Współczesny transport i sedymentacja żwirów w dolinie Dunajca (stresz. Referatu)
Abstract
The transportation and sedimentation of the conterporay gravels in the Dunajec River Valley
The studies have been made alongside the Dunajec river valley on the variability of the maximal size of granite blocks and pebbles, the variability of the petrographic composition of the gravel, the degree of roundness and sphericity of the granite pebbles and the dependance of the orientation of pebbles upon their shape and size. Comparing the plots of variability of the maximal sizes of the granite blocks and pebbles with the variability calculated from Sternberg’s Law the sectors of the valley in which the selective transportation and accumulation of gravels takes place have been determined. The variability of the petrographic composition of gravel is due to different causes in various sectors of the river. In the upper course the mechanical abrasion eliminates the pebbles of limestones, marls and other soft rocks, while in the lower course the chemical weathering of granite pebbles causes a relative increase of quarzite pebbles in the gravel. The degree of roundness and sphericity of pebbles after the initial increase in the upper course of the rive r decreases in its lower course. It has been shown that this is caused by the selection of pebbles on the basis of shape during transportation. This selection takes place earlier than the selection on the basis of the size of pebbles. The orientation of pebbles, depends upon their shape and size. On the basis of th a t dependence the course of the deposition of gravels has been reproduced. For the determination of the transportation direction of the fossil river gravels the measurements of the orientation of pebbles are of the greatest importance. At planning and interpreting of such measurements the differences in behaviour of pebbles of various size and shape should be taken under consideration.
The studies have been made alongside the Dunajec river valley on the variability of the maximal size of granite blocks and pebbles, the variability of the petrographic composition of the gravel, the degree of roundness and sphericity of the granite pebbles and the dependance of the orientation of pebbles upon their shape and size. Comparing the plots of variability of the maximal sizes of the granite blocks and pebbles with the variability calculated from Sternberg’s Law the sectors of the valley in which the selective transportation and accumulation of gravels takes place have been determined. The variability of the petrographic composition of gravel is due to different causes in various sectors of the river. In the upper course the mechanical abrasion eliminates the pebbles of limestones, marls and other soft rocks, while in the lower course the chemical weathering of granite pebbles causes a relative increase of quarzite pebbles in the gravel. The degree of roundness and sphericity of pebbles after the initial increase in the upper course of the rive r decreases in its lower course. It has been shown that this is caused by the selection of pebbles on the basis of shape during transportation. This selection takes place earlier than the selection on the basis of the size of pebbles. The orientation of pebbles, depends upon their shape and size. On the basis of th a t dependence the course of the deposition of gravels has been reproduced. For the determination of the transportation direction of the fossil river gravels the measurements of the orientation of pebbles are of the greatest importance. At planning and interpreting of such measurements the differences in behaviour of pebbles of various size and shape should be taken under consideration.