BOUDINS IN THE SOUTHERN IBERIAN SHEAR ZONE

The Southern Iberian Shear Zone forms a 50 km Variscan suture in the Iberian Massif and caused deformation in adjacent rocks within the Pulo do Lobo Formation. The Pulo do Lobo Formation near the shear zone consists of interbedded quartzites and metapelites that contain a variety of structures including boudins of quartzite surrounded by metapelite. This study looks closely at the boudins, their shapes, and their proximity to the shear zone. Using the application StraboSpot, we constructed detailed structural maps of boudins and related features, and distance of boudins from the shear zone was recorded.

We calculated length-to-width ratios of each boudin in order to approximate the degree of strain. It appears that closer to the shear zone, there are an increased number of boudins, and that once out of the affected area, the boudins are absent. The degree of deformation recorded by the boudin shapes is expected to increase with proximity to the shear zone, and this will be tested with our further research. We also measured strings of connected boudins to calculate extension and will compare this to shear zone proximity.

Studying strain in the boudins can help us understand how strain magnitude diminishes with distance from shear zones.