Thursday, June 19, 2014

The Purple Cilffs of the McDermott Formation

South of Durango lies this striking maroon cliff band of strata known locally as the Purple Cliffs and geologically as the McDermott Formation. It is believed by most geologist to be a fluvial deposit with debris flows and some volcaniclastic deposits from the La Plata Volcanic Intrusions to the northwest.. The deposit can be found throughout the Four Corners area and is dated to be on the Upper Cretaceous-Tertiary boundary (66 Million years old) and some fossils have been found in the formation here in Durango and also in exposures in New Mexico. I find them to be one of my favorite exposures in all of the Durango area.


  1. Looks like a nice place for a hike.

  2. Try looking at these Purple Cliffs as the TIP OF THE SAN JUAN BASIN more intimately known as the Fruitland Coal Outcrop. The Fruitland Coal which has been drilled extensively for coal-bed methane NatGas actually comes up from the depths (2,600 ft deep around Ignacio) and outcrops on the surface here. Go to Google Maps, choose the satellite view and you can visualize this entire Fruitland Coal Outcrop coming up from the coal strip mine fields in northern New Mexico to this Purple Cliffs feature where it crosses over the river behind WalMart and becomes Carbon Junction at the Ford Dealership, then becomes Raider Ridge behind FLC and goes out towards Helen's Store then into the Pine River Drainage where it expands out and heads south of Pagosa Springs. This is the outcrop RIM of the Fruitland Coal defining the San Juan Basin of hydrocarbon elements, primarily NatGas (coal-bed methane) and strip mined coal.

    Originally, the base case for building an uphill Lake now fenced off and named Lake Changehorse was to get Animas River Water pumped 500 ft uphill as the first beginning of a storage mechanism to futher pump this water uphill toward Marvel and Kline where the new coal fired plants were planned to be built.

    Don't be deceived about what these Purple Cliffs actually represent.

    Alice Weatherby