National Academies Press: OpenBook

Effects of Past Global Change on Life (1995)

Chapter: Eocene

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Suggested Citation:"Eocene." National Research Council. 1995. Effects of Past Global Change on Life. Washington, DC: The National Academies Press. doi: 10.17226/4762.
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Page 165

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THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 165 SOUTHERN HIGH LATITUDES: A COMPARISON record was in the Turonian of the Otway Basin, southeastern Australia (Martin, 1977; Dettmann, 1989). Proteaceae, now a major southern family, also evolved at about this time (Dettmann, 1989). Campanian-Maastrichtian Evolutionary innovation in southern floras reached its zenith during the Campanian. Evidence is provided by a rich palynomorph record from James Ross, Seymour, and adjacent islands near the tip of the Antarctic Peninsula (e.g., Dettmann and Thomson, 1987; Dettmann and Jarzen, 1988; Askin, 1989, 1990b), from New Zealand (e.g., Couper, 1960; Mildenhall, 1980; Raine, 1984), and from the Otway and Gippsland Basins of southeastern Australia (e.g., Stover and Partridge, 1973; Dettmann and Jarzen, 1988; Dettman et al., 1992). The Nothofagaceae (we accept the family status, discussion and references cited in Dettmann et al., 1990) originated in southern high latitudes in the early Campanian, with ancestral pollen types widespread from Australasia to the Antarctic Peninsula. N. brassii, fusca, and menziesii types differentiated soon after (Dettmann et al., 1990), with the southern South America-Antarctic Peninsula area the center of Nothofagus diversification. In the Proteaceae, several types of both Proteoideae and Grevilleoideae occur in Campanian rocks, with earlier arrival of ancestral Proteaceae from northern Gondwana (Dettmann, 1989). The Antarctic Peninsula and New Zealand-southeastern Australia areas were both early Campanian diversification sites for various proteaceaeous groups (Beauprea type, Macadamia type, Gevuina-Hicksbeachia type, Knightia type, Xylomelum type; Dettmann and Jarzen, 1988; Pocknall and Crosbie, 1988; Dettmann, 1989). Gunnera (Gunneraceae) immigrated southward from northern Gondwana via the Antarctic Peninsula in the Campanian (Jarzen and Dettmann, 1990). Members of Myrtaceae may have entered via this route, while Winteraceae appeared in the New Zealand-southeastern Australian area (Dettmann, 1989). Loranthaceae appeared near the end of the Campanian in the Antarctic Peninsula area (Askin, 1989). The conifer Dacrycarpus also appeared in the high southern latitudes during the Campanian (Dettmann, 1989). Diversification continued through the Maastrichtian, with many endemic angiosperm pollen taxa of unknown botanical affinities appearing in the fossil record. This may represent parallel (to northern) development of a herbaceous, "weedy" strategy during the general cooling trend. The latest Maastrichtian on Seymour Island (~66°S) included a short warm interval characterized by members of Bombacaceae, Olacaceae (Anacolosa type), and Sapindaceae (Cupanieae tribe) (Askin, 1989). A rich Campanian leaf assemblage from King George Island (Zamek locality), South Shetland Islands, suggests a broad- leaved forest community, including evergreen types (with thick, coriaceous leaves) and deciduous Nothofagus growing in a subhumid mesothermal climate (Birkenmajer and Zastawniak, 1989). Abundant ferns, especially gleicheniaceous types (Cao, 1989), grew on adjacent moist lowland areas at the end of the Cretaceous. Conifer and angiosperm wood from the James Ross Basin have wide, uniform rings and low latewood-to-earlywood ratios, indicating high productivity, sudden dark-induced dormancy, and no water stress (Francis, 1986). Rainfall of 1000 to 2000 mm/yr was suggested. From the late Maastrichtian (and Early Paleocene) on Seymour Island, dispersed plant cuticle from evergreen foliage of araucarians, Cupressaceae, and podocarp conifers, plus numerous angiosperm taxa, including Myrtaceae and Lauraceae, indicates a wet climate, MAT approximately 8 to 15°C, MAR probably <16°C, and CCM >1°C (G. R. Upchurch, University of Colorado, personal communication, 1990). Podocarpaceous conifer (especially Lagarostrobus)-Nothofagus-Proteaceae forest grew throughout much of the southern high latitudes. Presumed paleoclimates were humid, warm-cool temperate (Cranwell, 1969; Mildenhall, 1980; Francis, 1986; Dettmann and Thomson, 1987; Dettmann and Jarzen, 1988; Askin, 1989, 1990a; Truswell, 1991). Northern Cenozoic Paleocene After a slow start, woody angiosperms became the vegetation dominants, with about 20 leaf taxa in the fossil record. During the Paleocene, angiosperm wood (with vessels and other angiospermous features) occurred on the North Slope of Alaska. Betulaceous-Ulmaceous forms became established, and also migrating from lower latitudes were members of Palmae, Fagaceae, and Juglandaceae (Wolfe, 1966, 1980; Wolfe and Wahrhaftig, 1970; Spicer et al., 1987). "Metasequoia" was the dominant conifer. Leaf assemblages include rare Cupressaceous foliage and the first record of a rosaceous leaf on the Alaskan North Slope (J. A. Wolfe, U.S. Geological Survey, personal communication, 1989). The MAT was 7°C, and the climate periodically dry, although coals were extensive, albeit thin (less than 1-m thick). The palynomorph record has yet to be examined in detail. Eocene The fossil record is good in Canada and southwest Alaska, though poor in northern Alaska. On Ellesmere Island, at 66° N, the vegetation included high-productivity

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What can we expect as global change progresses? Will there be thresholds that trigger sudden shifts in environmental conditions—or that cause catastrophic destruction of life?

Effects of Past Global Change on Life explores what earth scientists are learning about the impact of large-scale environmental changes on ancient life—and how these findings may help us resolve today's environmental controversies.

Leading authorities discuss historical climate trends and what can be learned from the mass extinctions and other critical periods about the rise and fall of plant and animal species in response to global change. The volume develops a picture of how environmental change has closed some evolutionary doors while opening others—including profound effects on the early members of the human family.

An expert panel offers specific recommendations on expanding research and improving investigative tools—and targets historical periods and geological and biological patterns with the most promise of shedding light on future developments.

This readable and informative book will be of special interest to professionals in the earth sciences and the environmental community as well as concerned policymakers.

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