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Paleomagnetic results from Northeast Anatolia: remagnetization in Late Cretaceous sandstones and tectonic rotation at the Eastern extension of the Izmir–Ankara–Erzincan suture zone

Çinku M. C.

Acta Geophysica

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2017

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Vol. 65, no. 6

1095--1109

EN

Paleomagnetic results obtained from Upper Cretaceous sandstones in Northeastern Anatolia demonstrate that the entire area from Erzincan to Kars has been remagnetised. The remagnetisation was acquired before the Middle Eocene collision between the Eastern Pontides and the Arabian Platform because Middle Eocene sandstones carry primary natural remanent magnetisations. The post-folding in situ mean direction of the Upper Cretaceous sandstones is compared with mean directions of younger, Middle Eocene to present rock formations. As a result, a twostage antagonistic rotation mechanism is proposed. First, the collision between the Pontides and the Taurides between Late Cretaceous and Middle Eocene was associated by clockwise rotation of ~ 26°. In the second stage between Middle Eocene and Middle Miocene and beyond, counterclockwise rotations up to ~ 52° of the Pontide and Anatolide blocks and clockwise rotations of the Van Block were characterised by regional shortening and westward escape.

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Mesozoic remagnetization of Upper Devonian carbonates from the Česis and Skaistgirys quarries (Baltic states)

Katinas V., Nawrocki J.

Geological Quarterly

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2004

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Vol. 48, No 3

293-298

EN

The palaeomagnetic properties of Frasnian and Famennian dolomites from two quarries in Latvia and Lithuania respectively are compared. Famennian dolomites from Skaistgirys quarry (N Lithuania) revealed the presence of one distinct normal polarity component (D =14 degrees Celsius, I = 53 degrees Celsius, 95 = 4.2 degrees Celsius, n = 28 specimens). The reversed polarity component predominates in Frasnian dolomites from Česis quarry (Central Latvia). Only one hand specimen from this locality contained a component with the opposite direction. The mean direction from Česis quarry (D = 198 degrees Celsius, I = -53 degrees Celsius, 95 = 4.4 degrees Celsius, n = 22 specimens) is very close to that from Skaistgirys quarry and therefore was recorded most probably during the same event of remagnetisation but at a later stage. The remagnetizations of these dolomites were caused most probably by progressive oxidation of ferric sulphides to magnetite and finaly to hematite. A comparison of the palaeomagnetic poles obtained with the stable European APWP (Apparent Polar Wander Path) indicates a Late Jurassic/Early Cretaceous age for the remagnetization event. This estimation can be useful for chronostratigraphic linking of post-Palaeozoic tectonic activity and diagenetic events, so far very poorly recognized in this part of the European plate. Our data shows also that the Late Jurassic/Early Cretaceous part of the stable European APWP may still be inaccurate.

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Palaeomagnetism of some Devonian carbonates from the Holy Cross Mts.(Central Poland): large pre-Permian rotations or strain modifiedpalaeomagnetic directions?

Grabowski J., Nawrocki J.

Geological Quarterly

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2001

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Vol. 45, No 2

165-178

EN

Palaeomagnetic studies of Middle and Upper Devonian carbonate rocks in the Holy Cross Mts. (Central Poland, SW foreland of the East European Craton - EEC) involved samples from the southern (Kielce) and northern (Łysogóry) unit. Haematite-bearing carbonates showed syn-folding remagnetisation of Early Permian age. The pole of this component is situated on the apparent polar wander path (APWP) of the EEC. The syn-folding age implies deformation of the Variscan syncline during Alpine uplift of the Holy Cross Mts. In dark limestones and dolomites magnetite was a dominant magnetic mineral. The age of magnetisation is interpreted as pre-Late Carboniferous: syn-folding in one locality and either pre- or syn-folding in four others. Four poles calculated from these components are shifted to the NW from the reference southern APWP for the EEC and one pole is concordant with its Early Carboniferous segment. The occurrence of rotated and unrotated palaeomagnetic poles could indicate that some fragments of both Kielce and Łysogóry units were subjected to local clockwise rotations during Variscan compression. An alternative explanation might be that Variscan pre- and/or syn-folding components could be strain modified or resultant magnetisations and they should not be used in palaeotectonic reconstruction.