Geochemistry of sediment cores from the continental shelf of the Gulf of Cadiz (North East Atlantic)

Cores were retrieved in Summer and Autumn 2006 on board of the R/V Mytilus in the framework of the EMIGAS Spanish project ('Zonas de emisión de gases efecto invernadero en los sistemas litorales: influencia de las entradas costeras y del metabolismo bentónico'). Five sampling stations were selected in two different areas: the Bay of Cádiz and its outer region (BOX BC02, BOX BC04, BOX BC05), and the Guadalquivir prodelta (BOX GL03, BOX GL04), which is characterized by a high fluvial supply and a moderate hydrodynamic regime.

Major and minor elements (Si, Ti, Al, Fe, Mg, Ca, K, Na, P, S) and trace elements (Mn, V, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Ba, and Pb) show differences in bulk chemical composition between the two areas. Trace metals (V, Cr, Ni, Cu, Zn, and Pb) are found at lower levels in the Bay of Cádiz compared to the Gualdalquivir prodelta. Relatively high concentrations of Zr and Y, commonly associated with the heavy minerals fraction, are found in the top sediment layers of the Bay of Cádiz, and are attributed to the enrichment of heavy minerals related to selective transport.