Sprecher
Beschreibung
We report several cases of upright permineralized stumps and in situ fossil forests preserved in felsic volcanic ash or reworked volcanigenic sediments in upper Permian strata exposed in coastal outcrops of the high-palaeolatitude Sydney Basin, Australia. The stumps are rooted in coal seams and are associated with transported logs and organic debris. Adpression floras in associated fluvial strata host low-diversity macrofloras of glossopterid gymnosperms and various herbaceous sphenopsids and ferns. Although preservational quality of the woods is variable, secondary xylem characters are consistent with glossopterid wood anatomy reported from other regions. Ring characters indicate growth under strongly seasonal conditions. However, intraseasonal perturbations to wood production were common, possibly induced by episodic ash falls and herbivore/pathogen attack. Individual forest horizons contain different stump size profiles suggesting a range of forest maturities are represented. Any one in situ stump horizon should not be considered representative of all Gondwanan Permian forests. In general, glossopterid forests appear to have had characters broadly similar in stature to modern boreal forested mires, with tree densities of over 1300 trunks ha-1. Multiple intercalated coal and tuff beds hosting upright stumps in individual stratigraphic sections indicate repeated burial events and recolonization of the land surface by forested mire vegetation on decadal to centennial time scales. As in modern boreal forests of volcanically active regions, such as the Kamchatka Peninsula, ash falls appear to have provided little impediment to the survival and persistence of the glossopterid coal-forming vegetation through the Guadalupian to Lopingian in humid high-latitude southeastern Gondwana.