The spectacularly preserved Metasequoia wood excavated from the Fossil Forest site of Axel Heiberg Island (Canadian High Arctic) provides a unique window into the δ18O value of Eocene meteoric water via the analysis of fossil cellulose. Seventeen fossilized Metasequoia individuals yielded cellulose with δ18O (Vienna standard mean ocean water [VSMOW]) values ranging from 17.1‰ to 21.4‰ and with a mean value of 19.9‰-strikingly low compared to modern trees of all latitudes. Using established biosynthetic relationships for plant cellulose, we reconstructed the δ18O (VSMOW) value of Eocene meteoric water to be -15.1‰ on Axel Heiberg Island-a value similar to previous determinations of Eocene terrestrial water using varied paleoenvironmental indicators. A wholly temperature-based interpretation of these isotopic results would predict a mean annual temperature of -2.7 °C, but this is incompatible with extremely high forest productivity. Instead, a calculation of isotopic fractionation in moisture transported from the Pacific Ocean north across North America explains the simultaneous arrival of warm air and isotopically depleted moisture in the Eocene Arctic; we suggest that these meridional weather patterns were caused by the absence of a Polar Front during the ice-free Eocene.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Jan 1 2002|
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