22 Undergraduate Research Poster Session II

Saturday, 29 March 2025
8:30 AM - 5:30 PM
North Great Hall

USING ANISOTROPY OF MAGNETIC SUSCEPTIBILITY (AMS) TO APPROXIMATE STRAIN ORIENTATIONS WITHIN THE PULO DO LOBO FORMATION AFFECTED BY THE SOUTHERN IBERIAN SHEAR ZONE

Paper number: 22-24
Program: Theme Sessions
Time: 8:30 AM – 5:30 PM

Authors

Abstract

The Southern Iberian Shear Zone (SISZ) is a Variscan-aged suture located in southwestern Spain between the Ossa-Morena Zone (OMZ) and the South Portuguese Zone (SPZ). The SISZ juxtaposes the Beja-Acebuches Metabasites and the Pulo de Lobo metasedimentary formation (PdL) comprised of interbedded quartzites and metapelites. This shear zone also contains interesting kinematics with variable degrees of flattening with both left-lateral and thrust deformation. Here, we used Anisotropy of Magnetic Susceptibility (AMS) within the PdL to identify finite strain orientations which can be used to unravel the complex kinematics. We collected oriented PdL samples in the field along two transects perpendicular to the shear zone and later cut them into cubes (2cm x 2cm x 2cm) for AMS analysis. The magnetic mineralogy consists largely of paramagnetic minerals such as biotite with minor contributions from titanomagnetite or hematite. The AMS analysis was conducted using a multi-functional Kappabridge instrument. Preliminary results show that the foliation orientation measured from AMS resembles the foliation orientation measured in the field, and the magnetic lineations are highly variable in orientation similar to the scarce macroscopic mineral lineations that could be measured. The magnetic fabric shape parameter indicates that the rocks underwent a dominant flattening strain. Our further work will investigate whether the magnetic fabric anisotropy strength or shape fabrics change with respect to distance from the shear zone in order to further constrain kinematics and strain development of the SISZ. To form a more complete picture of the SISZ deformation within the PdL, this data can be used in conjunction with ongoing structural analysis, geochemical study, and microstructural research of this zone.

Geological Society of America Abstracts with Programs. Vol. 57, No. 3

doi: 10.1130/abs/2025NE-408689

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