Abstract
Abstract. We have analyzed marine palynomorphs (mainly dinocysts and acritarchs) from the Integrated Ocean Drilling Program Site U1307 in the Labrador Sea in order to establish a detailed biostratigraphy for the Late Pliocene to Early Pleistocene. We have defined three magnetostratigraphically calibrated dinocyst and acritarch biozones in the Late Pliocene to Early Pleistocene. Zone LS1 is defined based on the highest occurrence of Barssidinium graminosum and covers the later Pliocene from 3.21 to 2.75 Ma. Zone LS2 is marked by the acme of Pyxidinopsis braboi which occurs between 2.75 and 2.57 Ma, thus encompassing the Plio–Pleistocene transition. Finally, zone LS3 extends from 2.57 to 2.23 Ma in the Early Pleistocene. The palynostratigraphic record of IODP Site U1307 is difficult to correlate to other North Atlantic and Nordic Seas sites mainly because of a different temporal resolution and a lack of well-defined biostratigraphic marker species at the basin scale. The low abundance, discontinuous occurrence and asynchronous events of warm-water Pliocene taxa such as Invertocysta lacrymosa, Impagidinium solidum, Ataxiodinium confusum, Melitasphaeridium choanophorum and Operculodinium? eirikianum suggest cooler conditions in the Labrador Sea than elsewhere in the North Atlantic, reflecting a strong regionalism. Nevertheless, as recorded at other locations in the North Atlantic, the disappearance of many dinocyst and acritarch taxa around 2.75 Ma at Site U1307 reflects a strong ecological response accompanying the intensification of the Northern Hemisphere glaciation.
Highlights
The Cenozoic was marked by large tectonic, paleoceanographic and paleoclimatic events that led to the initiation and the intensification of the Northern Hemisphere glaciations
Our study focused on the Plio–Pleistocene transition and was made with considerably higher temporal resolution than that of de Vernal and Mudie (1989), who investigated 155 samples at 1.5 m intervals in the Pliocene to Holocene sediments recovered at Ocean Drilling Program (ODP) Hole 646B
While most sites used with a Late Neogene stratigraphical scheme are under the influence of warm North Atlantic waters, Integrated Ocean Drilling Program (IODP) Site U1307 is situated in the path of the East Greenland Current, which carries relatively fresh and cool waters (Fig. 1)
Summary
The Cenozoic was marked by large tectonic, paleoceanographic and paleoclimatic events that led to the initiation and the intensification of the Northern Hemisphere glaciations (iNHG; Shackleton et al, 1984; Mudelsee and Raymo, 2005). Well-constrained chronologies are crucial for documenting and better understanding the paleoceanographic conditions and paleoclimatic changes around the iNHG at the end of the Cenozoic. Mattingsdal et al (2014) demonstrated the importance of a robust chronology to reconstruct the regional history of the Fram Strait gateway in order to better understand exchange between the Arctic and Atlantic oceans as well as the intensification of glaciation in the Barents Sea and on Svalbard. Uncertainties remain about the relationships between the different ocean gateways, including the Bering Strait, the Canadian Arctic Archipelago, the Fram Strait and Isthmus of Panama and their implication in the intensification of the Northern Hemisphere glaciation (iNHG; Sarnthein et al, 2009; Matthiessen et al, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
