This paper concerns the periglacial morphogenesis of slopes occurring on typical relief forms of the Cracow Upland, namely: 1) valleys with asymmetric slopes, 2) undulating plateau with monadnocks, ...and 3) the edge of the tectonic graben. The research aims to reconstruct denudation processes and slope relief development based on the analysis of slope deposit distribution. The analysis was carried out in the context of climate change during the last glacial cycle (the Upper Vistulian).
Evolution of slopes in the investigated area is mainly conditioned by the geological setting, i.e. facies of Jurassic limestones, tectonics, and presence of karstic forms. On the other hand, climate intensified and stimulated the type of denudation processes. Intensive denudation occurred in conditions of cold and wet climate (in the phases of increasing and decaying permafrost). During extremely frosty and dry climate (in the phases of continuous permafrost) denudation processes declined, and loess deposition predominated. In places, the presence of soft deposits protected the substratum against weathering.
The following types of slope evolution dominated: lateral recession, development of convex–concave slopes, slope flattening and elongation, and development of convex slope shapes. Steep slopes were laterally retreated. Gentle slopes were: a) lowered and elongated (especially on the substratum made up of inclined bedded limestones) and b) transformed into convex–concave slopes (on substratum made up of different facies of limestones). A convex profile in the lower part of gentle (deluvial) valley slopes originated as a result of cutting-down by river erosion.
► Periglacial evolution of slopes is conditioned by the geology of the substratum rather than climate. ► Slope evolution is presented for asymmetric valleys, hilltop monadnocks, and fault-line scarps. ► There is no direct relation between the climatic exposition and slope inclination.
La présente mise au point repose sur des observations personnelles dans les provinces du Shanxi et de Pékin en compagnie de chercheurs chinois et sur un dépouillement des publications chinoises ...récentes ou de leurs résumés anglais. Les conclusions sont les suivantes : 1. le dépôt des loess a commencé il y a environ 2500000 ans; 2. les chercheurs chinois distinguent trois « loess » appelés, dans l'ordre chronologique Wucheng, Lishi et Malan; 3. les « loess » Wucheng et Lishi sont, en réalité, des séries complexes de paléosols plus ou moins intensément décarbonatés, à poupées, en place et plus ou moins tronqués, de produits de ruissellement et de quelques intercalations (« Loess Lishi ») de loess éoliens originels; 4. pendant le dépôt de ces formations, comme cela est montré en détail pour le « Loess Lishi », la morphogenèse a été importante (creusement de vallées); 5. le « Loess Malan » se dépose juste après une période de remblaiement fluviatile aux environs de Datong (Shanxi) et coïncide avec une période de climat très rude (pergélisol dans les environs de Datong). Les travaux chinois montrent que, lors des paroxysmes de froid avant 25000 environ et après 22000, l'anticyclone hivernal de la mousson s'étendait plus loin vers l'E.S.-E. qu'actuellement. Des sables éoliens, dans l'Ordos, passent, vers l'E.S.-E., à des alternances de sable et de loess puis à des loess typiques. The present paper synthesises field observations of the Author made in Shanxi and Pekin provinces and recent chinese literature, in part english abstracts. The main points to be focussed are : 1. Loesses began to be deposited around 2500000 years ago; 2. Chinese scientists have distinguished three, « loesses », in chronological order : Wucheng, Lishi and Malan; 3. In fact, what is called « Wucheng Loess » and Lishi Loess » are complex and diversified deposits, consisting of predominant decarbonated material (exclusive in « Wucheng Loess »), truncated paleosoils with carbonate nodules, run-off products and scarce true loess in situ; 4. During the elaboration of these loess complexes, morphogenesis has been very active, mainly under the form of valley cutting, especially during Lishi period; 5. Malan Loess has been deposited, as true aeolian material, just after a period of fluvial aggradation in the region of Datong (Shanxi). Climate was even more continental than the present one, with very severe winters. Permafrost has been recognized near Datong. Chinese scientists consider that, during each of the two last colder periods, before 26000 BP and after 22000 BP, the Winter Monsoon high pressures had a greater extension towards E.S.-E. than presently. In the Ordos region, Shaanxi Province, wind blown sand merges in an interstratified alternance of sand and loess layers and, further E.S.-E., in pure loess.
