Submarine planation of carbonate substrate on the Laurentian continental shelf (upper Cambrian, Notch Peak Formation, Utah)

Widespread erosional surfaces record the cumulative effects of physicochemical processes operating at regional to basin scales and therefore constitute critical archives of paleoenvironmental conditions and basin evolution. This study investigates an extensive planar erosional surface within upper Cambrian deposits from the cratonic margin of Laurentia, to characterize factors favoring subaqueous substrate abrasion in carbonate-dominated, lower Paleozoic epicontinental shelves. The surface, traced over an area of ~1500 km 2 , exhibits a consistently flat geometry, with clear evidence of truncation of the underlying facies both at the macroscopic and microscopic scale. Formation in subaqueous conditions is inferred from the absence of karst-related features or relief reflecting subaerial drainage systems, no clear evidence of meteoric diagenetic overprint, and direct superposition of fully subtidal deposits with no intervening continental facies. New carbon isotope data corroborate existing biostratigraphic and chemostratigraphic evidence that provides chronostratigraphic constraints on the development of the surface. Facies analysis suggests that the influx of fine siliciclastics and sustained wave motion of sediment on an early-cemented carbonate substrate, consisting of lime mudstone, stromatolitic boundstone, and grainstone to rudstone deposits, effectively “sandpapered” a broad sector of the shelf. Subaqueous mechanical wear leading to extensive substrate planation is maximized by factors including carbonate-dominated substrate, early submarine cementation, flat antecedent topography, availability of sand-sized particles without complete substrate coverage by sediment, and vigorous wave regime. These findings provide insight on formation of submarine erosional surfaces in lower Paleozoic epicontinental seas and a rock record perspective to inform research on subaqueous bedrock abrasion.