The “lower or bowlder member” of the formation exposed on Miller Mesa, Colorado, and designated by Atwood in 1915 as Eocene Ridgway Till is Pleistocene till, overlain by remnants of an extensive Pleistocene landslide consisting largely of huge slabs of San Juan tuff-agglomerate. The “upper or pebble member” of Atwood's Ridgway Till is crushed Mancos Shale with contained pebbles from the Telluride Conglomerate and was a part of that landslide.

The “Gunnison tillite” of Atwood and Atwood (1926) is not a glacial deposit but is part of a volcanic agglomerate.

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