Environmental Engineering Reference
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feeding burrows. In this case, the scientific value of a good classification is
clear. The morphology and sedimentology of agrichnia and chemichnia raise
questions that cannot be answered within the existing classification, which sug-
gests new categories and new directions for research.
6.7 Escape Traces (Fugichnia)
Escape traces ( Frey, 1973 ) are those made by animals that have been rapidly
buried by a layer of sediment. This requires that the animal be reasonably mus-
cular and able to respire while temporarily buried. Not all animals can escape
rapid burial; some succumb to a light dusting of sediment while others can dig
upward for many centimeters. Accordingly, the bodies of some hard-shelled
animals, such as gastropods, can be found in escape position where they died
within a storm bed (tempestite) or turbidite, and some fugichnia likewise do
not penetrate the full thickness of a bed.
Fugichnia are temporary structures and accordingly are not open or rein-
forced. They chiefly consist of disturbed laminae ( Ekdale et al., 1984; Sch ยจ fer,
1972 ). Collapsed shafts may resemble fugichnia, but the laminae of fugichnia
tend to have a relatively constant angle with relation to the burrow wall.
6.8 Brooding Traces (Calichnia)
Genise and Bown (1994) proposed calichnia as a name for biogenic structures
used for raising young, such as wasp nests and the balls made by dung beetles.
Despite a series of articles by Genise, Laza, Hasiotis, and others, only a few
researchers were familiar with these structures until Ichnia 2004, when Genise
and his colleagues led a field trip to the magnificent Cenozoic succession
exposed in Patagonia. Since then, it has been clear that calichnia constitute
one of the most important categories of trace fossils in paleosols.
The most complex calichnia are those made by the social activity of colonial
organisms, especially social insects such as bees, wasps, termites, and ants.
These burrow systems are commonly hybrid, incorporating parts devoted to
specialized functions such as dwelling and farming in addition to reproduction,
all with different morphologies. In general, these systems consist of densely
branched networks of open burrows in all orientations. Branching may be reg-
ularly patterned, or as irregular as the streets of a medieval city. Some are very
deep, in the case of termites extending as much as tens of meters to the water
table, and they may be very extensive. The hybrid nature of these social traces,
used for other functions in addition to reproduction, makes them different from
structures that are used exclusively for brooding. An alternative suggestion is to
use the name polychresichnia for this meaning ( Hasiotis, 2003 ).
The taxonomic study of calichnia is a specialized one that requires training
in entomology as well as ichnology. Details of the wall structure must be
observed in addition to the architecture of the whole system. Calichnia are
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