CASTIGLIONI G. B. con contributi di – with contributions by BONDESAN M., ELMI C., MARCHETTI G. & PELLEGRINI L.
Le risposte del sistema fluviale alle variazioni ambientali – Response of the fluvial system to environmental variations
Pages 165-187
Abstract
The «fluvial system» of the Po Plain) including the mountain basins of the rivers it contains) embraces an area ofabout 115;000km 2 • Without neglecting references to the mountainous part) the entire framework of the Plain) shown in the Geomorphological Map, allows an approach to many problems) both general and as regards specific sectors) in which case the expression «subsystem» is used in an elastic manner. In Chapters 5 and 9) this fluvial systembad already been described in overall terms: its main axis/ the two subsystems oftributaries (very different from each other) on both sides/ and the independent Veneto and Romagna systems. The whole system euoloed, was modified in time as the two mountain chains developed and were subsequently eroded as the basin between them was filled in) and is primarily the product of the geological history of the entire basin) including its relationships with sea level changes in the Mediterranean and climatic history. As regards the duration of this evolution) the time-scale involves tens ofmillions of years) although this is not the span used in this chapter. Only in a single case can we refer to the Upper Miocene (about 6 million years ago), regarding the development of fluvial morphology linked to considerable variations in sea level (see later). For the rest) most of the problems of the «response of the fluvial system to environmental variations» which the authors of the Map implicitly or explicitly face) refer to the interval from the Middle-Upper Pleistocene to the Holocene) including historical and present-day times) during which completely new factors ofvariation occurred, linked to antbropization. During this period, bearing in mind the fact that many questions have long been debated, e.g., fluvial terraces variously interpreted as «tectonic», «eustatic» or «climatic», etc., it is useful and possible to focus) albeit briefly) on issues…
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