Northernmost record of brontotheres, Axel Heiberg Island, Canada—Implications for age of the Buchanan Lake Formation and brontothere paleobiology

Abstract

Eocene land vertebrates are rare, relatively recent, discoveries in the Canadian Arctic islands. The first were discovered in 1975 in Eocene-aged strata of the Eureka Sound Group, western Ellesmere Island, and reported by Dawson et al. (1976). Subsequent discoveries occurred in the 1980s in similar-aged strata on both Ellesmere and Axel Heiberg islands (Dawson, 1990; Dawson et al., 1993), bringing the tally of vertebrate families to over 30 (Marincovich et al., 1990; Dawson, 1990). The vertebrate fauna provides strong evidence for a mild, equable Arctic climate during the Eocene (Estes and Hutchison, 1980), corroborated by the paleoflora (Axelrod, 1984; Basinger, 1986, 1991). Supporting this interpretation, the isotopically-determined mean ocean surface temperature at 70°N was a mild 10-15°, a far cry from today's mean of −10° (Barron, 1987; Shackleton and Boersma, 1981; McKenna, 1980).