Organic geochemistry of the McMurdo Dry Valleys soil, Antarctica

Abstract

Organic geochemical studies of 12 soil samples from Wright and Taylor Valleys of the McMurdo Dry Valleys (Ross Desert) in southern Victoria Land, Antarctica, were carried out. Long-chain n-alkanoic acids (C 20−C 34), with predominance of even-carbon numbers, were abundant in all the samples. 3-Hydroxy acids (C 8-C 30) with a predominance of even-carbon numbers were found in the samples, together with 2-, ω- and (ω-1)-hydroxy acids. α,ω-Dicarboxylic acids (C 8-C 31) were detected having near-unity values of carbon preference indices; mainly the C 13 dicarboxylic acid predominated. Visual kerogen revealed that amorphous materials are major components (68–98%) with small amounts of very fine coals (2–32%), but no woody and herbaceous materials. The occurrence of mature isomers of steranes and triterpanes, the paucity of n-alkenoic acids and data from the microscopic study suggest that organic components in the soil samples are derived from erosion of Beacon Supergroup sedimentary rocks and past biological debris containing vascular plan waxes as well as wind-transported cyano-bacterial mats, including cyanobacteria, microalgae, bacteria and fungi, rather than from living organisms.