Environmental Engineering Reference
In-Depth Information
During the last Pleistocene cold stage the Maritime Alps were extensively glaciated
and the ice masses were contiguous with the main Alpine ice sheet. Lacustrine sedi-
ments at Lac Long Inferieur, a glaciated cirque (2090 m asl) in the French Maritime
Alps, indicate that ice had melted by 14.19
±
0.13 ka
14
C BP (Ponel
et al
., 2001).
Glacier retreat was punctuated by several readvances, and on the Italian side of the
Argentera massif, Fisinger and Ribolini (2001) documented evidence for several
glacial advances during the Late-glacial substage. In Italy, outlet glaciers from the
Maritime Alps' ice sheet descended the Gesso and Stura di Demonte valleys and
nearly to the Po Plain. The lowest frontal and lateral moraines in the Gesso Val-
ley have recently been dated using
10
Be nuclide analysis (Granger
et al.
, 2006).
Boulders sampled on two separate moraine crests gave mean
10
Be cosmogenic
ages of 16.3
1.0 ka. Granger
et al.
(2006) argued that these two
moraines represent the inner and outer moraine crests of the same glacial event.
The older maximum age of the Gesso glacier is broadly consistent with the Alps
further north, where the northern lobe of the Rhone glacier reached its maximum
extension between c. 21.0 and 19.1 ka around the time of the global LGM (Ivy-Ochs
et al.
, 2004). Later glacier advances at higher elevations in the Gesso valley have
also now been dated using
10
Be exposure age dating (Federici
et al
., 2008). Four
boulder samples from the Piano del Praiet frontal moraine gave a weighted mean
age of 11.3
±
0.4 ka. Federici
et al.
(2008) suggest that the frontal moraine corre-
lates with the Egesen Stadial of the Alps (Younger Dryas) and they argue that this
suggests a synchronicity of the Egesen deglaciation across the European Alps.
±
0.9 and 18.8
±
3.2.5 Italian Apennines
Traces of glaciation are recorded throughout the Italian Apennines - extending
from the Ligurian Alps in the north to the Appennino Calabro in the south. The
Apennines reach an altitude of 2912 m asl at Corno Grande in the Gran Sasso, cen-
tral Italy. Here, Giraudi and Frezzotti (1997) have demonstrated that the maximum
glacier extent of the last cold stage (Wurmian) occurred prior to 22.7
0.6 ka
14
C
BP. At the glacier maximum, ice in the Campo Imperatore area of the Gran Sasso
extended 10.5 km down-valley and covered an area of 19 km
2
with an equilibrium
line altitude (ELA) of c. 1750 m. A series of recessional moraines and rock glaciers
in the Gran Sasso are thought to correspond to periods of glacier stabilization or
readvance between 20 and 10 ka
14
CBP.
Middle Pleistocene glacial deposits older than those considered to be of Wurmian
age are usually less well preserved and are often strongly eroded, smoothed and
smaller in size (Federici, 1980). Kotarba
et al.
(2001) presented U-series ages for
calcite cements within these moraines as old as 135
±
10 ka. Thus, given that the
cements formed after the host deposits were formed, the moraines supported corre-
lation with the Rissian Stage of the Alps (Kotarba
et al.
, 2001). It is therefore clear
that at least two major glacial advances are recorded in the Gran Sasso area, with
readvance also recorded during the Wurmian Late-glacial.
±
