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-7- I I I I I I I I I I I I I I I I I I I The Minturn Formation is well exposed in the vicinity of Red Sandstone Creek and is the oldest sedimentary rock in the area.16 It is composed of medium to very coarse-grained, gray to reddish brown sandstone, conglomeratic sandstone, thin beds of reddish brown silt- stone and sandy silty shale and pinkish gray to gray limestone beds. Basin Formation and Character Gore Creek has eroded deeply into the Minturn Formation by a combination of glaciation and alluvial action. The basic valley shape through much of the main Gore Valley is the classic U-shape typical of glacier action. This glacial erosion occurred mainly during the late Pleistocene period and the valley floor near the Town of Vail at some time in the past has been much deeper. The alluvial deposits within the valley currently exceed 100 feet in depth and are interfingered with coarser side tributary talus and slope wash deposits. Layers of peat or high organic content layers are found at infrequent levels throughout the alluvium. The upper end of most of the side tributaries, such as Booth, Pitkin on the north side of the basin and numerous smaller tributaries on the south side of the basin are formed in bowl shaped depressions that were created by "hanging" glaciers or nivation hollows during the Pleistocene period. The lower levels of the bowls are founded on erosion resistant or harder sandstone or limestone members of the Minturn Formation. The sections of the side tributaries that pass through these more resistant members is typified by very steep gradients and series of cliffs. Ther.e are various locations through the valley where large mass wasting or rock-soil slides have occurred. Many of these are associated