Douglas Harper's Etymology Dictionary
1974, from marginalize + -ation.
Wiktionary
n. The act of marginalizing or something marginalized.
WordNet
n. the social process of becoming or being made marginal (especially as a group within the larger society); "the marginalization of the underclass"; "the marginalization of literature" [syn: marginalisation]
Usage examples of "marginalization".
You are the first folk to pass through them and reach us, since the marginalization began a few weeks ago.
When they avoid mentioning politics or religion, because those topics may be too controversial, they reinforce the marginalization of important American institutions by the institution of the mall.
Any repressed, oppressed, or otherwise marginalized context would show up, disguised, in the text, and the text was a testament to the repression, oppression, marginalization.