Montana

Montana is where the corridor’s record thins out — subalpine limestone above Bozeman, a sixteen-crag gulch near Townsend, and country around White Sulphur Springs where even we found more scenery than route data. These pages are scaffolds more than chapters: honest about what’s documented, and an open invitation to whoever finishes the fieldwork.

The rock, at least, is now described. All three areas here are carbonate or carbonate-and-intrusive: the Bridgers are Mississippian Madison Group limestone carried up on a Laramide arch that exposes fourteen formations in one range; Avalanche Gulch is very probably the same Madison, karsted and pocketed, cut into the western flank of the Big Belts; and the Castles are an intrusive centre punched into a Paleozoic carbonate section — igneous spires west, limestone hills east, and an old lead–silver–copper district at the contact.