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GeoSnaps - Image of the Day

Geologic snapshots capturing Arizona’s geologic setting and mining history with a picture of the day from 1 January through 31 December 2013.

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Thursday, December 26, 2013
sandstone, siltstone

October 23, 2008 | Tuba City Kayenta-Navajo Transition | Northern Arizona  - Ranney

Much detail can be seen in these outcrops located north of US Highway 161 near Tuba City, Arizona. The salmon-colored, thinly-bedded deposits are fluvial mud and fine-grained sand within the Kayenta Formation of Jurassic age. These sediments were derived in streams originating to the northeast in the Ancestral Rocky Mountains. Upon this fluvial floodplain, small dunes would occasionally migrate across the landscape and two such dune sets are preserved as the orange-colored wedges of cross-bedded sandstone. These sands presage the arrival of the Navajo erg (sand sea) preserved today as the Navajo Sandstone on the Colorado Plateau. One can almost imagine this arid floodplain, with dinosaurs stalking the river banks. (Contributed by Wayne Ranney).

randomness-azgeology