Question: The Cheakamus Valley basalts are part of what southwestern British Columbia formation?
Context: The British Columbia Electric Railway (BCER) was an historic railway which operated in southwestern British Columbia, Canada.  Originally the parent company, and later a division, of BC Electric, the BCER assumed control of existing streetcar and interurban lines in southwestern British Columbia in 1897, and operated the electric railway systems in the region until the last interurban service was discontinued in 1958.  During and after the streetcar era, BC Electric also ran bus and trolleybus systems in Greater Vancouver and bus service in Greater Victoria; these systems subsequently became part of BC Transit, and the routes in Greater Vancouver eventually came under the control of TransLink.  Trolley buses still run in the City of Vancouver and one line extends into Burnaby. Flute Summit is a flat-topped summit in the Fitzsimmons Range of the Garibaldi Ranges of the Pacific Ranges in southwestern British Columbia, Canada.  It is located on the north side of Cheakamus Lake just southeast of the town of Whistler in Garibaldi Provincial Park.  The mountain is part of a group of hills called the Musical Bumps. The Cheakamus Valley basalts are a sequence of basaltic lava flows along the Cheakamus River in southwestern British Columbia, Canada.  They are part of the Garibaldi section of the Cascade Volcanic Arc and were produced during an episode of volcanic eruptions from an unknown vent.  The latest basaltic eruption deposited wood in lacustrine sediments under the lava flows that have been dated 34,200 ± 800 years old.  These youngest lavas form isolated ridges above the older glaciated Cheakamus Valley basalts and were described as "esker-like" by Canadian volcanologist Bill Mathews. The Squamish people (or in the "Squamish language (Sḵwx̱wú7mesh snichim)" Skwxwú7mesh   , sometimes seen in English as Skwxwu7mesh (The "7" represents a glottal stop), historically transliterated as Sko-ko-mish) are an indigenous people in southwestern British Columbia, Canada.  In 2012, there was population of 3,893 band members registered with the Squamish Nation.  Their language is the Squamish language or "Sḵwx̱wú7mesh snichim", considered a part of the Coast Salish languages, and is categorized as nearly extinct with just 10 fluent speakers as of 2010.  The traditional territory covered Point Grey as the southern border.  From here, it continued northward to Roberts Creek on the Sunshine Coast, up the Howe Sound.  The northern part included the Squamish, Cheakamus, Elaho and Mamquam rivers.  Up the Cheakamus River it included land past Whistler, British Columbia.  The southern and eastern part of their territory includes Indian Arm, along Burrard Inlet, through False Creek then English Bay and Point Grey.  Today the Squamish people live mostly in seven communities, located in West Vancouver, North Vancouver, and within and nearby to the District of Squamish. The Fitzsimmons Range is a small mountain range on the northwestern edge of the Garibaldi Ranges in southwestern British Columbia, Canada, located between the valleys of Cheakamus Lake (SW) and Fitzsimmons Creek (NE).  Its most famous summit is Whistler Mountain, which overlooks the resort town of Whistler and is one of the two mountains forming the Whistler Blackcomb ski resort.  Most of the range is within Garibaldi Provincial Park, while its northeastern extremity is part of the resort municipality, and of the lands associated with the ski resort operation.  Other summits in the range include Oboe Summit, Piccolo Summit and Flute Summit, which are hillocks along the ridge running southeast from Whistler Mountain and were named in association with the renaming of Whistler.  Beyond them is Singing Pass and Mount Fitzsimmons 2603 m (8540 ft) which is at the opposite end of the range from Whistler Mountain and the location of Fitzsimmons Glacier, which is the source of Fitzsimmons Creek. Mount Price is a small stratovolcano in the Garibaldi Ranges of the Pacific Ranges in southwestern British Columbia, Canada.  It is located 10 km southeast of the abandoned settlement of Garibaldi above the eastern flank of the Cheakamus River valley.  With a summit elevation of 2052 m and a topographic prominence of 402 m , it rises above the surrounding landscape on the western shore of Garibaldi Lake.  A large provincial park surrounds Mount Price and other volcanoes in its vicinity. The McBride Range is a small mountain range in southwestern British Columbia, Canada, located east of Cheakamus Lake at the northeast side of Garibaldi Provincial Park.  It has an area of 228 km and is a subrange of the Garibaldi Ranges which in turn form part of the Pacific Ranges of the Coast Mountains. The Cascade Volcanoes (also known as the Cascade Volcanic Arc or the Cascade Arc) are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 mi .  The arc has formed due to subduction along the Cascadia subduction zone.  Although taking its name from the Cascade Range, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes extend north into the Coast Mountains, past the Fraser River which is the northward limit of the Cascade Range proper. The Karmutsen Formation is a Late Triassic volcanic sequence of tholeiitic pillow basalts and breccias on Vancouver Island, British Columbia, Canada.  It is perhaps the thickest accreted section of an oceanic plateau worldwide, exposing up to 6000 m of basal sediment-sill complexes, basaltic to picritic pillow lavas, pillow breccia, and thick, massive basalt flows.  The widespread succession of basalts and breccias are part of the Insular Mountains, a large volcanic mountain range that forms Vancouver Island and the Queen Charlotte Islands.  In Strathcona Provincial Park, pillow basalts is the most abundant rock unit.  About half the mountains, including the highest ones, are carved from these basalts, such as Golden Hinde, which is the highest peak on Vancouver Island. The Whistler Olympic and Paralympic Village was a 2010 Winter Olympics facility in the resort town of Whistler, British Columbia.  The Olympic Village is considered one of Whistler's legacy projects, in that it is being used after the Olympics to help house and train Canadian athletes.  Whistler is one of the two host communities for the Games.  The site of this athletes' village is in the Cheakamus Valley approximately 20 minutes south of the Whistler Mountain competition venues, and 6 km from the highway cutoff for the Whistler Olympic Park sliding events venue in the Callaghan Valley.
Answer: Cascade Volcanoes