Presentation Type

Poster

Abstract

Examination of the early Cenozoic fluvial deposits of the Renova Formation provides support for the hypothesis that a southern branch of the pre-ice age Bell River of Canada, a river thought to have been the size of the Amazon, may have originated in the southern Colorado Plateau and flowed northward through Nevada, Utah, Idaho, and Montana. The Renova Formation mostly comprises fluvially-reworked and degraded volcanic ash. Radiometric ages of zircon grains from the Renova Formation, reported in the literature, correlate with the ages of zircons from ash-flow tuffs that erupted from mega-calderas in southern Nevada and Utah. There are also older zircons present in the Renova deposits which indicate recycling of zircon grains from Precambrian and Cambrian quartzites of Utah. These results provide evidence of river transport of ash and sand from Nevada and Utah into Montana. Previous research has been reviewed and assessed in the context of the Bell River hypothesis. A field trip was taken to physically observe the composition and depositional features of the Renova. Histograms generated by mass spectroscopy of Renova Formation zircon have been re-analyzed in light of the mega-caldera origin hypothesis. This new model suggests that a major, north-flowing Cenozoic drainage system was present in the western interior of North America before being segmented and destroyed by faulting and volcanism.

Category

Physical Sciences

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Apr 11th, 3:00 PM Apr 11th, 4:00 PM

Early Cenozoic Fluvial Deposits of the Renova Formation in SW Montana: Links to Southern Nevada and Utah?

Examination of the early Cenozoic fluvial deposits of the Renova Formation provides support for the hypothesis that a southern branch of the pre-ice age Bell River of Canada, a river thought to have been the size of the Amazon, may have originated in the southern Colorado Plateau and flowed northward through Nevada, Utah, Idaho, and Montana. The Renova Formation mostly comprises fluvially-reworked and degraded volcanic ash. Radiometric ages of zircon grains from the Renova Formation, reported in the literature, correlate with the ages of zircons from ash-flow tuffs that erupted from mega-calderas in southern Nevada and Utah. There are also older zircons present in the Renova deposits which indicate recycling of zircon grains from Precambrian and Cambrian quartzites of Utah. These results provide evidence of river transport of ash and sand from Nevada and Utah into Montana. Previous research has been reviewed and assessed in the context of the Bell River hypothesis. A field trip was taken to physically observe the composition and depositional features of the Renova. Histograms generated by mass spectroscopy of Renova Formation zircon have been re-analyzed in light of the mega-caldera origin hypothesis. This new model suggests that a major, north-flowing Cenozoic drainage system was present in the western interior of North America before being segmented and destroyed by faulting and volcanism.