Geo-challenge: Hiking on (not In) a River Valley

Posted on the 11 December 2015 by Hollis

Where on Google Earth are we?

Some hints ...
Arrows point to stream deposits from roughly 20 million years ago. Obsolete names date from the late 1800s.
Stream deposits cap a ridge (inverted topography); Devils Smoke House and Gabriels Castle behind. Note spectacular unconformity.The trail on the ridge crest passes through stream deposits turned to rock and photogenically eroded. 

Layers of sand, pebbles, cobbles record changes from about 20 million years ago.

Cemented layer, above siltstone nodules in fine matrix, above unconformity; cross-bedding near top of photo. 

Mostly siltstone nodules.

Crystalline clasts from the Rocky Mountains.


I found many puzzling weathered forms in cemented sand. Here are a few:

Happy dog for scale.

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