The Penguin Dictionary of Critical Theory. Ed. David Macey. New York: Penguin, 2002.

Archaeology vs. Genealogy

Archaeology deals with what Foucault terms "the positive unconscious of knowledge," that is, with a level of knowledge that eludes the consciousness of individual scientists and thinkers but that provides their theories with underlying rules and structures. (19)

[...]

Genealogy uproots the traditional foundations of history and disrupts history's apparent continuity by concentrating on minor events and "accidents" and insisting that knowledge is always rooted in power, but seeks to deny its own origins. There is no hidden or inner truth in a category such as gender, which is constructed by the bodies of knowledge (sexology, psychoanalysis) that claim to be able to explain it. A genealogical study of gender does not, rather, look forward to the liberaton of some repressed essence but, rather, to a liberation from the categories of gender. ... Although "genealogy" tends to replace Foucault's earlier description of his methodology as an archaeology of knowledge, he appears to regard the terms as being complementary rather than exclusive. (157)