A new ichnospecies Nummipera saraswatii from the early Eocene (Ypresian) Assilina bank deposits of the Naredi Formation, Kutch Basin, India

Abstract

A new ichnospecies of the ichnogenus Nummipera Hölder, 1989 has been documented in the carbonate packstone and wackestone of the Ypresian (early Eocene) Naredi Formation from the western Kutch (Kachchh) Basin, India. This new ichnospecies is distinguished from Nummipera eocenica (the existing sole ichnospecies of ichnogenus Nummipera) on the basis of the burrow orientation, taxonomy and orientation of foraminifera lining the burrow walls, and burrow filling. Nummipera saraswatii isp. nov. represents the earliest occurrence of Nummipera. It is a horizontal to gently inclined, straight to feebly curved, intermittently vertically flattened tubular burrow closed at one end, displaying circular to elliptical cross-sections, and representing three-distinct morphotypes. The analyzed specimens are characterized by walls mostly lined with unbroken and well-sorted megalospheric tests of Assilina laxispira. Burrows are characterized by active massive fill akin to the host material consisting of organic-rich muddy material and bioclasts or active concentric fill displaying a distinct outer and inner lumen, filled with organic-rich materials of different grain-sizes varying from mud to sand. Crustaceans and vermiform animals can be envisaged as the probable producers based on the distinctive morphotypes and ethological affinity. The shallow-tier N. saraswatii shows association with the deep-tier Cylindrichnus concentricus. The association manifests key features of a stressed Cruziana Ichnofacies and characterizes an Assilina bank of a proximal carbonate open shelf setting.

Keywords:

• Armored burrow
• ichnology
• carbonate
• Assilina laxispira
• Kachchh Basin

Acknowledgements

The authors would like to express their gratitude to the following agencies for aiding this research: Industrial Research and Consultancy Centre (IRCC; for seed grant # RD/0517- IRCCSH0-035 to SDG and final-year scholarship to MD) of Indian Institute of Technology Bombay (IIT Bombay) and Ministry of Education of Government of India (GoI) for funding the doctoral scholarship for MD; Science and Engineering Research Board (SERB), GoI (grant # CRG/2018/000259 to SDG); Council of Scientific and Industrial Research (CSIR) for the doctoral scholarships for RD and AN. The authors deeply acknowledge the Department of Earth Sciences and SAIF, IIT Bombay, for its sustained infrastructure support. The authors express their heartfelt gratitude to PK Saraswati, LA Buatois (Chief Co-Editor), R Netto (Associate Editor), MG Mángano (Reviewer 2), S Banerjee, J Punekar, A Wetzel, an anonymous reviewer (Reviewer 1) for their valuable insight and discussion. Authors would also like to thank the State Government of Gujarat, the District Administration of Kachchh, Ganni Bhai, and his associates for their cooperation and support during the fieldworks. Field assistance, intellectual discussions, and moral support by A Srivastava, D Rajkhowa, K Chatterjee, K Prasad, S Bajpai, and S Aich is highly appreciated.

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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 this research: Industrial Research and Consultancy Centre (IRCC; for seed grant # RD/0517- IRCCSH0-035 to SDG and final-year scholarship to MD) of Indian Institute of Technology Bombay (IIT Bombay) and Ministry of Education of Government of India (GoI) for funding the doctoral scholarship for MD; Science and Engineering Research Board (SERB), GoI (grant # CRG/2018/000259 to SDG); Council of Scientific and Industrial Research (CSIR); Department of Earth Sciences and SAIF, IIT Bombay’.