Trace fossils – Knowledge and References

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Petroleum Geological Survey

Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021

‘Trace fossils’ are not fossils themselves. They represent the past activities of some animals. The animal can be traced back by observing certain marks left behind by organisms on sedimentary rock. The marks left are foot prints, bores, barrows, tracks and trails and bite marks. The life of the animal can be interpreted by examination of these trace marks.

Zebra rock and other Ediacaran paleosols from Western Australia

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Journal Information

Published in Australian Journal of Earth Sciences, 2021

G. J. Retallack

Desiccation cracks have a V-shaped profile in clay (Weinberger, 2001), and several examples in shales of facies IR of the Johnny Cake Member of the Ranford Formation have been illustrated by Lan and Chen (2013). Similar tapering cracks were also seen in the dolomitic sandstones of the upper Moonlight Valley Tillite and Jarrad Member of the Ranford Formation (Figure 5b, d). These sandstone cracks emanate from the most hematite-rich tops of sandy beds but are filled with fine-grained white dolomitic sandstone. How sand can crack like clay is explained by Prave (2002) as owing to abundant hydrated microbiota, like that of a thick microbial earth soil rather than thin microbial mat (Retallack, 2012a). This idea is supported by co-occurring microbially influenced sedimentary structures (MISS of Noffke, 2010), such as the microbial trace fossil Rivularites repertus (Retallack & Broz, 2020), which has complex, multiple fills of shallow cracks (Figure 5c). A comparable phenomenon is oscillating desiccation cracks of modern supratidal flats (Noffke, 2010), which is the depositional setting envisaged by Lan and Chen (2013).