Lourinhã Formation

Lourinhã Formation

The Lourinhã Formation is a Late Jurassic geological unit in western Portugal known for diverse paleontological assemblages and important correlations with coeval units in Europe and beyond. It has produced abundant vertebrate, invertebrate, and plant fossils that have informed debates involving Charles Darwin, Richard Owen, Thomas Huxley, and later 20th–21st century paleontologists such as Dmitry Konstantinovich Belyaev, Peter Wellnhofer, José Bonaparte, and Octávio Mateus. The formation has been central to collaborations among institutions like the Natural History Museum, London, the Museu da Lourinhã, the University of Lisbon, the National Museum of Natural History (France), and the Smithsonian Institution.

Geology and Stratigraphy

The formation crops out chiefly in the Lourinhã Municipality on the western margin of the Iberian Peninsula and within basins bounded by structural elements including the Lusitanian Basin, the Hesperian Massif, and the West Iberian Margin. Lithologically it comprises interbedded fluvial sandstones, mudstones, and channel conglomerates with minor limestones and marls that reflect deposition during the Kimmeridgian to Tithonian stages. Stratigraphic subdivisions recognize members and levels correlated with magnetostratigraphy tied to the Geologic Time Scale, chemostratigraphy, and biostratigraphy using indexes like ammonites, ostracods, and palynomorphs documented by researchers affiliated with University of Coimbra and Universidade Nova de Lisboa. Regional mapping has used sequence stratigraphic concepts developed by scholars associated with ExxonMobil research groups and applied basin analysis methods promoted by Peter Vail and the American Association of Petroleum Geologists.

Paleoenvironments and Depositional History

Sedimentology indicates predominantly fluvial-deltaic to coastal plain environments influenced by relative sea-level changes driven by eustatic signals recorded in the Western Interior Seaway literature and compared to regressions described in the Hettangian–Oxfordian records. Paleosols, root traces, and plant macrofossils point to episodes of stabilization interpreted using models from the Sedimentology Society and paleoecological frameworks developed by researchers at the Smithsonian Tropical Research Institute and the Royal Society. Taphonomic studies co-authored by scientists from the University of Cambridge and the Max Planck Society emphasize rapid burial in channelized settings, periodic marine incursions linked to faunal turnovers discussed in works by Jack Sepkoski and David Jablonski, and climatic signals comparable to those reconstructed for contemporaneous units like the Morrison Formation and the Solnhofen Limestone.

Fossil Content

The formation has yielded a diverse vertebrate assemblage including theropod dinosaurs represented by taxa comparable to Allosaurus, Torvosaurus, and small maniraptorans studied by teams from the American Museum of Natural History and the Natural History Museum of Portugal. Sauropods and ornithopods similar to specimens reported from the Morrison Formation, Tendaguru Formation, and collections at the Berlin Natural History Museum appear alongside armoured ankylosaurs and stegosaurs that have been compared to material in the Natural History Museum, Vienna. Marine influence is evidenced by ammonites linked to the work of André Dumortier and bivalves generalized in catalogs at the Natural History Museum of Paris. Microvertebrate and palynological records curated at the British Geological Survey and Instituto Geológico e Mineiro contribute to paleoecological reconstructions used by paleoartists trained at the Royal Ontario Museum. Notable ichnofossils include sauropod and theropod tracksites studied in collaboration with researchers from the University of Glasgow, the University of Barcelona, and the Iberian Peninsula Dinosaur Project. Plant fossils and charcoal interpreted through frameworks developed by the International Paleobotany Association indicate gymnosperm-dominated floras analogous to assemblages in collections at the Natural History Museum, London and the Museum für Naturkunde, Berlin.

History of Research and Stratigraphic Interpretation

Early work in the region involved field surveys by 19th-century geologists linked to institutions like the Geological Survey of Portugal and correspondence networks that included figures from the Muséum national d'Histoire naturelle and the British Museum. Twentieth-century reassessments incorporated methods from stratigraphers at the University of Oxford and paleontologists associated with the Museu de História Natural do Funchal. Important contributions and taxonomic descriptions were published in journals connected to societies such as the Geological Society of London, the Sociedade Geológica de Portugal, and the Deutsche Forschungsgemeinschaft-funded projects. Recent work has emphasized integrated biostratigraphy and radiometric constraints in studies produced by consortia including the European Research Council, the Natural Environment Research Council, and teams collaborating between the University of Coimbra and the Nova School of Science and Technology.

Correlation and Regional Significance

The Lourinhã record is frequently correlated with the Morrison Formation of North America, the Tendaguru Formation of Tanzania, and the Guimarota Coal Mine sequence through shared faunal and floral elements and ammonite zonation frameworks developed by specialists at the International Commission on Stratigraphy and ammonite researchers from the Université de Rennes. These correlations underpin hypotheses regarding Late Jurassic paleobiogeography, driven by plate configurations described in syntheses by the United States Geological Survey and paleogeographic maps produced by the Paleomap Project. The formation has thus become a key reference for comparative studies undertaken by museums and universities including the Field Museum, the University of Porto, and international teams funded by agencies like the European Science Foundation.

Category:Geologic formations of Portugal Category:Jurassic paleontological sites