Kaledonidy środkowej Europy - orogenem przesuwczym złożonym z terranów

Władysław Pożaryski

Abstrakt


THE MIDDLE EUROPE CALEDONIDES - WRENCHING OROGENY COMPOSED OF TERRANES

Summary
The North German-Polish Caledonides belt lays between Variscian orogen and margin of the Easteuropean platform. W. Brochwicz-Lewiński, W. Pożaryski, H. Tomczyk (5, 6) in 1981 advanced an opinion that this orogen had formed in result of giant Silurian wrenching. The wrench movement detached the SW part of lithosphere under Middle Europe, forming the Easteuropean platform, and pushed it far to SE in recent Alpine area. The blocks detached from Appalachian region were moved on their places in Germany and Poland. Some new conceptions of the European Caledonides and Hercinides model (1,20,29) were proposed from time of mentioned hypothesis. According them these belts were wrench orogens, formed in spite of concentration and joining the removed terranes. Such features characterize the North German-Polish Caledonides. Now any discussion about Middle European Caledonides, basing on relicts of Caledonian orogens within Hercinides, should be carefully continued because of their unsure primary location. The five terranes of the North German-Polish Caledonides were distinguished. The terrane of Southern Jutland and adjacent part of North Sea characterizes with 3-stage metamorphism: most common stage (450–440 Ma) of Late Ordovician age corresponds to the Taconian phase, common stage (530–490 Ma) is connected with Early Caledonian movements (Grampianides) and the rare last one (420-400 Ma) was regarded by A. Berthelsen (3) as "old imprint corresponds to the Late Caledonian-Scandian orogenic phase". The lack of metamorphism, strong movements of Taconian orogenic phase and weeker of Scandian one characterize the Pomorze terrane. The Łysogóry terrane has unknown basement of Younger Cambrian age, on which the primary platform-type deposits were horizontaly arranged, later dislocated by Variscian movements. The Małopolska terrane was subjected to strong Grampian movements with week but distinct metamorphism (560–480 Ma). The undisturbed Ordovician-Silurian deposits of other platform type lie there and some data point there the Cadomian metamorphism (660–600 Ma). Similar age is the Upper Silesia terrane. The paleomagnetic investigations from the Małopolska terrane (4, 28) proved that Early Cambrian-Ordovician paleoinclination was 78-74° but in Late Silurian – 7–27°. Comparing these results with paleoinclination data from the Easteuropean platform M. Lewandowski (28) concluded that before Late Silurian this terrane was about 4000 km farther from recent position. All these data proved an existence of the huge shifting event, dating it precisely. The studies of D.H. Hutton (20) and R. Mason (29) suggest that main kinetic movements took place in Wenlockian and Ludlovian ages. This is 8 confirmed by data from Poland where the beds younger than Early Ludlovian were continuously deposited on terranes and adjacent part of the Easteuropean platform, covering that giant dislocation zone. These beds have some flysh features (22, 45, 53) but should be qualified as molassa within orogenic cycle. Their sedimentary characteristics and significant thickness are connected with the uplifting and erosion in last pulling phase, so called "terrane docking" (3, p. 268). An enormous differentiation of terranes indicates that they were detached from various orogens and shuffled during transport. The Upper Silesia terrane came from southern border of Iapetus Ocean and contains, together with the Małopolska terrane, the Holmia faunas, typical for shelf surrounding the Baltic shield. This shelf with its biofacies was primary extended far to West beyond the zero meridian. These data were deducated from the terrane model for Silurian Epoch, founding that terranes were transported by shifting on distance of several thousands kilometers. The connections of English terranes with the Appalachian belt, placed far to West confirmed this conception (4, 20).

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