Feltrin, Leonardo, and Oliver, Nicholas H.S. (2014) Timing and origin of megabreccia and folds along the Early Middle Cambrian margin of the Georgina Basin, Australia. Carbonates and Evaporites, 29 (1). pp. 3-31.

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Abstract

Megabreccia and related folds are two of the most interesting features of the Lawn Hill Outlier, a small carbonate platform situated in the northeastern part of the Georgina Basin in Queensland, Australia. Field studies and stable isotopic data were used to assess the timing and origin of folds and megabreccias in this carbonate plateau, and understand its possible relationship to an asteroid impact. Together with field and isotope data, the reconstruction of the sequence of events that led to the cratonization of the Centralian Superbasin supports a synsedimentary timing of formation for the folds and breccias. Some of the brittle faulting and veining accompanying strain localisation within the Thorntonia Limestones may represent, however, post-sedimentary, syntectonic deformation, possibly linked to the Late Devonian Alice Springs Orogeny. An origin for the folding and megabreccias linked to an asteroid impact cannot be completely discounted. Nevertheless, observed field relationships concerning the spatial distribution and typology of breccias occurring in basement and cover agree with stable isotopic signatures, suggesting that multiple intrabasinal processes contributed to platform destabilisation. Processes such as karstification, solution collapse, and fault reactivation, were the most likely mechanisms responsible for the formation of intrastratal breccias and slump folds in the Lawn Hill Outlier.

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