Sedimentary records can illuminate relationships between the climate, topography and glaciation of West Antarctica by revealing its Cenozoic topographic and paleoenvironmental history. Eocene fluvial drainage patterns have previously been inferred using geochemical provenance data from a ~44-34 Ma deltaic sandstone recovered from the Amundsen Sea Embayment. One interpretation holds that a low relief, low-lying West Antarctic landscape supported a >1500 km transcontinental river system. Alternatively, higher relief topography in central West Antarctica formed a drainage divide between the Ross and Amundsen seas. Here, zircon U-Pb data from Amundsen Sea Embayment sediments are examined alongside known regional bedrock provenance signatures, suggesting that all provenance indicators in the Eocene sandstone derive from West Antarctic rocks. This implies that a local river system flowed off a West Antarctic drainage divide, helping constrain the mid-late Eocene evolution of West Antarctic topography with implications for rifting history and the characteristics of sediments infilling interior basins.