Geomorphological Analysis of the Southwestern Margin of Xanadu, Titan: Insights on Tectonics

Abstract

Evidence for tectonic activity on Titan is provided by the presence of eroded mountain ranges. Xanadu is an equatorial region of Titan characterized by a complex topography, even though, overall, it has a lower average elevation compared to its surroundings. We investigated Xanadu's southwestern margin, a part of the region composed of heavily eroded and rugged terrains to the north and east, and of smoother, more uniform terrains to the west and south. The central portions of southwestern Xanadu (SW Xanadu) are characterized by an extensive fluvial network. The presence of such a distinctive feature was the main reason motivating the study of this area, given its potential to provide tectonic indications. Through detailed geomorphological mapping (map scale 1:700,000) on Synthetic Aperture Radar data and analysis of both fluvial drainage patterns and Digital Terrain Models, we identified several putative tectonic structures in this area: normal faulting to the west and east, thrust faulting to the north, and small-scale strike-slip faulting in its central parts. Pull-apart basins are depressions bounded by both dip-slip faults and by (overlapping and/or bending) segments of a major transcurrent fault, i.e., they are basins generated in transtensional tectonic settings. We propose that central SW Xanadu is a pull-apart basin, bordered by both normal and thrust faults and formed by transtensional tectonics, which we consider to be the most recent tectonic phase active in this area. This basin is characterized by small-scale strike-slip faulting within it, on which a fluvial network has subsequently imposed.

Plain Language Summary

Saturn's largest moon, Titan, has several mountain ranges on its surface. It is thought that they are formed by large-scale processes related to Titan's interior, such as tectonic activity. Xanadu is an equatorial region characterized by a rugged topography, even though its surrounding regions stand higher. We investigated Xanadu's southwestern margin, which is characterized by many different terrain types and by the presence of a hydrocarbon-related fluvial system. At Titan's surface pressure and temperature, hydrocarbons are in a liquid state and can therefore form rivers. Using radar data from the Cassini mission, we mapped in detail the differences in morphology of each terrain in the region. Furthermore, we analyzed local fluvial drainage patterns and different types of elevation data. We identified several areas that may testify the influence of Titan's internal processes on shaping SW Xanadu. We propose that different tectonic phases have been active in this region through time.