ABSTRACT: The Theron Mountains, Antarctica expose Jurassic mafic sills intruded into flatlying Permian sedimentary rocks. The sills form some 30% of the outcrop and most are highly concordant, although there are a few cross-cutting relationships. New fieldwork and analytical data suggest that there are four types of sills. The most abundant group chemically correlates with the Mount Fazio Chemical Type of Ferrar tholeiites from Victoria Land, and a second correlates with the distinctive Scarab Peak Chemical Type of Ferrar tholeiites. Two other chemical groups are compositionally close to certain low-Ti-Zr and high-Fe, high Ti-Zr lavas and intrusions in the central Lebombo Monocline and in Dronning Maud Land. The sills provide evidence for long-distance transport of magmas during initial stages of Gondwana break-up.