Honours Abstract (2005) Nupur SAINI

An analysis of the geology of the Razorback Beds at Mount Morgan led to a reinterpretation of the sequence. The three facies observed in the Razorback Beds - the Basal Pebbly Sandstone, Siltstone Facies and the Cross-bedded Sandstone, had previously been referred to as the Precipice Sandstone. However, this study has concluded that they correlate with a transgressive episode during the deposition of the upper Evergreen Formation and overlying fluvial Hutton Sandstone, deposited during the following regression.

An ichnofaunal assemblage, identified as prints of bipedal dinosaurs belonging to the Early Jurassic is observed in the upper horizons of the Siltsone Facies. Thirteen print morphologies were identified within the caverns, with two forms attributed to ornithopod tracks, while eleven are attributed to theropod tracks. Size calculations based on footprint morphometrics indicated a wide variation in size at hip height, with the average dinosaur size in the caverns being 70cm at hip height. Tracks observed within the caverns were used to establish the speed at which the dinosaurs were travelling while creating the prints. The speeds, all of less than 2 km/h, correlated with the environmental setting of the assemblages. That is, a lake margin, where various types of animals commonly traversed. This premise is based on several forms of information from this study, including sedimentology and footprint alignment.

Similar compositions of ichno-faunas can be observed in the globally distributed ichnofaunal assemblages belonging to the Early Jurassic of Africa, North America and Europe. The Fireclay Caverns has a higher diversity of forms observed, although this is likely due to regional differences in population. Also, non-dinosaurian forms which are observed in the global assemblages are not observed in the Fireclay Caverns.