Abstract

The pumice investigated is found on marine postglacial Strandlines and in prehistoric sites in northern Europe and the western Arctic. The accumulations occur on several Strandlines dating from about 6,700 to about 4,000 radiocarbon yrs B.P. Pumice is most abundant in Norway, and thereafter, Svalbard and the British Isles.

Pumice can remain afloat for a time sufficient to reach its present location from any volcano in the North Atlantic. Transport across the Polar Basin is unlikely. Current circulation and pumice distribution point to Iceland as the probable source of most of the pumice.

The pumice is classified on chemical grounds, according to the Rittmann scheme, into three groups: dacite, rhyodacite, and trachyandesite. Almost all of it is dacite, nearly rhyodacite. The dacitic pumice is divisible into an older (ca. 6,700 yrs), mainly brown variety, and a younger (ca. 4,000 yrs), mainly black variety.

Consideration of the products of all feasible volcanic foci in the Atlantic and North Pacific Oceans, and in the Polar Basin, together with ocean current data, shows that Iceland is the source of the dacitic pumice and probably also of the rhyodacitic variety. The trachyandesitic specimens probably derive from one or more of the smaller Atlantic islands. Although Hekla volcano seems to be the likely source of the dacitic pumice, its inland position is a drawback, and nothing definite can be stated until more data are available on the eruptive history and petrology of other more suitably located volcanos.

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