Palaeoenvironmental reconstruction on the basis of Quaternary palaeo dune sequences on Fuerteventura

Abstract

The volcanic origin of the Canarian Archipelago widely determines the landscape of these islands. Partially near coastal areas the volcanic rocks are covered by dune fields. The eastern Canary Islands show the largest areas of sand deposits. On northern Fuerteventura sandpits and deep incised gully systems allow broader insight into generations of these archives. The dune material originates from the shallow shelf. Hence, the mineral composition is dominated by calcite and aragonite. The outcrops show the layering of several generations of biogenic carbonate sands which are separated by palaeosurfaces. These surfaces suggest soil-forming processes with their (often) reddish colour. Generally, the occurrence of several palaeosurfaces promises a high potential of those Quaternary dune archives on northern Fuerteventura. Former studies focussed on just few quarries being situated in close distances. Differing formation concepts and contradicting chronologies (Middle to Late Pleistocene versus Late Pleistocene) suggest the need for further investigation of landward palaeo dune sections, resulting in a German Research Foundation-funded project (FA 239/18-1) with regard to palaeo dune sequences within the catchments of two barrancos on northern Fuerteventura. Firstly, the project called for defining representative sections of the two catchments for the purpose of working out a correlation and deducing a standard profile; both should be based on stratigraphic findings. Luminescence dating shall contribute to finally establishing a chronostratigraphy. Besides the carbonate sands, the dune archives are influenced by the imprint of volcanic material (tephra, lapilli, and basaltic rock) and Saharan dust. Generally, the archives’ composition and appearance raise several further questions. Are periods of surface formation dependent on reduced sand supply or on changes in climatic conditions? Which soil forming processes contribute to the characteristics of palaeosurface layers? What is the influence of Saharan dust? As dating of lava flows on northern Fuerteventura revealed Middle to Late Pleistocene ages, a further question refers to the relationship between dune formation and volcanic activity. Mainly deduced from findings in the field but also by use of grain size distribution, elemental composition, content of CaCO3, determination of Fed (pedogenic iron), measurements of rock magnetic parameters, analyses of gastropod associations, micromorphological analyses, determination of quartz content via automatic static image analysis with a Malvern Morphologi G3-ID, XRD analyses, and IRSL dating, this thesis provides a chronostratigraphy of palaeo dune archives of northern Fuerteventura deduced from a correlation of sections close to the western coast and sections close to the eastern coast. The derived standard profile shows