Ichnology and palaeoecology of the Neogene Beaumaris Sandstone: a reconstruction of palaeoenvironments using trace fossils as interpretive tools.

The recent discovery of trace fossils in parts of Beaumaris Sandstone presented a new aspect to the paleontology of the strata. The work that described this discovery was limited in its scope and provided information only on a small area of the outcrop. What was still unknown was the extent of the trace fossils, whether new types remained to be discovered and if they were sufficiently numerous to be used as a stratigraphic tool. To ascertain this, extensive field surveys was conducted, and representative sections were identified, with an emphasis on those areas previously thought to be unfossiliferous. The data from selected sites along the length of outcrop was analyzed, and the occurrence of different fossils (both ‘body’ and ‘ichno’) used to divide Beaumaris Sandstone into distinct units. Undescribed ichnospecies were encountered during this process, and used as a primary tool in unit construction. Ichnofossils were found to be present in large numbers and some variety, and in a state of preservation that renders them good subjects for study.<br><br> Fossil crab and worm burrows, preserved in Goethite, formed the larger part of the previously undocumented types. Fossil wood casts were recorded along the whole length of outcrop. The discovery of an undescribed species of Psilonichnus represents the first record of this ichnogenus in Australia. A small occurrence of sea anemone trace fossils was found. These trace fossils (Bergaueria) have only known in Australia from Pre-Cambrian rocks prior to this, and are very rare worldwide, due to the highly specific conditions necessary for their formation. The combined use of fossil casts and burrows as stratigraphic tools is confirmed as being of equal utility as more traditional methods, presenting a valid alternate method of research.