ABSTRACT
The Ancient Wall buildup is one of several atoll-like carbonate accumulations occurring in the Upper Devonian of western Canada. The buildup and associated sediments comprise five facies: platform facies of thin laterally persistent biostromal calcarenites; buildup interior of bioclastic lime sands and mudstones; buildup rim of structureless dolomite and discontinuous algal-coral-stromatoporoid boundstones; foreslope of interbedded normal basin sediments and buildup-derived detritus including allodapic carbonates, rudites, and large allochthonous blocks of the buildup rim which were moved downslope by highly concentrated debris flows; and basin of thin-bedded argillaceous lime mudstones, shales, silty carbonates, and siltstones.
Sea-level changes exerted dominant control on the development of the complex. A wide range of diagenetic features are present, the most striking being cementation, silicification and dolomitization. Criteria indicating proximity to similar subsurface buildups include recognition of the foreslope facies, increasing carbonate content of basin formations and thickness relationships.
