Rivers of Big Mountain, 40K to 20K Years Ago.
Finally, one of the amazing ancient events around the end of the Pleistocene (40,000 – 20,000 y.a) that often fascinates me about Big Mountain topography. There was not a one mile thick ice sheet here, but in the far north was the Late Wisconsin Ice Sheet. Here, there was rapid erosional changes across Big Mountain’s ancestral landscape. Rivers cutting out canyons due to regional tectonic lifting aided by the well packed moisture of the Alpine-Mountain climate. A scene from 30,000 years ago is unimaginable to how the terrain looks today. Aside from the geologic processes, my fascination turns into that puzzling correlation to stories of prehistoric Díneh era or the origin time of Black Mesa topography. Walking up a gradual steep slope out from the ravine, there was the ocher stained and loose siltstone surface which is covered by dark-pink sand and river-worn clastic. These broken rock pieces were irregular, rounded pebbles. Larger chucks were recognizable pieces of solidified coal ash, baked shale, partially melted sandstones, jointed Moqui marble, and petrified wood. (fig. 5) My instant thoughts are the scenarios of a 30,000 year old river materials to the ancient, geologic scenario of a tropical environment 100 to 70 million years ago. I had no time to infringe upon the ground but certainly, river systems were responsible for these deposited remnants.
Inset: flash flood bend (A), rare major flood bench (B), Late Pleistocene bench (C),