Anisotropy of magnetic susceptibility (AMS) constrains on uplift kinematics of The Sierra Nevada culmination during Plio-Pleistocene, Betic Cordillera, Spain

Abstract

We collected rock fabric (AMS) data in Plio-Pleistocene deposits around Sierra Nevada (Spain) to explore the presence of low-grade penetrative fabrics that can contribute additional constrains to the ongoing discussion on the emplacing kinematics of the orogen. Sierra Nevada is a regional E-W trending mountain range located in the Betic Cordillera and consists of folded and stacked thrust sheets emplaced during the Late Miocene. Previous interpretations are that the Sierra Nevada dome was emplaced by top to the west extension and isostatic rebound after thrust belt formation or alternatively, uplift resulted from contractional strain during N-S oriented pure shear. To determine the fabric we measured low field susceptibility. Results from heating and cooling experiments show a complicated magnetic mineralogy from virtually all ferromagnetic to virtually all paramagnetic between samples collected from varied structural positions. The fabric ellipsoid is coherent with low strain, uniformly oblate in shape and records a compaction fabric (Z) with superimposed tectonic strain where the principal elongation axis (X) is variable north and south of Sierra Nevada. The X-axis is preferentially oriented NNE-SSW to NE-SW to the south and shows a general E-W orientation, in the northern sampling site. The results are inconsistent with previous models of culmination formation proposed in the literature and suggest that the Plio-Pleistocene evolution on Sierra Nevada may be disconnected from the older emplacement kinematics and may be affected by the general strike slip tectonic active along the margin of the Alboran Sea.