Rhythmically stratified periglacial slope deposits
DOI:
https://doi.org/10.26485/BP/1955/2/2Keywords:
periglacial conditions, asymmetrical valleys, slope erosional surfaces, Łódź regionAbstract
This paper deals with the problem of the rhythmically stratified slope deposits which were recognized by Cailleux in 1948 and termed by him eboulis ordonnes. In 1951 similar formations have been described by Y. Guillien who called them grezes litees.
The present writer recognized some rhythmically stratified slope deposits in the valleys of the Escarpment of the Łódź Upland. These formations bear some resemblance to those described in the French literature. They occur in a similar geomorphic situation and display analogous, both structural and textural features. However they differ by their finer fraction and a reverse type of asymmetrical situation. The French eboulis ordonnes and grezes litees occur on east-facing slopes while the rhythmic slope deposits in the region of Łódź are exposed westward.
These rhythmically stratified slope deposits are believed to have originated under periglacial conditions and are being attributed to congelifluction and downwash. It is also assumed that snow drifts accumulated by easterly winds have largely contributed to their formation. The merging of slope deposits with river sands which prevail at the base of the slope deposits is also emphasized. Toward the top an increase of congeliflual activity at the expense of decreasing downwash was also established. The fact may be attributable to the progressive chilling of the climate.
Because of their association with asymmetrical valleys, denudational spurs and troughs as well as pediments, these rhythmic slope deposits are of importance in periglacial morphogeny. Of special interest and importance, however, is their relationship to periglacial erosional surfaces. Periglacial slope erosional surfaces bear some resemblance to terraces of altiplanation as they both belong to the category of pediments.
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