Thesis advisor: Yvette Kuiper / 40Ar/39Ar single-grain total-fusion ages of muscovite and biotite and one 40Ar/39Ar furnace step-heating age of hornblende from the Tadmuck Brook Schist, Nashoba Formation, and Ball Hill mylonite zone are used to reconstruct the late tectonic and metamorphic history of the Nashoba terrane in eastern Massachusetts. The data fall into three age populations. Age population I (~376-330 Ma) is interpreted as cooling after a migmatization event in the Nashoba terrane, population II (~300 Ma) may be associated with normal movement on the Clinton-Newbury fault, and population III (~267 Ma) is possibly related to cooling of the Rocky Pond Granite. No younger Alleghanian overprint was observed. / Thesis (MS) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.