Environmental Engineering Reference
In-Depth Information
Figure 3.5
The Pleistocene Sanabria ice cap over the Sierra de la Cabrera and Sierra de
Segundera in northwest Spain. Reproduced from Cowton
et al.
(2009), with permission from
Elsevier
extensive glaciation was characterized by a large plateau ice cap, which covered an
area of more than 440 km
2
, with a maximum ice thickness of c. 300 m and outlet
glaciers reaching as low as 1000 m (Figure 3.5). Radiocarbon dates from the base
of lacustrine sequences appear to suggest that the most extensive phase of ice-cap
glaciation occurred during the last cold stage (Weichselian), with deglaciation oc-
curring before 14-15 ka
14
C BP. A second phase of glaciation is recorded by the
moraines of valley glaciers, which may have drained small plateau ice caps; whilst
a final phase of glaciation is recorded by moraines in the highest cirques.
West of the Sanabria National Park are the Queixa (Galicia, Spain) and Geres
(Portugal) massifs. Here,
21
Ne and
10
Be cosmogenic isotope analyses have been ap-
plied to date glacially polished bedrock surfaces and push-moraine boulders. Three
glacial phases have been identified, with the oldest two being of Middle Pleistocene
age and the youngest glaciation dating from the last cold stage of the Pleistocene
