Magnetic fabric of deformed Quaternary sediments: contributions to the understanding of the neotectonic activity in the surroundings of the Aburrá Valley, Central Cordillera, Colombia

Abstract

The origin of the Aburrá Valley (AV) is proposed as a set of coalescent tectonic subbasins located along the northern  portion of the Central Cordillera of Colombia, the Northern  Andes of Colombia. The Itagüí, Medellín, Bello, and Barbosa  subbasins have developed between the Romeral Shear Zone (RSZ) and the Antioqueño Batholith starting in the Late  Cenozoic. The aim of this study is to contribute to the  understanding of the AV neotectonic framework using the  anisotropy of magnetic susceptibility (AMS) and structural  analysis. For this, we measure the magnetic fabric ellipsoid  shape of faulted sediments and compare them with the geometry and kinematics of fault planes to determine their  relationship with the present-day stress field and the  regional fault architecture. The principal directions of the  elongation axes along the La Brizuela and Yarumalito sites  were NE-SW, following the magnetic lineation trend and  marking a normal displacement with a dextral component.  A marked NW-SE magnetic cleavage was found for the La  Caimana site along a strike-slip tectonic setting. Holocene  ruptures of the principal displacement zone (i.e., the RSZ)  and their surroundings, may indicate normal faulting, with  fault bends and steps over basins controlled primarily by R´ and P structures. Moreover, the active faults located to the  east of the AV indicate post Plio-Pleistocene deformations  with normal faulting through 90/80 to 150/70 antithetic  faults. This work identifies the AMS technique as a powerful  tool, for understanding the neotectonic framework along  urban and surrounding areas.