Jurassic Palynology from “The Dinosaur Coast” of Asturias (Lastres Fm., Northwestern Spain): Palynostratigraphical and Palaeoecological Insights

SIMPLE SUMMARY: The Upper Jurassic deposits of the Lastres Formation crop out on the Asturian coast (northwest of the Iberian Peninsula), in the so-called “The Dinosaur Coast”. This formation presents a high abundance of dinosaur remains and other vertebrates. Despite the deep knowledge about its fauna and environment, practically nothing is known about the plant communities that formed the landscape of the region at the end of the Jurassic. We present here the first palynological data of the Lastres Fm., identifying a rich and abundant palynological assemblage formed by more than 60 different taxa. The presence of some taxa with biostratigraphic value suggests a Kimmeridgian-Tithonian age for this formation. On the other hand, the botanical affinities of the taxa found indicate that the vegetation of the “The Dinosaur Coast” of Asturias would not be homogeneous, but would be formed by a mosaic of different plant communities that would adapt to the variety of environments present in the region. The presence of forest areas probably represented a protected environment as well as a food source for herbivorous dinosaurs. Analysis of charcoalified wood remains suggests that palaeofires were relatively recurrent in the study area. ABSTRACT: Abundant fossils of vertebrates (mainly footprints and bones of dinosaurs) and numerous invertebrates occur in the Upper Jurassic deposits of the Lastres Formation in the Asturias region, North of Spain. However, no palynological study has been published from this geological formation; therefore, much palaeoenvironmental and palaeoecological information is still unknown. In this study, a total of 62 morphospecies, belonging to 49 different morphogenera were identified, including pollen, spores, algae remains, fungi spores, dinoflagellates, foraminifera, and scolecodonts from four different locations on the Asturian coast. Spores are the dominant group of palynomorphs, both in diversity and abundance, contrasting with the minor diversity of pollen grains. The age of some key taxa indicates that the palynological assemblage cannot be older than the Kimmeridgian, suggesting a Kimmeridgian-Tithonian age. The botanical and environmental affinities of the pollen and spores indicate the presence of different plant assemblages, including plant communities from humid areas such as the margin of rivers and small freshwater ponds that were dominated by bryophytes and ferns, and a coastal plant community that would inhabit arid areas and would be dominated by gymnosperms and some pteridophytes. The SEM analyses of wood remains show the abundance of charcoalified remains suggesting that wildfires were usual in “The Dinosaur Coast” of Asturias during the Kimmeridgian.