The Elk Mountains and West Elk Mountains appear to be westward
continuations of the Sawatch Range. Structurally, however, they are not
faulted anticlines like most of the other ranges in Colorado, but are
composed of a series of layers of Paleozoic sediments thrust westward
over one another. These rocks, often crumpled and highly metamorphosed,
are cut by numerous sills, dikes, and other intrusions, many of which
have caused mineral enrichment locally.
At Maroon Bells, in the canyon of Maroon Creek, and at Redstone on the
Crystal River, these metamorphosed sediments are well exposed. Here, red
sandstones and shales have been altered to quartzites and slate. At
Marble, metamorphism of a thick limestone bed has produced white marble
of great beauty, known as Yule Marble. This decorative stone was
quarried extensively until about 1940. It was used in the Lincoln
Memorial and several other monumental structures; in the town of Marble
it has been used for the doorsteps of log cabins! The largest block
quarried, for the Tomb of the Unknown Soldier in Arlington National
Cemetery, measured 14 by 7.4 by 6 feet in the rough, and weighed 56
tons.
[Illustration: Mt. Sopris, south of Glenwood Springs, is an igneous
intrusion. (Jack Rathbone photo)]
Crested Butte, at the south end of the Elk Mountains, is a small
intrusive igneous mass called a _laccolith_. Hard and resistant to
erosion, it stands over 2,000 feet above the adjacent valley floor.