Effects of the Last Glacial Maximum in
the northern Prince Charles Mountains
Recent mapping of lateral moraines located alongside the major glaciers in the northern Prince Charles Mountains has been aimed at identifying those associated with the Last Glacial Maximum (LGM), ~20,000 years ago. The altitude of these moraines, relative to present glacier surfaces, provides an indication of how large the glaciers were at that time. Contrary to previously held beliefs that substantial glacier expansion, up to hundreds of metres, occurred during the Last Glacial Maximum, these lateral moraines are located only tens of metres above the present glacier surfaces, indicating that there were, in fact, only modest increases in ice volume. This work, which includes an on-going cosmogenic isotope exposure age dating study of boulders from the lateral moraines, has important ramifications for understanding the way in which the Antarctic Ice Sheet and outlet glaciers respond to climate change.
.gif)
View towards the east across a vast ice-covered moraine field on
the northern side of Crohn Massif, Porthos Range, northern Prince
Charles Mountains. This is a type of lateral moraine feature,
deposited by the Scylla Glacier. It consists of a thin (<1m)
layer of boulders deposited over very slow moving or stagnant ice.
The arcuate ridges next to the snowbank at the left are from a small
rock glacier that is flowing into the moraine field from the slopes
of Crohn Massif (M. Mabin, 1995) © Copyright
Australian Antarctic Division.
.gif)
Last Glacial Maximum (~20,000 years ago) moraine on the lower
slopes of Martin Massif. The LGM is marked by the boulder scatter and
abrupt line that runs across the slope on the right side of the
image. The moraine is 40m above the area of scattered snowbanks and
ice-covered moraine below (M. Mabin, 1995) ©
Copyright Australian Antarctic Division.
.gif)
Last Glacial Maximum lateral moraine ridge on the eastern slopes
of Mount Creighton. The relatively unweathered angular boulders of
the moraine (on the right of the image) contrast with the much older
subdued, weathered, and boulder-free surface (to the left) (M. Mabin,
1995) © Copyright Australian Antarctic
Division.
.gif)
Aerial view of the lower slopes of eastern Loewe Massif, northern
Prince Charles Mountains. The curving line running from the bottom
left is a moraine ridge deposited by the Nemesis/Charybdis Glaciers
during the Last Glacial Maximum. Ice flowed from right to left. The
area is about 3 km from and 150m above the present glacier. Note the
contrast between the dark brown, very bouldery surface of the Last
Glacial Maximum moraine area, and the subdued, red-brown boulder-free
surface to the upper left. This suggests a considerable age
difference between the two land surfaces (M. Mabin, 1995) © Copyright Australian Antarctic Division.
.gif)
View of the Last Glacial Maximum moraine ridge shown in the
previous image. Eastern slopes of Loewe Massif, northern Prince
Charles Mountains in the background. Ice flowed from left to right
depositing the dark brown bouldery ridge behind the quad. Boulders
are mainly charnockite derived from Loewe Massif (M. Mabin,
1995) © Copyright Australian Antarctic
Division.
.gif)
Aerial view towards the southwest across the southern part of
Radok Lake, Amery Oasis, northern Prince Charles Mountains. The
Battye Glacier ice tongue floats on the lake surface which is located
7 m above sea level. The ice on the lake is ~2 m thick, and is
semi-permanent. Areas around the edge and near the ice tongue melt
each summer, and occasionally the whole surface becomes ice free.
Radok Lake is the deepest lake in Antarctica. A sounding by Jon Luly
and Mark Mabin in 1996 near the tip of the ice tongue reached 335m
depth. Previously, Russian scientists had reported a depth of 346 m
but it is not known where this was taken. The floating part of the
Battye Glacier ice tongue is about 2 km long and flows at about 80m
per year. Since this image was taken in January 1990, several hundred
metres of the tip have broken off and floated away to the north (M.
Mabin, 1990) © Copyright Australian Antarctic
Division.
.gif)
Slopes at the northern end of the Radok Lake basin. These slopes
are cut in the sandstones of the Amery Group rocks and rise about 150m above the lake. The horizontal line running across the slope about
two-thirds of the way up is believed to be a lake shoreline formed
when Radok Lake was considerably deeper than at present, but it is
not known when this occurred (M. Mabin, 1990) ©
Copyright Australian Antarctic Division.
Information Sources:
Mabin, M.C.G. (1992) Late Quaternary ice surface fluctuations of the Lambert Glacier. In: Yoshida, Y., Kaminuma, K. and Shiraishi, K. (editors) Recent Progress in Antarctic Earth Science, p. 683-687. Terra Scientific Publishing Company, Tokyo.
Mabin, M.C.G. (personal communication, 1997)
Further information regarding this work can be obtained from Dr. Mark Mabin:
 |