A student's emerging genre mastery is a complex process which involves learning not only relevant discoursal forms, but also a wide range of specialist knowledge frames. Recent research suggests that these knowledge frames are acquired during the development of a student's disciplinary identity. Although disciplinary identity clearly contributes to expert genre production, the relationship between the two has to date been relatively underexplored by EAP and ESP scholars. This paper presents a framework that describes how disciplinary identity may be structurally related to the specialist genres students must learn. A case study then examines how one geology student's developing disciplinary identity allowed him to gradually produce a key written genre in geology with increasing expertise. The study suggests that the specialist frames he embodied within his disciplinary identity enabled him to make increasing reference to geology's central concerns and practices, via a typified set of implicit textual cues. Expert writers use these implicit cues to situate themselves and their level of expertise with respect to their community of practice. In conclusion, it is argued that genre-based courses should also include instruction about both the target discipline's specialist knowledge frames as well as the implicit cues that help readers and writers reconstruct them.