LAST GLACIAL MAXIMUM GLACIOLACUSTRINE DEPOSITS FROM THE ADIGE MORAINE AMPHITHEATRE (RIVOLI VERONESE, NORTHERN ITALY): DISTRIBUTION, SEDIMENTARY FACIES, AND SIGNIFICANCE

Proglacial lakes formed between ridges, small fluvioglacial plains and glacier fronts of end-moraine systems are excellent sedimentary archives capable of accurately recording environmental variations linked to deglaciation. The Adige Moraine Amphitheatre (AMA) at the outlet of the Adige Valley in the southern foothill of the Alps (Rivoli Veronese, Verona; Northern Italy) is a multi-moraine ridges system built during the Last Glacial Maximum (LGM) by two subsequent glacial advances of the Adige Glacier. Within the innermost moraine arc of the AMA, the topography of glacial deposits acted as a dam originating two separated proglacial lakes, collecting meltwaters. Geomorphological and geological mapping allowed identifying the vestiges of a complex glaciolacustrine system with a branching proglacial lake in which deltaic and ice-contact situations coexisted. Four sedimentary facies associations suggestive of ablating ice-front, glaciofluvial, deltaic, and glaciolacustrine depositional settings were recognised, and their spatial relationship clarified through facies analysis. Results suggest the proglacial lake was likely enclosed by the glacier front, moraine ridges, and other glacial deposits that obstructed the pre-existent Adige Canyon, and that the two identified lake branches coalesced during the final phase of glacier retreat. The process controlling the draining of the lake is not completely known, but the occurrence of boulders (recurrently named as “erratics”) in the uppermost deposits of the Adige River glaciofluvial fan to the south of AMA suggests these may represent mega-clasts transported during the post-LGM collapse of the Adige Glacier. We propose that these mega-clasts were mobilized by a glacial lake outburst flood resulting from the collapse of the deposits obstructing the Adige Canyon upstream. Our results add to better understanding of the AMA deglaciation phases and to the reconstruction of the LGM-Post-Glacial transition period in the foothills of the southern Central Alpine region.