Wpływ rzeźby podłoża na dynamikę ruchu lądolodu zlodowacenia środkowopolskiego w północno-wschodniej części Gór Świętokrzyskich

Abstract

Influence on the morphology of fundament on the Dynamics of movement of the ice-sheet during the Middle Polish Glaciation in the north-eastern part of the Holy Cross Mts Considerable amount of local material in gravels of the frontal moraines of the Middle Polish Glaciation (Riss), occuring on NE slopes of the Holy Cross Mts., dearly indicates a considerable exaration activity of ice-sheet enforced to overpass still higher elevations at its foreground. Parallel distribution of geological units of the fundament, displaying NW-SE strike, was favouring subsequent incorporation into transgressing ice-sheet still lithologically varying types of rocks (fig. 1). Basing on the analysis of percentage content of individual local rock types in morainic gravels it was possible to determine the regional varia bility of local boulder content, their fields of scatter, direction of transport as well as mechanism governing the scatter of both (local and Scandinavian material. The fields of scatter of boulders of local rocks (fig. 2) are distributed exclusively south-westwards from the outcrops of parental rocks, clearly indicating the only one direction of ice-sheet movement from NE to SW. The boulders of Cretaceous rocks form several separated fields of scatter indicating depressions where existed the possibility of free advance of ice. The comparatively high Upper Jurassic elevations Were considerably impeding or even hindering further transport of Cretaceous boulders. As follows from the distribution of Upper Jurassic rock boulders they are coming just from these elevations. These both groups of boulders were transported in the same direction but along different ways. Consequently only sometimes the marginal parts of their scatter fields are mutually overlapping. Scandinavian, boulders occur in all the morainic gravels. Their amount varies from 5 to 95 percent, forming larger local accumulations. The distribution of Scandinavian rocks is much less dependent on the elements of the morphology of basement. However, if we take into account that the boulders were occurring not only in the lowest layers of the ice-sheet, the influence of morphology of the fundament on the direction of transport could not be so considerable. Numerous elevations occuring in this region caused frequent detachment of lower parts of the ice-sheet containing local material. Such detached lobes of ice were left at foot of higher elevations, forming inclined planes facilitating the movement of upper parts of „pure” ice containing exclusively Scandinavian material. These upper parts after gaining the contact with the basement were again enriched in local material. The latter was, however, different from that left at the foot of hindering elevation. Such situation was repeated several times until the north-eastern slopes of the Holy Cross Mts were completely covered with ice. During the final stages the process of overthrusting otf the ice-sheet over the dead ice was probably repeated several times resulting in additional enrichment of some moraines in Scandinavian material.