Abstract
The ability to distinguish the features of a chemical sedimentary rock that can only be attributed to biology is a challenge relevant to both geobiology and astrobiology. This study aimed to test criteria for recognizing petrographically the biogenicity of microbially influenced fabrics and fossil microbes in complex Quaternary stalactitic carbonate rocks from Caerwys, UK. We found that the presence of carbonaceous microfossils, fabrics produced by the calcification of microbial filaments, and the asymmetrical development of tufa fabrics due to the more rapid growth of microbially influenced laminations could be recognized as biogenic features. Petrographic evidence also indicated that the development of ”speleothem-like” laminae was related to episodes of growth interrupted by intervals of non-deposition and erosion. The lack of any biogenic characteristics in these laminae is consistent with their development as a result of variation in the physico-chemical parameters that drive calcite precipitation from meteoric waters in such environmental settings.
| Original language | English |
|---|---|
| Pages (from-to) | 883-900 |
| Number of pages | 19 |
| Journal | Astrobiology |
| Volume | 15 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - Oct 2015 |
Bibliographical note
Natural Resources Wales and Steven Griffiths are thanked for access to Caerwys quarry and permission to work on the site. Sebastiaan Edelman and Thomas Logeman assisted with fieldwork and provided some of the field photographs. Bouke Lacet (Sedimentology laboratory, VU University Amsterdam) prepared the thin-sections. Three anonymous reviewers helped to sharpen the manuscript, and Sherry Cady provided valuable editorial advice and assistance. A.T.B. was inspired by Martin Brasier. He dedicates this manuscript to his father’s memory.Keywords
- microfossil
- stromalite
- biogenicity
- carbonate
- tufa
- speleothem
