Simulation of Variables Controlling Carbonate Geometry and Facies: Judy Creek Reef, West Canada--An Example

David M. Scaturo, Christopher G. St. C. Kendall, Jack C. Wendte

Two of us (D.M.S. and C.G.St.C.K.) have been simulating parameters which control evolution of carbonate facies and their geometry. We tested our simulation with a three-dimensional, sequence-facies model of Judy Creek reef complex provided by the third author (J.C.W.).

This complex consists of repeated shoaling-upward sequences. Facies of all but the final cycle consist of a marginal reef and interior lagoon with smaller order, subtidal to tidal-flat cycles. The commonly sharp bases of major cycles mark abrupt shifts in facies belts and, with the exception of the final cycle, lack evidence of widespread subaerial exposure, arguing that reef development was strongly governed by episodic increases in rate of relative sea level rise.

Five major cycles of reef growth occur. The first has a marginal reef facies that prograded and then aggraded. In cycles two through four, the disposition of the reef margin facies vary from upbuilding to backstepping to stacked prograding cycles, depending on position in the reef complex. The fourth cycle was terminated by a lowering of relative sea level and subaerial exposure of the shallow-water reef. The fifth and last phase of growth occurred as sea level rose and formed up to 30 m of backstepping, ramp-bounded shoal sequences.

Our simulation of the Judy Creek complex modeled sediment geometry as a function of eustasy, tectonic subsidence, and carbonate production (as controlled by water depth and reef position). Iterative testing of input variables reproduced the reef history.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.