ABUNDANT IN SITU STUMPS IN HIGH PALEOLATITUDE ANTARCTIC DEPOSITS DOCUMENT HIGH PRODUCTIVITY OF LATE PERMIAN POLAR FORESTS AND TEMPERATE POLAR CLIMATE

The Upper Buckley Formation at Lamping Peak (LP), Beardmore Glacier area, contains stumps recording forests that flourished at 75^° S in the Late Permian. The stumps are in growth position, as indicated by outwardly radiating roots and by surrounding leaf mats of impressions of Glossopteris leaves. The stumps occur in a sequence of stacked crevasse splay sandstones and siltstones deposited in a braided stream system. Shallow roots, immature soil, and presence of Vertebraria root structures adapted for saturated soils are consistent with a high water table and wetland setting.

The stumps of diverse sizes (few cm to 75 cm) occur on two bedding planes separated by 1 m. The more extensively exposed upper bedding plane (LP1) has 53 stumps with a mean diameter at ground level (dgl) of 20.9 cm and a density of 2505 trees ha^-1, whereas LP2 has 21 stumps, mean dgl = 39 cm, and density = 1185 trees ha^-1. Calculated mean maximum heights of trees (method of Niklas, 1994) are 15.4 m (LP1) and 24.6 m (LP2).

Basal area (m² ha^-1) provides a measure of tree abundance that is independent of forest age. LP1,2 forests have higher basal areas (65 and 80 m² ha^-1, respectively based on calculated diameter at breast height, following forestry convention) than modern forests whose basal areas are reported in the literature (e.g., forests in the Rockies, New Zealand, Costa Rica, Germany); only Sequoia and some swamp forests have larger basal areas. LP forests have basal areas calculated using dgl for comparison with fossil forests (LP1 = 173 m² ha^-1; LP2 = 194 m² ha^-1) that are more than twice that reported for Triassic and Jurassic high latitude fossil forests. There is a positive linear relationship between biomass and basal area of modern forests. Extrapolation to the high basal areas of the LP forests suggests that their biomass was as high or higher than most modern forests. These forests demonstrate that warm, moist conditions required for highly productive forests were extant < 1 m.y. before the end of the Permian.