Outline of tectonics of the outer zone,the Carpathian foretrough |
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| Abstract: | The edge trough in the East Carpathians includes an inner zone that developed adjacent to the Carpathian geosyncline, a deep trough filled with thick Miocene and Pliocene sediments. The Miocene beds have been extensively folded and overthrust. The edge trough also includes an outer zone which is the depressed edge of the platform covered by Tortonian and Sarmatian sediments. The structure and geologic history of the platform part of this trough is based on much borehole data and detailed geologic and geophysical surveys. The stratigraphy is discussed and thicknesses of the Tortonian and lower Sarmatian for different localities are given in Table 1. Figure 1 shows the structure of the outer zone; contours are drawn on top of the Tiras (gypsum-anhydrite) formation. Several zones of rapidly varying thickness in the Tortonian and lower Sarmatian sediments correspond to major northwest striking basement faults, which are responsible for the block structure of much of the outer zone. These basement faults, first demonstrated by geophysics and then examined in numerous boreholes, show that the dip of lower Sarmatian and Tortonian rocks increases with depth from about 10-15° up to 35-45°. Gentle flexures in upper horizons become larger downwards and pass into downfaults. Movements occurred during deposition. Figure 2 gives geologic sections showing faults in the outer zone. All dislocations form a definite fault system oriented obliquely with respect to the main strike of the Alpine tectonic elements. There are frequent signs of tectonic movements throughout the Miocene.—W.D. Lowry |
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