Sedimentology of the late Neoproterozoic Patsy Springs Canyon, Flinders Ranges, South Australia

Abstract

The Neoproterozoic Patsy Springs Canyon is located within the northern portion of the Adelaide Geosyncline, South Australia. The sedimentary structures found within the canyon fill are consistent with a deep marine origin, and include syn-sedimentary marine phosphates, marine cements, sandstones with partial Bouma sequences, abundant mudstones and various mass flow deposit types (including grain flows, debris flows and slumps). Structures indicative of tidal activity (previously interpreted to be of shallow water origin) are interspersed with Bouma sequences and mass flow deposits and are here interpreted as having been produced by deep-water tidal bottom currents. Rare structures resembling hummocky cross stratification are here interpreted as similarly being of deep-water origin.

This deep water interpretation for the canyon fill contradicts previous shallow water models and alleviates the need for extraordinary changes in base level, required by such shallow water models. A deep-water submarine origin for the canyon is also more consistent with the lack of canyon-synchronous basin-wide unconformity and is more consistent with an open-ocean palaeogeography. This study has resolved some of the ambiguity surrounding the origin of the Wonoka canyons by providing sedimentological evidence to suggest that they may in fact represent ancient submarine canyons.