PARURGONINA VALANGINIANA N. SP. FROM THE VALANGINIAN OF SW IRAN (ZAGROS ZONE): THE FIRST CRETACEOUS RECORD OF THE GENUS

Abstract

The new larger benthic foraminifer Parurgonina valanginiana is described from the Valanginian deposits of the Fahliyan Formation of southwestern Iran (Zagros Zone). It is separated from the uppermost Oxfordian-lowermost Tithonian generotype P. caelinensis (Cuvillier et al.) by a distinct time gap. The Lower Cretaceous specimens exhibit a larger embryonic chamber whereas the internal structural and other biometric data are generally in conformity with the Upper Jurassic morphotypes. Besides the Middle Jurassic P. primaeva Kamoun & Peybernès and the Upper Jurassic P. caelinensis, P. valanginiana sp. nov. represents the third species of the genus described and possibly a Valanginian marker endemic for the Arabian Plate. In the Fahliyan Formation, P. valanginiana sp. nov. occurs in wackestones associated with Pseudocyclammina lituus (Yokoyama). Additional data for the micropalaeontological assemblages (benthic foraminifera, calcareous algae) of the shallow-water carbonates of the Fahliyan Formation are provided. As it is also the case in the United Arab Emirates (Granier, 2008), it is proposed that the Tithonian/Berriasian boundary does not, as generally indicated in the literature, coincide with the boundary of the Hith Formation and the Fahliyan Formation, but instead occurs within the latter. The new finds provide further evidence that the Tithonian/Berriasian boundary did not represent a major rupture or extinction for larger benthic foraminifera. On the contrary, the Berriasian/Valanginian boundary corresponds to a natural discontinuity (both sedimentological and biological) possibly enhanced by a hiatus of the upper Berriasian strata. The foraminiferal diversity remains quite high during early Valanginian times then falls drastically, which suggests that the Berriasian/Valanginian crisis is a double barelled crisis (first base Valanginian, second intra-Valanginian).