FOREST OF FOSSIL ALGAE IN THE EDIACARA MEMBER (RAWNSLEY QUARTZITE), SOUTH AUSTRALIA

The Ediacara Biota contains fossil evidence of the first complex macroscopic organisms on the planet and is comprised of more then 50 unique and morphologically diverse genera. While the phylogenetic affinities of these fossils are debated, many are considered animals but macroalgae are not considered a common component. Excavation of 26 fossil beds ranging from 2 to 27 square meters of the Ediacara member (Rawnsley Quartzite, South Australia) at the Nilpena Station National Heritage Site allows for an unprecedented in situ examination and evaluation of these fossils.

Taxa of the Ediacara Member include iconic genera such as Dickinsonia, Tribrachidium and Parvancorina but a relatively common fossil found in the Ediacara Biota of South Australia is a general form referred to as Bundle of Filaments (BOF). There are three different morphologies of this form, the most common of which has a holdfast, stipe and bundle of filaments. The other two lack a holdfast or stipe. Specimens are up to 50 cm long. BOF is unlike any other fossils found in the other classic Ediacara biota localities however it is comparable to fossils in the Doushantuo Formation black shales of South China (Xiao et al., 2013) Although bundle of filaments is found on several of the 26 beds in South Australia, it typically occurs as a single specimen. However, on one bed, around 7 square meters in area, it occurs in a dense assemblage with over 20 specimens per square meter. Specimens show no evidence of transport (such as orientation or breakage) and are interpreted to be preserved in situ revealing a macroalgae dominated community within the Ediacara Member. Minor components occurring with these specimens include some of the smallest specimens of Dickinsonia and Sprigginamorphs.