Ewolucja basenu niecki miechowskiej w jurze jako rezultat regionalnych przemian tektonicznych

Zbigniew Złonkiewicz


Evolution of the Miechów Depression basin in the Jurassic as a result of regional tectonical changes.
S u m m a r y. Evolution of a sedimentary basin in the Miechów Depression (MD) during the Jurassic was due to the synsedimentary tectonic activity of the Caledonian–Variscan structures. There was a local zone of maximal subsidence extending NW–SE in its area. The Włoszczowa Massif (WM) in the basement of the Permian-Mesozoic cover in central and NW part of theMD was an element of a little lesser subsidence in comparison to the adjacent NW and SE areas. A narrow graben in the Lasocin–Strzelce Dislocation Zone separated it from the Holy Cross Mts. Block (HCM). The Mid-Polish Trough invaded the MD from the NW. The edge of WM (Pilica Fault) limited a reach of the pre-Bathonian SE ingressions. In addition, transgression from an inland basin (from SE) developed since the Bathonian. Grabens and horsts elongated NNW–SSE were formed in the central part of MD. They continued further S-wards beyond the edge of the Carpathians. In the Callovian and Late Jurassic facial zones in the central and NW part of the MD were elongated NW–SE.
The zone of major subsidence was located between Pągów and Kostki Małe and stretched further SE into the basin of the Carpathian Foreland. During the Late Oxfordian and Kimmeridgian the shallowest zone of the basin SW to the HCM was located in the N part of the WM. Structures formed in the MD area pointed at an oblique extension directed to NW. It was effected by palaeostress directed to NW, stronger in the NW part of the area and gradualy decreasing. The stress reactivated two oblique-slip fault systems: Kraków–Lubliniec and Lasocin–Strzelce. Also an increasing tension to W, stronger in its S part, might be recognized. It activated the Zawiercie Fault in the Late Bajocian and caused left-slip rotation of the WM in the Late Oxfordian. The tectonic model controlling sedimentation during the Latest Jurassic and Early Cretaceous was very similar to the pattern of subsiding and elevating zones formed in this area during Variscan compression. The Mid-Polish Trough was formed by dextral extension and reactivation of dislocations parallel to the edge of the East European Craton. The consolidated HCM-block belonged to a zone of elevated blocks, characteristic for the axial part of an extension basin.

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