Quad Creek Quartzite - 3.25 Billion years old. The lighter rock with darker central igneous intrusion is the oldest rock in the USA. It was derived from the first solid rock that formed on Earth. It is located in a roadcut of US Highway 212 South of Red Lodge.
Quad Creek Quartzite - 3.25 Billion Years Old. The first silica-rich, solid Earth crust that formed during the cooling of the earth surface was further compressed and heated during initial supercontinent formation and redistribution to become incorporated into other metamorphic rock that formed the Beartooth plateau.
Rock Creek Valley. The drive West from Red Lodge to Cooke City on Hwy 212 (Beartooth Highway) gives numerous views of this glacier-carved valley in metamorphic rock.
Beartooth Plateau at dawn. This plateau and associated Beartooth Pass at 10,947 ft (3,337 m) was forced upward during the Laramide orogeny (70-80 million years ago - 70-80 MA) initiated by tectonic plate subduction as what is now the western continent of North America was growing. Overlying layers were eroded by water, wind and, most notably, by glacier activity (1.5 MA) down to Precambrian rock. This plateau continues to rise as it is eroded due to the Yellowstone hot spot.
The beartooth was carved out of granitic gneiss by glacier activity.
Shedding mountain goats on the Beartooth Plateau. Mountain goats are not native and were introduced into the Absaroka and Madison Mountains in the 1940's and 1950's.
Lighter colored pegmatite, a quartz-rich igneous rock, sits on granitic gneiss a metamorphic rock which forms most of the Precambrian rock surface (>540 MA) at Beartooth Pass and Plateau.
Pilot Peak (center) and Index Peak (right) are glacier-carved peaks of volcanic strata from Absaroka Volcanic activity that occurred 53 to 43.7 MA. The Absaroka stratovolcanoes eroded and these peaks are eroded remains of Trout peak and Wapiti lava flows of andesite (lava of intermediate silica content). The off white to light green line below the base of the peaks is the Pilgrim formation of limestone and shale from the late Cambrian period (550 Ma).
Closer view of Pilot Peak in the center. Igneouw dikes that resist erosion form vertical bands in the mountain.
Layers of eroded andesitic deposits and brecca from the Absaroka Volcanic Supergroup are at the base of Pilot Peak.
Hurricane Mesa and other volcanic-origin mountains in the foreground in the Absaroka mountains lie above the lighter band of Pilgrim Formation limestone.
Beartooth Lake and Beartooth Butte. Residual sedimentary layers from the Paleozoic Era (Cambrian through Devonian, 550-350 MA) escaped glacier erosion and represent deposits laid down during periods of rising and fall seas in the Western Interior Seaway. There is a mixture of limestone, shale, sandstone and dolomite.
Detail of sedimentary layers in Beartooth Butte.
Republic Mountain above Cooke City, Montana with partially eroded Absaroka volcanic rock and conglomerate above Pilgrim limestone. Gold was discovered in Cooke City in 1870 while the area was still part of the Crow reservation. After relocating Crow to exploit mineral deposits of gold, silver, copper and lead, extensive mining occurred between the late 1800's and 1930.
Lulu pass above Cooke City. Igneous intrustion protrude through limestone formations. Acid fluids and magma interact with limestone which buffers the acid and metals are precipitated leaving deposits of gold, sliver, copper, lead and zinc at the interface.
Lulu Pass Contact Mine Ruins and machinery. The mine was active from 1910's through 1925. Pyritic gold ore removed from the volcanic mountain above was processed and shipped to Cooke City. Limestone and dolomite rocks are in the stream beds.
