High latitude fossil floras provide an important source of data on past climates, since the plants were living in a strongly seasonal light regime and often existed at the limit of their environmental tolerances. Permian and Triassic rocks from Antarctica have been a rich source of biological information because of the large number of sites that have yielded exquisitely preserved fossil plants. Anatomically preserved plants from several sites in the central Transantarctic Mountains and southern Victoria Land provide a unique source of fossil tree ring data. Samples of wood have come from a variety of sites including fluvial settings, permineralized peat deposits, and forest sites where the trees are preserved in situ (in growth position). The wood exhibits distinct growth rings which have been analyzed for paleoclimate signals. Rings from both Permian and Triassic woods are large, ranging from a few millimeters to several centimeters in width, and represent growth rates that are 1–2 orders of magnitude larger than those at high latitudes today. In addition, the structure of the individual rings differs from that seen in modern temperate rings. The presence of a considerable amount of early wood and only 1–2 cells of latewood suggests that light may have been the limiting factor in the growth of these forest trees. Tree ring data, as well as the level of diversity in the Antarctic Permian and Triassic floras are at variance with the majority of paleoclimate models that have been produced for the region.
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