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Lavas from the Samoan volcanic chain show the most enriched geochemical signatures ever documented in oceanic lavas ([sup.87]Sr/[sup.86]Sr as high as 0.7205). In order to test the hypothesis that their source contains a component of recycled upper continental crust, we measured oxygen isotope compositions of olivine phenocrysts from these lavas. Correlations between [delta][sup.18]O of olivines (5.11[per thousand]-5.70[per thousand]) and [sup.87]Sr/[sup.86]Sr and [sup.207]Pb/[sup.204]Pb of whole rocks, as well as Ce/Pb and Nb/Th ratios of whole rocks, indicate that (1) measured [delta][sup.18]O are primary, mantle-derived values, and (2) the enriched mantle source of these lavas contains continental crust or its derivative sediments. The observed trend between [delta][sup.18]O and [sup.87]Sr/[sup.86]Sr can be fit using either clastic marine sediment or continental crust values of [delta][sup.18]O, Sr concentration, and [sup.87]Sr/[sup.86]Sr, but only those for clastic marine sediments are compatible with trace element modeling. We conclude that the enriched source for Samoan basalts was created by sedimentation of continent-derived material into a marine environment, followed by subduction and mixing with ambient mantle. Keywords: oxygen isotopes, Samoa, enriched mantle, EM2, ocean island basalts.

The classical model for the generation of hotspot tracks maintains that stationary and deep-seated mantle plumes impinge on overriding tectonic plates, thereby generating age-progressive trails of volcanic islands and seamounts. Samoa has played a key role in discrediting this model and the very existence of mantle plumes, because early geochronological work failed to demonstrate a linear age progression along this chain of islands. Specifically on Savai'i Island, the bulk of the subaerial volcanics is younger than 0.39 Ma, much younger than the 5.1 Ma age predicted from the classical hotspot model and a constant 7.1 cm/yr Pacific plate motion. This discrepancy led to alternative magma-producing mechanisms that involve the cracking of the lithosphere beneath the Samoan islands, as a result of the extensional regime generated by the nearby Tonga Trench. Here we report [sup.40]Ar/[sup.39]Ar ages from the submarine flanks of Savai'i Island showing that its volcanic construction began as early as 5.0 Ma and in a true intraplate setting. This reinstates Samoa as a primary hotspot trail associated with a deep mantle plume and a linear age progression. Keywords: primary hotspots, [sup.40]Ar[sup.39]Ar geochronology, Pacific plate, plate extension, seamounts, Samoa.

We present the first detailed record of Holocene climate variation from Icelandic eolian soil deposits. Seven cold and windy episodes occurred in Iceland during the past 10 k.y., including the well-documented Little Ice Age (0.6-0.1 ka) and the 8.2 ka event. These windy events are associated with enhanced drift-ice discharge into the North Atlantic, and several are associated with evidence for cold and windy climate in central Greenland and diminution of deep-water formation in the North Atlantic. Although the Arctic Oscillation-North Atlantic Oscillation (AO-NAO) has been invoked to explain other climate teleconnections in the North Atlantic, our paleorecord of windiness in Iceland is not consistent with a persistent negative phase of the AO-NAO. Keywords: Holocene, Iceland, wind transport, grain-size analysis, loess, paleoclimate.