FLOODPLAIN PROCESSES THROUGH THE LENS OF UPPER CRETACEOUS PALYNOFACIES ASSEMBLAGES: PRELIMINARY RESULTS FROM DINOSAUR PROVINCIAL PARK, ALBERTA, CANADA

Floodplain deposits can contribute to detailed paleoenvironmental reconstructions through comprehensive palynofacies analysis reinforced by sedimentology. However, the application of such concepts to Late Cretaceous fluvial systems has been limited, resulting in discrete and lower-resolution terrestrial paleoenvironmental reconstructions for this time interval. The Dinosaur Park Formation in Dinosaur Provincial Park (DPP), Alberta, Canada, provides an ideal fluvial setting to apply these concepts. Therefore, this study aims to understand the processes influencing the formation of floodplain deposits during the deposition of the Dinosaur Park Formation through analysis of palynofacies assemblages and to assess their suitability for studying Late Cretaceous environments.

A detailed stratigraphic section, including lithology, grain size, bed thickness and pedogenic features, was recorded of the 47.5 m high outcrop. Rock samples were collected every 0.5 m along a 32 m stratigraphic section dominated by floodplain deposits. After extracting the sedimentary organic matter content from the rock samples, thin sections were prepared and subsequently analyzed microscopically under transmitted white light and UV fluorescence light.

Field observations identified six recurring lithofacies within the measured section, categorized into two facies associations. Facies Association 1 (FA1), representing channel-belt deposits, primarily consists of sandstones. Facies Association 2 (FA2), representing floodplain deposits, features fine-grained facies with varying pedogenic alterations. Palynofacies assemblages show a close relationship with facies associations. FA1 is characterized by opaque phytoclasts and Amorphous Organic Matter, while FA2 is characterized by translucent phytoclasts and palynomorphs. However, pulses of opaque phytoclasts were observed within the floodplain, particularly within the sandy mudstone facies. Overall, our preliminary examination of palynofacies assemblages suggests their potential as a robust proxy for high-resolution paleoenvironmental reconstructions at the DPP.