Limestone

Pure limestones are white or almost white. Because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Limestone my be crystalline, clastic, granular, or dense, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock. Chert nodules are common in limestone layers (especially in the Florence Limestone or Permian Age, which outcrops in the Flint Hills area from Marshall County southward to Cowley and Chautauqua counties).

Origin

Most limestones are marine deposits, but some are formed in lakes, rivers and on land.

Limestones consisting mainly of animal shells.

The shells of many animals, those that live either in the sea or in freshwater, consist of calcium carbonate (calcite and aragonite). When the animals die, their shells are left on the ocean floor, lake bottom or river bed where they may accumulate into thick deposits.

Crinoidal Limestones - Crinoids are sea animals that had long stems, cup like bodies and long filter arms, that look so much like flowers that they are call sea lillies. The stems breaks into small, disc shaped fragments. Some limestones of the Pennsylvanian and Permian aged rocks of Kansas contain so many of these stem fragments that the term crinoidal limestone describe them well. These are found extensively in eastern Kansas. The Cretaceous Niobrara Chalk is one of the few localities in western Kansas that contains beautiful specimens of stemless crinoids, in which both the bodies and the long arms are well preserved.

Fusilinid Limestones - The Fusilinid is a member of the single-celled animals call Foraminifera. These small animals, whose shells look like grains of wheat, were abundant during the Pennsylvanian and Permian periods. Many limestone are almost solid masses of fusilinid shells.

Reef-like Limestones and Shell Limestones. These limestones contain the remains of corals, brachipods, clams, oysters, bryozoans and other forms. Some of these animals lived on colonies and the remains formed lens-shaped or elongated deposits, which sometimes grew to several hundred miles in length. The ones found in Kansas are, however, much smaller. Reeflike bodies in eastern and southeastern Kansas were formed by limy mud trapped by leaf-like blades of marine algae. Small colonies or groups of fossil shells in some formations measure only a foot in diameter.

Limestones formed partly by chemical processes

Calcium carbonate is more soluble in water that contains carbon dioxide than in pure water. When the carbon dioxide is removed for any reason, (Plants remove carbon dioxide by using it in their food. When water is heated, evaporated or merely stirred, carbon dioxide is decreased) the calcium carbonate falls out of the solution and settles to the bottom.

Algal Limestone - Algae are primitive plants (most seaweeds and pond scums are algae). They may live in seawater or freshwater. Like all plants, they use carbon dioxide to manufacture food thus allowing for the participation of the calcium carbonate. The resulting limestone commonly takes on the form of algae or groups of algae and may form irregular shaped and banded structures. Approximately half of the Pennsylvania and Permian limestones of eastern Kansas are at least, partially formed by algae. Particularly good exposures can be seen in Johnson County, Brown County and in the Flint Hills.

Oolitic limestone - Oolites are small rounded particles or grains, so named because they look like fish eggs. Oolites commonly are formed by layers of material (usually calcite), that have been deposited around some tiny particle such as a sand grain or fossil fragment and are rolled back and forth in quiet waters. Some of the oolites may be of algal origin. When the grains formed by the process are more than two millimeters in diameter (about the size of the head of a pin), they are called pisolites.

Many limestones in Kansas (particularly of Pennsylvanian age) contain oolites. Most outcrops of oolitic limestone are found in the eastern one-third of the state. They are especially noticeable in Johnson, Miami, Linn, Bourbon, and Labette Counties and near the towns of Independence and Cherryvale in Montgomery County. Kansas rocks of Permian and younger ages do not contain many oolites.

Chalk is a variety of limestone that probably was formed by the accumulation of shells of Foraminifera and/or by chemical precipitation of calcium carbonate. Pure chalk is white, but it may be stained with iron oxide or other impurities. It is a soft porous rock that crumbles easily.

In the Cretaceous rocks of western Kansas the Niobrara Chalk (also contains some shale) outcrops in an irregular belt from Smith and Jewell counties on the northeast to Finney and Logan counties on the southwest. The rock is gray to cream color, but weathers white, yellow or orange. The average thickness of the entire formation is about 600 feet.

Kansas chalk beds are known worldwide for the reptilian and other vertebrate fossils found. They are equally famous for the pinnacles, spires and odd-shaped masses formed. Particularly notable are Monument Rocks and Castle Rock in Gove County and the chalk bluffs along the Smoky Hill River in Logan, Gove and Trego counties.

Diatomaceous Marl - This rock is important because of the calcium carbonate content and the silica content from the diatoms which are tiny, single-celled creatures that have characteristics of both plants and animals. When the diatoms die, there outer shell (silica) settle to the bottom of the lake/sea and accumulate. Diatomaceous Marl is found in the Ogallala Formation of Wallace and Logan counties. The deposits can been seen from a distance where they outcrop along the south side on a valley for about four miles. Outcrops are also found in Meade, Seward counties and elsewhere in western Kansas. The rock can be mined and used for filtering water or other solutions and as a filler in paints and other products.

Travertine is a banded, compact variety of limestone. It is formed along streams, particularly where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited, where evaporation of the water leaves a solution that is supersaturated with chemical constituents of calcite. A good deposit was found near Waconda Spring in Mitchell County, where the minerals in the spring water built a hill of travertine 42 feet high and 300 feet in diameter. This deposit is now covered by the Glen Elder Reservoir. Tufa, a porous or cellular variety of travertine is found near waterfalls. Such deposits have been reported in Riley and Butler counties.

Caliche is a type of calcite-cemented sandstone that forms in the soils of dry regions. It is generally impure (clay, silt, sandy), fairly soft (although very old caliche maybe extremely hard). Some caliche deposits consist of only small nodules, such as the Loess Kinchen in wind-blown silt, but also occurs as a continuous bed that can be traced for many miles. The pisolitc limestone near the surface of the High Plains in western Kansas is such a bed. This dense limestone has a distinctive structure and can be recognized by its pinkish color, banded appearance and concentric areas. It was formed after the close of the Tertiary, when the climate was drier than it is now.

Table 2 - Particle Size
Sedimentary Rocks

Size

Fragment

Rounded, Subrounded, Subangular
Aggregate

Angular
Aggregate
> 256mm Boulder Boulder gravel, Boulder conglomerate

Rubble
256 - 64mm Cobble Cobble gravel, cobble conglomerate

  Breccia
64 - 4mm Pebble Pebble gravel, pebble conglomerate
4 - 2 mm Granule Granule gravel  
2 - 1/16 mm Sand Sand, Sandstone Grit (1/2 - 1 mm)
1/16 - 1/256mm Silt Silt, Siltstone  
< 1/256 mm Clay Clay, Shale