Institut de Physique du Globe de Paris - Pilbara Drilling Project

The Pilbara Drilling Project 2004

A window on "The habitat of life on Early Earth"

* PDP 2: Dresser Formation at North Pole (3.5 Billion years)
Recent discovery: (Philippot et al. Science 2007)

* PDP 1: Tumbiana Formation at Meentheena (2.7 Billion years)
- Stromatolites: morphological evidence of early microbial ecosystems
- metabolisms in Archean ecosystems and evolution of atmospheric system

Two crucial intervals in geologic time were chosen for drilling purposes. The Early Archaean at 3.5 Ga (Dresser Formation, Warrawoona Group), which was dominated by ocean floor hydrothermal processes and/or shallow evaporitic environment and associated forms of life (thermophilic, photosynthetic ?), and the late Archaean at 2.7 Ga (Tumbiana Formation, Fortescue Group) right before the rise in atmospheric oxygen, when methanotrophic life must have been diversifying.

The important issues to be addressed concern:
1) the origin and conditions of formation of the deposits;
2) the composition and temperature of hydrothermal fluids and Archaean seawater and the origins of the carbonaceous material (biogenic vs chemical);
3) the significance of stromatolites and putative microfossils
4) characterizing the metabolisms of early microbial ecosystems (methanotrophs, sulfato-reducers, photosynthesizers ?) and their impact on early Earth environments and atmosphere;
5) the redox and chemical evolution of the Archaean atmosphere;
6) the study of the microbial diversity associated with drilling fluids, and the central and outer parts of cores to address the issue of potential microbial contamination.

The Pilbara Drilling Project was initiated current 2003 as part of a cross-disciplinary research project at the frontier between Microbiology and Earth Sciences entitled 'Modern and Archaean Deep Biosphere: A dual approach based on drill core samples' and supported by the French interdisciplinary program GEOMEX (Geomicrobiology of Extreme Environments, Lopez-Garcia and Philippot, PI).

Diamond drilling was performed in August 2004 and funded by the Institut de Physique du Globe de Paris and the Institut des Sciences de lUnivers (INSU) in partnership with the Geological Survey of Western Australia.

Principal Investigators: Pascal Philippot & Martin van Kranendonk. Geochemistry, Petrology, Mineralogy: Magali Ader, Karim Benzerara, Pierre Cartigny, Marc Chaussidon, Gaston Godard, François Guyot, Kevin Lepot, Béatrice Luais, Bernard Marty, Pascal Philippot, Magali Pujol, Nicolas Rividi, Svetlana Tessalina, Christophe Thomazo, Martin van Kranendonk, Mark van Zuilen. Microbiology: Emmanuelle Gérard, Purificàcion Lopez-Garcia, David Moreira. Organic Geochemistry: Laurent Binet, Sylvie Derenne, Marie-Christine Maurel, Philippe Schaeffer. Paleomagnetism: Jean Besse, Charles Poitou, Jean Pierre Valet