Signs of Soft-Sediment Deformation at “Slickrock”

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Caption:

Geological examination of bedding textures indicates threestratigraphic units in an area called "Slickrock" located in the martianrock outcrop that NASA's Opportunity examined for several weeks.This is an image Opportunity took from a distance of 2.1 meters (6.9feet) during the rover's 45th sol on Mars (March 10, 2004) and shows ascour surface or ripple trough lamination. These features are consistentwith sedimentation on a moist surface where wind-driven processes mayalso have occurred.

Figure 1

In Figure 1, interpretive blue lines indicate boundaries between the units. Theupper blue line may coincide with a scour surface. The lower and upperunits have features suggestive of ripples or early soft-sedimentdeformation. The central unit is dominated by fine, parallelstratification, which could have been produced by wind-blown ripples.

Figure 2

In Figure 2, features labeled with red letters are shown in an enlargement ofportions of the image. "A" is a scour surface characterized by truncation of theunderlying fine layers, or laminae. "B" is a possible soft-sediment bucklingcharacterized by a "teepee" shaped structure. "C" shows a possible ripplebeneath the arrow and a possible ripple cross-lamination to the left of thearrow, along the surface the arrow tip touches. "D" is a scour surface orripple trough lamination. These features are consistent with sedimentationon a moist surface where wind-driven processes may also have occurred.

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