Environmental Engineering Reference
In-Depth Information
Excavated
metal
container
FIGURE 2.35
Example of anthropogenically deposited material. (Photo by Daniel T. Rogers.)
• Nonnaturally occurring debris located within sediments
• Evidence of excavation
• Lack of original deposition structures within the deposits in question
• Inconsistency or evidence of stressed or absent vegetative cover
• Topography inconsistent with surrounding area or region
Figure 2.35 is a photograph showing landfill material. In this case, several metal containers
were excavated indicating anthropogenic disturbance.
2.6.2 Naturally Occurring Disturbance
Examples of naturally occurring types of disturbance include the following (Pettijohn 1975):
• Diagenesis, typically involving compaction and lithification.
• Erosional removal of a portion or an entire deposit (causing an unconformity).
• Bioturbation involving the disturbance of very near-surface soil layers, typically
by worms and other macro invertebrates.
• Vegetative disturbance from trees with large and deep root systems.
• Differential compaction or subsidence; these events can obscure, bend, or offset
original depositional deposits and sequences and make interpretation of deposi-
tion challenging.
• Redistribution of sand deposits by wind along a beach, forming dune deposits
often difficult to recognize because many dune deposits do not contain easily rec-
ognizable depositional structures.
• Offsets in bedding planes or sediment layers from faulting or other tectonic activ-
ity. The results of tectonic offsets may make the matching of depositional layers
impossible depending on the distance of the offset.
• Landslides along steep slopes or unvegetated hillslopes resulting from fire or
flooding.
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