Saturday, 15 July 2006

Micromorphology and microprobe study of phosphate reaction in ornithogenic cryosols from Antarctica.

Carlos E.G.R. Schaefer1, Felipe N.B. Simas1, and Bob Gilkes2. (1) Departamento do Solos-Universidade Federal de Višosa, Campus da Universidade, Višosa, Brazil, (2) School of Earth and Geographical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA, Perth, 6009, Australia

Ornithogenic soils rich in phosphorous are widespread in Maritime Antartica, but the phosphatization process in these soils has not been fully considered as a primary soil-forming process in this cold region. This study present a detailed analytical, micropedological and submicroscopical characterization of a toposequence of ornithogenic soils in the vicinity of Arctowski Station, representing sucessive cycles of penguin nesting in the area. SED/EDS and WDS electron microprobe studies were carried out at high magnification. Basic soil chemical data of selected soil attributes shows great enrichment of P, Ca, K and other elements in ornithogenic soils. A granular, sub-rounded structure occurs in all ornithogenic horizons, with varying proportion of coarse fragments, and made of silty partcicles surrounded by phosphate illuvial deposition. These illuviation features characterize a distinct process of phosphatization, with P mobility and neoformation of uncommon secondary phosphates, such as Minyulite and Leucophosphite. Formation of Al-phosphates is related to different poorly crystalline Al forms down the profile, whereas K-Al phosphates are associated with younger leacheates in the upper parts of the ornithogenic soils. WDS and EDS data for the phosphatic plasma are consistent with its illuvial nature.

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