The lake-drainage site is in Sanders County, Montana, approximately 65 mi (105 km) northwest of Missoula, and about the same distance southwest of Kalispell (Fig. 1).
Paved, two-lane highways and easily passable side roads provide interconnecting access to most parts of the area at all seasons. Montana 382 between Perma and its junction with Montana 28 passes through Markle Pass and across the giant ripples of Camas Prairie. An unpaved track leads from that road to Wills Creek Pass and the Schmitz Lakes. Montana 28 between Plains and Hot Springs crosses the debris fill in the valley of Boyer Creek, and passes Rainbow Lake and through Duck Pond Pass above its head. An unpaved county road connects Rainbow Lake and Camas Prairie.
Ownership is a mixture of private ranch land, public and private forest land, and Flathead-Salish tribal lands, none of which are posted. Access is generally open to all parts of the area except that people planning to spend significant amounts of time on the tribal lands around Rainbow Lake should buy a recreation permit.
The varve site comprises large roadcuts through stream and glacial lake deposits on and near 1-90 in the vicinity of the Nine-mile Exit, about 19 mi (31 km) west of Missoula, in Missoula County (Fig. 1).
Figures & Tables
Rocky Mountain Section of the Geological Society of America
One of six volumes generated by each GSA section for the Decade of North American Geology (DNAG) project, this Centennial Field Guide contains descriptions of 100 sites or site clusters representing outstanding geologic locations in northern Arizona, Colorado, Idaho, Montana, North Dakota, New Mexico, South Dakota, Utah, Wyoming, and Alberta.