Environmental Engineering Reference
In-Depth Information
FIGURE 2.27
Sand deposit with festoon-type cross-bedding in Michigan. Hard hat in upper left for scale. (Photo by Daniel
T. Rogers.)
Coarser grained layers
DNAG
Photo scale
Finer grained layers
CM
IN
1 2 3 4 5
FIGURE 2.28
Sand deposit with planar tabular type of cross-bedding. (Photo by Daniel T. Rogers.)
investigating urban sites and help them distinguish whether the deposits being examined
originated from a natural process or formed by anthropogenic activity.
• Ripple marks—formed within wind-blown dune deposits or along beach deposits
generally in shallow water. Ripple marks are very small dune-like deposits whose
long axes are perpendicular to the air or water current forming them. Ripple
marks commonly form either as asymmetrical ripple marks or as oscillation ripple
marks. Asymmetrical ripple marks form in shallow water or as dune deposits
where there is a dominant direction of water current or wind. Oscillation ripple
marks form in shallow water within the surf zone where there are competing and
opposite directions of water flow.
• Mudcracks—are also commonly termed desiccation cracks. These features are
formed when a fine-grained deposit—often clay-sized—undergoes drying and
then is buried, preserving the feature.
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