Abstract
Below the actual surface a depth of a few decimetres (as a rule 1…2 m) has been modified decisively by the periglacial conditions of the last glacial period (Weichselian respectively Wuermian). The characteristics as well as the subdivision of the active layer of permafrost soils have been shaped by processes of cryoclastics, cryotranslocation, cryoperstruction and cryopedogenesis, each of them subdivided by particular sub processes. During the last decades a lot of investigations and discussions have been addressed to these phenomena of the pedosphere, but, however, different authors have turned their attention and considerations to different aspects of the complex interplay. Different concepts have accentuated different aspects of profile subdivision: A concept of covers (in German “Decken”) has been based mainly on processes of cryotranslocation. On the other hand a concept of zones has been deduced mainly from processes of cryoperstruction and cryopedogenesis. The main difference of both these concepts consists in the basic criteria: The zone concept interprets any sedimentary differentiation of substrates as secondary criteria. This concept concedes equivalent zones in differing materials as well as different zones in equivalent materials. On the other hand the cover concept evaluates a dominating role of the sedimentary processes for the vertical substrate subdivision nevertheless conceding an essential share of sub processes belonging to the cryoperstruction for the synsedimentary or postsedimentary rearrangement of covers under periglacial conditions. This includes the permissiveness of an additional vertical subdivision of the respective cover. In Germany soil mapping is an official task of federal and regional geological institutions (Landesämter respectively Bundesanstalt für Geowissenschaften und Rohstoffe). Their activities on this matter are subdued to official instructions (in German: Kartieranleitung) applying a vertical subdivision of the sub superficial range by “layers” (in German “Lagen”). The definition and differentiation of layers considers the process of cryotranslocation as well as several (but not all) sub processes of cryoperstruction whereas other sub processes sharing the cryoperstruction are not included by the definition of layers. In particular this lack concerns the sub processes of cryohomognisation and cryolithotropy. Moreover, the definition of layers does not deal with the processes and results of cryopedogenesis regardless of the frequent connection with consequences of cryoperstruction [l.e. of horizons and zones]. Frequently, not any of distinct types, principles, or criteria of profile subdivision is applicable. Consequently, no regional or spatial limitation of distinct periglacial phenomena are recognizable. One cannot distinguish regions and island positions dominated by the occurrence of periglacial covers from others dominated by the appearance of cryoperstruction zones. On the contrary the different processes and sub processes have been effective in complexity but with changing dominances. Therefore, uncoupling particular processes of periglacial surface modification is not senseful. The profile of soil substrate comprises considerably varying shares as of local components as of cryotranslocated accumulations. The diversity of possible combination depends mainly on local geological and geomorphological conditions as altitude, exposition, and relief energy as distance to ice sheet margins or areas of eolian accumulation. Analysing the sub superficial profile subdivision provides a detailed characterization of the substrate succession considering local and outside components as well as features of cryoperstruction. Moreover, required is an integrating and at the same time aggregating regionally comprehensive arrangement and characterization of periglacial profile differentiation. For this purpose the suitability of the current definition connected with the term “layer” (in German: “Lage”) is limited, for this definition does not comprise the complexity of sharing processes. This is the reason for the proposition of a new term providing neutrality with regard to profile subdivisions due to cryoperstruction, cryotranslocation and pedogenesis (cryohorizonts). Such term enables avoiding a misleading nomenclature. This proposal is related to the term “segment” (respectively “periglacial segment”) and clearly distinguishable not only from cover or zone but from “layer”, too, However, if furthermore the term “layer” should be desired also for future use, a complementary redefinition and renaming is required straighting that a completed term “layer” must comprise all possible profile subdivisions due to all the process systems. In comparison with the current definition of layers this completed redefinition is an enlargement of content, synonymous with the segment. A prerequisite of the further use respectively application of the term “layer” – completed – is the general acceptance of this enlargement with all consequences. The general characterization of segments respectively of layers according to the completed redefinition comprises processes and features resulting from periglacial environmental conditions in the pedosphere: i) Substrate supply by means of cryoclastics and cryotranslocation (including eolian accumulation as well as solifluction and rinsing) from the local material and varying allochthonous components; ii) Cryoperstruction (with destratification and homogenisation, cryolithotropy and cryoturbation); iii) Cryopedogenesis (precursors or even finalizing development of soil horizons). All sharing sub processes could participate in forming the pedosphere with various shares and during different periods of time. Due to the varying local conditions (paleorelief, inclination, shape, and exposition of slopes) and the distribution pattern of parent materials (rocks, loose sediments) as well as to allochthonous components arise differences determining the occurrence of segments respectively of layers according to the completed redefinition. These differences are reflected by substantial composition, stratification and structure as well as by the forming of soil horizons in the vertical succession of single segments (respectively layers according to the redefinition), but also by their horizontal extension. Their vertical sequence may be subdivided into the upper part (upper segment or upper layer), proved locally in the uplands, the main part (main segment or main layer), the middle part (upper and lower middle part), the basic part (occasionally distinguishable by means of composition, structural features and sometimes age of development). The consequent connection linking all the process systems effective under periglacial environmental conditions enables and provides a detailed, integrating and regionally comprehensive characterization of differentiations and subdivisions related to sub superficial substrates and soils by means of periglacial segments respectively also layers (but exclusively according to the completed redefinition).
>> Volltextversion (pdf 2.0 M; Heft 6-Aufsatz 1; Original paper; Language: Deutsch; urn:nbn:de:0041-afsv-00610)
Heft 9/2010
Heft 6/2008
