Two new dinoflagellate cyst species and their biostratigraphical application in the Eocene and Oligocene of the North Sea

Abstract

The Cenozoic of the North Sea is among the best-documented stratigraphical successions in the world, and multiple palynological events have been recognised for chronostratigraphical control across the region. The ever-increasing number of wells studied for hydrocarbon exploration and production results in the generation of new biostratigraphical data that constantly increase our palynological knowledge of the area. Here we describe two new dinoflagellate cyst species from an Lower Eocene (Ypresian) to Lower Oligocene (Rupelian) succession in Gannet Field (UK Central North Sea). These are Reticulatosphaera valdereticulata sp. nov., a short-lived Rupelian index taxon, and Alisocysta heilmannii sp. nov., previously informally known as Alisocysta sp. 2, which is an Ypresian marker widely used by biostratigraphers working the North Sea region. The development of a dense network of trabeculae connecting the processes distally allows Reticulatosphaera valdereticulata sp. nov. to be clearly distinguished from the closely similar Reticulatosphaera actinocoronata. The main diagnostic feature in Alisocysta heilmannii sp. nov. is the development of delicate penitabular septa. Both species show widespread palaeogeographical distribution across the North Sea region. We also document the diverse palynofloras in which the two new species are encountered and discuss biostratigraphical application and palaeoenvironmental settings.

Keywords:

• North Sea
• Paleogene
• dinoflagellate cysts
• biostratigraphy
• taxonomy
• palaeobiogeography

Acknowledgements

Permission to publish the data and interpretations herein was kindly provided by Shell UK Ltd., and their partners Esso Exploration and Production UK Ltd. The interpretations and opinions presented here are those of the authors only and do not in any way represent the views of Shell UK Ltd. or Esso Exploration and Production UK Ltd. Manuel Casas-Gallego and Iakov Gogin publish with the permission of CGG Robertson. Jim Fenton and Peter Osterloff, as well as reviewers Robert Fensome and Claus Heilmann-Clausen, are thanked for reading the original manuscript and for their useful suggestions to improve it. Steve Jones and Mark Rees are thanked for the processing of the samples.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Manuel Casas-Gallego

MANUEL CASAS-GALLEGO is a Project Stratigrapher with CGG Robertson UK. He started working on palynology in 2005 during a stay at 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, North America, Romania, West and East Africa, SE Asia, Guyana and Jamaica.

Iakov Gogin

IAKOV GOGIN is a Project Geoscientist and Stratigrapher at CGG Robertson, UK. He studied Ordovician sedimentology and palynology at the University of St. Petersburg, Russia. After that he focused on Mesozoic palynology of West Siberia and Caspian as consultant/stratigrapher in Geologorazvedka Institute in Russia. In 2012 he joined Ichron Ltd (later acquired by RPS) to become offshore stratigrapher with focus on North Sea (UK and Norway), Faroe-Shetlands, Canada and West Africa. In 2018 he moved to CGG Robertson and got experience on Tertiary and Mesozoic of North Africa, Mediterranean and Eastern Europe. Research interests are dinoflagellate cysts and Mesozoic stratigraphy.

Manuel Vieira

MANUEL VIEIRA is a Senior Stratigrapher at Shell UK, based in Aberdeen since 2013. He currently supports all the offshore Northwest Europe exploration and development activities. After completing a PhD at Minho University (Portugal) in 2008, Manuel worked as a consultant Stratigrapher/Palynologist with Ichron Ltd. He was involved in projects from the North Sea (UK and Norway), Shetland Basin, Faroe Islands, India, Sri Lanka, Brazil, Morocco, Falkland Islands and Greenland. Manuel has much wellsite experience, especially on Mesozoic and Cenozoic sequences. His research interests are on dinoflagellate cysts, pollen and spores, paleoclimate, palaeobotany and evolution.