Prognon, François (2006) Provenance du matériel à l'origine des formations pédologiques quaternaires des archipels des Bermudes et des Bahamas. PhD thesis Dynamique et ressources des bassins sédimentaires, Centre de Géosciences, ENSMP p.281.

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Abstract

Bermudan and Bahamian Quaternary deposits are characterized by the alternation of carbonates and paleosols. Up to now, atmospheric material, especially Saharan dust, was considered as the main component of the pedological formations.

XRD analyses revealed that the mineralogical assemblage of the Bermuda paleosols predominantly includes carbonates, clay minerals (kaolinite, chlorite and chlorite/vermiculite), phosphates, aluminium and iron oxides/hydroxides. It is strikingly close to the mineralogy of the altered Bermuda volcanic seamount, but noticeably different from the mineralogy of Saharan dust. Moreover, volcanic lithoclasts are found in numerous paleosol profiles all over the archipelago, in all the recorded time intervals. We thus consider the volcanic seamount as the main source of non-carbonate minerals detected in the paleosols. The atmospheric dust reaching Bermuda all along the Quaternary period is probably diluted by the local flux of insoluble residues and remains undetectable by the XRD method.

Carbonates dominate Bahamian paleosols mineralogical assemblage. Recent formations contain kutnahorite, older hydrotalcite. We carried out a comparative study on the evolution of the San Salvador and Eleuthera paleosols mineralogy. It is supported by the speciation model CHESS. It demonstrates that soil evolution is driven by the local platform physiography and by the substratum mineralogy. The clay assemblage from Bahamian paleosols and marine sediments is inherited from North African and probably from North American sources (Mississippi Valley Loess).

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