A fluvial record of late Quaternary climate changes and tectonic uplift along the Marche Piedmont Zone of the Apennines: New insights from the Tesino River (Italy)

Fluvial terraces are a pre-eminent continental record of climate changes and tectonics. Although the use of fill terraces for incision rate derivation is complicated due to their cyclical nature relative to strath terraces, they remain a relatively complete record of incision and deposition, thus allowing one to derive interpretations about both tectonics and climate. The Adriatic piedmont of the Apennines (central Italy) offers a well-preserved staircase of such terraces, caused by the cyclical alternation of fluvial aggradation and incision over the Middle and Late Pleistocene in response to a combination of low-rate tectonic uplift and climate changes. Although the staircase has been already widely described with examples from several valleys of the Adriatic Piedmont, its geochronological constraints are limited and must be enhanced to extract reliable climatic and tectonic signals from terrace deposits—especially for the older terrace levels. This research provides new Optically Stimulated Luminescence (OSL) data on the terrace chronology in combination with new semi-automatically extracted data on the altimetric and along-valley terrace distributions, as well as the sedimentological characteristics of fill terraces within the Tesino River basin in the Marche piedmont zone of the Apennines. The semi-automatic extraction of the terrace tread allowed a preliminary level classification as a function of the terrace height above the modern channel thalweg. The results demonstrate that, within the slowly uplifting Adriatic piedmont of the Apennines, the main phases of fluvial aggradation occurred during cold and full-glacial conditions followed by river incision and floodplain-channel abandonment during warmer periods. This finding confirms previous results from the last fluvial aggradation-incision cycle (Late Pleistocene). The results also show that the same formation mechanism is valid for the older (Middle Pleistocene) terraces. Indeed, this study provides new geochronological constraints for the regional-scale paradigm of cyclical formation and development of Quaternary fill terrace staircases along this sector of the Apennines. The use of a dated fill terrace staircase allowed estimation of a Middle Pleistocene long-term bedrock incision rate ranging from 0.3 to 0.5 mm yr−1 in agreement with previous studies in the central-northern sector of the Adriatic Apennines. The resulting uplift rate supports the presence of differently uplifted blocks due to the fragmentation of the peri-Adriatic region caused by the activity of left-lateral faults.