Geochemical characteristics and early diagenesis of recent carbonate mound sediments in the Gulf of Cádiz
Hamaekers, H. (2010). Geochemical characteristics and early diagenesis of recent carbonate mound sediments in the Gulf of Cádiz. MSc Thesis. Katholieke Universiteit Leuven - Faculteit Wetenschappen: Leuven. 159 p. pp.
Cold-water corals have been studied intensively during the last twenty years. They are the framework builders of cold-water carbonate mounds. The CARBONATE project group has been studying coldwater carbonate mounds along the eastern North Atlantic margin, from northern Norway down to Mauretania and the Gulf of Cádiz (Foubert et al. 2008 and Wienberg et al. 2009). Three gravity cores have been taken through carbonate mounds during cruise 64PE284 of RV Pelagia in the carbonate mound provinces SE of Yuma mud volcano and N of Mekness mud volcano (Gulf of Cádiz). They are the subjects of this thesis. No living Scleractinians are found on top of these mounds. Several geochemical, geophysical and petrographical methods have been performed to investigate theinfluence of early diagenesis on the palaeo-environmental record registered in cold-water carbonate mounds.Inductively Coupled Plasma Optical Emission Spectroscopy (ICP – OES), Quantitative X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Magnetic Susceptibility (MS) have been carried out to unravel the palaeo-environmental record and to give a first indication about the presence of early diagenesis. Optical microscopy and Cathodoluminescence (CL) were then used to study the influence of early diagenesis, such as coral and bioclast dissolution and the formation of pyrite and other diagenetic minerals, more in detail on thin sections. Early diagenesis has influenced all the three cores, but the pathways and the impact differ between the cores.Together with the 14C dating, it is possible to reconstruct the palaeo-environmental record from the geochemical results and it seems to be that, in the GoC, the environmental and oceanographicconditions during the warm interstadials of the last glacial period were more favourable for a dominating carbonate fraction than during the present interglacial, the Holocene. Furthermore, the last glacial period in general, seemed to be more favourable for cold-water coral growth in the GoC than during the Holocene.
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