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Theodore Roosevelt National Park
Geologic Features & Processes
This section provides descriptions of the most prominent and distinctive geologic features
and processes in Theodore Roosevelt National Park.
View of Badlands from Oxbow Overlook. Theodore Roosevelt National Park is an ideal setting for the development of
badlands topography. Badlands formation with its high-drainage density is probably the most distinctive geologic process in the park.
NPS photo by Dave Krueger.
Myriad natural features contribute to the development
of badlands topography at Theodore Roosevelt National
Park (figure 13). Among these factors are intense seasonal
storms; relatively soft, easily erodible rocks; and the
absence of dense stabilizing vegetation. Badlands
formation is probably the most distinctive geologic
process occurring in the park. Badlands topography is
discussed in detail in the "Geologic Setting," "Coal
Resources and Mining," and "Geologic History"
sections. Other features and processes of the landscape
at Theodore Roosevelt National Park are presented in
alphabetical order here.
Concretions and Cap Rocks
Concretions are hard, compact aggregates of mineral
material. They precipitate out of solution from
groundwater. Prior to the regional erosion of the Little
Missouri badlands, groundwater slowly seeped through
the layers of sediments for millions of years. This water
contained minerals, which precipitated then cemented
around sand grains or other nucleus (e.g., shell or bone
fragments). Some concretions are remarkably large,
especially in the North Unit. For example, along the
scenic drive near Squaw Creek Campground, large,
round concretions called "cannonballs" have eroded out
of the surrounding rock and accumulated at the base of
the cliffs (Murphy et al. 1999). Erosion- resistant
concretions preferentially weather out of the basal
sandstone of the Sentinel Butte Formation. Many of
these concretions form the resistant caprock of pedestals
(also known as rain pillars or hoodoos). These cap rocks
are flat, hard, sandstone slabs that protect the underlying
sediments from erosion. Eventually the slabs will tilt or
fall off the pedestals and the remaining soft sediments
will quickly erode away (Murphy et al. 1999).
Large boulders once transported by glaciers now rest
scattered on bedrock surfaces different from their own
compositions, a position which testifies to the
effectiveness of glacial erosion and transport. Many
erratics have glacial striations or scratches that formed as
they were dragged against bedrock during glacial
movement. Glacial erratics of granitic and carbonate
compositions are the primary evidence of glaciation in
Theodore Roosevelt National Park (Biek and Gonzalez
2001). They occur in the North Unit and are thought to
mark the maximum extent of glacial ice in this part of the
Missouri Plateau. Most of the erratics are 1 to 2 feet (0.3
to 0.6 m) in diameter, but some are almost 5 feet (1.5 m) in
diameter (Biek and Gonzalez 2001).
Windblown deposits such as loess and sand cover large
areas of the Great Plains. This wide eolian distribution
throughout the region was recognized almost as soon as
geological exploration began in the late 19th century
(Emmons et al. 1896; Gilbert, 1896). Though sporadically
mapped and underrepresented on most geologic maps,
investigators of Quaternary climate change have renewed
scientific interest in loess and eolian sand (Madole 1995).
Lengthy loess sequences, such as those present on the
northern Great Plains, contain detailed records of
Quaternary glacial- interglacial cycles. Scientists consider
these to be a terrestrial equivalent to the foraminiferal
oxygen isotope record of deep- sea sediments, which
document long- term climate change (Muhs et al. 1999).
Loess is also a direct record of atmospheric circulation.
Information on paleowind from loess in the geologic
record can test atmospheric general circulation models
(Muhs et al. 1999). In addition, widespread eolian
deposits are important sources of information for
reconstructing the history of aridification in the interior
of North America during the Quaternary (Madole 1995).
In North Dakota, sediments deposited during the
Pleistocene Epoch (1.8 million years ago to 11,800 years
ago) belong to what geologists call the Coleharbor
Group. Sediments deposited during the Holocene Epoch
(11,800 years ago to present) belong to the Oahe
Formation. Loess is present in both of these units.
Although most upland surfaces are veneered with loess,
and dune sands are locally present, neither were mapped
by Biek and Gonzalez (2001). Loess is difficult to map
where it is thin (less than 5 feet [1.5 m]) or overlies rocks
that weather to residuum that is texturally similar to
loess, as is the case in much of the badlands region
Oxbow Overlook. The Little Missouri River makes a huge bend as it turns east in the North Unit. Eventually, the river will
abandon the large U-shaped portion of the channel and flow in a more direct course, leaving an oxbow. NPS Photo by Dave Krueger.
The erosion and deposition of sediments associated with
active streams constantly change riparian ecosystems. In
the valleys at Theodore Roosevelt National Park, streams
tend to meander-widening their bends and occasionally
short- circuiting them. This leaves the abandoned
meanders as oxbow lakes, which slowly fill in with
sediment (figure 14). Remnants of these filled lakes
record this process as ongoing along the Little Missouri
River (Laird 1956). Today, the Little Missouri River
makes a wide bend as it turns east in the North Unit.
Eventually, the river will abandon the large U- shaped
portion of the channel in favor of a more direct route,
leaving a stranded oxbow (Murphy et al. 1999).
Pediments are broad, erosional, low- angle bedrock
surfaces, extending out from highland margins. They are
correlative with arid and semiarid conditions and are
associated with landscape development over time.
However, the connection between pediments and
climate is still a subject of debate among
geomorphologists (Summerfield 1991).
In Theodore Roosevelt National Park pediments occur
at the bases of major escarpments and the heads of major
drainages. In the South Unit, the largest pediment
surfaces are located at the foot of the eastern
escarpment, in the vicinity of Boicourt and Sheep Butte
springs, and at the heads of Sheep, Paddock, and Jones
creeks. In the North Unit, large pediments occur along
Squaw Creek and the Little Missouri River (Biek and
Gonzalez 2001). Pediments in the park are complex
assemblages in which erosional surfaces have been
buried by sheetwash sediment or reworked eolian
material (see "Sheetwash Erosion" and "Eolian
Deposits" sections). These conditions make
interpretation and study of landscape development via
pediments difficult in the park.
Sand and Gravel
Sand and gravel are present in alluvial deposits (units
QTa and Qt on the geologic map) in the North and South
units of Theodore Roosevelt National Park. These
deposits occur as a veneer capping high- level plateaus
near the Little Missouri River. A thick mantle of
Holocene loess often covers these deposits.
Sand and gravel have been mined by private entities from
at least two places inside park boundaries. The first
location, at the eastern edge of the Petrified Forest
Plateau, probably provided sand and gravel for road
material (used locally) and the trail leading to the top of
Petrified Forest Plateau (Biek and Gonzalez 2001). In
2002 the National Park Service acquired the second
location-a 5,510- acre (2,230 ha) land acquisition
containing 960 acres (389 ha) of sand and gravel
potential. This property was previously owned by Ken
and Norma Eberts who periodically sold gravel from the
site to Billings County for road improvements. The
National Park Service extinguished sand and gravel
rights in conjunction with the buyout of the parcel of
land (Phil Cloues, NPS Geologic Resources Division,
written communication, October 18, 2004).
Shelter at Riverbend Overlook. The Civilian Conservation Corps used medium-grained, cross-bedded sandstone from a
local quarry to construct various structures in the park, such as this shelter in the North Unit. NPS photo by Dave Krueger.
Sometime before 1957, sand and gravel deposits were also
mined from another location atop the plateau
immediately east of Medora. This currently unreclaimed
pit is located just outside the park's boundary. A large
landslide is present on the steep slope just west of the pit
(Biek and Gonzalez 2001).
Sandstone and Silcrete
During the 1930s, the Civilian Conservation Corps used
medium- grained, cross- bedded sandstone from a
quarry near Theodore Roosevelt National Park to
construct various structures in the park. For example, rough blocks of what is likely Sentinel Butte sandstone
surround the perimeter of the shelter at the Riverbend
Overlook in the North Unit (figure 15). Large blocks of
the same sandstone and silcrete blocks of the Taylor bed
(upper unit of the Bear Den Member of the Golden
Valley Formation) line the path down to the shelter.
Silcrete is silica- cemented sand and gravel. Investigators
are uncertain whether these stones were quarried in the
park. A 1937 photo caption implies that the quarry was in
the North Unit, but a longtime park employee was
certain that the quarry was located 25 miles (40 km)
southwest of the park in an area called Flat Top Butte
(Biek and Gonzalez 2001). At present, investigators have
not seen any evidence of sandstone quarrying within
Theodore Roosevelt National Park (Biek and Gonzalez
In 1938, the Emergency Relief Association built the old
South Unit entrance station. This check station, adjacent
stone fence, and privy are made from cut and dressed
sandstone blocks of unknown origin. A pylon
constructed of this same stone upon which the park's
name hangs was originally at the check station. It was
moved to the Painted Canyon Visitor Center in 1968
(Biek and Gonzalez 2001).
In densely vegetated environments, the presence of
stabilizing plant roots usually prevents rills from
developing. By contrast, in arid and semiarid
environments such as Theodore Roosevelt National
Park, where precipitation tends to fall in intense bursts,
erosional features such as rills and gullies naturally
develop. The slopes of many of the buttes in the park are
extremely gullied or minutely dissected by running
water. Rill- and- gully erosion occurs particularly in the
basal sandstone of the Sentinel Butte Formation.
The movement of water across a slope surface is called
sheetwash. This is a general term because, unlike a sheet,
water flow is never of uniform depth due to
microtopography of hillslope surfaces. Sheetwash
typically grades into channelized flow as the water
movement becomes progressively more concentrated
into particular downslope routes. For this reason, the
distinction between "sheet flow" and "channelized flow"
is sometimes indefinite. Nevertheless, sheetwash flowing
from the sides of a butte in the badlands will typically
concentrate into tiny rills as a result of irregularities of
the slope. Some of these rills break down between
rainfall events; others enlarge into gullies that deepen
and widen with each rain. As rills develop into gullies,
they erode back into the butte until two rivulets meet at
their heads. The divide between them becomes very
narrow and more succeptible to rapid weathering and
erosion. Eventually, the divide between the two rivulets
degrades entirely, separating a small portion of the butte
side from the main butte. Thus, the butte erodes
incrementally by both the action of running water and by
this process of segmentation (Laird 1956).
Changes in channel gradient, discharge, or sediment load
can cause a river to incise its floodplain and form
terraces. River terraces also can be cut into previously
deposited alluvium or bedrock. Following incision, the
original floodplain is abandoned and left as a relatively
flat bench (terrace), which is separated from the new
floodplain below. River terraces are inclined
downstream but not always at the same angle as the
active floodplain. The valley wall of an entrenching river
may contain a vertical sequence of terraces. The lowest,
youngest terrace may retain traces of floodplain
morphology, whereas the highest, oldest terrace may be
heavily weathered. Terraces can be either paired or
unpaired. Paired terraces on opposite sides of the river
form when vertical incision occurs more rapidly than the
lateral migration of the channel. Unpaired terraces form
when rapid lateral shifting of the channel occurs and the
river cuts terraces alternately on each side of the valley
In general, geomorphologists differentiate terraces and
assign ages based on height above the modern stream level. For example, in the South Unit, alluvial terrace
deposits (unit Qt on the geologic map) are subdivided
into four mappable units (from youngest to oldest): Qt1,
Qt2, Qt3, and Qt4.
Terraces in Theodore Roosevelt National Park record
changes caused by a major climatic cooling event during
the Pleistocene Epoch. This cooling caused the advance
of large continental ice sheets from northern latitudes. In
pre- glacial time, the Little Missouri River flowed north
toward Hudson Bay. However, when glaciers advanced
southward, local north- flowing streams were blocked;
the drainages of the Little Missouri and Yellowstone
rivers were diverted along the edge of the ice front. This
ice- marginal drainage eventually became the present
Missouri River, which the Little Missouri River flows
into. The rate of erosion and downcutting of the Little
Missouri River was not constant: as erosion and
deposition continued, the river cut a series of terraces,
remnants of which can be seen in the park (Harris and
Biek, R. F., and M. A. Gonzalez. 2001. The geology of
Theodore Roosevelt National Park, Billings and
McKenzie counties, North Dakota. Miscellaneous Series
86, text (74 p.), 2 pls. (scale 1:24,000). Bismarck: North
Dakota Geological Survey.
Harris, A. G., and E. Tuttle. 1990. Geology of national
parks, 4th ed. Dubuque, IA: Kendall/Hunt Publishing
Laird, W. M. 1956. Geology of the North Unit, Theodore
Roosevelt National Memorial Park. Bulletin 32.
Bismarck: North Dakota Geological Survey.
Madole, R. F. 1995. Spatial and temporal patterns of late
Quaternary eolian deposition, eastern Colorado,
U.S.A. Quaternary Science Reviews 14:155-177.
Muhs, D. R., J. B. Swinehart, D. B. Loope, J. N.
Aleinikoff, and J. Been. 1999. 200,000 years of climate
change recorded in eolian sediments of the High
Plains of eastern Colorado and western Nebraska. In
Colorado and adjacent areas, Field Guide 1, eds. D. R.
Lageson, A. P. Lester, and B. D. Trudgill, 71-91.
Boulder, CO: Geological Society of America.
Murphy, E. C., J. P. Bluemle, and B. M. Kaye. 1999.
Roadlog guide for the South & North units, Theodore
Roosevelt National Park. Educational Series 22. 2nd
printing. Bismarck and Medora, ND: North Dakota
Geological Survey North Dakota Geological Survey,
and Theodore Roosevelt Nature and History
Summerfield, M. A. 1991. Global geomorphology: An
introduction to the study of landforms. New York: John
Wiley & Sons, Inc.