National Academies Press: OpenBook

Effects of Past Global Change on Life (1995)

Chapter: Turonian-Coniacian-Santonian

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Suggested Citation:"Turonian-Coniacian-Santonian." National Research Council. 1995. Effects of Past Global Change on Life. Washington, DC: The National Academies Press. doi: 10.17226/4762.
Page 158

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THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 158 SOUTHERN HIGH LATITUDES: A COMPARISON Pseudoaspidiophyllum, Crednaria) locally dominated riparian habitats, where they successfully replaced Ginkgo and Ginkgo- like plants. Figure 9.1 Cretaceous high latitude plant fossil localities on 100 and 80 Ma paleocontinental reconstructions (polar Lambert equal-area projections) of Smith et al. (1981): (a) Northern Albian-Cenomanian localities, 1: Smiley (1966, 1967, 1969a,b), Scott and Smiley (1979); 2: May and Shane (1985), Spicer and Parrish (1986, 1990a,b), Spicer (1987), Parrish and Spicer (1988a,b), Grant et al. (1988), Youtcheffetal. (1987); 3: Jarzen and Norris (1975); 4: Singh (1975); 5: Samylina (1973, 1974), Lebedev (1978). (b) Southern Aptian, Albian-Cenomanian localities, 1: Volkheimer and Salas (1975), Archangelsky (1980), Romero and Archangelsky (1986); 2:Rees and Smellie (1989), Rees (1990), Chapman and Smellie (1992); 3: Dettmann and Thomson (1987), Baldoni and Medina (1989); 4:Truswell (1983), Truswell and Anderson (1985); 5: Truswell (1990); 6: Truswell (1983); 7: Couper (1960), Raine (1984); 8: Douglas and Williams (1982), Dettmann (1986a), Taylor and Hickey (1990), Parrish et al. (1991), Dettmann et al. (1992). (c) Northern Turonian to Maastrichtian localities, 1: Hollick (1930), Spicer(1983); 2: Parrish et al. (1987), Frederiksen et al. (1988), Parrish and Spicer (1988a), Frederiksen (1989), Spicer and Parrish (1990a,b); 3: Hickey et al. (1983); 4: Krassilov (1979). (d) Southern Turonian to Maastrichtian localities, 1: Birkenmajer and Zastawniak (1989); 2: Cranwell (1969), Baldoni and Barreda (1986), Francis (1986), Dettmann and Thomson (1987), Askin (1988a,b, 1989, 1990a,b), Dettmann and Jarzen (1988), Baldoni and Medina (1989), Dettmann (1989), Jarzen and Dettmann (1990), Askin et al. (1991); 3: Truswell (1983), Truswell and Anderson (1985); 4: Truswell (1983); 5: Couper (1960), Mildenhall (1980), Raine (1984, 1988), Daniel et al. (1990); 6: Stover and Partridge (1973), Martin (1977), Dettmann and Jarzen (1988), Dettmann (1989), Dettmann et al. (1992). By the late Cenomanian, angiosperm diversity had risen to more than 60 leaf forms in Alaska (Spicer and Parrish, 1990a). Pollen diversity in Alaska has yet to be fully evaluated. The vegetation was still conifer dominated, but needle-leaved conifers were less common. Angiosperm leaf sizes were large, and leaf physiognomy suggests a wet regime with MATs of 10°C (Parrish and Spicer, 1988a). Tree rings show little intra-annual variation (few false rings). There is some inter-annual variation, possibly a result of fluctuations in water availability (Parrish and Spicer, 1988b), although overall water stress was lacking, based on the high productivity and large cell size. Latewood was very limited, suggesting rapid onset of dark induced dormancy (Spicer and Parrish, 1990b). There are no periglacial sediments known, or any features indicative of sea ice. Turonian-Coniacian-Santonian The Turonian was characterized by a major global sea-level highstand, reducing the nonmarine sedimentary record. By the Coniacian, needle-leaved conifers and Podozamites had disappeared and taxodiaceous foliage was common. Platanoid angiosperms were still dominant along river and lake margins, and had begun to penetrate forests. Cycads were rare or absent, Ginkgo diversity was much reduced, and Equisetites and ferns formed the main ground cover. Leaf margin analysis of a small number of specimens imply an MAT of 13°C at about 78°N (Parrish and Spicer, 1988a), and conditions were still wet although coals are thinner and less numerous. Angiosperm diversity was high, but possibly less than in the Cenomanian. All taxa were deciduous or capable of winter dormancy. Santonian nonmarine sediments are rare and not yet sampled for plant fossils.

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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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