Early Cretaceous wetland of Las Hoyas

Las Hoyas is a remarkable fossil site known for its complete Barremian wetland Biota, which includes approximately 250 species of soft-bodied organisms, plants, and animals (Marugan-Lobón et al., 2023). The site was in a microbasin within the Cuenca sub-basin of the Iberian Domain. The La Huérguina Formation, which yields the fossils, was dated by charophyte and ostracod associations, and was deposited in lacustrine and palustrine environments. The formationis composed of finely laminated limestones that were deposited in depressions formed by tectonic activity over pedogenic and karstified Jurassic marine limestones (Fregenal-Martínez and Meléndez, 2016). The locality was a shallow lake situated in an extensive, perennial, carbonate inland wetland in a subtropical climate. The lake was drained by water rich in carbonates, which was fed by karstic aquifers. The system was seasonally regulated, with water-level oscillations, favoring the growth of microbial mats. The microfacies of mats indicate drier periods with abundant fossil remains, while wetter periods are characterized by microfacies composed of fine carbonate particles and debris with a limited number of fossils. A systematic excavation layer by layer is essential for obtaining detailed information on fossil assemblages and for the recognition of ichnological evidence and microbially induced sedimentary structures.