Tectonic evolution of the Corsica‐Apennines‐Alps region studied by the method of successive approximations

Abstract

Paleotectonic and paleogeographic maps are often very complex. Users find it difficult to evaluate the extent to which the features shown are based on reliable geologic data, and it is not generally possible to estimate uncertainties in shapes and positions. In the scientific tradition of designing simple models to represent complex reality, this study uses systematically simplified palinspastic models to study the tectonic evolution of the central Mediterranean. The prime constraint is northwestward motion of the African continent toward Europe at 7.5 km/m.y. In the “first‐approximation” model, only unidirectional plate motion is allowed, and the model is unable to generate both the Alpine and Apennine orogenic belts, at right angles to each other. The “second approximation” allows rotations. It is surprising how well this very simple model, with its rigidly restrictive rules, reproduces the known evolution of the central Mediterranean. This agreement allows some optimism that the second approximation is correctly modeling the primary features of the tectonic evolution of the central Mediterranean. Revising the shapes of the tectonic entities in a “third approximation” would allow the final pattern to mimic even more closely the present tectonic situation in the Mediterranean, but here the advantages of rigid simplification would start to diminish. The first conclusion of the paper is thus that strongly simplified models are useful in tectonic studies and are justified in light of the uncertainties. Simplified models are used to explore the recently proposed “Ancient‐Apennine” hypothesis, in which Apennine deformation begins with a reversal of subduction polarity at about 100–90 Ma. This view contrasts with the standard “Young‐Apennine” hypothesis, in which subduction reversal and the onset of Apennine orogensis do not occur until 35–30 Ma. Study of the simplified tectonic models leads to the second conclusion of the paper, that the Ancient‐Apennine hypothesis honors regional constraints as well as the standard view does. The simplified modeling suggests specific tests in Alpine Corsica for choosing between the Young‐Apennine and Ancient‐Apennine hypotheses.