Page 143 - Carbonate Facies in Geologic History

130 The Advent of Framebuilders in the Middle Paleozoic

STlUCTURE CONTOURS ON RESTORED
TOP OF l rDUC FORM .... TlON

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--------;oo;;:~-_-___ -:_:;.~-:~~~~-___ ----
Fig.IV-20. Surface of Redwater offshore carbonate bank, Alberta basin, Canada. From Klo-
van (1964, Fig. 5). Note wide central depression which may be an artifact of later compaction
and not depositional. Contours are in feet. The grid marks townships which are 6 miles square.
Illustration with permission of author and Canadian Society of Petroleum Geologists

ups may be hundreds of meters but platform-bank relief is variable from a few
meters to 200 or so. Many buildups rise from previously formed, even wider
platforms indicating that they may be residual organic accumulations surviving
regional deepening of the sea and/or clastic influx by keeping "heads above
water." The presence of multiple trends across the Alberta basin indicates no
major response to prevailing winds and currents. The organic community was
able to thrive almost as well within a semi-protected basin on its open sea side.
The intervening basinal areas of Alberta were areas of slightly deeper and
considerably muddier water than the carbonate producing banks. The first trans-
gression after the Elk Point evaporite period, resulted in widespread deposition of
a fossiliferous gray shale and limestone (Waterways Formation); at this time
scattered carbonate bank development became extensive. The best known car-
bonate complex of this earliest time is embodied in the Swan Hills Formation.
Both of these units are subdivisions of the Beaverhill Lake Group of early
Frasnian age. These early Frasnian buildups are regionally north and west of the
maximum carbonate development of later Frasnian time. Before the major stage
of buildups in W oodbend time and after construction of the Cooking Lake Plat-