Conor Watkins' Ozark Mountain Experience

Article 60-62 Combined



The Engineering Geology of Thomas Jefferson Hall

And The Filled Sinks of The Ozarks

Darn! We Won't Be Touring The Leaning Tower of TJ Anytime Soon



The south exposure of the Vichy Rd. Filled Sink is clearly visible here,

as it has weathered back into the hillside, allowing snow to accumulate.

The surrounding Jefferson City dolomite (buff color) remains free of snow as

its walls are steeper. Thomas Jefferson Hall, built on another such structure,

is visible in the background.

It seems the passing of urban legends pertaining to campus buildings and professors is a rite of passage on most college campuses. These legends are sometimes started by upper classmen trying to trick freshmen into believing their tall tales. Other times, an old story about a building or person will be dug up and partially misunderstood. These legends also serve as a form of entertainment by adding mystery to what would otherwise be rather dull subjects. As with the almost all college campuses, UM-Rolla has its share of urban legends.

One of the most commonly told urban legends on campus is that the south tower of the Thomas Jefferson (TJ) Residence Hall is slowly sinking and will eventually need to be closed. As with many urban legends, there are some grains of truth to this one. Perhaps this legend was started by cracks caused by differential settlement (when one part of a building settles faster than other parts) soon after the building opened or an article in the Missouri Miner that appeared on March 29, 1984.

The March 29, 1984 Miner article was part of the April Fools issue and a headline titled “TJ Sinkhole Could Cause Geo-puckering” appeared at the top of the front page. This tongue and cheek article states that a sinkhole was discovered under TJ Hall during construction but that it was filled with concrete. It also goes into several wild predictions that the building is sinking, tilting, and could cause suction that might also pull the north tower of TJ down along with the south tower. Also included is a suggestion that the third floor may sink to current ground level.

The article then describes plans to turn the “Leaning Tower of TJ” into a tourist attraction. Since it is in plain view of I-44 tourists should come in droves! While some students in the north tower looked forward to falling into a hole, those in the south tower were scared. Those working to prevent the fall started a group called KWEST (Keep Working Entirely Saves TJ). Although no plans to save the building were presented, the front page features a picture of KWEST members standing straight while their hall tilts at a wild angle in the background. This picture was taken by aligning the vertical axis of the camera with leaning students to create the illusion that the building was in fact tilting.

Both towers of TJ Hall are built partially or completely atop an ancient paleokarst or filled sink structure developed in the Jefferson City Formation, a dolomite from the Ordovician Period of geologic time (505-440 million years ago). The paleokarst features in the area are are a geologic feature somewhat unique to the Ozarks, although other types of paleokarst occur worldwide. These structures may or may not be true sinkholes that have been filled in with soil, rock, or ore bearing materials. Although dissolution of rock occurred, it appears that standard karst processes (process of groundwater dissolving rock) were not always entirely responsible for their formation. Although their origin is unknown, various theories on how these filled sinks formed have been presented over the years. For this reason, some like to avoid using the term filled sink or paleosink, as no one is absolutely sure these were once sinkholes. Paleokarst, essentially meaning "fossil karst", is a more general term and is often used instead. It is known that most of these structures were infilled during the Pennsylvanian Period of geologic time (326-286 million years ago). For reference, the dinosaurs are though to have died out around 66 million years ago. The topic of their possible origin will be discussed in more detail later.

Structures built atop filled sinks can experience a wide variety of problems but measures were taken to avoid settlement and tilting during the design and construction of TJ. The foundation under the south tower of TJ consists a system of drilled shafts ir piers, which is a very conservative design. The piers for TJ were installed by excavating 36 inch diameter shafts through the shaley sink filling and at least two feet into “solid” bedrock below. These shafts were filled with a cage of reinforcing steel and then concrete to form supporting piers. Reinforced concrete grade beams were them used to bridge between the piers. The building itself was built atop these beams and these are likely the cause of the cracking in the structure.



Partial foundation plans for the south tower of TJ thanks to UM-Rolla

Physical Facilities.



Simplified diagram of the subsurface cross section beneath TJ Hall.

Note: There are more than four caissons under TJ in reality.



A drill rig in the process of excavating a shaft for one of many piers

supporting the south tower of TJ. These pictures were taken from the roof or

one of the balconies on the north tower. Notice the difference in the appearance

of U.S. Hwy 63 in the background.

Click links below for more pictures of the construction of TJ's foundation.

-Clearing land for construction 1, 2

-Foundation pier excavation and placement of grade beams 1, 2, 3, 4, 5, 6, & 7A/7B

Thanks to UMR Archives for the pictures of TJ's foundation construction.

Filled sinks do lose their fillings to voids below from time to time. Such events have both alarmed nearby residents and caused property damage. One such occurrence happened in Jefferson City, MO at Hwy 50 and Rainbow Drive in March of 1975. An ancient filled sink suddenly lost its contents, which surprised residents and required the relocation of a transformer. It was reported that dogs in the surrounding neighborhoods acted strangely for a half hour period during the night before the sink was discovered (possibly the sink was collapsing at this time). Unusual animal behavior has also been reported before and during earthquakes.

Another case of a filled sink reactivating occurred in April of 1993 after a mining operation closed at the Giancola Clay Pit, a filled sink near Owensville. This pit had partially filled with water that suddenly was lost through a cave that opened up in the side of the sink. 20 million gallons of water disappeared in about 12 hours. Nearby residents reported that their wells were damaged and sought damages from the mining company. The apparent cave opening in the sink has collapsed, but the pit continues to subside and drain water, indicating that the sink is still connected to subsurface conduits. The nearby Homeyer Road Claypit collapsed in 1966, clouding wells up to three miles away. Other claypits in the area have also collapsed.

Robert Dillon’s 1999 dissertation includes evidence that clay mining activities may be contributing to the instability of filled sinks, as mined out pits collect water and funnel it into the subsurface. This water, sometimes made more acidic by the oxidation of pyrites and other naturally occurring sulfides, can erode and dissolve subsurface soil and rock. Both mining activities and improperly sealed boreholes left from prospecting can allow water to enter the subsurface. The relatively impermeable parking lot built around TJ keep much of the rainwater falling nearby from entering the ground near the building. This reduces the chances of the sink or sinks under TJ from reactivating.

Cave Hill Cave, located along Hwy 50 near Mt. Sterling in Gasconade County, is what remains of a filled sink that has partially lost its filling to a cavity below. The Cave Hill sink structure is large and has dimensions of approximately 1 mile by ¼ mile. It is either one large sink or a combination of several smaller overlapping sinks. Cave Hill Cave is completely developed within a filled sink. Evidence indicates that its filling subsided into a cavity below. Slickensides (striations in the rock due to shear) are visible in the sides of the cave, indicating that the bottom of the cave dropped during its formation. The shaley filling has ponded water in the cave at a level much higher than local water table, even during droughts. The author recently attempted to access this cave and drove many miles out of the way to see this feature. After getting to within 1000 feet of the cave, the property was posted “No Trespassing” and the mission ended. The Hwy 50 roadcut at Cave Hill and those nearby contained multiple filled sinks and evidence of past faulting/folding. Perhaps this cave represents a similar phenomenon to what is or once was taking place under TJ.

During the excavations for the shafts to hold the piers supporting TJ, a cave with no previous natural entrances was discovered about 20 feet below the surface. Jerry Vineyard of the Missouri DNR – Geological Survey And Resource Assessment (formerly Division of Geology And Land Survey) was called in to investigate. He lit a carbide lamp and was lowered into the shaft. Upon being lowered into the cave, his carbide lamp went out. He tried to relight the lamp several times but was unable to do so. Vineyard used a backup flashlight to investigate the hole and found that the cave was completely formed within the sink filling. It appeared that the sink had lost 3-4 feet of its filling to a cavity below, allowing the shale to part along a bedding plane. The cave was observed to be about 20 feet long, 3-4 feet high in its tallest dimension, and seemed to be very unstable. It gradually squeezed down to nothing along the bedding planes of the shale filling. As Vineyard investigated the cave, he soon started breathing heavily without having exerted himself. At this point Vineyard called to be raised from the hole, as he suspected the air was bad and low in oxygen. Soon after, a rough looking, cigar smoking workman requested to be lowered in the hole. Upon getting to the bottom of the hole, his cigar went out, helping to verify that the air in the cave was unsuitable for people to breathe.

The portion of this shaft near the cave was cased with a liner before concrete was poured into the hole. Plans for the foundation of the structure were consulted in the writing of this article. Based on the designs for the piers, the building should be stable even if its piers pass through voids and unstable material on their way to solid bedrock. If the material within the sink subsides further, this would likely lead to problems in the parking lot, swimming pool, etc., but the main buildings should remain relatively undisturbed.

After the south tower of TJ Hall was constructed, significant cracking was noticed in the walls, floors, and ceilings and some began to worry about the stability of the structure. The movement of the building and its cracking were monitored and it was determined that the building had stopped settling and that it posed no safety hazards to those inside. Such cracking is not uncommon in the Ozarks where the bedrock has been fractured and dissolved, but the unusual circumstances of the site warranted further investigations. The many cracks and slightly uneven floors present in the building, especially on the higher floors, help add to the legend that the tower is slowly falling over. The building may still be moving very slowly, but the change is so gradual that changes won’t be noticed in many human lifetimes. Upon talking with Jim Murphy, Director of Residential Life and Student Services at UMR, he stated that he is confident that TJ Hall is safe for those visiting and living inside. Based on the relatively conservative design of the foundation, the building’s foundation should be safe from failure.

The settlement and cracks at TJ are likely caused by the creeping of the grade beams. Although the grade beams are made of reinforced concrete 5-6 feet thick, reinforced concrete will creep under sustained load, which has likely allowed parts of TJ to sag between the drilled shafts. This has probably been the cause of the settlement and cracking at TJ.



Reinforced concrete grade beams being laid for TJ South Tower. Notice

worker next to reinforcing steel for scale. These beams have likely sagged

over time, causing settlement and cracking at TJ.

<Click For Additional Picture>

The swimming pool has suffered damage due to settling, as it is not founded on deep foundations. This, over time, has added to the idea about the ground near TJ being unstable.



TJ Hall swimming pool

Notice the settlement cracks near the corner of the pool;

these may be the result of poor construction, as well

as settlement related to the filled sink.









Students enjoy the pool whether or not it is sinking.

Thanks to UMR Archives for the above three photos.

(Notice 1980's Mountain Dew & Crush cans in lower photo)

An architectural detail on the south tower has also helped propagate the legend that TJ is falling over. One may notice a concrete grid pattern on the east side of the south tower and a similar stair step pattern on the west side. Rumors say that this was added after the original construction to serve as a reinforcing frame to help hold the building up. The design is strictly aesthetic and was planned from the very beginning. The intention of the pattern was to blend the south tower with the north tower. The concrete structural columns of the pre-existing north tower are exposed on the exterior of the building. This is part of the design and has nothing to do with the sink structure underneath. From a distance, the grid pattern inherent to the structure of the north tower looks similar to the pattern on the south tower. This was the intention of the designers, as they wanted the buildings to go together. Pictures showing the south tower under construction with the grid may be viewed in the UMR Archives in room G2 at the library.



TJ south tower shown under construction with its superficial white grid

- More pictures of TJ south going up 1, 2, 3, 4, 5, 6, & 7

-Nearly complete east and west views

-Completed building 1, 2, 3, 4, 5, & 6

Both towers color

Pictures courtesy of UMR Archives



Scale model of TJ before the south tower added on - notice the white grid

pattern up to the 7th floor of the south tower to match the existing north tower.

More pictures of the TJ model in black and white 1, 2, 3, 4, 5, & 6

TJ model pictures courtesy of UMR Archives

There are also rumors circulating about the north tower of TJ Hall, as it also shows cracking, especially in the basement. UMR was able to purchase this preexisting building at an extremely low price. The north tower’s original purpose was a dormitory run by a private contractor, much like today’s campus food service. During a period of low enrollment, the occupancy of the dormitory dropped and the contractor had to sell. Rumors say that the building sold cheaply due to structural problems, which were slowed by injecting grout, a concrete like substance, into the subsurface under the building. This rumor has NOT been verified as true or false as of now by the author and records pertaining to the construction of the north tower have been sparse, especially since it wasn’t originally built by the University. As of now, this is nothing more than a rumor/myth/urban legend.

Two filled sinks are clearly visible in the I-44 road cut next to TJ. This feature is known as the Vichy Rd. Filled Sink due to its location just east of the Vichy Rd. overpass in Rolla between I-44 exits 185 and 186. Upon looking east from the overpass, one can see sink structures in both sides of the I-44 road cut. It is thought that this structure is actually two completely separate sinks, as their internal structure is somewhat different. If this is true, the rock dividing the two structures was removed during the construction of I-44.



The Vichy Rd. Filled Sink(s) are filled with sandstones and shales, which are both common sink fillings in the Ozarks. It is thought that the sandstones present in the sinks are simply St. Peter Sandstone that has been eroded and reworked. Small amounts of hematite, an iron oxide based ore, also color portions of the north sink face a purplish color.



The north exposure of the Vichy Rd. Filled Sink contains sandstone, shale,

and purplish staining from hematite. Both exposures are associated with a

a small fault.

It appears that a small steeply dipping fault runs through both exposures of the Vichy Rd. Filled Sink structures, with the western side having been downthrown. The north exposure of the sink shows evidence of shearing and folding. Some of the beds present in the sink are brecciated (highly fractured) and overturned. The bedding in the southern exposure is less chaotic but the bedding dips to near vertical on the eastern side where faulting has occurred. It is possible that the sink structures were developed along this fault, as it is easier for water to circulate and dissolve rock where it is faulted and/or fractured. It is unlikely that this fault will move anytime in the near future, as it has been dormant for hundreds of millions of years! It is likely that the filled sinks under TJ are also related to this fault.

References to this structure are also made on pages 183-184 of “Geologic Wonders and Curiosities of Missouri” (2nd Edition). This book includes pictures of both exposures, with the picture of the southern exposure clearly showing TJ Hall in the background. The caption states that the piers for TJ Hall pass through another sink structure nearby. To those unfamiliar with the area’s geology and the design of the buildings, this small bit of information might lead one to believe that TJ is unstable.



The south exposure of the Vichy Rd. Filled Sink is clearly visible here.

Thomas Jefferson Hall, built on another similar structure, is shown

in the background.



This airphoto taken of TJ in 2002 clearly shows the southern exposure of the

Vichy Rd. Filled Sink, as it's weaker rock has weathered back at a more rapid

rate than the surrounding Jefferson City dolomite.

Thanks to Casey Cotita of UM-Rolla Physical Facilities for the above airphoto.

Due to its large size and easy accessibility, the Vichy Rd. Filled sink is one of the most commonly visited sink structures in Missouri. It is often included in field trip guides and discussed by professors and students studying such structures.

While driving around Rolla and the surrounding area, one may notice a large number of filled sinks. Such structures are most visible in road cuts. Others are noticeable along I-44 both east and west of Rolla. Several highly visible sink structures are present along U.S. Hwy 63 just north of Rolla. Upon entering Northwye, which is just north of Lowe’s Home Improvement Center, one will notice two filled sinks exposed on the right (east) side of the highway. These are visible in the road cut just before the highway narrows from four to two lanes. Another large sink is visible on the east side of the next road cut. Due to the weak natural of the rock filling the sinks, these had to be scaled back in order to prevent failure onto the road surface. Another excellent exposure of a filled sink material is present as one heads west out of Rolla and up the hill past Zeno’s, etc. towards Doolittle. It shows up as inclined shaley beds on both sides of the highway between mile markers 182 and 183, but is closer to marker 182. The host rock for this sink is Roubidoux sandstone. The large number of filled sinks seen in area roadcuts leads one to believe that there must be many more of these structures yet to be uncovered nearby.

Upon visiting the site of Rolla Quarry, a quarry run by Capital Quarries north of Rolla on Jan 31, 2003 for a class field trip, the author noticed a filled sink structure in the western face of the quarry. Upon consulting with the quarry operator, it was found that the filled sink has made quarrying slightly more difficult. The weak, shaley sink filling is of little to no value in most construction projects and cannot easily be sold. It cannot be mixed with most other crushed rock products from the quarry, as shale is detrimental when used as aggregate in asphalt and concrete. A mud filled cave nearby, which was likely related to the filled sink, was discovered and destroyed during quarrying. This material was also considered waste and had to be separated from the rest of the rock material. Perhaps more of this cave will be uncovered as quarrying progresses in the direction of the filled sink. The filled sinks along Hwy 63 and in the one in the quarry are also developed in the Jefferson City dolomite.



The filled sink within Capital Quarries' Rolla Quarry is filled with shales and

some sandstone. It is very easy to see, as the face is relatively unweathered

due to its recent exposure by the quarrying. A small mud filled cave

was exposed while quarrying nearby.

Click links below for more pictures.

-Another picture, slightly farther back, of the same filled sink

-Crushing and processing equipment within the quarry

(part of filled sink visible as small white area at very left of picture)

The filled sink structure under TJ and those nearby are not an unusual phenomenon in the Ozarks, as the known number of similar structures number in the thousands. There are probably many more that have yet to be discovered. The Ozarks have gone through at least two past erosional episodes in which karst features developed. Evidence indicates that many of the caves we can enter today and many of the conduits serving large Ozark springs were formed during these times. After the erosional episode, sea level rose, covering the area and depositing marine sediments. Some of these filled sink structures are thought to be old sinkholes that were simply filled with sediments. Others seem to have a more mysterious origin. One theory presented by Gregg and Shelton is that such sinks later became paleosprings, which drained the subsurface as the Ouachita Mountains in Arkansas were uplifted. This theory states that mildly hydrothermal (80-180 degrees C) waters moving through the subsurface concentrated minerals and deposited them at locations where the water chemistry was no longer conducive to keeping minerals in solution, depositing the MVT (Mississippi Valley Type) mineral deposits in Missouri. This theory mainly explains the metallic deposits in the area. There are other theories on how the sinks were formed but no one has been able to verify any as fact.

Robert Dillon’s 1999 dissertation highlights studies of the clay mining district near Owensville. During his research, dye tracing was conducted. His traces indicate that there is a high level of subsurface connection between the claypits and underground drainage, indicating that subsurface conduits are present. Approximately 20% of the 1,256 studied claypits do not hold water.

Filled sinks are developed in multiple formations throughout the Ozarks, and not just the Jefferson City Formation. It seems that a large proportion of the sink structures are developed along faults, which must be partly due to the fact that these natural weaknesses in the rock allow groundwater to circulate and dissolve more readily. Whatever geologic phenomenon led to the creation of these structures worked on essentially all the carbonate based rock types of the Ozarks. Some rock formations deposited in the geologic past have been destroyed by erosion, but evidence of these otherwise unknown rock types has only been preserved in the filled sinks. This is just one reason why these structures are of such interest to geologists.

The numerous filled sinks of the Ozarks have played an important role in the economic development of Missouri. In prehistoric times, Indians used the sink fillings for face paint. Early settlers to the Ozarks took advantage of the sink fillings which were mined up to the earlier half of the 1900’s. Some sinks contain high quality fireclays, which can be used in ceramics and high temperature refractory products, while others contain metallic minerals and even coal. A general rule of thumb is that the sinks north of I-44 contain clays while those south of the highway contain heavier metallic minerals. There are exceptions to this rule of course.

Early mining of sink fillings provided material for the Maramec Iron Works at the site of the present day Maramec Spring Park. The original iron ores smelted in the Maramec furnace originated from a large hematite and pyrite filled pit about one half mile away from the spring. Ores from other nearby pits were also processed at the furnace. Other iron-filled pits were later discovered in the Newburg area. Thomas James, who started the Maramec operation, later built a second furnace at the Ozark Iron Works along the Little Piney near Newburg, MO. Multiple furnaces sprung up around the Ozarks until larger deposits of iron were discovered in Michigan and the filled pits of the Ozarks became unprofitable to mine. The James Foundation, which runs Maramec Spring Park, has done an excellent job of highlighting the history of the area in the museums on the site. The furnace and other parts of the iron works are still visible on the site. The Ozark Iron Works is still present but is located on private property. The remains of other iron works are scattered throughout the Ozarks on both private and public lands. Other filled sinks in similar areas were mined for lead (mainly in the form of the mineral galena), zinc, and copper ores.



The Maramec Iron Works processed ore mined from

nearby filled sink structures in its furnace.

To the north of I-44, clay filled sinks have served to provide refractory or fireclays for ceramics and other high temperature uses and ingredients for cements. Missouri fireclays are used in firebrick. During World War II, Missouri firebrick was used to line the boilers of ships serving in the war. During the Apollo space missions, the launch pads at Cape Canaveral were made of Missouri refractory clays. Areas near Mexico, Owensville, and Rolla, MO once provided large quantities of these clays for industry. In recent years, the fireclay industry in Missouri has declined, although mining still occurs near Mexico, Owensville and other locations. At least 1,256 claypits are known in the area and any topographic map of the vicinity will show numerous old mines simply labeled as “claypits.”

Other filled sinks were once mined for coal. Some sinks contain a mixture of coal and another material such as clay or a metallic mineral deposit. The coal was most likely deposited when the sinks contained swamps, which allowed organic matter to accumulate and later be turned into coal. Once such sink was mined for clay and coal near the present day rest area along I-44 at St. Clair Missouri. Construction has destroyed most of the evidence of this structure, but some brecciated and tilted rocks may be seen in the roadcut near mile marker 235, especially from the westbound lanes. This structure is associated with another fault named the Anaconda Fault, which has also been dormant for hundreds of millions of years.

Some filled sinks, such as the ones exposed at the quarry in Rolla are filled with impure clays/shales, which are essentially a junk rock. One cannot build atop these structures without expecting some settlement and the material is not useful for other construction or industrial purposes. These are a nuisance to all but geologists.

Some filled sinks serve other uses, including landfills, after they are mined out. A claypit across I-44 from Lowe's Home Improvement Warehouse in Rolla was once mined for its clay filling and then filled with trash. After filling, this pit was covered with a layer of clay and junk rock.

Another filled sink is located in a road cut on Missouri Hwy 100 on the line between St. Louis and Franklin Counties. As with many other sinks, this one is present in a zone of faulted and folded rock along a geologic structure known as the Eureka Anticline.

Filled sinks may or may not show up at the ground surface without being trenched or bored through. Sinks filled with shales tend to erode and the same rate is surrounding rocks unless they are present in the side of a hill. These often blend into the landscape and don’t appear until being dug into. Filled sinks with a resistant sandstone rimrock, or liner, tend to show up more readily on the surface, unless they are present in the similar looking Roubidoux sandstone.

Features known as blossom rocks tend to stand above the surrounding landscape. These structures are made of sandstone and also have undetermined origins. Some believe that these structures are portions of old caves that have been filled with more resistant sandstone while others theorize they might be eroded remnant portions of filled sinks. Blossom Rock (also known as Yancy Mills Sandstone Exposure) at the Lane Spring Recreation Area in the Mark Twain National Forest about 13 miles south of Rolla is an excellent example of such a structure. There are at least six notable blossom rock type structures within the Rolla 15 minute quadrangle map. Similar structures with larger pebbles and cobbles included in their matrix are often referred to as cave conglomerates.



Blossom Rock at the Lane Spring Recreation Area is thought to be the

sandstone infilling of an ancient cave or sinkhole.

Other similar structures known as circle deposits sometimes contain metallic ores and broken rock. These may either be a portion of a now filled cave, formed by deposits coming in through an ancient sinkhole above. Others believe them to be formed when underlying rock slowly dissolves and overlying materials slowly subside while becoming fragmented. All of these structures are roughly circular, where caves are usually more linear.

Filled caves (roofed cavities with a secondary filling) are also present throughout the Ozarks. Many are simply filled with clay, as any Ozark caver knows. Others are filled with mineral deposits of economic value. Some were exposed in the mining of other ore bodies. It has been theorized that the Viburnum Trend mineral deposits of Missouri formed through the filling of large ancient caves, as there extent looks much like that of modern day caves in plan view. At least two filled caves, one filled with shales and the other with iron ore, are present near the Rolla Quarry.

The above mentioned paleokarst features are just a few of the thousands known in the state. Anyone wanting to learn more on the subject should consult the references mentioned below. Although this article may have shed light on one of the stories behind Thomas Jefferson Hall, there are still many questions yet to be answered about the formation of the filled sinks and other paleokarst of the Ozarks as a whole.

Thanks to Jerry Vineyard (Retired Deputy State Geologist of Missouri), Mike Siemens (Geologist, MoDNR - GSRAD), Alfred C. Spreng (UMR Professor Emeritus), Gerald Rupert (UMR Professor Emeritus), Casey Cotita and others at UMR Physical Facilities for their pictures and information on the design of TJ Hall, Jim Murphy (Director of UMR Residential Life and Student Services) for his information on TJ, Melody Lloyd of the UMR Archives (http://www.umr.edu/~archives), “Geologic Wonders and Curiosities of Missouri” by Vineyard and Beveridge, “Guidebook To The Geology of The Waynesville, Rolla, And St. James Areas, Missouri” by Spreng and Proctor, US Geological Survey (http://geology.er.usgs.gov/paleo/geotime.shtml), “Caves of Missouri” by J Harlen Bretz, “Geomorphic History of The Ozarks of Missouri” by J Harlen Bretz, and “Origin of The Filled Sink-structures And Circle Deposits of Missouri: Geological Society of America - Bulletin v. 61” P. 789-834 by J Harlen Bretz for information used in this article. Two sources with more recent UM-Rolla connections were also used. Pages 81-99 of “Basin-Wide Diagenetic Patterns: Integrated Petrologic, Geochemical, And Hydrologic Considerations – Society for Sedimentary Geology Special Publication No. 57” edited by Isabel P. Montanez, Jay M. Gregg, and Kevin L. Shelton contains a subsection titled “Sedimentary Facies Control of Fluid Flow And Mineralization in Cambro-Ordovician Strata, Southern Missouri” by Zhenhao He, Jay M. Gregg, Kevin L. Shelton, and James R. Palmer. Dr. Jay Gregg is Chair of the Dept. of Geology And Geophysics at UMR. A 1999 Doctoral dissertation from the UMR Dept. of Geology and Geophysics by Robert Dillion titled “Stability of Paleosinks And Karstic Carbonates In The Southern Fire Clay Mining District of Missouri” was also consulted.