Porosity and Permeability in Bioturbated Sediments - Trace Fossils as Indicators of Sedimentary Environments - page 823

4.3.1.2 Hawiyah Portion of the Ghawar Field (Jurassic), Saudi Arabia
SCD have also been reported from carbonate strata. Pemberton and Gingras
(2005) presented data from the Hawiyah portion of the Ghawar Field, where
a distinct interval of stacked Glossifungites -Ichnofacies-demarcated surfaces
occurs. The Ghawar example is rather extreme as it is characterized by Thalas-
sinoides with 1-2 cm in burrow diameter that penetrates up to 2.1 m below the
surface. The burrow-encapsulating matrix is composed of low-permeability
micritic calcite. The burrow fills and the overlying strata consist of detrital
sucrosic dolomite, providing a biogenic flow system for some of the Ghawar
reservoirs. The permeability of the burrow fill is high enough to cause the bio-
genic flow medium to locally develop into high permeability (also known as
“Super K”) stratigraphic levels.
4.3.1.3 Baldonnel Formation (Triassic), British Columbia, Canada
Outcrops of the Baldonnel Formation display discontinuity surfaces delineated
by granule/pebble lags, substrate-controlled trace-fossil assemblages, and pro-
nounced diagenetic alteration of underlying strata in the Carnian Baldonnel For-
mation at Williston Lake, north-eastern British Columbia. Many of these
surfaces are characterized by well-developed, low- to moderate-diversity
trace-fossil assemblages attributed to the Glossifungites Ichnofacies that locally
are overprinted by sparse, low-diversity trace-fossil assemblages characteristic
of the Trypanites Ichnofacies, together comprising a polygenetic SCD ( Fig. 8 ).
Fabric-selective (interparticle, intraparticle, and biomoldic) and non-fabric-
selective (vuggy and burrow) porosity are best developed in them, in association
with bioclastic packstone and grainstone beds immediately beneath discontinu-
ity surfaces, particularly those characterized by Glossifungites assemblages.
Complex depositional/diagenetic relationships occurred where substrata char-
acterized by moderately diverse Skolithos or proximal Cruziana trace-fossil
assemblages were buried, exhumed, colonized by firmground-preferring
infauna, lithified, colonized by hardground-preferring infauna, and reburied.
Diagenetic alteration occurred via fluid penetration through burrows during,
and shortly after, hardground formation.
4.3.2 Non-Surface-Constrained Discrete Heterogeneities
Non-surface-constrained discrete (textural) heterogeneities (NCD) comprise
sharply defined burrows that are encased in a fine-grained matrix. Like
surface-constrained heterogeneities, this architecture is common in clastic strata
where sand-filled burrows descend into mudstone. However, NCD are laterally
and vertically distributed (i.e., burrows originate from several depositional sur-
faces), and the bioturbation intensity must be high enough to afford connectivity
in three dimensions. This type of permeability enhancement is most common in
strata that accumulated in offshore settings, although lagoon and bay settings,