Ediacaran stratigraphy and the biota of the Adelaide Geosyncline, South Australia

Abstract

does not adequately describe the combination of passive margin and rift-based basin, but it does acknowledge the tectonics involved in accumulation of >20 km of strata, in 300 Myr (Preiss, 1987; Williams et al., 2008). Preiss (2000) subdivided the successions into the Warrina, Heysen and Moralana supergroups. These record, in turn, at least three phases of rifting during the break up of Rodinia and the Sturt glaciation, followed by evolution of the Centralian Superbasin, and the Delamerian Orogeny with rifting E and SE of the Adelaide Geosyncline in the Cambrian. Diapiric intrusions of massive and flow-banded carbonate cemented breccias with disorganised megaclasts of sedimentary and igneous rocks occur in the cores of anticlines and as apophyses along fault systems throughout the Flinders Ranges (Preiss, 1985). Diapiric breccias appear to be sourced from the Callanna Group, the basal succession of sedimentary strata in the Adelaide Geosyncline (Figure 2). Where outcropping, these carbonates, siliciclastics and volcanics show evidence of intercalated shallow marine, evaporitic and terrestrial sedimentation that accompanied the early rifting stage in the evolution of the Adelaide Geosyncline. Neoproterozoic Stratigraphy and Paleontology The Heysen Supergroup (Figure 2), consisting of the Umberatana and Wilpena groups, records the mid to late Cryogenian Sturt and Elatina glaciations (Preiss et al., 2011; Williams et al., 2008, 2011) succeeded by the Ediacaran intermittent return to warmer climates and the rise of multicellular organisms in the Ediacara biota. The base of the Cryogenian has yet to be defined. Heysen Supergroup This supergroup encompasses the entire succession in the central Flinders Ranges other than the diapiric rocks sourced from the base of the underlying Warrina Supergroup (Preiss, 1985, 1993). In the central Flinders Ranges the 4.5 km thick Umberatana Group encompasses the two main phases of glacial deposition (see Thomas et al., 2012). The carbonaceous, calcareous and pyritic Tindelpina Shale Member, of the interglacial Tapley Hill Formation, caps the Fe-rich diamictite and tillite formations of the Sturt glaciation. The upper Cryogenian glacials of the Elatina Formation are truncated by the Nuccaleena Formation at the base of the Wilpena Group and the Ediacaran System. a combination of geochemical, paleobiological and stratigraphic events, to offset the limitations of the Neoproterozoic paleontological record, is required to bracket this interval of Earth history. Fossils of the Cryogenian, Ediacaran and Cambrian document a series of unexpected quantum leaps in the size and diversity of life.

Discovery of the oldest bilaterian from the Ediacaran of South Australia

“…We propose that Ikaria is the trace maker of Helminthoidichnites and potentially the oldest, definitive bilaterian, at least as represented in the fossil record of South Australia. Kimberella, the only other taxon from the Ediacara Member that is consistently reconstructed as a bilaterian, occurs significantly higher stratigraphically than the earliest appearance of Helminthoidichnites (6,7,19,20). Similarities between taxonomic assemblages have been consistently cited as evidence that White Sea assemblage fossils from the Ediacara Member, including Kimberella, are conservatively 560 to 551 Ma (21)(22)(23)(24).…”

“…At the National Heritage Nilpena site, the excavation and reconstruction of 37-mscale fossiliferous bed surfaces reveals in situ communities of the Ediacara Biota (18). At Nilpena, and sections within the Flinders Ranges, Helminthoidichnites occurs more than 100 m below the first appearance of Kimberella (19,20). There are currently no radiometric dates to constrain the absolute age of the Ediacara Member; however, significant overlap of taxa with well-established deposits from the White Sea region of Russia indicates that these are likely between 560 and 551 million years old (21)(22)(23)(24).…”

Origin and early diversification of the phylum Cnidaria Verrill: major developments in the analysis of the taxon's Proterozoic–Cambrian history

“…). However, similarities between medusa‐like fossils and extant jellyfish probably are nonhomologous (Young and Hagadorn ), and moreover, some of these fossils were holdfast structures originally embedded in bottom sediment (Gehling and Droser ; Laflamme et al . ).…”

Fleshing out the Landscape: Two centuries of Australia’s geological heroes

“…The brilliant Martin Glaessner revived South Australian studies in paleontology and stratigraphy when appointed in 1950, culminating in the study of the Ediacara fauna, discovered in 1947 by Reginald (Reg) Sprigg (Weidenbach, 2008). Photos of such fossils are included in Figure 7 of Gehling and Droser (2012).…”