Dating Oligocene-Recent siliciclastic sediment sequences from the Norwegian Sea

Tjerk Veenstra, Francesca Sangiorgi, Vidar Bakker, Klaudia Kuiper, Appy Sluijs 

The Norwegian Sea is crucial for ocean circulation and global climate and has therefore long been a focus in paleoceanography. However, precise dating of sediments has often proved difficult, due to poor preservation and endemism among microfossils and the discontinuous nature of many records. One important Norwegian Sea Site, Ocean Drilling Program (ODP) Site 643, is of particular interest, because of its location and long stratigraphic reach. Previously published magneto- and biostratigraphic age models diverge by ~1 Myr in the lower and middle Miocene, insufficient for global correlations. Here we present new palynological, notably dinoflagellate cyst (dinocyst) data from the lower and middle Miocene of ODP Site 643 and integrate these with existing palynostratigraphies of ODP Site 643. Additionally, we perform 40Ar/39Ar dating on selected tephra layers. We use these, combined with other microfossil bioevents, to reinterpret the existing magnetostratigraphy and construct a revised Oligocene to Recent biomagnetostratigraphic age model for this Site. We confirm the occurrence of three early and middle Miocene hiatuses and one early Pleistocene hiatus and refine their duration. Our age model further indicates a substantially older age for lower and middle Miocene sediments than previous dating has suggested. Finally, we combine our new age model with the integrated palynostratigraphy to provide updated ages of dinocyst bioevents and zone boundaries, which are at least applicable to the Norwegian Sea.