Radar Image

The Radarsat image of Oasis (Fig. 7) shows a concentric pattern associated with the structure. Similar to the radar image for BP, the radar data for Oasis show that the concentric structure, which appears as discontinuous concentric bands in the visible light data, is a continuous structure both laterally away from the structure as well as circumferentially around it. This pattern suggests uniform deformation around the circumference of the structure. Areas that appear only in the visible wavelengths and which are bright in the radar are presumably differentially weathered material that stands above the sand sheet. The northwest-trending features observed in the visible images are also apparent in the radar as bright linear features, again indicating that most of the feature stands above the sand. These features can be traced along strike where they have lower brightness, suggesting that they are not exposed at the surface but buried by the sand sheet.

The drainages are very well defined in the radar data, particularly along the west and east sides of the structure. They clearly control the distribution of alluvial material seen in the Landsat images. The drainage on the west side of the structure appears to be a single major channel with a few tributaries, compared with the more braided nature of the drainage on the east side of the structure. This difference could be controlled by topography.

Fig. 14. Alleged clastic plugs (Underwood and Fisk, 1980) north of the Oasis structure, apparently outside of limit of deformation visible in the field.
Fig. 15. Deformed ridge near clastic plugs, about 4 km outside the inner ring at Oasis.
Color Plate: (1, top) BP impact structure (visible natural light, Landsat image). (2, bottom) Oasis impact structure (visible natural light, Landsat image).

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