Geology Reference
In-Depth Information
From a practical point of view, we need only be concerned with the more recent cold-
climate fl uctuations. This is because most periglacial landforms and deposits that formed
in earlier cold periods are unlikely to have survived to the present day without having
been modifi ed beyond recognition by either later cold stages or by intervening (intergla-
cial) periods of more temperate climate.
The record of the last 100 000-150 000 years is also illustrated by the oxygen-isotope
curves obtained from the Byrd Station (Antarctica) and Camp Century (Greenland) ice
cores (Figure 11.3). They indicate that, in both Europe and North America, the penulti-
mate cold stage (Illinoian/Riss; OIS-6) occurred some time prior to 150 000 years BP. The
last interglacial, or warm, period (Sangamon/Eemien; OIS-5e) is generally believed to
have lasted until
120 000 years ago, after which the climate deteriorated during OIS-4
through OIS-2. The fi nal cold stage lasted until approximately 10 000 years ago. Not sur-
prisingly, the last cold period (Wisconsinan/Weichselian) is best known, and several
∼
Figure 11.3.
Oxygen-isotope records obtained from ice cores. (A) Byrd Station, Antarctica. (B)
Camp Century, Greenland, together with time scale. (C) Generalized Late-Quaternary isotope
stratigraphy, and July temperatures inferred from palynology. Colder temperatures are indicated
by decreasing O
18
values (shaded areas). From Johnsen et al. (1972), West (1977, fi gure 10.10),
Vandenberghe and Pissart (1993).
