Jeszcze raz o płaszczowinie strażowskiej w Tatrach (artykuł dyskusyjny), cz. I

Zbigniew Kotański

Abstrakt


ONCE MORE ABOUT THE STRAZOV NAPPE IN THE TATRA MTS. (PT. I)

Summary
This is a polemic article, supporting and evolving the Author's view concerning existence of the upper subtatric (Strazov) nappe in the Western Tatra Mts (39-50). This view was questioned by some authors (M. Mahel 57, J. Gaździcki and A. Michalik 23, 62 and E. Passendorfer 73, 74). After detail discussion of many local tectonic, cartographic and lithologic questions, as well as some general paleogeographical and microfacies-environmental problems, following conclusions are formulated:
1. The presence of three tectonic units in lower part of the Chochołowska Valley is evident. These are: the lowermost Siwa Woda unit, belonging to the middle subtatric Choc nappe (Cierny Vah series), overthrusted by two higher units - Furkaska and Koryciska units, which belong to the upper subtatric Strazov nappe. The thrust surface of the Koryciska unit over the Siwa Woda unit is clearly discernible in the detail geological maps (33, 34, 39, 47, 58) and is easily recognisable in morphology. Therefore the considerations of "inverted superposition" of those units, based on the analysis of pebbles in Eocene conglomerates (62), are inessential.
2. The attempt of presentation of tectonics of the discussed are chaotically, as a gravitational megabreccia (24, 62), is not confirmed by detail mapping. Negation of existence of the above mentioned tectonic units, is in fact a backward tendency in tectonic investigations.
3. The upper subtatric (Strazov) nappe has been distinguished by D. Andrusov (3) in the Strazov Mts. on the basis of superposition of the Ladinian Wetterstein limestone and dolomite on the Choc Rhaetian and Hauptdolomit (exactly the same situation as in the Tatra Mts.). The main difference between these two series consists in the facial differentiation of Middle and Upper Triassic. The Choc series is a deeper-marine series composed of two lithostratigraphical formations - Reifling limestones and Lunz beds, whereas the main component of the Strazov series are Wetterstein limestones and dolomites. Hence, in the classical Andrusov's conception the differences between Choc and Strazov series are very clear. After some further investigations of M. Mahel (53-56), these differences became rather obliterated, particularly after creation by him the Bebrava unit (57) with transitional facies character. The situation became clear again in result of some recent field works (51) and environmental- dasycladacean studies (15), questioning the existence of Bebrava unit and attributing the dubious sequences again to the Strazov nappe (15). This is in fact the return to the classical conception of D. Andrusov (2, 5 - 9). In result of such development of paleogeographical and facial concepts, it is evident (with the Furkaska - Koryciska series with very thin Reifling limestone, but with good developed Partnach beds and with Ladinian-Carnian Wetterstein carbonate formation of enormous 2000 m thickness, but completely without the Lunz beds) is not Choc, but Strazov series.
4. In result of sonic new microfacies-sedimentological investigations, the new depositional model of Middle Triassic has been elaborated in the Eastern Alps (18, 19, 71, 72, 78, 89). The Fig. 1 presents the Wetterstein-Partnach formational couple. The same model was later applied to Internal Carpathians (Fig. 2). Northern carbonate platform is separated from the southern platform (North-Gemer and Strazov) by basinal Choc sediments. Partnach beds are the basinal equivalent of the recifal-lagoonal Wetterstein formation, both of them being connected with the southern platform, but not with the deeper Choc zone.
5. The Wetterstein formation is a main component of the southern carbonate platform, which was composed of two main types of sediments - reef and back-reef lagoon sediments. Both of them are represented in the Wetterstein dolomite in the Western Tatra. The attribution of the reef character to Wetterstein limestone and of the lagoonal character to Wetterstein dolomite (62) is not adequate, because the both types of rocks may be recifal or lagoonal (Fig. 3), what should be checked by microfacies studies. Therefore the degree of primary or secondary dolomitization should not be the deciding argument for attribution of studied sequences to Choc or Strazov series.
6. The only criterion of paleogeographical-facies zonation should be then the right palinspastic reconstruction, presenting distribution of Middle Triassic carbonate platforms and separating basins (Fig. 2). Accordingly to such a concept Furkaska- Koryciska series with strongly dominating Wetterstein-Partnach formational couple belongs surely to the southern carbonate platform. The great thickness of Wetterstein dolomite may be explained by synsedimentary subsidence (Fig. 4).
The Author is readily disposed to initiation of common field work in this difficult terrain and resolution of all disputable questions after definition of some basic conceptions and acceptation of some common point of departure.

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