HR: 0830h
AN: P41A-0398    [PDF]
TI: Land of Extremes: Faulting and Shear in Europa's North Pole
AU: * Figueredo, P H
EM: figueredo@asu.edu
AF: Arizona State University, Department Geological Sciences, Tempe, AZ 85287-1404 United States
AU: Greeley, R
EM: greeley@asu.edu
AF: Arizona State University, Department Geological Sciences, Tempe, AZ 85287-1404 United States
AB: Tectonic processes dominate the evolution of the north polar areas of Europa. Our study area, centered at $\sim$220\deg\ /67\deg\ N and imaged by Galileo at $\sim$170m/pixel, shows a complex tectonic history with multiple generations of crosscutting lineaments. Structures associated with strike-slip and extensional deformation are dominant, and there is very little indication of cryovolcanic activity. All strike-slip displacements are left-lateral, in agreement with predictions of diurnal tidal stresses for these latitudes [1]. Offsets determined by plate reconstructions range from few km to $\sim$92 km, the largest displacement measured so far on Europa (see also [2]). The variety of structures associated with strike-slip motions is surprising, and include simple fractures and ridged bands several km wide. There is no relationship between the amount of offset and the type of structure accommodating it, but it is possible that primary or secondary features (i.e., accommodating deformation elsewhere) might result in different morphologies. Extension and transtension occur across narrow ($<$15km wide) bands, cycloidal ridges, and triple points. Most extensional structures display axial symmetry and raised margins, indicating widening of original double ridges. We note that the relative albedo of the bands' interior does not always follow the "younger, darker" trend seen elsewhere [e.g., 3]. Precise stratigraphic analysis of the study area has allowed us to correlate the geologic histories of distant areas. In addition, the northern plains of Europa are a good location for examining temporal trends in tectonic processes without the influence of cryovolcanic activity. Changes in the style and degree of tectonic deformation are being studied by determining the different types of features and amounts of offset at different times. In addition, stereo observations are available for most of this area, and we are currently generating a digital elevation model of the local topography. Because of the extent of the stereo coverage, this information will allow us to examine the topographic signature of different kinds of structures in the same region. [1] Hoppa et al., Icarus, 141, 287-298, 1999; [2] Sarid et al., Icarus, 158, 24-41, 2002; [3] Geissler et al., Icarus, 135, 107-126, 1998.
DE: 5475 Tectonics (8149)
DE: 6218 Jovian satellites
DE: 8010 Fractures and faults
DE: 8149 Planetary tectonics (5475)
DE: 8155 Plate motions--general
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting