Geochronology/Paleozoic

Geochronology/Paleozoic is the science of applying dates in the past to Paleozoic rocks. In many situations fossils and artifacts may yield dates applicable to the rocks they occur in.

Notations
Let
 * 1) ALMA represent the Asian Land Mammal Age,
 * 2) b2k represent before AD 2000,
 * 3) BP represent before present, as the chart is for 2008, this may require an added -8 for b2k,
 * 4) ELMMZ represent the European Land Mammal Mega Zone,
 * 5) FAD represent first appearance datum,
 * 6) FO represent first occurrence,
 * 7) Ga represent Gegaannum, billion years ago, or -109 b2k,
 * 8) GICC05 represent Greenland Ice Core Chronology 2005,
 * 9) GRIP represent Greenland Ice Core Project,
 * 10) GSSP represent Global Stratotype Section and Point,
 * 11) HO represent highest occurrence,
 * 12) ICS represent the International Commission on Stratigraphy,
 * 13) IUGS represent the International Union of Geological Sciences,
 * 14) LAD represent last appearance datum,
 * 15) LO represent lowest occurrence,
 * 16) Ma represent Megaannum, million years ago, or -106 b2k,
 * 17) NALMA represent the North American Land Mammal Age,
 * 18) NGRIP represent North Greenland Ice Core Project, and
 * 19) SALMA represent South American Land Mammal Age.

"The term b2 k [b2k] refers to the ice-core zero age of AD 2000; note that this is 50 years different from the zero yr for radiocarbon, which is AD 1950 [...]."

Chronostratigraphy
Dates have been assigned to specific geologic stratigraphy frames, columns, or columnar units.

Permian
The Permian lasted from 299.0 ± 0.8 to 251.0 ± 0.4 Mb2k.

The extinct group of animals, the Gorgonopsia, is named after the Gorgons and formed the dominant group of carnivores in the Middle and Upper Permian.

Phosphoria Formation
The Phosphoria Formation of the western United States represents some 15 million years of sedimentation. It reaches a thickness of 420 metres and covers an area of 350,000 km2.

Asselian
In the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian, a subdivision of the Cisuralian Epoch or Series, which lasted between 298.9 and 295 million years ago (Ma), preceded by the Gzhelian (the latest or uppermost subdivision in the Carboniferous) and followed by the Sakmarian.

The Artinskian still encompasses most of the lower Permian – its current definitions are more restricted. The Asselian is named after the Assel River in the southern Ural Mountains of Kazakhstan and Bashkortostan.

The base of the Asselian Stage is at the same time the base of the Cisuralian Series and the Permian System, defined as the place in the stratigraphic record where fossils of the conodont Streptognathodus isolatus first appear, where the global reference profile for the base (the GSSP or golden spike) is located in the valley of the Aidaralash River, near Aqtöbe in the Ural Mountains of Kazakhstan. The top of the Asselian stage (the base of the Sakmarian stage) is at the first appearance of conodont species Streptognathodus postfusus.

The Asselian contains five conodont biozones:
 * zone of Streptognathodus barskovi
 * zone of Streptognathodus postfusus
 * zone of Streptognathodus fusus
 * zone of Streptognathodus constrictus
 * zone of Streptognathodus isolatus

Late Paleozoic icehouse
The late Paleozoic icehouse, formerly known as the Karoo ice age, was the climate state 360–260 million years ago (Mya) in which large land-based ice-sheets were present on Earth's surface.

"The late Paleozoic icehouse was the longest-lived ice age of the Phanerozoic, and its demise constitutes the only recorded turnover to a greenhouse state."

Rotliegend
The Rotiegend lasted from 302 Ma to 260 Ma.

Late Pennsylvanian
The Pennsylvanian also known as Upper Carboniferous or Late Carboniferous is, in the International Commission on Stratigraphy (ICS) geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period, lasting from roughly 323.2 million years ago to 298.9 million years ago. As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few hundred thousand years. The Pennsylvanian is named after the U.S. state of Pennsylvania, where the coal-productive beds of this age are widespread.

Gzhelian
The Gzhelian is an age in the International Commission on Stratigraphy (ICS) geologic timescale or a stage in the stratigraphic column, the youngest stage of the Pennsylvanian, the youngest subsystem of the Carboniferous. The Gzhelian lasted from 303.7 to 298.9 Ma. It follows the Kasimovian age/stage and is followed by the Asselian age/stage, the oldest subdivision of the Permian system.

The Gzhelian is more or less coeval with the Stephanian Stage of the regional stratigraphy of Europe.

The base of the Gzhelian is at the first appearance of the Fusulinida genera Daixina, Jigulites and Rugosofusulina, or at the first appearance of the conodont Streptognathodus zethus. The top of the stage (the base of the Permian system) is at the first appearance of the conodont Streptognathodus isolatus within the Streptognathus "wabaunsensis" chronocline. Six meters higher in the reference profile, the Fusulinida species Sphaeroschwagerina vulgaris aktjubensis appears.

A Global Boundary Stratotype Section and Point (golden spike) for the Gzhelian Stage is yet lacking. A candidate is a section along the Ussolka river (a tributary of the Belaya river) at the edge of the hamlet of Krasnoussolsky, about 120 kilometres south-east of Ufa and 60 kilometres north-east of Sterlitamak (in Bashkortostan).

The Gzhelian Stage is subdivided into five biozones, based on the conodont genus Streptognathodus:
 * Streptognathodus wabaunsensis and Streptognathodus bellus Zone
 * Streptognathodus simplex Zone
 * Streptognathodus virgilicus Zone
 * Streptognathodus vitali Zone
 * Streptognathodus simulator Zone

Kasimovian
The Kasimovian is a geochronologic age or chronostratigraphic stage in the International Commission on Stratigraphy (ICS) geologic timescale, the third stage in the Pennsylvanian (late Carboniferous), lasting from 307 to 303.7 Ma. The Kasimovian saw an extinction event which occurred around 305 mya, referred to as the Carboniferous Rainforest Collapse. and corresponds to the Missourian in North American geochronology and the Stephanian in western European geochronology.

Carboniferous
The Carboniferous began 359.2 ± 2.5 Mb2k and ended 299.0 ± 0.8 Mb2k.

Pennsylvanian
"Specimens of Calamites cistii (Sphenophyta; Pennsylvanian, France) are described showing endophytic cavities, located in the outer cortex of the stem, a tissue that is rarely preserved. This new record shifts the appearance of this behavior back 60 Ma." Two "specimens of the arborescent Calamites cistii (Sphenophyta) [were] collected from the Pennsylvanian basin of Graissessac (Hérault, France)". "The specimens belong to the species Calamites cistii Brongniart, 1828 (Sphenophyta). They are housed in the Collections de Paléobotanique, Service général des Collections, University Montpellier 2 (LPM)."

The Pennsylvanian lasted from 318.1 ± 1.3 to 299.0 ± 0.8 Mb2k.

Mississippian
The Mississippian lasted from 359.2 ± 2.5 to 318.1 ± 1.3 Mb2k.

Prolecanites gurleyi is an index fossil of the Mississippian.

Middle Mississippian
"This species has been consistently identified with the considerably younger, late Viséan (late Holkerian to Asbian [late Meramecian to early Chesterian]) genus Beyrichoceras Foord, 1903 (type species, Goniatites obtusus Phillips, 1836) (eg, Gordon, 1965, p. 284."

Visean
"The first appearance of Eoparastaffella simplex in the lineage Eoparastaffela ovalis - Eoparastaffella simplex (foraminifers) [is] the new biostratigraphic criterion to define the base of the Viséan."

Tournaisian
"The base of the Carboniferous System, Mississippian Sub-System and Tournaisian Stage is defined at the base of Bed 89 in Trench E' at La Serre, France. It coincides with the first appearance of the conodont Siphonodella sulcata within the evolutionary lineage from Siphonodella praesulcata to Siphonodella sulcata."

Devonian
The Devonian spanned 416.0 ± 2.8 to 359.2 ± 2.5 Mb2k.

Famennian
"The boundary for the Frasnian/Famennian Stage Global Stratotype Section and Point (GSSP) [...] is drawn [above] in a section exposed [in the second image above] near the Upper Coumiac Quarry in the southeastern Montagne Noire, France."

A specimen of Clymenia laevigata from the Upper Devonian Famennian of Poland is on the right.

On the left is a fossil of Platyclymenia intracrostata also from the Famennian of Poland.

Early Devonian
Asteroxylon ("star-shaped xylem") is an extinct genus of vascular plants of the Division Lycopodiophyta known from anatomically preserved specimens described from the famous Early Devonian Rhynie chert and Windyfield chert in Aberdeenshire, Scotland. Asteroxylon is considered the most basal member of the Lycopsida.

This plant consisted of aerial, isotomously and anisotomously branching stems that reached 12 mm in diameter and 40 cm in length. The possibly procumbent aerial stems arose from a leaf-less rhizome which bore smaller-diameter, positively geotropic root-like branches. The rhizomes, which represent an independent origin of roots, reached a depth of up to 20 cm below the surface. The xylem or conducting tissue at the center of the aerial stems is distinctly star-shaped in cross-section and has been considered an early actinostele or an "Asteroxylon-type" protostele. The tracheids are of the primitive annular or helical type (so-called G-type). "Leaves" – not true leaves, but protrusions – were of the form of unbranched strap-shaped enations up to 5 mm long; a single vascular trace branched from the main bundle in the centre of the stem to terminate at the base of each enation. Enations and axes bore stomata, indicating that their tissues were capable of photosynthesis.

Asteroxylon differs from other similar Early Devonian lycopsids such as Drepanophycus and Baragwanathia in that the singular vascular leaf trace in these latter plants extends into the leaf. The leaves of Drepanophycus and Baragwanathia are therefore considered to be true microphylls or, alternatively, small leaves.

The type species is Asteroxylon mackiei.

Mimagoniatites is a genus of ammonites from the early Devonian.

"Shell [is] small to large size, evolute, thinly discoidal to discoidal. Whorl cross section of the first two whorls [is] approximately circular, in later whorls subtrapezoidal. Umbilicus [is] narrow to moderately wide, moderately large umbilical window (< 1 mm). Whorl expansion rate increases remarkably from the second whorl on (> 2.5, later up to 3.9). Growth line course [is] biconvex with prominent ventrolateral projection and deep ventral sinus."

The lower boundary of the genus is "LD3C--LD3D: Anetoceras Range Zone top, 405.5 million years" and the upper boundary is "CZB maureri--sulc.antiqua Zone [19,30], 398.5 million years".

Geographic distribution: "Devonian of Algeria (2 collections), Canada (1: Nunavut), China (7), the Czech Republic (5), Germany (3), Morocco (13), the Russian Federation (1), Spain (4), Turkey (3), United States (1: Pennsylvania)".

Silurian
The Silurian spanned 443.7 ± 1.5 to 416.0 ± 2.8 Mb2k.

Hexamoceras hertzeri is an index fossil for the Silurian.

Hexamoceras is a genus of the Nautiloidea.

"Rolfe made the important observation that 'Other genera are pre-Devonian and hence cannot be ammonoid aptychi, but Ruedemann's suggestion that aptychi "would naturally also have existed in the Ordovician and Silurian cephalopods" has been largely overlooked'."

Miaogoalingian
Miaogoalingian Chinese Stage, from 422 to 418.7 ± 2.7 Ma. End Defined By: Graptolite, lowest occurrence of Monograptus parultimus.

Andean-Saharan glaciation
"A major glacial episode at c. 440 Ma, is recorded in Late Ordovician strata (predominantly Ashgillian) in West Africa (Tamadjert Formation of the Sahara), in Morocco (Tindouf Basin) and in west-central Saudi Arabia, all areas at polar latitudes at the time. From the Late Ordovician to the Early Silurian the centre of glaciation moved from northern Africa to southwestern South America."

The maximum extent of glaciation developed in Africa and eastern Brazil.

The Andean-Saharan was preceded by the Cryogenian ice ages (720–630 Ma, the Sturtian and Marinoan glaciations), often referred to as Snowball Earth, and followed by the Karoo Ice Age (350–260 Ma).

Telychian
On the right is an image of the type locality for the Telychian base GSSP indicated by an arrow which points parallel to the bedding. Older bedding of the Aeronian is to the right. The Telychian GSSP is in the Wormwood Formation, Cefn Cerig quarry.

In the section below for the Aeronian, the lower Telychian is marked with a Ⓣ.

Aeronian
The diagram above has the GSSP for the base of the Aeronian symbolized by a Ⓐ. The upper GSSP for the end of the Aeronian is symbolized by a Ⓣ.

On the right is the type locality for the base of the Aeronian indicated by the arrow. Actual beds are perpendicular to the arrow. The base of the Aeronian is in the Cefngarreg Sandstone Formation (formerly Trefawr Formation), Trefawr track section, Crychan Forest, Central Wales.

Ordovician
The Ordovician lasted from 488.3 ± 1.7 to 443.7 ± 1.5 Mb2k.

Upper Ordovician
The image on the right is an over-encrusted, internal mold of a nautiloid from the Upper Ordovician of northern Kentucky.

Actonian
The "Onny Valley [...] is the type locality for the Actonian and Onnian substages, and a [Site of Special Scientific Interest] SSSI."

On the right is a geological map of the Onny Valley section together with a strategraphic column, sample localities and the chrono- and lithostratigraphy of the southern Caradoc area (after Rushton et al. 2000).

Sandbian
"The Lower Sandbian Nemagraptus gracilis Zone comprises one of the most widespread, and easily recognizable graptolite faunas in the Ordovician System. The base of the N. gracilis Zone also marks the base of the Upper Ordovician Series, and is internationally defined by the FAD of the eponymous species, with the Global Stratotype Section and Point (GSSP) located at Fågelsång in Scania, southern Sweden (Bergström et al., 2000, 2009)."

Middle Ordovician
Epoch: Middle Ordovician (471.8 - 460.9 Ma).

Abereiddian
On the right is an Ordovician chart which illustrates the stratigraphic relationships between the Global Series, Stages and key faunal markers, and the main regional series, stage and substage divisions used in different parts of the world (after Webby 1988).

Here, the Abereiddian is the lower portion of the Llanvirn series, which in turn is the upper portion of Darriwilian Stage, of the upper Middle Ordovician.

Chewtonian
Chewtonian Australian Stage, from 473 To 471 Ma.

Early Ordovician
Epoch: Early Ordovician (488.3 - 471.8 Ma).

Ibexian
North American Stage: Ibexian (491 - 471.8 ± 1.6 Ma).

End Defined By: Conodont, potentially lowest occurrence of Protoprioniodus aranda or of Baltoniodus triangularis.

Tremadocian
ICS Stage: Tremadocian (488.3 - 478.6 Ma).

The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from 485.4 to 477.7 Ma. The base of the Tremadocian is defined as the first appearance of the conodont species Iapetognathus fluctivagus at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland.

The GSSP for the beginning of the Tremadocian is the Greenpoint section (49.6829°N 57.9653°W) in Gros Morne National Park, in western Newfoundland, defined as the first appearance of the conodont species Iapetognathus fluctivagus, found 101.8 m above the Greenpoint section datum within bed number 23. The boundary lies within the Broom Point Member, of the Green Point Formation which is part of the Cow Head Group. The first planktonic graptolites appear 4.8 m above the first appearance of Iapetognathus fluctivagus at Greenpoint section.

The Tremadocian ends with the beginning of the Floian which is defined as the first appearance of Tetragraptus approximatus at the GSSP in Diabasbrottet quarry, Västergötland, Sweden.

Datsonian
Australian Stage: Datsonian (488.3 - 485 Ma).

Upper Cambrian
~497 – 485.4 ± 1.9 Ma.

"Cambrian Radiolaria are best known from Middle Cambrian shallow-water carbonate environments (i.e., the Middle Cambrian strata; Won and Below, 1999), but they are also known Upper Cambrian in deep-sea deposits (Tolmacheva et al., 2001)."


 * Elvinia-zone Upper Cambrian.

New Elvinia Zone (Upper Cambrian) Trilobites.

Upper Middle Cambrian.

A "radiometrically anchored astrochronologic framework across the late Cambrian interval, using high-resolution aluminum (Al) series (1 mm resolution) through the Alum Shale Formation in Scania, southernmost Sweden, [is] based on the fully cored Albjära-1 well. Significant cycles with periods of 405 kyr (long eccentricity), 108 kyr (short eccentricity), 30.4 kyr (obliquity) and 18.8 kyr (precession), associated with long-term amplitude modulation of obliquity and precession, confirmed the orbital imprint on late Cambrian climate. Using the U-Pb dating at 486.78±0.53Ma for the Cambro-Ordovician boundary as anchor point, our timescale spans from ~483.9 to ~500.0 Ma, covering 7 trilobite superzones and 3 graptolite zones. The calibration indicates ages of 491.2±0.54 Ma, 493.9±0.67 Ma, 497.3±0.67 Ma and 500.4±0.67 Ma for the lower boundaries of provisional Stage10, Jiangshanian, Paibian and Guzhangian stages, respectively."

Furongian
~497 – 485.4 ± 1.9 Ma.

The Furongian Series includes Cambrian Stage 10, Cambrian Stage 9, and the Paibian Stage.

Hunanian
~497 – 485.4 ± 1.9 Ma.

The Hunan is comparable to the Furongian.

Cressagian
European Stage: Cressagian (488.3 - 486 Ma.)

Cambrian
The Cambrian lasted from 542.0 ± 1.0 to 488.3 ± 1.7 Mb2k.

Because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used: in some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian (Caerfai or Waucoban, 541 ± 1.0 to 509 ± 1.7 mya), Middle Cambrian (St Davids or Albertan, 509 ± 1.0 to 497 ± 1.7 mya) and Furongian (497 ± 1.0 to 485.4 ± 1.7 mya; also known as Late Cambrian, Merioneth or Croixan).

Trilobite zones

Trilobite zones allowing biostratigraphic correlation in the Cambrian belong to the Lower, Middle, or Upper Cambrian.

Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones.

Late Cambrian
The Franconian is the middle stage of the Upper or Late Cambrian in North America, equivalent to the Chinese Changshanian with a span of nearly 4.5 million years, from about 497 to 492.5 Ma. The name comes from the Franconia Formation,  about 100 feet (30 m) of sandstone and green shale exposed near the town of Franconia in eastern Minnesota, north of St Paul.

The Franconian is preceded by the Dresbachian and followed by the Trempealeauan, respectively the lower and upper stages of the North American Upper Cambrian or Croixan Series.

Collier Shale
The Collier Shale, a geologic formation in the Ouachita Mountains of Arkansas and Oklahoma, dating from the Late Cambrian to Early Ordovician periods, the oldest stratigraphic unit exposed in Arkansas, first described in 1892, named in 1909, with assigned type locality to the headwaters of Collier Creek in Montgomery County, Arkansas, underlies the Crystal Mountain Sandstone.

Trilobites:
 * Anechocephalus aphelodermus
 * Apachia lumaleasa
 * Buttsia drabensis
 * Cernuolimbus monilis
 * Cheilocephalus brachyops
 * Cliffia lataegenae
 * Cliffia magnacilis
 * Comanchia amplooculata
 * Dellea planafrons
 * Dellea suada
 * Erixanium lacunatum
 * Housia vacuna
 * Iddingsia hapsis
 * Irvingella major
 * Jessievillia radiatus
 * Kindbladia wichitaensis
 * Kymagnostus harti
 * Linnarsonella girtyi
 * Neoagnostus dilatus
 * Parabolinoides contractus
 * Pseudagnostus communis
 * Pseudokingstonia exotica
 * Pterocephalia sanctisabae
 * Pulchricapitus fetosus
 * Pyttstrigis dicilia
 * Xenocheilos minutum

Payntonian
Australian Stage: Payntonian (491 - 488.3 Ma).

Stage 10
Stage 10 of the Cambrian is the still unnamed third and final stage of the Furongian series that follows the Jiangshanian and precedes the Ordovician Tremadocian Stage.

The upper boundary is defined as the appearance of the conodont Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 Ma.

The calibration indicates an age of 491.2±0.54 Ma for the lower boundary of provisional Stage10.

Batyrbayan
Russian-Kazakhian Stage: Batyrbayan (491.5 - 488.3 Ma)

The Batyrbayan is the lowest level of the Upper Cambrian.

Biostratigraphic zones:
 * 1) Lotagnostus hedini
 * 2) Harpidoides–Platypeltoides
 * 3) Lophosaukia

Dolgellian
The Dolgellian is the latest level of the Cambrian, from 492.5 To 488.3 ± 1.7 Ma.

Fengshanian
The Fengshanian is the latest level of the Cambrian, from 492.5 To 488.3 ± 1.7 Ma.

Trempealeauan
~ 492.5 to 488.3 Ma.

The Trempealeauan is the upper or latest stage of the Upper or Late Cambrian in North America, spanning about 4 million years from about 492.5 to 488.3 Ma, equivalent to the Fengshanian of China. The name comes from the Trempealeau Formation, named for the town of Trempealeau in western Wisconsin, located on the Mississippi River.

The Trempealeauan follows, or overlies, the Franconian, which is the middle stage of the Upper Cambrian in North America and is followed by the Gasconadian in the Lower Ordovician. Together with the Dresbachian at the bottom, the Trempealeauan and Franconian make up the Croixan Series.

Croixan
501 ± 2 to 488.3 ± 1.7 Ma.

End Defined By: Conodont, lowest occurrence of Iapetognathus fluctivagus; just above base of Cordylodus lindstromi conodont Zone. Just below lowest occurrence of planktonic graptolites.

The lower and upper stages of the North American Upper Cambrian is the Croixan Series.

Late Cambrian Epoch (Upper Cambrian, Merioneth, Furongian, Croixian, Potsdamian), from 501 ± 2 to 488.3 ± 1.7 Ma.

Start Defined By: Trilobite, lowest occurrence of agnostoid Glyptagnostus reticulatus. Coincides with base of large positive carbon-isotope excursion.

Merioneth
501 ± 2 to 488.3 ± 1.7 Ma.


 * Genevievella campbellina occurs in the Upper Cambrian of the United States (Merioneth: Warriorsmark, Huntingdon, Huntingdon; Warrior Formation, near Waddle, Centre County, all Pennsylvania, 40.8° N, 77.9° W)
 * Trilobites, including Crepicephalus, Cedaria, and Llanoaspidella
 * Brachiopods
 * Cryptozoon, a type of trace fossil
 * Stromatolites

Potsdamian
501 ± 2 to 488.3 ± 1.7 Ma.

Jiangshanian
~494 – ~489.5 Ma.

The upper boundary candidate is the FAD of the Trilobite Lotagnostus americanus.

The Jiangshanian is the middle stage of the Furongian series following the Paibian Stage and is succeeded by the Cambrian Stage 10, with the base defined as the first appearance of the trilobite Agnostotes orientalis which is estimated to be the 494 million years ago, lasting until approximately 489.5 Ma.

The Global Standard Stratotype-Section and Point (GSSP) for the Base of the Jiangshanian Stage was established in 2011.

Sunwaptan
Sunwaptan North American Stage, from 493 to 491 Ma.

Upper Millardan

Millardan
494.5 to 491 Ma.

The Millardan contains the Sunwaptan and Steptoean.

Aksayan
Russian-Kazakhian Stage: Aksayan (493 - 491.5 Ma).

Biostratigraphic zones:
 * 1) Trisulcagnostus trisulcus
 * 2) Lotagnostus scrobicularis
 * 3) Neoagnostus quadratiformis
 * 4) Eurudagnostus ovaliformis
 * 5) Eurudagnostus kazachstanus
 * 6) Pseudagnostus pseudangustilobis

Plicatolina lucida from the Aksayan Stage, Ogon’or Formation, upper part.

"Cambrian deposits appear on the surface in wings of anticline folds (Chekurovka and Bulkur Anticlines). The Upper Cambrian is represented by most of the upper part of the Ogon’or Formation. In the north of the region, in the Bulkur Anticline, the upper Ogon’or Formation is replaced by dolomites of the Balaganakh Formation (Kembrii Sibiri (Cambrian of Siberia), Repina, L.N. and Rozanov, A.Yu., Eds., Tr. Inst. Geol. Geofiz., Ross. Akad. Nauk, Sib. Otd., no. 788, Novosibirsk: Nauka, 1992). All records of the genus Plicatolina are confined to the upper part of the Ogon’or Forma􏰀tion."

Changshanian
Changshanian (496.8 - 492.5) span 4.3 Ma.

The middle stage of the Late Cambrian in China with a span of nearly 4.5 million years, from about 497 to 492.5 Ma.

Festiniogian
Festiniogian Regional Stage (Franconian, Changshanian), from 496.8 To 492.5 Ma.

Franconian
The Franconian is the middle stage of the Upper or Late Cambrian in North America, equivalent to the Chinese Changshanian with a span of nearly 4.5 million years, from about 497 to 492.5 Ma.

Steptoean
Steptoan North American Stage, from 494.5 to 493 Ma.

Lower Millardan

The Steptoean Positive Carbon Isotope Excursion (SPICE) was a geological event which occurred ~ 500 Ma. The SPICE event was a positive shift in carbon isotope (Δ) values which lasted for around 2 to 4 million years. This shift is interpreted to be a global disturbance in the carbon cycle, affecting both the ocean and atmosphere. Regional sea level changes and trilobite extinctions are associated with the SPICE event, although the exact mechanism(s) driving these events is still unconfirmed.

One proposed cause of the SPICE is an increase in the burial of organic carbon, perhaps caused by increased primary productivity or enhanced organic matter preservation due to ocean stratification (i.e. anoxia or euxinia).

"The Cambrian Paibian sedimentary succession of the central Australian Amadeus Basin contains a sequence of supratidal to subtidal shallow marine siliciclastic and oolitic, stromatolitic limestones and dolostones. Basin-wide sequence stratigraphy in combination with biostratigraphy revealed the [Glyptagnostus] G. stolidotus Zone within a 3rd-order transgressive systems tract (TST). The westward transgression caused changes from a fluvial-dominated depositional environment towards a shallow-marine oolitic carbonate shoal environment. The eastern succession is dominated by stromatolitic, oolitic carbonate rocks with 2- to 5-m 5th-order shoaling upward cycles with several 4th-order cycles. The change from TST to HST (highstand systems tract) is marked by a maximum flooding surface within the Goyder Formation, which coincides with the peak of the Steptoean Positive Carbon Isotope Excursion (SPICE). The SPICE shows a facies-independent, synchronous positive δ excursion of 5‰ in a 130 m interval in 8 sections across a ~460 km transect. The SPICE peak is lowest in the nearshore successions (+0.4‰ δ), and highest in the platform succession (+4.9‰ δ) and is interpreted to be related to the chemical gradient of seawater and mixing of the [dissolved inorganic carbon] DIC with atmospheric -derived (i.e. terrestrial) bicarbonate. The recovery from SPICE is recorded by 4th-order shoaling upward cycles that compose the 3rd-order HST."

Sakian
Russia, Kazakhstan age Sakian (494.5 - 493) Ma.

Biostratigraphical zones:
 * 1) Ivshinagostus ivshini
 * 2) Oncagnostus longiformis
 * 3) Glyptagnostus reticulatus

Idamean
Australian Stage: Idamean (497 - 494 Ma).

Ayusokkanian
Russian-Kazakhian Stage: Ayusokkanian (501 - 494.5 Ma).

The FAD of Lotagnosthus americanus is the primary stratigraphic tool for correlation of the base for Stage 10.

Biostratigraphic zones:
 * 1) Glyptagnostus stolidotus
 * 2) Kormagnostus simplex

Paibian
ICS Stage: Paibian (501 - 496 Ma).

The "FAD of Glyptagnostus reticulatus [is the primary stratigraphic tool for correlation of the base] for the Paibian Stage."

Maentwrogian
Regional Stage: Maentwrogian (501 - 496.8 Ma).

Dresbachian
The Dresbachian is a Maentwrogian regional stage of North America, lasting from 501 to 497 Ma, part of the Upper Cambrian and is defined by four trilobite zones (Cedaria, Crepicephalus, Aphelaspis, and Dunderbergia), overlaps with the International Commission on Stratigraphy (ICS)-stages Guzhangian, Paibian and the lowest Jiangshanian.

The Dresbachian overlies the Middle Cambrian Albertan series, and is the lowest stage of the Upper Cambrian Croixian series, followed by the Franconian stage. The Dresbachian extinction event, about 502 million years ago, was followed by the Cambrian–Ordovician extinction event about 485.4 Ma.


 * Cedaria is a small, rather flat trilobite with an oval outline, a headshield and tailshield of approximately the same size, 7 articulating segments in the middle part of the body and spines at the back edges of the headshield that reach halflength of the body, that lived during the early part of the Upper Cambrian (Dresbachian), and is especially abundant in the Weeks Formation.
 * Genevievella simon, Genevievella cuniculaena, Genevievella raggedi and Genevievella campbellina have been found in the Upper Cambrian of Canada (Dresbachian, Rabbitkettle Formation, Yukon, 62.7° N, 128.4° W).
 * Genevievella spinox has been excavated from the Upper Cambrian of the United States (Dresbachian, Coosella zone, Riley Formation, Central Texas, 30.3° N, 97.7° W)
 * Genevievella granulosa, Weeks Formation, House Range, Millard County, Utah, USA, early Upper Cambrian.

Mindyallan
Upper Cambrian of Australia: 501 - 497 Ma.


 * Genevievella caelata is known from the Upper Cambrian of Australia (Mindyallan, Upper beds Member, Mungerbar Formation, Glenormiston, Queensland, 22.9° S, 138.8° E).

Marjuman
North American Stage: Marjuman (504 - 494.5 Ma).

Cedaria-zone lowermost Upper Cambrian

Bathyuriscus is an extinct genus of Cambrian trilobite, a nektobenthic predatory carnivore, endemic to the shallow seas that surrounded Laurentia. Its major characteristics are a large forward-reaching glabella, pointed pleurae or pleurae with very short spines, and a medium pygidium with well-impressed furrows. Complete specimens have never reached the size of 7 cm predicted by the largest pygidium found. Bathyuriscus is often found with the free cheeks shed, indicating a ecdysis (moulted exoskeleton). An average specimen will in addition have a furrowed glabella, crescent-shaped eyes, be semi-circular in overall body shape, have 7 to 9 thoracic segments, and a length of about 1.5 inches.

Guzhangian
~500.5 – ~497 Ma

The Guzhangian-Paibian boundary is marked by the first appearance of the trilobite Glyptagnostus reticulatus around 497 Ma.

"The Global boundary Stratotype Section and Point (GSSP) for the base of the Guzhangian Stage (Cambrian Series 3) is defined at the base of a limestone (calcisiltite) layer 121.3 m above the base of the Huaqiao Formation in the Louyixi section along the Youshui River (Fengtan Reservoir), about 4 km northwest of Luoyixi (4 km southeast of Wangcun), in northwestern Hunan, China."

"The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Lejopyge laevigata [in the image on the left] (base of the L. laevigata Zone)."

Trilobites:
 * Glyptagnostus reticulatus zone around 497 Ma.
 * Glyptagnostus stolidotus zone.
 * Lejopyge laevigata zone.
 * Genevievella bigranulosa is present in the Upper Cambrian of China (Guzhangian, Glyptagnostus stolidotus trilobite zone and Paibian, Glyptagnostus reticulatus trilobite zone, both Huaqiao Formation, Hunan, 28.4° N, 109.5° E).

Miaolingian
~509 – ~497 Ma.

Upper GSSP acceptance date is 2003.

The Miaolingian lasted from about 509 to 497 Ma and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian.

The most promising fossil markers were seen to be the respective first appearances of either trilobite species Ovatoryctocara granulata or Oryctocephalus indicus, which both have an age close to 509 Ma. After some deliberation, the FAD of Oryctocephalus indicus was chosen to be the lower boundary marker, and the GSSP was placed in Wuliu-Zengjiayan, Guizhou, China.

Miaolingian acceptance date is 2018.

Albertan
Albertan, 509 ± 1.0 to 497 ± 1.7 Ma.

In the local North American subdivision, a paleontologist finding fragments of the trilobite Olenellus would identify the beds as being from the Waucoban Stage whereas fragments of a later trilobite such as Elrathia would identify the stage as Albertan.

In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian (Caerfai or Waucoban, 541 ± 1.0 to 509 ± 1.7 mya), Middle Cambrian (St Davids or Albertan, 509 ± 1.0 to 497 ± 1.7 mya) and Furongian (497 ± 1.0 to 485.4 ± 1.7 mya; also known as Late Cambrian, Merioneth or Croixan).

Spence Shale
(~507.5-506 Ma)

The Spence Shale, Wuliuan, ~507.5-506 Ma, the middle member of the Langston Formation in southeastern Idaho and northeastern Utah, exposed in the Bear River Range, the Wasatch Range and the Wellsville Mountains, is known for its abundant Cambrian trilobites and the preservation of Burgess Shale-type fossils, type locality: Spence Gulch in southeastern Idaho, near the town of Liberty, first described in 1908, spans the Albertella and Glossopleura biozones.


 * Glossopleura-zone
 * Albertella-zone

Sonoraspis and Albertella

Wheeler Shale
(~507 Ma)

Asaphiscus wheeleri occurs in the Middle Cambrian of the United States (Delamaran, Lower Wheeler Shale, Millard County, Utah, 40.0°N, 113.0°W; and Menevian, Wheeler Formation, House Range, Utah, 39.2° N, 113.3° W).

Burgess Shale
Def. a "rock formation in the Canadian Rockies that contains very many fossils from the Cambrian period" is called the Burgess Shale.

The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At 508 Ma (Wuliuan of the middle Cambrian), it is one of the earliest fossil beds containing soft-part imprints.

(~508 Ma)

Bathyuriscus–Elrathina-zone Middle Cambrian

Contemporaneous with the Burgess Shale

Oryctocephalus indicus-zone underlies Burgess Shale.

Eldon Formation
The Eldon Formation (51°18'8.5°N 115°55'45"W) ~509-500 Ma present on the western edge of the Western Canada Sedimentary Basin in the southern Canadian Rockies of southwestern Alberta and southeastern British Columbia, is a thick sequence of massive, cliff-forming limestones and dolomites, deposited during Middle Cambrian time, and it includes fossil stromatolites. The Eldon forms the scenic cliffs at the top of Castle Mountain, and can also be seen at Mount Yamnuska and other mountains in Banff National Park and Yoho National Parks.

The Eldon Formation was deposited during the Middle Cambrian, originally formed as limestone and calcareous mudstone in the intertidal to supratidal zone along the western margin of the Laurentia (North American Craton), subsequently by dolomitization altered to dolomite and dolomitic mudstone in some areas.

The Eldon Formation reaches a maximum thickness of about 500 metres (1,640 feet) at Mount Bosworth on the Alberta-British Columbia border conformably overlies the Stephen Formation, which hosts the fossils of the Burgess shale, in the south, and the Snake Indian Formation in the north, is conformably overlain by the Pika Formation, grades into the Earlie Formation to the east, the Chancellor Formation to the west, and the Titkana Formation to the north. It is probably equivalent to the Windsor Mountain Formation to the south.

Drumian
~504.5 – ~500.5 Ma

The "FAD of Ptychagnostus atavus [is the primary stratigraphic tool for correlation of the base (GSSP)] for the Drumian Stage".

"The Global boundary Stratotype Section and Point (GSSP) for the base of the Drumian Stage (Cambrian Series 3) is defined at the base of a limestone (calcisiltite) layer 62 m above the base of the Wheeler Formation in the Stratotype Ridge section, Drum Mountains, Utah, USA. The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Ptychagnostus atavus (base of the P. atavus Zone)."

Middle Cambrian
The Middle Cambrian corresponds to the Miaolingian.

Epoch: Middle Cambrian (513 - 501 Ma).

Ptychagnostus is a member of the Agnostida that lived during the Cambrian, did not exceed one centimetre in length. Their remains are rarely found in empty tubes of the polychaete worm Selkirkia. The genus probably ranged throughout the water column, had two glabellar lobes, and three pygidial lobes.

Ptychagnostus punctuosus-zone


 * Ptychagnostus punctuosus (Type species).
 * Ptychagnostus affinis (formerly Pt. punctuosus affinis)
 * Ptychagnostus aculeatus
 * Ptychagnostus akanthodes
 * Ptychagnostus atavus
 * Ptychagnostus cassis
 * Ptychagnostus ciceroides
 * Ptychagnostus cuyanus
 * Ptychagnostus germanus
 * Ptychagnostus gibbus
 * Ptychagnostus hybridus
 * Ptychagnostus intermedius
 * Ptychagnostus michaeli
 * Ptychagnostus praecurrens
 * Ptychagnostus seminula

Mayan
Russian-Kazakhian Stage: Mayan (502 - 501 Ma).

Trilobites:
 * 1) Peronopsis earliest Mayan (~497.5 Ma) to earliest Batyrbayan (~497.0 Ma)
 * 2) Peronopsis bonnerensis = Pentagnostus (Meragostus) bonnerensis - zone
 * 3) Lejopyge laevigata–Aldanaspis truncata
 * 4) Anomocarioides limbataeformis
 * 5) Corynexochus perforatus– Anopolenus henrici

Boomerangian
Australian Stage: Boomerangian (504 - 501 Ma).

The Boomerangian is the upper level of the Middle Cambrian in Australia.

Zhungxian
Chinese Stage: Zhungxian (505 - 501 Ma).

Undillian
Australian age: Undillian (506 - 504 Ma).

Gushanian
Chinese Stage: Zhungxian (596.8 - 501 Ma).

St. David's
European epoch (513 ± 2 - 501 ± 2) Ma.

Amgan
Amgan Russian-Kazakhian Stage (Solvan), from 513 ± 2 to 502 Ma.

"The Lower Cambrian carbonate sequence ends with the 160-m-thick Upper Toyonian Barangol Formation, the age which is based on calcareous algae, archaeocyatids and trilobites (Zybin et al., 2000). It is uncorformably overlain by the Ust’-Sema Formation, a 1,000-m-thick basaltic sequence displaying thick conglomerates at its base, containing blocks of limestones with a similar fauna to the one identified in the Cheposh Formation (Zybin et al., 2000)."

Biostratigraphic zones:
 * 1) Pseudanomocarina
 * 2) Kounamkites
 * 3) Schistocephalus

Zuzhungian
Chinese age: Zuzhungian (509 - 503 Ma).

Delamaran
North American Stage: Delamaran (512 - 504 Ma).

The Delamaran is the North American equivalent of the Amgan of Russia.

Wuliuan
~509 – ~504.5 Ma

Bolaspidella-zone

Starts at the base of the Drumian stage.

"The polymerid trilobites Ptychoparella (incorporating Elrathina as a junior synonym) and Elrathia have long stratigraphic ranges (Robison, 1964a, 1964b, 1976; Babcock, 1994a) that extend from stage 5 into the lower part of the Drumian Stage (White, 1973) and provide little help in constraining the base of the Drumian."

On the right are images of key agnostoid trilobite species used for recognition of the base of the Drumian Stage.

"A, Ptychagnostus gibbus (Linnarsson), dorsal exoskeleton in shale, x 8.4, from the Wheeler Formation, c. 25 m above base, south side of Swasey Peak, House Range, Utah (R. A. Robison locality 157); KUMIP 153949. B, Ptychagnostus atavus (Tullberg), cephalon in limestone showing scrobiculate genae, x 8.1, from the Wheeler Formation, 27 m above base, House Range, Utah (R. A. Robison locality 196); KUMIP 153830. C, P. atavus (Tullberg), pygidium in limestone, x 7.8, from same locality as specimen in Figure 6B; KUMIP 153933. D, P. atavus (Tullberg), dorsal exoskeleton from shale with cone-in-cone calcite encrusting ventral surface, x 8.1 from the Wheeler Formation, c. 100 below top, “Swasey Spring quarry”, east flank of House Range, Utah (R. A. Robison locality 114); KUMIP 153930."

The "Cambrian lobopodian (panarthropod) worm Hallucigenia sparsa [is] from the Burgess Shale (Cambrian Series 3, Stage 5)."

Florian
Australian Stage: Florian (508 - 506 Ma).

Templetonian
Templetonian Australian Stage, from 510 to 508 Ma.

Bright Angel Shale


The three units of the Tonto Group and the colorful Bright Angel Shale are easily identified as a geological sequence beneath the tall cliffs of the Redwall Limestone (the Redwall sits upon a short resistant cliff of Muav Limestone); the Tonto Group is also easily seen beside Granite Gorge of the Colorado River and the Vishnu Basement Rocks The units of the Tonto Group:
 * Redwall Limestone
 * Temple Butte Formation, Devonian – (409–363 Ma), channel deposits upon Muav Limestone
 * Tonto Group (3 units) (~544–505 Ma)
 * (3) Muav Limestone
 * (2) Bright Angel Shale
 * (1) Tapeats Sandstone

The eastern version of the Pioche shale can be found eastwards in the Grand Canyon, as the Bright Angel Shale.

The Cambrian Bright Angel Shale is the middle layer of the three member Tonto Group geologic feature. The 3-rock Tonto section famously sits upon the Great Unconformity because of the highly resistant cliffs of the base layer, vertical Tapeats Sandstone cliffs.

The Bright Angel Shale is easily identified for two reasons: its soft-greenish color stands out against the browns, reds, and whites of neighboring rock units, and its slope-forming character against mostly cliff-forming resistant rocks.

The Bright Angel Shale is about 500 ft thick at its maximum. It is a nonresistant slope-forming unit. The Bright Angel Shale consists of green and purple-red, siltstone and shale which is interbedded with red-brown to brown sandstone that is similar in lithology to the underlying Tapeats. The Bright Angel Shale underlies and interfingers with Muav Limestone. The Bright Angel Shale is located in the lower elevations of the Grand Canyon, Arizona. The Bright Angel Shale preserves fossils dating back to the Cambrian.

Pioche Shale
The Pioche Shale is an Early to Middle Cambrian Burgess shale-type Lagerstätte in Nevada.

It spans the Early–Middle Cambrian boundary; fossils from the Early Cambrian are preserved in botryoidal hematite, whereas those from the Middle Cambrian are preserved in the more familiar carbon films, and very reminiscent of the Chengjiang County preservation.

It preserves arthropods and worms familiar from the Burgess Shale.

It spans the early Cambrian Olenellus and basal Middle Cambrian Eokochaspis nodosa trilobite zones.

Eokochaspis zone

Lower-Middle Cambrian Boundary Interval.

The lower Middle Cambrian

Lower Cambrian
541.0 ± 1.0 – ~509 Ma.

"The Lower Cambrian carbonate sequence ends with the 160-m-thick Upper Toyonian Barangol Formation, the age which is based on calcareous algae, archaeocyatids and trilobites (Zybin et al., 2000)."

The Lower Cambrian consists of the Cambrian Series 2 and the Terreneuvian.

In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into an epicontinental sea.

Early Cambrian
In some subdivisions the Cambrian is divided into three epochs with locally differing names; e.g. the Early Cambrian (Caerfai or Waucoban, 541 ± 1.0 to 509 ± 1.7 mya).

Early Cambrian Epoch (Lower Cambrian, Caerfai, Waucoban, Georgian), from 542 ± 0.3 to 513 ± 2 Ma. Start Defined By: Trace fossil, lowest occurrence of Treptichnus (Phycodes) pedum. Near base of negative carbon-isotope excursion.

Maozhangian
China stage Maozhangian (513 - 509).

Stage 4
~514 – ~509 Ma.

The lower boundary may be the first appearance datum of two trilobite genera, Olenellus or Redlichia or the first appearance of the trilobite species Arthricocephalus chauveaui, which set the lower boundary close to 514 Ma. The upper boundary corresponds to the beginning of the Wuliuan.

Olenellus zone (top of the Lower Cambrian)

The Olenellus-zone has traditionally marked the top of the Lower Cambrian.

Subdivision of the Olenellus-zone

Recently, it has been proposed to subdivide the Olenellus-zone.

The following zones have been proposed to replace the Upper Olenellus-zone. Each lower boundary is defined by the first occurrence of the naming species. Each upper boundary is defined by the first occurrence of the naming species of the overlying zone. In case of the youngest zone, this is Eokochaspis nodosa, that also marks the base of the Wuliuan. Species: Nephrolenellus multinodus (lower half), Mesonacis fremonti, Olenellus terminatus Sensu and its common qualifiers (s.l.), Olenellus puertoblancoensis s.l., Olenellus fowleri s.l., Olenellus gilberti, Bolbolenellus brevispinus (not the lower part), Olenellus chiefensis (upper half), Olenellus sp.1 (upper half), Nephrolenellus geniculatus (upper part), Olenellus sp.2 (upper part), Olenellus howelli (very uppermost part).
 * Nephrolenellus multinodus-zone (youngest).

Species: Bolbolenellus euryparia (lower half), Mesonacis fremonti, Bristolia fragilis s.l. (lower half), Olenellus terminatus s.l., Olenellus fowleri s.l., Olenellus puertoblancoensis s.l., Olenellus gilberti (uppermost part), Biceratops nevadensis (uppermost part), Bristolia brachyomma (very uppermost part). Species: Peachella iddingsi (lower half), Mesonacis fremonti, Olenellus nevadensis (lower part), Bristolia anteros (lowest half), Bristolia fragilis s.l., Olenellus terminatus s.l., Paranephrolenellus besti (very short period in the late lower part), Peachella brevispina (middle part). Species: Bristolia insolens (lower half), Mesonacis fremonti, Olenellus nevadensis, Olenellus clarki, Olenellus sp.3, Paranephrolenellus klondykensis (lowest part), Bristolia harringtoni (middle part), Bristolia bristolensis (lower half), Bristolia anteros (not lowest part), Bristolia fragilis s.l. (upper half), Paranephrolenellus inflatus (very short interval in the middle), Eopeachella angustispina (uppermost part). Species: Bristolia mohavensis (lower half), Mesonacis fremonti, Olenellus nevadensis, Olenellus clarki, Olenellus sp.3, Bristolia harringtoni (middle part), Bristolia bristolensis (upper half). Species: Arcuolenellus arcuatus (lowest part), ''Arcuolenellus aff. megafrontatis'' (lower half), Mesonacis cylindricus (not the highest part), Olenellus nevadensis, Olenellus clarki (not lowest part), Mesonacis fremonti (upper half), Olenellus sp.3 (upper part).
 * Bolbolenellus euryparia-zone.
 * Peachella iddingsi-zone
 * Bristolia insolens-zone
 * Bristolia mohavensis-zone
 * Arcuolenellus arcuatus-zone (oldest)

Cambrian Series 2
~521 – ~509 Ma.

Cambrian Series 2 corresponds to the Toyonian down to the Atdabanian and to Cambrian Stage 4 and Stage 3.

Ordian
Australian Stage: Ordian (520 - 510 Ma).

Dyeran
North American Stage: Dyeran (524.5 - 512 Ma).

"The upper Dyeran Latham Shale—Chambless Limestone—Cadiz Formation succession of the Marble Mountains and Providence Mountains [...] is considered cratonic because it is separated from the erosional contact with Precambrian basement by only a relatively thin quartzite and siltstone interval (Stewart, 1970; Palmer, 1971; Nelson, 1976)."

"Six new biostratigraphic zones are established within the upper part of the Dyeran Stage: the Arcuolenellus arcuatus (oldest), Bristolia mohavensis, Bristolia insolens, Peachella iddingsi, Bolbolenellus euryparia, and Nephrolenellus multinodus (youngest) zones. The base of each zone is defined by the first appearance datum of the eponymous species. Sequence stratigraphic analysis reveals the presence of four depositional sequences within the upper Dyeran of the southern Great Basin. Sequence boundaries are often marked by erosion surfaces within successions deposited on the craton and the inner and middle shelf, but do not show strong association with observed range ends of olenelloid species and do not correspond to zonal boundaries within the upper Dyeran. Sequence I spans the A. arcuatus Zone to the lowermost Bo. euryparia Zone; Sequence II is contained entirely within the ''Bo. euryparia Zone; Sequence III spans the upper part of the Bo. euryparia Zone and lower part of the N. multinodus Zone; and Sequence IV corresponds to the upper part of the N. multinodus'' Zone."
 * 1) Nephrolenellus multinodus
 * 2) Bolbolenellus euryparia
 * 3) Peachella iddingsi
 * 4) Bristolia insolens
 * 5) Bristolia mohavensis
 * 6) Arcuolenellus arcuatus

The Dyeran overlies the Montezuman in North America.

Latham Shale
Bristolia trilobite zone, Latham Shale Formation, Dyeran (516.0 - 513.0 Ma).

Trilobites found throughout the Latham Shale are from the Bristolia subzone of the Bonnia-Olenellus Zone, indicating that the Latham Shale belongs to the upper Dyeran Stage of the Waucoban Series.

Longwangmioan
China Stage, from 518 to 513 Ma.

Toyonian
Toyonian Russian-Kazakhian Stage, from 518.5 to 513 ± 2 Ma.

"Trilobite associations found in [the Shashkunar] Formation belong to the Lower Toyonian Parapoliella–Onchocefalina zone. Archaeocyathids and brachiopods found in this formation suggest a wider, but compatible, Botomian to Toyonian age (Zybin et al., 2000). The Lower Cambrian carbonate sequence ends with the 160-m-thick Upper Toyonian Barangol Formation, the age which is based on calcareous algae, archaeocyatids and trilobites (Zybin et al., 2000). It is uncorformably overlain by the Ust’-Sema Formation, a 1,000-m-thick basaltic sequence displaying thick conglomerates at its base, containing blocks of limestones with a similar fauna to the one identified in the Cheposh Formation (Zybin et al., 2000)."

"The up to 700-m-thick Cheposh Formation, composed of massive limestones made of archaeocyathid biohermes, overlies conformably the Shashkunar Formation. Trilobite associations found in this Formation belong to the Lower Toyonian Parapoliella–Onchocefalina zone. Archaeocyathids and brachiopods found in this formation suggest a wider, but compatible, Botomian to Toyonian age (Zybin et al., 2000). The Lower Cambrian carbonate sequence ends with the 160-m-thick Upper Toyonian Barangol Formation, the age which is based on calcareous algae, archaeocyatids and trilobites (Zybin et al., 2000). It is uncorformably overlain by the Ust’-Sema Formation, a 1,000-m-thick basaltic sequence displaying thick conglomerates at its base, containing blocks of limestones with a similar fauna to the one identified in the Cheposh Formation (Zybin et al., 2000)."

Biostratigraphic zones:
 * 1) Anabaraspis splendens
 * 2) Lermontovia grandis
 * 3) Bergeroniellus ketemensis

Lenian
Regional Stage: Lenian (524 - 513 Ma).

Waucoban
Early Cambrian Epoch (Lower Cambrian, Caerfai, Waucoban, Georgian), from 542 ± 0.3 To 513 ± 2 Ma. Start Defined By: Trace fossil, lowest occurrence of Treptichnus (Phycodes) pedum. Near base of negative carbon-isotope excursion.

In North America, the Lower Cambrian is called the Waucoban series that is then subdivided into zones based on the succession of trilobites.

In East Asia and Siberia, the same unit is split into Alexian, Atdabanian, and Botomian stages.

Caerfai
Early Cambrian Epoch (Lower Cambrian, Caerfai, Waucoban, Georgian), from 542 ± 0.3 to 513 ± 2 Ma. Start Defined By: Trace fossil, lowest occurrence of Treptichnus (Phycodes) pedum. Near base of negative carbon-isotope excursion.

Stage 3
~521 – ~514 Ma.

The FAD of trilobites is the primary stratigraphic tool for correlation of the base for Stage 3.

Changlangpuan
Changlangpuan Chinese Stage, from 523 to 518 Ma.

The Changlangpuan in China is comparable to the Botomian in Russia or Kazakhian.

Botomian
Botomian Russian-Kazakhian Stage, from 524 to 518.5 Ma.

The end-Botomian mass extinction event, also known as the late early Cambrian extinctions, refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period, approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera up to 80%. Among the organisms affected by this event were the small shelly fossils, Archaeocyatha (archaeocyathids) (an extinct group of sponges), trilobites, brachiopods, Hyolitha (hyoliths), and Mollusca (mollusks).

"The Botomian age is based essentially on trilobites (Parapagetia–Serrodiscus zone), but also on archaeocyathids".

"Relatively well-preserved polycystine Radiolaria are [...] described from Lower Cambrian (Botomian) strata of the Shashkunar Formation, Altai Mountains in southern Siberia (Russia)."

"The Shashkunar Formation, a 500 m thick Lower Cambrian sequence of essentially carbonate rocks, overlies unconformably the Manzherok Formation and displays at its base a thick sequence of conglomerates. It is composed essentially of thin-bedded grey to dark grey limestones with interbedded nodular chert levels which become more frequent towards the top of the Formation."

"These radiolarians display a test formed of a disorderly and three-dimensionally interwoven meshwork of numerous straight and curved bars branching from a five-rayed point-centered spicule located within the inner shell surface. The shell structure allows their assignment to the family Archeoentactiniidae, thus extending the known age range of the family down to the Lower Cambrian."

The "material obtained from Altai attests that the earliest representatives of the family Archeoentactiniidae originated during or before the Botomian."

"[M]icrofossil material from nodular cherts of Botomian slope carbonates of the Shashkunar Formation can be assigned to the Archeoentactiniid family."

Biostratigraphic zones:
 * 1) Bergeroniaspis ornata
 * 2) Bergeroniellus asiaticusi
 * 3) Bergeroniellus ketemensis
 * 4) Bergeroniellus gurari
 * 5) Bergeroniellus micmacciformis–Erbiella

Heatherdale Shale
Heatherdale Shale is in the upper Normanville Group, mid-Botomian Stage, upper Lower Cambrian.

One soft-bodied fossil has been discovered from this site - a poorly-preserved Isoxys valve was cracked out in the lab. Isoxys is a nonmineralizing bivalved arthropod known only from Lower and Middle Cambrian rocks.

"Only two of several tuffaceous horizons from the Stansbury and Arrowie Basins have been dated (i) a date of 522.0 ± 2.1 Ma from the Heatherdale Shale of the Stansbury Basin, about 400 m above latest Atdabanian archaeocyathids and (ii) a date of 522.0 ± 1.8 Ma from the lower part of the Billy Creek Formation in the Arrowie Basin. Neither date is regarded as reliable."

"In the Stansbury Basin, Cooper et al. (1992) produced a mean 206 Pb/238 U Sensitive High Mass Resolution Ion Microprobe (SHRIMP) age of 526 ± 4 Ma with standard SL13 on zircons separated from a tuff bed within the upper part of the Heatherdale Shale at Sellicks Hill, Fleurieu Peninsula. Further analysis, plus new zircon data, enabled Jenkins et al. (2002) to revise this age to 522 ± 2.0 Ma. However, this age is not very well biostratigraphically constrained in the area of outcrop. It is overlain unconformably by the thick (∼8–10 km), predominantly flyschoid sediments of the Kanmantoo Group that contains very few, poorly preserved trilobites and brachiopods (Jago and Haines, 1997). The Kanmantoo Group is intruded by an early syntectonic granitoid known as the Rathjen Gneiss, which has a U–Pb date of 514 ± 4 Ma (Foden et al., 1999)."

"The tuff horizon is quite close to the only known trilobite fauna within the Heatherdale Shale. This comprises a few poorly preserved specimens of the trilobite Atops briandailyi (Jago et al., 1984; Jenkins and Hasenohr, 1989; Jenkins et al., 2002). The tuff horizon is over 400 m stratigraphically higher than the only reasonably well constrained biostratigraphic horizon in the Fleurieu Peninsula Cambrian succession. This horizon contains archaeocyaths in the top of the Sellick Hill Formation and the bottom part of the Fork Tree Limestone that Zhuravlev and Gravestock (1994) considered to be latest Atdabanian. Based on both biostratigraphy and sequence stratigraphy, Gravestock (1995) correlated the Heatherdale Shale with the biostratigraphically controlled successions of Yorke Peninsula and the Flinders Ranges. He suggested that the Heatherdale Shale should be correlated with the Mernmerna Formation and Oraparinna Shale that contain Pararaia janeae Zone (equivalent to the Botoman) trilobites in the Central Flinders Ranges."

"With respect to Yorke Peninsula, Gravestock (1995) correlated the upper Heatherdale Shale to the upper part of the Koolywurtie Member of the Parara Limestone; this contains archaeocyaths of the Syringocnema favus beds, implying a middle to late Botoman age (Zhuravlev and Gravestock, 1994). This is supported by the work of Zhou and Whitford (1994) who reported a U–Pb age of 525 ± 8 Ma with standard SL13 from a felsic tuff within the Cymbric Vale Formation of western New South Wales; Jenkins et al. (2002) recalculated this age to 517.8 ± 2.1 Ma. Both archaeocyath (Zhuravlev and Gravestock, 1994) and trilobite faunas (Jago et al., 1997; Paterson, 2005) from the Cymbric Vale Formation support a mid to late Botoman age."

"Gravestock and Shergold (2001) reported a SHRIMP age of 522.8 ± 1.8 Ma (SL13 standard) from the lower part of the Billy Creek Formation in the Arrowie Basin. It should be noted that the value of SHRIMP dates based on the SL13 standard has been questioned by Black et al. (1997) because of doubts as to the reliability of this standard (see also Jago and Haines, 1998; Paterson, 2005). In the Warburton Basin, Sun (1998) quoted an unpublished U–Pb zircon dating of 517 ± 9 Ma from the Mooracoochie Volcanics that unconformably lie below the fossiliferous succession."

Terreneuvian
541.0 ± 1.0 – ~521 Ma.

The Terreneuvian Series includes Cambrian Stage 2 and the Fortunian Stage.

Stage 2
~529 – ~521 Ma.

"Hallucigeniids are [...] an important and widespread component of disparate Cambrian communities from late in the Terreneuvian (Cambrian Stage 2) through the ‘middle’ Cambrian (Series 3); their apparent decline in the latest Cambrian may be partly taphonomic. The cone-in-cone construction of hallucigeniid sclerites is shared with the sclerotized cuticular structures (jaws and claws) in modern onychophorans."

In the image on the right "Hallucigenia sparsa [is] from the Burgess Shale: (a,b) Smithsonian Institution, National Museum of Natural History (NMNH) 83935 (holotype), articulated specimen, showing seven pairs of spines, partially decayed towards the rear, presumed head to the right. (a) composite image of part and counterpart; (b) enlargement of the basal part of the spines; (c,d) Royal Ontario Museum (ROM) 61513, complete specimen showing seven pairs of spines and backscatter image of boxed area (d); (e–i) ROM 57776, backscatter images (overview and close-ups of boxed areas) of spine showing four internal cones and lineations; (g) ROM 61513, backscatter image showing lineations and a distal cone; (j–o) ROM 62269, backscatter images of several spines, showing elemental distribution of carbon (l) and phosphorous (m) and details of ornamentation near spines’ mid-length (n) and base (o) (arrows indicate local disturbances in the rhomboid pattern); (p) ROM 61513, backscatter image showing details of ornamentation showing scales in positive relief (top left) and negative relief below the carbon film. Ba, basal region of spines; C, cone; Li, lineations. Scale bars: (a–d) 1000 µm; (e,j–m) 100 µm; (f–i) 50 µm; (n–p) 10 µm."

Atdabanian
Russian-Kazakhian Stage: Atdabanian (530 - 524 Ma).

"Lower Cambrian (Atdabanian) material [is] from the Batenev Ridge, West Siberia (Russia)."

"[S]ponge spicules and protoconodonts, characteristic of the Upper Atdabanian and Botomian stages, as well as radiolarians were found in the siliceous mudstone lenses of this formation (Obut and Iwata, 2000, Zybin et al., 2000)."

Trilobites:
 * Nevadella eucharis is known from the Middle Member of the Poleta Formation, Esmeralda County, Nevada, USA.
 * Nevadella keelensis is known from the Sekwi Formation, Northwest Territories, Canada.
 * Nevadella mountjoyi is known from the Mural Formation, north slope of Mount Mumm, Alberta, Canada.
 * Nevadella perfecta is known from the Mahto Formation, Mumm Peak on the west side of Hitka Pass, western Alberta, Canada.

Biostratigraphic zones:
 * 1) Judomia–Uktaspis (Prouktaspis)
 * 2) Delgadella anabara
 * 3) Repinaella
 * 4) Profallotaspis jakutensis

Montezuman
Montezuman North American Stage, from 529.5 to 524.5 Ma.


 * 1) Nevadella eucharis and/or Nevadella perfecta
 * 2) Nevadia addyensis
 * 3) Avefallotaspis Maria
 * 4) Grandinasus patula
 * 5) Esmeraldina rowei

Qungzusian
Qungzusian Chinese Stage, from 532 to 523 Ma.

Fortunian
541.0 ± 1.0 – ~529 Ma.

The FAD of Trichophycus pedum is the primary stratigraphic tool for correlation of the base (GSSP) for the Fortunian Stage.

Tommotian
Tommotian Russian-Kazakhian Stage, from 534 to 530 Ma.

Manzherok Formation
"The Manzherok Formation is essentially a thick (up to 1,250 m) sequence of Lower Cambrian basaltic lavas that overly unconformably the Baratal Formation. Blocks of brecciated silicified carbonate rocks which reflect accumulation in a slope depositional environment are present in places. They contain algae, microphytoliths and sponge spicules (Safonova et al., 2011, Zybin et al., 2000)."

Biostratigraphic zones:
 * 1) Dokidocyathus lenaicus– Tumuliolinthus primigenius
 * 2) Dokidocyathus regularis
 * 3) Nochoroicyathus sunnaginicus

Meishuchuan
Chinese Stage: Meishuchuan (542 - 532 Ma).

Nemakit-Daldynian
Nemakit-Daldynian Russian-Kazakhian Stage, from 542 ± 0.3 To 534 Ma. Start Defined By: Trace fossil, lowest occurrence of Treptichnus (Phycodes) pedum. Near base of negative carbon-isotope excursion.

"The Vendian-Cambrian sequence that crops out along the Katun’ River (northern Gorny Altai, Katun’ zone) is mainly composed of a thick sequence of biogenic carbonate sedimentary rocks that accumulated on shallow marine depositional environments of a basaltic plateau. They belong to two laterally coeval formations, which may reach 1000 m in thickness: the Baratal Formation, made essentially of thick-bedded partly stromatolitc limestones, underlain by black shales, and the Eskongo Formation, made of dark colored dolomites and limestones with some intercalations of chert [...]. These oldest parts of the Katun sedimentary sequence are considered as Vendian to Early Cambrian (Tommotian) in age; the Baratal Formation contains microphytolites of a Vendian age (Buslov et al., 1993, Zybin and Sergeev, 1978)."

Baratal Formation
The "Baratal Formation [is] made essentially of thick-bedded partly stromatolitc limestones".

The "Baratal Formation contains microphytolites of a Vendian age (Buslov et al., 1993, Zybin and Sergeev, 1978)."

Eskongo Formation
"The Eskongo Formation contains microphytolites, calcareous algae and shelly microfauna characteristic of a Vendian-Early Cambrian age (Terleev, 1991). A lot of sponge spicules (Protospongia sp. and Chancelloria sp. and specimens of Monaxonellida, Hexactinellida and Tetraxonida) were also identified in the siliceous levels of this Formation (Zybin et al., 2000)."

Precambrian
Precambrian (4567.17 - 542 Ma).

Def.
 * 1) "the time and geology dated before the Phanerozoic" or
 * 2) the "eon (or supereon) and rock formations dated before 541.0±1.0 million years ago, coinciding with the first appearance of the fossils of hard-shelled animals"

is called the precambrian.

Usage notes


 * The International Commission on Stratigraphy, which attempts to standardize the vocabulary of the field, is revising the boundaries between time periods based on physical-science methods rather than the kinds of fossils present.
 * The boundary between the Precambrian and the Phanerozoic has been changed from time to time and will be subject to change.

Poundian
Australian stage Poundian (570 - 542 ± 0.3) Ma.

Hypotheses

 * 1) Each time frame or span of time in geochronology has at least one dating technique.
 * 2) Late Ordovician and Upper Ordovician are different time frames.