Submarine canyons and sea-level fluctuations in the late Ediacaran: evidence from the Ediacara Member, South Australia

The rise and diversification of metazoans in the late Ediacaran have been linked to global sea-level changes. However, the regional record of these changes remains ambiguous. Here, we investigate the origin of an unconformity at the base of the Ediacara Member in South Australia that hosts one of the most diverse assemblages of the Ediacara Biota. The unconformity is traceable throughout the Flinders Ranges, creating deep southeast-oriented valleys reaching 280 m in depth and more than 6 km in width. The base of their infill is marked by rip-up clast breccias overlain by gravity-flow deposits interbedded with deep-water siltstone. The succession shallows upward and is capped by wave-reworked sediments that are correlative throughout the basin. We propose that this basal unconformity formed through the propagation of shelf-incising submarine canyons, potentially during a global lowstand. A significant transgression led to their infill and deposition of the Ediacara Member, allowing preservation of the diverse assemblage of the Ediacara Biota.