A Chattian-Aquitanian wood flora from the West Siberian Plain: Implications for regional palaeobiogeography

Abstract

In this study, we describe the fossil wood flora from the Chattian (late Oligocene) and Aquitanian (early Miocene) deposits that crop out on the Tym River at Kompasky Bor, Russia. Twenty conifer and angiosperm wood taxa are described and a new fossil wood genus Thujopsoxylon gen. nov. and three new species are established: Thujopsoxylon schneiderianum sp. nov.; Piceoxylon nikitinii sp. nov.; and Crataegoxylon sibiricum sp. nov. The Kompasky Bor flora is important because it is the northernmost Chattian macroflora in the West Siberian Plain so far known and provides constraints on the timing and record of plant taxa migrations between Europe and the West Siberian Plain during the late Paleogene and the early Neogene. The fossil wood and macrofossil taxa are compared to European and other West Siberian Plain floras of similar age to understand the spatial and temporal relationships between these floras. The results of this multivariate analysis indicate floristic exchange between Europe and the West Siberian Plain was not prevalent, but much more pronounced between the West Siberian Plain and the Ural Mountains during the Rupelian and Chattian. Furthermore, elements of the polar broad-leaved deciduous forests appear to have occupied northern Europe and extended into the Ural Mountains and, despite the functionality of the lowland corridors between Europe and the West Siberian Plain, floristic exchange was not pronounced until Miocene time when climate became cooler and drier, signaling the onset of the evolution and development of boreal ecosystems in Europe and the West Siberian Plain.