The Gasconade River is a northeast and north-northeast oriented Missouri River tributary and flows from near Seymour, Missouri to join the east-oriented Missouri River, near Gasconade, Missouri. Major Gasconade River tributaries include north-oriented the Osage Fork, Roubidoux Creek, and the Big Piney River. This Gasconade River overview provides a summary of essays describing landform origins for all drainage divides surrounding the Gasconade River drainage basin. Essays being summarized are based entirely on illustrated topographic map evidence and interpret landform origins from a previously unexplored perspective of a deep glacial erosion and a thick ice sheet that melted fast paradigm. Topographic map evidence shown and discussed in these essays documents how the deep Gasconade River valley and its north-oriented tributary valleys were eroded by systematic reversals of an immense south-oriented flood, which was derived from a rapidly melting North American ice sheet. Prior to headward erosion of the deep Missouri River valley flood waters flowed south across what is now the Gasconade River drainage basin to what was then the newly eroded southeast-oriented White River valley and what were then actively eroding south-oriented White River tributary valleys. Headward erosion of the deep east-oriented Missouri River valley beheaded the south-oriented flood flow routes in sequence from east to west. Flood waters on north ends of beheaded flood flow routes reversed flow direction to erode deep north-oriented valleys. The actively eroding north-oriented valleys captured significant south-oriented flood flow from west of the actively eroding Missouri River valley head. The captured flood water moved in southeast, east, and northeast directions and caused the north-oriented valleys, such as the Gasconade River valley, to erode headward toward the southwest and to also behead south-oriented flood flow routes in sequence from east to west. The Gasconade River valley was able to erode headward for a significant distance faster than the actively eroding Missouri River valley and its Osage River tributary valley were able to behead south-oriented flood flow routes supplying flood waters to the actively eroding Gasconade River valley. Headward erosion of the deep Osage River valley from the actively eroding Missouri River valley finally beheaded and captured all flood flow routes to the what had been the actively eroding Gasconade River valley. Essays upon which this overview essay is based illustrate and discuss how topographic map evidence including positions and orientations of present day valleys, the nature of Gasconade River valley and tributary valley meanders, and through valleys crossing present day drainage divides, provide evidence supporting this flood origin interpretation (the detailed essays can be found under Gasconade River on the sidebar category list).

Gasconade River drainage basin location map

Gasconade River drainage basin history

The Gasconade River drainage basin is located south central Missouri and drains to the northeast and north-northeast oriented Gasconade River, which flows to the east-oriented Missouri River, which in turn flows to the south-oriented Mississippi River. Major north-oriented Gasconade River tributaries include the Osage Fork, Roubidoux Creek, and the Big Piney River. The Gasconade River and its major north-oriented tributaries are among many major Missouri River tributaries, which flow in a north direction to join south-oriented drainage system. Why do Missouri River tributaries flow in a north direction to join a south-oriented drainage network? It is tempting to say the Gasconade River and other Missouri north-oriented rivers and streams (seen on figure 1) predate North American glaciation and were captured by headward erosion of the Missouri River valley along an ice sheet southern margin. There is some logic in that explanation. Headwaters of the Gasconade River and its major tributaries are located in the Ozark Plateau area of southern Missouri, which is generally higher in elevation than areas further to the north. In fact it could be argued the Ozark Plateau higher elevations provided a barrier limiting ice sheet advances.

• While attractive at first glance the pre-glacial north-oriented drainage explanation does not explain how and when north-oriented river and stream valleys were eroded, nor does such an explanation explain how the east and northeast-oriented Osage River valley was formed, unless an ice sheet advanced to near the Osage River valley location and the Missouri River valley to the north was eroded along a different or at least a later ice sheet margin. Further, the pre-glacial north-oriented drainage explanation does not explain many landform features best seen on detailed topographic maps. Among the unexplained features are the unusual incised meanders found along the Gasconade River route, southeast and south oriented barbed tributaries flowing to the northeast and north-northeast oriented Gasconade River, the asymmetric Gasconade River-White River drainage divide found along the Gasconade River southern margin, and the presence of numerous through valleys eroded across all present day Gasconade River drainage basin drainage divides. This topographic map evidence cries out for a different explanation than the pre-glacial north-oriented drainage explanation. Based on this topographic map evidence the more detailed essays explain Gasconade River drainage basin evolution in the context of an immense south-oriented glacial melt water flood, with flood flow routes beheaded and reversed in sequence by headward erosion of the deep east-oriented Missouri River valley and its tributary valleys.

• South of the Gasconade River drainage basin is the southeast and south-southeast oriented White River drainage basin. In figure 1 the White River flows from Table Rock Lake (Reservoir) to Bull Shoals Lake (Reservoir) and then in a southeast and south-southeast direction to eventually join the south-oriented Mississippi River. Most south-oriented streams flowing to the figure 1 south edge, including the Black River in the figure 1 southeast quadrant, are White River tributaries. The Gasconade River-White River drainage divide is an asymmetric drainage divide, with the White River tributaries generally having steeper gradients along the drainage divide. Figure 2 below illustrates the asymmetric drainage divide near Mountain Grove, Missouri. The south oriented stream is the North Fork River, which flows in a south direction to eventually join the south-southeast oriented White River. North-oriented drainage in the figure 2 east half flows to north oriented Beaver Creek, which flows to the north and northeast-oriented Gasconade River. West and north-oriented drainage in the figure 2 west half flows to north-oriented Whetstone Creek, which also flows to the Gasconade River.

• Asymmetric drainage divides, such as the drainage divide in figure 2, are not normally formed by random erosional processes acting over long periods of time and provide evidence of unusual erosion events. Through valleys crossing the Gasconade River-White River drainage divide provide evidence significant volumes of water once flowed across the drainage divide. Similar through valleys can be found all along the present day Gasconade River-White River drainage divide suggesting the flow was not confined to just a few channels, but moved across the entire drainage divide, which suggests a massive flood once crossed the drainage divide. The asymmetric nature of the drainage divide strongly suggests the water was flowing from the north to south. But all drainage routes north of the drainage divide are north-oriented drainage routes. Where did the large volumes of south-oriented water come from and how did those large volumes south-oriented water flow in what is now an uphill direction to reach the present day Gasconade River-White River drainage divide?

Figure 2: Gasconade River-White River drainage divide area near Mountain Grove, Missouri. The Gasconade River drainage basin is located north and west of the drainage divide and the White River drainage basin is located south and east of the drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

The Gasconade River-White River drainage divide becomes even more complex further to west at the Gasconade River headwaters, near Seymour, Missouri. Figure 3 below illustrates the Gasconade River headwaters east and north of Seymour. The asymmetric west to east oriented Gasconade River-White River drainage divide can be seen south of the highway in the figure 3 southeast quadrant. Note how the Gasconade River begins as a southeast-oriented stream in the figure 3 north center area and then turns to become a northeast-oriented stream in the figure 3 east half. Also, note west of the Gasconade River headwaters are headwaters of the west and northwest-oriented James River. West of the figure 3 map area the James River flows in a northwest direction before turning to flow in a southwest and south direction to join the White River. Note how in figure 3 the James River-Gasconade River drainage divide is asymmetric, but the steeper gradient along this drainage divide is on the Gasconade River side. How is it possible for the Gasconade River-White River drainage divide to be asymmetric in two completely different directions?

Figure 3: Drainage divides in the Gasconade River headwaters area near Seymour, Missouri. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

The explanation for the drainage divide evidence shown in figures 2 and 3 is massive south-oriented floods once flowed across the entire present day Gasconade River drainage basin and adjacent drainage basins. Flood waters were derived from a rapidly melting North American ice sheet and at that time there was no Missouri River valley north of the Gasconade River. Further, at that time elevations in the present day Gasconade River drainage basin were different from what they are today, meaning flood waters could freely flow south across the Gasconade River drainage basin to what was then the actively eroding White River drainage basin to the south. Headward erosion of the deep Missouri River valley north of the Gasconade River drainage basin then beheaded south-oriented flood flow routes in sequence from east to west. Flood waters on north ends of beheaded flood flow routes reversed flow direction and began to erode deep north-oriented valleys. The north-oriented Gasconade River valley was one of those deep north oriented valleys.

• How did south-oriented flood water erode a major north-oriented valley and its major north-oriented tributary valleys? Once the deep north-oriented Gasconade River valley was initiated it began to capture south-oriented flood water flowing on flood flow routes west of the actively eroding Missouri River valley head. The captured flood water next moved in southeast, east, and northeast directions to reach the actively eroding Gasconade River valley head. Southeast, east, and northeast oriented flood channels next influenced the direction the Gasconade River valley headward erosion took. At times the Gasconade River valley eroded headward along northeast-oriented flood flow routes, and at other times the valley eroded headward along a southeast-oriented flood flow route. At still other times the Gasconade River valley beheaded a south or southeast oriented flood flow route and eroded headward along a reversed flood flow route. This erratic erosion pattern is recorded by the Gasconade River valley route, which displays large incised meanders, such as those shown in figure 4.

• Gasconade River valley headward erosion also beheaded south-oriented flood flow channels in sequence from east to west. Flood waters on those south-oriented flood flow channels reversed flow direction to erode deep north-oriented valleys. Those deep north-oriented valleys also captured flood waters moving south on flood flow routes west of the actively eroding Gasconade River valley head. The captured flood flow then moved in southeast, east, and northeast directions to those new north-oriented valleys, which are today north-oriented Gasconade River tributary valleys. The asymmetric Gasconade River-White River drainage divide was eroded by south-oriented flood waters flowing to what were then actively eroding south-oriented White River tributary valleys. Flood flow across the Gasconade River-White River drainage divide was beheaded and reversed in sequence from east to west as the deep Gasconade River valley eroded headward.

• The asymmetric James River-Gasconade River drainage divide in figure 3 was eroded by south-oriented flood flow from west of what was then the actively eroding Osage River valley head. The south-oriented flood water was captured by headward erosion of the deep northeast and north-northeast oriented Gasconade River valley and was moving in a southeast direction to the actively eroding Gasconade River valley head. Captured south-oriented flood flow from west of the actively eroding Osage River valley head and moving in a southeast direction to the Gasconade River valley head provided the immense water volumes needed to erode the deep Gasconade River valley. Headward erosion of the south-oriented James River valley from what was then the newly eroded southeast and south-southeast oriented White River valley beheaded the southeast-oriented flood flow routes to the actively eroding Gasconade River valley head. Flood waters on southeast ends of  beheaded flood flow routes reversed flow direction to erode the northwest-oriented James River headwaters valley and to create the asymmetric James River-Gasconade River drainage divide.

Figure 4: Gasconade River valley meanders illustrating how the deep north oriented Gasconade River valley eroded headward along multiple reversed flood flow routes as well as captured flood flow routes. For example, south and southeast-oriented valley segments were eroded headward along south and southeast-oriented flood flow routes while north and northwest oriented valley segments were eroded headward along beheaded and reversed south and southeast-oriented flood flow routes. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Today it is difficult to look at the Gasconade River drainage basin and to image it was eroded by an immense south-oriented flood. It is difficult to imagine a North American continent without the Missouri River drainage network, or at least segments of that drainage network. Yet at the time the Gasconade River drainage basin was eroded the Missouri River drainage network did not exist. Most if not all of the Missouri River valley and its tributary valleys had yet to be eroded, much less integrated to form what we know today as the Missouri River drainage basin. Volumes of flood water required to erode and form the Gasconade River drainage basin, much less the much larger Missouri River drainage basin, were much greater than any floods described in the existing geologic literature. When flood waters first flowed across what is today the Gasconade River drainage basin regional elevations were such that flood waters could freely move in a south direction. Present day elevations, where the Gasconade River drainage basin is higher in the south than in the north, are the result of deep flood water erosion and perhaps also the result of regional warping or uplift. The essays upon which this overview essay is based make no effort to determine how much material was removed from the Gasconade River drainage basin, although the essays do present evidence for significant deep flood water erosion.

Missouri River drainage basin research project essay series

This Gasconade River drainage basin landform origins overview essay is one of a series of  Missouri River drainage basin landform origins research project overview essays. The research project essay series goal is to use topographic map evidence to describe the evolution of drainage divides separating each significant present day Missouri River tributary valley and also to describe the evolution of drainage divides separating the present day Missouri River drainage basin from adjacent drainage basins. Each overview essay in this series relates to a specific Missouri River tributary, tributary to a present day Missouri River tributary, or a present day Missouri River valley segment. Each overview essay provides a summary of several much more detailed essays which illustrate and discuss topographic map evidence describing the evolution of a secondary drainage divide area within the overview essay geographic region. The Missouri River drainage basin research project series is being developed one essay at a time and overview essays are added as significant tributaries are reached. More detailed essays upon which this overview essay is based can be found under the Gasconade River on the sidebar category list. Overview essays and detailed essays relating to adjacent drainage basins can be found under appropriate river or Missouri River segment names on the sidebar category list.

• The Missouri River drainage basin research project introduces a new regional geomorphology paradigm. An essay titled “About the ‘thick ice sheet that melted fast’ geomorphology paradigm” provides a brief introduction to the new paradigm and how the new paradigm emerged. Detailed evidence illustrated and discussed in the Missouri River drainage basin research project essay series builds a strong case for (1) deep glacial erosion of the North American continent by a thick North American ice sheet that created and occupied a deep “hole”, (2) rapid melting of that thick North American ice sheet, (3) immense floods of south-oriented melt water, (4) headward erosion of deep east, northeast and north-oriented valley systems to capture the south-oriented melt water floods and to divert the melt water further and further northeast into space the ice sheet had once occupied, (5) deep flood water erosion of the North American continent surface, and (6) crustal warping that resulted in uplift of mountain ranges and other regions as flood waters were deeply eroding what are now high mountain regions and other high elevation areas. This interpretation is fundamentally different from most previous interpretations. The Gasconade River drainage basin evidence in this much larger Missouri River drainage basin landform origins research project essay series is presented for review and discussion by qualified research geomorphologists and geologists.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.