Was Earth really a snowball? Detailed facies analysis and 3D modelling of the Elatina Formation, Pichi Richi Pass, Flinders Ranges, South Australia

Abstract

The Elatina Formation is exposed in outcrops throughout South Australia, most notably represented by distinct glaciogenic deposits in central and northern Flinders Ranges. As the formation reflects low latitude glaciation, it has previously been used as a benchmark study in the development of the Snowball Earth hypothesis. Pichi Richi Pass in the central Flinders Ranges is an excellent example of the Elatina Formation, however significant uncertainties exist regarding the local sequence stratigraphy and interpretation of the depositional environments. A detailed facies analysis and 3D model of the Elatina Formation at Pichi Richi Pass was established to demonstrate the variability and distribution of the depositional system. The Elatina Formation consists of four lithostratigraphic units, with eight facies identified within two of the units. The facies were established from lithological properties, and then associated based on descriptions and interpretation of their depositional processes. The results reflect thick non-glaciogenic layers interbedded with thin glaciogenic layers. The non-glaciogenic layers were deposited in coastal, deltaic and fluvial settings, while the glaciogenic units were deposited in a glaciofluvial environment. As most of the Elatina Formation in Pichi Richi Pass appears to be deposited under moving water, it suggests that the palaeoenvironment of the Elatina Formation is not consistent with prolonged glacial conditions like that of Snowball Earth. Rather, it denotes variable glacial periods characterised by glacial advance and retreat.