National Academies Press: OpenBook

Effects of Past Global Change on Life (1995)

Chapter: Albian-Cenomanian and Early Angiosperms

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Suggested Citation:"Albian-Cenomanian and Early Angiosperms." 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 159
Suggested Citation:"Albian-Cenomanian and Early Angiosperms." 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 160
Suggested Citation:"Albian-Cenomanian and Early Angiosperms." 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 161
Suggested Citation:"Albian-Cenomanian and Early Angiosperms." 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 162
Suggested Citation:"Albian-Cenomanian and Early Angiosperms." 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 163

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THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 159 SOUTHERN HIGH LATITUDES: A COMPARISON Campanian-Maastrichtian The North Slope of Alaska was at 85°N, and overall diversity had dropped in the megafloral record. Woody angiosperm diversity was much reduced, and conifers were represented by only two foliage and five wood taxa (Spicer and Parrish, 1990a). Equisetites and ferns continued as the main ground cover, and Ginkgo and cycads had disappeared. Fires were common. The palynomorph record is extensive and indicates angiosperm predominance in the Maastrichtian, with a high turnover and spatial heterogeneity of taxa (Frederiksen et al., 1988; Frederiksen, 1989). Plants that produced the pollen are believed to be mostly herbaceous and probably annuals. A ''weedy" strategy would have been favored by short growing seasons and fire disturbance. Some woody Betulaceae/Ulmaceae may have been present (Parrish et al., 1987; Frederiksen, 1989); however tree taxa were dominated by the limited variety of conifers. Tree rings reflect lower productivity and more inter-and intra-annual variation. Latewood to earlywood ratios are higher, suggesting thermal limitations on spring or summer growth rather than sudden dark-induced dormancy (Spicer and Parrish, 1990b). By the Maastrichtian, vegetation was more open, with smaller trees. The environment was not as wet, with periodic drying. Vegetational physiognomy suggests MAT of 2.5 to 5°C and long, cold, dark winters with CMM probably no lower than -11°C (Parrish et al., 1987). Large wood tracheid cross sections, and lack of periglacial sediments, imply no severe drought or freezing (Spicer and Parrish, 1990b). On the Alaskan Peninsula, conditions were much warmer than on the North Slope. Leaf forms were more advanced, migration from the south continued, and Nilssonia (cycad) and diminuitive Ginkgo dawsonii survived into the Maastrichtian (Hollick, 1930; Spicer, 1983). Floras in both the northern (Spicer, 1989b) and the southern (Askin, 1988b, 1990a; Raine, 1988) high latitudes apparently did not suffer any major ecological trauma at the Cretaceous-Tertiary boundary. Southern Cretaceous Albian-Cenomanian and Early Angiosperms By the middle Cretaceous, angiosperms were well established in the southern high latitudes. At least 8 an Figure 9.2 Cenozoic high latitude plant fossil localities on 40 and 10 Ma paleocontinental reconstructions (polar Lambert equalarea projections) of Smith et al. (1981): (a) Northern Paleocene-Eocene localities, 1: Wolfe (1980); 2: Wolfe (1966), Wolfe and Poore (1982); 3:Hickey et al. (1983), Parrish et al. (1987), Frederiksen et al. (1988), Spicer and Parrish (1990a); 4: Francis and McMillan (1987); 5: Schweitzer (1974). (b) Southern Paleocene-Eocene localities, 1: Stuchlik (1981), Lyra (1986), Torres and LeMoigne (1988), Birkenmajer and Zastawniak (1989), Torres and Meon (1990); 2: Dusen (1908), Fleming and Askin (1982), Zamaloa et al. (1987), Askin (1988a,b, 1990b), Case (1988), Askin et al. (1991); 3. Mohr, 1990; 4:Kennett and Barker (1990), Mohr (1990); 5: Truswell (1983). (c) Northern Oligocene to Pliocene localities, 1: Sher et al. (1979); 2: Hills et al. (1974); 3: Hills and Matthews (1974), Kuc et al. (1983); 4: Funder et al. (1985). (d) Southern Oligocene to Pliocene localities, 1: Palma- Heldt (1987), Birkenmajer and Zastawniak (1989); 2:Mohr (1990); 3: Askin and Markgraf (1986), Carlquist (1987), Webb etal. (1987), Harwood (1988); 4:Kemp (1975), Kemp and Barrett (1975), Truswell (1983, 1990), Hill (1989), Mildenhall (1989).

SOUTHERN HIGH LATITUDES: A COMPARISON Figure 9.3 Vegetational trends and global change for the Cretaceous northern high latitudes. Sources of data are in the text. Sea-level curve for Figures 9.3 to 9.6 from Haq et al. (1987); time scale for Figures 9.3 and 9.4 from Harland et al. (1990). THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 160

SOUTHERN HIGH LATITUDES: A COMPARISON Figure 9.4 Vegetational trends and global change for the Cretaceous southern high latitudes. Isotope data for Figures 9.4 and 9.6 from Barrera et al. (1987), Stott and Kennett (1990), and Stott et al. (1990). THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 161

SOUTHERN HIGH LATITUDES: A COMPARISON Figure 9.5 Vegetational trends and global change for the Cenozoic northern high latitudes. Time scale for Figures 9.5 and 9.6 from Berggren et al. (1985) and Harland et al. (1990). THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 162

THE LATE CRETACEOUS AND CENOZOIC HISTORY OF VEGETATION AND CLIMATE AT NORTHERN AND 163 SOUTHERN HIGH LATITUDES: A COMPARISON Figure 9.6 Vegetational trends and global change for the Cenozoic southern high latitudes.

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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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