The Dapingian is the third stage of the
Ordovician system and the first stage of the
Middle Ordovician series. It is preceded by the
Floian and succeeded by the
Darriwilian. The base of the Dapingian (and the top of the
Floian) is defined as the
first appearance of the
conodont species Baltoniodus triangularis which happened about 470 million years ago. The Dapingian lasted for about 2.7 million years until about 467.3 million years ago.[7]
History
The Ordovician was divided into three series and six global stages in 1995. Although at the time of 2005 GSSPs for the overlying
Darriwilian and underlying "
second stage" had already been ratified, definition of a GSSP for the first stage of the Middle Ordovician Series caused difficulties due to the deficiencies of the selected biohorizon and section.[8] The Dapingian was the last Ordovician stage to be ratified, and was initially referred to as an informal and unnamed "third stage" corresponding to the early part of the Middle Ordovician.[9] This third stage was meant to represent the appearance of several major
index fossils. The conodont Baltoniodus triangularis, a species found in Baltica and China, defined the base of the regional Baltoscandian Volkhov stage. Another conodont, Tripodus laevis, defined the base of the Whiterockian stage in western North America. T. laevis was also roughly correlated with the appearance of the
graptoliteIsograptus v. lunatus.[10]
The Whiterock Narrows section in the
Ninemile Formation of
Nevada was the initial suggestion for the GSSP of the third stage, but a 2001 review of the site revealed that its local conodont fauna was misaligned with wider graptolite zonation. In its place, two formal GSSP candidates were proposed.[11] The Niquivil section of
Argentina used another widespread species, Protoprioniodus (Cooperignathus) aranda, as a proxy for B. triangularis, T. laevis, and graptolites, which were absent from the section.[12] The Huanghuachang section of
China hosted a more diverse fauna of index fossils, including Baltoniodus triangularis and biostratigraphically useful graptolites and
chitinozoans.[10] The Huanghuachang section was approved as the GSSP for the third stage in 2006, and was ratified by the
ICS in 2007.[11][9]
Naming
The Dapingian is named after Daping, a village that lies near the Dapingian GSSP at Huanghuachang. The Chenjiahe section, an outcrop with similar rocks, can be found 5 km to the north of the Huanghuachang section.[11] The name of the Dapingian stage was introduced in June 2007 and approved alongside the stage's ratification, beating out earlier suggestions such as "Volkhovian" and "Huanghuachangian".[9]
The Dapingian overlaps with the upper part of the
Arenig, a geologic stage used in
England.[13][14] It is also equivalent to the lower part of the North American
Whiterockian stage,[15] most of the Baltic/Russian
Volkhov stage,[16][17] and the Castlemainian and Yapeenian stages which have been used in Australia.[13] In Baltoscandia, especially in the East Baltic, the global stage boundary corresponds to the bases of the Megistaspis polyphemus Trilobite Zone and probably Isograptus victoriae victoriae Graptolite Zone.[18]
Ocean and climate
At the beginning of the Dapingian, there was a drop in sea level of 70–80 m, which is reflected in the rocks as a well-developed hardground surface in Baltoscandia. Changes in sea level during Dapingian age appear to be associated with short pulses of cooling, which have become a harbinger of much colder climate in the next
Darriwilian age.[19] At the end of the Dapingian, continental ice was growing with small changes in volume caused by changes in the Earth's orbit.[20]
Major events
The
Great Ordovician Biodiversification Event (GOBE) lasted in the Dapingian. Fan et al. (2020) define GOBE as a 20 Myr interval that began in the
Tremadocian and ended in the late Dapingian, although other researchers have suggested different temporal limits.[21]
The extensive
transgression associated with rapid tectonic subsidence, occured at the end of the Dapingian in the
Southern Urals.[22]
The Komstad Regressive Event roughly corresponds to the Dapingian.[23]
Since the Dapingian, there has been a connection between the Afro-European part of
Gondwana and
Baltica, which is confirmed by the discovery of fossils of
cornutanstylophoransPhyllocystis in these regions.[25]Planopora, the oldest сystoporate
bryozoan to form erect, bifoliate colonies, is known from the Dapingian of the Baltic paleobasin,
Leningrad Oblast, Russia.[26]
^Adrain, J. M.; Pérez-Peris, F. (2023). "Funeralaspis n. gen.: a new odontopleurine trilobite from the early Middle Ordovician (Dapingian) of Death Valley, eastern California, USA, and the classification of Ordovician odontopleurines". Zootaxa. 5336 (4): 509–529.
doi:
10.11646/zootaxa.5336.4.3.
PMID38221079.