The Marble Mountain Wilderness lies within the Klamath Mountains west of Fort Jones, California.  This particular section b/w Black Marble Mountain & Marble Mountain contains a vast region of marble karst, w/ many channels & sinks of sculpted rock in solution leading down to vertical pits & cave entrances.  There are at least 150 known cave entrances within the karst, the largest is Bigfoot Cave w/ about 12.4 miles of known passages & a depth of 1,205 feet, which is more than Oregon Caves to the north.  The slope here is steep but the marble has a strong grip, flatter plateaus nearby is where I spotted many cave entrances, pits up to 100 feet deep.  The geology of the Klamath Mountains is among the most bizarre & intriguing in North America, nearby atop the marble & w/in are schist deposits & the adjacent higher peaks w/in the Boulder Peak region is comprised of red peridotite.  To the south, one can see the snowy Trinity Alps, of Sierra Batholith origin.