TOWER AND RAM: A TALE OF TWO ANTICLINES

The Canyon Ranges of the Mackenzie Mountains, MWT, Canada, extend between Lats. 61-68 N as a series of anticlinal and periclinal folds in carbonate and clastic strata of Ordovician-Pennsylvanian age. The structures display many evidences of Neotectonic activity. Best known are three deep canyons along the South Nahanni River that are of antecedent origin. Immediately to the north, the Ram River (Lat. 61 30'N, Long 124 - 124 45'W)rises on Tower Anticline and follows an antecedent course east across Ram Plateau, a second anticline. geomorphic evolution of both structures is controlled by the Nahanni Fm, a resistant platformal limestone ~180 m in thickness that is overlain by readily stripped shales.The formation is karstic, with well- developed karstic groundwater circulation despite presence of widespread to continuous permafrost. On Tower Anticline it is underlain by shales and thin-bedded argillaceous limestones of low solubility and permeability, and has been gutted by basal sapping of the caprock as a consequence. On Ram Plateau it is underlain by banded dolomites that permit karstic groundwater circulation so that the karstic plateau is largely preserved. Correlations with canyon sinuosity, local relief and inferred neotectonic history will be discussed.