How a Fundamentally Different and New Glacial History Paradigm Explains North America Glaciated Prairie Region Erosional Escarpments and Drainage Patterns

Scientific paradigms are frameworks of ideas governing how a discipline conducts its research. Paradigms by themselves are neither correct nor incorrect, but are judged on their ability to explain evidence and to open up research opportunities. The commonly accepted glacial history paradigm requires North American glaciated prairie region erosional landform features, such as erosional escarpments and abandoned valleys associated with the north-oriented Bell River drainage system, to be pre-glacial in origin. While considerable literature is based on such interpretations those escarpments and abandoned valleys are formed in easily eroded bedrock and should not have survived continental ice sheet erosion. In addition to defying common sense logic the pre-glacial origin of those erosional escarpments and abandoned valleys is not well understood. A new paradigm requiring at least one continental ice sheet to have occupied a deep North American “hole” (formed by deep ice sheet erosion and ice sheet caused crustal warping) offers geomorphologists an opportunity to explain the erosional escarpments as remnants of canyon walls originally formed when supra-glacial rivers sliced ice-walled and bedrock-floored canyons into a decaying continental ice sheet’s surface and the abandoned north-oriented Bell River drainage system valleys to have been eroded as the ice-walled and bedrock-floored canyon network captured and diverted massive melt water floods onto and then across the decaying ice sheet’s floor and then in northeast and north directions between detached and semi-detached ice sheet remnants. The diversion of immense melt water floods from the Gulf of Mexico to the North Atlantic Ocean triggered climatic change that ended the first ice sheet’s melting. Water in the newly formed north-oriented drainage systems then froze between the detached and semi-detached (and greatly thinned) ice sheet remnants to create a second and much thinner ice sheet and to complete creation of the glaciated prairie region glacial features seen today.

GIS analyses of ice-sheet erosional impacts on the exposed shield of Baffin Island, eastern Canadian Arctic

The erosional impacts of former ice sheets on the low-relief bedrock surfaces of Northern Hemisphere shields are not well understood. This paper assesses the variable impacts of glacial erosion on a portion of Baffin Island, eastern Canadian Arctic, between 68° and 72°N and 66° and 80°W. This tilted shield block was covered repeatedly by the Laurentide Ice Sheet during the late Cenozoic. The impact of ice-sheet erosion is examined with GIS analyses using two geomorphic parameters: lake density and terrain ruggedness. The resulting patterns generally conform to published data from other remote sensing studies, geological observations, cosmogenic exposure ages, and the distribution of the chemical index of alteration for tills. Lake density and terrain ruggedness are thereby demonstrated to be useful quantitative indicators of variable ice-sheet erosional impacts across Baffin Island. Ice-sheet erosion was most effective in the lower western parts of the lowlands, in a west–east-oriented band at around 350–400 m a.s.l., and in fjord-onset zones in the uplifted eastern region. Above the 350–400 m a.s.l. band and between the fjord-onset zones, ice-sheet erosion was not sufficient to create extensive ice-roughened or streamlined bedrock surfaces. The exception — where lake density and terrain ruggedness indicate that ice-sheet erosion had a scouring effect all across the study area — was in an area from Foxe Basin to Home Bay with elevations <400 m a.s.l. These morphological contrasts link to former ice-sheet basal thermal regimes during the Pleistocene. The zone of low glacial erosion surrounding the cold-based Barnes Ice Cap probably represents the ice cap’s greater extent during successive Pleistocene cold stages. Inter-fjord plateaus with few ice-sheet bedforms remained cold-based throughout multiple Pleistocene glaciations. In contrast, zones of high lake density and high terrain ruggedness are a result of the repeated development of fast-flowing, erosive ice in warm-based zones beneath the Laurentide Ice Sheet. These zones are linked to greater ice thickness over western lowland Baffin Island. However, adjacent lowland surfaces with similar elevations of non-eroded, weakly eroded, and ice-scoured shield bedrock indicate that—even in areas of high lake density and terrain ruggedness—the total depth of ice sheet erosion did not exceed 50 m.