Palaeoenvironmental implications of Middle Jurassic trace fossils from the Jaisalmer Formation, India, with emphasis on the ichnogenus Asteriacites Lumbricalis von Schlotheim, 1820

Shweta S. Gurav, Kantimati G. Kulkarni, Amruta R. Paranjape, Vidyadhar D. Borkar


The Hamira Member (Bathonian) of the Jaisalmer Formation records the first marine transgression within the Jaisalmer Basin. It also contains the ichnogenus Asteriacites von Schlotheim, 1820, as documented here for the first time. This was used to refine interpretations of the palaeoenvironment. Crowded ophiuroid resting traces, Asteriacites lumbricalis, occur in a silty limestone unit 1 m thick. This is preceded by a monospecific assemblage of Diplocraterion parallelum towards the base of this unit, while towards the top there is an assemblage, comprising Gyrochorte comosa, Protovirgularia rugosa, Rhizocorallium commune and Rosselia socialis. Colonisation by the Asteriacites trace makers occurred in a shallow-water, marginal-marine, normal-salinity, fully oxygenated, high-energy setting with steady rates of sedimentation. From an ichnological perspective, the sequence investigated shows a shift in environmental conditions from the middle shoreface to the off shore transition zone. Addressing the Asteriacites/Heliophycus nomenclatorial dilemma, Knaust (2012) suggested that the generic designation Asteriacites should be retained. His view was found to be appropriate and supported to avoid further confusion.

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