The volcanic record in the ANDRILL McMurdo Ice Shelf AND-1B drill core

Abstract

he 1285 m thick MIS core offers an invaluable opportunity to obtain a detailed record of volcanism in McMurdo Sound. Volcanic stratigraphy and preliminary petrologic data on volcanic rocks in the AND-1B core are reported here. Remarkable volcanic deposits include: a) a phonolitic pumice layer found at ≈85 mbsf which is not correlated to any known vent onshore; b) a black well sorted volcanic sands succession (132.83 to 146.79 mbsf) interpreted as being derived mainly from subaerial Hawaiian/Strombolian eruptions; c) a thick volcanic succession in the middle part of the core with an interbedded submarine lava flow. The flow may be derived from a nearby (≈4 km) vent on the seafloor according to average length of the lavas with similar composition; d) deeply altered tuffs and minor sandstone below 1220 mbsf. Diagenesis and intense alteration at depths >600 mbsf, hamper the interpretation of magma evolution and provenance.