Geology Reference
In-Depth Information
bedded sediments indicates a change to sheet solifl uction and slopewash on a progressively
lower-angled slope. A second series of lobate deformations occur in an upper layer of
stratifi ed sand. Overlying all these sediments, and extending to the foot of the present
slope, is a layer of cross-bedded sand and gravel with numerous pebble layers.
These slope deposits indicate a progressive change in the form of Gora Sw Malgorzata.
In the earliest phase, probably at the beginning of the last cold period, solifl uction and
slopewash sediments obliterated the braided channel. As a result, the slope became longer
and gentler. Then, solifl uction fi lled the channel depressions and gave a step-like (lobate)
profi le. As slope gradient progressively decreased, stratifi ed slopewash sediments were
deposited and the slope assumed a smoother profi le. Ultimately, the ancient channel relief
was obliterated by a gentle depositional slope of 2-4° in angle. Further slope evolution
was terminated by the deposition of bedded gravels which extend to the foot of the
present-day hill. These suggest that the pradolina came into operation once again.
In terms of landscape modifi cation, the sediments that fl ank the lower slopes of Gora
Sw Malgorzata indicate continued slope modifi cation throughout the last cold stage. Solif-
luction and sheetwash processes progressively reduced and extended the lower part of the
slope while the upper part experienced erosion and retreat. Ultimately, a near-stable slope
was probably attained. Then, during the climatic amelioration that accompanied the end
of the cold stage, a second phase of solifl uction was initiated before the lower slope was
buried beneath fl uvial sediments when discharge through the pradolina commenced.
ADVANCED READING
Ballantyne, C. K., Harris, C. (1994).
The Periglaciation of Great Britain
. Cambridge University
Press, Cambridge, 330 pp.
Dylik, J. (1969). Slope development under periglacial conditions in the Łód˙ region.
Biuletyn
Peryglacjalny
,
18
, 381-410.
Schokker, J., Koster, E. A. (2004). Sedimentology and facies distribution of Pleistocene cold-climate
aeolian and fl uvial deposits in the Roer Valley Graben (Southeastern Netherlands).
Permafrost
and Periglacial Processes
,
15
, 1-20.
Vandenberghe, J. (1993). Changing fl uvial processes under changing periglacial conditions.
Zeitschrift für Geomorphologie
, suppl.
88
, 17-28.
DISCUSSION TOPICS
1. Describe the typical landscape modifi cations that took place under periglacial condi-
tions in the mid-latitudes during the Pleistocene.
2. Discuss the roles of snow, rain, wind, and aspect in the context of landscape modifi ca-
tion during the cold periods of the Pleistocene.
3. What are the causes of asymmetrical valleys and what do they tell one about Pleis-
tocene periglacial conditions?
4. What was the role played by fl uvial processes in fashioning the Pleistocene periglacial
landscapes of mid-latitudes?
