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2 1998

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Tectonics of the consolidated basement of the Polish Carpathians

Ryłko W., Tomaś A.

Przegląd Geologiczny

1998

Vol. 46, nr 8/2

758-762

Based on the results ofmagnetotelluric soundings a sketch of the main tectonic elements of the consolidated basement of the Polish Flysch Carpathians and a number of longitudinal profiles and cross-sections have been drawn. The sketch as well as the sections allowed for developing a concept about major tectonic pattern of the consolidated basement in this part of the Carpathians. Morphology of the consolidated basement surface of the Carpathians is very diversified. Depth to the top of the basement surface varies from several hundred meters in the western part of the Carpathians to around 20 km in the south-eastern part. Generally, the surface drops from the north-west toward the south-east. The drop is not uniform, and it has a discontinuous character. In the tectonics of the consolidated basement of the Carpathians, in the territory of Poland, three major elements influencing its structure are distinguished. These are two transverse, generally SW-NE oriented fault zones (A-A and B-B), where the basement is dipping eastward. The third element, of a comparable meaning to the other two, is a longitudinal zone of the basement dipping southward - " regional basement slope ". The first of these large fault zones, the transverse and western-most one (A-A), runs from Babia Góra to the region ofRzeszotary. The dislocated area lying to south-east of the fault zone is lowered by about 8.5 km in its southern part and about 2 km in its northern part. The second, transverse B-B fault zone follows the Wysowa-Sedziszów Małopolski line. The dislocated area lying to the east of this fault zone is lowered by several kilometers to maximum of 12 km in the southern part. The entire eastern block is moved along the fault 40 km to the north. The B-B zone separates the central block from the eastern one. The third major tectonic element is the described earlier zone of the regional basement slope (Fig. 2). It is a longitudinal element which remodels the consolidated basement of the Carpathians in the southern direction. Along this zone, there is an abrupt block-wise lowering of the consolidated basement to the south. The two transverse dislocation zone A-A and B-B, discussed earlier, divide the consolidated basement of the Polish Carpathians into three regions. The western region located to the west of the A-A zone, the central region between the A-A and B-B zones, and eastern region located to the east of the last zone (B-B). The consolidated basement of the western region is relatively shallow, at the depth from one to four kilometers. This region is technically calm. The central and eastern blocks are two-fold, separated by the regional basement slope into the elevated northern part and lowered southern part. An outlined general framework of the tectonics of the consolidated basement of the Polish Carpathians is a present-day representation, yet it was finally formed in the Neogene. We can assume that in the Early Neogene (probably at the turn of the Oligocene and Miocene) the northern plate collided with the Carpathian block. In the Lower Miocene, along the boundary between the northern plate and the Carpathian block, the latter was dropped from a few kilometers in the west to several kilometers in the east. After the lower Miocene, probably at the Middle/Upper Miocene interface, the Carpathian block started to disjoin. It was fractured along the A-A zone and, in its eastern part, rotationally shifted by about 40 km to the north-east. In the west, the western block was formed. The eastern part, apart from being shifted and rotated, was additionally lowered by a few kilometers towards the south. In the Upper Miocene a fracture along the B-B zone took place, and, as in the previous stage, the eastern part was rotationally transferred by ca 40 km to the north-east. Thus, the net shift, along the A-A and B-B line was about 80 km. The eastern part was divided along the B-B line into the central and eastern blocks. The eastern block, moreover, is lowered by a few kilometers to the south. This process is accompanied by a development of a set of oblique slip faults of various directions.

Paleoecology and organie matter in the Late Badenian and Early Sarmatian marine basin of the Polish part of the Carpathian Foredeep

Czepiec I., Kotarba M.J.

Przegląd Geologiczny

1998

Vol. 46, nr 8/2

732-736

The studies aim to determine both the ecological and geochemical conditions of the Late Badenian and Early Sarmatian sedimentary basin located in the outer part of the Carpathian Foredeep. Particularly interesting are: depositional environment of organic matter, depth of the basin and water temperatures. The Late Badenian sea was presumably only slightly deeper than the outer shelf i.e. about 200 meters. The warm climate resembling that of the warm temperate zone resulted in surface water temperatures 17-20' C. In the Sarmatian the sea depth was initially about 30-50 meters thus, the existence of submarine meadows was inferred. Then, progressing shallowing to about 10 meters took place. The Sarmatian sea was a warm basin with temperatures roughly corresponding to those of the Late Badenian ones. Organic matter deposited during both the Badenian and the Sarmatian reveals terrestrial origin. Organic matter in the Late Badenian and Early Sarmatian strata is immature or, at most, early matured but at depth below 3000 meters. Very low correlation of both the concentrations and the maturation degree of the organic matter with its depth of occurrence suggest the similarity of sedimentary environments in the whole Miocene succession and the lack of thermal transformation after deposition. Almost exclusive occurrence of the humic organic matter points to the fast and rhythmic supply of terrestrial clay matter to the deltaic environments in the shallow Miocene basin. A rapid sedimentation of terrestrial, deltaic sediments took place in the Miocene basin, therefore the humic organic matter (type III kerogen) prevailed there and the marine type II kerogen was hardly detectable.