TIMING OF MIDDLE AND UPPER DEVONIAN SEA LEVEL EVENTS AND CARBONATE PLATFORM (MIETTE AND ANCIENT WALL) DEVELOPMENT IN WESTERN ALBERTA

New biostratigraphic data constrain the timing of sea level events that initiated deposition of seven major Middle-Upper Devonian 3rd order genetic sequences that comprise the main architectural units of the Flume carbonate ramp and detached Miette and Ancient Wall carbonate platforms in western Alberta. Initial onlap of the West Alberta Arch (WAA) is recorded by mixed carbonates-clastics of the Thornton Creek Member (sequence 1) of the lowermost Flume Formation at Ancient Wall during the interval of the Upper subterminus conodont fauna (=Upper disparilis Zone). Flume Formation (sequence 2) carbonate ramp deposition was initiated during a late Givetian (norrisi Zone) sea level rise and continued into the early Frasnian (Montagne Noire [M.N.] Zone 4) at both Miette and Ancient Wall. Within the Flume succession (sequence 2), evidence of shallowing and exposure of a major part of the Flume Formation ramp is evident at the top of the Utopia Member, followed by resumed deepening and ramp aggradation as indicated by the upper Flume. Significant early Frasnian deepening within the interval of M.N. Zone 4 marked the initiation of isolated platform development with deposition of the Maligne-Lower Cairn formations (sequence 3). Deposition of the lower Perdrix-Upper Cairn formations (sequence 4) occurred as a consequence of pronounced deepening during middle Frasnian M.N. Zone 5. Another middle Frasnian deepening event initiated the final phase of isolated platform development recorded by deposition of the middle Perdrix Formation-Peechee Member of the Southesk Formation (Sequence 5) during the interval of M.N. zones 7?-10. Upper Perdrix/Mount Hawk Formation/Arcs-lower Simla members of the Southesk Formation (sequence 6) were deposited during M.N. Zones 11-12 and record carbonate ramp progradation across underlying basin fill at Miette. Latest Frasnian age Ronde/Upper Simla Mbr./upper Mount Hawk Formation (sequence 7) was deposited during the interval of M.N. Zone 13 and indicate initiation and continuation of carbonate ramp progradation at Ancient Wall and Miette respectively. These units mark the final phase of Late Devonian carbonate platform development prior to the Frasnian-Famennian mass extinction bioevent.