Late Permian forests of the Buckley Formation, Beardmore Glacier area, Antarctica
Knepprath, Nichole Elizabeth
In situ fossil stumps of Glossopteris are preserved in their original growth position in fluvial deposits of the Upper Buckley Formation (Upper Permian) in the Beardmore Glacier, central Transanctarctic Mountains. Roots radiate shallowly from the stumps into immature paleosols that retain their lamination. Of the 87 stumps found, 74 are in two horizons at Lamping Peak separated vertically by approximately one meter. The stumps represent forests that flourished at polar paleolatitudes (>70°S). Mean maximum tree height (~20 m), density (~2000 trees/ha), and basal area (~175 m²/ha) of the fossil forest are comparable to those of modern temperate forests and greater than those of other Permian and some younger high-paleolatitude forests. Regardless of the strongly seasonal polar light regime, conditions were sufficiently warm and wet to promote growth during the growing season. Large woody debris (LWD) and macerated debris are preserved as imprints and coalified plant material although the wood of most of the stumps has been replaced by magnetite. The LWD and macerated plant material are more abundant in Upper than Lower Permian deposits in which no stumps have been found. Because of the paucity of branches and root stocks, LWD is inferred to have been transported, which is consistent with its preferred orientation. Results from stream table experiments suggest orientation of LWD is controlled by flow direction when transported; therefore, orientation of LWD at Lamping Peak likely indicates paleoflow.