Polygenetic (Polyphase) Karsted Hardground Omission Surfaces In Lower Silurian Neritic Limestones: Anticosti Island, Eastern Canada

Research on Anticosti Island, Québec, reveals the existence of polygenetic (polyphase) karsted hardground omission surfaces in Lower Silurian Chicotte Formation limestones. These surfaces, formed through combined marine and meteoric diagenesis, include planar erosional bedding tops, scalloped erosional surfaces, knobs, ridges, swales at bedding contacts, and paleoscarps. The study proposes that these features are linked to specific diagenetic–depositional processes in terrestrial–peritidal–shallow neritic zones, influenced by fluctuations in relative sea level. These processes include karst corrosion, peritidal–shallow subtidal erosion, subtidal seawater flushing and cementation, and shallow subtidal deposition. The surfaces are interpreted to have been the result of initial extensive shallow-water synsedimentary lithification forming hardgrounds, which were planed by inner-neritic abrasion, altered by exposure and subaerial corrosion, and buried by sediments as sea level rose again. This succession was repeated several times, resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. The study also notes that these Silurian inner-neritic–strandline omission surfaces are temporally unique, part of a suite of marine omission surfaces mostly found in early to middle Paleozoic neritic carbonate sedimentary rocks.

James, N. P., Desrochers, A., & Kyser, T. K. (2015). Polygenetic (Polyphase) Karsted Hardground Omission Surfaces In Lower Silurian Neritic Limestones: Anticosti Island, Eastern Canada. Journal of Sedimentary Research, 85(9), 1138–1154. https://doi.org/10.2110/jsr.2015.71