Geological setting of exceptional geological features of the Flinders Ranges

Abstract

The Flinders Ranges in South Australia mainly comprise folded Neoproterozoic to Cambrian sedimentary rocks of the Adelaide Geosyncline, with local inliers of its Paleo–Mesoproterozoic igneous and metamorphic basement. A widely varied range of exceptional geological features is displayed in the rocks of the ranges and forms the basis of a proposal for recognition as a UNESCO World Heritage Serial Property. Abundant fossil evidence is revealed of the evolution and diversification of Earth’s early life forms, and these rocks showcase the increasing complexity of life with time, from single-celled life forms and stromatolites, organo-sedimentary structures resulting from microbial life-activity, through multi-cellular organisms such as the Ediacara biota and builders of giant reefs to animals with shells and burrowing, predatory and scavenging behaviour in the early Cambrian. This took place during a time span of over 300 million years of extreme climatic oscillations and fluctuations of ocean and atmospheric composition, punctuated by two global glaciations. The geological evolution of this basin was modified by its radiogenic, unstable basement and mobile salt tectonics and diapirism, which provide a unique natural laboratory for studies of these aspects and, particularly, the possible genetic and causative relationships between them. Added to this unique history are an interval of flood basalt extrusion, sedimentary ironstone deposition accompanying glaciation, a debris layer from a bolide impact and deep canyon incision. Indeed, this unique basin evolution history is likely to have influenced the progress of its biotic evolution. Further, the thermal effects of the radiogenic basement have continued until the present day, as revealed in Paleozoic magmatism, hydrothermal features and hot springs. The Ediacaran, the first geological period defined in the southern hemisphere, and the first for over 100 years, has its defining GSSP (Global Stratotype Section and Point) in the Flinders Ranges.