The recognition and implications of the
wood-boring trace fossil Asthenopodichnium
xylobiotum in Upper Cretaceous strata of Grand Staircase
Escalante National Monument, Utah
Moran,
Kelli
L., Simpson,
Edward L., Hilbert-Wolf,
Hannah
L., Wizevich, Michael C., Golder, Keenan B., and Tindall,
Sarah E., 2009, The
recognition
and
implications
of the wood-boring trace fossil
Asthenopodichnium xylobiotum in Upper Cretaceous strata of Grand
Staircase Escalante National Monument, Utah [abs]: 2009 Portland
GSA Annual Meeting (18-21 October 2009), Geological Society of
America Abstracts with Programs, Vol. 41, No. 7, p. 262.
A prolific,
macroscopic, wood-boring trace fossil is present in the Late Cretaceous
upper and capping sandstone members of the Wahweap Formation and the
Kaiparowits Formation in Grand Staircase-Escalante National Monument,
Utah. Detailed examination of these borings warrants assignment to Asthenopodichnium xylobiotum
(Thenius, 1979). The morphology and paleoenvironmental occurrence of
these Asthenopodichnium are discussed and contrasted with the similar
wood-boring ichnogenus Teredolites, which is widely considered a
marine/estuarine trace fossil.
The scoop-shaped, pouch-like traces occur as ferruginous casts of tree
bark and are found throughout both braided and meandering fluvial
deposits in the Wahweap and Kaiparowits formations. The long axis of
the trace is typically parallel with or sub parallel to the preserved
wood grain. The length ranges from 5.0 to 29.0 mm, width from 1.6 to
9.0 mm, and depths from 0.8 to 6.7 mm. Although found as isolated
individual traces, they characteristically occur in dense clusters
often with superimposed pouches.
Asthenopodichnium differs
from Teredolites by: 1) parallel versus perpendicular orientation of
the trace elongation direction relative to the wood surface, 2)
scoop-like form versus clavate shaped tube, and 3) semi-circle versus
circular cross-section. Asthenopodichnium
has been attributed to the freshwater boring of mayfly larvae (Ephemeroptera), although amphipods,
isopods and dragonflies are also possible producers. Teredolites, a clam boring, is
indicative of marine or estuarine deposits, whereas Asthenopodichnium has only been
reported in freshwater fluvial deposits. Caution must be exercised in
identifying these two distinct borings because of their specific
environmental implications.
