MODELING THE TECTONIC STYLES OF ICY PLANETARY SURFACES AND THEIR TERRESTRIAL ANALOGS

Abstract

Tectonics on icy surfaces of the Solar System present a number of issues relevant for understanding the geologic evolution and the geodynamic processes of icy bodies. The recognized strong evidence of extensional tectonic regimes and the paucity of compressional structures leave unclear their structural balancing. This assumption opens the issue on the existence of a prevalent tectonic regime and a preferential style of deformation affecting the icy planetary surfaces. The present dissertation addresses this problem by improving our understanding on the tectonic regimes that deform the icy surfaces. The investigation is performed by the modeling of the tectonic setting of selected study areas in confined (closed) and unconfined (open) icy surfaces. These were identified in the icy satellites Ganymede and Enceladus (confined study cases), and in the northern polar cap of Mars (unconfined study case). Their comparison with their terrestrial analogs, identified in the Antarctic ice sheet, supports the investigation. The tectonic structures in the investigated regions are studied by a multidisciplinary structural geology approach that includes remote sensing, structural mapping, geomorphology, and quantitative (geo)statistical analyses. A total of three tectonic models are prepared and describe the kinematic evolution of the investigated icy surfaces. Ganymede model suggests transpressional tectonics in the Uruk Sulcus region, and the identification of regional groove systems proposed in the structural map of Ganymede grooves allow to recognize significant regional strike-slip tectonics affecting its surface. Transpression is also recognized by the model proposed in the South Polar Terrain of Enceladus, where block rotation tectonics characterizes the Tiger Stripes kinematics. The tectonic model proposed for the northern polar cap of Mars attributes the origin and evolution of the spiral troughs to the activity of low-angle normal faults that fade in a ductile detachment at depth.