A review of the Ordovician acritarch genus Barakella Cramer & Díez 1977

ABSTRACT

The Ordovician acritarch genus Barakella Cramer & Díez 1977 and two species, B. felix and B. fortunata, bearing characteristic anastomosing filamentous elements at one pole were first described from the subsurface of the Kasba Tadla Basin, Morocco. Subsequently, another species was described from the South Chinese Ordovician and was later attributed to the genus as Barakella rara. New material from the type locality in Morocco and additional sections in South China are used for a review of the genus Barakella. Based on this review, including statistical analysis, Barakella rara is considered a junior synonym of Barakella felix. Barakella is a useful taxon for biostratigraphical applications in the Ordovician. Its first appearance datum (FAD) lies in the early Floian (Early Ordovician, time slices 2a–2b) in both South China and Wales. Except for a doubtful record from Sweden, all records of Barakella are from the peri-Gondwana margin, making the genus an indicator of the peri-Gondwana palaeoprovince. The appearance of Barakella in South China indicates that Barakella possibly originated in shallow-water nearshore environments, and later spread to offshore environments.

KEYWORDS:

• Ordovician
• Barakella
• South China
• Morocco
• biostratigraphy
• statistical analysis

Acknowledgements

This paper is respectfully dedicated to the late Gordon D. Wood, our colleague and friend for many years. This study was initiated while Yan Kui was undertaking a post-doctoral fellowship at the University of Lille. Part of Thomas Servais’ contribution for this manuscript was written whilst undertaking a Visiting Fellowship at the Institute of Advanced Study (IAS), Durham University, UK. Thomas also thanks David A.T. Harper (Van Mildert College, Durham) for hosting his visit and for discussion. We thank Dr Bing Huang for the discussion on statistical analysis. We acknowledge the Office National des Hydrocarbures et des Mines (ONHYM), Rabat, Morocco, for providing access to the borehole material from Boujad. The palynological treatment of the material from Morocco was performed at the University of Lille; Laurence Debeauvais is thanked for technical assistance. We acknowledge the careful review by managing editor Jim Riding, guest editor Merrell Miller and referee Reed Wicander, and their valuable comments and suggestions. This work is a contribution to IGCP project 653 (The Onset of the Great Ordovician Biodiversification Event). Stewart Molyneux publishes by permission of the Executive Director, British Geological Survey (NERC).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) [grant numbers 41272012, 41472007, 41521061, and 41290260] and the Chinese Academy of Sciences [grant number XDP05]. Part of Elena G. Raevskaya's research was supported by the Russian Foundation for Basic Research [grant number 16-05-00799].

Notes on contributors

Kui Yan

KUI YAN is an associate researcher at the Nanjing Institute of Geology and Palaeontology, China. He graduated in geology from the Chinese University of Geoscience at Wuhan in 2001. In 2007, he received his PhD from the Nanjing Institute of Geology and Palaeontology. Kui visited the University of Lille 1, France, for a post-doctoral programme from 2009 to 2010. Kui mainly works on the stratigraphical and palaeogeographical significance of the Ordovician microphytoplankton of southern China. Specifically, he specialises in the study of interactions between palaeoenvironment and microphytoplankton evolution during the Great Ordovician Radiation.

Jun Li

JUN LI graduated in geology from Peking University, Beijing, China, in 1978. He received his MSc in 1981 and a PhD in 1991, both from the University of the Chinese Academy of Sciences, Beijing. Since 1981, he has been a permanent researcher in the Nanjing Institute of Geology and Palaeontology, and was promoted to research professor in 1999. Jun visited the University of Sheffield, UK, during 1985, and the University of Lille 1, France, on numerous occasions between 2000 and 2017. He also visited Central Michigan University, USA, for three months in 2004. Jun's research is focused on Ordovician and Silurian acritarchs.

Stewart G. Molyneux

STEWART G. MOLYNEUX received his BSc and PhD degrees from the University of Sheffield, UK, where his PhD research on Ordovician palynology was supervised by Professor Charles Downie. He joined the British Geological Survey (BGS) as a palynologist in 1979, and remained there throughout his career, working initially on Mesozoic successions of the North Sea, but then increasingly to support BGS mapping of Lower Palaeozoic outcrops in Wales, northern England, the Southern Uplands of Scotland and Devonian successions in south-west England. He also worked on various international projects for BGS and under contract for other organisations, coupled with editorial work and management responsibilities. He retired from BGS in 2014, but remains active in both research and consultancy work, with a focus on Lower Palaeozoic palynology.

Elena G. Raevskaya

ELENA G. RAEVSKAYA is head of the Stratigraphy Department and a deputy director at the State Research and Production Enterprise ‘GEOLOGORAZVEDKA’. She received her MSc in historical geology from Novosibirsk University in 1992 and her PhD in palaeontology and stratigraphy from Saint-Petersburg University in 2000. She obtained a scholarship for studies in Sweden and post-doctoral programmes in Italy and France. Her research interest is focused on Precambrian, Cambrian and Ordovician palynology (acritarch taxonomy, systematics, evolution), biostratigraphy, palaeoecology and palaeobiogeography of the Siberian and East European Platforms, and Arctic Russia, as well as Mesozoic (Jurassic and Cretaceous) micropalaeontology, palynology, biostratigraphy and basin analysis of the main oil and gas provinces of Russia (Western Siberia, etc.). Since 2015, Elena has been Vice President of the Palaeontological Society of Russia.

Thomas Servais

THOMAS SERVAIS is a research director at the French Centre of Scientific Research (CNRS). He was trained as a geologist at the universities of Namur and Liège in Belgium, and received a PhD on Ordovician acritarchs in 1993. After postdoctoral studies in Belgium, Germany and the United Kingdom, Thomas was recruited as a CNRS research associate at the University of Lille 1 in 1997. Most of his research concentrates on Lower Palaeozoic microphytoplankton, but other fields of interest include regional geology, macropalaeontology and micropalaeontology. Thomas has been Secretary of the Acritarch Subcommission of the Commission Internationale de Microflores du Paléozoïque (CIMP), General Secretary of CIMP, President of the Association de Palynologues de Langue Française (APLF), President of the Association Paléontologique Française (APF) and leader of the International Geoscience Programme (IGCP) project no. 503 ‘Ordovician Palaeogeography and Palaeoclimate’. He is currently President of the International Federation of Palynological Societies (IFPS) and Vice President of the International Palaeontological Association, and leader of the International Geoscience Programme (IGCP) project no. 653 ‘The onset of the Great Ordovician Biodiversification Event’.