Page 144 - Carbonate Facies in Geologic History

Alberta Basin Banks 131

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1050

1100

1150

1200

f ·.:::;<YORE'REE' r-1REEF DETRITUS ~~HON-SKElETAl
•••. : ••• :: MEGAlODOH FACIES (2) L....:...J W/MA"M: STRCM. (~) ~CALCARENITES _LAMINITE Jlll BAC~ REEF
~REEF DETRITUS-13) ~ r--lDENSE, eOREO. FACIES
AB
T
~ AR STROH. FACIES ~ ORGANIC REEF (4) AMPHIPORA FACIES III L---.J CALCARENITES
UL
Fig.IV-21. Composite cross section of Upper Redwater reef complex showing facies across
eastern edge of the large offshore bank in the Alberta Basin, Canada. From Klovan (1964,
Fig. II). Great vertical exaggeration; the true dip of eastern slope is only about 2 degrees. The
interior westerly dip between Imperial Eastgate and Imperial Simmons wells is possibly an
artifact of compaction. Illustration courtesy of author and Canadian Society of Petroleum
Geologists

form, thin deposits of black-brown calcareous shale (Duvernay) accumulated in
the basins. This time of basin starvation coincided with considerable upward
growth of the surrounding banks. A gray-green shale (Ireton) filled in the reef-
lined basins which may have been 200 m deep by this time (see Table IV-3).
Most of the buildups are dolomitized, a process responsible for much of the
porosity, permeability, and good reservoir quality. Several of the limestone banks
have been studied in great detail both paleontologically and petrographically.
The microfacies types listed above in this chapter derive mainly from such study.
Most of the Swan Hills banks have been described (Fischbuch 1968; Murray,
1966; Jenik and Lerbekmo, 1968) and complementary studies have been made on
Wood bend strata in the Canadian Rockies (e.g., Dooge, 1966; Dolphin and Klo-
van, 1970; Noble, 1970). A classical study is by Klovan (1964) of the Redwater