A boulder (Sol_50-8) showing typical shallow marine sedimentary structures of the Zhurong Member. (IMAGE)
Caption
Block diagrams show interpreted sedimentary structures. The boulder is about 110 cm across and preserves a series of left-dipping planar surfaces separating 2-10 cm thick tabular units interpreted to be primary sedimentary bedding and is generally consistent with that on the surrounding ground. The greenish tint on some surfaces is due to color saturation of the sensors, and not real. The beds have internal laminations that differ from bed to bed. These features are used to interpret the primary depositional environment. Note that the boulder is locally sculpted by wind, in places covered by wind-blown dust or sand, and possibly affected by chemical weathering or cementation. a’’. Stratigraphic section drawn perpendicular to bedding along the front face of the outcrop, and placing boulder c on top, as it appears to strike with a small missing gap. The section is divided into six units of planar, herringbone, convex-up, and trough cross-laminated layers, suggestive of deposition by bi-directional subaqueous currents. Details of features from red boxes on panel a. b. Features interpreted as herringbone cross-laminae formed by bipolar current directions, typical of alternating currents. c. Features interpreted as trough cross-lamina from a separate boulder in the background, representing bipolar current directions, overlain by planar cross-laminated sand. Boulder is possibly out of place or even upside down, but appears to have similar orientation as the main boulder. d. Features interpreted as planar bedding visible in 3D around a corner in the boulder, overlain by a concave cross-laminated unit. e. Features interpreted as herringbone cross-lamina, strongly etched by wind, forming a pseudo-fan shape.
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