Original paper

Biostratigraphy and planktonic foraminiferal abundance in the phosphate-bearing Pabdeh Formation of the Lar Mountains (SW Iran)

Daneshian, Jahanbakhsh; Shariati, Sharam; Salsani, Armin


The Pabdeh Formation is located in the Zagros sedimentary basin, southwest Iran. This study assessed the effect of phosphate environmental factors on planktonic foraminiferal diversity and abundance in phosphate-bearing horizons. Age determination based on planktonic foraminifera suggests that the age of the studied section is Oligocene to Eocene. Analytical tests were conducted to determine the phosphate grade of each bed. The percentages of planktonic and benthonic foraminifera were assessed using a semi-quantitative method. The amount of globigerinathekids increases with increasing phosphate in the strata, i. e., there is a direct relationship between globigerinathekid percent abundance and phosphate grade. This finding could be used to determine the quality of a phosphate deposit. The abundance of phosphate in the environment directly affected the diversity of hantkeninids: percent abundance is higher at higher phosphate levels. Replacement primary porosity of skeletal fragments, infilling of interparticle porosity by phosphate cement, and the presence of rim envelopes surrounding body fossils and non-skeletal particles demonstrate that formation of phosphate cement occurred during early diagenesis.


phosphateearly diagenesispaleogenediversityinterparticle porosityforaminiferapabdeh formationiran