The role of tephra additions on development of incipient soils from Livingston Island (Antarctic Peninsula) revealed by environmental magnetism

Soils from maritime Antarctica store important information about initialization of pedogenesis and role of the major factors of soil formation. Deciphering the interplay among all contributing agents is however challenging and needs involvement of an interdisciplinary approach. The main aim of our study is to contribute to this goal by assessing mineral magnetic signature of a collection of topsoils from Livingston Island and investigate the major contributing factors, determining their magnetic properties. A set of 23 soil samples from Hurd Peninsula at Livingston Island were studied. Magnetic susceptibility and frequency dependent magnetic susceptibility measurements, anhysteretic remanent magnetization, hysteresis measurements at room temperature and low temperatures were carried out. Identification of magnetic minerals was achieved through thermomagnetic measurements of magnetic susceptibility and analysis of Isothermal Remanence acquisition. Magnetic measurements were supplemented by geochemical analyses of total elemental composition by X-ray fluorescence spectrometry and selective Fe- and Al- extractions by Dithionite-Citrate-Bicarbonate and ammonium oxalate. Magnetic results indicate that composition of iron oxides in soils differs significantly from that of bedrocks by the presence of titianomagnetite fractions with high- and medium Ti-content, while rocks' mineralogy is dominated by paramagnetic minerals or by coarse grained multi-domain magnetite. Titanomagnetite phases were ascribed to the input of tephra additions from the nearby Deception Island. Based on the magnetic susceptibility measurements at low temperatures it was concluded that a fraction of fine grained magnetite is present in soils, in addition to titanomagnetite. Geochemical data reveal differences between the composition of soils and main rock lithologies, which is also assigned to tephra input. Amount of ammonium-oxalate extractable iron and aluminum were higher than that extracted by dithionite, which was attributed to fast tephra weathering in cold polar climate.

Automated summary

This study investigates the mineral magnetic signature of soil samples from Livingston Island and identifies the major contributing factors to soil formation. The results indicate the presence of titanomagnetite fractions and fine-grained magnetite in the soils, which are attributed to tephra input from nearby Deception Island. The geochemical analysis also reveals differences between the composition of soils and main rock lithologies, suggesting the influence of tephra weathering in the cold polar climate.