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162. Correlation of Alpine glaciation and global glacioeustatic changes through intergrated lake and alluvial stratigraphy in N-Italy

Author

MONEGATO G., PINI R., RAVAZZI C., REIMER P., and WICK L.

Subjects
penultimate glaciation, lake evolution, Late Pleistocene, sediment provenance, Alps, glacioeustatic oscillations, palynostratigraphy
Abstract

We compare lake and alluvial stratigraphy along a frame connecting the southern Alpine foothills and the Adriatic Sea, with the aim of matching the effects of Alpine glaciation and sea-level changes on sedimentation during the last glacial cycle. The palynostratigraphy of Lake Fimon provided proxies for regional vegetation and climate change and was coupled with sediment petrography, loss on ignition and magnetic susceptibility, disentangling alluvial phases from fluvioglacial activity related to culminations of the southeastern Alpine glaciers. The Fimon area was not reached by alluvial fans during the penultimate glacial maximum, nor by the sea transgression during the last interglacial, but a closed lake soon developed at the Eemian onset due to enhanced rainfall. Sea-level fall at glacial inception triggered the entrenchment of the drainage network in the plain reaching the outer Fimon Basin. Slow aggradation, but no sign of fluvioglacial activity, lasted to 38.21.45 cal. ka BP, when a major forest withdrawal took place, coeval to the spread of alluvial fans. By 27.50.5 cal. ka BP the Fimon Basin was dammed by the Brenta outwash system. The main step of of forest recovery commenced at around (15.8) cal. ka BP, when apex trenching of the outwash fans was triggered by the glacier's decay.

Published
2011
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189. The latest LGM culmination of the Garda Glacier (Italian Alps) and the onset of glacial termination. Age of glacial collapse and vegetation chronosequence

Author

Ravazzi, C, Pini, R, Badino, F, DE AMICIS, M, Londeix, L, Reimer, P, BADINO, FEDERICA, DE AMICIS, MATTIA GIOVANNI MARIA, Reimer, P., Ravazzi, C, Pini, R, Badino, F, DE AMICIS, M, Londeix, L, Reimer, P, BADINO, FEDERICA, DE AMICIS, MATTIA GIOVANNI MARIA, and Reimer, P.

Abstract

In the deglacial sequence of the largest end moraine system of the Italian Alps, we focused on the latest culmination of the Last Glacial Maximum, before a sudden downwasting of the piedmontane lobe occupying the modern lake basin. We obtained a robust chronology for this culmination and for the subsequent deglacial history by cross-radiocarbon dating of a proximal fluvioglacial plain and of a deglacial continuous lake sedimentation. We used reworked dinocysts to locate sources of glacial abrasion and to mark the input of glacial meltwater until depletion. The palynological record from postglacial lake sediments provided the first vegetation chronosequence directly reacting to the early Lateglacial withdrawal so far documented in the Alps. Glacier collapse occurred soon after 17.46 ± 0.2 ka cal BP, which is, the Manerba advance culmination. Basin deglaciation of several overdeepened foreland piedmont lakes on southern and northern sides of the Alps appears to be synchronous at millennial scale and near-synchronous with large-scale glacial retreat at global scale. The pioneering succession shows a first afforestation step at a median modeled age of 64 years after deglaciation, while rapid tree growth lagged 7 centuries. Between 16.4 ± 0.16 and 15.5 ± 0.16 ka cal BP, a regressive phase interrupted forest growth marking a Lateglacial phase of continental-dry climate predating GI-1. This event, spanning the most advanced phases of North-Atlantic H1, is consistently radiocarbon-framed at three deglacial lake records so far investigated on the Italian side of the Alps. Relationships with the Gschnitz stadial from the Alpine record of Lateglacial advances are discussed

Published
2014

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