Environmental Engineering Reference
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FIGURE 8
Intraformational unconformity within the Late Triassic Baldonnel Formation. This sur-
face is characterized by low-diversity
Glossifungites
trace-fossil assemblages that consist of
Areni-
colites
,
Rhizocorallium
,
Skolithos,
and
Thalassinoides
, as well as large, unnamed burrow networks.
The lower lithofacies consists of a variably bioclastic fine-grained mudstone-wackestone (M-W)
with low, mixed interparticle and intercrystalline porosity of
2.5%. The upper lithofacies is a
sandy bioclastic grainstone (Gr) with fine-to-medium-grained matrix and mixed interparticle, mol-
dic and intercrystalline porosity of
6-9%. These facies are separated by a discontinuous coarse-
grained lag (Lag) that infills fractures and burrows that emanate downward from this surface.
(A) Outcrop of the Baldonnel intraformation unconformity, East Carbon Creek, north-eastern Brit-
ish Columbia (Canada). Two burrows are identified, including a solitary
Skolithos
(
Sk
) and a large,
approximately U-shaped burrow (U) that is believed to be part of a complex arthropod domichnion.
(B) Polished hand sample illustrating the sharp boundary between the mudstone-wackestone
(M-W) and the coarse-grained lag that infills burrows such as the obliquely-cut
Rhizocorallium
(
Rh
) illustrated here.
including deposits dominated by inclined heterolithic stratification, cannot be
discounted.
NCD flowmedia are dominantly dual permeable in character (
Figs. 2 and 6
).
Owing in part to the association of NCD with offshore settings, the bioturbation
intensity can be quite high with burrows occupying between 30% and 90%
of the sediment volume. In offshore and shelf settings, vertical and horizontal
burrow architectures are common (e.g.,
Cruziana
and
Zoophycos
ichnofacies);
as such, NCD are likely to be highly interconnected (
Fig. 9
) and permeability
should be isotropic. In increasingly distal settings, characterized by the
Nereites
Ichnofacies, bioturbation is dominantly restricted to bedding planes and the ver-
tical permeability is not normally enhanced. The thicknesses of permeability
enhanced zones range between 5 m and tens of meters (e.g.,
Pemberton and
Gingras, 2005
). Additionally, the permeability enhancement is stratigraphically
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