Plant assemblages from the Shafer Peak Formation (Lower Jurassic), north Victoria Land, Transantarctic Mountains

The Jurassic plant fossil record of Gondwana is generally meagre, which renders phytogeographic and palaeoclimatic interpretations difficult to date. Moreover, plant fossil assemblages mainly consist of impressions/compressions with rather limited palaeobiological and palaeoecological significance. We here present a detailed survey of new Early Jurassic plant assemblages from the Pliensbachian Shafer Peak Formation, north Victoria Land, Transantarctic Mountains. Some of the well-preserved fossils yield cuticle. The floras consist of isoetalean lycophytes, sphenophytes, several ferns, bennettitaleans, and conifers. In addition, three distinct kinds of conifer shoots and needles were obtained from bulk macerations. The composition of the plant communities is typical for Jurassic macrofloras of Gondwana, which underscores the general homogeneity of Southern Hemisphere vegetation during the mid-Mesozoic. Altogether, the plant fossil assemblages indicate humid and warm temperate conditions, which is in contrast to recent palaeoclimatic models that predict cool temperate climates for the continental interior of southern Gondwana during the Jurassic. However, there is no evidence for notable soil development or peat accumulation. The environmental conditions were apparently very unstable due to intense volcanic activity that resulted in frequent perturbation of landscape and vegetation, hampering the development of long-lived climax communities. Cuticles of bennettitaleans and conifers show xeromorphic features that may have been beneficial for growth in this volcanic environment.