GEOGRAPHIC AND MULTIVARIATE ANALYSES OF MACROFLORAL GENUS OCCURRENCES IN PERMIAN ANGARALAND: A REGIONAL LOOK AT THE PALEOPHYTIC/MESOPHYTIC TURNOVER

The Angaran phytogeographic realm in the north-temperate zone of Permian Pangea has long been known to contain a macroflora distinct from equatorial Euramerica and Cathaysia and south-temperate Gondwana. Angara is characterized by the dominance of cordaitids, rarity of lycophytes, and presence of endemic forms such as Rhipidopsis and Angaropteridium. Previous descriptions of geographic variation in floral collections within this region have noted the broadly separate zones of Siberia, the Russian Platform, and Subangara. A geographical approach tracking the spatial occurrence of floristically important genera through the Permian and a quantitative approach examining the similarity of overall floral composition in Angaran collections are attempted here. By examining individual genera and assemblages in the Angaran phytogeographic realm with multivariate techniques, new patterns emerge and are helping to refine our understanding of the global Paleophytic/Mesophytic floral turnover on a regional scale. Angaran macrofloral genus occurrence data were compiled from primary and secondary literature by the Paleogeographic Atlas Project at the University of Chicago. Depositional environment and mode of fossilization are known for most assemblages, allowing comparison of similarly preserved collections with most as floodplain deposits from lowland settings. Detrended correspondence analysis of floral assemblages with more than 5 genera were performed for 3 Permian time bins: (1) Asselian, Sakmarian, Artinskian, (2) Kungurian, Roadian, Wordian, and (3) Capitanian, Wuchiapingian, Changhsingian. During Time 1, floras south of the subtropical Urals are distinct from floras northeast of the Urals in the Verkhoyansk region and Tungusska Basin. During Time 2, assemblages from the Russian Platform are statistical floristic outliers to a similarly structured though less provinicialized Angaran flora. The latest Permian time bin also shows paleolatitudinal separation of eastern Angaran floras from the Uralian and Russian Platform floras. Paleoclimatic (paleolatitude and moisture source) and paleogeographic barriers (the Uralian seaway and highlands) may, in combination, help explain the distinct regions of phytogeographic similarity and dissimilarity through the Permian in Angaraland.