There has been considerable interest over the past 15 years in the scientific research article, its schematic structure and how it responds to discourse community expectations. While these features have been widely investigated in numerous disciplines, relatively scant attention has been paid to the important discipline of geology. Moreover, within the sub-discipline of petrology, we find a sub-section as yet unrecognized in the extensive literature on the research article. The 'Geological Setting' (GS), an introductory part-genre occurring before the onset of petrological analysis, is a multi-functional description which frames researchers' results within their geological context. Based on a corpus of 20 articles (10 in French and 10 in English), it is argued that this part-genre is not only a complex of the topography, geological history and characteristics of the research site, but also serves to establish the authors' credentials and authority as experts. This is accomplished not through agentive narratives marking the authors' presence on the site, but through more muted and indirect means. Similarities at the macro-level and general discourse structure are found in both the French and English texts, with important stylistic differences on a local level.