The youngest pre-caldera volcanism of Deception Island is represented by a thick sequence of subaerial pyroclastic deposits which has been grouped as the Yellow Tuff Formation. Most of these deposits were related to the explosive activity of a central vent which was destroyed during the formation of the caldera. Two members can be distinguished in this formation. The lower member is mainly composed of 1 to 12 m thick massive pyroclastic flow deposits with interbedded air-fall and surge deposits. The upper member is in stratigraphical continuity with the lower member and consists of base surge deposits with minor air-fall and thin pyroclastic flow deposits. The pre-caldera deposits have undergone a palagonitic alteration which produced crystallization of smectites, Fe-oxides, zeolites and calcite.

No abstract

S U M M A R YA paleomagnetic study was carried out on recent volcanic rocks exposed on Deception Island (63.0• S, 60.6• W), Antarctica. Sampling comprised all stratigraphic units exposed on the island, which include basaltic, andesitic and trachytic lavas, basaltic dykes and pyroclastic flows. Following stepwise thermal and alternating field demagnetization procedures, consistent characteristic remanence directions were determined at 21 sites, using principal-component analysis. The overall mean remanence direction for the Deception Island rocks is dec. 348.8• , inc. −73.7• , α 95 = 4.4• , N = 21, and is consistent within error with the geocentric axial dipole direction at the study locality. All of the studied rocks show normal polarity, indicating a Brunhes Chron age. The only available radiometric date of 153 ± 46 kyr agrees with this and suggests a minimum chronostratigraphic span of 100 kyr for the sampled rocks. The site mean directions show a Fisherian distribution and dispersion values compatible with current palaeosecular variation models. No evidence of the far-sided or right-handed effect is found in our data.