Impagidinium obscurum sp. nov., a marker dinoflagellate cyst for the Thanetian (Paleocene) of the North Sea and the Barents Sea

Abstract

This paper presents the formal description of Impagidinium obscurum sp. nov. from the Thanetian strata of northwest Europe. The palaeogeographic distribution of this species covers a wide area, ranging from the North Sea to the Barents Sea. Palynologists working in the region have long referred to Impagidinium obscurum sp. nov. as Leptodinium? ‘obscurum’ and used it as an important intra-Paleocene marker species. The informal specific name was with reference to the incompletely defined tabulation of the cyst. However, although the tabulation is often obscured by the dense folding of the walls, the cyst tabulation formula has been partly deciphered in this work, based on the organisation of sutural crests in exceptionally well-preserved specimens, which allows confident attribution to the genus Impagidinium. This species is restricted to the ‘early’ Thanetian and is associated with diverse dinoflagellate cyst assemblages which include Alisocysta margarita and Areoligera gippingensis.

Keywords:

• Thanetian
• taxonomy
• dinoflagellate cyst
• biostratigraphy
• palaeobiogeography
• North Sea
• Barents Sea

Acknowledgements

The authors would like to thank A/S Norske Shell, CGG Robertson and RPS Ichron Ltd for permission to publish this research. The views expressed might not necessarily reflect the views of these company. RPS Ichron and CGG Robertson are also thanked for permission to use their laboratory facilities. The authors would also like to thank Marc Gordon (Shell UK) for support with ArcGIS. Finally, they would like to thank the reviewers Raquel Guerstein and Peter Bijl for their valuable comments on taxonomy and their help in finalising this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

MANUEL VIEIRA is currently based in Aberdeen, since 2013, working as a Biostratigrapher for Shell UK supporting all the offshore Northwest Europe activities. Undergraduate at Minho University (Portugal), followed by a PhD studying Pliocene palynology completed in 2008. Before joined Shell worked as a consultant Stratigrapher/Palynologist with Ichron Ltd. Was involved in projects from the North Sea (UK and Norway), Faroes, West of Shetlands, India, Sri Lanka, Brazil, Morocco, Falklands and Greenland. Experienced at wellsite on several wells (Cenozoic and Mesozoic sequences).

MANUEL CASAS-GALLEGO is a Stratigrapher with CGG Robertson UK. He started working on palynology in 2005 during a stay at the Montpellier University (France), studying Miocene sediments of Thailand. He earned his PhD degree at the Autonomous University of Madrid in 2017 undertaking research on the Paleogene palynology of northern Spain. Manuel worked as a consultant palynologist/paleobotanist in Madrid from 2006 to 2014, before joining CGG Robertson UK, where he has been involved in projects from the Cenozoic and Mesozoic of the North Sea and Norwegian Sea, West and East Africa, North America, Jamaica, Romania and SE Asia, among others.

SALIH MAHDI is a Principal Palynologist/Stratigrapher with RPS ichron, based in Northwich Cheshire, he studied geology at the University of Baghdad, Iraq, before undertaking research on the Carboniferous palynology of northern England at the University of Aston in Birmingham, for which he was awarded a PhD in 1982. In 1986 he joined Gearhart Geoconsultant to work on Mesozoic and Paleogene successions in the North Sea. He was soon called upon to work on the Carboniferous palynology of the southern North Sea (UK and Dutch sectors) Irish Sea and onshore UK. Since then he enquired extensive biostratigraphical experience of Paleogene, Mesozoic and Palaeozoic sequences of Northwest Europe. He also has extensive biostratigraphic experience of Upper Palaeozoic, Mesozoic and Tertiary sequences of Brazil, Falkland, North and West Africa, Middle East (Iraq, Qatar, Oman ↦ Syria), India and Pakistan.

JIM FENTON is Chief Stratigrapher with CGG Robertson, based in Llandudno, North Wales. He studied geology at University of Sheffield, graduating in 1975 before undertaking research on the palynology of the Middle Jurassic of the East Midlands at the same institution. He was awarded a Ph.D in 1980. In 1978 he joined Robertson Research and commenced work on Mesozoic and Tertiary successions in NW Europe. Geographic and stratigraphic expansion has led to single and multi-disciplinary studies, often associated with seismic and sedimentological interpretations, on basins ranging from offshore New Zealand to the Norwegian/Russian Barents Sea and West Coast Canada to Mongolia, with stratigraphy varying from Pleistocene to Carboniferous. Key areas of expertise are NW Europe, East and West Africa, East Coast Canada and USA, onshore USA (Wyoming and Texas), South America (Peru) and Middle East (Kurdistan, Kuwait, Yemen). Wellsite studies have been completed in the Barents Sea, Norwegian Sea, North Sea (UK, Norway and Denmark), offshore Senegal, Gabon and Tanzania.