Młode ruchy tektoniczne a morfologia Pienin

Abstract

Young tectonic movements and morphology of the Pieniny Mts. (Polish western Carpathians) The author attempts to reconstruct the Neogene and Quaternary pajaeogeography of the Pieniny Mts. and the eastern part of the Nowy Targ Basin. Analyses of remaining fragments of planation surfaces as well as long-profiles of Quaternary river terraces (rock socles) allow the measurement of the intensity of young tectonic movements (tables 1, 2). The detailed geomorphological map on a scale of 1:10 000 of the Dunajec river valley and its tributaries between Dębno and Krościenko was prepared. Particular attention was payed to the structure of river terraces (cf. fig. 3, table 3). The analysis of terrace levels was carried out on the basis of 110 cross-section s of the Dunajec valley. The amount of dissection of the Quaternary river terraces socles as well as disturbances in their longitudinal profiles were taken as a measure of differentiated tectonic movements (fig. 2, table 4). The detailed investigations of terrace covers (pétrographic composition, degree of weathering, pebbles orientation, etc.) allowed the correlation of terraces and the description of their relation to solifluction covers made possible. Within the area under investigation there occur remains of three planation surfaces: the intermontane level (270—440 m), formed during the Pannonian, the foot-hills level (150—240 m), formed during the Romanian and the river-side level (90—150 m), formed in the early Quaternary period. The Lubań — Radziejowa range belongs to the most strongly uplifted zones (Middle Pliocene — Early Quaternary). This uplift was accompanied by the subsidence of the Krośnica river valley. The uplift during the Rhone phase reached following values: 400 m in the Lubań range, 115—120 m in the Spiskie Pieniny Mts. and 100—205 m in the Pieniny Mts. The rate of uplift during the Valachian phase was weaker: 90—135 m in the Lubań — Radziejowa range, 70—120 m in the Spiskie Pieniny Mts. and only 30—70 m within the Pieniny Mts. During the Early Quaternary period the approximate rate of uplift of the Pieniny Mts. Teached 60— 70 m. The Pliocene deposits occurring at the foot of the Lubań range were redeposited from the previously higher situated sites (within the Foot-Hills level) as a result of tectonic movements which lowered the contact zone between the Pieniny Klippen Belt and the Magura nappe. The important role played also solifluction processes which occurred during the last glaciation. The antecedent Pieniny and Niedzica water gaps were formed mainly in the earliest Quaternary and were finally deepened in the Pleistocene. Several factors were involved in the formation of these gaps. Differences in the rock resistance, differentiated block-type tectonic movements during the Late Pliocene and Early Quaternary, the plio-pleistocene actvity of the Peripieninian deep crustal fracture, large transversal depressions of the Pieniny Klippen Belt and accompanied dislocation zones, which can be seen on the satellite fotographs belong to them. The total amount of the Quaternary uplift of the Pieniny Mts. is from 100 m in the western to 150 m in the eastern part. On the basis of analyses of the Quaternary river terraces, especially rock socles, as well as the differences in thickness of alluvial covers, three regions showing different tectonic pattern have been distinguished: a) the Dębno — Frydman Graben. This graben, formed during the Early Quaternary, underwent downward movements lasting to the present day. Its depth reaches 150 m. b) the Pieniny Mts., which were uplifted during the Pleistocene by block-type movements. The amount of uplift after the South-Polish Glaciation reached 50—85 m. The surroundings of the Pieniny water gap and the eastern margin of the Nowy Targ Basin were more strongly uplifted than the area between Czorsztyn and Sromowce Niżne. Small disturbances in terrace socles visible on longitudinal profiles are connected with the presence of large dislocation zones, orientated NNW—SSE which cross the Dunajec valley. The rate of uplift was relatively stable (table 4). During the youngest Holocene, the eastern part of the Pieniny Mts. (Sromowce Niżne — Kras) seemed to be slightly uplifted. The western part, however, was stable or weakly depressed. c) the Krościenko Basin. In regard to the Pieniny Klippen Belt and the Beskid Sądecki range the rate of uplift was here much slower. During the Late Glacial downward tectonic movements began to dominate. These processes were continued in the Holocene. The Krościenko Basin and the Dębno — Frydman Graben are located in the zone of subsidence which is connected with the contact zone between the Pieniny Klippen Belt and the Magura nappe. The northern and southern margins of the Nowy Targ Basin were uplifted in the early Pleistocene with the same intensity. These movements began to differentiate in the Late Pleistocene. Since then, the Lubań range has revealed the relatively faster uplift.