ABSTRACT
Three glacial drifts of Pleistocene age can be differentiated in a transect across the Strait of Magellan from the slopes of Brunswick Peninsula on the mainland to the crest of the Boqueròn Range on Tierra del Fuego. The youngest drift displays sharp constructional morphology, is weathered to depths of less than a meter, and contains volcanic clasts with weathering rinds <1 mm thick. An intermediate drift has more subdued morainal topography and is weathered to depths of 2.5-3 m; weathering rinds reach mean thicknesses of 2.1-2.2 mm. The oldest drift extends to the highest terrain on the transect and retains little or no constructional morphology; weathering extends to >3 m and weathering rinds reach thicknesses of 5 mm. Traced northward, the two youngest drifts are correlated with moraine systems that reach the strait at the Second Narrows and First Narrows, respectively. Limiting radiometric ages, together with the relative-age data, indicate that the youngest drift correlates with the last glacial age (isotope stage 2), that the intermediate drift is of middle Pleistocene age, and that the oldest drift may date to the early Pleistocene. Each of the two older drifts may include deposits of more than one glaciation.
