Fossil woods from the Cross Valley Formation (Paleocene of Western Antarctica): Araucariaceae-dominated forests

•We describe an extensive fossil wood collection from the Cross Valley Formation.•Preservation of the samples is often poor and 52% of the samples were assigned to a fossil-species.•The assemblage is dominated by conifers, particularly Araucariaceae.•Araucariaceae-dominated forests are unusual in the Cenozoic.

Fossil woods from Paleocene sediments of the Cross Valley Formation (Seymour Island, Antarctic Peninsula) are anatomically studied in detail. We collected 64 samples represented almost exclusively by conifers (95%). Only three samples of not determinable angiosperm fossil wood were found. Preservation of the samples is often poor and 52% of the samples were assigned to a fossil-species. The assemblage is dominated by Agathoxylon (Araucariaceae), particularly Agathoxylon antarcticus. Araucariaceae species are joined by Protophyllocladoxylon, Phyllocladoxylon and Cupressinoxylon. Forests dominated by Araucariaceae are unusual during the Cenozoic. The high dominance of Araucariaceae woods may be a reflection of soil conditions, weather and terrain elevation. Our study supports previous hypothesis that identified differences between the paleofloras in each side of the Antarctic Peninsula during the Paleocene.