Sims Island: first data from a Pliocene alkaline volcanic centre in eastern Ellsworth Land

Although Sims Island (73°17′S/78°33′W), a bedrock peak in Carroll Inlet on the English Coast of eastern Ellsworth Land (Fig. 1), had previously been observed and photographed from the air (e.g. Rowley & Thomson 1990, fig. C.6.2), no landing had been made prior to the present study. Based on proximity and apparent lithological similarities, the island was thought likely to consist of alkaline volcanic rocks similar to those exposed on nearby Snow Nunataks (Fig. 1; e.g. Rowley & Thomson 1990). Smellie (1999) tentatively included it the Bellingshausen Sea Volcanic Group (BSVG), which consists of Miocene-Recent alkaline volcanic outcrops scattered across Alexander Island and eastern Ellsworth Land. More specifically, he provisionally assigned it to the Mount Benkert Formation (MBF), a probable subglacial volcanic succession exposed on three of the four Snow Nunataks. This note is based on observations made and samples collected during a short visit to Sims Island on 6 March 1996.