Middle Jurassic rhyolite volcanism of eastern Graham Land, Antarctic Peninsula: age correlations and stratigraphic relationships

Abstract

Silicic volcanism atc.168 Ma has been identified previously on the Antarctic Peninsula, and the Mapple Formation, which includes those volcanic rocks, has been defined and documented from one area of the east coast of Graham Land. Based on age and geochemical criteria, correlations have been made to the extensive Chon Aike Province of South America, which has been demonstrated to be one of the largest silicic volcanic provinces in the world. Rhyolitic and intermediate composition volcanic successions from six separate localities on the east coast of the Antarctic Peninsula are described here and are confirmed as correlatives of the Mapple Formation, based on newly acquired geochronology and field observations. They are dominantly rhyolitic crystal tuffs and/or ignimbrites with ages in the interval 162–168 Ma, overlapping with the age of the Mapple Formation (167–171 Ma) at the type locality. Andesitic agglomerates are also described, which are included in the same event and demonstrate the occurrence of rare intermediate volcanism, which is also seen in the Chon Aike Province. A new group, the Graham Land Volcanic Group, is defined here, and criteria are established which allow the separation of some volcanic successions out of the previously defined Antarctic Peninsula Volcanic Group, which takes no account of tectonic setting, eruption age or geochemistry.

Autochthonous v. accreted terrane development of continental margins: a revised in situ tectonic history of the Antarctic Peninsula

“…This group includes the Graham Land Volcanic Group (Riley et al 2010) of eastern Graham Land and the Mount Poster (Rowley et al 1982) and Brennecke formations (Wever & Storey 1992) in eastern Palmer Land. (2) Intermediate-mafic composition volcanic rocks exposed along the Peninsula's west coast with a fore-or intra-arc origin and characterized by thick volcaniclastic sequences (Riley et al 2010).…”

“…This group includes the Graham Land Volcanic Group (Riley et al 2010) of eastern Graham Land and the Mount Poster (Rowley et al 1982) and Brennecke formations (Wever & Storey 1992) in eastern Palmer Land. (2) Intermediate-mafic composition volcanic rocks exposed along the Peninsula's west coast with a fore-or intra-arc origin and characterized by thick volcaniclastic sequences (Riley et al 2010). Geochronological data from the mainland of the Antarctic Peninsula are sparse (especially in Palmer Land), but existing data indicate that active margin arc magmatism is active subsequent to the Chon Aike Volcanic Group volcanism (Pankhurst et al 2000), ends prior to the Late Neogene to Recent intraplate alkaline volcanism (Smellie 1987) and is most prevalent in the Cretaceous (Rex 1976; Fig.…”

New Paleomagnetic and 40Ar/39Ar Geochronological Results for the South Shetland Islands, West Antarctica, and Their Tectonic Implications

“…Red squares are the sites sampled in this study (slightly modified fromRiley et al, 2010). Red squares are the sites sampled in this study (slightly modified fromRiley et al, 2010).…”

“…Simplified geological map of the Antarctic Peninsula. Red squares are the sites sampled in this study (slightly modified fromRiley et al, 2010).…”

A NanoSIMS Investigation on Timescales Recorded in Volcanic Quartz From the Silicic Chon Aike Province (Patagonia)

“…Locally calderas could be identified as eruption centers (e.g., Aragón et al, 1996). The ignimbrites are intercalated with volumetrically less important rhyolitic lava flows and domes, fallout deposits, debris flow deposits and epiclastic deposits (e.g., Riley et al, 2010). In Patagonia, the province can be divided into two regionseastern Patagonia and the Andean Cordillera.…”