The Santonian is an
age in the
geologic timescale or a
chronostratigraphic stage. It is a subdivision of the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
Epoch or
Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (
million years ago) and 83.6 ± 0.7 mya. The Santonian is preceded by the
Coniacian and is followed by the
Campanian.
[Gradstein ''et al.'' (2004)]
Stratigraphic definition
The Santonian Stage was established by
French geologist
Henri Coquand in 1857. It is named after the city of
Saintes in the region of
Saintonge, where the original
type locality is located.
The base of the Santonian Stage is defined by the appearance of the
inoceramid bivalve
Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...
''
Cladoceramus undulatoplicatus
''Cladoceramus'' is an extinct genus of fossil Marine (ocean), marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the Extant taxon, extant genus ''Pteria (bivalve), Pteria''. They lived in the Santoni ...
''. The
GSSP (official reference profile) for the base of the Santonian Stage is located near
Olazagutia, Spain; it was ratified by the Subcommission on Cretaceous Stratigraphy in 2012.
The Santonian's top (the base of the Campanian Stage) is informally marked by the
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
ion of the
crinoid ''
Marsupites testudinarius''.
A GSSP for the top of the Santonian was ratified in October 2022 in Bottaccione,
Gubbio,
Italy
Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
.
Subdivision
The Santonian is sometimes subdivided into Lower, Middle and Upper Substages. In the
Tethys domain the Santonian is coeval with a single
ammonite biozone: that of ''
Placenticeras polyopsis''.
Biostratigraphy based on inoceramids,
nanoplankton or
forams is more detailed.
References
Notes
Literature
*; 2004: ''A Geologic Time Scale 2004'',
Cambridge University Press
Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...
.
External links
GeoWhen Database - SantonianLate Cretaceous timescale
at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Late Cretaceous
at the website of Norges Network of offshore records of geology and stratigraphy
{{Geological history, p, m
*04
Geological ages
Cretaceous geochronology