This paper focuses on the identification of academic written genres from two corpora of reading material in Spanish that undergraduate and graduate university students are assigned in order to access specialized information across seven disciplines, namely Biotechnology, Chemistry, Economics, History, Linguistics, Literature and Physics. A group of 31 genres were identified across the discourses of the disciplines under study. Among the most frequent genres, "Textbook", "Research Article", and "Disciplinary Text", were identified. Contrasting reading material, the importance of the "Research Article" is highly relevant, as it was the only genre that emerged in all seven disciplines. What I am proposing is that, regarding generic variation, there are clear-cut differences in the academic discourse of disciplines pertaining to Social Sciences and Humanities (SS&H) and Basic Sciences (BS), as it has been initially proposed (Parodi 2010a, 2014). However, the findings show that Economics academic discourse is closer to BS in terms of genre constitution.