Palaeoecology and affinities of Nummipera eocenica burrows from the middle Eocene (late Lutetian) of Jiroft area, Central Iran

Abstract

Marly nummulite limestones of the Tabas Block of central Iran (Jiroft area) contain armoured burrows of the problematic ichnofossil Nummipera eocenica. These burrows are covered with tests of Nummulites cf. praelyelli and Nummulites deshayesi. The studied traces most closely resemble morphotype C of N. eocenica from the Eocene of the Tatra Mountains. The Iranian specimens occur in marly limestone that was deposited in a moderate to low energy environment on the shallow part of a ramp, although occasionally sediments indicate wave action and storm influence in high-energy conditions. The trace maker may have selectively used microspheric forms or B-forms of Nummulites by means of its appendages. Moreover, A-forms are dominant in accumulations of foraminifera in the studied section, but the trace maker obviously preferred the thinner test B-forms that are mainly saddle and flat shaped forms (Nummulites cf. praelyelli) over the lenticular and thick test forms (e.g. N. deshayesi). In addition to the protection against the episodic hydrodynamic activity, it is possible that one of the main reasons behind the reinforcement of burrow walls may have been the need for protection against predators. The trace makers were likely crustaceans or alternatively onuphid polychaetes.