| Quaternary geological mapping, architectural-element analysis and ground penetrating radar profiling indicate that the Nakina moraine, near Longlac, northern Ontario, formed as a grounding line moraine, dominated by coalescing, ice-marginal, high-energy shoal-water deltaic systems.; Deltaic topset bed assemblages resemble channel fill complexes associated with shallow, flashy, low-sinuosity braided rivers. Sediment transport and deposition under high-energy conditions is indicated by the presence of massive beds and sigmoidal to planar-laminated strata, which formed in the transition zone between dune and upper stage flow-regime. Assemblages of low-angle, trough and planar cross-stratified sediment are interpreted as gently dipping deltaic foreset elements. These reflect rapid deposition from hyperconcentrated suspensions with minor redeposition by sediment gravity flows. Stacks of silty, fine to medium sand, with planar-laminae, sinusoidal drapes, and type A and B ripple-drift cross-lamination, are interpreted as bottomset bed deposits. (Abstract shortened by UMI.)... |
