Pressure-solution fabrics and their overprinting relationships within a minor fold train of the Umbria-Marche Apennines, Italy

Analysis of mesoscopic folds that affect pelagic carbonates of the Upper Jurassic-Lower Cretaceous Maiolica Fm. in the Umbria-Marche Apennines reveals a complex structural history. Bedding-parallel stylolites, that were produced during or soon after deposition as a consequence of an overall extensional deformation, are generally overprinted by bedding-normal pressure-solution cleavage related to the early stages of folding. These relationships are reversed in the steep fold limbs, where pressure-solution cleavage appears locally overprinted by bedding-parallel stylolites. The oblique relationship among the stylolitic surfaces and the columnar peaks supports the hypothesis of reactivation of dissolution processes along early, pre-folding stylolites during the advanced stages of folding. Systematic recognition of these relationships in other folded sequences is important, in that it may provide relevant constraints for the quantitative estimates of orogenic contraction across fold-and-thrust belts.