The geology of Missouri is mainly composed of rocks from Proterozoic to the Paleozoic-age, with Mesozoic and Cenozoic in the southeastern part of the state (Thompson, 1995), and unlithified units ranging from Holocene back to possibly Miocene-age (Thompson, 1995). These rocks may reveal alternating force regimes of compression and extension that appear to be mitigated by underlying Proterozoic lineaments (McCracken, 1971)(Kisvarsani, 1979). The geologic history of Missouri has generally been interpreted as one of relatively stable periods of deposition punctuated with periods of epeirogenic uplift and subareal exposure (McCracken, 1971). There are features exposed in the bedrock that could indicate a more complex tectonic history, largely controlled by the late Proterozoic structures in the basement rock under the state.
Through most of its geologic history, Missouri existed as a shallow carbonate ramp accumulating shallow marine limestones, sandstones, dolomites and shales, with occasional clastic contributions from the St. Francois Mountains in southeastern Missouri and the Central Kansas Uplift in Kansas (Thompson, 1995). These deposits alternate between shallow marine and clastic in the Cambrian (Thompson, 1995), are mainly shallow marine in the Ordovician, Silurian and Devonian, are mostly shallow marine in the Mississippian, and become more cyclothemic and clastic in the Pennsylvanian, which is approximately the end of marine deposition in most of Missouri, as the crust is uplifted and the waters covering the Mississippi Embayment recede out of the state. There is a small, Cretaceous-age intertidal deposit along the edge of the Ozark Escarpment in southeast Missouri that marks the final marine deposition in the Ozarks. Some deposits in the Bootheel continue deposition of marine sediments into the late Cretaceous (Thompson, 1985). The formations of the Mississippi Embayment in the Bootheel region of Missouri grade from para-lithified material to barely compressed sediment. But they cover the most tectonically active region in the state.
There have been at least seven episodes of epeirogenic uplift (McCracken, 1971) in the geologic history of the state, as recorded by the development of paleokarst (Gregg, 1988) and the unconformities between various formations and epochs (Thompson, 1995). Geologic strata generally dip down and away from the Proterozoic volcanics of the St. Francois Mountains. Underlying all these strata are two vaguely defined and roughly mapped igneous provinces that may be 'pulling the strings' on many of the features and phenomena observed in the present-day geology of Missouri.
Previous Lineament Research
The basement rocks of Missouri are divided into three provinces. Two of these provinces underly most of Missouri: the Central Plains Orogen, composed of metamorphics and granites (Kisvarsanyi, 1979), and the Grenville Province, which is composed of rhyolites and granites(Kisvarsanyi, 1979). These large masses of igneous and metamorphic rock formed 1.3-1.4 billion years ago (Berry and Bickford, 1971). These ancient terranes have large linear suture zones that may represent faulted accretionary prisms of continental crust from island arcs and proto-continents. These fault systems may express themselves in later geologic formations that are currently observable at the surface in the form of lineaments and associated perpendicular fractures. These features may affect the distribution of stresses that become seismic events in the New Madrid Seismic Zone and the accumulation of potable and mineralized groundwater into aquifers and ore deposits.
The Central Plains Orogen
2. Maps showing approximate contact between the Central Plains Orogen and the Grenville Orogen. Note the boundary between the two orogens that is roughly parallel with the Reelfoot Rift to the southeast. These three maps emphasize that researchers are not in agreement with the approximate divisions of these igneous provinces. (Sims and Peterman, 1986)(Bleeker, 2008)(Csontos, 2008 adapted from Van Schmus, 1996)
A map of the tectonic structures of Missouri produced by the Missouri Geological Survey (McCracken, 1971) shows that much of the geology to the west and northwest of the St. Francois Mountains appears to be controlled by normal faults that trend from the northwest to the southeast. These faults parallel underlying lineaments in the Central Plains Orogen. Most of these faults align in roughly the same trend. Some faults trend perpendicular from the southwest to the northeast, but these could be graben structures (Seeger and Palmer, 1998), or joints in the overlying dolomites and limestones that are a function of solution weathering (Van Dike, 1979) and unloading stresses (Ritter et. al, 2002).
The Grenville Orogen
The Grenville Orogen follows the southern boundary of the Central Plains Orogen. It is composed of granite and rhyolite, some of which can be seen in the exposed igneous knobs of the St. Francois Mountains in southeast Missouri. These rocks are approximately 1.3-1.4 billion years old (Berry and Bickford, 1971) and are the oldest rock exposures in Missouri.
3. Photos of the St. Francois igneous rocks taken by the author. The light pink rocks are coarse-crystalline granite (intrusive), the dark purple rocks are fine-crystalline rhyolite (extrusive). Different researchers disagree on the age and boundary of these Proterozoic provinces (Van Schmus et.al, 1996)(Bleeker, 2008).
The Proterzoic map of Missouri is based on a limited number of drill holes that penetrated the Proterozoic basement at the time of its publishing (Kisvarsanyi, 1979). The lineaments in western and northwestern Missouri (McCracken, 1971) could represent differential stresses based on lithologic differences within the Central Plains Orogen. These parallel structures could act to distribute tectonic stresses along their shear planes, and in turn transmit some of this energy to the surface, generating the lineaments that have been observed in NASA photos (Kisvarsanyi, 1975) and field-truthed as being actual physical features (Kisvarsanyi, 1975).
4. Map from McCracken (1971) showing Proterozoic structures and lineaments.
5. Drawn from McCracken (1971) and Kisvarsanyi (1975), the author has generated this map in ArcMap, meant to portray that such lineaments may provide structural control on the Mississippi and Missouri Rivers. Bends that can be observed along the northwestern Missouri border with Kansas and Nebraska; in central Missouri near Columbia and Booneville; and along most of the Mississippi River between Missouri and Illinois all trend in the general direction of underlying Proterozoic lineaments. In the Bootheel Region, the Mississippi River could be turning towards the west under the influence of the Reelfoot Rift and the underlying boundary between the Grenville Orogen and the Appalachian-Ouachita Trough (Ouachita-Appalachian map from Lowe, 1985).
New Madrid Seismic Zone
A vast body of research exists for the New Madrid Seismic Zone (NMSZ) since the first historically recorded temblors in the winter of 1811-1812. This seismological research has defined the structure of the Reelfoot Rift, which lies beneath hundreds of meters of sediment that has been deposited in the topographic low of the Reelfoot Graben since the Cretaceous. The graben is a tensional structure that trends from the southwest to the northeast, roughly parallel to the boundary between the Grenville Orogen and the Ouachita-Appalachian Margin. Some research indicates that the Reelfoot Rift, the Ouachita Trough and the Southern Oklahoma Aulacogen are related to the same Proterozoic suture zone (Lowe, 1985). The Reelfoot Rift is generally seen as a failed rift arm, but also appears to have had substantial compressive forces at work to the north of it.
6. Reelfoot Rift mapped in DEM image (Csontos, 2008). Note the southwest-northeast trend similar to the Grenville-Ouachita Trough boundary.
7. Image of the Reelfoot Rift from Csontos (2008) showing the elevation of the structures of the rift, along with possible connections with other fault zones, including the Bolivar-Mansfield Tectonic Zone (BMTZ).
8. Geologic and structural map of the Bootheel in southeast Missouri. Generated by the author in ArcMap.
As the seismic zone turns and trends to the northwest along the eastern margin of the St. Francois Mountains, it appears to become a compressional feature at the surface, marked by the occurrence of Silurian-age rocks that parallels the Mississippi River. This structure also displays the most concentrated area of reverse faulting in the state (McCracken, 1971)(Missouri Environmental Geology Atlas, 2007), further indicating it is compressional in nature. The Simms Mountian and Ste. Genevieve fault systems bound this eastern edge of the St. Francois Mountains. Further into the St. Louis metropolitan area, the NMSZ is found Paleozoic-age rocks in the Dupo-House Springs Anticline, a complex of inactive faults. North of St. Louis, there is a large anticline, the Lincoln Fold, that appears to be structurally related to all these features to the south, but has no recent history of significant seismic activity (Van der Pluijum et. al,1996).
Simms Mountain and Ste Genevieve fault systems, and other faults north of the Reelfoot Rift. Note the northwest-southeast trend consistent with Proterozoic lineaments predicted to control other similarly trending structures in the state.
9. Simms Mountain and Ste. Genevieve fault systems. Generated by author in ArcMap.
The Dupo and House Springs Anticlines are inactive faults propagating through Paleozoic-age rocks in the St. Louis metropolitan area. Though these faults do not appear to be active, they are considered 'seismic hazards' by the Nuclear Regulatory Commission in that they could act as zones of weakness in the event of a large earthquake in the New Madrid Seismic Zone. Seismological impacts in the recent past in this area were due to damage from surface waves, and not seismic waves traveling in the subsurface (Gaunt, 2010)
10. Dupo and House Springs Anticlines. Generated by author in ArcMap.
The Lincoln Fold is a large anticline that dominates the geology of eastern Missouri. The deposition of the Pennsylvanian-age Moberly channel sands appears to indicate that the Lincoln Fold may have once been topographically high enough to cause the surface hydrological gradient of this area to flow from east to west (Missouri Environmental Geology Atlas, 2007), the opposite of the surface gradient today. Faults of significant length bound it, and past displacement has brought Ordovician-age rocks to the surface (Thompson, 1995). It is roughly parallel to the Dupo-House Springs anticlines, and may be the northern part of a faulted regional anticline that includes those three structures.
11. The Lincoln Fold. Generated by author in ArcMap.
The Bolivar-Mansfield Fault Zone transects southwest Missouri from the Kansas border near Amoret, Missouri, to the Grand Gulf Fault System near Thayer, Missouri at the Arkansas border. Csontos (2008) hypothesizes that the 'Bolivar-Mansfield Tectonic Zone' connects to the Reelfoot Rift under northeastern Arkansas. This fault/ tectonic zone appears show significant normal faulting and bedrock displacement through time, with the Ordovician-age Jefferson City-Cotter Dolomite exposed on the upthrown side of the fault and the Mississippian-age Burlington-Keokuk Limestone on the downthrown side.
12. The Bolivar-Mansfield fault zone. Generated by author in ArcMap.
Above and Below
The influence of lineaments can be observed at the surface over large areas of the state. They can stretch for over a hundred miles, and often intersect areas of geologic significance. Grand Gulf State Park, in south-central Missouri, is one of the largest karst features in the state. It is a collapsed cavern system formed in the Ordovician-age Jefferson City-Cotter Dolomite. While the collapse does not appear to have been related to seismic activity, the formation of the Grand Gulf cavern system may have been due in part to the presence of the lineament that may have formed Bolivar-Mansfield fault. This lineament has been shown to be a preferential pathway for the flow of groundwater. With greater amounts of chemically aggressive groundwater able to move faster in the subsurface, larger karst features like Grand Gulf could form in this area. Lineaments may also provide structural and hydrogeologic controls on the large cave and spring systems found in the south-central Ozarks to the east of Grand Gulf (Vineyard, 1982), as well as controlling the flow of surface water in streams and rivers. Waters entering Grand Gulf have been shown by dye tracing to be part of the karst groundwater zone that discharges at Mammoth Springs, the largest spring in Arkansas, approximately 8.5 miles to the south.
13. The Thayer fault zone in south-central Missouri. Generated by the author in ArcMap based on Hedden (1968).
Kisvarsanyi (1975) mapped 'photo-lineaments' in satellite imagery as part of a NASA research mission. They may also influence the flow of Mississippi Valley-Type (MVT) fluids in host rocks in eastern and southern Missouri (Kisvarsanyi, 1975). These mineral-rich fluids have deposited ores of lead, iron, zinc, copper and other metals in economically recoverable bodies (Clendenin, 2009). Some of the lead-rich areas in southeast Missouri have been in production for over 200 years (Seeger and Palmer, 1998). It can also bee seen that these lineaments distribute tectonic forces throughout the bedrock of the state from surface to basement. Researchers disagree on if these faults are seismically active to any significant degree. Outside of the Reelfoot Rift, there are generally only small earthquakes averaging Magnitude 4 or less (Gaunt, 2010).
From evidence seen at the surface and with the limited subsurface investigation that has been performed, it appears that Proterozoic structures continue to influence the surface geology of Missouri. The Reelfoot Rift is the most active structure originating in Proterozoic rocks, periodically releasing large seismic events that alter the surface geology and hydrology, as well as human settlement in the area. Most towns in the Bootheel are located on high, sandy areas that have been interpreted as large liquefaction features generated by past earthquakes.
14. Light areas in photo are liquefaction features, sand blows from seismic events north of New Madrid, Missouri, which the New Madrid Seismic Zone takes its name from. Generated by the author from digital orthoquad photographs in the Missouri Environmental Geology Atlas (2006).
The faults and structures visible on the eastern flank of the St. Francois Mountains provide surface exposures of possible subsurface structures. These fault systems display a faulted horst and graben topography that could be analogous to the structure of the Reelfoot Rift. If so, the history of alternating stress regimes could also be more complex. While there is no current evidence that this fault system is in seismic connection with the Reelfoot Rift, it has been known to generate its own earthquakes in the past (Gaunt, 2010).
The cycle of uplifting, normal faulting and development of a horst and graben topography would indicate an extensional stress regime throughout most of the geologic history of Missouri. But the formation of large structural anticlines in eastern Missouri and the development of large syncline and anticline 'fields' in northern Missouri and the identification of reverse faults on the eastern flanks of the St. Francois Mountains may indicate that compressional forces in the geologic past. Perhaps these periods of compression are limited to the punctuated episodes of uplift that are preserved in the Paleozoic rock record. Or perhaps they are ongoing processes at depth that are masked by solution weathering and a 'shallow' tensional stress regime that is dominant at the surface. The Proterozoic basement of Missouri may have compressional forces acting on it that come from distant, large-scale tectonic features.
Despite all the possibilities that exist in the interpretation of the geology of Missouri, there is a body of evidence suggesting that Proterozoic-age faults and lineaments do influence geologic structures in Missouri.
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Gaunt, D., 2010, personal communications
Gregg, J., 1988, Origins of dolomite in the offshore facies of the Bonneterre Formation (Cambrian), southeast Missouri, SEPM Special Publications
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