Evidence for microbial activity in British and Irish Ordovician pillow lavas

John Parnell*, Malcolm Hole, Adrian J. Boyce

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Pyrite is consistently found in modern seafloor vesicular basalts and has a sulphur isotopic composition consistent with microbial activity. We present S isotope data from pyrite in Ordovician pillow lavas at localities across the British Isles, which yield a range of δ34S compositions consistent with two components of sulphur: groundmass pyrite (~0±4‰) and 32S-enriched pyrite in the vesicles (-8‰ to -27‰). The latter are recorded from vesicular lavas in four different terranes, representing different settings at the margins of the Iapetus Ocean. Whereas a component of magmatic sulphate is recognized in the groundmass values, the isotopically light data in the vesicles are consistent with microbial reduction of seawater sulphate in sub-seafloor lavas. This is consistent with modern examples and indicates considerable longevity for this sub-seafloor microbial habitat.

Original languageEnglish
Pages (from-to)497-508
Number of pages12
JournalGeological Journal
Issue number4
Early online date15 May 2014
Publication statusPublished - 1 Jul 2015

Bibliographical note


We are grateful to A. Light, R. Parr, A. Williamson and S. Foster for help with sample collection and processing and the Garda of Co. Leitrim for their understanding. A. McDonald, A. Sandison and C. Taylor provided skilled technical support. J. Ponicka drafted Figure 6. AJB is funded by NERC support of the Isotope Community Support Facility at SUERC. NERC supported the project through facility grant IP-1235-0511.


  • Basalt
  • Deep biosphere
  • Ireland
  • Ordovician
  • Pillow lava
  • Scotland
  • Wales


Dive into the research topics of 'Evidence for microbial activity in British and Irish Ordovician pillow lavas'. Together they form a unique fingerprint.

Cite this