6 Surficial geology and neotectonics in the West: Celebrating and advancing the legacy of Kirk Bryan through field-based geomorphology studies (Posters)
This session invites and examines recent field-based geomorphology studies in the West. Contributions regarding soils geomorphology, neotectonics, pediments, fluvial terraces, and landscape development are invited.
Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E
Tracking North America's pre-Pleistocene Amazon-scale paleo-river from its possible headwaters in the Colorado Plateau and Great Basin to its delta in the Labrador Sea
Paper number: 6-0
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM
Authors
Abstract
Prior to its stepwise destruction by tectonics, volcanism, and glaciation, an Amazon-scale, pre-Pleistocene paleo-river drained North America into a large delta in the Labrador Sea. At its height, its southern headwaters may have tapped the Colorado Plateau and Great Basin. It was named the "Bell River" after the Canadian geologist who first imagined it in 1895. Seismic reflection profiles and deep exploration wells have documented the internal stratigraphy of the 9-km thick Bell River paleo-delta in the Labrador Sea. The continental-scale Bell River arrived in the Labrador Sea as the Cretaceous Interior Seaway was retreating. Detrital zircon of delta sediments have apparent provenance in the Canadian Shield, Rocky Mountains, Colorado Plateau, and Great Basin. Numerous sites preserve geologic evidence of the tenure and destruction of north-flowing Miocene paleo-rivers from the Rocky Mountains, Colorado Plateau, and Great Basin. Paleocene and Eocene delta sediments were dominated by muds eroded from Cretaceous marine beds of the Cordilleran foreland basin. Oligocene and Miocene sand sheets of the delta front include detrital zircon with apparent provenance in the Cordilleran magmatic arc of southern California and Arizona.
The southern headwaters of the Bell River were the paleo- upper Missouri and Yellowstone Rivers, which confluenced with the Bell River in the area of Hudson Bay. The paleo-Yellowstone may have tapped into the southern Colorado Plateau. It may have eroded part of the early Grand Canyon and scoured the Colorado Plateau from 28 Ma to 6 Ma. Its headwaters were cut off by faulting along the present Continental Divide in west-central Wyoming, when tectonics shifted drainage from north- to south-flowing. After 6 Ma, the deep Inner Gorge of Grand Canyon was carved by the south-flowing Colorado River. The paleo-upper Missouri River may have reached into the Great Basin from 16 Ma to 6 Ma, but was cut off at the Continental Divide on the Idaho-Montana border by faulting along the Yellowstone hotspot track. Pleistocene ice sheets destroyed the Bell River basin in Canada, scoured its delta, and diverted the Missouri and Yellowstone rivers into the Mississippi River basin.
Geological Society of America Abstracts with Programs. Vol. 58, No. 4
doi: 10.1130/abs/2026RM-410514
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