PALEOMYCOLOGY OF THE PRINCETON CHERT

The Princeton Chert, one of several fossil plant localities within British Columbia’s Okanagan Highlands, provides a unique opportunity to understand the diversity of soil and root-associated fungi during the Eocene. The Chert is a 7.5 m thick parautochthonous deposit composed of ~ 49 layers of silicified peat, rhythmically interbedded with sub-bituminous coal and carbonaceous shale. It occurs within the informally named Ashnola shale of the upper Allenby Fm of the Princeton Group, and radiometric dating of an ash within the Chert indicates an age of 48.7 Ma (latest Ypresian to earliest Lutetian). The locality is of great paleobotanical significance owing to the preservation of numerous vascular plant organs permineralized at a cellular level of detail; these include several filicalean ferns, three conifers, and more than 25 angiosperm taxa. Several plants show structural adaptations associated with growth in inundated conditions, and some, like the enigmatic angiosperm Eorhiza arnoldii, are preserved in growth position, signifying that several of the depositional cycles reflect emergent-dominated margins of a backswamp or small lacustrine system. Understanding the paleoecology of the Princeton Chert remains an important goal for paleobotanists, and because soil microbial community composition can provide insight into the hydrogeochemistry of mires, characterizing fungal diversity within the Chert yields new perspectives on both paleoecology and taphonomic processes within this assemblage. The known microfungal community includes pathogens, mutualists, endophytes, and saprotrophs; several of the latter can be attributed to extant ascomycete lineages as a result of high-fidelity preservation of developmental characters. Concurrent work to characterize microbial community structure associated with extant aquatic plants will serve to elucidate ecological processes in inundated soils, thereby improving our interpretations of the paleoecology of this Eocene mire.