ASGP (2014), vol. 84: 249-257
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
Geology and Palaeontology Group, Agharkar Research Institute, G.G. Agarkar Road, Pune 411 004, India; e-mails: shwtgrv at gmail.com, kantimatik at gmail.com, amrita.paranjpe at gmail.com, vidyadharborkar at yahoo.co.in
Gurav, S. S., Kulkarni, K. G., Paranjape, A. R. & Borkar, V. D., 2014. Palaeoenvironmental implications of Middle Jurassic trace fossils from the Jaisalmer Formation, India, with emphasis on the ichnogenus Asteriacites Lumbricalis von Schlotheim, 1820. Annales Societatis Geologorum Poloniae, 84: 249–257.
Abstract: 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.
Manuscript received 5 May 2014, accepted 20 October 2014
