Upper Jurassic

Upper Jurassic
Name	Upper Jurassic
Time start mya	163.5
Time end mya	145.0
Period	Jurassic
Preceding	Middle Jurassic
Following	Cretaceous

Upper Jurassic The Upper Jurassic is the latest epoch of the Jurassic Period, spanning from about 163.5 to 145.0 million years ago. It is a major chapter in Mesozoic Earth history marked by distinctive marine transgressions, tectonic reorganizations, and flourishing faunas and floras that influenced later intervals such as the Cretaceous and the Paleogene. Prominent sites, stratigraphic schemes, and researchers across Europe, North America, Africa, Asia, and South America have shaped modern understanding of this interval.

Definition and Subdivision

The epoch is formally subdivided into the Oxfordian, Kimmeridgian, and Tithonian stages, terms originating from European stratigraphy and established through work by stratigraphers associated with institutions such as the Geological Society of London and regional surveys like the British Geological Survey. The Oxfordian was originally defined near Oxford, the Kimmeridgian derives from Kimmeridge Bay on the Isle of Purbeck, and the Tithonian from sections in the Tithonian Alps described by Alpine geologists collaborating with the Geological Survey of Austria. Global frameworks adopted by international bodies such as the International Commission on Stratigraphy integrate regional chronostratigraphic units with biostratigraphic markers like ammonite zonations developed by paleontologists associated with universities including University of Cambridge and University of Heidelberg.

Stratigraphy and Chronology

Stratigraphic frameworks for the epoch rely on marine biostratigraphy (ammonites, belemnites, radiolarians) and integrated chemostratigraphy including stable isotopes employed by research groups at the Max Planck Society and the Smithsonian Institution. Major lithostratigraphic units include the Morrison Formation in North America, the Solnhofen Limestone in Bavaria described by curators of the Bayerische Staatssammlung für Paläontologie und Geologie, and the Portland Stone of southern England documented by the Natural History Museum, London. High-resolution chronologies have been refined using cyclostratigraphy in studies linked to the European Geosciences Union and magnetostratigraphy by teams at the Scripps Institution of Oceanography. Correlation across basins leverages work from the Royal Society-supported projects and regional mapping by national geological surveys such as the United States Geological Survey and the Geological Survey of Canada.

Paleogeography and Climate

Paleogeographic reconstructions depict the breakup of the supercontinent Pangaea into northern Laurasia and southern Gondwana, a process investigated by tectonicists at institutions like the California Institute of Technology and the Institut de Physique du Globe de Paris. Shallow epicontinental seas inundated continental interiors, producing carbonate platforms studied in the Berriasian Basin and the Paris Basin through collaborations between the Muséum national d'Histoire naturelle and regional academies. Climate proxies indicate a generally warm greenhouse climate with regional seasonality reconstructed by researchers from the University of Oxford and the University of Tokyo using palynology and oxygen isotopes. Oceanic circulation changes inferred by modelers at the National Center for Atmospheric Research and the Lamont–Doherty Earth Observatory affected heat and nutrient distribution, shaping biogeographic provinces revealed in specimens curated at the American Museum of Natural History.

Paleontology and Biodiversity

Marine faunas were dominated by diverse ammonites and belemnites described in monographs from the Paleontological Society and cephalopod specialists at the Natural History Museum, London. Reef ecosystems hosted sponges and scleractinian corals documented by researchers at the Smithsonian Tropical Research Institute. Vertebrate assemblages include iconic dinosaurs from the Morrison Formation such as sauropods and theropods cataloged by the Field Museum and the Denver Museum of Nature & Science, while pterosaurs and early birds from Solnhofen were studied by paleontologists associated with the Bayerische Staatssammlung and the Zoological Society of London. Marine reptiles—plesiosaurs and pliosaurs—feature in collections at the Natural History Museum, London and the Royal Belgian Institute of Natural Sciences. Plant assemblages, including conifers and ginkgoaleans, were characterized in floras examined by the Royal Botanic Gardens, Kew and the Smithsonian Institution.

Tectonics and Sedimentation

Tectonic activity included rifting that widened the proto-Atlantic and shaped basins analyzed by geologists at the University of Texas at Austin and the University of Lisbon. Syn-rift and post-rift sedimentary sequences produced siliciclastic successions such as the Upper Jurassic Morrison Formation and carbonate ramps like the Tethyan platform facies studied by the University of Geneva and the University of Padua. Foreland basin deposits adjacent to orogenic belts—outcomes of collisions involving microcontinents documented by the Geological Survey of India—recorded sediment fluxes traced by provenance studies from laboratories at the Geological Survey of Finland and the University of Chile.

Economic Geology and Resources

Upper Jurassic strata host hydrocarbon source rocks and reservoirs exploited by energy companies collaborating with centers like the Norwegian Petroleum Directorate and the Bureau of Ocean Energy Management. Notable petroleum systems include North Sea Jurassic plays evaluated by the Oil and Gas Authority (UK) and basin models developed by the Norwegian Geological Survey. Carbonate and evaporite deposits provided building stones such as Portland Stone used in projects by the City of London Corporation and gypsum exploited in regional industries monitored by national ministries of mining. Phosphate and iron occurrences in basins of Morocco and Brazil were documented in geological reports produced with input from the United Nations Development Programme.

Research History and Key Localities

Historical research owes much to 19th-century figures and institutions: stratigraphic schemes were advanced by members of the Geological Society of London and fieldworkers from the British Museum (Natural History). Key localities include the Solnhofen Limestone, the Morrison Formation, Kimmeridge Bay, and the Tithonian sections of the Alps, each yielding seminal fossils described in publications from the Royal Society and monographs by curators at the Natural History Museum, London and the American Museum of Natural History. Ongoing international collaborations among universities such as the University of Cambridge, Harvard University, and the University of São Paulo continue to refine stratigraphic correlations, paleoenvironmental reconstructions, and the evolutionary history of organisms that thrived during this epoch.

Category:Geologic epochs