Coated grains in the Upper Cretaceous Ilam Formation: implication for paleoclimatic reconstruction

Document Type: Research Paper


1 Department of Petroleum Geology, Research Institute of Petroleum Industry (RIPI) 14857-33111 Tehran, Iran

2 School of Geology, College of Science, University of Tehran, 14176-14411 Tehran, Iran

3 School of Earth Sciences, Damghan University, 36716-41167 Damghan, Iran


The Upper Cretaceous Ilam carbonate Formation has been analyzed for its coated grains (fine ooids and rhodoids) in oilfields of SW Iran. The recognized coated grains are morphologically classified into several types. Petrographic and geochemical characteristics indicate that the ooids were originally composed of low-magnesium calcite (LMC; consistent with global observations), but rhodoids consisted originally of high-magnesium calcite (HMC). The overall primary mineralogy of the intervals containing coated grains has been a mixture of HMC and LMC. Co-occurrence of these mineralogies and allochemical (both ooids and rhodoids and other bioclasts) components indicates a rhodalgal-like grain association and a relatively temperate paleoclimatic conditions.


Article Title [Persian]


Articles in Press, Accepted Manuscript
Available Online from 07 December 2019
  • Receive Date: 13 July 2019
  • Revise Date: 15 November 2019
  • Accept Date: 07 December 2019