Displacement on the Insubric Line

Abstract

ALTHOUGH the Insubric Line is generally recognized as a major tectonic boundary¹ there is scant agreement regarding its history and its kinematics. The profound influence that the Insubric Line exerts on the geology of the Alps is shown by the following points: it forms the southern limit of high-grade Alpine metamorphism, including early high pressure, and later, intermediate pressure, phases; it forms the southern limit of most of the Pennine nappes. The Dent Blanche nappe and certain Austro-Alpine nappes may be “rooted” to the south of the Insubric Line^2,3; it probably separates regions with markedly different palaeomagnetic declinations⁴; it forms a break in the pattern of radiometric ages, so that some Hercynian gneisses involved in the Pennine nappes yield Alpine ages although these gneisses existing to the south of the Insubric Line show ages of 2-300 m.y.