. The pumiceous levels interbedded in the paleobeaches of Half Moon Island, hypothesis about their provenance.

REMESAL, M.B., C.A. PARICA AND A.T. CASELLI

Buenos Aires

Congreso; SCAR; 2010

DNA

Deception Island is a young, active volcano located at the southwestern of the Bransfield Strait, between the Antarctic Peninsula and the South Shetland archipelago. The origin of the Deception volcano is related to a spreading centre in the Bransfield Strait, which is responsible for a line of submerged seamounts. Decepcion is characterized by explosive volcanism and emissions of pumiceous blocks. Deception Island contains a wide range of magmatic compositions (basalt to dacites). After Le Bas et al. (1986), the rocks are classified as basalts (mainly subalkali basalts, rare alkali basalts), basaltic trachyandesites, trachyandesites and trachytes. Interbedded in the paleobeaches of Half Moon Islands thin levels of pumiceous fragments had been recognized. The pumiceous blocks founded in Half Moon Island are brownish with a narrow variation in tones dark to light. Sizes oscillate between 3 cm to 8 cm. The textures are highly vesiculated and vitroclastic. Pumiceous block from Half Moon Island was classified as trachyte (≈65%SiO2, ≥ 7%total alkalis, < 20%Q) bordering the limit of the alkaline series. These samples have a good array in the tendency of a transitional series of Deception Island very close to the new data presented for the pumiceous. The over impose of the chondritic-normalize profile of the pumiceous blocks from Half Moon Island define a trend close similar to differentiated rocks from Deception Island, with enrichment in LREE ([Ce/Yb]cn ≈ 2), flat design for the HREE and the Eu anomaly. 48 Quaternary Southern Ocean intermediate and deep-water circulation