The Pennyroyal Plateau or Pennyroyal Region, often spelled Pennyrile, [1] is a large physiographic region of Kentucky that features rolling hills, caves, and karst topography in general. It is named for Hedeoma pulegioides (the American pennyroyal), a wild mint that grows in the area. It is also called the "Mississippian Plateau," for the Mississippian geologic age in which it was formed. [2]
The Pennyroyal is bordered by the Pottsville Escarpment in the east. The Pottsville Escarpment is the transition zone from the central part of Kentucky to the higher and geologically younger Cumberland Plateau in the eastern part of the state. The Pennyroyal is bordered on the north by Muldraugh Hill, the geological escarpment that forms the transition from the geologically older Bluegrass to the Pennyroyal. This is a series of knobs and ridges based on hard siltstones.
The Pennyroyal is bordered on the west by the younger Jackson Purchase. The Pennyroyal is often thought by non-geologists to include the West Kentucky Coal Field of Pennsylvanian age, located in the northwestern area of the state, as the southeastern part of the Illinois Basin. The coalfield and the Pennyroyal are of different geologic ages and are separated by the Clifty Region, largely of Pennsylvanian sandstone, occasionally bituminous; the boundary with the Pennyroyal is the Dripping Springs Escarpment. [3]
To the south, the Pennyroyal continues as the Highland Rim of Middle Tennessee.
The Pennyroyal is largely in farmland where the bedrock is limestone, and most of the Pennyroyal is based on Mississippian limestone, particularly the St. Louis Limestone or Ste. Genevieve Limestone. In some areas, the limestone is capped with a soft sandstone. This kind of formation is featured in the Mammoth Cave area, and has enabled the formation of the world's most extensive cave system. Numerous other caves exist in the Pennyroyal, where some of the most intensely cave-forming limestones of the world are to be found. [4]
Where the capping sandstone is intact, the land surface is usually forested, rugged hills.
The Bluegrass region is a geographic region in the U.S. state of Kentucky. It makes up the central and northern part of the state, roughly bounded by the cities of Frankfort, Paris, Richmond and Stanford. It is part of the Interior Low Plateaus ecoregion.
Muldraugh Hill is an escarpment in Bullitt, Hardin, Jefferson, and Nelson counties of central Kentucky separating the Bluegrass on the north and north-east from the Pennyrile on the south and south-west. This escarpment fades into the Pottsville Escarpment on the east and terminates at the Ohio River in the west. However, in truth, it continues in Indiana as Floyds Knobs.
The Cumberland Plateau is the southern part of the Appalachian Plateau in the Appalachian Mountains of the United States. It includes much of eastern Kentucky and Tennessee, and portions of northern Alabama and northwest Georgia. The terms "Allegheny Plateau" and the "Cumberland Plateau" both refer to the dissected plateau lands lying west of the main Appalachian Mountains. The terms stem from historical usage rather than geological difference, so there is no strict dividing line between the two. Two major rivers share the names of the plateaus, with the Allegheny River rising in the Allegheny Plateau and the Cumberland River rising in the Cumberland Plateau in Harlan County, Kentucky.
The West Kentucky Coal Field comprises an area in the west-central and northwestern part of the state, bounded by the Dripping Springs Escarpment and the Pennyroyal Plateau and the Ohio River, but is part of the Illinois Basin that extends into Indiana and Illinois. It is characterized by Pennsylvanian age sandstones, shales and coal. Nearly all of the counties in the area are part of the television market known as the Kentucky–Illinois–Indiana tri-state area.
The Nashville Basin, also known as the Central Basin, is a term often used to describe the area surrounding Murfreesboro, Tennessee, in which Nashville is located. The Central Basin was caused by an uplifting which produced a dome known as the Nashville Dome. The Nashville Dome is evidenced by the underlying rock strata that all dip downward away from Nashville. The uplifting of the Nashville Dome fractured overlying strata, making it more easily eroded, and thus the "dome" resulted in a "basin". Uplifted strata in the center of a geological dome have higher potential erosive energy than the surrounding strata, because they are physically higher. Erosion thus acts on the uplifted area at a greater rate than on the surrounding flat-lying area, creating a low area, i.e., a basin. This area is more correctly referred to as the "Central Dome" of Tennessee.
The Highland Rim is a geographic term for the area in Tennessee, North Alabama, and Kentucky which surrounds the Central Basin. Geologically, the Central Basin is a dome. The Highland Rim is a cuesta surrounding the basin, and the border where the difference in elevation is sharply pronounced is an escarpment.
The Tradewater River is a tributary of the Ohio River, approximately 136 miles (219 km) long, in western Kentucky in the United States. It drains an area of 932 square miles (2,410 km2) in the limestone hills south of Evansville, Indiana, between the basins of the Cumberland River on the west and the Green River on the east.
The Allegheny Front is the major southeast- or east-facing escarpment in the Allegheny Mountains in southern Pennsylvania, western Maryland, eastern West Virginia, and western Virginia. The Allegheny Front forms the boundary between the Ridge-and-Valley Appalachians to its east and the Appalachian Plateau to its west. The Front is closely associated with the Appalachian Mountains' Eastern Continental Divide, which in this area divides the waters of the Ohio/Mississippi river system, flowing to the Gulf of Mexico, from rivers flowing into Chesapeake Bay and from there into the Atlantic Ocean.
The Knobs Region or The Knobs is located in the US state of Kentucky. It is a narrow, arc-shaped region consisting of hundreds of isolated hills. The region wraps around the southern and eastern parts of the Bluegrass region in the north central to northeastern part of the state. The western end of the Knobs region begins near Louisville, Kentucky and continues southeastward through Bullitt, Hardin, Nelson, LaRue, Marion County, Taylor, Boyle, Casey, Lincoln, and Garrard counties before turning northeast and running along the Pottsville Escarpment and the Appalachian Plateau. The Knob arc has a length of 230 miles (370 km).
The Big South Fork National River and Recreation Area, commonly known as Big South Fork, preserves the Big South Fork of the Cumberland River and its tributaries in northeastern Tennessee and southeastern Kentucky.
The Girkin Formation is a geologic formation located in the Chester Escarpment of central Kentucky, USA. It comprises a level of Mammoth Cave and lies above the Ste. Genevieve Limestone and St. Louis Limestone and below the Big Clifty Sandstone in that area. The Girkin is a limestone Mississippian in age.
The Osage Plains are a physiographic section of the larger Central Lowland province, which in turn is part of the larger Interior Plains physiographic division. The area is sometimes called the Lower Plains, North Central Plains,or Rolling Plains. The Osage Plains, covering west-central Missouri, the southeastern third of Kansas, most of central Oklahoma, and extending into north-central Texas, is the southernmost of three tallgrass prairie physiographic areas. It grades into savanna and woodland to the east and south, and into shorter, mixed-grass prairie to the west. The Osage Plains consist of three subregions. The Osage Plains proper occupy the northeast segment. Although sharply demarcated from the Ozark uplift, the plains are nonetheless a transitional area across which the boundary between prairie and woodland has shifted over time. In the central portion of the physiographic area lies the second subregion, the Flint Hills, commonly called "the Osage" in Oklahoma. This large remnant core of native tallgrass prairie is a rocky rolling terrain that runs from north to south across Kansas and extends into Oklahoma. To the west and south of these hills are the Blackland Prairies and Cross Timbers. This vegetatively complex region of intermixed prairie and scrubby juniper-mesquite woodland extends into north-central Texas. Bluestem prairies and oak-dominated savannas and woodlands characterize the natural vegetation in the Cross Timbers. Much of the area has been converted to agriculture, although expanses of oak forest and woodland are still scattered throughout the eastern portion of the subregion.
Western Kentucky is the western portion of the U.S. state of Kentucky. It generally includes part or all of several more widely recognized regions of the state.
The geology of Kansas encompasses the geologic history and the presently exposed rock and soil. Rock that crops out in the US state of Kansas was formed during the Phanerozoic eon, which consists of three geologic eras: the Paleozoic, Mesozoic and Cenozoic. Paleozoic rocks at the surface in Kansas are primarily from the Mississippian, Pennsylvanian, and Permian periods.
The Pennsylvanian Pottsville Formation is a mapped bedrock unit in Pennsylvania, western Maryland, West Virginia, Ohio, and Alabama. It is a major ridge-former in the Ridge-and-Valley Appalachians of the eastern United States. The Pottsville Formation is conspicuous at many sites along the Allegheny Front, the eastern escarpment of the Allegheny or Appalachian Plateau.
The Ozark Highlands is a Level III ecoregion designated by the Environmental Protection Agency (EPA) in four U.S. states. Most of the region is within Missouri, with a part in Arkansas and small sections in Oklahoma and Kansas. It is the largest subdivision of the region known as the Ozark Mountains, less rugged in comparison to the Boston Mountains in Arkansas, the highest part of the Ozarks.
The Interior Low Plateaus are a physiographic region in eastern United States. It consists of a diverse landscape that extends from north Alabama across central Tennessee and Kentucky into southern Illinois, Indiana, and Ohio. Its natural communities are a matrix of temperate forests, woodlands, and prairies.
The Pennington Formation is a geologic formation named for Pennington Gap, Virginia. It can be found in outcrops along Pine Mountain and Cumberland Mountain in Kentucky, Virginia, and Tennessee, where it is the uppermost Mississippian-age formation. The name has also been applied to similar Mississippian strata in the Cumberland Escarpment of eastern Kentucky, though the rocks in that area were later renamed to the Paragon Formation.
The geology of Ohio formed beginning more than one billion years ago in the Proterozoic eon of the Precambrian. The igneous and metamorphic crystalline basement rock is poorly understood except through deep boreholes and does not outcrop at the surface. The basement rock is divided between the Grenville Province and Superior Province. When the Grenville Province crust collided with Proto-North America, it launched the Grenville orogeny, a major mountain building event. The Grenville mountains eroded, filling in rift basins and Ohio was flooded and periodically exposed as dry land throughout the Paleozoic. In addition to marine carbonates such as limestone and dolomite, large deposits of shale and sandstone formed as subsequent mountain building events such as the Taconic orogeny and Acadian orogeny led to additional sediment deposition. Ohio transitioned to dryland conditions in the Pennsylvanian, forming large coal swamps and the region has been dryland ever since. Until the Pleistocene glaciations erased these features, the landscape was cut with deep stream valleys, which scoured away hundreds of meters of rock leaving little trace of geologic history in the Mesozoic and Cenozoic.
The geology of Kentucky formed beginning more than one billion years ago, in the Proterozoic eon of the Precambrian. The oldest igneous and metamorphic crystalline basement rock is part of the Grenville Province, a small continent that collided with the early North American continent. The beginning of the Paleozoic is poorly attested and the oldest rocks in Kentucky, outcropping at the surface, are from the Ordovician. Throughout the Paleozoic, shallow seas covered the area, depositing marine sedimentary rocks such as limestone, dolomite and shale, as well as large numbers of fossils. By the Mississippian and the Pennsylvanian, massive coal swamps formed and generated the two large coal fields and the oil and gas which have played an important role in the state's economy. With interludes of terrestrial conditions, shallow marine conditions persisted throughout the Mesozoic and well into the Cenozoic. Unlike neighboring states, Kentucky was not significantly impacted by the Pleistocene glaciations. The state has extensive natural resources, including coal, oil and gas, sand, clay, fluorspar, limestone, dolomite and gravel. Kentucky is unique as the first state to be fully geologically mapped.