DENSE PERMIAN POLAR FORESTS WITH LARGE TREES: UPPER BUCKLEY FORMATION, CENTRAL TRANSANTARCTIC MOUNTAINS

Upright tree stumps are preserved in their original growth positions in Upper Permian fluvial deposits of the Beardmore Glacier area, Antarctica. These in situ stumps permit reconstruction of tree density and height in Permian forests that were located at ~75 to 80 degrees south. Two forests, 53 stumps on one bed and 21 stumps on an underlying bed, are recorded at Lamping Peak (S 84° 12.6½; E 164° 40.7½); another near Wahl Glacier (S84° 5.7½; E 165° 19.9½) consists of 13 stumps. Well-preserved impressions of Glossopteris leaves are abundant encircling the stumps and comprising the fossil leaf litter. The single leaf type links the stumps to Glossopteris, and the profusion of leaves is consistent with a deciduous habit. The trees grew on bars within a braided stream system and were susceptible to repeated episodes of rapid sediment influx. Sediment buried plant material, surrounded stumps, and halted soil-forming processes. Roots viewed in profile are shallow and laterally extensive, implying a high water table and wet environment. Extrapolation of observed stump densities yields variable tree densities with a maximum of 2400 trees per hectare. Mean tree diameters for the three forests are 21 cm, 39 cm, and 26 cm. The estimated mean maximum tree height is 24.6 m and 15.4 m at Lamping Peak and 18.2 m at Wahl Glacier (method of Niklas, 1994). The Lamping and Wahl forests were more densely packed or had larger trees than younger polar forests. They underscore how benign the Late Permian polar climate was and how well Glossopteris was adapted to the strongly seasonal light regime.