Główne etapy ewolucji geologicznej zachodniej Tetydy - zarys problematyki

Józef Wieczorek

Abstract


W ewolucji medyterańskiego sektora Zachodniej Tetydy wyróżniono trzy zasadnicze etapy: przedoceaniczny (później perm - wczesna jura), oceaniczny (środkowa jura - środkowa kreda) i etap zamykania Tetydy (środkowa kreda - paleogen). Medyterańska część Tetydy w sensie paleogeograficznym nie była oceanem. Region ten pozostawał pod wpływem lateralnych ruchów Afryki względem Europy i w jego historii znaczną rolę odgrywały ruchy przesuwcze. Główne etapy ewolucji Tetydy można odczytać w rozwoju polskiej części Karpat, szczególnie Tatr.

MAIN PHASES OF THE GEOLOGICAL EVOLUTION OF THE WESTERN TETHYS -AN OUTLINE

he western part of the Tethys can be subdivided three basins - Mediterranean, Atlantic and Caribbean ones. The boundary between western and eastern parts of the Tethys is conventionally accepted along the Vardar zone.

Three main phases are recognizable in the evolution of the Mediterranean basin - "pre-oceanic" (Late Permian) - Early Jurassic), "oceanic" (Middle Jurassic - Middle Cretaceous) and the closing period of the Tethys (Middle Cretaceous - Paleogene). The above part of the Tethys was formed due to lateral movements of African and Eurasian. plates which were related with several phases of the Atlantic Ocean evolution. In this basin strike-slip movements were of particular importance. The Mediterranean basin of the Tethys was spread mainly on the thinned continental crust. Three belts of the oceanic crust (Ligurian-Piedmontian, Muresz and Vardar) did not reach considerable wideness and were for-med during about 60 mIn years. From the paleogeographic point of view the Mediterranean part of the Tethys was never a real ocean.

During the "pre-oceanic" phase the basin spread westward. Rifting took place in the Middle Triassic and its results are recognizable in the Polish Tatra Mts., too (layers from Reining and Partnach in the Furkaska - Koryciska scale reflect the Early Jurassic a broad carbonate platform existed in the Mediterranean Tethys. The terrigenous facies existed at the margins as on be observed in High-Tatric and Sub-Tatric sequences in the Tatra Mts.

The evolution of the oceanic crust belts in the western Tethys took place during Jurassic and Early Cretaceous. The Ligurian-Piemonlain "ocean" was connected with the Atlantic part of the Tethys along the transform fault Maghreb-Sicily. Between the European margin and the north edge of Adria (Apulia) a fault system is proposed as well. Manifestations of mobility (appearance of intra-basin ridges, changes of their activity and position and scarcity of oceanic crust records indicate the Carpathian flysch basin to be developed in the area of strike-slip faulting. The Cieszyn basin pull-apart in character developed at the end of Jurassic.

Beginning from the Middle Jurassic tension prevailed and caused the sub-division of the Mediterranean Tethys into basins of deep ocean sedimentation (rosso amonitico, radiolarites, maiolica) and uplifts of shallow water carbonate sedimentation. This differentiation can be followed in corresponding deposits of Tatra and Pieniny Mts. Middle Jurassic neptunian dikes found in High-Tatric sequence of the Tatra Mts are related to the same movements.

From the Middle Cretaceous (or earlier in some other basins) the compression movements began to prevail and eliminated the oceanic crust belts. During this phase in the Flysch Carpathians tectonic movements periodically intensified in the Middle Cretaceous Turonian, Campanian, Eocene-Oligocene and Miocene.


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