Biostratigraphy and surface-water reconstruction for the Oligocene of the North Atlantic based on organic-walled dinoflagellate cysts
Final Report Abstract
The Oligocene represents a critical interval of Cenozoic climate evolution because it allows to study the processes underlying the transition from a world free of large-scale continental ice shields and rapid eustatic sea-level change to one dominated by these factors. To contribute to a better understanding of Oligocene climate dynamics in the higher-latitude North Atlantic, we have studied dinocysts from IODP Sites U1405, U1406 and U1411 in high temporal resolution. Besides yielding the first chronostratigraphically calibrated dinocyst biostratigraphy for the Oligocene of the higher-latitude North Atlantic, our results also provided new insight into surface-water and sea-level changes. For the Oligocene/Miocene transition interval, we reconstruct a long-term surface-water cooling off Newfoundland from c. 23.1 Ma onwards; surface-water productivity remained generally low. The lack of a correlation between surface-water productivity and temperature renders it unlikely that the observed paleoceanographic change was caused by a southward migration of the Arctic Front. Instead, our data may document an enhanced influence of the (Proto- )Labrador Current on surface waters off Newfoundland that suppressed the influence of the Gulf Stream. We speculate that the enhanced influence of the (Proto-) Labrador Current was triggered by northern hemisphere cooling and possibly modulated by high-latitude sea-ice expansion. A pronounced, eccentricity-paced sea-level variability is documented in the abundances of neritic dinocysts and terrigenous palynomorphs, which reach maxima during glacial intervals as inferred from previously published benthic oxygen-isotope data. In the ‘mid-Oligocene’, we observe marked, likely astronomically paced abundance pulses of the cold-water indicator Svalbardella cooksoniae. The occurrences of this taxon indicate that the North Atlantic off Newfoundland experienced repeated surface-water cooling in conjunction with mid-Oligocene Antarctic glaciations. For the Eocene/Oligocene transition interval, our dinocyst-based surface-water temperature reconstruction from Site U1411 indicates a first, transient cooling ~100 kyrs prior to the Oi-1 event, followed by a return to warmer conditions and a second, longer-lasting (~200 kyrs) cooling before warmer conditions resumed. The dinocyst-based surface-water productivity mimics the surface-water temperature curve, with enhanced productivity co-occurring with cooler conditions and vice versa.
Publications
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2016. Magnetostratigraphically calibrated dinoflagellate cyst bioevents for the uppermost Eocene to lowermost Miocene of the western North Atlantic (IODP Expedition 342, Paleogene Newfoundland sediment drifts). Review of Palaeobotany and Palynology 234, 159–185
Egger, L.M., Śliwińska, K.M., van Peer, T., Liebrand, D., Lippert, P.C., Friedrich, O., Wilson, P.A., Norris, R.D., Pross, J.
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2017. Comment to “Wetzeliella and its allies – the ‘hole’ story: a taxonomic revision of the Paleogene dinoflagellate subfamily Wetzelielloideae. Palynology 41, 423–429
Bijl, P.K., Brinkhuis, H., Egger, L.M., Eldrett, J.S., Frieling, J., Grothe, A., Houben, A.J.P., Pross, J., Śliwińska, K.K., Sluijs, A.
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2018. Sea-level and surface-water change in the western North Atlantic across the Oligocene–Miocene transition: a palynological perspective from IODP Site U1406 (Newfoundland margin). Marine Micropaleontology 139, 57–71
Egger, L.M., Bahr, A., Friedrich, O., Wilson, P.A., Norris, R.D., van Peer, T.E., Lippert, P.C., Liebrand, D., Pross, J.
