How a New Geology and Glacial Paradigm Explains Colorado South Platte-Arkansas River Drainage Divide Topographic Map Evidence, USA

Abstract

United States Geological Survey (USGS) topographic maps (available at the USGS National Map website) are used to determine development of the asymmetric South Platte River drainage basin (south of Denver) by noting low points (referred to as divide crossings) where south-oriented floodwater channels once crossed the South Platte-Arkansas River drainage divide. Twelve groups of observed divide crossings are described most of which show evidence for flood-formed diverging and converging channels including where divide crossings are cut across Thirtynine Mile volcanic field ejectamenta. A new Cenozoic geologic and glacial history paradigm requires southeast- and south-oriented floods to have flowed across what is now the east-west continental divide to reach the southeast-oriented Arkansas River valley and to have eroded the divide crossings before north-oriented South Platte River valley headward erosion captured the flow. Such floods are not consistent with accepted Cenozoic geologic and glacial history interpretations, but are consistent with new paradigm interpretations (developed to explain Missouri River drainage basin topographic map drainage system evidence) in which a thick continental ice sheet (located where large continental ice sheets are usually reported to have been) deeply eroded the underlying bedrock and caused crustal uplift to create a deep “hole” with a deep “hole” rim segment roughly following today’s Wyoming and northern Colorado east-west continental divide and then continuing eastward along what is now the Mis-souri-Arkansas River drainage divide. The new paradigm results in a Cenozoic geologic and glacial history in which immense south-oriented continental ice sheet meltwater floods first flowed in a south direction across the rising deep “hole” rim and were then forced by rim uplift to flow along the rim subsequently in north directions into the developing deep “hole”.