Abstract

Although at least 38 Precambrian paleosols have been reported in Canada, few have received the attention afforded most other geological phenomena. The most intensively studied of these are widely distributed Early Proterozoic paleosols associated with the sub-Huronian and Matonabbee (new name) unconformities. Criteria that have been most useful in identifying Precambrian paleosols in Canada include macrostructures (ascending protolith disruption, saprolith, and corestones), micromorphology (sepic texture and peds), mineralogical changes (dissolution, transformation), geochemical signatures (ascending depletion of some elements, characteristic weathering indices), and distinctive colour contrast. Diagenetic mechanical and geochemical overprinting of the paleosols, evident in many Canadian examples, includes paleosol compaction, veins cutting pedogenic features, and widespread alkali and alkaline earth element metasomatism. Metamorphism and deformation also tend to mask pedogenic features, as attested by the scarcity of documented occurrences of medium- to high-grade metamorphosed Precambrian paleosols in Canada. The recognition of other Precambrian paleosols in metamorphosed terranes could be aided by systematic detailed studies of rocks beneath unconformities to assess geochemical gradients in metamorphic minerals rich in Si, Al and Fe. Geochronological constraints on Precambrian paleosol development might reinforce previously proposed stratigraphic correlations, suggest new correlations, and serve to delimit times and areas of relative tectonic stability and subaerial exposure.

You do not currently have access to this article.