Use of Stream and Dismembered Stream Valleys Now Crossing Wyoming’s Northern Laramie Mountains to Test a Recently Proposed Regional Geomorphology Paradigm, USA

Detailed topographic maps show multiple stream valleys and what are probably dismembered stream valleys that extend completely across Wyoming’s northern Laramie Mountains. Several of the most obvious valleys are described with valley origins first explained (or attempted to be explained) from the commonly accepted regional geomorphology paradigm (accepted paradigm) perspective and second from a recently proposed regional geomorphology paradigm (new paradigm) perspective in an effort to determine which of the two paradigms provides the simplest explanations. Accepted paradigm explanations require at least some of the valley erosion to have occurred prior to deposition of Oligocene and Miocene sediments that once covered the northern Laramie Mountains (with some of the exhumed valleys now containing sediment cover remnants). In contrast the fundamentally different new paradigm requires immense south-oriented continental ice sheet melt water floods to have crossed the region as ice sheet related crustal warping raised the region and the Laramie Mountains (and implies sediments now partially filling some of the valleys are probably flood deposited mate-rials). The new paradigm provides simpler explanations for the origins of the valleys now extending completely across the northern Laramie Mountains and also for their related barbed tributaries, truncated side valleys, and drainage route U-turns than the accepted paradigm, although the new paradigm also leads to a fundamentally different middle and late Cenozoic regional geologic history than is currently recognized. One paradigm cannot be used to judge a different paradigm, but the paradigms can be compared based on their ability to explain evidence and Occam’s Razor can determine which of the two paradigms provides the simplest explanations. New paradigm expla-How nations for northern Laramie Mountains valley origins investigated here require fewer assumptions than the accepted paradigm explanations suggesting the new paradigm merits serious future consideration.

Detailed topographic maps show multiple stream valleys and what are probably dismembered stream valleys that extend completely across Wyoming's northern Laramie Mountains. Several of the most obvious valleys are described with valley origins first explained (or attempted to be explained) from the commonly accepted regional geomorphology paradigm (accepted paradigm) perspective and second from a recently proposed regional geomorphology paradigm (new paradigm) perspective in an effort to determine which of the two paradigms provides the simplest explanations. Accepted paradigm explanations require at least some of the valley erosion to have occurred prior to deposition of Oligocene and Miocene sediments that once covered the northern Laramie Mountains (with some of the exhumed valleys now containing sediment cover remnants). In contrast the fundamentally different new paradigm requires immense south-oriented continental ice sheet melt water floods to have crossed the region as ice sheet related crustal warping raised the region and the Laramie Mountains (and implies sediments now partially filling some of the valleys are probably flood deposited materials). The new paradigm provides simpler explanations for the origins of the valleys now extending completely across the northern Laramie Mountains and also for their related barbed tributaries, truncated side valleys, and drainage route U-turns than the accepted paradigm, although the new paradigm also leads to a fundamentally different middle and late Cenozoic regional geologic history than is currently recognized. One paradigm cannot be used to judge a different paradigm, but the paradigms can be compared based on their ability to explain evidence and Occam's Razor can determine which of the two paradigms provides the simplest explanations. New paradigm expla-1. Introduction

Statement of the Problem
A recently proposed regional geomorphology paradigm (new paradigm) requires massive south-and southeast-oriented continental ice sheet melt water floods to have flowed across what is today the entire Missouri River drainage basin including what are now high plateau and mountain range areas and is fundamentally different from the commonly accepted regional geomorphology paradigm (accepted paradigm) in which North American continental ice sheets existed at a time when a north-, northeast-, and east-oriented slope would have prevented continental ice sheet melt water floods from reaching most Missouri River drainage basin areas-including the entire state of Wyoming. According to Thomas Kuhn [1], paradigms are sets of rules governing how a scientific community conducts its research and by themselves are neither correct nor incorrect, but are judged on their ability to explain observed evidence. Kuhn suggests that from time to time evidence appears, which the accepted paradigm cannot satisfactorily explain. In such cases Kuhn says the anomalous evidence is dealt with in one of three ways. First, the accepted paradigm eventually explains the problem evidence and the accepted paradigm continues without interruption.
Second, the unexplainable evidence is put on the shelf for future consideration.
Third, the anomalous evidence leads to a new paradigm and a battle over which paradigm should be used.
When faced with the choice between two fundamentally different paradigms a scientific community can also apply Occam's Razor to determine which of two competing paradigms provides the simplest explanations. Occam's Razor in science, according to Anderson [2] suggests "What can be done with fewer [assumptions] is done in vain with more". Stream and dismembered stream valleys extending completely across Wyoming's northern Laramie Mountain represent known, but so far poorly explained evidence. Topographic maps depict the valleys and associated features such as barbed tributaries, drainage route U-turns, giving other sets of evidence a higher priority is unknown. However, these unusual valleys provide an opportunity to describe previously unexplained landform features, to attempt to explain the valley origins from the perspective of two fundamentally different regional geomorphology paradigms, and to apply Occam's Razor to determine which of the two competing paradigms requires the fewest number of assumptions. The principal drainage route seen in Figure 1 is the North Platte River, which originates in northcentral Colorado and flows in a northwest and north direction to the Laramie Range northwest end where the river has cut a 300-meter deep canyon and then turns in an east and southeast direction to flow along the Laramie Mountains northeast flank and into Nebraska where it joins the northeast-oriented South Platte River to form Nebraska's east-oriented Platte River (flowing to the Missouri River with the water ultimately reaching the Gulf of Mexico). In Figure   1

Previous Work
When comparing paradigms three types of previous work are important. First is paradigm neutral previous work describing, but not interpreting observed evidence. For determining how well a paradigm explains drainage system origins detailed topographic maps provide the most useful paradigm neutral previous work. The study reported here used topographic maps of the northern Laramie Mountains region available at the United States Geological Survey (USGS) National   [11] report "the timing and causes of the elevation gain and incision in the [Rocky Mountain] region are unclear" and Fan et al. [12] describe work supporting "a hypothesis that the steep elevation gradient between the central Rockies and the western Great Plains has existed as a major topographic feature since at least earliest Oligocene time with the mean elevation contrast comparable to the modern topography".
Also supporting such accepted paradigm interpretations are paleogeographic map reconstructions by Galloway et al. [13] showing Oligocene and Miocene east-oriented drainage systems to the east of the Laramie Mountains and the north-south continental divide a short distance to the north of the northern Laramie Mountains. From the accepted paradigm perspective, the north-south continental divide was located just to the north of the Laramie Mountains from about Eocene to Quaternary time when continental ice sheets blocked pre-glacial north-oriented rivers to form the present-day Missouri River. This pre-glacial north-oriented drainage system is known in the geologic literature as the Bell River drainage system (see [14]) and is supported by abandoned valleys extending northward from where north-oriented tributaries now join the Montana and North and South Dakota Missouri River. Glacial deposits partially fill those abandoned valleys and are used to support the pre-glacial age determination.
White [15] argued that continental ice sheets should have destroyed all evidence of any pre-glacial valleys especially in the easily-eroded northern plains region bedrock. However, numerous workers including Gravenor [16] and Sugden [17] rejected White's alternative deep erosion by continental ice sheets hypothesis and the accepted paradigm continues to interpret those abandoned valleys as pre-glacial in age.
In contrast the new paradigm's defining rule requires south-and south- In addition, from the new paradigm perspective Clausen [22] uses topographic maps evidence to show how large floods eroded an anastomosing complex of Laramie Range canyons (in the area to the south of Figure 1 southeast corner).

Research Method
This study was first done as part of the author's much larger Missouri River

Muddy Creek-Bates Creek through Valleys
Northeast

Deer Creek-Bates Creek and Deer Creek-Little Medicine Bow River Linkages
Deer Creek (seen in Figure 2 and Figure 3) and several tributaries begin as south-oriented streams that after leaving the mountains make U-turns and converge to flow in a north direction completely across the northern Laramie Mountains before turning in a northeast direction to reach the North Platte River. Upper Deer Creek Canyon (seen in Figure 3) is more than 500 meters deep and the Hunter et al. [3]

Box Elder Creek-Deer Creek and Box Elder Creek-Little Medicine Bow River Linkages
Box Elder Creek (seen in Figure 2 and

La Prele Creek-Little Medicine Bow River Linkages
La Prele Creek (headwaters seen in Figure 4)

La Bonte Creek-Little Medicine Bow River and La Bonte Creek-North Laramie River Linkages
La Bonte Creek (headwaters seen in Figure

Discussion
From the accepted paradigm perspective valleys now containing Oligocene and Miocene sediments were eroded prior to any North American continental ice sheets. In other words, from the accepted paradigm perspective the new paradigm explanations are impossible and should be rejected. However, Kuhn [1] states that one paradigm cannot be used to judge a fundamentally different pa- and a mechanism to explain why the Laramie Mountains uplift occurred as massive south-oriented floods flowed across the region. That mechanism could simply be a continental ice sheet that was thick and heavy enough to raise mountain ranges and plateau areas as gigantic melt water floods flowed from it.

Conclusion
Paradigms as described by Kuhn  This study compared the ability of a recently proposed regional geomorphology paradigm and of the commonly accepted regional geomorphology paradigm to explain easily observed (on detailed topographic maps) stream and other erosional valleys that now extend completely across Wyoming's northern Laramie Mountains. If just the erosional features are considered the new paradigm provides simpler and more complete explanations and the new paradigm should be preferred. However, if sediments contained in some of the eroded valleys are also considered the two paradigms lead to fundamentally different interpretations of middle and late Cenozoic geologic history and further work is needed to compare how the two competing paradigms explain other sets of easily observed geomorphic and geologic evidence.