Types and development of stream terraces in the Marche Apennines (central Italy): a review and remarks on recent appraisals.

The excellent preservation, together with a large number of exposures of Quaternary terrace-alluvium and related deposits, made since a long time the northern Marche (central Apennines) an object of targeted scientific work. The stream terraces exposed in the area can be taken as representative of both arrangement and development of terrace staircases in several river basins draining the Adriatic side of the Apennines. In this frame, this paper focuses on types and development of stream terrace staircases in the northern Marche Apennines both reviewing pre-existing data and providing some appraisals on recent achievements. In this area, the overall pattern of main valleys, which flow eastwards into the Adriatic Sea, was already delineated in the Early Pleistocene-Early Middle Pleistocene, thus allowing initial almost-flat surfaces to be gradually furrowed by valleys where stream terraces could develop. Initially, likely accounting mainly for tectonic controls, only erosive terrace-staircases were formed, which at present are arranged on several levels at the highest elevations above the thalweg. Later on, likely following the so-called “Mid-Pleistocene Revolution”, fill terraces started to develop extensively all along the main valleys. In the northern Marche main valleys, four principal climate-driven fill terraces are found at approximately 100 ka cycle, to which an undefined number of minor and/or local recent units are overlapped. Modes of both fill terrace re-incision and stream entrenchment in bedrock in downcutting regimes also suggest that both warming- and cooling-limb forcing of incision were effective.