Biozonation and Paleobathymetry on Foraminifera Upper Cretaceous Deposites of Central Iran Basins (Isfahan, Baharestan Section)

Abstract

In this study LateCretaceous stratum in central Iran, Baharestan section in Isfahan area, wasevaluated by biozonation and paleobathymetry. These sediments have 89 meters thick, and stratahave been formed of marl and marl limestone. In order to indicate the ancientdepth of Upper Cretaceous at this time, planktonic and benthic foraminiferawere studied. The percentage of the total planktonic foraminifera to the wholesample of foraminifera after the removal of indwell benthic foraminifera (%P*)using the formula D = e(3.58718 + (0.03534 × %P*)) was identified and depth of 200 - 450meters was achieved for them. In the present investigation, 30 planktonicspecies of 11 genus have been identified. The Upper Cretaceous deposit wasdivided to 6 biozones on the basis of planktonic foraminifera which arecosmopolitan and consist of: Biozone 1—Marginotruncana sigali-Dicarinellaprimitiva partial range zone; Biozone 2—Dicarinellaconcavata interval zone; Biozone 3—Dicarinella asymetrica total range zone; Biozone 4—Globotruncanitaelevata partial range zone;Biozone 5—Globotruncana ventricosa intervalzone; Biozone 6—Radotruncana calcarata intervalzone. Based on planktonicforaminifera, the Upper Cretaceous sediments in the study area are of theTuronian-Late Campanian ages.