Superfici terrazzate pleistoceniche nella media valle del Fiume Crati (Calabria)

Abstract

A stretch of the central portion of the River Crati valley on the south of Tarsia, between the western slope of Greek Sila and the eastern slope of the "Catena Costiera" (Coastal Chain) was investigated. Sediments of Lower Pleistocene outcrop mainly in this portion of the valley; eastward, these sediments overlie directly the Paleozoic crystalline units of Sila, whereas in the Tarsia area, they are also found above conglomerate, sandstone and limestone of Middle-Upper Miocene age, westwards, clay, sand, and conglomerate of Lower Pleistocene are deposited in this order, overlying in places clay of Middle-Upper Pliocene age. The tectonic uplifting of the area, that brought Pleistocenic marine sediments to elevations of over 500 m, caused an intense erosion, leading to the formation of a dense hydrographic network; thus the present morphology is characterized by narrow and extended ridges, coinciding with the watersheds of Crati, Follone and Esaro rivers and all their tributaries. These ridges slope gently down to the valley; however, their profile is irregular, being characterized by both minor and major dip reaches and by gentle undulations (topographic culminations or summits). The subhorizonta! stretches and the summits, considered as relic forms of surfaces dismantled by erosion, were the morphological elements utilized to identify the ancient terraces of the River Crati valley. The adopted methodology was based upon quantitative analysis of the available morphological elements: topographic culminations, subhorizontal stretches of ridges and the scarps along the ridges, according to the terrace nomenclature model proposed in Fig. 4. The agreement between the results obtained by the three methods allowed a map of the ancient terrace surface to be prepared; twelve orders of terraces were recognized from about 150 to 750 m in elevation. Hypotheses as to the origin of terraces and the tectonic and eustatic causes of their formation are also given.