Integrated Ichnology, Sedimentology and Stratigraphy of the Lower Cretaceous Sparky Alloformation (Mannville Group), Lloydminster Area, west-central Saskatchewan, Canada

Abstract

Abstract The Lower Cretaceous Sparky Alloformation in the Lloydminster area of Saskatchewan, Canada consists of a complex succession of deltaic and marginal-marine deposits reflecting progradation towards the north and northwest (N-NW). The bounding discontinuities used to delineate the Sparky Allomember correspond to marine flooding surfaces (FS). Based on the integration of ichnological and sedimentological characteristics of succession, ten discrete facies have been identified. These are combined into five recurring facies associations. Facies Association 1 (FA1) comprises sediments deposited below fairweather wave base but above storm wave base. Facies associations 2 and 3 (FA2 and FA3) coarsen upward and represent the progradation of wave- and storm-dominated shorefaces as well as mixed river- and wave-influenced deltas, respectively. Facies Association 4 (FA4) typically cuts through FA3, and displays a fining-upward trend, and is interpreted as distributary channel deposits. Complete cycles of FA2 and FA3, wherein the tops of the cycles have not been removed by downcutting channels, are capped by coastal plain/delta plain deposits of Facies Association 5 (FA5). The Sparky Alloformation terminates at an upper contact marked by renewed marine transgression and the formation of a regionally extensive transgressive surface of erosion (TSE). Three coarsening-upward cycles are identified within the Sparky Alloformation, each bounded by allogenically produced flooding surfaces. These units, termed Lower, Middle and Upper allomembers, are characterized by wave- and storm-dominated shorefaces and associated mixed river-and wave-influenced deltaic successions reflecting progradation towards the N-NW. The Sparky Alloformation consists of sediments deposited during periods of pronounced progradation and corresponds to a highstand systems tract.