Entrada sandstone - 140 -180 million years. Here’s the USGS page discussing it: http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/entrada.htm
When you get done reading the literature sited get back to me.
cited, not sited...
This is just what I said, that the figure of ~200 million years came from the age of the deposited strata. And I repeat that it seems specious to say that nature took this amount of time to form the rock that these yahoos toppled. Why not call it 10 billion years in the making, as we may say of anything we come upon at any time?