Environmental Engineering Reference
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FIGURE 4 Burrowing bivalves and the resultant traces. White scale bar is 2 cm. (A) Downward-
deflected sediment lamination (equilibrichnia; outlined by the white dashed line) around the bivalve
Tresus nuttalli . (B) Lockeia (L) on a bedding plane, generated by Mya arenaria in mud. Bottle cap is
2.6 cm. (C) Concentric sediment lamination (dashed white line) around the siphon hole of M . are-
naria in sandy mud. Scale bar is in centimeters. (D) Single-siphon Siphonichnus (Si) made by
M . arenaria in sand. Note the downward-deflected mud laminae around the siphon shaft. (E)
Dual-siphon Siphonichnus made by Nuttallia obscurata in sand. (F) Sand-filled Gastrochaenolites
(Ga) made by Petricola pholadiformis (inset photo) in sandstone.
of en-echelon chevrons where the shell was pushed apart to drive the animal
forward. The movement of shallowly burrowing bivalves and gastropods can
cause significant disruption in the upper few centimeters of the sediment.
2.3 Crustaceans
The range of burrow morphologies produced by crustaceans rivals that of
vermiform animals. Crustacean burrows can be unlined or lined with fecal
material. Unlike vermiform animals, however, crustacean-burrow diameters
are commonly variable along their length. In marine settings, the dominant
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