The vigor of the glacial Antarctic Circumpolar Current (ACC) and the locations of frontal boundaries are important parameters in understanding to the role of the Southern Ocean in global climate changes. To contribute to our understanding of these parameters we are surveying the provenance of detrital sediments around the perimeter of Antarctica. In general, erosion products from East Antarctica in proximal marine sediments are characterized by highly radiogenic Sr isotopes and erosion products from West Antarctica are reflected by less radiogenic Sr isotopes in proximal marine sediments. Downstream from major oceanic basalt sources such as the Drake Passage and the Kerguelen Plateau, the sediments also have unradiogenic Sr isotopes. Another observation from the pattern of compositional variations within the modern ACC is that terrigenous sediment from Antarctica appears to be injected into the ACC by way of the Ross and Weddell gyres. Sr isotopes from a transect northward from the Ross Sea reveal a general trend that suggests two main sources, one from New Zealand (unradiogenic Sr) and one from Antarctica (radiogenic Sr). In the latitudinal range of the major ACC water flux and where the sediment flux is low (sediment flux data are from Chase et al., 2003, Deep Sea Research II), a departure from the general Ross Sea-to-New Zealand trend toward less radiogenic values indicates the input from a third source, and is approximately coincident with the southern boundary of the ACC. This third component is interpreted to originate from the Pacific-Antarctic ridge to the west. During the LGM the departure from the trend in Sr isotopes is displaced to the north, consistent with a northward displacement of the frontal system. In the Atlantic sector there is also a systematic geographical variation in the Sr isotope composition during both time intervals. Additionally, the differences between LGM and Holocene times reveal some important insights about changing continental contributions to the ACC. For example, more radiogenic Sr in cores starting at about 36oeE (and 57oeS) and moving to the east, appear to indicate a significant increase in sediment flux from the ancient basement of the Antarctic continent (Dronning Maude Land). On the other hand, lower values in a streak running east- west through the center of the Atlantic ACC sector are attributable to greater contributions from the young terrains that border the Drake Passage. It also appears that the Agulhas leakage was reduced in the LGM (Franzese abstract, this meeting), consistent with a northward displacement of the frontal zones, but more data will be needed to confirm this intriguing hint.