Palaeoenvironmental reconstruction based on coralline red algal and foraminifera assemblages in Oligo-Miocene succession of NW central Zagros, Iran

The biofacies analysis together with a detailed study of larger benthic foraminfera and non geniculate (crustose) red algae were used to palaeoenvironmental reconstruction of Oligo-Miocene succession of NW central Zagros. Assemblages are dominated by the taxa of subfamilies Melobesioideae (Lithothamnion, Mesophyllum), Mastophoroideae (Spongites) and Lithophylloideae (Lithophyllum). Additionally, Sporolithon (Sporolithaceae) occurs. In this succession, a conspicuous pattern in the distribution of coralline red algae is observed that correspond to the distribution of foraminifera. Two red algal associations are identified: a Lithophyllum dominated association with inner ramp index foraminifera restricted to the upper photic zone in warm-temperate environments and a Mesophyllum dominated association with distal middle ramp index foraminifera which is characteristic for the lower photic zone in warm-temperate to tropical environments. Intervals with dominant Mesophyllum are associated with Heterostegina, Lepidocyclina and planktonic foraminifera that have been interpreted to represent distal middle ramp deposits show a high water depth index. Intervals with dominant Lithophyllum are associated with inner ramp index foraminifera including porcellaneous foraminifera show a shallow-water environments.