Bedrock Geology, Morris Lake (105B/5), southern Yukon (1:50,000 scale)

Between the Cretaceous granites (Hake Batholith on the west; Cassiar Batholith to the east) are three belts of metamorphic rocks, collectively part of Yukon-Tanana Terrane (Mortensen, 1992). These are remnants of oceanic and continental volcanic arcs, and marginal basin sediments of Early to mid-Paleozoic age. At the head of Borden Creek are thick carbonate and andesitic volcanic rocks correlated with Klinkit Group (Simard et al., 2003). The Ram Creek Fault (Poole, 1956) and Hidden Lake Fault are not exposed but deduced to be steeply dipping brittle structures with northeastward thrust or transpressional offset, based upon more complete exposure to the southeast in 105B/3 map area. The former is likely of Cretaceous age; the latter was active between mid-Permian and Early Jurassic time.