Evidence for a western extension of the Angaran phytogeographic province in the Early Permian

摘要

A newly described Early Permian fossil plant assemblage in the Mt. Dall conglomerate in the Farewell terrane (Alaska Range, USA) is analyzed from a paleobiogeographic perspective. These data constitute the youngest paleontological dataset yet discovered in this terrane, represent the terrane's only predominantly terrestrial fossil assemblage, and are the only plant macrofossil remains of Early Permian age within a >1500 km radius today. A suite of multivariate statistical analyses comparing the Mt. Dall paleoflora to similar age (Asselian-Artinskian) collections from the Angaran, Euramerican, and Cathaysian Permian phytogeographic provinces reveals that the Mt. Dall paleoflora has a paleobiogeographic affinity with Sub-Angaran plant fossil assem-blages collected from Mongolia and the Primorye region of southeastern Russia. The paleoflora has dual importance in the construction and testing of hypotheses for which there are geographically and temporally few controls.First, these data may be used in association with other faunal and floral remains to test models of the assembly of Alaska, which seek, in part, an understanding of the paleogeographic and lithological origins of accreted terranes. That the Mt. Dall paleoflora indicates mixed Eurasia-North America paleobiogeographic affinity among individual taxa and plots in multivariate space with mid-latitude assemblages on northern Pangea may suggest deposition in that latitudinal belt.Second, contrary to the well-sampled fossil plant-bearing Permo-Carboniferous of the paleotropics and the northeastern temperate Pangean regions (Angaraland), terrestrial biome structure and vegetation type of northwestern Pangea are poorly known. This lack of understanding is due to the paucity of paleofloral collections from this region in this time period and the paleogeographic uncertainty of their position along the ancient active margin of Laurentia. The Mt. Dall paleoflora's phytogeographic affinity to paleobotanical collections from the northeastern Pangea therefore suggests that the Angaran province extended meridionally westward in the Early Permian into what is now northern North America.