Geology of the Tincup Lake area, southwestern Yukon : implications for the tectonic evolution of the western margin of the Yukon-Tanana terrane

The lineup lake area (NTS 115G/1114) comprises 12 map units of polyfolded upper greenschist to lower amphibolite facies metasedimentary and metavolcanic rocks correlated with assemblages of Yukon-Tanana terrane. Mapping at a scale of 1: 20,000 was carried out, resulting in the identification of four generations of late Permian (?) to late Cretaceous folding and two generations of late Cretaceous, or younger, faulting in the lineup lake area. Well exposed Cal marble marker units constrain the orientation and geometry of map units in this structurally complex area. In the southern part of the lineup lake area the map pattern is controlled by F2 long limbs that are moderately to steeply S dipping. In the northern part of the lineup Lake area, Sdipping or gently NW-dipping F3 limbs control the map pattern. South-dipping, brittle normal faults crosscut folds and are in turn cut by a network of nearvertical, dextral strike-slip faults striking 305°-335° and with 500- 2000m spacing. The steep faults are inferred to be related to the Denali fault and were coeval with regional strike-slip faults that cut the Late Cretaceous to Early Paleocene Ruby Range Batholith to the south. South-dipping, brittle normal faults crosscut folds and are in turn cut by a network of nearvertical, dextral strike-slip faults striking 305°-335° and with 500- 2000m spacing. The steep faults are inferred to be related to the Denali fault and were coeval with regional strike-slip faults that cut the Late Cretaceous to Early Paleocene Ruby Range Batholith to the south.