Mammoth Cave vs Valley and Ridge Karst
The Central Kentucky Karst is a well known karst landscape which features the largest mapped cave in the world with over 400 miles of known passageway. Just like the Valley and Ridge karst the same five ingredients of karst which include; rock, solvent, gradient, geometry, and time are critical in forming this unique landscape.
Mammoth Cave Rocks: The stratigraphic column of the south-central Kentucky is listed above. The main three limestone units that Mammoth Cave forms in are the Girkin, Ste. Genevieve, and St. Louis Limestones, which combine to be a 150 meter package of limestone. The Big Clifty Sandstone is an crucial sandstone that acts as a caprock, which protects the limestone below from dissolution. Hence the location of the Big Clifty Sandstone determines where the Mammoth Cave system is located at. Where the Big Clifty is not exposed intense dissolution of the limestone occurs and this leads to the formation of the Sinkhole Plain which is pictured below. Also the Lost River Chert bed at the top of St. Louis Limestone acts as a caprock/confining unit for caves in the Sinkhole Plain.
Mammoth Cave Rocks: The stratigraphic column of the south-central Kentucky is listed above. The main three limestone units that Mammoth Cave forms in are the Girkin, Ste. Genevieve, and St. Louis Limestones, which combine to be a 150 meter package of limestone. The Big Clifty Sandstone is an crucial sandstone that acts as a caprock, which protects the limestone below from dissolution. Hence the location of the Big Clifty Sandstone determines where the Mammoth Cave system is located at. Where the Big Clifty is not exposed intense dissolution of the limestone occurs and this leads to the formation of the Sinkhole Plain which is pictured below. Also the Lost River Chert bed at the top of St. Louis Limestone acts as a caprock/confining unit for caves in the Sinkhole Plain.
Mammoth Cave Solvent: Recharge in the Mammoth Cave Karst occurs in sinkholes, sinking streams, and from percolation along fractures/joints in the permeable but mostly insoluble Big Clifty Sandstone. The agent of dissolution is by carbonic acid in which meteoric waters mix with carbon dioxide sources in the atmosphere and soil. Work by (Hess & White, 1993) shows that the saturation indices in springs are seem to be undersaturated with calcite throughout the year with springs in the Haney much more undersaturated. A brief period of degassing of CO2 and low flow in the Summer/Fall may contribute to springs in the Girkin, Ste. Genevieive, and St. Louis to be briefly oversaturated with respect to CO2.
Mammoth Cave Gradient/Geometry: Faults and folds do occur in the Mammoth Cave zone, but they are not as major of a feature compared to the Valley and Ridge. The overall dip of the rocks of Mammoth Cave is very gentle, but there is enough gradient available for ground water to move, but still the gradient is not steep enough so the meteroic water can travel long distances along bedding planes, allowing for cave development to extend long distances. Many caves in Mammoth Cave are your curvilinear branchwork caves which make sense because many are controlled by bedding planes(Palmer, 1981) although caves up in the Haney Limestone Member are often controlled by joints (Arpin, 2013) so they may take on a more rectilinear branchwork morphology or even a network maze morphology.
Mammoth Cave Time: The Mammoth Cave karst system is in a mature state. Not a post mature karst, but much older compared to eogenetic karst in the Floridian Aquifer system. Enough time has passed in the Mammoth Cave to allow for levels to form in the cave system. Here during various time periods over the past 10 millions there were three main incisions of the Green River at the level that the Green River was at that time, and this allowed for the development of three generations of cave passages. Information was provided (White, 1970; Palmer, 1981; and Palmer, 2000)
Mammoth Cave Gradient/Geometry: Faults and folds do occur in the Mammoth Cave zone, but they are not as major of a feature compared to the Valley and Ridge. The overall dip of the rocks of Mammoth Cave is very gentle, but there is enough gradient available for ground water to move, but still the gradient is not steep enough so the meteroic water can travel long distances along bedding planes, allowing for cave development to extend long distances. Many caves in Mammoth Cave are your curvilinear branchwork caves which make sense because many are controlled by bedding planes(Palmer, 1981) although caves up in the Haney Limestone Member are often controlled by joints (Arpin, 2013) so they may take on a more rectilinear branchwork morphology or even a network maze morphology.
Mammoth Cave Time: The Mammoth Cave karst system is in a mature state. Not a post mature karst, but much older compared to eogenetic karst in the Floridian Aquifer system. Enough time has passed in the Mammoth Cave to allow for levels to form in the cave system. Here during various time periods over the past 10 millions there were three main incisions of the Green River at the level that the Green River was at that time, and this allowed for the development of three generations of cave passages. Information was provided (White, 1970; Palmer, 1981; and Palmer, 2000)