Abstract. The anisotropy of magnetic susceptibility (AMS) technique provides
an effective way to measure fabrics and, in the process, interpret the
kinematics of actively deforming orogens. We collected rock fabric data of
alluvial fan sediments surrounding the Sierra Nevada massif, Spain, and a
broader range of Cenozoic sediments and rocks across the Northern Apennine
foreland, Italy, to explore the deformation fabrics that contribute to the
ongoing discussions of orogenic kinematics. The Sierra Nevada is a regional
massif in the hinterland of the Betic Cordillera. We recovered nearly
identical kinematics regardless of specimen magnetic mineralogy, structural
position, crustal depth, or time. The principal elongation axes are NE–SW in
agreement with mineral lineations, regional GPS geodesy, and seismicity
results. The axes trends are consistent with the convergence history of the
Africa–Eurasia plate boundary. In Italy, we measured AMS fabrics of
specimens collected along a NE–SW corridor spanning the transition from
crustal shortening to extension in the Northern Apennines. Samples have AMS
fabrics compatible only with shortening in the Apennine wedge and have
locked in penetrative contractional fabrics, even for those samples that
were translated into the actively extending domain. In both regions, we found
that specimens have a low degree of anisotropy and oblate susceptibility
ellipsoids that are consistent with tectonic deformation superposed on
compaction fabrics. Collectively, these studies demonstrate the novel ways
that AMS can be combined with structural, seismic, and GPS geodetic data to
resolve orogenic kinematics in space and time.
Stratigraphy, paleomagnetism, and anisotropy of magnetic susceptibility of the Miocene Stanislaus Group, central Sierra Nevada and Sweetwater Mountains, California and Nevada
