DOMINANT LITHOLOGY

Overview: Rock (and sediment) terms that represent the prevailing composition of each geologic map unit have been assigned (See Dominant Lithology Map link). Prevailing compositions are the dominant lithologies that most affect the unit's land-use and geotechnical behavior. This assessment was made by reviewing descriptions from existing geologic maps and published reports. Some map units are made up of more than one rock unit; in those cases the dominant lithologic term is a composite of the member units. The basic character of each lithologic term is described below, along with additional properties that are known to be associated with similar materials.

Unconsolidated material

1.  Clay and silt: Unconsolidated to semiconsolidated, fine-grained sediment. Associated with surficial deposits in the Jackson Purchase region and glacial, lacustrine (lake) deposits in the Ohio River Valley and tributaries of the river. May contain lenses or thin layers of chert. Additional properties : Clay-rich deposits may have swelling properties.
2. Eolian loess: Silt and clayey silt deposited by wind; typically unconsolidated, homogenous, nonstratified, and friable. Commonly covers uplands adjacent to alluvial valleys of the Ohio River and its tributaries. Additional properties : Reported to be most stable in near-vertical exposures.
3. Eolian sand: Very fine-to fine-grained sand deposited by wind, such as sand dunes; mainly quartz grains. Unit commonly concealed by loess.
4. Gravel: Mainly consisting of pebbles or cobbles of quartz, chert, limestone, sandstone, or siltstone. Matrix is commonly fine to coarse sand.
5. Mixed sediments: Unconsolidated material containing mixtures of gravel, sand, silt, and clay. Lithology mainly occurs in surficial units such as Alluvium and Terrace deposits.
6. Sand and gravel: Coarse-grained variety of unconsolidated, mixed sediments.
7. Sand, silt, and clay: Fine-grained variety of unconsolidated mixed sediments. 

Bedrock units

1. Artificial fill: Man-made compacted rock debris from highways, railroads, and earthen dam construction.
2. Black shale: Fine-grained, organic-rich sedimentary rock formed from the compaction of clay silt or mud. Clayey to silty texture; commonly splits along irregular bedding planes. Gray to black. Commonly contains fractures. Additional properties: Prone to extensive weathering, plastic clays can present poor foundation conditions and unstable slopes. Possible pyrite expansion in some areas.
3. Conglomeritic sandstone: Coarse-grained sedimentary rock consisting of large quartz pebbles in a sandstone matrix.
4. Dolomite: Sedimentary rock, more than 90 percent of the mineral dolomite (CaMg(CO 3 ) 2 ) and less than 10 percent of the mineral calcite (CaCO 3 ). Generally has a sugary texture, but lacks visible, individual grains as in sandstone.
5. Dolomite and limestone: Sedimentary rock units of interbedded dolomite and limestone (see definitions of dolomite and limestone).
6. Gray shale: A fine-grained sedimentary rock formed from the compaction of clay, silt, or mud. Clayey to silty texture; commonly splits along planar or irregular bedding planes. Additional properties: Some units may have high percentage of swelling clay, slopes can be unstable and susceptible to landslides.
7. Limestone and minor dolomite: Mainly comprised of limestone with few interbeds of dolomite. Unit may have thin interbeds of shale as well. Limestone varies from fine-grained argillaceous to coarse-grained crystalline varieties.
8. Limestone and shale: Mainly composed of approximately equal parts limestone and shale. Both sedimentary rocks, limestone is primarily composed of calcite and varies from fine-grained argillaceous to coarse-grained crystalline varieties. Limestone is commonly fossiliferous. Shale is fine-grained and formed from the compaction of clay, silt, or mud. Clayey to silty texture; commonly splits along planar or irregular bedding planes. Additional properties: Areas underlain with this unit commonly have high karst potential.
9. Limestone and minor shale: Mainly comprised of limestone with few interbeds of shale. Limestone varies from fine-grained argillaceous to coarse-grained crystalline varieties. Additional properties: Areas underlain with this unit commonly have high karst potential.
10. Limestone, coarse-grained: Sedimentary rock primarily composed of calcite. Coarse-grained limestone can range from coarsely crystalline to bioclastic (fossiliferous) or oolitic. Additional properties : Areas underlain with this unit commonly have high karst potential.
11. Limestone, fine-grained: Sedimentary rock primarily composed of calcite. Fine-grained limestone can range from argillaceous lime mud to finely crystalline varieties. Additional properties : Typically well suited for foundation material and construction aggregate. Areas underlain with this unit commonly have high karst potential.
12. Lithic sandstone: Coarse-grained sedimentary rock containing visible grains of quartz (up to 90 percent), other minerals, and rock fragments. Commonly contains abundant amounts of mica minerals. These sandstones are typically light to dark gray in color.
13. Mixed clastics: Interbedded shale, sandy shale, sandstone, fireclay, and coal; associated with coal-bearing rock sequences in the Eastern and Western Kentucky Coal Fields. Additional properties : Fine-grained rocks in these sequences, especially those associated with marine units, are susceptible to landslide development on steep to moderate slopes. Light-colored and red or green, fine-grained rocks found in northeastern Kentucky are highly slaking and do not form stable slopes.
14. Mixed clastics and carbonates: Sedimentary rock sequences including detrital clastics and marine limestones. Lithology mainly represents combined rock units within the Mississippian and Pennsylvanian.
15. Peridotite: A coarse-grained intrusive igneous rock. Some outcrops may be weathered areas of soil containing igneous mineral crystals. Green to black.
16. Quartzose sandstone: A light-colored, coarse-grained clastic sedimentary rock in which quartz is the primary constituent (more than 90 percent). Commonly well-sorted, "clean" sandstone. Usually tan to white. Additional properties : Quartzose sandstones are often very hard and form cliffs or resistant caps to ridges and plateaus. Porous varieties may be hosts for petroleum reservoirs in the subsurface.
17. Reddish green shale: Shale is a fine-grained sedimentary rock formed from the compaction of clay, silt or mud. The distinctive color is mainly a result of the carbon content and oxidation state of iron in the shales. Lithology may contain minor amounts of siltstone and sandstone. Additional properties: lithology tends to weather rapidly, slopes can be unstable at low angles.
18. Sandstone and minor shale: A coarse-grained clastic sedimentary rock composed of grains of sand (primarily quartz) in a matrix of silt or clay. Sandstone is commonly interbedded with shale.
19. Shale and limestone: Interbedded shale and limestone. More than 50 percent of the shale layers. Shale is a fine-grained sedimentary rock formed from the compaction of clay, silt, or mud. Additional properties : Thick accumulations of weathered shale on steep slopes can become unstable. Shale tends to slump when overly saturated with water.
20. Shale and minor dolomite: Mainly consists of shale interbedded with minor amounts of dolomite. Shale is a fine-grained sedimentary rock formed from the compaction of clay, silt or mud. Additional properties : Thick accumulations of weathered shale on steep slopes can become unstable. Shale tends to slump when overly saturated with water.
21. Shale and sandstone: Interbedded shale and sandstone. Unit has more shale than sandstone. Shale is a fine-grained sedimentary rock formed from the compaction of clay, silt, or mud. Additional properties - Thick accumulations of weathered shale on steep slopes can become unstable. Shale tends to slump when overly saturated with water.
22. Siltstone and shale: Interbedded siltstone and shale. Unit has more siltstone. Siltstone is similar to shale but commonly lacking fissility and thin laminations. Additional properties - Thick accumulations of weathered shale on steep slopes can become unstable. Shale tends to slump when overly saturated with water.
23. Brecciated or deformed: Breccia is a clastic rock composed of angular or broken rock fragments held together by a fine-grained cement or matrix. Deformation may be many any type of folding, faulting, brecciation, or shattering in the rock.