Late Cretaceous Flora in an Ancient Fluvial Environment: The Lower Cantwell Formation at Sable Mountain, Denali National Park, Alaska
Tomsich CS, Fowell SJ, McCarthy PJ. 2010. Late Cretaceous Flora in an Ancient Fluvial Environment: The Lower Cantwell Formation at Sable Mountain, Denali National Park, Alaska. Alaska Park Science. 8(2):21-25
The lower Cantwell Formation is a late Cretaceous fluvial deposit that contains dinosaur footprints and plant fossils. Facies analysis of numerous conglomerate, sandstone, siltstone, and shale successions in the Sable Mountain area in Denali National Park and Preserve reveals a variety of depositional settings, including channels, overbank, crevasse splays, lakes and ponds, located in close proximity on an ancient floodplain or alluvial fan. Plant megafossils preserved in the finer-grained facies indicate that the Cantwell flora was a polar broad-leaved deciduous mixed forest with diverse angiosperms and several deciduous conifers. Combined sedimentological and paleobotanical studies allow identification of distinct local plant communities associated with each of the depositional settings. Dicotyledonous angiosperm leaf morphology was used to compute a mean annual temperature of 51.1ºF (10.6 ºC), a warmest monthly mean of 69.1ºF (20.6 ºC), and a coldest monthly mean of 34.7ºF (1.5 ºC). Climate in this high-latitude region was temperate, with mild winters and considerably warmer summers than those that prevailed on Alaska’s North Slope during the Late Cretaceous.
- Type
- Journal Article
- Authors
- Tomsich, Carla; Fowell, Sarah; McCarthy, Paul
- Units
- DENA
- Keywords
- Ancient Fluvial Environment, Denali National Park and Preserve, Flora, Late Cretaceous, Lower Cantwell Formation, Sable Mountain