The Caledonian foreland basin in Scandinavia: Constrained by the thermal maturation of the Alum Shale

Abstract

Various palaeotemperature estimates from preserved Palaeozoic sedimentary rocks in Sweden indicate the existence of a considerably higher temperature in the past. Earlier workers have suggested that the reason for this higher palaeotemperature was due to the development of a foreland basin which buried the sediments, during the Caledonian orogeny. Palaeotemperature estimations from vitrinite reflectance are indicating a maximum palaeotemperature of approximately 165 °C for the autochthonous Alum Shale in Jämtland and 100 °C for the Alum Shale in Västergötland. These palaeotemperature estimations converted to burial depths are used as boundary conditions in the modelling of the Caledonian mountain range and the connected foreland basin. This study suggests, that to accommodate a basin fitting palaeotemperature constraints, a mountain chain similar to the Himalayas must have occurred, which implies a flexural rigidity of the lithosphere in the order of 4×1024 Nm. The heat flow is assumed to have been approximately 60 mW/m2. The model is used to estimate the overthrusted load of the Caledonian mountain range from calculated burial effects of an elastic lithosphere and does not include any other heat producing sources, i.e. fluid flow or igneous intrusions on a regional scale.