PLATE RECONSTRUCTION OF ASTYPALAEA LINEA, EUROPA: A CASE FOR TRANSTENSIONAL GENERAL SHEAR

Astypalaea Linea (AL) is a 300 km by 40 km region of Europa riddled by fractures, ridges, sulci, and troughs that display a dominant dextral sense-of-shear. While Europa’s icy crust does not behave with the exact same Earth-style tectonics and deformation, previous studies identify AL as analogous to pull-apart structures on Earth. Former studies with two-dimensional reconstructions reverse the emplacement of a band of young material by identifying and re-establishing piercing points from either side of the band. After the researchers moved ridges, troughs, furrows, and other linear and planar features to as close an approximation of original position as possible, they discovered that AL’s transtensional feature has an average displacement of 60 km.

We present a reconstruction of AL to its initial configuration using GPlates, a mapping software based in three-dimensional projection, and consider the young band of material during the latter half of rotation and translation of blocks of solid state ice. We mapped 375 polygons that define the microplates and projected Galileo satellite imagery to a globe and pin the raster to our model of the icy blocks. Incremental restorations of plate positions at intervals of 5 My between 50 Ma and present day model how AL evolved over time. Additional to retro-fitting piercing points, after 25 Ma we consider the band of young ice to be formed and to move along with the other bounding microplates.

While we model original plate positions similar to previous studies, we argue that the young band also preserves sinistral kinematics that must be accommodated for. As such, we also end with final displacement of on average 60 km, though with a larger dextral movement followed by a sinistral contraction before AL reached its final geometry. We conclude that AL experienced two episodes of general shear to achieve its modern-day appearance.