Paleoenvironmental analyses of coralline red algal assemblages in Lower Miocene carbonate deposits of Central Iran

ABSTRACT

This work is based on coralline red algal flora-dominated Lower Miocene carbonates of the Qom Formation from Central Iran Basin. Five assemblages, including corallinoid, lithophylloid, mastophoroid, melobesioid and sporolithoid corresponding to 11 genera of geniculate and non-geniculate, were identified. Also, growth forms and taphonomic characteristics of coralline-algal grains were assessed. The arborescent, layered to foliose lamellae, fruticose, lumpy, warty and encrusting growth forms of studied taxa are observed and five taphonomic traits belonging to both mechanical [abrasion, disarticulation, fragmentation] and biological [encrustation, bioerosion] processes were recognised. The relative abundance of assemblages, growth forms, and taphonomy of red algae visualised at thin-section scale were calculated. Our quantitative analysis highlights mechanical (abrasion > fragmentation) and biological (bioerosion> encrustation) processes. Moreover, layered to foliose and fruticose abundance peaks reveal higher than others. This kind of algal distribution in the examined region indicates that the Qom Formation was deposited on a marine carbonate shelf, which is a deepening depositional system in tropical and subtropical zone. This approach expresses more abundance of red algal assemblages on the deep part of inner and proximal to distal middle shelf settings along with a regime of moderately high towards low hydrodynamic energy and mesophotic – oligophotic conditions.

GRAPHIC ABSTRACT

KEYWORDS:

• Lower miocene
• coralline red algae
• growth forms
• taphonomy
• environmental factors
• Iran

Acknowledgments

The authors would like to thank historical biology editor Dr. Gareth Dyke and the reviewers for their profitable suggestions and helpful comments on the manuscript. Sincere thanks to F. Bakhtiari for her cooperation with one of the authors (J. Daneshian) in collecting and preparing the thin-section.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the Kharazmi University