IODP Expedition 307: A high Resolution Record of Contourite Deposition and Palaeoclimatic Forcing on the Eastern Porcupine Seabight (Irish Continental Margin)

In May 2005, IODP Expedition 307 recovered a continuous sediment succession from a contourite drift sequence from the eastern slope of the Porcupine Seabight. The contourite drift is adjacent to the Belgica Mound Province of which one cold-water coral carbonate mound (Challenger Mound) was also drilled. Grain size analysis of 95m of decalcified Pleistocene succession from IODP Core 1318B with 10cm resolution provides a detailed record of grain size distribution and variability for the last ca. 780kyr. Based on these data, we interpret the climatic history, changing sedimentological, hydrodynamic and palaeoenvironmental conditions within the Belgica Mound province. This information, in conjunction with other analyses provides important regional information on palaeoclimatic forcing of sedimentary systems on the NE Atlantic slope during the Pleistocene. So far, End-Member Modelling and sortible silt analyses have identified significant changes in the sedimentary processes over time. Correlations with the abundance of ice rafted detritus highlight the changes in climate condition as the main factor for changes in the slope sedimentary system. Results indicate periods with a coarse sediment input alternating with prolonged finer grained sediment reflecting sporadic periods of along-slope contourite deposition, down-slope terrigenous components and ice- rafted debris linked to ice mass dynamics. Given the proximity of the study area to the Belgica cold-water coral carbonate mounds, this information provide the regional hydrodynamic and paleoenvironmental context for a segment of the mound story and help elucidate carbonate mound growth vs. sediment input throughout the last c. 700kyr. Although much effort has been invested in the study of the Irish offshore in recent years, this project is unique in the detail at which the Pleistocene sediments will be examined and the depth of borehole recovery promises to provide answers on the interplay of sedimentology, climate and oceanography in this area throughout the Pleistocene.