Evolution of an Alpine fluvioglacial system at the LGM decay: The Cormor megafan (NE Italy)

摘要: Abstract The dramatic climatic and environmental changes that occurred at the end of last glaciation led to formation landforms (e.g., moraines, fluvial ridges, alluvial terraces) strongly characterize landscape in plains facing Alps. This also with Tagliamento glacier, which built a large LGM moraine amphitheatre piedmont sector southeastern Alps fed fluvioglacial systems Friulian plain (NE Italy). Cormor stream was one main glacial outwashes formed an megafan during peak LGM. At decline LGM, active belt narrowed subsequently abandoned. Since Lateglacial system has been intermittent limited activity. sequence events preservation surfaces, enables their investigation, along correlatable ridges. study depositional phases allows us precisely constrain chronology withdrawal is difficult sectors southern geomorphological geological realized through use remote sensing, DEM analysis, field survey, stratigraphic boreholes, radiocarbon dating. During experienced widespread aggradation gravel deposition up 15–25 km from apex, while distal dominated by fine-grained sediments. incised apical portion its megafan, funnelling sedimentary discharge experiencing progradational lobe. buried some swampy areas, sealing peaty organic-rich clayey horizons 2–4 m top these layers dated 22.0–19.5 ka cal BP indirectly constrains several recessional moraines within amphitheatre. After this phase, deactivated because water sediment concentration catchment River. demonstrates possibility reconstruct timing studying related outwash plain. Moreover, new geochronological dating chronological comparison eastern Southern global chronology. results suggest we can apply approach part other megafans Alpine central Po where almost lacking.