The Impact of Sediment Consistency on Track and Undertrack Morphology: Experiments with Emu Tracks in Layered Cement

Abstract

To demonstrate the influence of sediment consistency on track and undertrack morphology, an emu foot was impressed in four packages of layered, colored cement. The packages contained different ratios of cement to water and were subsequently sliced vertically to reveal the subsurface deformation caused by the foot, and to expose the differences in track and undertrack morphology at different degrees of firmness. A further package of alternating layers of sand and cement layers was prepared, allowing the package to be spilt along horizontal surfaces in order to investigate the undertrack formation and loss of information with depth. The experiments clearly show that increasing water content in the sediment has a strong effect on the morphology of both the true track and the undertracks.

Keywords:

• Experimental ichnology
• cement substrate
• undertracks
• tracks
• vertical sections

ACKNOWLEDGEMENTS

This study would not have been possible without significant help from Arne Nielsen with the practical aspects of the work. Karin Holst is thanked for allowing us to study her emus and for her help and expertise in handling them. Karsten Feldsted, The Danish Museum of Hunting and Forestry, Hørsholm, Denmark, provided us with a spare emu foot. Eckart Håkansson, Department of Geography and Geology, University of Copenhagen, kindly read and commented on an early draft on the manuscript, and the comments of the two anonymous reviewers was helpful and constructive.