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diagenesis most commonly occurs in and around generations of interpenetrating
trace fossils. Consequently, the heterogeneity in burrow-mottled carbonates
is high. Although a dual-permeability network is generally produced, dual-
porosity systems are also present.
Burrow-associated dolomite is commonly present in Paleozoic carbonates.
Diagenetic heterogeneities are exemplified by the Ordovician Chazy Group
(
Mehrtens and Selleck, 2002
), Devonian strata in western Canada (
Beales,
1953; Corlett and Jones, 2012; Gingras et al., 2004b
), the Late Ordovician
Bighorn Dolomite in Wyoming (
Zenger, 1992, 1996
), and the Ordovician
Yeoman Formation in the Williston Basin (
Kendall, 1977; Pak, 2003
) of North
America. Younger examples are provided in
Pedley (1992)
. The depositional
environments range from platformal offshore (Palliser Formation) to restrict
offshore. The successions result in significant volumes of altered/affected
strata. Thicknesses typically approach 10 m, however, more or less continuous
zones may be more than 100 m thick. Likewise, the areal extents of these ramp-
and platform-associated strata are potentially extensive, generally falling
between one and hundreds of square kilometers.
4.3.5.1 Red River Formation (Ordovician), Saskatchewan and
Manitoba, Canada
The best-characterized example of burrow-associated diagenesis in North
America is the Tyndall Stone, a dolomitic-mottled limestone quarried in
Manitoba, Canada. The Tyndall Stone is assigned to the Ordovician Selkirk
Member of the Red River Formation (
Kendall, 1977
). Similarly, mottled lime-
stones comprise the subsurface equivalent Yeoman Formation in south-eastern
Saskatchewan (
Kendall, 1975
). The Selkirk Member and the Yeoman Formation
accumulated as an epicontinental carbonate platform in the Williston Basin. The
most distinctive feature of the Tyndall Stone is the presence of pervasively
distributed, dolomitized, branching trace fossils (
Gingras et al., 2004b; Kendall,
1977
). Spot-permeametry data from the Tyndall Stone show that the average
permeability of the matrix is 1.65 mD, and the average burrow permeability is
19.2 mD (i.e., a dual-porosity system) (
Gingras et al., 2004b
;
Fig. 4
, inset).
Oil production from the Yeoman Formation in Saskatchewan is primarily from
the dolomitic phases that occur in layers between 1 and approximately 10 m thick.
4.3.5.2
Lonely Bay Formation (Devonian), Northwest Territories,
Canada
Corlett and Jones (2012)
show that the Lonely Bay Formation contains an
intensely bioturbated facies, characterized by dolomite- and calcite-cemented
burrows. The calcite-cemented burrows were formed proximal to the shoreline
and the dolomite-cemented burrows in distal units. Within the calcite-cemented
burrows, the primary sedimentary and ichnological fabric was preserved. The
sedimentary fabric associated with the dolomite-cemented burrows appears
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