Distribution and Paleoecology of the Middle Jurassic Foraminifera from Eastern Alborz (Goznawwi section)

Document Type: Research Paper

Authors

1 Department of Geology, Faculty of Science, University of Isfahan, P.O. Box, 81746-73441, Isfahan, Iran.

2 Research Institute for Earth Sciences, Geological Survey of Iran, P.O. Box, 1385-1494, Tehran, Iran

Abstract

Analysis of benthic foraminiferal assemblages was performed in Callovian deposits of the Farsian Formation Northeastern Alborz; Iran. The sequence of Callovian at the Goznawwi area consists mainly of soft marls , which contain high-diversity calcareous assemblages. In this foraminiferal succession nine morphogroups were differentiated according to shell architecture (general shape, mode of coiling and number of chambers), integrated with the supposed microhabitat (epifauna, shallow infauna and deep infauna) and feeding strategy (suspension-feeder, herbivore, bacterivore, etc.). Based on foraminiferal assemblage, we have distinguished nine type of morphogroups, including seven calcareous benthic and two agglutinated benthic morphogroups. The environmental evolution of the analyzed section is interpreted by using the stratigraphic distribution of morphogroups, combined with species diversities and sedimentary data, in a sequence stratigraphic framework. Palaeoecological analysis of the foraminiferal assemblages based on morphogroups analysis and macroinvertebrate has shown that this sediment was deposited on the open marine, deeper of the shelf water, with normal saline (euhaline), with sub-oxyed (or dysoxic) condition and eutrophic environment.

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Article Title [Persian]

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