Peri-Gondwanan acritarchs from the Ordovician of the Llanos Orientales Basin, Colombia

Abstract

There are few publications on the precise age and palaeogeography of the Palaeozoic rocks of Colombia. In the present study the Pluspetrol Paisa-1 well, located in the central part of the Colombian Llanos Orientales Basin, is investigated palynologically, in order to determine the age, the palaeoenvironment and the palaeogeography of the sediments. The lowermost stratigraphical interval of the well (4939–5040′; ∼1505–1536 m) is composed of alternating sandstone and black shale beds, from which a well-preserved assemblage of Ordovician acritarchs has been identified in five samples (cuttings and sidewall cores). The acritarch assemblage contains some diagnostic taxa, including Arbusculidium, Barakella, Coryphidium, Dactylofusa, Striatotheca, and Veryhachium, among others, indicating an Early to Middle Ordovician age. The presence of a few biostratigraphical index species, such as Dactyolofusa velifera or Coryphidium bohemicum, and the absence of others point to a middle Floian age. As the three diagnostic genera (Arbusculidium, Coryphidium, Striatotheca) are present, the assemblage clearly belongs, in terms of palaeobiogeography, to the peri-Gondwanan acritarch province. Our study thus extends the geographical distribution of this province to the north-western part of South America, extending the palaeobiogeographical distribution map of Early to Middle Ordovician acritarchs. A comparison of the palynoflora with models of acritarch distribution in different palaeoenvironments implies a relatively shallow-water environment.

Keywords:

• phytoplankton
• South America
• peri-Gondwana
• biostratigraphy
• palaeobiogeography
• palaeoenvironment

Acknowledgements

We acknowledge the Ecole Doctorale ED 104 (Sciences de la Matière, du Rayonnement et de l’Environnement), Université de Lille, for financial support. This work is a contribution to the CPER research project CLIMIBIO (we acknowledge the French Ministry for Higher Education and Research, the Hauts de France Region and the European Funds for Regional Economic Development for their financial support for this project). We thank the Pluspetrol company for kindly allowing the use of the palynological data. The Instituto de Incestigaciones en Estratigrafía – IIES (Universidad de Caldas, Colombia) gave important logistic support. This is a contribution to IGCP 653 ‘The onset of the Great Ordovician Biodiversification Event’.

Notes on contributors

DAVID M. KROECK received his MSc in earth sciences in 2016 from the University of Bonn, Germany. Since 2016 he is a PhD student at the Evo-Eco-Paléo unit of the University of Lille working on the biodiversity, palaeoecology, palaeogeography and biostratigraphy of the phytoplankton, mainly acritarchs, of the Palaeozoic.

ANDRÉS PARDO-TRUJILLO is a Geologist of the Department of Geological Sciences of the University of Caldas (Manizales, 1998). Andres obtained his M.Sc. in Vegetal micropalaeontology at 1997 and his PhD in Science at Liège University (Belgium, 2004). He has worked as a professor in the department of Geological Sciences at Universidad de Caldas (Colombia) since 1989. During 2006–2009 he worked as an advisor to the National Hydrocarbons Agency, where participated in the geological study of several Colombian sedimentary basins. Andres is currently director of the Instituto de Investigaciones en Estratigrafía-IIES and of the Research Group in Stratigraphy and Vulcanology-GIEV Cumanday at the Universidad of Caldas.

ANGELO PLATA TORRES obtained his bachelor’s degree in biology from the Universidad Industrial the Santander, Colombia in 2007. Angelo worked at the Colombian oil company ECOPETROL for 5 years as a junior biostratigrapher before going to the Spain in 2012 to obtain his Master of Earth Science degree from the Department of Geology, Salamanca University. At coming back of Salamanca University, he works as palynologist in chief of the Palynology Lab for Instituto de Investigaciones en Estratigrafía (IIES), Universidad de Caldas, where research about terrestrial palynomorphs and marine diatoms. Currently, Angelo is candidate to PhD in Salamanca University.

MILLERLANDY ROMERO-BAÉZ is a biologist with a Master of Science from Rice University in Houston. With 10+ years of experience in oil & gas and environmental research, her primary focus has been palaeoecology/ecology, environmental science, and sustainable development and design. Her career started as a junior biostratigrapher in Ecopetrol, the Colombia national oil company, followed by a more senior career as a palynologist and palaeoecologist intern at Smithsonian Tropical Research Institute. She also consulted for energy production companies, government petroleum agencies, and research groups around the world. Currently, she is applying her prior experience as an environmental researcher to provide advice on sustainability topics related to the use of natural resources in a highly competitive business environment. She is an avid advocate of low carbon and circular economy in a society with a growing demand for energy, water, food, and human well-being.

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 in 1997. His research is focused on Lower Palaeozoic microphytoplankton. Thomas is currently vice-chairman of the International Subcommission of Ordovician Stratigraphy (ISOS) and co-leader of the International Geoscience Programme (IGCP) 653 ‘The onset of the Great Ordovician Biodiversification Event’ (2016-2020).