Alluvial sand composition as a tool to unravel late Quaternary sedimentation of the Modena Plain, northern Italy
Published:January 01, 2007
Stefano Lugli, Simona Marchetti Dori, Daniela Fontana, 2007. "Alluvial sand composition as a tool to unravel late Quaternary sedimentation of the Modena Plain, northern Italy", Sedimentary Provenance and Petrogenesis: Perspectives from Petrography and Geochemistry, José Arribas, Mark J. Johnsson, Salvatore Critelli
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The Modena alluvial plain is located on the northern side of the northern Apennines fold-and-thrust belt, where streams draining the chain flow toward the northeast into the Po River. The alluvial plain is characterized by a spectacular abundance of archaeological sites of various ages and can be considered a natural laboratory for the reconstruction of the recent sedimentary evolution of the Po Plain. Detailed modal analyses of modern sands of the Modena Plain streams indicate that the provenance signal can be distinguished on the basis of key components, such as quartz, feldspar, carbonate, and lithic fragments. The compositional fields of the streams depend on the extent of the watershed, the recycling of older fluvial sediments, and the sediment input from tributary streams.
The modal analyses demonstrate that sand composition of the major rivers (Panaro and Secchia) has not changed during the Holocene, when sediment production, storage, and dispersal were probably dominated by colluvial aggradation in an environment characterized by dense vegetation cover.
In the late Pleistocene, fluvial sands were characterized by higher feldspar contents compared with modern and Holocene sands. This feldspar abundance could reflect a high-frequency signal in sediment supply rates linked to secular variations of weathering processes, and it reveals the strong denudation and sediment removal conditions of the last glacial stage (15–18 ka).
The implication of this study is that provenance of Holocene sediments now buried in the floodplain can be determined by a simple comparison with modern sand composition. Sand composition studies may represent a useful tool to reconstruct the Pleistocene-Holocene fluvial sediment supply and the evolution of human settlements as function of climate and drainage system changes.