In the austral summer of 2006/7 the ANDRILL MIS (ANtarctic geological DRILLing- McMurdo Ice Shelf) project recovered a 1285. m sediment core from beneath the Ross Ice Shelf near Ross Island, Antarctica. Contained within the upper ~. 600. m of this core are sediments recording 38 glacial/interglacial cycles of Early Pliocene to Pleistocene time, including 13 discrete diatomite units (DU). The thickest of these, DU XI, is ~. 76. m thick, has been assigned an Early Pliocene age (5-3. Ma), and represents several extended periods of uninterrupted sediment accumulation. A combination of geochemical and biological data was used to examine the role of changes in sediment source areas on diatom community composition. Peak-area count-ratios from the data collected with the XRF core scanner include K:Fe and Ti:K. K is lower and Ti higher in the volcanic series sampled. K:Fe is an indicator of the source area of fine-grained sediment delivered to the site by terrestrial and marine sedimentary processes (glacial, fluvial, eolian, gravitational, marine currents), while Ti:K is primarily associated with Ross Sea volcanic sources. A comparison of these two elemental ratios shows an anti-correlation, indicating changes in source rocks with time. Furthermore, relative abundance of the diatom genus, Chaetoceros, varies in the same sense and magnitude as K:Fe, suggesting that climatically-driven changes in sediment source regions are related to variations in abundance. It is suggested that increases in TAM-sourced sediment at the ANDRILL AND-1B site caused increased nutrient levels in the water column, leading to blooms of this genus, which is consistent with current known ecological preferences. © 2012 Elsevier B.V.