, structure, and seismicity.
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Figure 1.1: Visual of the study area (area not in color), including the cratonic platform and the
Colorado Plateau.
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Figure 1.2: Precambrian tectonic assembly map of North America (Whitmeyer and Karlstrom
2007).
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Figure 1.3: Digital Elevation Map of the United States, showing sample topographic provinces
(Thelin and Pike, 1991).
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— CHAPTER 2 —
METHODOLOGY ______________________________________________________________________________
2.1 Previous Precambrian Basement Maps
The first step of my research involved determining what maps are already available that
characterized Midcontinent tectonic features. There have been many attempts to portray the role
of the Precambrian basement surface in influencing later Phanerozoic tectonics. Two of the
earliest maps produced of the Precambrian basement are the 1:5,000,000-scale Basement Map of
North America, published by the American Association of Petroleum Geologists and the USGS
in 1967, and the 1:2,500,000-scale Basement Rock Map of the United States by Bayley and
Muehlberger (1968). Both maps provide a generalized interpretation of the Precambrian
basement surface. On the Basement Rock Map of the United States, the different Precambrian
rock types are clearly emphasized, and while depth to the top of the Precambrian data are
indicated by hard-to-see contour lines. Major faults that are expressed at the surface are also
drawn and labeled in some cases, but major subsurface faults are not shown due to the lack of
seismic-reflection data available at the time the map was produced.
The Generalized Tectonic Map of North America by King and Edmonston (1972)
provides a very simplified contour map of the top-of-Precambrian surface. Major basins are
clearly visible, but the map is generalized and doesn't offer any data that was not already shown
by the Basement Rock Map of the United States. Muehlberger et al.'s (1992) Tectonic Map of
North America, published by the American Association of Petroleum Geologists, provides an
update of the Basement Rock Map of the United States. Muehlberger et al.'s map (actually, a
series of 4 plates) shows significantly more detail than earlier versions of tectonic maps of North
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America. The contours on the Precambrian surface are better constrained as they utilize
additional data from seismic-reflection profiles and new drilling data. The map not only shows
more faults, but the depiction of the faults clearly shows how they offset the structural contours
on the Precambrian surface. The colors and shades of colors used on the map also make the
major basins stand out.
The Precambrian Basement Structure Map of the Continental United States by Sims et
al. (2008) is one of the most current maps of major structures within the Precambrian basement.
This map uses an interpretation of magnetic anomaly maps to delineate major structures such as
suture zones and large, continental-scale faults. Sims and others (2008) emphasizes that most of
the major structures have been reactivated when stress fields within the region changed. The
suture zones and other large faults within the region behave as zones of weakness within the
Precambrian basement. Sims et al.'s map does not, however, display contours on top of the
Precambrian basement.
Maps portraying one state, or several adjacent states, have been prepared for portions of
the cratonic platform, and these reveal the local form of the Precambrian top surface in greater
detail. Most of these maps are based on well data, though some also include evidence from
seismic-reflection profiles. Faults shown on these maps are based on stratigraphic separations,
vertical displacements of seismic reflectors, or Bouguer gravity or magnetic anomaly maps.
Examples of state-scale maps (maps showing contours on top of the Precambrian basement in
one state) are the Configuration of the Top of Precambrian Rocks in Kansas by Cole (1978) and
the Precambrian Structure Map of North Dakota by Heck (1988). In these two maps (and maps
similar to these for other states), the contours and faults stop abruptly at the state boundaries.
Examples of regional basement-surface maps include the Precambrian Basement Map of the
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Northern Midcontinent, USA by Sims (1990), and the Precambrian Basement Map of the Trans-
Hudson Orogen, USA by Sims et al. (1992). Both maps illustrate faults and contours on the
Precambrian top surface in detail but, like many state-scale maps, do not show the regional
associations of the Precambrian surface across the Midcontinent, and do not cleanly link to maps
of adjacent states. Notably, most state-scale maps are decades old, and have not been updated to
a digital form.
2.2 Identifying a Marker Horizon
The top of the Precambrian surface is marked by a continent-wide unconformity—known
as the Great Unconformity—that formed due to extensive erosion during the Late Precambrian,
prior to the deposition of Paleozoic strata (Peters and Gaines, 2012). The Great Unconformity is
exposed at the Earth’s surface in at many locations along the edges of basement-cored uplifts in
the Rocky Mountains, as well as at the top of the inner gorge in the Grand Canyon and at the top
of the gorge in Black Canyon of the Gunnison. In the Midcontinent, it is almost completely
covered except at localities along the boundary between the Canadian Shield and the continental-
interior platform in Minnesota and Wisconsin. South of the Canadian Shield, the unconformity
is exposed at only a few localities, such as the Baraboo Syncline, in southern Wisconsin, and the
St. Francis Mountains in eastern Missouri. Elsewhere, the Great Unconformity exists tens of
meters to more than several thousand meters below the Earth’s surface, and has been sampled
only in drill holes.
The Great Unconformity is an excellent marker horizon for characterizing intracratonic
tectonic features (basins, domes, and faults), for it exists everywhere in the Midcontinent, can be
recognized definitively on seismic profiles and in drill cores, and has not been affected by
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surface erosion since the Late Precambrian. Further, all geologists tend to interpret the surface in
the same way, so there isn't uncertainty in correlating the surface across the Midcontinent—
younger stratigraphic features, in contrast, may be interpreted differently by different authors.
The depth to the unconformity can also be referred to as "depth to basement" or "depth to the
cover/basement contact," or "depth to the top of the Precambrian."
2.3 Data Acquisition for the Shaded Relief Map
Data for the shaded relief map was primarily acquired by a basic literature research on
the internet and through on-line reference systems, such as GeoRef, available through the
University of Illinois Library. Maps showing structure contours on the Precambrian basement
were mostly found as images on the internet through state geological survey websites. In some
states, contour data representing the shape of the Precambrian surface were already available in
downloadable packages. I called many state geological surveys directly to acquire information
that was not available on the internet or through the library system. I also contacted libraries at
other universities, as well as individuals on the faculty of other universities, throughout the
country to try to obtain additional information. Maps that were not in a digital format were
scanned on a large-format scanner at the Illinois State Geological Survey. However, a couple of
maps were either in too poor condition to be scanned (meaning that the map had too many
creases, or ripped easily) or only a small area needed to be scanned, so a smaller scanner was put
into use. To obtain data in areas for which existing structural contour maps were not available, I
used either drillhole data, which was added as point data to my data base, or point data extracted
from published cross sections.
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Cross sections were of particular use to constrain depth to basement along the southern
and eastern borders of my map area, where the basement and its platformal cover were
overlapped by thrust faults in the foreland of the Appalachian/Ouachita orogen. To obtain this
data I pasted a scan of the cross section into Adobe Illustrator, and then set up a vertical scale,
which I scrolled across the section, measuring depth to basement at regular intervals. I stopped
data acquisition at the forelandward-most fault that thrust basement up over Phanerozoic cover. I
also marked the location of points where basement-penetrating faults intersected the line of
section. Finally, I plotted the strings of resulting point data on a map, hand-contoured the data,
and then transferred the resulting map into the digital data base.
2.4 Production of the Shaded-Relief Map
I used ArcGIS, a software product produced by ESRI (www.esri.com), for creating the
maps described in this thesis. This work was done under the supervision of Curt Abert, and
utilized the facilities of the GIS laboratory of the Illinois State Geological Survey. ArcGIS can
be used to geo-reference spatial data sets, and to draw the results in both 2-D (ArcMap) and 3-D
(ArcScene). A map showing the outline of the states within the conterminous United States
provided serves as the "base map" on which I projected my depth-to-basement and structural
trace data. The map projection of this base map is NAD 1983, UTM Zone 14N.
Use of Preexisting Digital Maps: The geological surveys of several states (Illinois,
Iowa, Missouri, Kentucky, South Dakota, Indiana, Nebraska, and Ohio) have prepared ArcGIS-
based maps showing depth to basement for the entire state. (The Texas Bureau of Economic
Geology has produced a map for a portion of west Texas, but not for the whole state.) On such
maps, the contour lines are shapes with each point on the line representing a geo-referenced
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point; the data set representing this line is called a “shapefile.” I converted the shapefiles to the
map projection mentioned above and added it as an overlay to the map (Fig. 2.1). Shapefiles for
other areas, including small map areas represented in research publications and/or continent-
scale maps, were also added where available.
Using Archival Non-Digital Maps: The majority of the maps that showed the depth to
the Precambrian surface for the continental interior are available only as a raster image (bitmap)
in the form of a JPEG, TIFF, or PDF file, or as a paper copy that needed to be scanned and
turned into a digital raster image. Regardless of its origin, the raster image or "source map" was
placed as an overlay into ArcMap and was georeferenced by distorting it so it registered as
closely as possible to the base map's orientation and projection (Fig. 2.2a). Specific lines or
points on the source map image that I used to align the image to the base map include state
boundaries, county boundaries, and latitude or longitude lines.
Once the source map was aligned to the base map, I digitized the raster map by "hands-on
digitizing," which involves tracing out contours on the computer by using the computer mouse
(Fig. 2.2b). I first created a new line shapefile and set the projection to the one I used for
producing the maps. I added a contour field to the attribute table so that I could record the depth
to the Precambrian that the line represented. I then overlaid the contour shapefile onto the
georeferenced map and I started an edit session, in which I drew straight-line segments over the
map image for each contour line. For curving lines, I increased the number of vertices, which
are points at the end of each line segment, and the number of line segments, so that the drawn
lines would closely follow the map’s curving contour lines. The above procedure was repeated
numerous times for each source map. If lines were too close to resolve at the scale of the entire
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study area, I queried a contour interval (usually 1000 ft. contour interval) so that individual
contour lines can be visualized.
Unfortunately, my digitizing procedure introduces some error into the map compilation.
Part of this error comes from scanning (for the scanning lenses do not reproduce images exactly),
part comes from stretching and distorting within ArcGIS to fit the source map to the base map
(for the process does not produce a perfect match across the entire area of the map, especially if
the source map was not the same projection as the base map), and part comes from the process of
tracing contour lines (since the inherent inaccuracy of hand motions means that the tracing is not
exact). Also, contour maps, by their nature, are not unique solutions to point data. Effort was
made to keep the amount of error to a minimum, and I estimate that tracings as it appears on the
base map is no more than approximately 500 m off of the "true" tracing on the source map.
Use of Drill-Hole and Cross-Section Data: To constrain depth to basement in areas for
which map data do not exist, I used drill-hole data and/or data extracted from cross sections. To
use drill-hole data, I prepared a spread sheet in Microsoft Excel that contains latitude, longitude,
and depth. This data can be entered directly to the ArcMap document, for ArcGIS software
converts longitude and latitude into X (north-south) and Y (east-west) coordinates, respectively,
and depth into a Z coordinate, which then becomes a shapefile that shows the wells or drill hole
locations as points on the map. To extract depth data from cross sections, I scanned the cross
section to produce a JPEG of the cross section, or obtained an existing JPEG image of the cross
section. I exported the JPEG into Adobe Illustrator as a base layer. Then, I created a new layer
on which I drew a horizontal sea-level reference line as an overlay, and created an accurate
vertical (i.e., depth) scale. I then moved the scale along the sea-level reference line, and
measured the depth to the basement/cover contact (the Great Unconformity) at regular intervals.
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In places where the change in depth was rapid (e.g., at basement-penetrating faults), I added
additional points for extra control. I then produced a map-view image showing the trace of the
cross sections and the points of measurement along it. This trace was then geo-referenced onto
the map document. Next, I extracted the latitude and longitude for each measured point along
the cross section, and entered into a Microsoft Excel document, along with the depth to basement
data for the point. The Excel document was then placed into the ArcMap document and
subsequently made into a point shapefile. Once the depth points were visualized, I hand
contoured the subsequent area, along with adding faults where needed, to produce the
Precambrian surface in that area.
The Trace of Precambrian Outcrop: To depict the trace of the basement/cover contact
(the Great Unconformity or the top of the crystalline Precambrian) where it intersects the ground
surface, I produced a shapefile outlining areas where the Precambrian rocks are the bedrock at
the Earth’s surface. Some of these areas include: Minnesota, Wisconsin, northern Michigan,
northern New York (the Adirondack Mountains), the Blue Ridge and its along-strike equivalents
(the "Blue-Green-Long Axis") in the Appalachians, the basement of the basement-cored uplifts
in the Rocky Mountain region, and the floors of deep canyons in the Colorado Plateau.
Elevation data, which was derived from a 30 arc-second DEM of North America produced by the
U.S. Geological Survey’s Center for Earth Resources Observation and Science, was downloaded
from ArcGIS’ online data repository and exported directly into the ArcMap document. An
‘Extract by Mask’ tool was used to clip the elevation data to fill in the Precambrian outcrop
shapefile. The clipped elevation data was then changed from raster data to point elevation data
using tools in the ArcGIS toolbox. The resulting shapefile was then used to create the
Precambrian surface along with the other contour and point elevation data.
Page 23
18
Data Compilation in ArcGIS: The shapefiles of the depth to the Precambrian surface
contours and points were added to the ArcMap document to create a "primary data contour layer"
for the entire study area. Most of the reference maps provided contours measured in feet, but
some provided contours in meters. The contours provided in meters were converted to feet by
multiplying the number of meters by 3.2808. I also checked to insure that all depths on the map
represented depth below sea level, not depth below the ground surface. I accomplished this task
by conducting a literature search on the source maps, identifying any additional texts provided
by the author of the source map. For source maps with no additional information, I visually
judged the source maps by the contours’ continuity with other surrounding data/source maps that
had more precise information.
Due to inherent errors made during georeferencing, or due to errors on source maps
themselves, contours did not all line up across state boundaries. The non-matching contours
were adjusted by hand on the primary data contour layer so that the contours would be smooth
lines, and would not give the false impression that faults exist at state borders. I also hand
corrected places where contours appeared to cross one another, and hand-adjusted contours along
or near faults, so that they were aligned as closely as possible to the faults. In the ArcMap
document, the contours were actually ‘snapped’ to the fault lines (Fig. 2.3).
Transformation of the Contour Map into the Shaded-Relief Map: Production of the
shaded-relief image of the Precambrian surface required two steps. First, I used the "Topo-to-
Raster" tool in the Spatial Analyst toolbox of ArcGIS to transform point and line shapefiles into a
raster image on which variations in color represent depth. Initially, I created a colored
topographic map with a cell size (the size of the area assigned a particular elevation) at the
default setting of 2000 meters on a side. This setting did not produce a clear-enough image, so
Page 24
19
subsequently, I used a cell size of 500 meters, which greatly enhanced the sharpness of the map
(Fig. 2.4). The map employed a stretched color scheme, ranging from light yellow to dark
brown—lighter colors represent higher areas and the darker colors represent deeper areas. Thus,
the tops of domes and arches are lighter colored, whereas the floors of basins are darker colored.
Second, I applied the "Hillshade tool" to the completed Topo-to-Raster image to create a shading
affect giving the impression that if the surface of the Precambrian was lit by the Sun positioned
at 315° at an angle of 45° above the horizon. Depth values were multiplied first by 0.3048 to
adjust the measured units to meters, and then were multiplied by 10 to produce a vertical
exaggeration of 10X. The Hillshade image was made 50% transparent and then was placed over
the Topo-to-Raster color image, to create the digitally rendered shaded-relief map of the Great
Unconformity (Fig. 2.5). Areas of Precambrian outcrop were colored red, so that they stand out.
After producing several preliminary versions of the map, I produced the final version (Fig. 2.6).
To create the 3-D look of the map, the map was exported as a georeferenced TIFF image
file. The image file was then placed into ArcScene, which transforms the map from a 2-D
surface to a 3-D surface that can be viewed at any angle the viewer desires. The georeferenced
map image was assigned the base heights of the Topo-to-Raster image to create the 3-D aspect of
the map. To make variations in elevation stand out, the image was produced with a vertical
exaggeration of 10X (Fig. 2.7).
2.5 Production of the Fault-and-Fold Map and Other Shapefile Maps
The second map that I produced is a map that shows the traces of major faults and folds
in the Midcontinent. Obtaining data for this map proved to be a challenge, for structures in the
Midcontinent are not well exposed, and in many cases can only be inferred from subsurface data
Page 25
20
(e.g., structure-contour maps of reference horizons), and literature about these structures is
sparse. Nevertheless, I was able to find sufficient information by using preexisting maps and
cross sections at a variety of scales, available in journals, USGS or state-survey publications and
open-file reports, field guides, and theses. Data were difficult to correlate; however, because
some source maps show entire regions, some show individual states, and some show only
relatively small portions of states. Compilation problems also occurred because different data
sources portray the structures at different levels of detail, structures mapped in one area were not
necessarily mapped in adjacent areas, one map depicts a given structure as fault while another
map of the same area depicts it as a fold or as a fault-fold pair, and existing portrayals of
structures on maps do not all depict cross-cutting relationships correctly. Because of the nature
of source data, the map that I have produced should not be viewed as having the same level of
accuracy as a surface-geology map, but it can be used to help visualize the distribution and trend
of structures.
To produce my ArcGIS map, I first created digital shapefiles of faults and folds by
scanning and then digitizing the faults and folds. A separate shapefile was created for each
structure. These were added directly to a base map, the same base map that I used for the
shaded-relief map of basement topography (Fig. 2.8). Once all of the faults and folds were
added to the map, I reviewed available descriptions of each structure, and then produced a
summary description which was entered in a Microsoft Excel spreadsheet, which ended up being
21 pages long (Table 2.1). Examples of data collected include the age of the formation of the
structure, the age of the last known activity along that structure, the sense of displacement on the
structure, and references that describe the structure. Faults and folds that were found to not
intersect at the Great Unconformity (based on the literature research) were removed from the
Page 26
21
final shapefile. I determined which basement-involved structures to include in the study by
examining how much data I collected from a detailed literature research on all of the faults and
folds I could find references to. I classified the faults and folds by the amount of confidence I
had that the structures existed based on this literature research, with a scale from 0 to 3, in which
0 indicates no confidence and no information available other than the drawn structure on the map
and 3 indicates great confidence that the structure exists based on a large amount of data
available. I also simplified some of the major structures, meaning that I removed the subsidiary
faults and folds so that the structure lines appear relatively smooth at a page-size scale of the
map. The updated Excel spreadsheet was attached to the final fault and fold shapefile (Fig. 2.9)
to create a more detailed attribute table for the dataset (see Table 2.1).
Additional shapefiles were created to further analyze both the shaded-relief map and the fault-
and-fold map. The shapefile labeled ‘Cordillera’ defines the foreland edge of the region that lies
to the west of cratonic-platform crust. Thus, the trace of this line corresponds with the eastern
edge of the Basin-and-Range Province, the region of crust that has undergone significant
stretching and thinning in the Cenozoic, and had undergone stretching and thinning at the end of
the Precambrian. The Ouachita orogen shapefile shows the foreland edge of the Ouachita fold-
thrust belt in Oklahoma and Arkansas, the Appalachian shapefile shows the western edge of the
Appalachian fold-thrust belt, and the ‘Coastal Plain’ outlines the northern edge of the region that
was submerged when sea level was high during the Cretaceous and early Cenozoic. The
subsurface of the coastal plain was not included in my study, because it has undergone stretching
and faulting due to Atlantic Ocean opening, so the region is not considered part of the
continental-interior platform.
Page 27
22
In general, the area of my study included only areas inboard of the Cordilleran, Ouachita,
Appalachian, and Coastal plain shapefiles (see Fig. 1.1). There are two exceptions to this rule,
however. The first exception is the area beneath Mississippi Embayment, a region where
coastal-plain sediments extend north, up the Mississippi Valley to the southern end of Illinois. I
included this area because it has not undergone significant tectonic subsidence due to Atlantic
Ocean opening, even though it was buried by Cretaceous/Cenozoic sediment. By including the
area beneath the Mississippi Embayment, my map can depict the important New Madrid Seismic
zone, as well as the Oklahoma-Alabama transform fault. The second exception is the area of the
Appalachian foreland between the foreland edge of the Appalachian fold-thrust belt and the
exposed basement thrust slices of the Blue-Green-Long Axis. I included this region because it
encompasses the deeper portion of the Appalachian Basin as well as relict rifts, such as the
Montgomery Rift. Leaving these features out would give the false impression that basement
gradually got shallower progressively from the western edge of the Appalachian basin up to the
Blue-Green-Long axis.
My map also includes several other shapefiles that can be useful for tectonic
interpretation (Fig. 2.10). A shapefile labeled ‘Precambrian Outcrop’, as noted earlier, which
outlines areas within the study area where Precambrian rocks exist at the Earth’s surface.
Another shapefile, called ‘Rift Zones’, indicates where the failed rift zones (e.g., aulacogens) that
have filled with significant sediment and/or volcanics are located. I constructed this shapefile
based on the literature search and the major rift bounding faults that I mapped. The final
shapefile that I produced is labeled ‘Domes and Basins’, which outlines the borders of
intracratonic domes, arches, and basins (Fig. 2.11). Data used to construct the Domes and
Basins shapefile comes from the literature research (especially the source maps).
Page 28
23
Table 2.1: Attributes of Midcontinent Structural Features. ______________________________________________________________________________
The table that follows was constructed in conjunction with the fault-and-fold map produced in
this study. Information collected for the attribute table was collected between September 2011
and May 2013, and was entered into an Excel document for readability. The fields are filled
according to the varying degrees of information available for each structure. The following title
column descriptions will attempt to provide an explanation for the information entered into the
attribute table:
• FID: The FID, or Feature Identification number is a distinctive number provided by ArcGIS
for each line or structure on the map.
• Type of Feature: The Type of Feature column provides a choice of fourteen different types of
structures that could be present in the Precambrian basement, including faults and folds.
• Structure Name: The Structure-name column indicates the recognized name of the structure, if
one is available in the literature.
• Trend/Strike: This description provides a generalized map trend and measured strike (if
available) of the structures.
• Dip/Plunge: This description provides a generalized or measured (if available) explanation of
the vertical motion of the structure.
• Age formed: The Age formed column indicates a timing of when the structure began to
experience movement or deformation (if available).
• Last Activity: The Last Activity column provides a timing of the last movement or
deformation experienced by the structure (if available).
• Const.: The Const. (Constraint) column attempts to assign a number between 1 and 3 based
on the level of confidence from the literature research that the structures are true on the map,
with 1 being the lowest level of confidence and 3 being the highest level.
• Other: The Other column provides a more detailed description of the structure, regarding to
the deformation history, type of structure, displacement measurements, and other important
information.
• References: The References column includes the references used in the map layout and
informative descriptions of the structures. The full citations for the references are provided in
the references section at the end of this thesis.
Page 29
24
Table 2.1: Attribute table for the Midcontinent structures.
FID
typ
e o
f fe
atu
rest
ructu
re_
nam
etr
end
/str
ike
dip
/plu
nge
age fo
rmed
last
activity
co
nst
.o
ther
refe
rences
0right la
tera
l st
rik
e s
lip
fault
Verm
illio
n fault
WN
W-E
SE
steep
dip
3sp
lits
into
Wo
lf L
ak
e a
nd
No
rth
Kaw
ishiw
i fa
ults,
merg
es
with
Quetico
fault a
t C
anad
ian
bo
rder
Bunk
er
eta
l 1
985
, B
auer
et al 2
011
, S
ims
19
72
,
Sim
s eta
l 1
991
1hig
h a
ngle
fault
Burn
sid
e L
ak
e fault
NE
-SW
S s
ide d
ow
n,
steep
ly d
ipp
ing
or
vert
ical
3in
itia
lly d
om
inant st
rik
e s
lip
mo
tio
n,
revers
e fault a
nd
rig
ht
late
ral st
rik
e s
lip fault
Bauer
et al 2
011
2le
ft late
ral st
rik
e s
lip
fault
Waasa
fault
NE
-SW
vert
ical?
2S
ims
19
72
3re
vers
e fault
Hale
y fault
NW
-SE
S s
ide d
ow
n,
steep
ly d
ipp
ing
or
vert
ical
3in
itia
lly d
om
inant st
rik
e s
lip
mo
tio
n
Bauer
et al 2
011
4th
rust
fault
Wo
lff L
ak
e fault
E-W
S?
3d
om
inantly s
trik
e s
lip s
ense
of
mo
vem
ent
Bauer
et al 2
011
5th
rust
fault
Rain
y L
ak
e-S
ein
e R
iver
fault
NE
-SW
NP
recam
brian
3b
oth
dextr
al sh
ear
and
ductile
shear
zone
Bauer
et al 2
011
6th
rust
fault
Rauch fault z
one
NE
-SW
N2
Sim
s 1
972
7th
rust
fault
Bear
Riv
er
fault
NE
-SW
S2
Sim
s 1
972
8th
rust
fault
Mud
Cre
ek
shear
zone
N7
0E
N3
Bauer
et al 2
011
9sh
ear
zone
Murr
ay s
hear
zone
NE
-SW
2S
ims
19
72
10
left late
ral st
rik
e s
lip
fault
Cam
p R
ivard
fault
NE
-SW
2S
ims
19
72
11
thru
st fault
Do
ugla
s fa
ult
NE
-SW
vert
ical, S
E s
ide
up
?
3W
part
of M
idco
ntinent R
ift
syst
em
Van S
chm
us
19
92
, S
ims
and
Mo
rey 1
972
12
hig
h a
ngle
thru
st fault
Malm
o S
tructu
ral
dis
co
ntinuity
NE
-SW
S2
south
ern
part
of G
reat L
ak
es
tecto
nic
zo
ne,
poss
ible
age
co
rrela
tio
n w
ith N
iagara
fault
zone
So
uth
wic
k a
nd
Mo
rey
1991
13
thru
st fault
Hin
ck
ley fault
NE
-SW
E2
Bauer
et al 2
011
14
thru
st fault
Pin
e fault
NN
E-S
SW
E3
para
llels
Do
ugla
s fa
ult
Van S
chm
us
19
92
15
transf
er
fault
Belle
Pla
ine fault z
one
NW
-SE
po
st E
arly
Ord
ovic
ian
3d
eflects
Mid
co
ntinent R
ift to
the
SE
, st
rik
e s
lip a
nd
dip
slip
mo
vem
ent ,
reactivate
d a
s th
rust
fault
Bunk
er
eta
l 1
985
,
Chand
ler
eta
l 2
007
,
Gib
bs
eta
l 1
984
,
Cra
dd
ock
197
2
16
shear
zone
Yello
w M
ed
icin
e s
hear
zone
E-N
EN
26
00
Ma
3se
vera
l p
erio
ds
of d
uctile
defo
rmatio
n,
reactivate
d a
s
thru
st fault?
Bic
kfo
rd e
tal 2
006
,
Chand
ler
eta
l 2
007
17
shear
zone
Sp
irit L
ak
e tecto
nic
zo
ne
E-N
E
SY
avap
ai-
age
stru
ctu
re
3N
bo
und
ary
of Y
avap
ai o
rogen,
truncate
s m
ain
Peno
kean s
utu
re
Chand
ler
eta
l 2
007
, H
olm
eta
l 2
007
, S
chulz
and
Canno
n 2
007
, V
an
Schm
us
19
92
, V
an
Schm
us
eta
l 1
989
Page 30
25
Table 2.1 (cont’d)
18
shear
zone
Gre
at L
ak
es
tecto
nic
zo
ne
E-N
ES
and
N2
600
Ma,
Late
Arc
hean
Late
Cre
taceo
us
2ap
pare
nt vert
ical o
ffse
t ~
75
-
95
m,
dom
inantly d
ip s
lip
mo
vem
ent w
ith late
r re
vers
e d
ip
slip
Chand
ler
eta
l 2
007
,
Gib
bs
eta
l 1
984
, H
olm
eta
l 1
998
, H
olm
eta
l
20
07
, S
ims
eta
l 1
980
19
thru
st fault
Gre
at L
ak
es
tecto
nic
zo
ne
NE
-SW
N2
600
Ma,
late
Arc
hean
late
Cre
taceo
us
2m
ajo
r cru
stal b
ound
ary
,
reactivate
d m
ultip
le tim
es
with
no
rmal and
revers
e s
ense
Chand
ler
eta
l 2
007
,
Gib
bs
eta
l 1
984
, H
olm
eta
l 1
998
, H
olm
eta
l
20
07
, S
ims
eta
l 1
980
20
thru
st fault
Arg
yle
fault
EN
E-W
SW
NW
2B
auer
et al 2
011
21
infe
rred
base
ment
fault
Lancast
er
fault
E-W
2V
an S
chm
us
19
92
22
infe
rred
base
ment
fault
Mid
dle
Riv
er
fault
WN
W-E
SE
2S
ims
19
72
23
thru
st fault
Fo
urt
ow
n fault
NE
-SW
NW
2B
auer
et al 2
011
24
infe
rred
base
ment
fault
Quetico
fault
NE
-SW
2m
erg
es
with V
erm
illio
n fault b
y
Canad
a
Sim
s 1
972
25
right la
tera
l st
rik
e s
lip
fault
Rese
rvatio
n fault
NW
-SE
do
wnth
row
n to
the N
E,
steep
dip
3w
rench m
ovem
ent, r
eactivate
d
severa
l tim
es
McC
orm
ick
201
0, S
ims
eta
l 1
991
26
no
rmal fa
ult
Pie
rre fault
mo
stly
NE
-
SW
do
wnth
row
n to
N
Quate
rnary
3alig
ned
with G
reat L
ak
es
tecto
nic
zo
ne
Cro
ne a
nd
Wheele
r
20
00
, M
cC
orm
ick
201
0,
Nic
ho
ls e
tal 1
989
, S
ims
eta
l 1
991
27
no
rmal fa
ult
Phill
ip fault
NE
-SW
do
wnth
row
n to
N,
55 N
dip
3M
cC
orm
ick
201
0, S
ims
eta
l 1
991
28
no
rmal fa
ult
Ced
ar
Cre
ek
fault
NN
W-S
SE
do
wnth
row
n to
NE
3W
bo
und
ary
of T
rans-
Hud
son
oro
gen,
900
ft v
ert
ical
dis
pla
cem
ent
McC
orm
ick
201
0, S
ims
eta
l 1
991
29
infe
rred
base
ment
fault
Hart
vill
e-R
aw
hid
e fault/
Fanny P
eak
mo
no
clin
e
NN
E-S
SW
vary
ing d
ip,
steep
lim
b to
the
W
3W
bo
und
ary
of T
rans-
Hud
son
oro
gen,
mo
no
clin
e a
t su
rface
McC
orm
ick
201
0,
Bla
ck
sto
ne 1
993
, W
ick
s
eta
l 1
999
, S
ims
eta
l 1
991
30
no
rmal fa
ult
Plu
m R
iver
fault z
one
E-W
do
wnth
row
n to
the N
3b
rittle
cata
cla
stic
defo
rmatio
n
zones,
70m
vert
ical
dis
pla
cem
ent
And
ers
on 2
006
, B
unk
er
eta
l 1
985
, C
rone a
nd
Wheele
r 2
000
31
no
rmal fa
ult
Fayette s
tructu
ral zo
ne
NE
-SW
do
wnth
row
n to
the S
E
3A
nd
ers
on 2
006
, B
unk
er
eta
l 1
985
32
no
rmal fa
ult
Thurm
an-R
ed
field
stru
ctu
ral zo
ne
NE
-SW
do
wnth
row
n to
the S
3re
peate
d P
hanero
zoic
activity,
rift b
ound
ing fault
And
ers
on 2
006
, B
unk
er
eta
l 1
985
33
no
rmal fa
ult
Thurm
an-R
ed
field
stru
ctu
ral zo
ne
NE
-SW
do
wnth
row
n to
the S
3re
peate
d P
hanero
zoic
activity,
rift b
ound
ing fault
And
ers
on 2
006
, B
unk
er
eta
l 1
985
34
no
rmal fa
ult
Thurm
an-R
ed
field
stru
ctu
ral zo
ne
NE
-SW
do
wnth
row
n to
the S
3re
peate
d P
hanero
zoic
activity,
rift b
ound
ing fault
And
ers
on 2
006
, B
unk
er
eta
l 1
985
Page 31
26
Table 2.1 (cont’d)
35
no
rmal fa
ult
Des
Mo
ines
Riv
er
fault
zone
NW
-SE
do
wnth
row
n to
the N
E
3A
nd
ers
on 2
006
, S
ims
1990
36
infe
rred
base
ment
fault
Sheed
er
Pra
irie
fault z
one
N-S
2A
nd
ers
on 2
006
37
no
rmal fa
ult
Perr
y-H
am
pto
n fault z
one
NE
-SW
do
wnth
row
n to
the S
E
3w
ithin
Mid
co
ntinent R
ift sy
stem
in I
ow
a
And
ers
on 2
006
38
infe
rred
base
ment
fault
10
2 fault z
one
N-S
2A
nd
ers
on 2
006
39
no
rmal fa
ult
No
rthern
Bo
und
ary
fault
zone
NE
-SW
do
wnth
row
n to
the N
W
3N
bo
und
ary
of M
idco
ntinent
Rift sy
stem
And
ers
on 2
006
,
VanS
chm
us
19
92
40
left late
ral st
rik
e s
lip
fault
Hum
bo
ldt fa
ult z
one
NN
E-S
SW
do
wnth
row
n to
the E
1.1
Ga
Pale
ozo
ic3
vert
ical o
ffse
t as
much a
s 9
15m
,
series
of anast
om
osi
ng faults
Baars
and
Watn
ey 1
991
,
Bere
nd
sen 1
997
41
no
rmal fa
ult
Sand
wic
h fault z
one
NW
-SE
do
wnth
row
n to
the N
3B
unk
er
eta
l 1
985
, S
ims
1990
42
hig
h a
ngle
no
rmal
fault
Wauk
esh
a fault
NE
-SW
do
wnth
row
n to
the S
E
3d
isp
laces
Pre
cam
brian b
y
10
00
ft
Bunk
er
eta
l 1
985
, S
ims
19
90
, B
rasc
hayk
o 2
00
5
43
no
rmal fa
ult
Kew
eenaw
fault
NE
-SW
do
wnth
row
n to
the S
3si
nuo
us
trend
Van S
chm
us
19
92
, S
ims
1992
44
no
rmal fa
ult
Lak
e O
wen fault
NE
-SW
do
wnth
row
n to
the E
3S
part
of M
idco
ntinent R
ift
syst
em
Van S
chm
us
19
92
, S
ims
1990
45
shear
zone
Sp
irit L
ak
e tecto
nic
zo
ne
EN
EY
avap
ai-
age
stru
ctu
re
3N
bo
und
ary
of Y
avap
ai o
rogen,
truncate
s m
ain
Peno
kean s
utu
re
Chand
ler
eta
l 2
007
, H
olm
eta
l 2
007
, S
chulz
and
Canno
n 2
007
46
sutu
re z
one
Nia
gara
fault z
one
E-W
S s
ide u
p,
steep
S d
ip,
near
vert
ical
18
50
Ma
3se
para
tes
Sup
erio
r cra
tonic
rock
s to
the N
fro
m a
rc-r
ela
ted
rock
s to
the S
Canno
n e
tal 1
991
,
Chand
ler
eta
l 2
007
,
So
uth
wic
k a
nd
Mo
rey
1991
47
shear
zone
Eau P
lein
e s
hear
zone
E-W
N s
ide u
p,
steep
ly d
ipp
ing
to the N
18
60
-18
40
Ma
3b
ound
ary
betw
een P
em
bin
e-
Wausa
u terr
ane a
nd
Mars
hfield
terr
ane,
inte
rpre
ted
to
be a
pale
osu
ture
Canno
n e
tal 1
991
, H
olm
eta
l 2
007
, R
om
ano
eta
l
20
00
, S
chulz
and
Canno
n
2007
48
hig
h a
ngle
fault
Ste
. G
enevie
ve fault z
one
NW
-SE
do
wnth
row
n to
NE
Late
Pro
tero
zoic
-
Early C
am
brian
po
st-P
enn-
sylv
ania
n
3b
oth
revers
e a
nd
no
rmal fa
ults,
mo
no
clin
e,
poss
ible
left late
ral
mo
vem
ent, tra
nsf
er
fault?
McC
rack
en 1
966
,
Cle
nd
enin
eta
l 1
989
,
Busc
hb
ack
and
Ko
lata
19
90
, N
els
on 1
990
49
no
rmal fa
ult
Big
Riv
er
fault
NE
-SW
do
wnth
row
n to
the N
W
Late
Pro
tero
zoic
-
Early C
am
brian
3m
erg
es
with S
imm
s M
ounta
in
fault to
fo
rm P
alm
er
fault z
one
McC
rack
en 1
966
,
Cle
nd
enin
eta
l 1
989
50
transf
er
fault
Elli
ngto
n fault
NW
-SE
do
wnth
row
n to
the S
W,
steep
dip
(7
0-8
0)
to
NE
Late
Pro
tero
zoic
-
Early C
am
brian
Po
st-
Ord
ovic
ian
3m
ad
e u
p o
f S
weetw
ate
r and
Sue's
Bra
nch fault s
egm
ents
,
reactivate
d a
s re
vers
e/thru
st
faults
McC
rack
en 1
966
,
Cle
nd
enin
eta
l 1
989
Page 32
27
Table 2.1 (cont’d)
51
transf
er
fault
Sim
s M
ounta
in fault
NW
-SE
do
wnth
row
n to
NE
, d
ip <
20
to
>80
NE
Late
Pro
tero
zoic
-
Early C
am
brian
3m
erg
es
with B
ig R
iver
fault to
form
Palm
er
fault z
one,
left
late
ral, n
orm
al, a
nd
revers
e
mo
vem
ent
McC
rack
en 1
966
,
Cle
nd
enin
eta
l 1
989
52
left late
ral st
rik
e s
lip
fault
Bo
livar-
Mansf
ield
fault
zone
NW
-SE
do
wnth
row
n to
the S
W
3le
ft late
ral m
ovem
ent b
y ~
15
mM
cC
rack
en 1
966
,
Cle
nd
enin
eta
l 1
989
53
no
rmal fa
ult
Palm
er
fault z
one
E-W
do
wnth
row
n to
the N
3M
cC
rack
en 1
966
54
transf
er
fault
Shanno
n C
ounty
fault
NW
-SE
do
wnth
row
n to
SW
Late
Pro
tero
zoic
-
Early C
am
brian
3le
ft late
ral st
rik
e s
lip m
ovem
ent
Cle
nd
inin
eta
l 1
989
55
transf
er
fault
Bla
ck
fault
NW
-SE
do
wnth
row
n to
the S
W,
dip
to
the N
E
Late
Pro
tero
zoic
-
Early C
am
brian
35
0m
zo
ne o
f in
tense
defo
rmatio
n,
revers
e,
no
rmal,
and
left late
ral m
ovem
ent
Cle
nd
inin
eta
l 1
989
56
no
rmal fa
ult
Chesa
peak
e fault
NW
-SE
do
wnth
row
n to
the N
E
3M
cC
rack
en 1
966
, S
ims
1990
57
anticlin
eL
inco
ln fo
ldN
W-S
Ed
ow
n to
SW
thro
w,
N4
5W
2p
art
nere
d w
ith C
ap
au G
res
mo
no
clin
e,
en e
chelo
n p
air
McC
rack
en 1
966
,
Harr
iso
n a
nd
Schultz
2002
58
anticlin
eL
a S
alle
anticlin
al b
elt
NN
W-S
SE
2se
vera
l p
erio
ds
of up
lift d
uring
Pale
ozo
ic
Bunk
er
eta
l 1
985
, B
ear
eta
l 1
997
, B
usc
hb
ack
and
Ko
lata
19
90
59
hig
h a
ngle
no
rmal
fault
Wab
ash
Valle
y fault
syst
em
N-N
E
Late
Pale
ozo
ic-
Early M
eso
zoic
Late
Quate
rnary
(<15
Ka)
3d
ip s
lip d
isp
lacem
ent at le
ast
0.6
km
, la
tera
l o
ffse
ts 2
-4k
m,
strik
e s
lip a
nd
revers
e m
otio
n
Bunk
er
eta
l 1
985
, C
rone
and
Wheele
r 2
000
,
Ko
lata
and
Nels
on 1
997
60
mo
no
clin
eD
u Q
uo
in m
ono
clin
eN
-Sd
ips
to E
, st
eep
sid
e o
n the E
late
Cam
brian
Penn-s
ylv
ania
n2
base
ment in
vo
lved
, exte
nd
s
NN
E fro
m C
ottage G
rove fault
zone
Ko
lata
and
Nels
on 1
997
,
Nels
on 1
990
61
anticlin
eS
ale
m-L
oud
en a
nticlin
es
N-S
asy
mm
etr
ical
steep
W lim
b
2b
ase
ment in
vo
lved
fo
r S
ale
m
anticlin
e
Ko
lata
and
Nels
on 1
997
,
Nels
on 1
990
62
anticlin
eW
ate
rlo
o-D
up
o a
nticlin
eN
-NW
steep
W lim
b,
gentle E
lim
b
Late
Mis
s-
issi
pp
ian/ E
arly
Penn-s
ylv
ania
n
2exte
nd
s in
to M
O,
exte
nsi
on o
f
Cap
au G
res
stru
ctu
re?
Ko
lata
and
Nels
on 1
997
,
Harr
iso
n a
nd
Schultz
20
02
, N
els
on 1
990
63
right la
tera
l st
rik
e s
lip
fault
Co
ttage G
rove fault
syst
em
E-W
Late
Penn-
sylv
ania
n/ E
arly
Perm
ian
3b
oth
majo
r and
min
or
faults
with
no
rmal, r
evers
e,
strik
e s
lip,
and
ob
lique m
ovem
ent
Ko
lata
and
Nels
on 1
997
,
Busc
hb
ack
and
Ko
lata
19
90
, N
els
on 1
990
64
no
rmal fa
ult
Lusk
Cre
ek
fault z
one
NE
-SW
SW
dip
pin
g
mast
er
fault
Late
Pre
cam
brian to
Early C
am
brian
Mid
-Late
Quate
rnary
(<75
0K
a)
3N
W b
ound
ary
of R
eelfo
ot R
ift,
revers
e fault d
uring A
lleghenia
n
oro
geny,
no
rmal in
Cam
brian
Cro
ne a
nd
Wheele
r
20
00
, K
ola
ta a
nd
Nels
on
1997
65
hig
h a
ngle
no
rmal
fault
Ro
ugh C
reek
-
Shaw
neeto
wn fault
syst
em
NE
-SW
dip
to
SL
ate
Pre
cam
brian to
Early C
am
brian
po
st P
enn-
sylv
ania
n
3b
raid
ed
hig
h a
ngle
faults,
flo
wer
stru
ctu
res,
max v
ert
ical up
lift at
least
11
00
m
Ko
lata
and
Nels
on 1
997
,
Nels
on 1
990
Page 33
28
Table 2.1 (cont’d)
66
hig
h a
ngle
no
rmal
fault
Pennyrile
fault s
yst
em
EN
E-W
SW
hig
h a
ngle
dip
to
N
Late
Pale
ozo
ic-
Early M
eso
zoic
po
st P
enn-
sylv
ania
n
3en e
chelo
n,
inte
rtw
inin
g faults,
som
e r
evers
e faultin
g a
nd
left
late
ral o
ffse
t
Ko
lata
and
Nels
on 1
997
,
Nels
on 1
990
67
synclin
eM
oo
rman s
ynclin
eE
-W2
directly u
nd
erlain
by R
ough
Cre
ek
Gra
ben
McD
ow
ell
19
86
68
hig
h a
ngle
no
rmal
fault
Flu
ors
par
are
a fault
co
mp
lex
EN
E-W
SW
65
or
steep
er
3P
erm
ian d
ikes,
sill
s, a
nd
dia
trem
es,
no
rmal, r
evers
e,
strik
e s
lip,
and
obliq
ue s
lip
mo
vem
ent
Cro
ne a
nd
Wheele
r
20
00
, B
usc
hb
ack
and
Ko
lata
19
90
69
no
rmal fa
ult
Tab
b fault s
yst
em
E-W
to
E-S
E
steep
dip
, N
sid
e
do
wn
3m
ajo
r d
isp
lacem
ent to
the S
Ko
lata
and
Nels
on 1
997
,
Nels
on 1
990
70
hig
h a
ngle
fault
Ro
yal C
ente
r fa
ult
NE
-SW
do
wnth
row
n to
the S
E
2B
unk
er
eta
l 1
985
71
hig
h a
ngle
fault
Fo
rtvill
e fault
NE
-SW
do
wnth
row
n to
the S
E
2B
unk
er
eta
l 1
985
72
no
rmal fa
ult
Mo
unt C
arm
el fa
ult
NN
W-S
SE
64
W d
ip to
vert
ical
Early P
enn-
sylv
ania
n
3antith
etic n
orm
al fa
ult s
pla
ys
co
mm
on
Bunk
er
eta
l 1
985
, K
ola
ta
and
Nels
on 1
997
, N
els
on
1990
73
hig
h a
ngle
fault
Bo
wlin
g G
reen fault
NN
W-S
SE
near
vert
ical
Late
Ord
ovic
ian to
pre
sent
3fa
ult b
end
fo
lds,
fault
pro
pagatio
n fo
lds,
and
im
bricate
fans
co
mm
on,
no
rmal, r
evers
e,
and
thru
st faults
Bunk
er
eta
l 1
985
,
Onasc
h a
nd
Kahle
19
91
74
infe
rred
base
ment
fault
Outlet fa
ult
NW
-SE
vary
ing d
ip
directio
n
2su
bsu
rface,
may r
each
Pre
cam
brian
Bara
no
ski 2
002
75
infe
rred
base
ment
fault
Mario
n fault
NW
-SE
do
wnth
row
n to
the N
E
2su
bsu
rface,
may r
each
Pre
cam
brian
Bara
no
ski 2
002
76
revers
e fault
Kentu
ck
y R
iver
fault
syst
em
E-N
E2
5-8
0 in S
W
and
NE
Quate
rnary
(1.6
Ma)
3N
bo
und
ary
of R
om
e T
rough,
45
0m
offse
t, left late
ral
co
mp
onent
Cro
ne a
nd
Wheele
r
20
00
, D
raho
vza
l and
No
ger
19
95
, G
ao
eta
l
2000
77
hig
h a
ngle
fault
Irvin
e-P
ain
t C
reek
fault
syst
em
E-N
Ed
ow
nth
row
n to
the S
E
3either
revers
e o
r no
rmal m
otio
nD
raho
vza
l and
No
ger
1995
78
no
rmal fa
ult
Ro
ck
Cast
le R
iver
fault
N-S
to
NE
-
SW
to
E-N
E
do
wnth
row
n to
the N
W
2m
ark
s S
bo
und
ary
of R
om
e
Tro
ugh
Dra
ho
vza
l and
No
ger
1995
79
no
rmal fa
ult
Lexin
gto
n fault/G
renvill
e
fro
nt
N-N
Ed
ow
n to
E a
nd
W
Quate
rnary
2W
bo
und
ary
of R
om
e T
rough,
60
0m
offse
t o
f P
recam
brian
base
ment, p
art
of G
renvill
e fro
nt
Cro
ne a
nd
Wheele
r 2
000
80
hig
h a
ngle
fault
Wic
hita fault z
one
NW
-SE
(N5
0W
)
30
-40
S-S
WL
ate
Pro
tero
zoic
to C
am
brian
Quate
rnary
3co
mp
rise
d o
f M
ounta
in V
iew
fault,
Duncan-C
riner
fault,
Meers
fault,
and
Co
rdell
fault,
vario
us
mo
vem
ent d
irectio
ns
Burc
hett e
tal 1
985
,
Ram
elli
and
Sle
mm
ons
19
86
, L
uza
eta
l 1
987
,
Perr
y 1
989
, N
UR
EG
-
2115 2
012
Page 34
29
Table 2.1 (cont’d)
81
hig
h a
ngle
fault
Nem
aha fault z
one/u
plif
tN
-S/N
NE
-
SS
W,
N1
6E
dip
s to
E a
nd
WL
ate
Mis
s-
issi
pp
ian/ E
arly
Penn-s
ylv
ania
n
po
st M
iss-
issi
pp
ian
3ab
rup
tly c
hanges
directio
n fro
m
NE
-SW
to
NW
-SE
, in
clu
des
an
anticlin
e
Burc
hett e
tal 1
985
,
Ro
bbin
s and
Kelle
r 1
992
,
Merr
iam
19
63
, B
row
n
eta
l 1
983
82
hig
h a
ngle
fault
Cap
au G
res
fault
NW
-SE
do
wnth
row
to
the S
W,
max
dip
s o
f 6
5 S
to
steep
ly
overt
urn
ed
Late
Mis
s-
issi
pp
ian/ E
arly
Penn-s
ylv
ania
n
2p
art
nere
d w
ith L
inco
ln fo
ld,
en
echelo
n p
air,
mo
no
clin
e w
ith
ass
ocia
ted
faults,
revers
e faults
McC
rack
en 1
966
, K
ola
ta
and
Nels
on 1
997
,
Harr
iso
n a
nd
Schultz
20
02
, N
els
on 1
990
83
anticlin
eK
irk
svill
e-M
end
ota
anticlin
e
NW
-SE
2M
cC
rack
en 1
966
84
hig
h a
ngle
fault
Cub
a fault
N-S
do
wnth
row
n to
the E
NE
2M
cC
rack
en 1
966
85
hig
h a
ngle
fault
Leasb
urg
fault
N-S
do
wnth
row
n to
the E
2M
cC
rack
en 1
966
86
anticlin
eP
rocto
r anticlin
eN
W-S
E2
McC
rack
en 1
966
87
hig
h a
ngle
fault
Ritchey fault
E-W
do
wnth
row
n to
the S
2M
cC
rack
en 1
966
88
hig
h a
ngle
fault
Seneca fault
NE
-SW
2M
cC
rack
en 1
966
89
left late
ral st
rik
e s
lip
fault
Lak
e B
asi
n fault z
one
W-E
3B
erg
antino
and
Cla
rk
1985
90
no
rmal fa
ult
Cat C
reek
fault z
one
WN
W-E
SE
dip
s to
SP
rote
rozo
ic3
bo
th n
orm
al and
revers
e
dis
pla
cem
ent, s
ub
surf
ace fault
Berg
antino
and
Cla
rk
19
85
, W
oo
dw
ard
eta
l
1997
91
hig
h a
ngle
fault
Nye-B
ow
ler
fault z
one
NW
-SE
3B
erg
antino
and
Cla
rk
1985
92
hig
h a
ngle
fault
Fro
mb
erg
fault z
one
NE
-SW
2B
erg
antino
and
Cla
rk
1985
93
hig
h a
ngle
fault
Scap
ego
at-
Bannaty
ne
fault z
one
NE
-SW
3B
erg
antino
and
Cla
rk
1985
94
hig
h a
ngle
fault
Weld
on/B
rock
ton F
roid
fault z
one
NE
-SW
Quate
rnary
3
W b
ound
ary
of T
rans-
Hud
son
oro
gen,
either
no
rmal o
r re
vers
e
fault
Berg
antino
and
Cla
rk
19
85
, S
ims
eta
l 1
991
,
Cro
ne a
nd
Wheele
r 2
000
95
thru
st fault
Big
ho
rn e
ast
ern
bo
und
ary
thru
st
NW
-SE
up
thro
wn to
the
W
3E
bo
und
ary
of B
igho
rn
mo
unta
ins
Bla
ck
sto
ne 1
993
96
thru
st fault
Med
icin
e L
od
ge fault
zone
E-W
2S
bo
und
ary
of B
igho
rn b
asi
nB
lack
sto
ne 1
993
, S
tone
1993
97
revers
e fault
Meers
fault
W-N
W,
N6
0-
64W
do
wn to
SW
thro
w (
30
-
40
SW
),
mo
dera
te N
dip
(55
N,
56N
E)
Late
Pre
cam
brian/
Early C
am
brian
Quate
rnary
3vert
ical d
isp
lacem
ent o
f 5
m,
late
ral d
isp
lacem
ent o
f 1
2m
,
po
ssib
ly p
art
of A
lab
am
a-
Ok
laho
ma tra
nsf
orm
Cro
ne a
nd
Wheele
r
20
00
, R
am
elli
and
Sle
mm
ons
19
86
, C
rone
and
Luza
19
86
, L
uza
eta
l
19
87
, P
err
y 1
989
, C
ox
2010
Page 35
30
Table 2.1 (cont’d)
98
infe
rred
base
ment
fault
Wilz
etta fault
NN
E-S
SW
2B
urc
hett e
tal 1
985
99
no
rmal fa
ult
Criner
fault
NW
(N
45
W)
do
wn to
SW
thro
w
pre
-Quate
rnary
3S
E e
nd
of M
eers
Fault,
term
inate
s at O
uachita fo
ld
thru
st b
elt
Cro
ne a
nd
Wheele
r 2
000
100
revers
e fault
Wash
ita V
alle
y fault
NW
-SE
near
vert
ical,
do
wnth
row
n to
N
34
.3km
of le
ft late
ral
dis
pla
cem
ent, b
egan a
s no
rmal
fault
Cro
ne a
nd
Wheele
r
20
00
, P
err
y 1
989
, C
ox
and
Van A
rsd
ale
19
88
101
hig
h a
ngle
fault
Ap
ishap
a fault
NW
-SE
Pre
cam
brian
3su
bsu
rface (
infe
rred
)S
ims
eta
l 2
001
, H
em
bo
rg
1996
102
hig
h a
ngle
fault
Go
re fault
NW
-SE
vert
ical
Pre
cam
brian
3m
ylo
nite z
one,
origin
ate
d a
s
strik
e s
lip fault
Sim
s eta
l 2
001
, T
weto
1980
103
thru
st fault
Win
d R
iver
thru
st fault
NW
-SE
to
WN
W-E
SE
up
thro
wn o
n N
E
sid
e,
dip
s 4
0N
E
3th
rust
s up
Win
d R
iver
Range
Bla
ck
sto
ne 1
993
,
Yo
nk
ee a
nd
Mitra
19
93
104
thru
st fault
E-W
to
NE
-
SW
up
thro
wn o
n S
E
sid
e
2B
lack
sto
ne 1
993
105
thru
st fault
NW
-SE
up
thro
wn o
n the
NE
sid
e
2B
lack
sto
ne 1
993
106
hig
h a
ngle
thru
st fault
Ore
go
n b
asi
n fault
N-S
to
NW
-
SE
up
thro
wn o
n the
W s
ide
2S
tone 1
993
, B
lack
sto
ne
1993
107
hig
h a
ngle
fault
NN
E-S
SW
up
thro
wn o
n E
sid
e
2B
lack
sto
ne 1
993
108
thru
st fault
Ow
l C
reek
up
lift
NN
W-S
SE
up
thro
wn o
n N
sid
e
2B
lack
sto
ne 1
993
109
thru
st fault
E-W
up
thro
wn o
n S
sid
e
2N
of S
weetw
ate
r up
lift
Bla
ck
sto
ne 1
993
110
thru
st fault
NE
-SW
up
thro
wn o
n S
E
sid
e
2B
lack
sto
ne 1
993
111
thru
st fault
E-W
up
thro
wn o
n N
sid
e
2up
lifts
S e
nd
of S
weetw
ate
r
up
lift
Bla
ck
sto
ne 1
993
112
thru
st fault
NW
-SE
up
thro
wn o
n N
E
sid
e
2B
lack
sto
ne 1
993
113
thru
st fault
N-S
up
thro
wn o
n E
sid
e
2W
bo
und
ary
of R
ock
Sp
rings
up
lift
Bla
ck
sto
ne 1
993
114
thru
st fault
Ho
gsb
ack
thru
st fault
N-S
up
thro
wn o
n W
sid
e
2b
ound
ary
of S
evie
r o
rogeny
Bla
ck
sto
ne 1
993
115
thru
st fault
NW
-SE
up
thro
wn o
n N
E
sid
e
2up
lifts
Gro
s V
entr
e R
ange
Bla
ck
sto
ne 1
993
116
thru
st fault
NW
-SE
up
thro
wn o
n the
W s
ide
2B
lack
sto
ne 1
993
117
thru
st fault
Wash
ak
ie r
ange
thru
sts/
Ow
l C
reek
fault
NW
-SE
to
NE
-SW
up
thro
wn o
n the
N s
ide
2d
ips
in d
iffe
rent d
irectio
ns,
sinuo
us
trend
Bla
ck
sto
ne 1
993
Page 36
31
Table 2.1 (cont’d)
118
thru
st fau
ltN
-Sup
thro
wn
on
the
W s
ide
2to
the
E o
f B
eart
oo
th m
oun
tain
sB
lack
sto
ne 1
993
119
thru
st fau
ltN
W-S
Eup
thro
wn
on
E
sid
e
2up
lifts
W e
nd o
f S
wee
twat
er
rang
e
Bla
ckst
one
19
93
120
thru
st fau
ltE
NE
-WS
Wup
thro
wn
on
S
sid
e
2b
etw
een
Win
d R
iver
and
Sw
eetw
ater
ran
ges
Bla
ckst
one
19
93
121
thru
st fau
ltN
E-S
Wva
ryin
g d
ip
direc
tion
2m
ark
s E
bo
und
ary
of F
ront
Ran
ge
Bla
ckst
one
19
93
,
Hem
bo
rg 1
996
122
thru
st fau
ltN
E-S
W to
E-
W
upth
row
n o
n S
sid
e
2N
bo
und
ary
of L
aram
ie r
ange
Bla
ckst
one
19
93
123
thru
st fau
ltN
W-S
E to
N-
S to
E-W
upth
row
n o
n N
sid
e
2E
bo
und
ary
of S
ierr
a M
adre
mo
unta
ins
Bla
ckst
one
19
93
,
Hem
bo
rg 1
996
124
norm
al fau
ltE
-Wd
ow
nthr
ow
n o
n
S s
ide
2cu
ts thr
oug
h R
ock
Sp
ring
s up
lift
Bla
ckst
one
19
93
125
thru
st fau
ltE
-Wup
thro
wn
on
S
sid
e
2m
ark
s N
bo
und
ary
of U
inta
mo
unta
ins
Hem
bo
rg 1
996
126
norm
al fau
ltE
-Wd
ow
nthr
ow
n to
the
S
1so
uth
of U
inta
up
lift
Wo
odw
ard
198
4
127
thru
st fau
ltE
-Wup
thro
wn
to the
N
1si
nuo
us tre
nd,
infe
rred
bas
emen
t
thru
st
Wo
odw
ard
198
4
128
thru
st fau
ltN
W-S
Eup
thro
wn
on
E
sid
e
2W
bo
und
ary
of fr
ont
ran
ges
Hem
bo
rg 1
996
129
thru
st fau
ltN
W-S
Eva
ryin
g d
ip2
with
in N
ort
h P
ark
bas
inH
emb
org
19
96
130
norm
al fau
ltN
-S to
NW
-
SE
do
wnt
hro
wn
to
the
W
2H
emb
org
19
96
131
thru
st fau
ltN
NW
-SS
Eup
thro
wn
to the
NE
2H
emb
org
19
96
132
thru
st fau
ltN
-S to
E-W
upth
row
n to
the
NE
2H
emb
org
19
96
133
norm
al fau
ltN
W-S
Ed
ow
nthr
ow
n to
the
SW
2m
ark
s S
W b
oun
dar
y o
f
Unc
om
pag
re u
plif
t
Hem
bo
rg 1
996
134
norm
al fau
ltS
angr
e d
e C
rist
o fau
ltN
W-S
E6
0 to
the
WL
ate
Qua
tern
ary
2to
the
W o
f S
angr
e d
e C
rist
o
mo
untia
ns
Klu
th a
nd S
chaf
tena
ar
19
94
, C
rone
eta
l 20
06
135
infe
rred
bas
emen
t
faul
t
N-S
2su
bsu
rfac
e H
emb
org
19
96
136
infe
rred
bas
emen
t
faul
t
NW
-SE
2H
emb
org
19
96
137
thru
st fau
ltN
-Sup
thro
wn
to the
W
2m
ark
s E
bo
und
ary
of S
angr
e d
e
Crist
o R
ange
Hem
bo
rg 1
996
138
norm
al fau
ltN
E-S
W to
N-
S
do
wnt
hro
wn
to
the
W
1W
oo
dw
ard
198
4
Page 37
32
Table 2.1 (cont’d)
139
hig
h a
ngle
fault
Peco
s-P
icuris
fault/T
ijera
s-
Cano
ncito
fault z
one
N-S
, to
NE
d
ow
nth
row
n to
NW
and
SE
Pre
cam
brian
Ceno
zoic
2m
ajo
r st
rik
e s
lip fault w
ith left
late
ral o
bliq
ue m
ovem
ent,
anast
om
osi
ng e
n e
chelo
n h
igh
angle
faults
Ald
rich 1
986
, C
hap
in a
nd
Cath
er
19
94
, L
ew
is a
nd
Bald
rid
ge 1
994
, B
arr
ow
and
Kelle
r 1
994
,
Saly
ard
s and
Ald
rich
1994
140
infe
rred
base
ment
fault
Nacim
iento
up
lift
N-S
to
NN
E-
SS
W
1W
bo
und
ary
of A
lbuq
uerq
ue
basi
n
Lo
zinsk
i 1
994
141
hig
h a
ngle
fault
Rio
Puerc
o fault
zone/L
ucero
up
lift
N-S
do
wnth
row
n to
E
1W
bo
und
ary
of A
lbuq
uerq
ue
basi
n,
num
ero
us
faults
and
fo
lds
Lo
zinsk
i 1
994
, S
lack
and
Cam
pb
ell
19
76
142
revers
e fault
Manza
no
-Lo
s P
ino
s up
lift
N-S
S d
ip,
do
wnth
row
n to
W
Pro
tero
zoic
(1.6
5-1
.60G
a)
1right la
tera
l co
mp
onent, E
bo
und
ary
of R
io G
rand
e R
ift
Magnani eta
l 2
004
,
Lo
zinsk
i 1
994
, M
ay e
tal
1994
143
infe
rred
base
ment
fault
NN
E-S
SW
1su
bsu
rface (
infe
rred
)H
em
bo
rg 1
996
144
thru
st fault
NN
E-S
SW
up
thro
wn to
the
W
1W
oo
dw
ard
198
4
145
no
rmal fa
ult
N-S
do
wnth
row
n to
the E
1p
art
of R
io G
rand
e R
ift
Wo
odw
ard
198
4
146
infe
rred
base
ment
fault
N-S
1p
art
of R
io G
rand
e R
ift
Wo
odw
ard
198
4
147
no
rmal fa
ult
N-S
do
wnth
row
n to
the W
1si
nuo
us
trend
Wo
odw
ard
198
4
148
anticlin
eC
had
ron A
rch
NW
-SE
2C
arlso
n 1
970
149
hig
h a
ngle
fault
NE
-SW
do
wnth
row
n to
the S
E
1P
recam
brian c
rust
al b
ound
ary
?S
ims
eta
l 1
991
150
right la
tera
l st
rik
e s
lip
fault
NE
-SW
2S
ims
eta
l 1
991
151
right la
tera
l st
rik
e s
lip
fault
NW
-SE
2S
ims
eta
l 1
991
152
no
rmal fa
ult
Unio
n fault
NE
-SW
do
wnth
row
n to
the S
E
Mid
dle
Pale
ozo
ic?
2S
bo
und
ary
of M
idco
ntinent rift
in N
E
Carlso
n 1
970
, C
arlso
n
1997
153
hig
h a
ngle
fault
NW
-SE
do
wnth
row
n to
the S
W
2p
art
of C
entr
al K
ansa
s U
plif
tC
ole
19
76
154
hig
h a
ngle
fault
NW
-SE
do
wnth
row
n to
the S
W
2p
art
of C
entr
al K
ansa
s U
plif
tC
ole
19
76
155
hig
h a
ngle
fault
NW
-SE
do
wnth
row
n to
the S
W
2p
art
of C
entr
al K
ansa
s U
plif
tC
ole
19
76
156
hig
h a
ngle
fault
NN
E-S
SW
do
wnth
row
n to
the W
2p
art
of C
entr
al K
ansa
s U
plif
tC
ole
19
76
157
hig
h a
ngle
fault
NW
-SE
do
wnth
row
n to
the S
W
2p
art
of C
entr
al K
ansa
s U
plif
tC
ole
19
76
Page 38
33
Table 2.1 (cont’d)
158
hig
h a
ngle
fault
NW
-SE
do
wnth
row
n to
the S
W
2p
art
of C
entr
al K
ansa
s U
plif
tC
ole
19
76
159
hig
h a
ngle
fault
NN
E-S
SW
do
wnth
row
n to
the E
2re
aches
Pre
cam
brian r
ock
sC
ole
19
76
160
hig
h a
ngle
fault
NW
-SE
do
wnth
row
n to
the S
W
2re
aches
Pre
cam
brian r
ock
sC
ole
19
76
161
infe
rred
base
ment
fault
Waurik
a A
rch
NW
-SE
do
wnth
row
n to
the S
W
2re
aches
base
ment
Cam
pb
ell
and
Web
er
20
06
, E
win
g 1
990
162
hig
h a
ngle
fault
Centr
al O
kla
ho
ma fault
zone
N-S
do
wnth
row
n to
the E
and
W
3re
aches
base
ment
Cam
pb
ell
and
Web
er
2006
163
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the S
W
2re
aches
base
ment
Cam
pb
ell
and
Web
er
2006
164
thru
st fault
Sulp
hur
fault?
NW
-SE
do
wnth
row
n to
the N
2re
aches
base
ment
Cam
pb
ell
and
Web
er
20
06
, E
win
g 1
990
165
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the S
W
2re
aches
base
ment
Cam
pb
ell
and
Web
er
2006
166
infe
rred
base
ment
fault
NE
-SW
do
wnth
row
n to
the S
E
1no
rmal fa
ult?
Sim
s 1
990
167
no
rmal fa
ult
Hurr
icane fault
NE
-SW
steep
ly W
active to
day
2B
asi
n a
nd
Range s
tructu
re (
Late
Mio
cene)
Davis
19
99
168
hig
h a
ngle
no
rmal
fault
Sevie
r fa
ult
NE
-SW
W2
Davis
19
99
169
no
rmal fa
ult
Pausa
ugunt fa
ult
NE
-SW
75W
late
Tert
iary
to
Ho
locene
2exte
nd
s as
a m
ono
clin
e to
the N
Davis
19
99
170
no
rmal fa
ult
NN
E-S
SW
do
wnth
row
n to
the W
1W
oo
dw
ard
198
4
171
no
rmal fa
ult
NN
E-S
SW
do
wnth
row
n to
the W
1W
oo
dw
ard
198
4
172
mo
no
clin
eW
ate
rpo
ck
et fo
ldN
W-S
Est
eep
sid
e to
the
E
2D
avis
19
99
173
mo
no
clin
eS
an R
afa
el m
ono
clin
eN
E-S
Wst
eep
sid
e to
the
E
2W
oo
dw
ard
198
4
174
mo
no
clin
eE
ast
Kaib
ab
mo
no
clin
eN
-SE
dip
pin
g?
Pre
cam
brian
2m
ax o
ffse
t o
f 7
50m
, re
activate
d
Pre
cam
brian fault u
nd
er
mo
no
clin
e
Hunto
on 1
993
175
mo
no
clin
eN
E-S
W to
E-
W
steep
sid
e to
the
E
1W
oo
dw
ard
198
4
176
shear
zone
Shylo
ck
shear
zone
N-S
1B
erg
h a
nd
Karlst
rom
1992
177
mo
no
clin
eN
-Sst
eep
sid
e to
the
E
1W
oo
dw
ard
198
4
178
mo
no
clin
eN
E-S
W to
E-
W
steep
sid
e to
the
S
1W
oo
dw
ard
198
4
Page 39
34
Table 2.1 (cont’d)
179
no
rmal fa
ult
NE
-SW
2N
bo
und
ary
of R
om
e T
rough
Saylo
r 1
999
180
no
rmal fa
ult
Ak
ron-S
uffie
ld-S
mith
To
wnsh
ip fault z
ones
WN
W-E
SE
do
wnth
row
n to
the S
W
2se
t o
f 3
en e
chelo
n faults
Bara
no
ski 2
002
181
no
rmal fa
ult
Hig
hla
nd
tow
n fault
WN
W-E
SE
do
wnth
row
n to
the S
W
2in
clu
des
part
of P
itts
burg
-
Wash
ingto
n c
ross
str
ike
stru
ctu
ral d
isco
ntinuity
Bara
no
ski 2
002
182
hig
h a
ngle
fault
Sta
rr fault s
yst
em
E-W
do
wnth
row
n to
the S
2B
ara
no
ski 2
002
,
Bra
nno
ck
199
3
183
infe
rred
base
ment
fault
Cam
brid
ge C
ross
Str
ike
Str
uctu
ral d
isco
ntinuity
NW
-SE
do
wnth
row
n to
the S
W
2no
rmal fa
ult?
Bara
no
ski 2
002
184
infe
rred
base
ment
fault
NE
-SW
2N
bo
und
ary
of th
e R
om
e
Tro
ugh
Patc
hen e
tal 2
006
185
no
rmal fa
ult
Cla
rend
on-L
ind
en fault
syst
em
N-S
E a
nd
WL
ate
Pro
tero
zoic
to C
am
brian
3b
road
zo
ne o
f sm
all
dis
pla
cem
ent fa
ults
Fak
und
iny a
nd
Po
mero
y
20
02
, R
ick
ard
197
3,
Cro
ne a
nd
Wheele
r 2
000
186
no
rmal fa
ult
Do
lgerv
ille fault
NN
E-S
SW
do
wnth
row
n to
the W
3Ja
co
bi 2
002
, R
ick
ard
1973
187
no
rmal fa
ult
No
se fault
NE
-SW
to
N-
S
do
wnth
row
n to
the E
3Ja
co
bi 2
002
, R
ick
ard
1973
188
no
rmal fa
ult
Ho
ffm
ans
fault
N-S
do
wnth
row
n to
the E
2R
ick
ard
197
3
189
no
rmal fa
ult
N-S
do
wnth
row
n to
the E
2R
ick
ard
197
3
190
no
rmal fa
ult
N-S
do
wnth
row
n to
the E
2R
ick
ard
197
3
191
infe
rred
base
ment
fault
NW
-SE
to
E-
W
do
wnth
row
n to
the S
1E
win
g 1
990
192
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the S
W
1E
win
g 1
990
193
no
rmal fa
ult
Big
Lak
e fault
E-W
do
wnth
row
n to
the N
2E
win
g 1
990
194
no
rmal fa
ult
NW
-SE
do
wnth
row
n to
the S
W
2E
win
g 1
990
195
no
rmal fa
ult
NW
-SE
do
wnth
row
n to
the N
E
2E
win
g 1
990
196
infe
rred
base
ment
fault
N-S
to
E-W
vary
ing d
ip
directio
n
1E
win
g 1
990
197
no
rmal fa
ult
E-W
do
wnth
row
n to
the S
2E
win
g 1
990
198
no
rmal fa
ult
N-S
do
wnth
row
n to
the E
2E
win
g 1
990
Page 40
35
Table 2.1 (cont’d)
199
infe
rred
base
ment
fault
Huap
ache fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
200
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
201
thru
st fault
Ap
ache M
ounta
in fault
NW
-SE
vary
ing d
ip
directio
n
2E
win
g 1
990
202
no
rmal fa
ult
NW
-SE
do
wnth
row
n to
the S
W
2E
win
g 1
990
203
infe
rred
base
ment
fault
N-S
do
wnth
row
n to
the W
1E
win
g 1
990
204
infe
rred
base
ment
fault
E-W
to
NW
-
SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
205
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
206
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
207
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
208
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the S
W
1E
win
g 1
990
209
infe
rred
base
ment
fault
E-W
do
wnth
row
n to
the N
1E
win
g 1
990
210
infe
rred
base
ment
fault
E-W
do
wnth
row
n to
the N
1E
win
g 1
990
211
infe
rred
base
ment
fault
E-W
do
wnth
row
n to
the S
1E
win
g 1
990
212
infe
rred
base
ment
fault
NW
-SE
vary
ing d
ip
directio
n
1E
win
g 1
990
213
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
214
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
215
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the N
E
1E
win
g 1
990
216
thru
st fault
E-W
up
thro
wn to
the
N
2E
win
g 1
990
217
infe
rred
base
ment
fault
E-W
do
wnth
row
n to
the S
1E
win
g 1
990
218
infe
rred
base
ment
fault
E-W
do
wnth
row
n to
the N
1E
win
g 1
990
219
infe
rred
base
ment
fault
E-W
do
wnth
row
n to
the S
1E
win
g 1
990
220
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the S
W
1no
rmal fa
ult?
Ew
ing 1
990
Page 41
36
Table 2.1 (cont’d)
221
infe
rred
base
ment
fault
Cart
a V
alle
y fault z
one
E-W
to
NW
-
SE
do
wnth
row
n to
the N
1no
rmal fa
ult?
Ew
ing 1
990
222
infe
rred
base
ment
fault
NE
-SW
do
wnth
row
n to
the S
E
1no
rmal fa
ult?
Ew
ing 1
990
223
infe
rred
base
ment
fault
N-S
do
wnth
row
n to
the W
1no
rmal fa
ult?
Ew
ing 1
990
224
no
rmal fa
ult
Maso
n G
rab
en
NE
-SW
do
wnth
row
n to
the S
E
2E
win
g 1
990
225
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the S
E
2E
win
g 1
990
226
infe
rred
base
ment
fault
Lam
pasa
s arc
hN
E-S
Wd
ow
nth
row
n to
the S
E
1E
win
g 1
990
227
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the S
E
1E
win
g 1
990
228
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the S
E
1E
win
g 1
990
229
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the S
E
2E
win
g 1
990
230
infe
rred
base
ment
fault
NW
-SE
do
wnth
row
n to
the S
W
1co
ntinuatio
n o
f W
aurik
a a
rch?
Ew
ing 1
990
231
right la
tera
l st
rik
e s
lip
fault
NE
-SW
1W
oo
dw
ard
198
4
232
no
rmal fa
ult
Reelfo
ot F
ault
NN
W-S
SE
do
wnth
row
n to
the S
W
2C
sonto
s eta
l 2
008
233
infe
rred
base
ment
fault
White R
iver
fault z
one
NW
-SE
2cuts
acro
ss M
issi
ssip
pi V
alle
y
Gra
ben
Cso
nto
s eta
l 2
008
234
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the S
E
2N
W b
ound
ary
of R
eelfo
ot R
ift
Cso
nto
s eta
l 2
008
235
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the N
W
2S
E b
ound
ary
of R
eelfo
ot R
ift
Cso
nto
s eta
l 2
008
236
hig
h a
ngle
fault
NE
-SW
2centr
al p
art
of R
eelfo
ot R
ift
Cso
nto
s eta
l 2
008
237
transf
er
fault
NW
-SE
2p
art
of R
eelfo
ot R
ift
Cso
nto
s eta
l 2
008
238
no
rmal fa
ult
NW
-SE
do
wnth
row
n to
the S
W
2G
rosh
ong e
tal 2
010
239
no
rmal fa
ult
NW
-SE
do
wnth
row
n to
the S
W
2G
rosh
ong e
tal 2
010
240
no
rmal fa
ult
NW
-SE
do
wnth
row
n to
the S
W
2G
rosh
ong e
tal 2
010
241
no
rmal fa
ult
NE
-SW
do
wnth
row
n to
the S
E
2T
ho
mas
and
Bayo
na
2005
242
no
rmal fa
ult
NE
-SW
NW
2S
bo
und
ary
of R
om
e T
rough
Patc
hen e
tal 2
006
243
transf
er
fault
NW
-SE
1S
aylo
r 1
999
244
no
rmal fa
ult
NE
-SW
NW
2S
bo
und
ary
of R
om
e T
rough
Saylo
r 1
999
245
hig
h a
ngle
fault
Mo
nic
o fault
NE
-SW
1fa
ult intr
ud
ed
by n
arr
ow
dik
eS
ims
19
92
Page 42
37
Table 2.1 (cont’d)
246
hig
h a
ngle
fault
Ow
en fault
NE
-SW
do
wnth
row
n to
the N
W
2S
ims
19
92
, S
ims
19
89
247
shear
zone
Jum
p R
iver
shear
zone
NE
-SW
do
wnth
row
n to
the N
W
2S
ims
19
92
, S
ims
19
89
248
shear
zone
Ath
ens
Shear
zone
NE
-SW
dip
s 7
2 N
W,
do
wnth
row
n to
the S
E
2S
ims
19
92
249
revers
e fault
Min
era
l L
ak
e fault
WN
W-E
SE
do
wnth
row
n to
the S
Mid
dle
Pro
tero
zoic
2in
itia
ted
as
a n
orm
al fa
ult a
nd
late
r re
vers
ed
, right la
tera
l
co
mp
onent
Sim
s 1
992
250
hig
h a
ngle
thru
st fault
Fla
mb
eau F
low
age fault
E-W
to
NE
-
SW
up
thro
wn to
the
S
Early
Pro
tero
zoic
2in
ferr
ed
to
fla
tten a
t d
ep
th,
offse
t
by M
inera
l L
ak
e fault
Sim
s 1
992
251
hig
h a
ngle
thru
st fault
NW
-SE
up
thro
wn to
the
S
Early
Pro
tero
zoic
1in
ferr
ed
to
fla
tten a
t d
ep
thS
ims
19
92
252
hig
h a
ngle
fault
NW
-SE
1S
ims
19
92
253
hig
h a
ngle
fault
NW
-SE
1S
ims
19
92
254
hig
h a
ngle
thru
st fault
Bush
Lak
e fault
E-W
up
thro
wn to
the
S
Early
Pro
tero
zoic
2in
ferr
ed
to
fla
tten a
t d
ep
thS
ims
19
92
255
hig
h a
ngle
thru
st fault
So
uth
Range fault
E-W
up
thro
wn to
the
S
Early
Pro
tero
zoic
2in
ferr
ed
to
fla
tten a
t d
ep
thS
ims
19
92
256
hig
h a
ngle
fault
NE
-SW
1in
trud
ed
by n
arr
ow
dik
eS
ims
19
92
257
hig
h a
ngle
fault
E-W
1p
art
of M
arq
uette I
ron R
ange
Sim
s 1
992
258
right la
tera
l st
rik
e s
lip
fault
NE
-SW
2S
ims
eta
l 1
991
259
infe
rred
base
ment
fault
NN
E-S
SW
1S
ims
eta
l 1
991
260
infe
rred
base
ment
fault
N-S
1S
ims
eta
l 1
991
261
mo
no
clin
eE
cho
Clif
fs m
ono
clin
eN
-S2
Hunto
on 1
993
262
right la
tera
l st
rik
e s
lip
fault
Ro
me tra
nsv
ers
e
base
ment fa
ult
NW
-SE
2tr
ansf
er
fault o
f th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
263
right la
tera
l st
rik
e s
lip
fault
Annis
ton tra
nsv
ers
e
base
ment fa
ult
NW
-SE
2tr
ansf
er
fault o
f th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
264
no
rmal fa
ult
NE
-SW
NW
2S
E b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
265
no
rmal fa
ult
NE
-SW
SE
2N
W b
ound
ary
of th
e
Birm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
266
no
rmal fa
ult
NE
-SW
SE
2N
W b
ound
ary
of th
e
Birm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
Page 43
38
Table 2.1 (cont’d)
267
no
rmal fa
ult
NE
-SW
NW
2S
E b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
268
no
rmal fa
ult
NE
-SW
NW
2S
E b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
269
no
rmal fa
ult
NE
-SW
SE
2N
W b
ound
ary
of th
e
Birm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
270
left late
ral st
rik
e s
lip
fault
NW
-SE
2tr
ansf
er
fault o
f th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
271
no
rmal fa
ult
N-S
W2
E b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
272
no
rmal fa
ult
NN
E-S
SW
SE
2W
bo
und
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
273
transf
er
fault
WN
W-E
SE
2tr
ansf
er
fault o
f th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
274
transf
er
fault
NW
-SE
2tr
ansf
er
fault o
f th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
275
no
rmal fa
ult
NE
-SW
SE
2N
W b
ound
ary
of th
e
Birm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
276
no
rmal fa
ult
NE
-SW
NW
2S
E b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
277
no
rmal fa
ult
N-S
W2
E b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
278
no
rmal fa
ult
N-S
E2
W b
ound
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
279
no
rmal fa
ult
NE
-SW
SE
2W
bo
und
ary
of th
e B
irm
ingham
Base
ment gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
280
infe
rred
base
ment
fault
WN
W-E
SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
281
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
Page 44
39
Table 2.1 (cont’d)
282
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
283
infe
rred
base
ment
fault
E-W
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
284
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
285
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
286
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
287
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
288
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
289
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
290
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
291
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
292
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
293
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
294
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
295
infe
rred
base
ment
fault
E-W
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
296
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
297
infe
rred
base
ment
fault
E-W
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
298
infe
rred
base
ment
fault
N-S
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
299
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
300
infe
rred
base
ment
fault
N-S
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
301
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
302
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
303
infe
rred
base
ment
fault
N-S
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
Page 45
40
Table 2.1 (cont’d)
304
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
305
infe
rred
base
ment
fault
N-S
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
306
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
307
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
308
infe
rred
base
ment
fault
WN
W-E
SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
309
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
310
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
311
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
312
sutu
re z
one
NE
-SW
Pre
cam
brian?
1p
art
of C
heyenne b
elt?
Bad
er
20
08
, 20
09
313
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
314
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
315
infe
rred
base
ment
fault
WN
W-E
SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
316
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
317
infe
rred
base
ment
fault
E-W
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
318
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
319
infe
rred
base
ment
fault
E-W
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
320
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
321
infe
rred
base
ment
fault
WN
W-E
SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
322
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
323
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
324
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
325
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
Page 46
41
Table 2.1 (cont’d)
326
infe
rred
base
ment
fault
NE
-SW
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
327
infe
rred
base
ment
fault
N-S
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
328
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
329
infe
rred
base
ment
fault
NW
-SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
330
infe
rred
base
ment
fault
WN
W-E
SE
1b
ase
d o
n lin
eam
ent m
ap
Esc
h 2
010
331
sutu
re z
one
Cheyenne b
elt
EN
E-W
SW
Pre
cam
brian
2P
ale
op
rote
rozo
ic s
utu
re z
one
Bad
er
20
08
, 20
09
332
no
rmal fa
ult
EN
E-W
SW
S1
N p
art
of R
om
e T
rough/ R
ough
Cre
ek
Gra
ben
Hic
km
an 2
011
333
no
rmal fa
ult
EN
E-W
SW
N1
S p
art
of R
om
e T
rough/ R
ough
Cre
ek
Gra
ben
Hic
km
an 2
011
334
sutu
re z
one
N-S
Pre
cam
brian
2G
renvill
e s
utu
re z
one
Hic
km
an 2
011
335
no
rmal fa
ult
NE
-SW
NW
1S
part
of R
om
e T
rough,
sub
surf
ace
Hic
km
an 2
011
336
mo
no
clin
eN
NW
-SS
E2
part
of L
a S
alle
Anticlin
al b
elt
Busc
hb
ack
and
Ko
lata
1990
337
mo
no
clin
eN
-S2
part
of L
a S
alle
Anticlin
al b
elt
Busc
hb
ack
and
Ko
lata
1990
338
mo
no
clin
eN
-S2
part
of L
a S
alle
Anticlin
al b
elt
Busc
hb
ack
and
Ko
lata
1990
339
mo
no
clin
eB
lack
Hill
s m
ono
clin
eN
-Sst
eep
lim
b to
the
W
2W
ick
s eta
l 1
999
340
no
rmal fa
ult
Osb
orn
e s
tructu
ral zo
ne
NE
-SW
do
wnth
row
n to
the N
3S
ims
19
90
341
no
rmal fa
ult
Eld
ora
str
uctu
ral zo
ne
NE
-SW
do
wnth
row
n to
the N
3S
ims
19
90
342
no
rmal fa
ult
Deco
rah s
tructu
ral zo
ne
NE
-SW
do
wnth
row
n to
the S
3S
ims
19
90
343
no
rmal fa
ult
No
rthern
Chic
kasa
w
stru
ctu
ral zo
ne
NE
-SW
do
wnth
row
n to
the N
3S
ims
19
90
344
no
rmal fa
ult
NE
-SW
SE
2p
art
of B
irm
ingham
Base
ment
Gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
345
no
rmal fa
ult
NE
-SW
SE
2p
art
of B
irm
ingham
Base
ment
Gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
346
no
rmal fa
ult
NE
-SW
SE
2p
art
of B
irm
ingham
Base
ment
Gra
ben
Bayo
na e
tal 2
003
,
Tho
mas
and
Bayo
na
2005
Page 47
42
Table 2.1 (cont’d)
347
norm
al fau
ltN
E-S
WN
W2
par
t o
f B
irm
ingh
am B
asem
ent
Gra
ben
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
348
norm
al fau
ltN
E-S
WN
W2
S p
art o
f B
irm
ingh
am b
asem
ent
grab
en
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
349
norm
al fau
ltN
E-S
WN
W2
par
t o
f B
irm
ingh
am B
asem
ent
Gra
ben
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
350
norm
al fau
ltN
E-S
WS
E2
par
t o
f B
irm
ingh
am B
asem
ent
Gra
ben
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
351
norm
al fau
ltN
E-S
WS
E2
par
t o
f B
irm
ingh
am B
asem
ent
Gra
ben
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
352
norm
al fau
ltN
E-S
WS
E2
par
t o
f B
irm
ingh
am B
asem
ent
Gra
ben
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
353
norm
al fau
ltN
E-S
WS
E2
W p
art o
f B
irm
ingh
am
Bas
emen
t G
rab
en
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
354
norm
al fau
ltN
E-S
WS
E2
W p
art o
f B
irm
ingh
am
Bas
emen
t G
rab
en
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
355
norm
al fau
ltN
E-S
WS
E2
W p
art o
f B
irm
ingh
am
Bas
emen
t G
rab
en
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
356
norm
al fau
ltN
E-S
WS
E2
par
t o
f B
irm
ingh
am B
asem
ent
Gra
ben
Bay
ona
eta
l 20
03
,
Tho
mas
and
Bay
ona
2005
357
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rko
ma
bas
in
Arb
enz
20
08
358
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rko
ma
bas
in
Arb
enz
20
08
359
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rko
ma
bas
in
Arb
enz
20
08
360
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rko
ma
bas
in
Arb
enz
20
08
361
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rko
ma
bas
in
Arb
enz
20
08
362
norm
al fau
ltE
NE
-WS
WS
2in
terp
rete
d u
sing
cro
ss s
ectio
ns
in A
rko
ma
bas
in
Arb
enz
20
08
Page 48
43
Table 2.1 (cont’d)
363
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
364
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
365
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
366
no
rmal fa
ult
EN
E-W
SW
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
367
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
368
no
rmal fa
ult
E-W
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
369
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
370
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
371
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
372
transf
er
fault
N-S
unk
no
wn
1in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
373
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
374
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
375
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
376
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
377
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
378
no
rmal fa
ult
NE
-SW
SE
2in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
379
transf
er
fault
NN
E-S
SW
unk
no
wn
1in
terp
rete
d u
sing c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
380
no
rmal fa
ult
WN
W-E
SE
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
381
no
rmal fa
ult
WN
W-E
SE
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
382
no
rmal fa
ult
E-W
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
383
no
rmal fa
ult
E-W
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
384
no
rmal fa
ult
E-W
S2
inte
rpre
ted
usi
ng c
ross
sectio
ns
in A
rko
ma b
asi
n
Arb
enz
20
08
Page 49
44
Table 2.1 (cont’d)
385
norm
al fau
ltE
-WS
2in
terp
rete
d u
sing
cro
ss s
ectio
ns
in A
rkom
a bas
in
Arb
enz
20
08
386
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rkom
a bas
in
Arb
enz
20
08
387
norm
al fau
ltN
E-S
WS
E2
inte
rpre
ted
usi
ng c
ross
sec
tions
in A
rkom
a bas
in
Arb
enz
20
08
388
infe
rred
bas
emen
t
faul
t
Eas
t T
enne
ssee
Sei
smic
Zo
ne
NE
-SW
unk
now
nac
tive
today
1in
ferr
ed fro
m s
eism
icity
, m
ultip
le
smal
l fau
lts tre
ndin
g N
and
E
Po
wel
l eta
l 19
94
389
infe
rred
bas
emen
t
faul
t
Ok
laho
ma-
Ala
bam
a
tran
sfo
rm
NW
-SE
unk
now
n1
mar
ks
the
S e
dge
of th
e N
ort
h
Am
eric
an c
rato
n
Tho
mas
20
11
390
norm
al fau
ltN
W-S
ES
W1
infe
rred
in B
lack
War
rio
r B
asin
Gro
sho
ng e
tal 2
010
391
norm
al fau
ltN
W-S
ES
W1
infe
rred
in B
lack
War
rio
r B
asin
Gro
sho
ng e
tal 2
010
392
norm
al fau
ltN
W-S
ES
W1
infe
rred
in B
lack
War
rio
r B
asin
Gro
sho
ng e
tal 2
010
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Figure 2.1: Outline of the United States overlaid by existing digital contour data (in red), with a
contour interval of 1000 ft.
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Figure 2.2a: Georeferenced image of the Precambrian Structure Map of North Dakota (Heck
1988).
Figure 2.2b: Precambrian contours (in blue) drawn over the georeferenced Precambrian
Structure Map of North Dakota, with contour interval of 1000 ft.
a
b
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Figure 2.3: Outline of the United States showing depth to the Precambrian basement contours;
contours in red are measured in feet and have a 1000 ft contour interval, and contours in blue are
measured in meters and have no set contour interval.
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Figure 2.4: Topo-to-Raster image of the Precambrian basement in the United States, with darker
areas representing basins and lighter areas representing domes and arches.
Figure 2.5: Second version of the Precambrian surface map of the United States, with the
Hillshade raster overlying Topo-to-Raster image (see Figure 2.4).
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Figure 2.6: Final version of the shaded relief map of the Precambrian surface, with the
following overlays: Cordillera, Appalachians, and Ouachitas in purple, coastal plain in yellow,
and Precambrian outcrops in red.
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Figure 2.7: A 3-D perspective of the Precambrian shaded relief of the Midcontinent. Basin in
foreground is the Arkoma basin.
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Figure 2.8: Overlay of all of the faults and folds collected in the study. Not all of the faults and
folds reach the Precambrian.
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Figure 2.9: The final fault and fold map, showing the major faults and folds known to interact
with the Precambrian basement (in black).
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Figure 2.10: United States outline map with overlays of ‘Precambrian Outcrops’ (in red) and
‘Rift Areas’ (in green): MCR=Midcontinent Rift system, OA=Oklahoma Aulacogen, RF=
Reelfoot Rift, RCG=Rough Creek Graben, RT=Rome Trough, and BBG=Birmingham Basement
graben.
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Figure 2.11: United States outline map overlain by the ‘Domes and Basins’ shapefile:
AB=Appalachian Basin, AnB=Anadarko Basin, ArB=Arkoma Basin, BWB=Black Warrior
Basin, IB=Illinois Basin, MB=Michigan Basin and WB=Williston Basin.
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— CHAPTER 3 —
OBSERVATIONS
______________________________________________________________________________
3.1 Observations of the Shaded Relief Map
An initial examination of the shaded-relief map of the basement topography in the
Midcontinent reveals that the subsurface elevation the Great Unconformity varies significantly.
The central Midcontinent is a broad, low-relief surface, whereas the southern and eastern edges
of the Midcontinent have substantial structural relief. For example, the elevation of the basement
surface in the St. Francis Mountains in the Ozark Plateau is up to 500 m above sea level, whereas
the same surface in the southern end of the Illinois Basin, 100 km to the east, is as much as 7 km
below sea level. Thus, there is locally up to 7.5 km of structural relief on this surface in the
Midcontinent. Comparison of the Midcontinent to other sectors of the cratonic platform (namely,
the Rocky Mountains and the Colorado Plateau) indicates that the Midcontinent does have a
different character. In this chapter, I will discuss details of the shaded relief map, considering
each of the four sectors of the map (the Rocky Mountains; the Colorado Plateau; the
Midcontinent region; and the ‘bordering basins’) separately (Fig. 3.1).
The Rocky Mountains Sector: The Precambrian basement underneath the Rocky
Mountains shows evidence of intense episodes of past tectonic activity. Many of the high,
elongate (50 to 200 km long by 20 to 50 km wide) ranges are cored by Precambrian rocks
brought up on reverse faults (e.g., Yonkee and Mitra, 1993), some of which are exposed at
elevations of up to 4.4 km above sea level. Between the ranges are basins that are down to 6 km
deep, creating extreme structure relief on the Great Unconformity over a relatively short
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horizontal distance. In this region, the amplitude is high (about 10 km) and the wavelength, or
distance between uplifts, is relatively short (80 to 200 km). Notably, trends of ranges and
intervening basins occur in different orientations (north-south, west-east, and northwest-
southeast). The intensity of deformation of the basement, as indicated by structural relief and
relatively short distances between ranges, is greatest in Wyoming and Colorado, or the Laramide
Rocky Mountain province. The distance between Precambrian surface uplifts increases north of
Wyoming and south of Colorado.
The Colorado Plateau Sector: The Colorado Plateau of Arizona, Utah, New Mexico,
and Colorado lies south and west of the Rocky Mountains. Precambrian topography of the
Plateau differs significantly from that of the Rocky Mountains in that the Plateau’s Precambrian
surface displays relatively subdued structural relief, with gentler gradients of the surface. The
region contains monoclinal folds related to subsurface fault reactivation (e.g., Huntoon 1993),
but these are significantly smaller in amplitude (less than 1 km) than those of the Rocky
Mountains Province. The magnitude of structural relief appears to decrease progressively to the
south, toward the Mogollon Highlands of central Arizona, but the lack of structural relief may be
an artifact of lack of data.
The Midcontinent Sector: The basement surface in the interior of the Midcontinent
region is relatively smooth. In general, transitions between high areas (arches and domes) and
low areas (basins) occur relatively gradually, in that the distance between the centers of large
intracratonic basins (e.g., the Williston, Michigan, and Illinois basins) are on the order of 500 to
1000 km. Also, intracratonic basins of the Midcontinent are relatively equant (i.e., circular to
slightly elliptical) in comparison to elongate (very elliptical) basins of the Rocky Mountain
province. Notably, the Williston and Michigan basins are spoon-shaped structures, and the slope
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of the basin surface from the margin of the basin to the interior is very gradual (e.g., a vertical
change of 3 km over a distance of 150 km for the Michigan Basin, in comparison to the Bighorn
Basin in which the basement depth changes by about 10 km over a horizontal distance of 80 km.
The basement topography map emphasizes that, of the intracratonic basins in the Midcontinent,
the Illinois basin appears to be unique, in that its character changes from north to south—the
northern portion of the basin is a broad, spoon-shaped depression, whereas the southern end is a
relatively narrow fault-controlled rift (the Rough Creek graben).
Through most of the Midcontinent (e.g., in Michigan, Wisconsin, Iowa, North Dakota,
South Dakota, Indiana, Kansas, and Nebraska), the basement surface has low-relief, locally cut
by steps that are associated with recognized major faults (Fig. 3.2). For example, the
Proterozoic-age (1.1 Ga) Midcontinent Rift system visibly extends from Minnesota to Kansas.
This feature, despite originating as an extension-related graben, now appears as a positive feature
on the shaded-relief map because its bordering normal faults were inverted during the Paleozoic
to become reverse faults that thrust Precambrian rocks up relative to bordering Paleozoic cover.
The Nemaha Ridge (or uplift) clearly appears as a fault-controlled step in the basement that, at
its north end, intersects the Midcontinent rift. The Ozark Plateau appears on the shaded-relief
map as a rectilinear feature whose northeast corner has been relatively uplifted. Another notable
feature within the Midcontinent region is the Manson impact structure in central Iowa, which
affected the Precambrian surface, producing a central peak in the center of a circular depression.
The ‘Bordering Basins’ Sector: The shaded relief map emphasizes that relatively
narrow, elongate basins (400 km long by 100 km across) border the southern and eastern part of
the Midcontinent region. In effect, these basins define a chain that outlines the Midcontinent
Sector. In order from southwest to northeast, they are: the Permian basin of the Texas/New
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Mexico border, the Anadarko Basin of Oklahoma, the Arkoma Basin of the Oklahoma and
Arkansas, the Reelfoot Rift of eastern Arkansas and southeast Missouri, the Rough Creek
Graben of western Kentucky, and the Rome Trough, which extends from eastern Kentucky,
across West Virginia and Pennsylvania. These basins are locally very deep (up to 7.5 to 10.5
km), and their borders are relatively steep (7 to 10 km of relief over a horizontal distance of 100
km). Published studies indicate that the basins are bordered by and/or incorporate normal faults,
some of which have been inverted.
Along the foreland edge of the Appalachians, a second set of basins, parallel to the
Reelfoot Rift, has formed. This set includes the Birmingham Basement Graben of northern
Alabama (Thomas and Bayona 2005), and the interior portion of the Appalachian basin. The
Birmingham Basement Graben and the Reelfoot Rift together outline a crustal block spanning
Tennessee, and northern Alabama and Mississippi, that appears to have started separating from
the Midcontinent Sector, but did not succeed. This block is bounded on the southwest by the
Oklahoma-Alabama transform (Thomas 2011). The Black Warrior Basin, which is a triangular-
shaped basin in Mississippi and Alabama at the southeastern corner of this block, differs from
the other ‘bordering basins’, in that its border has a relatively gentle gradient that slopes towards
the Gulf of Mexico.
Notably, some of the bordering basins lie adjacent to uplifts where Precambrian rocks are
locally exposed at the surface. Two examples of this occurring are the Ozark Plateau, which lies
adjacent to the Illinois basin, and the Wichita-Arbuckle Mountains, which lies adjacent to the
Anadarko basin (see Figure 3.2). Also of note, some of the basins (e.g., the Arkoma and
Appalachian basins) lie adjacent to thrust belts, suggesting that some of their subsidence reflects
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loading by the emplacement of thrust sheets. In other words, their great depth may reflect the
superposition of thrust-related subsidence on prior rift-related subsidence.
3.2 Observations of Structures, Based on the Attribute Table and Fault/Fold Map
To provide constraints on the orientation and location of faults and folds in the cratonic
platform, I collected data on the structures from the literature and compiled them into an attribute
table, using an Excel spreadsheet (see Table 2.1). The level of detail concerning the structures
varies significantly. Many of the structures exist in the subsurface, so direct measurements on
fault dip, sense of slip and displacement amount is not available. In some cases, the dip-slip
component can be estimated based on structure-contour maps, and in some cases, by study of
seismic-reflection profiles.
I classified the structures, based on their character, into 14 types. Specifically, I refer to
structures that are known only from subsurface data as "inferred basement faults", of which the
type of structure or the sense of slip on that structure is not well known. I estimate
approximately 20% to 30% of the structures involved both faulting and associated folding. If the
fault has known normal-sense displacement, it is classified as a ‘normal fault’, and if it has
known reverse-sense displacement, it is classified as a "reverse fault". Steep faults on which the
sense of slip is not known are called simply ‘high-angle faults.’ I have also distinguished
between left-lateral and right-lateral strike slip faults, suture zones, and shear zones. ‘Suture
zones’ are structures that formed due to two or more Proterozoic terranes or crustal blocks
colliding together.
A plot of fault traces on the map (see Fig. 2.9), indicates that Midcontinent faults and
folds cluster, defining distinct fault-and-fold zones. The distribution of faulting that appears on
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the map could reflect, to some extent, lack of data. But more likely, it indicates that the
Midcontinent consists of relatively intact blocks bounded by fault-and-fold zones. Fault length
on the map varies. The longest faults are tens to hundreds of kilometers long, but some faults are
only a few kilometers long.
I measured the map trends of the structures in order to determine if there are dominant
trends of the structures in the Midcontinent, as had previously been suggested by previous
authors (e.g., Marshak and Paulsen, 1997; Marshak et al., 2003). I then used the StereoNet8
software to produce four rose diagrams for each group of structures (Almendinger et.al. 2013,
Cardozo and Almendinger 2013). The first group of structures involves the categorized normal,
reverse, thrust, high angle thrust, high angle normal, and high angle faults. This first rose
diagram, shown in Figure 3.3, shows two dominant trends in the NE and ENE directions. There
are also three notable trends that should be mentioned, which are in the NNE, NW, and WNW
directions. The second group of structures involves the designated strike slip faults, transform
faults, shear zones, and suture zones. Figure 3.4 reveals two dominant trends (NW and WNW),
and two notable trends (NE and ENE). The third group of structures includes the folds identified
in the study, involving anticlines, synclines, and monoclines. Two dominant trends that are
visible in this fold group (shown in Fig. 3.5) are in the NNW and NNE directions. The final
group of structures includes the ‘inferred basement faults’, which have two dominant trends in
the NW and WNW directions and two notable trends in the NNE and NNW directions (Fig. 3.6).
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Figure 3.1: Precambrian shaded relief map of the United States, with an overlay of the four
domains described in Chapter 3: the Rocky Mountain Sector, the Colorado Plateau Sector, the
Midcontinent Sector, and the Bordering Basins Sector.
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Figure 3.2: Precambrian shaded relief map of the Midcontinent, with overlays of the Cordillera,
Appalachians, and Ouachitas in purple, the coastal plain in yellow, and Precambrian outcrops in
red. MIS=Manson Impact Structure, MRS=Midcontinent Rift System, NR=Nemaha Ridge, and
WM=Wichita Mountains.
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Figure 3.3: Half-Rose Diagram of the normal, reverse, high angle, and thrust faults, showing the
dominant trends (NE and ENE trends) and the notable trends (WNW, NW, and NNE trends).
Figure 3.4: Half-Rose Diagram of the strike slip faults, transfer faults, suture zones, and shear
zones, showing the dominant trends (NW and WNW trends) and the notable trends (NE and
ENE trends).
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Figure 3.5: Half-Rose Diagram of the folds (anticlines, synclines, and monoclines, showing
dominant trends in the NNW and NNE directions.
Figure 3.6: Half-Rose Diagram of the inferred basement faults, showing dominant trends in the
NW and WNW directions and notable trends in the NNW and NNE directions.
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— CHAPTER 4 —
DISCUSSION AND CONCLUSIONS ______________________________________________________________________________
4.1 General Statement
The shaded-relief map of the Great Unconformity (i.e., on the top of the Precambrian
basement surface) provides a fresh image accentuating tectonic features and crustal character in
the Midcontinent. While the features that it shows have been recognized for decades, the
visualization emphasizes relationships that do not stand out so clearly in conventional depictions
of the basement top surface. In particular, is emphasizes that:
• The Midcontinent Sector is, overall, a coherent crustal block. It is delineated on the west by
the Rocky Mountain front, and on the south and east by rift basins, some of which have been
pushed down to greater depth by subsequent thrust-loading. The pattern of rifting stands out
on the map, and supports the hypothesis that during the Proterozoic separation of Laurentia
from Pannotia, a set of failed rifts formed inboard of the ultimately successful rift.
• In the Midcontinent Sector, basement topography is not controlled by the position of
Proterozoic sutures. Specifically, comparison of the Whitmeyer and Karlstrom map (see Fig.
1.2) with the basement topography map shows that there is little if any correlation between the
major Precambrian province boundaries and basement topography. This implies that sutures,
whose development is accompanied by prograde metamorphism and associated
recrystallization, do not behave as long-lived weaknesses.
• Proterozoic rifts do influence basement topography in the Midcontinent Sector. This is evident
by the structural relief associated with the Midcontinent Rift, the Nemaha Ridge, and the major
basins bordering the Midcontinent block. Therefore, the normal faults generated by rifting do
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remain as long-lived weaknesses as suggested by Marshak et al. (2003). The dilation during
normal faulting may provide access of water to mid-crustal rocks, leading to retrograde
metamorphism and the production of weak phyllosilicates (e.g., chlorite); these zones have
never annealed.
• The distance between sedimentary basins in the Midcontinent Sector and the gentle slope
gradients of basement leading into the basins contrasts markedly with that of the Rocky
Mountain Sector, but is not that different from the Colorado Plateau Sector. Clearly, the crust
of the Rocky Mountains region has behaved differently than other regions of cratonic platform
crust during convergent tectonism. Specifically, the Laramide shortening of the Rocky
Mountains Sector had significantly different consequences than the Alleghanian shortening of
the Midcontinent block. This either reflects the difference between the consequences of
shallow subduction and the consequences of continental collision, or a difference between the
character of the crust of the two regions prior to shortening.
• The Bordering Basins on the south and east of the Midcontinent Sector are discontinuous, in
that they are separated along strike by distinct crustal bridges of unrifted crust between them.
4.2 Implications of the Shaded-Relief Map to Interpreting Intraplate Seismicity
Using data collected from the U.S. Geological Survey, I constructed a shapefile showing
the most recent earthquake epicenters (from January 1979 to April 2013) throughout the cratonic
platform. To emphasize the spatial distribution of events, rather than the energy release by
cumulative earthquakes in an area, all epicenters are shown by the same dot size. I overlaid the
earthquake epicenter shapefile over the shaded relief map to see if any correlation exists between
epicenter distribution and basement structure (Fig. 4.1). The map clearly shows that the vast
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majority of events occur in the Bordering Basins Sector. Relatively few events occur in the
Midcontinent Sector. Those events that do occur in the Midcontinent Sector appear to be aligned
in semi-distinct zones that generally do not coincide with known basement-penetrating faults.
The three areas with the greatest concentration of earthquake epicenters (i.e., areas with
the most seismicity) are in central Oklahoma, in the New Madrid seismic zone/Reelfoot Rift
area, and in the East Tennessee seismic zone. The central Oklahoma seismic zone coincides
with several major faults (e.g., the Central Oklahoma fault zone and the Meers/Criner fault
system). The Central Oklahoma fault zone, which trends north-south, appears to be the southern
extension of the Nemaha uplift and delineates the steep gradient in basement topography at the
western edge of a crustal bridge between the Arkoma and Anadarko basins. Both the Criner and
Meers faults trend northwest-southeast and lie in the deepest part of the Anadarko basin. The
New Madrid seismic zone in the Reelfoot Rift occurs in the eastern boundary of the western
Tennessee crustal block, and appears continuous with a line of seismicity that extends northeast
to Lake Ontario. The zone also coincides with the steepest gradient in the slope of the basement
surface. The difference in Precambrian topographic relief from the deepest part of the Illinois
basin to the top of the Ozark Plateau is about 7.5 km. This is also the area where the Precambrian
topography is very steep, although the faulting patterns are not well known. The East Tennessee
seismic zone, in contrast, does not appear to correlate with a steep basement gradient. In fact,
structure associated the East Tennessee seismic zone is relatively subtle; the zone follows the
trend of the New York-Alabama Lineament (Powell et.al., 1994).
Notably, there are distinct gaps in seismicity within the Midcontinent region, even in
places where there are faults. One example is the central part of the Arkoma basin, which is the
region that lies between central Oklahoma and the New Madrid seismic zones. According to
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cross-sections and maps of this region (Arbenz, 2008; Csontos et.al., 2008), an extensional fault
system exists in the subsurface. Another example lies between the Rough Creek Graben and the
Rome Trough, in central Kentucky. This area is a crustal bridge between the two rift systems,
and contains the Grenville suture. Using information from Hickman (2011), I have extended the
rift-bounding faults to connect the two rift systems.
4.3 Implications of the Shaded Relief Map to Interpreting Crustal Inhomogeneities
Both gravity and magnetic anomaly maps provide insight into crustal differences within a
region. The use of both of these maps can help to identify small-scale and large-scale structures,
in the subsurface and at the land surface. Comparing the gravity and magnetic anomaly maps to
the Precambrian basement shaded-relief map can enhance interpretation of where basement
structures are located and possibly how they are derived. Gravity maps, in particular isostatic
gravity maps, provide images of mass anomalies within the crust—where positive gravity
anomalies occur, there is an excess in mass, and where negative gravity anomalies occur, there is
a deficit in mass. Figure 4.2 compares the isostatic gravity map of the United States to the
shaded-relief map of the basement top surface, and reveals clear correlations. For example, the
Midcontinent Rift System and the Meers/Criner faults appear as a strong positive anomaly
relative to the surrounding area. Another example is the western part of the Arkoma basin,
which is a strong negative anomaly in the isostatic gravity map.
Magnetic anomaly maps can highlight areas where rocks contain a relatively large or
relatively small concentration of magnetic minerals. A comparison between the magnetic-
anomaly map and the shaded-relief map of the basement top surface is shown in Figure 4.3.
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One clear positive anomaly in the magnetic map is a portion of the Midcontinent Rift System
(from Minnesota through Iowa).
4.4 Conclusions
The construction in ArcGIS of a 3-D shaded relief map of the Great Unconformity, and of
faults and folds, in the cratonic platform is challenging because the data necessary to produce
these maps is not easily accessible, and occurs in a variety of different forms. The maps provide
useful insight into architecture of regional-scale structures and suggest relationships among the
Precambrian basement topography, faulting, and seismicity. Specifically, the shaded-relief map
emphasizes that the cratonic platform includes distinct sectors that differ from one another in
terms of structural relief, gradients in the slope of the basement surface, and the wavelength of
uplifts and basins. The map of fault-and-fold zones emphasizes that the structures are not
randomly oriented, but concentrate in distinct sets. Comparison of the maps to the distribution of
earthquake epicenters emphasizes that most seismicity of the cratonic platform east of the Rocky
Mountain front concentrates in the rift-controlled basins that lie along the southern and eastern
margins of the low-relief Midcontinent sector.
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Figure 4.1: Precambrian shaded relief map of the Midcontinent showing earthquake epicenters
(red circles). ETSZ=East Tennessee Seismic Zone and NMSZ=New Madrid Seismic Zone.
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Figure 4.2: Comparison of an Isostatic Gravity map (above) to the Precambrian shaded relief
map (below).
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Figure 4.3: Comparison of a magnetic map (above) to the Precambrian shaded relief map
(below).
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