„Wielkoskalowe" różnice poglądów i interpretacji, odpowiedź
Abstract
„LARGE-SCALE" DIFFERENCES IN POINTS OF VIEW AND INTERPRETATIONS; REPLY
Summary
In critical analysis of our papers (1, 12 and possibly 13), J. Znosko (21) groundlessly treats us as authors of the hypothesis of strike-slip movements along SW margin of the East-European Platform, widely discussed in the literature for almost ten years. We agree with J. Znosko that there exist fundamental differences in character of the basement at opposite sides of contact zone of the platform, differing in their explanations. According to one interpretation put forward by J. Znosko, the differences are due to passing the Curie point by crystalline basement rocks occurring south-west of the East-European Platform, and according to the other (not treated as an alternative in that paper, 21) - due to subduction along SW margin of the platform in the course of the Caledonian orogeny. The hypotheses fail to give support in the available geophysical and geological data.
We agree with J. Znosko that there is still no evidence for overthrusts in the circum-Fennosarmatian Caledonides but we have to treat comparison of Central European sector of the Caledonian Deformation Front to front of overthrust in the Eastern Carpathians and other foldbelts as misinterpretation. The leaning of the front of Carpathian overthrusts against the margin of the East-European craton should be rather treated as an example of influence of deep structure of the basement on extent of the overthrusts. In turn, the Caledonian Deformation Front coincides with marginal fractures of the East-European Platform which would correspond to a collisional or internal suture if any collision took place in that area in the Late Paleozoic. The lack of any disturbances in marginal part of the platform speaks against such collision. That is why we cannot agree with interpretation of the sections through marginal part of the platform (1, fig. 2), presented by J. Znosko (21 ), as the sections show completely undeformed Lower Paleozoic sedimentary cover and basement in marginal part of the platform.
Remarks on virgation as a common phenomenon (21) do not match the case of Y-shape of Dalslandian, Caledonian and Variscan foldbelts in the North Atlantic region (22). If we accept origin of foldbelts in result of the Wilson cycle, we would have to assume repeated opening and closing of oceans in individual arms of that Y-shaped structure from about 1,500 m.y. ago till the Permian. That is why Zwart and Dornsiepen regarded as necessary to postulate the existence of triple junction, and we - cutting off and translocation of a fragment of Caledonian foldbelt along with its Dalslandian and Caledonian basement and, in this way, secondary nature of the Y-shaped structure.
J. Znosko (21) is actually right in questioning post- Grampian spreading in the Appalachian sector of the Protoatlantic, accepted in our earlier paper (1) after one of authors.
In recalling discussion following presentation of our paper at the Geodynamic Session at Jabłonna in 1981, J. Znosko (21) stated that "some remarks of participants were of fundamental value and it could seem that they will be taken into account and carefully analysed by the authors". It is impossible not to agree with that, similarly as with the statement of someone else that two sides are needed for discussion.
Finally, we would like to excuse to the Readers for delay in replying to J. Znosko and R. Dadlez. However, the delay was unevitable as the Authors did not agree to render their manuscripts accessible early enough to make possible publishing the replies in the same issues of this journal.
Summary
In critical analysis of our papers (1, 12 and possibly 13), J. Znosko (21) groundlessly treats us as authors of the hypothesis of strike-slip movements along SW margin of the East-European Platform, widely discussed in the literature for almost ten years. We agree with J. Znosko that there exist fundamental differences in character of the basement at opposite sides of contact zone of the platform, differing in their explanations. According to one interpretation put forward by J. Znosko, the differences are due to passing the Curie point by crystalline basement rocks occurring south-west of the East-European Platform, and according to the other (not treated as an alternative in that paper, 21) - due to subduction along SW margin of the platform in the course of the Caledonian orogeny. The hypotheses fail to give support in the available geophysical and geological data.
We agree with J. Znosko that there is still no evidence for overthrusts in the circum-Fennosarmatian Caledonides but we have to treat comparison of Central European sector of the Caledonian Deformation Front to front of overthrust in the Eastern Carpathians and other foldbelts as misinterpretation. The leaning of the front of Carpathian overthrusts against the margin of the East-European craton should be rather treated as an example of influence of deep structure of the basement on extent of the overthrusts. In turn, the Caledonian Deformation Front coincides with marginal fractures of the East-European Platform which would correspond to a collisional or internal suture if any collision took place in that area in the Late Paleozoic. The lack of any disturbances in marginal part of the platform speaks against such collision. That is why we cannot agree with interpretation of the sections through marginal part of the platform (1, fig. 2), presented by J. Znosko (21 ), as the sections show completely undeformed Lower Paleozoic sedimentary cover and basement in marginal part of the platform.
Remarks on virgation as a common phenomenon (21) do not match the case of Y-shape of Dalslandian, Caledonian and Variscan foldbelts in the North Atlantic region (22). If we accept origin of foldbelts in result of the Wilson cycle, we would have to assume repeated opening and closing of oceans in individual arms of that Y-shaped structure from about 1,500 m.y. ago till the Permian. That is why Zwart and Dornsiepen regarded as necessary to postulate the existence of triple junction, and we - cutting off and translocation of a fragment of Caledonian foldbelt along with its Dalslandian and Caledonian basement and, in this way, secondary nature of the Y-shaped structure.
J. Znosko (21) is actually right in questioning post- Grampian spreading in the Appalachian sector of the Protoatlantic, accepted in our earlier paper (1) after one of authors.
In recalling discussion following presentation of our paper at the Geodynamic Session at Jabłonna in 1981, J. Znosko (21) stated that "some remarks of participants were of fundamental value and it could seem that they will be taken into account and carefully analysed by the authors". It is impossible not to agree with that, similarly as with the statement of someone else that two sides are needed for discussion.
Finally, we would like to excuse to the Readers for delay in replying to J. Znosko and R. Dadlez. However, the delay was unevitable as the Authors did not agree to render their manuscripts accessible early enough to make possible publishing the replies in the same issues of this journal.