Ichnofossils from the Fort Member (Middle Jurassic), Jaisalmer Formation, Rajasthan

An ichnoassemblage from the Fort Member, Jaisalmer Formation, occurring in a hill north of the city of Jaisalmer is described. It comprises Arenicolites tenuis isp. nov., Bichordites isp., Planolites isp., Rhizocoralliurn irregulare Mayer, Rhizocorallium jenense Zenker, Taenidium serpentinurn Heer and Thalassinoides isp. Overall paucity of repichnia in an ichnoassemblage vis-a-vis noticeable dominance of domichnia and fodinichnia implies abundance of detrital nutrients. Host rocks yielding this ichnoassemblage are current bedded calcarenite showing fine shell hash along current beds and clayey limestones with presence of small, lenticular storm bed intercalations. They suggest near-shore, moderate-to strong-energy marine conditions rich in organic nutrients, supporting inferences drawn on the basis of trace fossils. The beds containing this ichnoassemblage are assigned ages ranging from Bathonian to Callovian, and hence considered here Middle Jurassic.