How a New Paradigm Explains Topographic Map Drainage System and Erosional Landform Evidence in the Fremont County Royal Gorge Area, Colorado, USA

A new Cenozoic geologic and glacial history paradigm (new paradigm) describes massive and prolonged continental ice sheet meltwater floods that eroded the Colorado Royal Gorge area and surrounding regions and which were diverted in east, northeast, and even north directions as uplift of a thick ice sheet created deep “hole” rim gradually occurred (the thick ice sheet was located where North American ice sheets are usually recognized to have existed). A deep “hole” rim segment followed what is now the northern and central Colorado east-west continental divide southward to the Arkansas River headwaters area and then continued south along the Sangre de Cristo Mountains crestline to at least the Purgatoire River-Canadian River drainage divide and may have continued east from that point along a less well-defined zone beginning with what is now the Purgatoire River-Canadian River drainage divide. Diverging and converging valley complexes, barbed tributaries, and Arkansas River and other drainage route direction changes (easily seen on United States Geological Survey detailed topographic maps) are interpreted to have developed as the south-oriented floodwaters first flowed across the rising deep “hole” rim to reach the south- and southeast-oriented Rio Grande River drainage basin and were subsequently blocked by deep “hole” rim uplift and diverted to flow in east, northeast, and north directions. The accepted Cenozoic geologic and glacial history paradigm (accepted paradigm) has to date been unable to satisfactorily explain the detailed topographic map drainage system and erosional landform evidence and the new and accepted paradigms are incommensurable and lead to quite different Cenozoic geologic and glacial histories.

Holocene glacier history of northeastern Cordillera Darwin, southernmost South America (55°S)

In the Cordillera Darwin, southernmost South America, we used 10Be and 14C dating, dendrochronology, and historical observations to reconstruct the glacial history of the Dalla Vedova valley from deglacial time to the present. After deglacial recession into northeastern Darwin and Dalla Vedova, by ~16 ka, evidence indicates a glacial advance at ~13 ka coeval with the Antarctic Cold Reversal. The next robustly dated glacial expansion occurred at 870 ± 60 calendar yr ago (approximately AD 1150), followed by less-extensive dendrochronologically constrained advances from shortly before AD 1836 to the mid-twentieth century. Our record is consistent with most studies within the Cordillera Darwin that show that the Holocene glacial maximum occurred during the last millennium. This pattern contrasts with the extensive early- and mid-Holocene glacier expansions farther north in Patagonia; furthermore, an advance at 870 ± 60 yr ago may suggest out-of-phase glacial advances occurred within the Cordillera Darwin relative to Patagonia. We speculate that a southward shift of westerlies and associated climate regimes toward the southernmost tip of the continent, about 900–800 yr ago, provides a mechanism by which some glaciers advanced in the Cordillera Darwin during what is generally considered a warm and dry period to the north in Patagonia.

How Two Different Cenozoic Geologic and Glacial History Paradigms Explain the Southcentral Montana Musselshell-Yellowstone River Drainage Divide Origin, USA

The accepted Cenozoic geologic and glacial history paradigm (accepted paradigm) considers the southcentral Montana Musselshell-Yellowstone River drainage divide to have originated during Tertiary (or preglacial) time while a new and different Cenozoic geologic and glacial history paradigm (new paradigm) describes how headward erosion of a northeast-oriented Musselshell River valley segment captured huge southeast-oriented meltwater floods to create the drainage divide late during a continental ice sheet’s melt history. Northwest to southeast oriented divide crossings (low points observed on detailed topographic maps where water once flowed across the drainage divide), southeast-oriented Yellowstone and Musselshell River segments immediately upstream from northeast-oriented Yellowstone and Musselshell River segments, and southeast- and northwest-oriented tributaries to northeast-oriented Yellowstone and Musselshell River segments indicate a major southeast-oriented drainage system predated the northeast-oriented Yellowstone and Musselshell River segments. Closeness of the divide crossings, divide crossing floor elevations, large escarpment-surrounded erosional amphitheater-shaped basins, and unusual flat-floored internally drained basin areas (straddling the drainage divide), all suggest the previous southeast-oriented drainage system moved large quantities of water which deeply eroded the region. In the mid-20th century geomorphologists working from the accepted paradigm perspective determined trying to explain such erosional landform evidence from the accepted paradigm perspective was a nonproductive research activity and now rarely investigate erosional landform origins. On the other hand, the new paradigm appears to explain most, if not all observed erosional landform features, although the two paradigms lead to significantly different regional Cenozoic geologic and glacial histories that cannot be easily compared.