TheDapingian is the third stage of theOrdovician system and the first stage of theMiddle Ordovician series. It is preceded by theFloian and succeeded by theDarriwilian. The base of the Dapingian (and the top of theFloian) is defined as thefirst appearance of theconodont speciesBaltoniodus triangularis which happened about 471.3 million years ago. The Dapingian lasted for about 1.9 million years until about 469.4 million years ago.[7]
The Ordovician was divided into three series and six global stages in 1995. Although at the time of 2005 GSSPs for the overlyingDarriwilian 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 majorindex fossils. The conodontBaltoniodus 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 thegraptoliteIsograptus v. lunatus.[10]
The Whiterock Narrows section in theNinemile Formation ofNevada 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 ofArgentina used another widespread species,Protoprioniodus (Cooperignathus) aranda, as a proxy forB. triangularis,T. laevis, and graptolites, which were absent from the section.[12] The Huanghuachang section ofChina hosted a more diverse fauna of index fossils, includingBaltoniodus triangularis and biostratigraphically useful graptolites andchitinozoans.[10] The Huanghuachang section was approved as the GSSP for the third stage in 2006, and was ratified by theICS in 2007.[11][9]
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 theArenig, a geologic stage used inEngland.[13][14] It is also equivalent to the lower part of the North AmericanWhiterockian stage,[15] most of the Baltic/RussianVolkhov 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 theMegistaspis polyphemus Trilobite Zone and probablyIsograptus victoriae victoriae Graptolite Zone.[18]
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 nextDarriwilian 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]
TheGreat Ordovician Biodiversification Event (GOBE) lasted in the Dapingian. Fan et al. (2020) define GOBE as a 20 Myr interval that began in theTremadocian and ended in the late Dapingian, although other researchers have suggested different temporal limits.[21]
The extensivetransgression associated with rapid tectonic subsidence, occurred at the end of the Dapingian in theSouthern 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 ofGondwana andBaltica, which is confirmed by the discovery of fossils ofcornutanstylophoransPhyllocystis in these regions.[25]Planopora, the oldest сystoporatebryozoan 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.
.jpg)
