Alpine remagnetization and tectonic rotations in the French Pyrenees

Abstract

A palaeomagnetic study of the 100 to 90 m.y. old alkaline igneous rocks of the French Pyrenees has in part revealed large between-site scatter caused by highly variable declination. Magnetomineralogical evidence suggests that the original titano-magnetite has undergone variable low-temperature oxidation through martitization and maghemitization processes, suggesting that the rocks have been remagnetized. When viewed in the context of the Upper Cretaceous-Lower Tertiary inclination pattern based on Portuguese palaeomagnetic data, it is concluded that the rocks most likely acquired their present magnetization during early Campanian-Maastrichtian time, i.e. 20-30 m.y. after their original cooling. On the other hand, this magnetization postdates a major phase of late Cretaceous compressive deformation. Subsequent strike-slip movement along the Pyrenean zone in the Lower Tertiary led to variable rotation of cover units along the orogenic belt, producing the inconsistent palaeomagnetic declination picture presently observed. It is concluded that the geological history of the alkaline rocks of the French Pyrenees, from the magmatic stage to the subsequent events of remagnetization and tectonic deformation, is strongly associated with the Alpine-age rotational instability of Iberia. The principal kinematic history of the Peninsula comprised ca. 40°counterclockwise rotation (relative to Europe) during Cenomanian-Turonian time (100-90 m.y. ago) followed by ca. 70°clockwise rotation in the early Campanian (ca. 75 m.y. ago).

Interpretation of the Gravity and Magnetic Anomalies of the Cappadocia Region, Central Turkey

“…Adding to the tectonic complexity of the region, clockwise rotation of the western extremity of the Cappadocian collage has been suggested by palaeomagnetism (PIPER et al, 2002). STORETVEDT et al (1999), based on a palaeomagnetic study of alkaline igneous rocks of the French Pyrenees concluded that during the Alpine climax the Iberian Peninsula first rotated 40°counterclockwise and then 70°clockwise. The reason for this rotational instability is that the Peninsula is located within the tectonically strained Alpine region, being squeezed in between the oppositely rotating Eurasia and Africa megablocks.…”

LA-ICP-MS U-Pb apatite dating of Lower Cretaceous rocks from teschenite-picrite association in the Silesian Unit (southern Poland)

“…Filled symbols represent data from : Smulikowski 1929;Mahmood 1973;Kudlásková 1987;Dostal & Owen 1998;Włodyka 2010 (Harangi & Árva-Sós 1993). Mesozoic teschenites are rare elsewhere although occurences have been documented in Georgia (Lebedev et al 2009), the French Pyrenees (Azambre et al 1992;Storetvedt et al 1999) and Russia (Transbaikalia - Metelkin et al 2004;Stupak et al 2004) where volcanic activity associated with teschenite emplacement occured during the Late Cretaceous (from 86 to 110 Ma).…”

New and revisited paleomagnetic data from Permian–Triassic red beds: Two kinematic domains in the west-central Pyrenees

“…( (a) Delacotte et al (1985); Barchi et al (1997); Le Callonnec et al (1997); Galbrun (1997); Thibal et al (1999); Storetvedt et al (1999); Galbrun and Gardin (2004).…”

“…1.a and c), and two sectors in the North: (1) Upper Cretaceous-Cenozoic boundary in the North-West (number 8 in Fig. 1.a) (Barchi et al, 1997;Delacotte et al, 1985;Galbrun, 1997;Galbrun and Gardin, 2004;Le Callonnec et al, 1997;Storetvedt et al, 1999;Thibal et al, 1999), ( 2 (Gisbert, 1981(Gisbert, , 1983 found in the west-central Pyrenees: the Paleozoic Basque Massifs on one hand, with variable recorded rotations, and the south Pyrenean Zone on the other hand, where there is a lack of large vertical axis rotations.…”