Palynological analyses of the sediments around the Miocene/Pliocene boundary in ODP Hole 151-911A

• Main Authors: Grøsfjeld, Kari, De Schepper, Stijn, Fabian, Karl, Husum, Katrine, Baranwal, Soma, Andreassen, Karin, Knies, Jochen
• Format: Dataset
• Language: English
• Published: PANGAEA 2014
• Subjects: 151-911A; Achomosphaera andalousiensis andalousiensis; Achomosphaera andalousiensis suttonensis; Acritarcha; standard error; Acritarcha indeterminata; Acritarcha per unit mass; Amiculosphaera umbraculum; Barssidinium evangelineae; Barssidinium graminosum; Barssidinium pliocenicum; Barssidinium spp.; Bitectatodinium raedwaldii; Bitectatodinium tepikiense; Botryococcus spp.; Brigantedinium spp.; Cymatiosphaera invaginata; Cymatiosphaera spp.; DEPTH; sediment/rock; Dinoflagellate cyst; Dinoflagellate cyst indeterminata; Dinoflagellate cyst per unit mass; Dinoflagellate cyst reworked; Dinoflagellate cyst reworked per unit mass; DRILL; Drilling/drill rig; Dry mass; DSDP/ODP/IODP sample designation; Echinidinium euaxum; Filisphaera filifera; Filisphaera microornata; Foraminiferal organic linings; Habibacysta tectata; Impagidinium aculeatum; Impagidinium pallidum; Impagidinium patulum; Impagidinium sp.; Impagidinium spp.; Invertocysta lacrymosa; Invertocysta tabulata; Joides Resolution; Laboratory code/label; Lavradosphaera crista; Lavradosphaera lucifer; Arctic; Arctic Ocean; Yermak Plateau; Foraminifera*; Sea ice; Subarctic; Yermak plateau; Spitsbergen
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.834616; https://doi.org/10.1594/PANGAEA.834616

The late Neogene evolution of the Arctic to Subarctic region is poorly understood due to few available records and poor age control. At the margin of the Arctic Ocean, Yermak Plateau Ocean Drilling Program (ODP) Hole 911A is strategically located for establishing a stratigraphic framework for the Arctic. Here we present dinoflagellate cyst and acritarch data from 24 stratigraphic levels in the lower part (474.26-505.64 metres below the seafloor (mbsf)) of ODP Hole 911A. The marine palynomorphs indicate a latest Miocene to earliest Pliocene age (between 5.8 and 5.0 Ma) for the base of the hole based on the co-occurrence of the dinoflagellate cyst Barssidinium evangelineae and acritarch Lavradosphaera crista. Our age estimate for the sediments can possibly be further refined to 5.0-5.33 Ma based on the presence of Achomosphaera andalousiensis suttonensis, which apparently has a range restricted to the Pliocene. An age close to the Miocene/Pliocene boundary agrees with the planktonic foraminifer data. Together with recently available magnetostratigraphic data, the base of the hole is likely to be placed at ~5.2 Ma. This new chronostratigraphy is a first step towards a better understanding of the late Neogene palaeoenvironment for the Yermak Plateau and also for the wider Arctic to Subarctic region. The terrestrial and fresh water palynomorphs were most likely redistributed and/or displaced from the shelf towards deeper parts of the basin during contourite deposition under the influence of the West Spitsbergen Current. The in situ marine dinoflagellate cyst assemblage contains a mixture of cool water and thermophilic taxa, indicating sea-ice free, cool-temperate, warmer than present conditions at the Yermak Plateau. Rivers were likely the source for the freshwater influence.