Kansas is located in the center of a continent. It
is at least a thousand miles from any ocean, but its geology is dominated
by oceanic events. There are no towering mountain ranges or volcanoes,
but the range of elevations
in Kansas is similar to that of mountainous Kentucky. Many mountaineers
have stood in amazement atop Kansas' Mt.
Sunflower. Though it lacks dramatic variations of lava and
mountain, Kansas geology is more complex than it might seem. We will
uncover the secrets locked in the rocks.
The following table provides information about how Kansas geology fits into the geologic timescale. Scroll down and read the table from the bottom up.
The statewide physiographic map shows how the sedimentary deposits are exposed on the surface and how the surface relates to the stratigraphic column. The stratigraphic cross section is taken along the line shown as A - A'. This line approximates the route of I-70 across the state.
The following table provides information about how Kansas geology fits into the geologic timescale. Scroll down and read the table from the bottom up.
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Kansas is in a relatively stable
region so the sedimentary layers are almost always older as you go deeper,
just like the timetable. With the exception of glacial erratics in
NE Kansas and a few 100 million year old volcanic domes that outcrop just
north of Manhattan, all surface rocks in the state are sedimentary.
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The statewide physiographic map shows how the sedimentary deposits are exposed on the surface and how the surface relates to the stratigraphic column. The stratigraphic cross section is taken along the line shown as A - A'. This line approximates the route of I-70 across the state.
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The trip begins in Douglas County. The second
county from the right along A-A'. We will observe Pennsylvanian formations
and glacial erratics. (Note the limits of the Kansas glacier). Moving west,
line A-A' transects Permian, Cretaceous, then Cenozoic deposits. Note
the elevation gain as you travel west from A' - A across the state.
The highest point in Kansas, very near pt. A, is 4,039 ft. Also note
the age of the surface deposits getting younger as you go west. In
Western Kansas there can be as much as 8000 ft. of sedimentary deposits above
the Precambrian system that underlies the state. |
Sedimentary Depositional
Regimes:
The region now occupied by Kansas was mostly under a shallow inland sea during much of its geologic history (see timetable above). There were many transgressive and regressive events in which sea level rose and fell. This led to an oscillating shoreline. One spatial point would be subjected to repeatedly different ocean depths, and different depths are associated with different depositional regimes.
These repeated, alternating deposits are called cyclotherms. These cyclotherms have recognizable patterns that geologists have called formations.
"The sedimentary rocks of Kansas have been divided into approximately 170 formations each named for the geographic locality where it was first recognized and described." (Kansas Geology ; Buchanan)
The layers that make up these formations are identified as members. The members that make up the formations exist in the same sequence wherever that particular formation is found. Some of these formations cover hundreds of square miles with widely separated outcrops. The Pennsylvanian Oread Formation of Kansas is also found in Iowa, Missouri, and Oklahoma, but it is always recognized by its particular sequence of members.
The Permian stratigraphic column of a region in the Flint Hills further illustrates the complex depositional regimes of Kansas.
The marine deposition regime held sway until near the end of Cretaceous times. The uplift of the Rocky Mountains raised Kansas out of the sea. During the Tertiary period, for about 60 million years, streams carried materials from the eroding Rocky Mountains into Western Kansas. These streams would get choked with rock debris and overflow out of the valleys, leaving a vast deposit of sand and gravel. The Quaternary period is highlighted by several incursions of Pleistocene Ice Age glaciers into NE Kansas. These glaciers left behind deposits carried in from the north, including Precambrian boulders found nowhere else in the state. As the glaciers retreated, vast areas of mud and silt were exposed. As they dried, strong north winds blew up dust storms that would have dwarfed the 1930's dustbowl storms. In parts of Eastern Kansas, the deposits of windblown loess are more than 100 ft. thick. Also during this period, prevailing Westerlies blew in huge duststorms from the eroding Rockies. Thick layers of windblown loess were deposited over the earlier deposits of sand and gravel. The uneroded remnants of these storms can be seen in the table-flat High Plains of Western Kansas. The sand and gravel deposits below the loess form the High Plains (Ogallala) Aquifer.
Landscapes:
"The Kansas landscape was formed by alternating periods of deposition and erosion. This landscape divides regions of Kansas according to physical geology, or physiography. Each region is different, and that difference is determined largely by geology, along with other factors such as climate."
(From the Kansas Geological Survey)
The region now occupied by Kansas was mostly under a shallow inland sea during much of its geologic history (see timetable above). There were many transgressive and regressive events in which sea level rose and fell. This led to an oscillating shoreline. One spatial point would be subjected to repeatedly different ocean depths, and different depths are associated with different depositional regimes.
- Near Shore: Erosional materials from the continent are deposited in the high-energy environment where waves are contacting the shore. The larger diameter, heavier grains are deposited and the finer grain materials stay suspended. This leads to sandy beaches and barrier islands that will become sandstones in the stratigraphic column.
- Off Shore: As the water gets deeper and further from shore, it becomes calmer. This lower energy situation allows the smaller diameter, lighter suspended particles to drop out. They form a muddy bottom that will become shale in the stratigraphic column.
- Open Marine: Microscopic algae and plankton
die and sink to the bottom, creating a biogenic limey ooze on the ocean
floor that will become limestone in the stratigraphic column. Changes
in ocean chemistry can also lead to deposits of calcium carbonate. Increased
carbon dioxide levels lead to a higher solubility for calcium carbonate.
If carbon dioxide levels drop, then calcium carbonate often precipitates
out, creating a limey ooze of chemical origin.
These repeated, alternating deposits are called cyclotherms. These cyclotherms have recognizable patterns that geologists have called formations.
"The sedimentary rocks of Kansas have been divided into approximately 170 formations each named for the geographic locality where it was first recognized and described." (Kansas Geology ; Buchanan)
The layers that make up these formations are identified as members. The members that make up the formations exist in the same sequence wherever that particular formation is found. Some of these formations cover hundreds of square miles with widely separated outcrops. The Pennsylvanian Oread Formation of Kansas is also found in Iowa, Missouri, and Oklahoma, but it is always recognized by its particular sequence of members.
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| Courtesy of 'Kansas Geology' ; Buchannan |
Photo courtesy of KGS |
The Permian stratigraphic column of a region in the Flint Hills further illustrates the complex depositional regimes of Kansas.
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There is a lack of sandstone in the cyclotherms
here. This is presumably because this region was far from shore and
never had the beach deposition that would have led to sandstone. This
leaves many alternating layers of deeper water limestone deposits and shallower
water deposits of shale. |
| Stratigraphic columns courtesy
of KGS |
The marine deposition regime held sway until near the end of Cretaceous times. The uplift of the Rocky Mountains raised Kansas out of the sea. During the Tertiary period, for about 60 million years, streams carried materials from the eroding Rocky Mountains into Western Kansas. These streams would get choked with rock debris and overflow out of the valleys, leaving a vast deposit of sand and gravel. The Quaternary period is highlighted by several incursions of Pleistocene Ice Age glaciers into NE Kansas. These glaciers left behind deposits carried in from the north, including Precambrian boulders found nowhere else in the state. As the glaciers retreated, vast areas of mud and silt were exposed. As they dried, strong north winds blew up dust storms that would have dwarfed the 1930's dustbowl storms. In parts of Eastern Kansas, the deposits of windblown loess are more than 100 ft. thick. Also during this period, prevailing Westerlies blew in huge duststorms from the eroding Rockies. Thick layers of windblown loess were deposited over the earlier deposits of sand and gravel. The uneroded remnants of these storms can be seen in the table-flat High Plains of Western Kansas. The sand and gravel deposits below the loess form the High Plains (Ogallala) Aquifer.
Landscapes:
"The Kansas landscape was formed by alternating periods of deposition and erosion. This landscape divides regions of Kansas according to physical geology, or physiography. Each region is different, and that difference is determined largely by geology, along with other factors such as climate."
(From the Kansas Geological Survey)
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| Map Courtesy of KGS |
The field trip will pass through several regions:
Osage Cuestas: Most of the surface in this region is Pennsylvanian origin, about 300 million years old. It is characterized by low rolling hills. Some of the hills have escarpments on one side and a gentler slope on the other.
Osage Cuestas: Most of the surface in this region is Pennsylvanian origin, about 300 million years old. It is characterized by low rolling hills. Some of the hills have escarpments on one side and a gentler slope on the other.
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| Photos courtesy of |
John Charlton KGS |
Glaciated Region: This region
has deposits from the terminal end of ice-age glaciers that retreated and
left behind materials carried in from the north.
Oil is still an important part of the Kansas economy and small
pump jacks can be seen scattered about the state.
There are also natural gas deposits. The Hugoton field in SW
Kansas is one of the largest in the world. Coal can be found in the Pennsylvanian
rocks of the eastern third of the state with a few beds found in Permian
rock.
Evaporites: At several locations and times, arms of the Permian sea dried up. As the water became less, the dissolved minerals precipitated out and sank to the bottom where they were covered up. Less soluble salts, such as gypsum (calcium sulfate) precipitate out first. More soluble salts, such as halite (table salt or sodium chloride) precipitate out later. This left Kansas with significant deposits of these evaporites.
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| Photo courtesy of KGS |
Flint Hills Uplands: The Flint Hills
get their name from the hard flint deposits that are incorporated into some
of the limestone layers here. Flint or 'chert' is a type of rock consisting
of microscopic crystals of SiO2. The source of these microscopic quartz
crystals is not understood for this region, but these crystals did sediment
out in some of the limestone deposits. The deposition of cherty limestone
is associated with maximum depth of transgressive events as described by
James S. Aber:
After many transgression/regression events, the regime changed drastically with the rising of the Rocky Mountains. Kansas arose from the sea and became exposed do a completely different deposition/erosion environment. As the ancient deposits began to erode away, the cherty limestone resisted erosion, while the shales eroded more easily. This led to the series of flat topped slopes that we can see today.
Arkansas River Lowlands: This region is
essentially the floodplain of the Arkansas River (this is
pronounced 'R-Kansas river in Kansas and R-Ken-Saw river everywhere
else). There are several interesting features we will see on
this trip, the sand-sage prairie and Cheyenne Bottoms Wetlands.
Geologic Resources:
Fossil Fuels: Kansas has an important place in the history of scientific oil exploration. In 1912 Erasmus Haworth was doing a detailed mapping of the surface geology for the Kansas Geologic Survey. He discovered a large upward bulging anticline near El Dorado Kansas. He knew that other oil strikes had been associated with anticlines, so he recommended the El Dorado anticline for oil exploration. In 1915 they struck oil, and the El Dorado field became the first major oil field discovered by the scientific method of detailed geologic mapping of surface rocks. By 1918 the El Dorado field accounted for 9% of global oil production. ( Information for the El Dorado field courtesy of KGS Open-file report 2001-41)
Cherty limestone: tan or light gray, platy to massive, fossiliferous limestone or chalky limestone; scarce to abundant nodules or beds of chert; locally may display algal banding or cross bedding; diverse fossils including many echinoids and fusulinids. Examples: Neva, Cottonwood, Crouse, Threemile, Florence, Stovall. Environment: far offshore, shallow sea of near-maximum transgression. [Underlines are my own.]
( Geology, Geomorphology, and Geohydrogology of the Flint HillsEast-Central Kansas
James S. Aber academic.emporia.edu/aberjame/field/flint/flint )
After many transgression/regression events, the regime changed drastically with the rising of the Rocky Mountains. Kansas arose from the sea and became exposed do a completely different deposition/erosion environment. As the ancient deposits began to erode away, the cherty limestone resisted erosion, while the shales eroded more easily. This led to the series of flat topped slopes that we can see today.
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| Konza Landscape photos courtesy
of Konza LTER website: |
http://www.konza.ksu.edu/ |
Smoky Hills: The Smoky Hills are
Cretaceous in origin. They change in nature from east to west. The
Eastern Hills are capped with Dakota Sandstone that was deposited 100 million
years ago. The Middle Hills are capped with limestone. This
region is often called 'Post-Rock Country' because the scarecity of trees
forced the early farmers to quarry limestone for fenceposts. The Western
Smoky Hills are a region where the 80 million year old Niobrara Chalk formations
were covered. The covering eroded away leaving exposed formations
and outcroppings of fossil-bearing chalk.
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| Eastern Smokys;Dakota Sandstone Cap |
Middle Smokys; fencepost country |
Western Smokys; Niobrara outcrop |
| Courtesy of KGS |
Courtesy of KGS |
Courtesy of Tom Geyer |
High Plains: The High Plains are the flatlands
of Western Kansas. These are the Cenozoic deposits that have been
held in place. Much of this region overlies the Ogallala formation
that is part of the huge interconnected High Plains Aquifer.
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| Abandoned limestone farmhouse on the high plains |
Center-pivot irrigation utilizing the High Plains
Aquifer |
| Courtesy of KGS |
Courtesy of Tom Geyer |
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| Sand-sage photo by Tom Norman |
Courtesy of KGS |
Fossil Fuels: Kansas has an important place in the history of scientific oil exploration. In 1912 Erasmus Haworth was doing a detailed mapping of the surface geology for the Kansas Geologic Survey. He discovered a large upward bulging anticline near El Dorado Kansas. He knew that other oil strikes had been associated with anticlines, so he recommended the El Dorado anticline for oil exploration. In 1915 they struck oil, and the El Dorado field became the first major oil field discovered by the scientific method of detailed geologic mapping of surface rocks. By 1918 the El Dorado field accounted for 9% of global oil production. ( Information for the El Dorado field courtesy of KGS Open-file report 2001-41)
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Oil pump and collecting tank photos courtesy of |
John Charlton KGS |
Evaporites: At several locations and times, arms of the Permian sea dried up. As the water became less, the dissolved minerals precipitated out and sank to the bottom where they were covered up. Less soluble salts, such as gypsum (calcium sulfate) precipitate out first. More soluble salts, such as halite (table salt or sodium chloride) precipitate out later. This left Kansas with significant deposits of these evaporites.
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| Salt Mine Photo courtesy of KGS |
Water: Much of the ground water is considered
geologic or 'fossil' water because it is extracted from aquifers that are
no longer being recharged. This is essentially mining a geological
resource. This issue will be discussed further in the Hydrology section.
