The Sedimentary Record of Mantle Plume Uplift Preceding Eruption of the Neoproterozoic Natkusiak Flood Basalt

Abstract

Strata of the Neoproterozoic Shaler Group on Victoria Island in NW Canada reveal stratigraphic and sedimentological features that are interpreted to be a response to differential crustal uplift immediately preceding emplacement of the 723 Ma Franklin gabbro sills and their extrusive equivalents, the Natkusiak Formation flood basalts. Volcanism was coeval with sedimentation, as indicated by loading features developed on the Kuujjua Formation, a fluvial braidplain quartzarenite that underlies the lowermost basalt flow of the Natkusiak Formation in the SW part of Minto Inlier. The Kuujjua Formation represents the top of an emergent cycle that began with deposition of intertidal carbonates followed by supratidal sabkha carbonates and sulphate evaporites of the underlying Kilian Formation. The Kuujjua Formation thins and pinches out toward the northeast, and there is erosional beveling of the upper Kilian beneath it. In the NE part of Minto Inlier, the Kuujjua and upper Kilian are absent and the Natkusiak Form...