Ichnofacies of the Stairway Sandstone fish-fossil beds (Middle Ordovician,Northern Territory,Australia) |
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Authors: | Neil S. Davies Ivan J. Sansom Robert S. Nicoll Alex Ritchie |
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Affiliation: | 1. School of Geography, Earth and Environmental Sciences, University of Birmingham , Edgbaston, Birmingham B15 2TT, UK neil.s.davies@dal.ca;3. School of Geography, Earth and Environmental Sciences, University of Birmingham , Edgbaston, Birmingham B15 2TT, UK;4. Department of Earth and Marine Sciences , Australian National University , Canberra, Australian Capital Territory 0200, Australia;5. Australian Museum , Sydney, New South Wales 2010, Australia |
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Abstract: | The Stairway Sandstone is a 30–560 m thick succession of Middle Ordovician siliciclastic sedimentary rocks within the Amadeus Basin of central Australia, deposited in the epeiric Larapintine Sea of northern peri-Gondwana. The Stairway Sandstone is significant as one of only two known Gondwanan successions to yield articulated arandaspid (pteraspidomorph agnathan) fish. Herein we use the ichnology of the Stairway Sandstone to reveal insights into the shallow marine habitat of these early vertebrates, and compare it with that of other known pteraspidomorph-bearing localities from across Gondwana. The Stairway Sandstone contains a diverse Ordovician ichnofauna including 22 ichnotaxa of Arenicolites, Arthrophycus, Asterosoma, Cruziana, Didymaulichnus, Diplichnites, Diplocraterion, ?Gordia, Lockeia, Monocraterion, Monomorphichnus, Phycodes, Planolites, Rusophycus, Skolithos and Uchirites. These ichnofauna provide a well-preserved example of a typical Ordovician epeiric sea assemblage, recording the diverse ethologies of tracemakers in a very shallow marine environment of flashy sediment accumulation and regularly shifting sandy substrates. New conodont data refine the age of the Stairway Sandstone to the early Darriwilian, with ichnostratigraphic implications for the Cruziana rugosa group and Arthrophycus alleghaniensis. |
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Keywords: | arandaspid Arthrophycus Cruziana ichnology ichnostratigraphy Ordovician |
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