Contourite Deposition in the North Atlantic Ocean Moderated By Mantle Plume Activity: Evidence from Seismic Reflection Images

Abstract:

It is generally accepted that the strength of Northern Component Water overflow, the ancient precursor of North Atlantic Deep Water, has varied throughout Neogene times. Variations in dynamic support of the lithosphere, due to transient behavior of the Iceland mantle plume, probably control spatial and temporal water depth variations this region. Pathways and intensities of oceanic bottom currents, together with deposition of contourite drifts, are strongly influenced by changing bathymetry. Here, we combine detailed observations of contourite drift deposits from seismic reflection profiles with a chronology of plume activity, to test the relationships between deep-water circulation, sedimentary drift accumulation and mantle convection. We present multi-channel seismic reflection profiles acquired over Bjorn, Gardar and Hatton Drifts in the Iceland Basin and over the northernmost portion of Eirik Drift, east of Greenland. Depositional hiatuses are easily identified and correlated between these high-quality images and nearby boreholes, which allows us to construct history of sedimentation across the North Atlantic Ocean over the past 5 Ma. We observe kilometer-scale westward-migration of Bjorn Drift, which can be explained by varying current strength and sediment supply, probably moderated by fluctuating dynamic support on overall subsidence. We place these observations into a new continuous 55 Ma record of Iceland mantle plume activity. There is compelling evidence to support the hypothesis that variations in mantle convection deep beneath the plates has profound consequences for deep-water flow and sediment deposition at Earth’s surface.