SEDIMENT COMPOSITION IN THE GULF OF CÁDIZ CONTOURITES DURING THE PLEISTOCENE

The Gulf of Cádiz and West Iberian margin are the location of a complex contourite depositional system. Expedition 339 of the Integrated Ocean Drilling Program collected sediment cores from multiple sites in this area. In order to understand the history of the Mediterranean Outflow Water and how it has changed through glacial and interglacial periods, primary mineral phases in each sample were identified. X-Ray diffraction of randomly oriented pressed powders was used to determine bulk mineralogy. Intensity ratios of major mineral phases, relative to quartz, provide a semi-quantitative analysis. Ages were calculated using the shipboard age/depth model and range from 300 ka to 1 Ma, covering multiple glacial cycles. Primary mineral phases include quartz, calcite, dolomite, aragonite, plagioclase, illite, a 7 Å clay, and various interstratified clays. Mineralogical data are consistent with the Expedition 339 shipboard results, and onshore lithologies support interpretation of local provenance. Compositional changes between the upper Mediterranean Outflow Water and lower Mediterranean Outflow Water were considered with respect to glacial and interglacial timescales, and variations were explained in terms of weathering and sediment transport paths. Pattern analysis of the two sites is currently underway.