The interaction of climate and tectonics since the Middle Pleistocene in the Marche Piedmont Zone of the Apennines: new geochronological data from the fluvial record.

The climatic and tectonic history of the Piedmont zone of the Apennines has been reviewed by leveraging the depositional records of the Tenna, Aso and Tesino Rivers, located in the Marche region of Central Italy. The westernmost part of this region has been subjected to uplift since the Middle-Late Pliocene, resulting in the emergence of the area, due to the propagation of the compressional front of the Apennines. Several studies, predominantly based on methodologies that rely on the sedimentological record, have obtained for the Marche Piedmont Zone uplift rates ranging from 0.2 to 0.7 mm yr⁻¹. The low-rate uplift activity has left as evidence different features, including also well-developed staircases of fluvial terraces of the fill type. The formation of this terrace type is strongly influenced by climate variations. From this perspective, fluvial terraces are recognized as impact-oriented indicators of middle-long term climatic oscillations, contributing to the aims of the extended partnership RETURN (multi-Risk sciEnce for resilienT commUnities undeR a changiNg climate). Indeed, the Italian National Recovery and Resilience Plan (PNRR), funded by Next Generation EU, aims to consolidate research on environmental, natural, and anthropogenic risks connected to climate change.

By extracting chronological and sedimentological data from the fill terrace deposits of the three selected rivers it was possible to assess and delineate the dynamics associated with the landscape evolution of the study area. Luminescence dating techniques were applied on the deposits to determine the timing of sedimentation of the fluvial terraces, yielding a total of eleven ages, that extend back to the Middle Pleistocene. We preliminary conducted a semi-automatic extraction of the terrace treads from high-resolution LiDAR DTMs of the river valleys: from these, the topographic slope and roughness were calculated and applied for the extraction of smooth sub-planar surfaces corresponding to the treads of the terraces. This process was essential for classifying the terraces into different levels based on their height above the channel thalweg, thereby contributing, together with on-field characterization of the deposits, to the creation of an updated map of the fluvial terraces, followed by the analysis of their altimetric and along-valley distribution.
The obtained new data has been reviewed both at the level of the individual rivers and in relation to Late Pleistocene - Holocene data already available from terrace deposits of other rivers of the Marche region. This enabled the analysis in parallel of the emplacement of different terrace levels both inside each valley and between adjacent ones, allowing the extraction of new uplift rates relative to the Piedmont zone of the Apennines and the recognition of differential uplift acting in correspondence to the studied area. Furthermore, owing to the overall expansion of the chronological record relative to the terrace deposits, it was possible to evaluate the correlation between the timing of fluvial deposition and the alternation between glacial and interglacial stages characteristic of the Quaternary, determining that sedimentation on the valley floor is strongly influenced by the effects of glacial stages on vegetation and sediment stabilization along the slopes, bringing to fluvial sedimentation.