Approximately 6 miles south of Chemult, at Diamond Lake Station (formerly Lonroth) on the Southern Pacific Railroad, the pumice is 65 feet thick and rests on at least 96 feet of stratified sand, gravel, and clay. Near by, in the hamlet of Beaver Marsh, a well penetrated 73 feet of pumice without reaching bottom. At Yamsay Station, approximately 5 miles farther south on the Southern Pacific tracks, the pumice is 53 feet thick. A mile or so northwest of this station, at the junction of the Dalles-California highway with the Diamond Lake highway, the pumice is reported to be 114 feet thick and to rest on “black sand.”
At Lenz Station, 9 miles south of Yamsay, the pumice is 65 feet thick and rests on sand and gravel. At Fuego, approximately another 9 miles to the south, two wells were drilled, one 500 feet and the other 136 feet west of the station. The former penetrated pumice to a depth of 70 feet without reaching the underlying bedrock; the other passed out of pumice and entered sand at a depth of 55 feet.
At Kirk Station, close to the south margin of the avalanche deposit, the pumice is 47 feet thick and rests on so-called “chalk rock,” probably Pliocene diatomite.
There are few available records of wells drilled through the pumice flow east of the Southern Pacific Railroad. On the Fordyce or Ryan Ranch, a short distance south of Lenz Station, three wells penetrated the deposits and entered coarse sand at depths between 18 and 30 feet. Farther east, near the Old Military Crossing, on the edge of Klamath Marsh, the pumice flow is 66 feet thick and is underlain by massive basalt. According to George Hartley, wells sunk near the center of Klamath Marsh pass through layers of pumice interstratified with sediments even to a depth of 350 feet. Doubtless these thin pumice layers represent products of much earlier eruptions.
In order to determine the thickness of the pumice and scoria flows closer to the base of Mount Mazama, three wells were drilled west of the Dalles-California highway. The first was 1 mile south of the northwest corner of the Klamath Indian Reservation, at an elevation of 4700 feet. Down to a depth of 80 feet the well passed through smoke-gray pumice and scoria, rich in crystals and small lithic fragments. Approximately 10 feet from the surface, the ejecta were stained bright pink by fumarolic action. From 80 to 93 feet, the well penetrated white lump pumice; from 93 to 96 feet, it traversed water-worn volcanic sand and gravel.
A second well, 5 miles to the south, passed through the following layers: 0-5 feet, crystal-lithic ash with fine pumice; 5-20 feet, pink dacite pumice; 20-80 feet, pumice mixed with smoke-gray scoria and crystal ash; 86-121 feet, coarse white dacite lump pumice; 121-125 feet, pumice-free volcanic sand and gravel.
