DREDGED BASALT FROM GIACOMINI SEAMOUNT

DURING the cruise in July 1965 of the RV Acona of the University of Alaska Institute of Marine Science, two angular blocks of basalt (15×12×5 cm3 and 20×15×9 cm3) were dredged from the summit area of Giacomini Seamount (56°24′ N, 146°34′ W), at a depth of 790 m (Fig. 1). Several hundred igneous, metamorphic and sedimentary pebbles, cobbles and boulders were also recovered in the dredge haul; they showed a wide range of rounding and a very thin coating of manganese oxide, and were very similar to those recovered from the summit areas of Gilbert, Miller, Pratt and Ga-3 Seamounts in the Gulf of Alaska Seamount Province, as previously reported by Menard1 and others. Menard concluded that these gravels were ice-rafted glacial drift, an interpretation which is strongly supported by the presence of faceted and striated rocks among the Giacomini erratics. © 1969 Nature Publishing Group.