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Title: Geochemistry and micropalaeontology of deep-sea sediments
Author: Abd El-Hameed, A. El-M. T.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1980
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Mineralogical, geochemical and micropalaeontological analyses of DSDP (Deep Sea Drilling Project) sediments from equatorial Pacific, South Atlantic and Caribbean sites have been made. The mineralogical data indicate that terrigenous contribution is relatively unimportant in equatorial Pacific sediments due mainly to the diluting effect of biogenous debris, although it is more pronounced in Late Tertiary sediments of the Caribbean site. The fine grained fractions of the sediments indicate that the majority of illite, kaolinite, chlorite and mixed-layer clay minerals, as well as other non-clay minerals (gibbsite, quartz, feldspar, amphibole, pyrophyllite and talc) are mainly of continental origin and probably derived from a combination of major wind belts and ocean currents. Smectite is most unlikely to be continental in origin and may originate within the ocean basins, possibly from mafic volcanic material. Major element geochemistry has clarified some of the sedimentological processes influencing sedimentation in the equatorial region. The elemental associations (on a carbonate-free basis) suggest that most of the sediments, with a few exceptions, are almost exclusively terrigenous, submarine weathering of basaltic material being a subordinate source. Titanium and aluminium are mainly of continental origin and iron seems to be closely associated with them. Most of the iron is probably contained in clay minerals and some as amorphous hydroxides. Manganese shows a strong non-lithogenous character and is found in the same hosts as iron, possibly as ferromanganese oxide minerals. Phosphorus is primarily biological in origin when corrected on a carbonate- and silica-free basis, but some may be contributed from continental sources and/or basaltic debris. Micropalaeontological analyses of the sediments have shown that the dissolution of calcareous nannofossils is selective and favours the preservation of the more resistant species. Discoasters are more resistant to dissolution than coccolith species. Elevated rates of carbonate dissolution have resulted in the enrichment of carbonate-poor sediments by the solution-resistant discoasters along with a higher proportion of nannofossil fragments. Alternations of carbonate-rich and carbonate-poor sediments are probably related to past climatic variations, with concomintant changes in surface productivity of calcareous plankton and consequently to fluctuations of the CCD (calcite compensation depth). Varying degrees of dissolution and fragmentation of calcareous shells are probably related to decrease in sedimentation rates and to the increase in the residence time of shells at the sediment-water interface.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available