International Journal of Astrobiology

Research Article

A comparative study of endolithic microborings in basaltic lavas from a transitional subglacial–marine environment

Claire R. Cousinsa1 c1, John L. Smelliea2, Adrian P. Jonesa1 and Ian A. Crawforda1

a1 Centre for Planetary Sciences, UCL/Birkbeck Research School of Earth Sciences, Gower Street, London WC1E 6BT, UK

a2 British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK

Abstract

Subglacially erupted Neogene basaltic hyaloclastites in lava-fed deltas in Antarctica were found to contain putative endolithic microborings preserved in fresh glass along hydrous alteration boundaries. The location and existence over the past 6 Ma of these lava deltas has exposed them to successive interglacials and subsequent percolation of the hyaloclastite with marine water. A statistical study of the hyaloclastites has found that endolithic microborings are distinctly more abundant within samples that show evidence for marine alteration, compared with those that have remained in a strictly freshwater (glacial) environment. Additionally, correlation between elevation and the abundance of microborings shows endolithic activity to be more prolific within lower elevation samples, where the hyaloclastites were influenced by marine fluids. Our study strongly suggests that endolithic microborings form more readily in marine-influenced, rather than freshwater environments. Indeed, marine fluids may be a necessary precondition for the microbial activity responsible. Thus, we suggest that the chemistry and origin of alteration fluids are controlling factors on the formation of endolithic microborings in basaltic glass. The study also contributes to the understanding of how endolithic microborings could be used as a biosignature on Mars, where basaltic lavas and aqueous alteration are known to have existed in the past.

(Received August 14 2008)

(Accepted November 04 2008)

(Online publication January 05 2009)

Correspondence:

c1 e-mail: c.cousins@ucl.ac.uk