Periglacial landforms
199
Figure 8.31. Slopes on detrital Cretaceous sediments with a continuous cover of nonsorted deposit
affected by active gelifluction. The foot of the slope has been undermined by fluvial action during the thaw
season. James Ross Island, east of the Antarctic Peninsula. Photo: A. Martfn-Serrano.
Kirkby, 1972). Generally, scarp retreat in periglacial environments is slower than in other
morphoclimatic zones, although this process depends largely on the litho-structural
characteristics of the rock face and on microclimatic conditions determined by
factors such as the orientation (Souchez, 1966).
The benched-slopes result from cryoplanation processes that produce the flattening
and decrease in inclination of the profile. The erosion in the upper parts of the
slope and sedimentation in the lower ones, mainly in the valley bottoms, involve
parallel retreat of the scarps and widening of the benched slope segments. These
ideas were introduced by Peltier (1950) in his "cycle of periglacial erosion"
(Figure 8.32).
The convex-concave slopes are characterised by a profile without irregularities.
They are mantled by a continuous cover of frost-shattered clasts (Figure 8.33) that may
be affected by gelifluction, surface wash and filling in sectors with high gradient. The
incision of these slopes by gully systems may give place to tripartite slopes or
triangular slope facets (Bfidel, 1982) (Figure 8.34). The gullies responsible for the
dissection of the slopes develop small low-gradient debris cones in the lower part
of the slope. Once the slope facet is disconnected from the upper part of the slope, it
hardly receives overland flow and becomes a relict landform with a high preservation
potential. The alternation of accumulation and incision periods in these slope systems
gives place to sequences of tripartite slopes.
199
Figure 8.31. Slopes on detrital Cretaceous sediments with a continuous cover of nonsorted deposit
affected by active gelifluction. The foot of the slope has been undermined by fluvial action during the thaw
season. James Ross Island, east of the Antarctic Peninsula. Photo: A. Martfn-Serrano.
Kirkby, 1972). Generally, scarp retreat in periglacial environments is slower than in other
morphoclimatic zones, although this process depends largely on the litho-structural
characteristics of the rock face and on microclimatic conditions determined by
factors such as the orientation (Souchez, 1966).
The benched-slopes result from cryoplanation processes that produce the flattening
and decrease in inclination of the profile. The erosion in the upper parts of the
slope and sedimentation in the lower ones, mainly in the valley bottoms, involve
parallel retreat of the scarps and widening of the benched slope segments. These
ideas were introduced by Peltier (1950) in his "cycle of periglacial erosion"
(Figure 8.32).
The convex-concave slopes are characterised by a profile without irregularities.
They are mantled by a continuous cover of frost-shattered clasts (Figure 8.33) that may
be affected by gelifluction, surface wash and filling in sectors with high gradient. The
incision of these slopes by gully systems may give place to tripartite slopes or
triangular slope facets (Bfidel, 1982) (Figure 8.34). The gullies responsible for the
dissection of the slopes develop small low-gradient debris cones in the lower part
of the slope. Once the slope facet is disconnected from the upper part of the slope, it
hardly receives overland flow and becomes a relict landform with a high preservation
potential. The alternation of accumulation and incision periods in these slope systems
gives place to sequences of tripartite slopes.