New evidence for block and thrust sheet rotations in the central northern Calcareous Alps deduced from two pervasive remagnetization events

Abstract

[1] We present 81 paleomagnetic sites (Early Triassic to Early Cretaceous) from the central sector of the northern Calcareous Alps (NCA, Eastern Alps, Austria and Germany). Stepwise thermal demagnetization defines three magnetic directions mostly carried by low unblocking temperature and low-coercivity minerals: J3, 350°; J2, 500°; J1, 575°and 680°. J3 and J2 show positive inclinations, whereas J1 (very seldom) is of dual polarity. The fold tests show that a J3 can be interpreted as a postfolding and posttilting remagnetization and J2 as a postfolding and pre(syn)tilting. J1 can be considered as primary because of the occurrence of two polarities and evidence presented by other authors in the area. All three components show a systematic and significant clockwise rotation after comparing with the expected European references. J2 or J1 are marked by higher rotation values than J3. J2 shows different inclinations depending on the structural position (north or southward dips). Considering the structural evolution and the observed inclinations, the first postfolding and pretilting remagnetization event (J2) could have taken place between Late Cretaceous and Eocene times but certainly before the thrusting of the NCA over the Rhenodanubian Flysch and northward tilting caused by the stacking of the lower Austroalpine nappes. The second postfolding and posttilting remagnetization (J3) would have been acquired after the final thrusting of the NCA over Penninic units. From then, the NCA behaved as a set of rigid blocks recording the main stage of vertical axis clockwise rotation (65°in average) associated with the continental collision. The variable degree of rotation in the different positions (from 40°to 134°) can be explained by individual vertical axis rotation in a block system trying to adjust to space problems. The constant declination differences between J2 and J3 (25°in average) would reflect the rotation related with the lateral differences of shortening during the oblique thrust of the Austroalpine units over the Penninic units.

40 Ar/ 39 Ar ages of crystallization and recrystallization of rock-forming polyhalite in Alpine rocksalt deposits

“…A last significant apparent age was found at c. 44 Ma. This is consistent with an apatite fission track study (Hejl & Grundmann 1989) and regional remagnetization data (Pueyo et al 2007). Together, the first polyhalite age data from the Upper Permian to Lower Triassic Haselgebirge Formation of the Eastern Alps, the type locality of polyhalite, yield meaningful geochronological results which are similar for two salt deposits c. 60 km apart.…”

Austrian versus Hungarian bauxites in an Alpine tectonic context: a tribute to Prof. Andrea Mindszenty

“…This cartoonish map-view restoration admittedly ignores the complex post-Santonian rotations documented in both the NCA and the TR by palaeomagnetic declination anomalies (e.g. Mauritsch & Becke 1987, Márton et al 2000, Márton & Fodor 2003, Pueyo et al, 2007. We believe that the right lateral Cretaceous strike-slip faults of the NCA may be correlated with those of the TR.…”

“…Admittedly, this cartoonish map-view restoration ignores the complex post-Santonian rotations documented in the NCA and the TR by palaeomagnetic declination anomalies (e.g. MAURITSCH & BECKE 1987, MÁRTON et al 2000, MÁRTON & FODOR 2003, PUEYO et al 2007.…”

“…Ez a vázlatos térképi rekonstrukció beismerten figyelmen kivül hagyja a komplex posztszenon forgásokat amiket mind az NCA és mind a TR esetében paleomágneses deklinációs anomáliák jeleznek (pl. MAURITSCH & BECKE 1987, MÁRTON et al 2000, MÁRTON & FODOR 2003, PUEYO et al 2007). Mi úgy gondoljuk, hogy az NCA kréta korújobbos elmozdulásai valószínűleg korrelálhatók a TR hasonló haránttöréseivel.…”

A model of dinoflagellate cyst distribution around the K/Pg boundary and its paleoenvironmental implications (Eastern Alps)

“…Paleomagnetic data and general plate tectonic reconstructions for these deposits suggest a paleolatitude of 20° to 30° N (Haubold et al, 1999;Pueyo et al, 2007). The transgression of the Gosau Group was the result of transtension, followed by rapid subsidence into __________________________ _____________________ Figure 1: Simplified geological map of the Eastern Alps (after Faupl and Wagreich, 2000).…”