. "9. The Late Cretaceous and Cenozoic History of Vegetation and Climate at Northern and Couthern High Latitudes: A Comparison." Effects of Past Global Change on Life. Washington, DC: The National Academies Press, 1995.
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Effects of Past Global Change on Life
giosperm pollen taxa were present near the tip of the Antarctic Peninsula (about 66°S) by the Albian-Cenomanian (Dettmann and Thomson, 1987; Baldoni and Medina, 1989). There, and slightly further north in southern South America (Volkheimer and Salas, 1975; Archangelsky, 1980; Romero and Archangelsky, 1986), palynomorphs and leaves represent monocotyledonous and several dicotyledonous families, including "higher" (nonmagnoliid) forms that produced triaperturate pollen. Vegetation was predominantly conifer forest with podocarps (Podocarpus and Microcachrys-type) and araucarians, pteridosperms, and diverse fern understory and ground cover.
For a small riparian collection (seven leaf taxa) of mainly microphyllous and deciduous angiosperms from Livingston Island, South Shetland Islands (59 to 65°S), a MAT of 13 to 20°C was suggested (Rees and Smellie, 1989; Rees, 1990), although values are tentative at best for samples with fewer than 20 species (Wolfe, 1971). Associated foliage includes various conifers and cycads. Several types of fern foliage and Equisetites may have formed ground cover, as in northern high latitudes. Well-defined growth rings in conifer wood attests to strong seasonality, but the lack of rings in angiosperm woods (Chapman and Smellie, 1992) is difficult to explain.
Angiosperms had penetrated close to 80°S by the Albian-Cenomanian in New Zealand (in Motuan and Ngaterian Stages; Raine, 1984). They have an older record in southeastern Australia (Aptian Koonwarra beds, ~60°S) based on pollen (Dettmann, 1986a) and foliage (with flowers) of a small, rhizomatous, perennial angiosperm (Taylor and Hickey, 1990).
Douglas and Williams (1982) interpreted the Albian-Cenomanian climate in southern Australia as wet warm temperate, with moderate seasonality, probably seasonally dry, and no widespread winter freezing. Cooler temperatures are indicated by Parrish et al. (1991) based on reevaluation of the Albian vegetation, though not as cold as suggested by oxygen isotope results (Gregory et al., 1989; MAT less than 0°C). Parrish et al. (1991) noted that the Albian floras include both deciduous, thin-cuticled leaves, commonly occurring as mats (e.g., Phyllopteroides), plus more abundant microphyllous conifers and small-leaved bennettitaleans with thick cuticles and specialized stomata for reducing water loss. The latter could have retained their leaves throughout the winter if temperatures were low enough to slow metabolic processes significantly. In their rift valley continental setting, these floras apparently experienced greater MAR than those in coastal sites, and thus with colder winters could contain evergreen taxa.
In contrast, coastal Cenomanian floras from South Island, New Zealand (Daniel et al., 1990) are physiognomically more comparable with coeval floras of Alaska. Many major groups, including angiosperms, conifers, ferns, and cycadophytes, are broad leaved, have mostly thin cuticles, and appear deciduous.
On the coast of East Antarctica, in Prydz Bay, Albian palynomorph assemblages in Ocean Drilling Program (ODP) site 119 drillhole samples (Truswell, 1990) record podocarpaceous conifer vegetation with ferns (especially schizaeaceous types) and various hepatics (liverworts). Fungal material is common. Recycled palynomorphs in Recent muds of the Weddell Sea (Truswell, 1983; Truswell and Anderson, 1985) indicate this vegetational type probably extended around much of the East Antarctic coastal margin.
Albian conifer wood from James Ross Island (~66°S) has uniform rings, absence of false rings, and large earlywood cell size, which indicate little water stress and no evidence for frost (Francis, 1986). Narrow latewood indicates sudden dark-induced dormancy, similar to coeval northern high latitude wood.
All the southern high latitude fossil occurrences fall on the marginal areas of Gondwanaland fragments. Palynomorph assemblages indicate the predominance of temperate, podocarp-araucarian-fern forest vegetation, with lycopod and fern moorland vegetation in some areas (Douglas and Williams, 1982; Dettmann, 1986a,b; Dettmann and Thomson, 1987; Truswell, 1990; Dettman et al., 1992). The nature of the vegetation in the more inland, continental craton of East Antarctica remains unknown.
Palynological data spanning the Turonian-Coniacian-Santonian interval is available from James Ross Island (Baldoni and Medina, 1989) and from the Australasian high latitude sector. The podocarp-araucarian-fern forest association continued through this interval in southern high latitudes. In the Turonian-Coniacian, the abundance and diversity of angiosperms remained low (Dettmann, 1989), while cryptogams were still an important part of the vegetation. This was, however, an important transitional time when the established southern podocarpaceous conifer forest vegetation was diversifying, and new angiosperm families that henceforth typified southern vegetation started to appear. The southern high latitude region was a locus of evolutionary innovation from the Turonian to the end of the Cretaceous. Among the conifers, Lagarostrobus originated in the Turonian (Dettmann, 1989). This important forest tree dominated southern high latitude forests from the Santonian through the Paleocene, and produced pollen (Phyllocladidites mawsonii ) identical to that of the Huon pine (L. franklinii), now restricted to wet, cool temperate, maritime western margins of Tasmania. Dacrydium-type conifers originated in the Coniacian (Dettmann, 1989). Based on the angiosperm pollen record, Ilex (Aquifoliacaeae) originated in southern high latitudes. Its earliest fossil