Basen dinantu w okolicach Krakowa - próba syntezy

Mariusz Paszkowski

Abstrakt


DINANTIAN BASIN IN THE CRACOW AREA: AN ATTEMPT OF A SYNTHESIS

Summary
The Dinantian sedimentary basin of Cracow area (S Poland) developed on the fragment of older, epicaledonian platform and formed the E shelf of Moravia-Silesia geosyncline (E closure of terminal part of Rhenohercynian Zone). Geotectonic framework of this area was formed during Dinantian by successive fragmentation of this relatively stable shelf. It was occupied during Devonian by carbonate platforms.
System of synsedimentary active blocks was developed as a result of desintegration of carbonate platforms. Their relative movements controlled facies distribution in basin. Closing of pull-apart type Moravia-Silesia basin by horizontal movements of lithospheric blocks along Elbe and Cracow- Hamburg lineaments created orogen and related greywacke flysch trough/foredeep basin. Eastward migration of maximal subsidence axis and area of immature clastic sedimentation during Dinantian caused onlap of Culm facies on all the other types of sediments. Relatively big and stable blocks were occupied by carbonate platforms or emerged. Quickly drowned blocks or fragments of tilted blocks were occupied by starved basins.
The main part of the shelf formed a kind of "basin and range province" i.e. system of tilted blocks. Small ephemeral carbonate platforms, frequently emerged or drowned occupied elevations. Network of basins among those platforms was situated on the drowned parts of tilted blocks. Basins were filled with pure pelagic sediments of starved type, but usually typical basinal deposits interfingered with allodapic limestones or carbonate debris flows, which derived from intrabasinal highs. Eustatically controlled events enable interregional correlation of successions both on carbonate platforms and in basins. The rise of sea level caused anoxic events in basinal areas indicated by deposition of unbioturbated black shales and cherts with phosphatic nodules, without bentos. This phenomena are known from crenulata, anchoralis and Upper Visean time and connected with disappearance of allodaps and partial drowning of carbonate platform. The fall of sea-level caused deposition of lighter, bioturbated pelites and spreading of allodapic limestones. This was manifested on the platforms (Fig. 3) as episodes of emersions and evaporite deposition during Middle/Upper Tournaisian and Lower/Middle Visean.

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