New chronological and stratigraphical data on the Ivrea amphitheatre (Piedmont, NW Italy)

Abstract

The Ivrea amphitheatre (IA) in NW Italy has been studied since 1850, on pedostratigraphic and morphological bases. Three stratigraphic groups of glacial sediments were distinguished. Newly recognized stratigraphic boundaries are based on interstadial/ interglacial units, palaeosols and lacustrine organic layers interbedded with glacigenic deposits, and on pedostratigraphy. Mapping of morphological features and associated marginal and sub-glacial deposit facies was used to characterize and reconstruct glacial margin fluctuations. Based on the field evidence, the stratigraphical limits recognized at single sites can be interpolated over the whole amphitheatre. Ten stratigraphic units (referred to as alloformations: Afs) were distinguished and mapped. They are related to at least as many glacial episodes ranging in age from the end of the Early Pleistocene to the Late Pleistocene. The youngest three glacial units (Serra Af, Piverone Af and Ivrea Af) and one interstadial level (Alice Superiore Unit between Serra and Piverone Afs) are discussed in detail. Based on biostratigraphical and pedological, as well as sedimentological and morphological data, the Serra Af can be attributed to MIS 6 and Piverone Af to MIS 4. The 10 Be surface exposure ages from two boulders (27.973.1, 32.474.0 kyr) on the Serra d'Ivrea moraine provide only a minimum age for moraine construction. The alignment of typical ice marginal landforms (moraines and kame terraces) for the more recent unit (Ivrea Af) has allowed recognition of 12 principal stadials during the LGM and Lateglacial; 6 stadials in the amphitheatre and 6 stadials in Dora Baltea Valley, and reconstruction of the nature of the last glacial retreat from the amphitheatre to the cirques. 10 Be exposure ages from three boulders related to Ivrea Af are 13.171.0, 17.472.6 and 20.871.5 ka. The latter two ages indicate that the Dora Baltea Glacier deposited the Ivrea Af in the IA during MIS 2. The 10 Be exposure ages of 14.671.2 and 14.070.9 ka from a polished bedrock surface some 15 km upstream from the amphitheatre provide a minimum age for ice decay. r

Chronology of the last glacial cycle in the European Alps

“…Monegato et al, 2007). 10 Be data from boulders on moraines in the Ivrea morainic amphitheatre in NW Italy (Gianotti et al, 2008) support the hypothesis that the onset of ice decay at 20.8 AE 1.5 ka in the southern ranges occurred simultaneously with the northern regions.…”

Glacier variations in the European Alps at the end of the last glaciation

“…Blanc massif filled Val d'Aosta and terminated in the Ivrea amphitheatre. The largest moraine, the Serra d'Ivrea, has been attributed to pre-last glacial cycle glaciations (Gianotti et al, 2008;. At Ivrea, Gianotti et al (2008Gianotti et al ( , 2015 report four stadials for the LGM; named Pavone, Bienca, Prà San Pietro and Germano stadials.…”

“…The largest moraine, the Serra d'Ivrea, has been attributed to pre-last glacial cycle glaciations (Gianotti et al, 2008;. At Ivrea, Gianotti et al (2008Gianotti et al ( , 2015 report four stadials for the LGM; named Pavone, Bienca, Prà San Pietro and Germano stadials. The 10 Be dates from the LGM moraines of the Ivrea amphitheatre indicate that pullback from the outermost Pavone moraines was underway by 24±2 ka (Gianotti et al, 2015).…”

“…10 Be ages on glacially striated bedrock located about 30 km upstream from the end moraines at Ivrea of 17-16 ka provide minimum ages for an ice-free lower Val d'Aosta (Gianotti et al, 2008(Gianotti et al, , 2015.…”

Taking Advantage of the ESA G-POD Service to Study Ground Deformation Processes in High Mountain Areas: A Valle d’Aosta Case Study, Northern Italy

“…The morphological traits of the VDA are characterized by the main valley trending east-west (Dora Baltea Valley). This is a wide (3400 km 2 ) glacial valley with several tributary valleys (trending north-south), which ends around the Pont Saint Martin municipality, at the Ivrea moraine amphitheater, the main evidence of Quaternary glaciations [60].…”