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Arkansas River Lowlands and Wellington-McPherson Lowlands: Rocks and Minerals (From the Kansas Geological Survey-1999 <http://www.kgs.ku.edu/Extension/lowlands/AL_factsheet1.pdf>) “The Arkansas River Lowlands and
the Wellington-McPherson Lowlands, though separated into different
physiographic regions, are geologically similar. Both regions are relatively
flat alluvial plains, made up of sand, silt, and gravel that was dumped by
streams and rivers. The Arkansas River Lowlands is made up of rocks deposited
by the Arkansas River during the last 10 million years as the river flowed
through Kansas from its source high in the Rocky Mountains. In the Rockies,
the Arkansas is supplied with runoff, snowmelt, and rock debris that weathers
from the mountains, but as it moves out onto the High Plains, it receives
little in the way of additional water. In fact, it loses water to its sandy
riverbed. As its flow decreases, the river’s ability to carry sediments also
diminishes and it begins to dump its sediment load. It changes from a
degrading stream (one that cuts downward in its channel) to an aggrading
stream (one that builds up the riverbed).
The Wellington-McPherson Lowlands of south-central Kansas is also
developed on alluvial deposits. This sand, silt, and gravel was eroded from
slightly older rocks in the High Plains to the north, then carried by streams
flowing south into the Arkansas River between one and two million years ago,
during the Pleistocene Epoch. The
Wellington-McPherson Lowlands sit on top of one of the largest salt deposits
in the world. Known as the Hutchinson salt bed, this deposit underlies much
of central Kansas and is as much as 400 feet thick in places. Another
important underground feature of the Wellington McPherson Lowlands is the
Equus Beds aquifer. The Equus Beds is made up of thick (more than 250 feet)
deposits of silt, sand, and gravel, in many places saturated with water. This
aquifer is an important source of water for Wichita, McPherson, Newton, and
other communities in this region. These Pliocene- and Pleistocene- age
deposits were named for fossils of Ice Age horses that were found among the
unconsolidated deposits (equus is the Latin word for horse). Sand
dunes, formed by wind and water, occur in many places in both regions. Most
of these dunes are covered with grass and other vegetation, which keeps the
sand from shifting. Such sand dunes are considered inactive—that is, they are
no longer moving in response to wind and water.” Common Rocks and Minerals
“Gypsum.—A common mineral in Kansas, gypsum is
made up of calcium sulfate with two molecules of water (CaSO4•2H20). (Calcium sulfate without water is the
mineral anhydrite.) It is colorless or white to light gray (or, rarely,
bright red), and is so soft that it can be scratched by a fingernail. Gypsum
is divided into three varieties. The first, selenite, consists of flat,
clear, diamond-shaped crystals. The second variety is called satin spar. It
is white or pink, fibrous, and has a silky luster. It is found as thin layers
in beds of rock gypsum and in certain shales. The third variety,
called massive or rock gypsum, is coarsely to finely granular, white to gray,
and contains varying amounts of impurities.
In the Wellington- McPherson Lowlands and the Arkansas River Lowlands,
gypsum is found in the shales of the Wellington Formation. In the Arkansas
River Lowlands, gypsum crops out in Wichita along Gypsum Creek, which drains
the eastern part of the city. Both selenite and satin spar can be collected
from these shales.” “Sand.—Found abundantly in Kansas, sand is a
loose, unconsolidated material formed from the breaking down or weathering of
older rocks and from the transportation and sorting of rock fragments by
moving water or by wind. Sand particles range in size from 0.625 mm and 2 mm,
larger than silt particles but smaller than pebbles. Kansas sand is composed
mostly of quartz. Sand also contains igneous and metamorphic minerals formed
outside the state and transported here by running water. Sand is common
throughout the Arkansas and Kansas river valleys. In the Arkansas River
Lowlands, sand dunes are common south of the river but rare north of the
river. This leads geologists to speculate that the prevailing winds were from
the north during the time of deposition, which was during the glaciations of
the Pleistocene Epoch (1.6 million to 10,000 years ago). At that time, huge
ice sheets to the north may have created winds from the north, the opposite
of today’s patterns, in which winds generally come from the south. Gypsum
Creek, Wichita.” “ Salt. —Halite, common table salt, is composed
of sodium chloride (NaCl). Most salt crystals are transparent and colorless
cubes, but impurities may impart a brilliant red, blue, or yellow color.
Broken fragments may be very nearly cube-shaped. Halite is easy to identify
because it has a salty taste and dissolves easily in water. Salt is an evaporite, which means it is
formed by the evaporation of water. (Other evaporites are gypsum and
anhydrite.) Salt rarely forms outcrops because rain and ground water dissolve
salt that is exposed at the surface. In Kansas, salt is found in thick beds
in Permian rocks deep underground, the largest of which is the Hutchinson
salt bed, which underlies approximately 37,000 square miles in central
Kansas. This salt was deposited by the evaporation of a shallow arm of the
Permian sea, which was cut off from the open ocean. When that shallow arm
evaporated, it left behind thick layers of gray shale, salt, and gypsum.
These deposits were subsequently buried by younger sediments and remained
hidden for millions of years until salt was accidentally discovered near
Hutchinson in 1887 by drillers looking for oil and gas. Salt was also discovered in Wellington in
1887. However, because this Sumner
County town is near the eastern edge of the Hutchinson salt bed, the salt was
only about 50 feet thick and the salt mine that opened there soon failed.
Today salt mines operate in Rice, Reno, and Ellsworth counties.” Places to Visit
“Gypsum Creek. —To see examples of gypsum in the
Wichita area, go to Gypsum Creek’s intersection with South Woodlawn Street,
just north of the Kansas turnpike (I-35) overpass. Walk eastward up the creek
bed for about 200 yards. As you walk along the gypsum ledge overhanging the
creek, note the sulfuric smell. Washing from the shale bottom of Gypsum
Creek, along the creek bottom and sand bars, are good selenite crystals and
some satin spar. Specimens may be collected at this location. Sand Hills
State Park.—A good place to see sand dunes in the Arkansas River Lowlands
is Sand Hills State Park, a few miles northeast of Hutchinson in Reno County.
The water table underneath these grass covered dunes is so close to the
surface that you can almost hit water by digging with your hands. To get to
the park, follow Kansas Highway 81 north out of Hutchinson for approximately
two miles.” “Quivira National Wildlife Refuge. —This wildlife refuge in northeastern
Stafford County lies in the transition zone between the relatively lush
vegetation of the eastern prairie and the more arid grasslands of the western
prairie. Big and Little Salt marshes, located within the refuge, provide
food, cover, and a resting place for thousands of waterfowl migrating between
breeding and wintering areas. The salty surface waters and salt flats at
Quivira are caused by natural saltwater in the underlying bedrock, which is
discharged in the vicinity. The average salinity of Little Salt Marsh is
approximately 2,500 parts per million (ppm); that of Big Salt Marsh ranges
from 5,000 to 10,000 ppm. (The salinity of seawater is 19,000 ppm, and the
upper limit for drinking water is about 250 ppm).” References Buchanan, Rex
C., and McCauley, James R., 1987, Roadside Kansas—A Traveler’s Guide to Its
Geology and Landmarks: Lawrence, Kansas, University Press of Kansas, 365 p. Buchanan, Rex
C., Tolsted, Laura L., and Swineford, Ada, 1986, Kansas Rocks and Minerals:
Kansas Geological Survey, Educational Series 2, 60 p. Evans, Catherine
S., 1988, From Sea to Prairie—A Primer of Kansas Geology: Kansas Geological
Survey, Educational Series 6, 60 p. Jackson, Julia
A., editor, 1997, Glossary of Geology (Fourth Edition): Alexandria, Virginia,
American Geological Institute, 769 p. Kansas
Geological Survey. 1999. Arkansas River Lowlands and
Wellington-McPherson Lowlands: Rocks and Minerals. This fact sheet
was compiled by Kansas Geological Survey staff (April 1999).< http//:www.kgs.ukans.edu/Extension/home.html/> Sawin, Robert
S., and Buchanan, Rex C., eds., 1996, Field Guide—Kansas Water Issues: Kansas
Geological Survey, Open-file Report 96-23, 65 p. Sawin, Robert
S., and Buchanan, Rex C., eds., 1997, Field Guide—Urban Expansion and Natural
Resources—Land Use, Water, and the Environment: Kansas Geological
Survey. Open-file Report 97-37, 53 p. Skelton,
Lawrence, 1997, Wichita’s Building Blocks—A Guide to Building Stones and
Geological Features: Kansas Geological Survey, Educational Series 11, 28 p. Wilson, Frank
W., 1978, Kansas Landscapes—A Geologic Diary: Kansas Geological Survey, Salt flats at Quivira National Wildlife
Refuge, Stafford County.Educational Series 5, 50 p. |