Mantle plume uplift in the sedimentary record: origin of kilometre-deep canyons within late Neoproterozoic successions, South Australia

In South Australia, canyons 200-250 km long are incised to depths of c. 1.5 km in late Neoproterozoic (after c. 590 Ma) marine deposits of the Adelaid e fold belt and canyons 90 km long and 700 m deep occur in correlative mari ne strata of the Officer Basin 1000 km to the NW. In the Adelaide fold belt , the isotopic signature of limestone veneering canyon walls, canyon sinuos ity and sedimentary structures in canyon fill suggest that the canyons were cut subaerially and filled by shallow-water marine deposits during coastal onlap. Eustacy cannot account for the kilometre-scale change in sea level required for subaerial canyon erosion, and chemostratigraphy and the lack o f evaporites at that stratigraphic level in southern Australia argue agains t a Messinian-style drawdown. In each region, uplift and crustal extension preceding or coeval with canyon incision are indicated by a regional unconf ormity, turbidite or mass-how deposition, and extensional faults. These fea tures and canyon incision may be explained by regional uplift above a risin g mantle plume over a distance of >1000 km in southern Australia. Flood bas alt volcanism in the Officer Basin tentatively dated at 563 +/- 40 Ma may h ave followed this uplift. Mantle plume uplift is expressed in the sedimenta ry record by emergent trends in facies, regional thinning, regional unconfo rmities, turbidites, gravity slides, normal faults and incised canyons and palaeovalleys.