Conodont biostratigraphy


Conodonts are an extinct class of animals whose feeding apparatuses called teeth or elements are common microfossils found in strata dating from the Stage 10 of the Furongian, the fourth and final series of the Cambrian, to the Rhaetian stage of the Late Triassic. These elements can be used alternatively to or in correlation with other types of fossils in the subfield of the stratigraphy named biostratigraphy.

Paleozoic conodonts

Cambrian conodonts

It is suggested that Eoconodontus notchpeakensis can be a marker of the Stage 10 of the Furongian, the fourth and final series of the Cambrian.
In 2006, a working group proposed the first appearance of Cordylodus andresi. Currently the first appearance of E. notchpeakensis is favored by many authors because it is globally widespread and is independent of facies.
The Eoconodontus notchpeakensis proposal would also incorporate a non-biostratigraphic marker to correlate the beginning of Stage 10 globally. A carbon isotope excursion occurs in the lower part of the E. notchpeakensis range.

Ordovician conodonts

Early Ordovician

The base of the Tremadocian, the lowest stage of Ordovician, is defined as the first appearance of Iapetognathus fluctivagus at the GSSP section in Newfoundland.
No conodont species is associated with the Floian, the second stage of the Ordovician.

Middle Ordovician

The base of the Dapingian, the third stage of the Ordovician, is defined as the first appearance of Baltoniodus triangularis.
The base of the Darriwilian, the fourth stage of the Ordovician, lies just above the North Atlantic Microzarkodina parva conodont zone. The base also lies in the upper part of the North American Histiodella altifrons conodont zone.
The Whiterock Stage refers mainly to the early Middle Ordovician in North America. It is often used in the older literature in a global sense. The Whiterock Stage is given a range from 471.8 to 462 m.y.a., spanning close to 10 million years. Officially its start is defined by the potentially lowest occurrence of the conodont Protoprioniodus aranda or Baltoniodus triangularis.

Late Ordovician

No conodont species is associated with the Sandbian, the Katian, nor with the Hirnantian, the fifth, sixth and seventh and final stages of the Ordovician.
Baltoniodus gerdae has been found in the early Sandbian Bromide Formation, in Oklahoma, USA.

Silurian conodonts

Llandovery

The Llandovery epoch lasted from 443.8 ± 1.5 to 433.4 ± 2.8 mya, and is subdivided into three stages: the Rhuddanian, lasting until 440.8 million years ago, the Aeronian, lasting to 438.5 million years ago, and the Telychian.
The Telychian of Estonia can be defined by five conodont zones.

Wenlock

The Wenlock, which lasted from 433.4 ± 1.5 to 427.4 ± 2.8 mya, is subdivided into the Sheinwoodian and Homerian ages.
The Sheinwoodian is defined between the acritarch biozone 5 and the last appearance of Pterospathodus amorphognathoides. The global boundary stratotype point is in Hughley Brook in Apedale, U.K.

Ludlow

The Ludlow, lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and the Ludfordian stage.

Přídolí

Devonian conodonts

Early Devonian

The Early Devonian lasts from 419.2 ± 2.8 to 393.3 ± 2.5 and begins with the Lochkovian stage, which lasts until the Pragian. This spans from 410.8 ± 2.8 to 407.6 ± 2.5, and is followed by the Emsian, which lasts until the Middle Devonian begins, 393.3± 2.7 million years ago.

Middle Devonian

The Middle Devonian comprises two subdivisions, the Eifelian giving way to the Givetian 387.7± 2.7 million years ago.

Late Devonian

Finally, the Late Devonian starts with the Frasnian, 382.7 ± 2.8 to 372.2 ± 2.5, followed by the Famennian subdivision, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian, 358.9± 2.5 million years ago. During that stage, a biologic event occurred. The Famennian is defined by a GSSP Golden Spike located at Coumiac quarry, Montagne Noire, France where there is a biologic abundant occurrence of Palmatolepis triangularis.

Carboniferous conodonts

Mississippian (also known as Lower Carboniferous)

The Tournaisian, the oldest age of the Mississippian contains eight conodont biozones:
The Visean, the second age of the Mississippian, contains four conodont biozones:
The Serpukhovian, the third or youngest age of the Mississippian, includes four conodont biozones:
The Bashkirian, the oldest age of the Pennsylvanian, contains six biozones based on conodont index fossils:
The base of the Moscovian, the second stage in the Pennsylvanian, is close to the first appearances of the conodonts Declinognathodus donetzianus and Idiognathoides postsulcatus. A proposal is to use the first appearance of the conodont Diplognathodus ellesmerensis, but since the species is rare and its evolution relatively unknown, it has not been accepted yet. The Moscovian can biostratigraphically be divided into five conodont biozones:
The top of the Kasimovian, the third stage in the Pennsylvanian, is close to the first appearance of the conodont Streptognathodus zethus. The Kasimovian is subdivided into three conodont biozones:
The base of the Gzhelian, the youngest age of the Pennsylvanian, is at the first appearance of Streptognathodus zethus. The top of the stage is at the first appearance of Streptognathodus isolatus within the Streptognathus "wabaunsensis" chronocline. The Gzhelian stage is subdivided into five biozones, based on the conodont genus Streptognathodus:

Cisuralian

The base of the Asselian stage is at the same time the base of the Cisuralian series and the Permian system. It is defined as the place in the stratigraphic record where fossils of Streptognathodus isolatus first appear. The top of the Asselian stage is at the first appearance of conodont species Streptognathodus postfusus. The Asselian contains five conodont biozones:
The base of the Sakmarian stage is laid with the first appearance of Streptognathodus postfusus in the fossil record. The top of the Sakmarian is defined as the place in the stratigraphic record where fossils of Sweetognathus whitei and Mesogondolella bisselli first appear.
The base of the Artinskian stage is defined as the place in the stratigraphic record where fossils of Sweetognathus whitei and Mesogondolella bisselli first appear. The top of the Artinskian is defined as the place in the stratigraphic record where fossils of Neostreptognathodus pnevi and Neostreptognathodus exculptus first appear.
The base of the Kungurian stage is defined as the place in the stratigraphic record where fossils of Neostreptognathodus pnevi and Neostreptognathodus exculptus first appear. The top of the Kungurian is defined as the place in the stratigraphic record where fossils of Jinogondolella nanginkensis first appear. The Kungurian contains three conodont biozones:
The base of the Roadian is defined as the place in the stratigraphic record where fossils of Jinogondolella nankingensis first appears. The top of the Roadian is at the first appearance of fossils of Jinogondolella aserrata.
The base of the Wordian stage is defined as the place in the stratigraphic record where fossils of Jinogondolella aserrata first appear. The top of the Wordian is defined as the place in the stratigraphic record where Jinogondolella postserrata first appears.
The base of the Capitanian stage is defined as the place in the stratigraphic record where fossils of Jinogondolella postserrata first appear. The top of the Capitanian is defined as the place in the stratigraphic record where Clarkina postbitteri postbitteri first appears. The Capitanian contains three conodont biozones:
The base of the Wuchiapingian stage is defined as the place in the stratigraphic record where Clarkina postbitteri postbitteri first appears. The top of the Wuchiapingian is at the first appearance of conodont species Clarkina wangi.
The base of the Changhsingian stage is at the first appearance of Clarkina wangi. The top of the Changhsingian is at the first appearance of Hindeodus parvus.

Mesozoic conodonts

Early Triassic

The base of the Induan stage is defined as the place in the fossil record where Hindeodus parvus first appears.
The base of the Olenekian is at the lowest occurrence of Neospathodus waageni. It is defined as ending near the lowest occurrences of Chiosella timorensis.

Middle Triassic

The base of the Anisian stage is sometimes laid at the first appearance of Chiosella timorensis in the stratigraphic record. The top of the Anisian is at the first appearance of Neogondolella praehungarica.
The Ladinian is defined by the first appearance of Budurovignathus praehungaricus.

Upper Triassic

The top of the Carnian is at the conodont biozones of Metapolygnathus communisti or Metapolygnathus primitius.
The Norian stage begins at the base of the conodont biozones of Metapolygnathus communisti and Metapolygnathus primitius. The top of the Norian is close to the first appearance of Misikella spp. and Epigondolella mosheri.
The Alaunian, also known as "Middle Norian", is a sub-age in the Upper Triassic. It begins with the first appearance of Cypridodella multidentata. The stage ends with the first appearance of Cypridodella bidentata.