An improved estimate of lithospheric thickness based on a reinterpretation of tilt data from Pleistocene Lake Algonquin

Abstract

A reinterpretation of relative-uplift data associated with the deformed strandline of Pleistocene Lake Algonquin is presented. The new analysis is based on a dynamic model that allows for the finite rate of retreat of the Laurentide ice sheet and the viscous relaxation of the Earth's mantle. Attention is also paid to the effects of the shape of the load profile on the interpretation. In the context of this model the thickness of the lithosphere is constrained to be not more than 85 krn. This value is based on the assumption of a model ice sheet with a parabolic cross section. If the load has a sharper edge, a thickness of 110 km is consistent with the data. These revised values slightly exceed Walcoll's original estimate. They are, on the other hand, distinctly lower than the value of 200 km, which has recently been inferred by Peltier for the thickness of the North American lithosphere. The relations between the different estimates are briefly discussed. It is suggested that a reconciliation of the estimates may require that effects caused by geoidal perturbations be included in future analyses of strandline tilt.