Wind-generated tool marks resembling trace fossils in a shallow estuarine environment

Abstract

A suite of tool marks were observed in the seaward section of a small estuary on the south coast of New South Wales. The marks were formed through wind-generated waves dragging Eucalyptus leaves and Casuarina fronds over the backshore sands that separate the closed estuary from the sea. Some of the marks formed through the process of tilting, which has not previously been recognised in an Australian setting. A number of the more complex marks closely resemble trace fossils left by fish, and differentiation between the two in the sedimentary record could be difficult. If correctly identified as tool marks, then they could give a spurious estimate of palaeoflow direction, as they correspond to the orientation of the prevailing winds at the time of formation. This study highlights the need for judicious interpretation of ambiguous grooves in the sedimentary record.

Key words:

• tool mark
• estuary
• wind
• tilting mark
• trace fossil
• palaeoflow direction

Acknowledgements

I would like to thank Simon Debenham, Andrew Heap, Brian Jones and an anonymous reviewer, whose helpful comments greatly improved the manuscript. I would also like to thank Peta Jane and Chloe Jones, for assisting with the fieldwork. Published with the permission of the Chief Executive Officer, Geoscience Australia.