Givetian

Givetian
Name	Givetian
Color	#A0A0FF
Timespan	Middle Devonian
Chronostrat	Stage
Lower boundary def	Not formally defined here
Upper boundary def	Not formally defined here

Givetian The Givetian is a Middle Devonian stage of the Paleozoic Era recognized in global chronostratigraphy and used in regional stratigraphic schemes across Europe, North America, Asia, Africa, and Australia. It connects extensively to studies of the Devonian timescale, correlations with the Frasnian and Eifelian stages, and to major paleobiogeographic investigations involving the Old Red Sandstone, Burgess Shale-era comparisons, and basin analyses such as those for the Rheic Ocean margin and the Iapetus Ocean remnants.

Definition and stratigraphic position

The Givetian stage was originally defined by stratigraphers working in the Ardennes region near Givet, France and formalized through discussions at international bodies including the International Commission on Stratigraphy and regional stratigraphic commissions such as the Geological Society of London committees. In global chronostratigraphy the Givetian succeeds the Eifelian and precedes the Frasnian, occupying a distinct interval within the Middle Devonian as employed by the International Chronostratigraphic Chart. Stratigraphic sections used for correlation include key type areas in the Ardennes, reference sections in the Rhenish Massif, and comparative cores from the Moscow Basin and the Michigan Basin.

Chronology and age

Absolute age estimates for the Givetian derive from radiometric work tied to ash beds and isotope stratigraphy conducted by teams associated with institutions such as the Smithsonian Institution, United States Geological Survey, Geological Survey of Canada, and academic groups at universities like University of Oxford and University of Cambridge. Numerical ages commonly cited place the Givetian roughly between ca. 387.7 Ma and 382.7 Ma according to recent iterations of the International Commission on Stratigraphy chart and recalibrations from studies at facilities including the Argonne National Laboratory and the European Centre for Nuclear Research. Correlations use biostratigraphic markers recognized by researchers from the Palaeontological Association and stratigraphers publishing in outlets like the Journal of the Geological Society and Nature Geoscience.

Global stratigraphy and subdivisions

Regional subdivision of the Givetian is implemented differently across provinces: European schemes developed by the Bundesanstalt für Geowissenschaften und Rohstoffe and French stratigraphers use local ammonoid and conodont zones; North American frameworks published by the United States Geological Survey and the Geological Survey of Canada apply brachiopod and coral faunal zonations; Russian stratigraphy from the Russian Academy of Sciences uses distinctive trilobite and conodont successions. Formal subdivision proposals have been debated within the International Union of Geological Sciences and at symposia hosted by institutions such as the Royal Society and the Deutsche Forschungsgemeinschaft. Correlation tools include magnetostratigraphy, sequence stratigraphy, and isotope chemostratigraphy developed in collaborative projects with the European Geosciences Union.

Paleoenvironments and depositional settings

Givetian depositional systems encompass shallow carbonate platforms, reef complexes, siliciclastic shelves, deltaic successions, and deeper basinal shales studied in basins like the Lorraine Basin, Michigan Basin, Taidong Basin, and Western Australia successions. Environmental reconstructions rely on work by paleoclimatologists and sedimentologists from the Max Planck Institute for Chemistry, Scripps Institution of Oceanography, and university departments at Harvard University and University of California, Berkeley. Interpreted settings include fringing reefs influenced by eustatic fluctuations examined alongside global events such as transgressive-regressive cycles tied to data from the International Ocean Discovery Program and sequence studies published in journals like Palaeogeography, Palaeoclimatology, Palaeoecology.

Paleontology and key fossils

The Givetian fossil record is rich in reef-building stromatoporoids, rugose corals, tabulate corals, brachiopods, bivalves, gastropods, cephalopods including early ammonoids, conodonts, trilobites, and vertebrate assemblages such as placoderms and early sarcopterygians studied by paleontologists affiliated with museums like the Natural History Museum, London, American Museum of Natural History, and the Muséum national d'Histoire naturelle. Iconic taxa used for biostratigraphy include diverse conodont genera analyzed by researchers from the Pander Society and trilobite specialists associated with the Paleontological Society. Vertebrate finds contributing to discussions of vertebrate evolution have been reported from localities investigated by teams at Uppsala University, University of Warsaw, and University of Calgary.

Regional occurrences and notable Givetian formations

Prominent Givetian sequences occur in the Ardennes (type region), the Holy Cross Mountains, the Rhenish Massif, the Appalachian Basin including the Catskill Formation transitions, the Moscow Basin limestones, the Canning Basin and Gascoyne successions of Western Australia, and Devonian basins in Morocco and China such as the Daping Formation. These formations have been the focus of field campaigns by teams from the University of Bern, Yale University, University of Adelaide, and national surveys like the Geological Survey of India. Regional monographs and atlases produced by organizations including the British Geological Survey and the Geological Survey of Canada document lithofacies, fossil assemblages, and sequence-stratigraphic frameworks used in hydrocarbon and mineral exploration by companies such as BP, Chevron, and Shell.

Category:Devonian