Comparing thin- and thick-skinned thrust tectonic models of the Central Apennines, Italy

The geological structure of the Central Apennines along a section line across the Lazio-Abruzzi carbonate platform has traditionally been interpreted using a thin-skinned thrust tectonic model, in which the sedimentary cover has been detached from an undeformed basement below. Such models have been used to predict that very large amounts of crustal shortening (e.g. 172 km over a section 173 km long) have occurred. Alternatively, in this paper we reinterpret the surface geology and well data along the same section line using a thick-skinned thrust tectonic model. Restoration of this section shows that the amount of shortening (37 km over a section 158 km long) is considerably lower than previously predicted; this is accomplished by open buckling of the carbonate platform, tighter folding of the basin scarp stratigraphy, and reactivation of pre-existing extensional faults. Age bracketing on thrust fault movement allows shortening rates for the two different models to be calculated; these are < 6 mm yr -1 for the new interpretation, but over 24 mm yr -1 for the equivalent thin-skinned model. This latter value is significantly greater than shortening rates reported for most other thrust belts, suggesting that thick-skinned tectonics is a more satisfactory explanation for the structure of this area. The two most important implications of this are that subthrust hydrocarbon plays are largely absent in the area, and Neogene contractional deformation in this part of the Apennines resulted in much less crustal shortening than previously predicted.