Quaternary uplift vs tectonic loading: a case study from the Lucanian Apennine, southern Italy

Uplift rates have been calculated for a large sector of the Lucanian Apennine ("axial zone" of the southern Apennines, Italy), using both geomorphological observations (elevation values, ages and arrangement of depositional and erosional landsurfaces and other morpho-tectonic indicators) and stratigraphical and structural data (sea-level-related facies, fault kinematics and offset estimations). These data have been compared with those derived from clay mineralogy of Mesozoic pelagic successions (Lagonegro units), outcropping in the same sector of the chain, which gave information on tectonic loading. The values of the Quaternary uplift rates of the southern Apennines axial zone vary from a minimum of 0.2 mm/yr to a maximum of about 1.2 mm/yr. Intermediate values (0.5-0.7 mm/yr) have been calculated for the other studied areas. Using geomorphological features and late Pliocene to Pleistocene successions involved in the genesis of erosional and depositional landsurfaces, the same rates (similar to0.6 mm/yr) have been obtained for a large time span (about 2 Ma) in the Melandro basin and adjacent Maddalena Mts. Therefore, during the last 2 Ma, the total uplift amount of the axial zone of the Lucanian Apennine is about 1.2-1.3 km, with local peaks of 1.5 km. On the other hand, the Mesozoic pelagic units experienced a tectonic loading of 4-5 km, as estimated by means of illite crystallinity (in the range 0.6-1.1 Deltadegrees2theta), percentage of illitic layers in illite/smectite mixed layers (60-90%) and white mica polytypes (in the range of 10-35%). The Quaternary uplift and the related erosion rates of the southern Apennines are unquestionably due to strike-slip faulting and, above all, due to extensional tectonics coupled with thermal/isostatic regional raising. The gap of several kilometres derived from the comparison between uplift rates and tectonic loading values may be explained only by different exhumation modalities starting from late Miocene time. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved.