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Palaeotectonics of the area of Miechów Depression in the Jurassic in relation to the SE segment of the Mid-Polish Trough

Złonkiewicz Z.

Volumina Jurassica

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2006

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Vol. 4, no. 1

70-71

EN

Structures reactivated in the basement of the Permian-Mesozoic cover (Fig. 1A) controlled development of the SE segment of Mid-Polish Trough. Facies and thickness patterns in the area of the Laramide Miechów Depression (Złonkiewicz 2006a, b) and adjacent areas verify and complete thesis of analog modeling (McClay et al. 2002; Gutowski & Koyi 2005). They indicate an oblique extension changing from NW to WNW. The NW component affected earlier and stronger the NW part of the area. It caused transtension in reactivated fault systems: the Kraków-Lubliniec (KLF) and Lasocin-Strzelce Dislocation zones (LSDZ). Also an increasing westward tension, earlier and stronger in southern part, may be recognized. Stages of development: I. Hettangian-Bajocian - dextral tension and post-Variscan relaxations. Strike-slip activity of the KLF and LSDZ. The NW- directed stress component down-threw the NW sides of the normal faults: Opoczno-Grójec Fault and the Pilica Fault, rejuvenated on the edge of the Włoszczowa Massif. A slight westward component and relaxations formed a pull-apart rhomboedric system of basins and horsts in down-thrown sides and extended a graben or isolated basin in the LSDZ. II. Bathonian - dextral oblique extension. Dominant stress, directed to NW, supported KLF and LSDZ slip. The coincidence with an increasing westward stress, stronger in the S part, activated a system of en echelone splay faults (strike W-E), posthumous to the Zawiercie Fault (ZF). A second-order system of splay faults (mostly NNW-SSE), bound to ZF, was formed in the Włoszczowa Massif area, leading to formation of grabens and horsts. That pattern was repeated further to the S at the Carpathian front. A basin (W-E) extended at the S border of the Włoszczowa Massif. III. Callovian-Kimmeridgian up to the Hypselocyclum Chron - dextral oblique extension. Increasing westward stress resulted in pull-apart activity and changed a rhombohedric system of horsts and grabens into elongated NW-SE structures. The westward component was stronger in the S part, which resulted in left-hand rotation of the Włoszczowa Massif. The regional uplift, regression and local emersion rebuilt the late-Variscan pattern; an up-thrown Włoszczowa Massif and down-thrown adjacent NW and SE areas. IV. Kimmeridgian from the Divisum Chron onwards-Valanginian - continuation of the palaeotectonic pattern, with dominating westward stress component. Transgression-regression cycle. Extension of the pull-apart structures in the S part of an area. Evolution of the Mid-Polish Trough, extending in front of the East European Craton, depended on varying stress components, produced by extension of rifts in N proto-Atlantic and W Tethys. Palaeotectonic development locates the area of the Miechów Depression between the elevated: Upper Silesian Massif and Holy Cross Mts. (HCM). The HCM belonged to the zone of elevated elements (Gorzów Block, Wielkopolska Ridge, Piotrków Block, Upper San Anticlinorium), typical for the axial part of a basin, separating parallel zones of maximal subsidence. The subsiding zones in the SE segment of the Mid-Polish Trough were located parallel to the edges of HCM (Fig. 1B) in rejuvenated Permian grabens. Observed palaeostress activated a right-hand transfer fault in the deep structure of the Holy Cross Dislocation and formed a positive flower structure in the HCM area.

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Palaeogeography of the NW and central part of the Miechów Depression during the Jurassic as a result of the palaeotectonics development

Złonkiewicz Z.

Volumina Jurassica

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2006

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Vol. 4, no. 1

72-72

EN

The Variscan movements elevated mountain ranges and uplands, forming vast massifs along the East European Craton. The structurally complicated Małopolska Massif was located in SE Poland. In the Jurassic the area corresponding to the Laramide Miechów Depression was located on the SW periphery of the Mid-Polish Trough and N periphery of the Tethys. The palaeogeographic development of the area of study was affected by reactivation of Caledonian-Variscan structures in the pre-Permian basement. It may be detected the influence of the Włoszczowa Massif (NW part of the Małopolska M.) as an area of a lesser subsidence. The Pilica Fault (on the NW Włoszczowa Massif edge) limited the pre-Bathonian transgressions to the SE part of the area of study. Also a narrow gulf/graben or isolated basin was temporarily formed in the Lasocin-Strzelce Dislocation Zone at the border of the Holy Cross Mts. and the area of study. Alluvial, deltaic and lagoonal to medium siliciclastic shelf sediments were deposited. Since the Bajocian an inland basin, elongated W-E, was formed parallel to the S border of the Włoszczowa Massif and in the Bathonian an ingression from SE began. Narrow gulfs/grabens and submarine ridges/horsts NNW-SSE elongated formed in the central part of the area of study. They continued further southwards up to the present edge of the Carpathians. By the end of the Middle Jurassic, lagoonal to distal siliciclastic shelf deposits corresponded to several transgression-regression cycles, interrupted by local erosion. The marine deposits of an open carbonate shelf of the Callovian - Early Kimmeridgian cycle covered the area of study and a local zone of maximal subsidence in the Jurassic was formed. The facies zones of various sponge-detrital deposits, mudstones and marls in its NW and central part were elongated NW-SE, and in the SE part they changed their direction to WNW-ESE. The fractioned Włoszczowa Massif subsided within grabens in the extending Lasocin-Strzelce Dislocation Z. The local subsidence zone, crossed the Włoszczowa Massif. It penetrated and deepened further in SE directionin the basin of Carpathian Foreland. The Late Oxfordian and Early Kimmeridgian regression resulted in temporal formation of a shallow water carbonate platform. It passed over the Mid-Polish Trough, migrating southwards, and the fine-grained shoal deposits and oolitic barriers reached, but did not crossed, the area of study. The shallowest facies of the platform, located SW to the Holy Cross Mts., was underlain by the northern element of the Włoszczowa Massif. A narrow zone of deeper marly facies, still preserved, split the carbonate platform. That pattern might be detected also in deposition of marls and lumachelles of the following transgression, which commenced in the Kimmeridgian between the Hypselocyclum and Divisum chrons.

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Ewolucja basenu niecki miechowskiej w jurze jako rezultat regionalnych przemian tektonicznych

Złonkiewicz Z.

Przegląd Geologiczny

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2006

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Vol. 54, nr 6

534-540

EN

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 basinSWto theHCMwas located in theNpart 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.