Geochronology/Paleontology

Def. the study "of the forms of life existing in prehistoric or geologic times" is called paleontology.

Clades from the paleontological rock record sometimes display a clade asymmetry. "(Our two cases of Metazoa and mammals represent the first filling of life's ecological "barrel" for multicellular animals, and the radiation of mammals into roles formerly occupied by dinosaurs.)"

Fossils
Def. "the mineralized remains of an animal or plant" or any "preserved evidence of ancient life, including shells, imprints, burrows, coprolites, and organically-produced chemicals" is called a fossil.

Derived terms include "ichnofossil, index fossil, living fossil, "mesofossil, microfossil," and trace fossil".

Def. "any ancient remains of a plant or animal that lived during a specific geological period and that can be used to date the containing rocks" is called an index fossil.

Geologic time
At right is a geologic clock representation which shows some of the major units of geological time and definitive events of Earth history, where the Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).

19th Century
Charred material from the Lake Pátzcuaro Basin, Mexico, was radiocarbon dated at 1715-1895 AD (120 b2k intercept).

18th Century
The more recent dated logboat of Ireland is from or known as Bond's Bridge, Cos AmlaghJTyrone, to 245 ± 15 b2k.

17th Century
A logboat from Northern Ireland designated GrN-14744 dates to 305 ± 30 b2k.

16th Century
A logboat from Ireland (Derryloughan B, Co. Tyrone) designated GrN-14738 dates to 410 ± 35 b2k.

15th century
A logboat from Ireland, Derryloughan A, Co. Tyrone, designated GrN-14737, has been radiocarbon dated to 570 ± 25 BP or b2k.

14th century
Radiocarbon dating of a corner piece of the Shroud of Turin placed it between the years 1260 and 1390, in the High to Late Middle Ages, which is consistent with "its first recorded exhibition in France in 1357."

Charred materials from the Lake Pátzcuaro Basin, Mexico, were radiocarbon dated at 1170-1300 AD (680 b2k intercept), 1230-1315 AD (665 b2k intercept), 1300-1415 AD (605 b2k intercept), 1320-1535 AD (540 b2k intercept) and 1320-1435 AD (500 b2k intercept).

13th century
The book was bound more than 100 years later with covers made of oak surrounded by leather, where the oak has been dated to 1264 using dendrochronology, and the oak trees used grew in the vicinity of Skara.

"In a meta-analysis of 1,434 radiocarbon dates from the region, reliable short-lived samples reveal that the colonization of East Polynesia occurred in two distinct phases: earliest in the Society Islands A.D. ~1025–1120, four centuries later than previously assumed; then after 70–265 y, dispersal continued in one major pulse to all remaining islands [15 archipelagos of East Polynesia, including New Zealand, Hawaii, and Rapa Nui] A.D. ∼1190–1290."

12th century
Recent dating of Sweden's oldest book, the Skara Missal [in the image on the left] shows that the book is just that: Sweden's oldest.

Researchers at Lund University concluded using radiocarbon dating that the book's pages are from the year 1150, i.e. at the time of the opening of the Skara cathedral.

Charred materials from the Lake Pátzcuaro Basin, Mexico, were radiocarbon dated at 970-1,170 AD (885 b2k intercept) and 1,010-1275 AD (775 b2k intercept).

11th century
"All 5 pieces of the famous Swedish Överhogdal [tapestries such as the portion shown in the image on the right] were examined [by radiocarbon dating to 900 - 1100]."

Radiocarbon dating of charcoal fragments from Koumbi Salehin, a settlement in south east Mauritania, indicate the site was continuously occupied from the 8th/9th to the 13th centuries.

10th century
The Norse settlement of Vinland at L’Anse aux Meadows National Historic Site, Newfoundland, in the image on the left, has been radiocarbon dated to c. 1000, or 1,000 b2k.

8th century
"The Strood causeway to Mersea Island was thought to be Roman, built in the 1st c. AD. It leads to Mersea’s Roman burial mound (barrow) where a typical Roman lead covered box with a no less typical Roman glass urn (tentatively dated between 100 and 120 AD) was retrieved [in the image on the right]. Oak piles in typical Roman cut were discovered in 1978. Up to the 1980s it was never doubted that the dam was built by Romans in the 1st c. AD to reach their settlements on the Island."

"Scientific dating methods have been applied to some substantial oak piles discovered beneath the Strood in 1978, when a water-main was being laid. They indicate that the structure was probably built between A.D. 684 and 702. The piles were discovered at the south end of the causeway where the trench was at its deepest—they were about 1.6m below the present ground level and were sealed by a series of road surfaces. Seven piles were recovered and samples were submitted to Harwell laboratory for radiocarbon dating to get a rough idea of the date. Samples from four of the piles were sent to the University of Sheffield for tree ring dating (dendrochronology). The remaining three piles are now in the Colchester and Essex Museum. The dating of the construction to AD 684 to 702 was regarded as conclusive."

Subatlantic period
"The main discontinuity in the climatic condition during the Bronze Age and Iron Age transition can be identified in the boundary from Subatlantic to Subboreal (2800-2500 BP; 996/914-766/551 2σ cal. BC). Such period “has globally been identified as a time of marked climatic change. Stratigraphical, paleobotanical and archaeological evidence point to a change from a dry and warm to a more humid and cool climate in central and northwestern Europe” (Tinner et al. 2003). The climatic deterioration which characterizes this chronological range is directly responsible of the plateau in the calibration curve between 760 and 420 BC (2500-2425 BP) (see chapter 4.3.2.1). The climatic oscillation around 2700 BP (896/813 2σ cal. BC) has been detected worldwide. Van Geel et al. (1996, 1998) and Speranza et al. (2002) found an abrupt shift around 850 BC in changing species composition of peat-forming mosses in European Holocene raised bog deposits. The change was from mosses preferring warm conditions to those preferring colder and wetter environments. Archaeological evidence supports such a change. Bronze Age settlements located in the Netherlands were suddenly abandoned after a long period of occupation which last around one millennium (Dergachev et al. 2004). Other studies confirmed the climatic discontinuity; Schilman et al. (2001) studied δ18O and δ13C in deposits from the southeastern Mediterranean, off Israel, and recognized the presence of two humid events in the time ranges of 3500-3000 BP (1884/1772-1263/1215 2σ cal. BC) and 1700-1000 BP (332/389-1016/1030 2σ cal. AD) and a period of arid conditions between 3000 and 1700 BP (1263/1215 2σ cal. BC- 332/389 2σ cal. AD). Barber and Langdon (2001) identified three main long climatic deteriorations 2900-2830 BP (1119/1037-1012/934 2σ cal. BC), 2630-2590 BP (810/797-801/788 2σ cal. BC) and 1550-1400 BP (430/549-637/658 2σ cal. AD) through the analysis of plant macrofossils in a peat deposit of Walton Moss located in Northern England and comparing such data with a temperature reconstruction based on chironomids in the sediment of a nearby lake."

Subboreal period
The "period around 850-760 BC, [2850-2760 b2k, is] characterised by a decrease in solar activity and a sharp increase of Δ 14C [...] the local vegetation succession, in relation to the changes in atmospheric radiocarbon content, shows additional evidence for solar forcing of climate change at the Subboreal - Subatlantic transition."

The "apparent reality of social equality testified by LBA urnfield burials can be definitely discarded at the Iron Age transition by the archaeological excavation at the Hexenbergle site, near Wehringen in Bayern (Germany). The monumental radiocarbon dated mound with a cremation burial of an adult male accompanied by a great amount of objects, including a sword, elements decorating a wagon and an extensive set of painted pottery (Hennig 1995). The dendrochronological date obtained on the wagon (778±5BC) provides a precise temporal location for an upper-class deceased with sepulchral paraphernalia in the Hallstatt period (Friedrich & Henning 1995, 1996)."

Bronze Ages
Radiocarbon "data indicate that the New Kingdom of Egypt started between 1570 and 1544 B.C.E [3570 - 3544 b2k]."

High precision radiocarbon dating of 18 samples from Jericho, including six samples of carbonized cereal from the burnt stratum, gave the age of the strata as 1562 BC, with a margin of error of 38 years [3562 ± 38 b2k].

A logboat from Ireland (Inch Abbey, Co. Down) was dendrochronology dated to 4140 b2k.

A logboat made from alder from Denmark (Verup l) designated K-4098B was radiocarbon dated to 4220 ± 75 b2k.

A logboat from Ireland (Ballygowan, Co. AmJagh) designated GrN-20550 was radiocarbon dated to 4660 ± 40 b2k.

Atlantic
The "Atlantic period [is from] 4.6–6 ka [6,000 to 4,600 b2k]."

"The Atlantic is equivalent to Pollen Zone VII."

Northgrippian
The "Scandinavian one 2000 years earlier [8,000 b2k]."

Boreal transition
"In recent years, the German oak chronology has been extended to 7938 BC [9938 b2k]. For earlier intervals, tree-ring chronologies must be based on pine, because oak re-emigrated to central Europe at the Preboreal/Boreal transition, at about 8000 BC [10,000 b2k]."

"The age range, 7145-7875 BC [9145-9875 b2k], is represented by the oak chronology, 'Main9'."

"The age range, 7833-9439 BC [9833-11439 b2k], is covered by the 1784-yr pine chronology."

Pre-Boreal transition
"About 9000 years ago the temperature in Greenland culminated at 4°C warmer than today. Since then it has become slowly cooler with only one dramatic change of climate. This happened 8250 years ago [...]. In an otherwise warm period the temperature fell 7°C within a decade, and it took 300 years to re-establish the warm climate. This event has also been demonstrated in European wooden ring series and in European bogs."

"The Pre-boreal period marks the transition from the cold climate of the Late-glacial to the warmer climate of Post-glacial time. This change is immediately obvious in the field from the nature of the sediments, changing as they do from clays to organic lake muds, showing that at this time a more or less continuous vegetation cover was developing."

"At the beginning of the Pre-boreal the pollen curves of the herbaceous species have high values, and most of the genera associated with the Late-glacial fiora are still present e.g. Artemisia, Polemomium and Thalictrum. These plants become less abundant throughout the Pre-boreal, and before the beginning of the Boreal their curves have reached low values."

">10,500-year-old human-modified bones for the extinct elephant birds Aepyornis and Mullerornis, [in the image on the right] show perimortem chop marks, cut marks, and depression fractures consistent with immobilization and dismemberment."

"Our evidence for anthropogenic perimortem modification of directly dated bones represents the earliest indication of humans in Madagascar, predating all other archaeological and genetic evidence by >6000 years and changing our understanding of the history of human colonization of Madagascar."

Younger Dryas
The "Alleröd/Younger Dryas transition [occurred] some 11,000 years ago [11,000 b2k]."

From "stable isotope measurements of the pine series (Becker, Kromer & Trimborn 1991) [...] an age of 11,050 cal BP for the beginning of climatic amelioration in central Europe [is obtained]."

Upper Pleistocene
Neanderthal Man (Homo neanderthalensis) inhabited Eurasia until becoming extinct between 40 and 30 ka. Towards the end of the Pleistocene and possibly into the early Holocene, several large mammalian species including the woolly rhinoceros, mammoth, mastodon and Irish elk became extinct.

Cave paintings have been found at Lascaux in the Dordogne which may be more than 17,000 years old. These are mainly of European bison (buffalo), deer and other animals hunted by man. Later paintings occur in caves throughout the world with further examples at Cave of Altamira (Spain) and in India, Australia and the Sahara.

Magdalenian hunter-gatherers were widespread in western Europe about 18,000 years ago until the end of the Pleistocene. They invented the earliest known harpoons using reindeer horn.

The only domesticated animal in the Pleistocene was the dog, which evolved from the grey wolf into its many modern breeds. It is believed that the grey wolf became associated with hunter-gatherer tribes around 15 ka. The earliest remains of a true domestic dog have been dated to 14,200 years ago. Domestication first happened in Eurasia but could have been anywhere from Western Europe to East Asia. Domestication of other animals such as cattle, goats, pigs and sheep did not begin until the Holocene when settled farming communities became established in the Near East. The cat was probably not domesticated before c. 7500 BC at the earliest, again in the Near East.

A butchered brown bear patella found in Alice and Gwendoline Cave in County Clare and dated to 10,860 to 10,641 BC indicates the first known human activity in Ireland.

The very first human habitation in the Japanese archipelago has been traced to Japanese Paleolithic (prehistoric times) between 40,000 BC and 30,000 BC. The earliest fossils are radiocarbon dated to c. 35,000 BC. Japan was once linked to the Asian mainland by land bridges via Hokkaido and Sakhalin Island to the north, but was unconnected at this time when the main islands of Hokkaido, Honshu, Kyushu and Shikoku were all separate entities.

From about 28 ka, there were migrations across the Bering land bridge from Siberia to Alaska. The people became the Indigenous peoples of the Americas (Native Americans0. It is believed that the original tribes subsequently moved down to Central and South America under pressure from later migrations.

In the North American land mammal age scale, the Rancholabrean spans the time from c. 240,000 years ago to c. 11,000 years ago. It is named after the Rancho La Brea fossil site in California, characterised by extinct forms of bison in association with other Pleistocene species such as the mammoth.

Bison occidentalis and Bison antiquus, an extinct subspecies of the smaller present-day bison, survived the Late Pleistocene period, between about 12 and 11 ka ago. Clovis peoples depended on these bison as their major food source. Earlier kills of camels, horses, and muskoxen found at Wally's beach were dated to 13.1–13.3 ka B.P.

The South American land mammal age Lujanian corresponds with the Late Pleistocene.

There is evidence of human habitation in mainland Australia, Indonesia, New Guinea and Tasmania from c. 45,000 BC. The finds include rock engravings, stone tools and evidence of cave habitation.

Allerød Oscillation
The "Allerød Chronozone, 11,800 to 11,000 years ago".

"Kamminga and Wright (1988), Wright (1995) and Neves and Pucciarelli (1998) have demonstrated, however, that the Zhoukoudian Upper Cave (UC) cranium 101 display marked similarities with Australo-Melanesians. Cunningham and Wescott (2002) has shown that although highly variable, none of the three specimens from this site (UC 101, UC 102, UC 103) resembles modern Asian populations. Matsumura and Zuraina (1999:333) reported the presence of the “Australo-Melanesian lineage” in Malaysia as late as the terminal Pleistocene. If we consider that UC is dated to between 32,000 BP and 11,000 BP, the fixation of the classical Mongoloid morphology in North Asia could have been a recent phenomenon (terminal Pleistocene/early Holocene), a hypothesis favored by several authors (see Cunningham and Wescott, 2002 for a review)."

"Accordingly, an Australo-Melanesian-like population present in North Asia by the end of the Pleistocene could have been the source of the first Americans. This would explain the presence of a non-Mongoloid morphology in the New World without invoking a direct transpacific route departing from Australia, as suggested by Rivet (1943)."

"Lahr (1995) has argued that human diversity in northern Asia was probably higher in the final moments of the Pleistocene than today, at least as far as cranial morphology is concerned. Therefore, non-Mongoloid Asians could have arrived in the Americas using the Behring Strait as the gate of entry following either the shore of Beringia or a land bridge."

"[Before the pharaohs and pyramids of the Dynastic period starting about 3,100 BC], about 9,300-4,000 BC, enigmatic Neolithic peoples flourished. [It] was the lifestyles and cultural innovations of these peoples that provided the very foundation for the advanced civilisations to come."

Mesolithic
The mesolithic period dates from around 13,000 to 8,500 b2k.

"The Siwan people are mostly Berbers, the indigenous people who once roamed the North African coast between Tunisia and Morocco. They inhabited the area as early as 10,000 B.C., first moving toward the coast but later inland as conquering powers pushed them to take refuge in the desert."

"Bruine Bank, an area in the North Sea, is known to fishermen for mainly two things: the excellent catch rates when the weather is cold – and the bones, mammoth teeth, and even artefacts which frequently get caught in the nets [...] The bones, teeth and artefacts stem from a long lost land, Doggerland. Until the end of the last Ice Age, about 8000 years ago, the North Sea was still a part of the continent, even beyond the British Isles. [...] The oldest find is a fragment of a Neanderthal skull which is at least 35,000 years old – possibly even much older, up to 75,000 would be possible. 35,000 old stone tools of the Paleolithic have more than once been dragged inadvertendly to the surface by the fishermen with their mussel vacuum harvesters."

Older Dryas
"Older Dryas [...] events [occurred about 13,400 b2k]".

"The most negative δ 18O excursions seen in the GRIP record lasted approximately 131 and 21 years for the [inter-Allerød cold period] IACP and [Older Dryas] OD, respectively. The comparable events in the Cariaco basin were of similar duration, 127 and 21 years. In addition to the chronological agreement, there is also considerable similarity in the decade-scale patterns of variability in both records. Given the geographical distance separating central Greenland from the southern Caribbean Sea, the close match of the pattern and duration of decadal events between the two records is striking."

In the figures on the right, especially b, is a detailed "comparison of δ 18O from the GRIP ice core24 with changes in a continuous sequence of light-lamina thickness measurements from core PL07-57PC. Both records are constrained by annual chronologies, although neither record is sampled at annual resolution. The interval of comparison includes the inter-Allerød cold period (12.9-13 cal. kyr BP) and Older Dryas (13.4 cal. kyr BP) events (IABP and OD from a). The durations of the two events, measured independently in both records, are very similar, as is the detailed pattern of variability at the decadal timescale."

Bølling Oscillation
The "intra-Bølling cold period [IBCP is a century-scale cold event and the] Bølling warming [occurs] at 14600 cal [calendar years, ~ b2k] BP (12700 14C BP)".

"The second wave to Australia according to the old model were the Carpinterians. They came 10-15,000 YBP and are thought to have come from India. Logically these were Indian Australoid/Veddoid types from the south. All Indians looked like Aborigines (Australoid) until 8,000 YBP. The transition towards Caucasoid only occurred in the last 8,000 years. It may well have been this Carpinterian group that brought the dingo digs along with themselves in a seaward movement to Australia ~13,000 YBP."

"Another group that may well be remnants of the Ancient NE Asians may be the Ainu, but they only showed up 14,000 YBP, and by that time, the Ancient Northeast Race was well underway. However, the Ainuid types seem to have spread out quite a bit. Remains from Northern China from 9,000 YBP appear Ainuid. Ainuid or Australoid types were the first people to come to the Americas. There are a few tribes left who seem to be the remnants of these ancient people. One was an extinct tribe in Baja California called the Guaycuru. I am thinking that the Gilyak may also be part of this ancient race. In phenotype, the Gilyak look more Japanese to me than anything else."

Oldest Dryas
"More than 15,000 years ago, humans began crossing a land bridge called Beringia that connected their native home in Eurasia to modern-day Alaska. Who knows what the journey entailed or what motivated them to leave, but once they arrived, they spread southward across the Americas."

Meiendorf Interstadial
The Meiendorf Interstadial is typified by a rise in the pollens of dwarf birches (Betula nana), willows (Salix sp.), sandthorns (Hippophae), junipers (Juniperus) and Artemisia.

The beginning of the Meiendorf Interstadial is around 14,700 b2k.

Hasselo stadial
The "Hasselo stadial [is] at approximately 40-38,500 14C years B.P. (Van Huissteden, 1990)."

"One of two strongly rounded fragments of the mammoth maxilla from the Shapka Quarry in the southern Leningrad region was recently dated at 38450 + 400/–300 years (GrA-39 116) and rhinoceros remains (spoke bone), back to 38360 + 300/–270 years ago (GrA-38 819) [7]. The maxilla fragments occurred in sediments of the Leningrad Interstadial, which correspond to the transition between the Hasselo Stadial (44–39 ka ago) and the Hengelo Interstadial (38–36 ka ago)."

Marine Isotope Stage 3
The site, which dates to approximately 60,000 years ago, is believed to show evidence of hunting by Neanderthals (Homo neanderthalensis). The finds include the in-situ remains of at least nine woolly mammoths (Mammuthus primigenius), associated with Mousterian stone tools and debitage. The artefactual, faunal and environmental evidence were sealed within a Middle Devensian palaeochannel with a dark organic fill. Well preserved in-situ sites of the time are exceedingly rare in Europe and very unusual within a British context.

The site also produced rhinoceros teeth, antlers, as well as other faunal evidence. The stone tools on the site numbered 600, made up of individual artefacts or waste flakes. Particularly interesting were the 44 hand axes of sub-triangular or ovate form.

Marine Isotope Stage 4
"During the Middle Stone Age of Southern Africa, technological and behavioral innovations led to significant changes in the lifeways of modern humans. The glacial episode of Marine Isotope Stage 4, about 57-71,000 years ago, resulted in cooler and drier climatic conditions and the expansion of grassland vegetation. Sea level dropped by as much as 80 meters below its current level. During this period the cultural phase known as the Howieson’s Poort appeared across much of Southern Africa, peaking at about 60-65,000 years ago, and then disappeared. The lithic industry of the Howieson’s Poort is exemplified by changes in technology, such as the use of the punch technique, an increase in the selection of fine-grained silcrete, and the predominance of retouched pieces including backed tools, segments, scrapers and points. Segments are the type fossil of the Howieson’s Poort and represent multi-purpose armatures that were hafted onto wooden spear shafts. The standardized design and refined style of segments convey information about the behavior of their makers and provide insight about group identity. Increasing use of ochre, the presence of engraved ostrich eggshells, and a bone tool industry are associated with these stone artifacts. Also evident is an intensified use of space. Taken together, these behaviors suggest that the Howieson’s Poort represents a clear marker of modern human culture."

Chibanian
The Chibanian, widely known by its previous designation of Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene epoch within the ongoing Quaternary period. The Chibanian name was officially ratified in January 2020. It is currently estimated to span the time between 0.770 Ma (770,000 years ago) and 0.126 Ma (126,000 years ago), also expressed as 770–126 ka. It includes the transition in paleanthropology from the Lower Palaeolithic to the Middle Paleolithic over 300 ka.

The Chibanian is preceded by the Calabrian and succeeded by the proposed Tarantian. The beginning of the Chibanian is the Brunhes–Matuyama reversal, when the Earth's magnetic field last underwent reversal. It ends with the onset of the Eemian interglacial period (Marine Isotope Stage 5).

The term Middle Pleistocene was in use as a provisional or "quasi-formal" designation by the International Union of Geological Sciences (IUGS). While the three lowest ages of the Pleistocene, the Gelasian, Calabrian and Chibanian have been officially defined, the Late Pleistocene has yet to be formally defined, along with consideration of a proposed Anthropocene sub-division of the Holocene.

The International Union of Geological Sciences (IUGS) had previously proposed replacement of the Middle Pleistocene by an Ionian Age based on strata found in Italy. In November 2017, however, the Chibanian (based on strata at a site in Chiba Prefecture, Japan) replaced the Ionian as the Subcommission on Quaternary Stratigraphy's preferred GSSP proposal for the age that should replace the Middle Pleistocene sub-epoch. The "Chibanian" name was ratified by the IUGS in January 2020.

The Chibanian includes the transition in paleanthropology from the Lower Palaeolithic to the Middle Palaeolithic: i.e., the emergence of Homo sapiens sapiens between 300 ka and 400 ka. The oldest known human DNA dates to the Middle Pleistocene, around 430,000 years ago. This is the oldest found.

Illinois Episode glaciations
"Illinoian [is] (ca. 220,000-430,000 yr BP)".

"The [Jebel Irhoud site] Moroccan fossils [...] are roughly 300,000 years old. Remarkably, they indicate that early Homo sapiens had faces much like our own, although their brains differed in fundamental ways."

"We did not evolve from a single 'cradle of mankind' somewhere in East Africa. We evolved on the African continent."

"It now looks like Denisovans can be placed at the site from close to 300,000 years ago to about 50,000 years ago, with Neandertals there for periods in between."

Yarmouthian interglacial
"The extinctions and earliest known first occurrences of the 26 extant and 8 extinct cyst taxa in the three samples (with a minimum 430,000 yr BP Yarmouthian age) corroborate a likely assemblages with a maximum age of Illinoian (ca. 220,000-430,000 yr BP) in Unit I."

Aftonian interglacial
"The age of the [stag moose Cervalces] roosevelti type specimen is pre-Wisconsin (Aftonian)".

Calabrian
"The boundary falls between the highest occurrence of Discoaster brouweri (below) and the lowest common occurrence of left-coiling Neogloboquadrina pachyderma (above), and below the lowest occurrences of medium-sized Gephyrocapsa (including G. oceanica) and Globigerinoides tenellus."

Tertiary
The Tertiary Period extends from 65.5 ± 0.3 to 2.588 x 106 b2k.

Neogene
The Neogene dates from 23.03 x 106 to 2.58 x 106 b2k.

Pliocene
The Pliocene ranges from 5.332 x 106 to 2.588 x 106 b2k.

"All of Pliocene time, without a gap, is physically represented in the three stages of which it is composed, in a single demonstrably uninterrupted sequence of highly fossiliferous Upper Cenozoic deep-water strata on the southern coast of Sicily. From bottom to top, the Pliocene consists of the Lower Pliocene Zanclean Stage, with a boundary-stratotype at Eraclea Minoa and a unit-stratotype at Capo Rossello; the Middle Pliocene Piacenzian Stage, defined at Punta Piccola (Castradori et al., 1998); and the Upper Pliocene Gelasian Stage, defined at Monte San Nicola near Gela (Rio et al., 1994, 1998) [...]."

Miocene
The Miocene dates from 23.03 x 106 to 5.332 x 106 b2k.

Messinian
"The GSSP of the Messinian Stage, which per definition marks the base of the Messinian and, hence, the boundary between the Tortonian and Messinian Stages of the Upper Miocene Subseries, is Oued Akrech (Morocco) where the Messinian GSSP is now formally designated at the base of the reddish layer of sedimentary cycle no. 15. This point coincides closely with the first regular occurrence (FRO) of the planktonic foraminiferal Globorotalia miotumida group and the first occurrence (FO) of the calcareous nannofossil Amaurolithus delicatus, and falls within the interval of reversed polarity that corresponds to C3Br.1r. The base of the reddish layer and, thus, the Messinian GSSP has been assigned an astronomical age of 7.251 Ma."

Tortonian
The Tortonian lasted from 11.63 Ma to 7.246 Ma.

Gigantopithecus is an extinct genus of ape that existed from perhaps nine million years to as recently as one hundred thousand years ago, at the same period as Homo erectus would have been dispersed, in what is now India, Vietnam, China and Indonesia placing Gigantopithecus in the same time frame and geographical location as several hominin species. The primate fossil record suggests that the species Gigantopithecus blacki were the largest known primates that ever lived, standing up to 3 m and weighing as much as 540 - 600 kg,  although some argue that it is more likely that they were much smaller, at roughly 1.8 - 2 m in height and 180 - 300 kg in weight.

Middle Miocene
The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two faunal stage: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene.

For the purpose of establishing European Land Mammal Ages this sub-epoch is equivalent to the Astaracian age.

Serravallian
The top of the Serravallian (the base of the Tortonian stage) is at the last common appearance of calcareous nannoplanktons Discoaster kugleri and planktonic foram Globigerinoides subquadratus. It is also associated with the short normal-polarized chronozone C5r.2n.

The Serravallian is in the middle Miocene and spans the time between 13.82 Ma and 11.63 Ma (million years ago), follows the Langhian and is followed by the Tortonian.

The base of the Serravallian is at the first occurrence of fossils of the nanoplankton species Sphenolithus heteromorphus and is located in the chronozone C5ABr. The official Global Boundary Stratotype Section and Point (GSSP) for the Serravallian is in the 'Ras il-Pellegrin' section, located at the 'Ras il-Pellegrin' headland in the vicinity of 'Fomm ir-Rih' Bay, SW Malta. The base of the Serravallian is represented in the field as the formation boundary between the Globigerina Limestone formation and the Blue Clay formation. The base of the Serravallian is related to the Mi3b oxygen isotope excursion marking the onset of the Middle Miocene Cooling step.

Langhian
The top of the Langhian stage (the base of the Serravallian stage) is at the first occurrence of fossils of the nanoplankton species Sphenolithus heteromorphus and is located in magnetic chronozone C5ABr.

The Langhian is, in the International Commission on Stratigraphy (ICS) geologic timescale, an age or stage in the middle Miocene series, spanning the time between 15.97 ± 0.05 Ma and 13.65 ± 0.05 Ma.

The base of the Langhian is defined by the first appearance of foraminifer species Praeorbulina glomerosa and is also coeval with the top of magnetic chronozone C5Cn.1n. A GSSP for the Langhian stage was not yet established in 2009.

The Langhian is coeval with the Orleanian and Astaracian European Land Mammal Mega Zones (more precisely: with biozones MN5 and MN6, MN6 starts just below the Langhian-Serravallian boundary ), with the upper Hemingfordian to mid-Barstovian North American Land Mammal Ages, with mid-Relizian to Luisian Californian regional stages (the Luisian extends barely into the early Serravallian ), with the early-mid Badenian Paratethys stage of Central and eastern Europe, with the Tozawan stage in Japan (which runs barely into the early Serravallian ), with the late Batesfordian through Balcombian to early Bairnsdalian Australian stages and with the mid-Cliffdenian to mid-Lillburnian New Zealand stages.

Paleogene
The Paleogene Period extends from 65.5 ± 0.3 to 23.03 ± 0.05 x 106 b2k.

Oligocene
The upper boundary of the Oligocene is defined by its GSSP at Carrosio, Italy, which coincides with the first appearance of the foraminiferan Paragloborotalia kugleri and with the base of magnetic polarity chronozone C6Cn.2n.

The Oligocene dates from 33.9 ± 0.1 x 106 to 23.03 x 106 b2k.

The Oligocene Epoch covers 34 - 23 Mya.

The Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene.

Oligocene faunal stages from youngest to oldest are:

The late Oligocene (26.5 to 24 mya) likely saw a warming trend in spite of low pCO2 levels, though this appears to vary by region. However, Antarctica remained heavily glaciated during this warming period. The late Oligocene warming is discernible in pollen counts from the Tibetan Plateau, which also show that the south Asian monsoon had already developed by the late Oligocene.

There appears to have been a land bridge in the early Oligocene between North America and Europe, since the faunas of the two regions are very similar. However, towards the end of the Oligocene, there was a brief marine incursion in Europe.

The Eocene-Oligocene transition, peaking around 33.5 mya, was a major cooling event and reorganization of the biosphere. The transition is marked by the Oi1 event, in which Marine isotope stages (oxygen isotope ratios) decreased by 1.3 ‰. About 0.3-0.4 ‰} of this is estimated to be due to major expansion of Antarctic ice sheets. The remaining 0.9 to 1.0 ‰ was due to about 5 to 6 C-change of global cooling. The transition likely took place in three closely spaced steps over the period from 33.8 to 33.5 mya. By the end of the transition, sea levels had dropped by 105 m, and ice sheets were 25% greater in extent than in the modern world.

The effects of the transition can be seen in the geological record at many locations around the world. Ice volumes rose as temperature and sea levels dropped. Endorheic basin (Playa) lakes of the Tibetan Plateau disappeared at the transition, pointing to cooling and aridification of central Asia. Pollen and spore counts in marine sediments of the Norwegian-Greenland Sea indicate a drop in winter temperatures at high latitudes of about 5 C-change just prior to the Oi1 event. Borehole dating from the Southeast Faroes drift indicates that deep-ocean circulation from the Arctic Ocean to the North Atlantic Ocean began in the early Oligocene.

Angiosperms continued their expansion throughout the world as tropical and sub-tropical forests were replaced by temperate deciduous forests. Open plains and deserts became more common and grasses expanded from their water-bank habitat in the Eocene moving out into open tracts. The decline in pCO2 favored C4 photosynthesis, which is found only in angiosperms and is particularly characteristic of grasses. However, even at the end of the period, grass was not quite common enough for modern savannas.

In North America, much of the dense forest was replaced by patchy scrubland with riparian forests. Subtropical species dominated with cashews and lychee trees present, and temperate woody plants such as roses, beeches, and pines were common. The legumes spread, while Cyperaceae (sedges) and ferns continued their ascent.

Most extant mammal families had appeared by the end of the Oligocene. These included primitive three-toed horses, rhinoceroses, camels, deer, and peccaries. Carnivores such as dogs, nimravids (ancestor of cats), bears, weasels, and raccoons began to replace the creodonts that had dominated the Paleocene in the Old World. Rodents and rabbits underwent tremendous diversification due to the increase in suitable habitats for ground-dwelling seed eaters, as habitats for squirrel-like nut- and fruit-eaters diminished. The primates, once present in Eurasia, were reduced in range to Africa and South America. Many groups, such as equids, entelodonts, rhinos, merycoidodonts, and camelids, became more able to run during this time, adapting to the plains that were spreading as the Eocene rainforests receded. Brontotheriidae (Brontotheres) died out in the Earliest Oligocene, and creodonts died out outside Africa and the Middle East at the end of the period. Multituberculates, an ancient lineage of primitive mammals that originated back in the Jurassic, also became extinct in the Oligocene, aside from the gondwanatheres.

The Eocene-Oligocene transition in Europe and Asia has been characterized as the Grande Coupure. The lowering of sea levels closed the Turgai Strait across the Obik Sea, which had previously separated Asia from Europe. This allowed Asian mammals, such as rhinoceroses and ruminants, to enter Europe and drive endemic species to extinction. Lesser faunal turnovers occurred simultaneously with the Oi2 event and towards the end of the Oligocene. There was significant diversification of mammals in Eurasia, including the giant indricotheres, that grew up to 6 m at the shoulder and weighed up to 20 tons. Paraceratherium was one of largest land mammals ever to walk the Earth. However, the indricotheres were an exception to a general tendency for Oligocene mammals to be much smaller than their Eocene counterparts. The earliest deer, giraffes, pigs, and cattle appeared in the mid-Oligocene in Eurasia. The first felid, Proailurus, originated in Asia during the late Oligocene and spread to Europe.

There was only limited migration between Asia and North America. The cooling of central North America at the Eocene-Oligocene transition resulted in a large turnover of gastropods, amphibians, and reptiles. Mammals were much less affected. Crocodilians and pond turtles replaced by dry land tortoises. Molluscs shifted to more drought-tolerant forms. The White River Fauna of central North America inhabited a semiarid prairie home and included entelodonts like Archaeotherium, camelids (such as Poebrotherium), running rhinoceratoids, three-toed equids (such as Mesohippus), nimravids, Protoceratidae (protoceratids), and early canids like Hesperocyon. Merycoidodonts, an endemic American group, were very diverse during this time.

Australia and South American became geographically isolated and developed their own distinctive endemic fauna. These included the New World and Old World monkeys. The South American continent was home to animals such as Pyrotheria (pyrotheres) and Astrapotheria (astrapotheres), as well as litopterns and notoungulates. Sebecosuchians, Phorusrhacidae (terror birds), and carnivorous metatheres, like the Borhyaenidae (borhyaenids) remained the dominant predators.

Africa was also relative isolated and retained its endemic fauna. These included mastodonts, hyraxes, arsinoitheres, and other archaic forms. Egypt in the Oligocene was an environment of lush forested deltas.

At sea, 97% of marine snail species, 89% of clams, and 50% of echinoderms of the Gulf Coast did not survive past the earliest Oligocene. New species evolved, but the overall diversity diminished. Cold-water mollusks migrated around the Pacific Rim from Alaska and Siberia. The marine animals of Oligocene oceans resembled today's fauna, such as the bivalves. Calcareous Cirratulidae (cirratulids) appeared in the Oligocene. The fossil record of marine mammals is a little spotty during this time, and not as well known as the Eocene or Miocene, but some fossils have been found. The baleen whales and toothed whales had just appeared, and their ancestors, the Archaeoceti (archaeocete) cetaceans began to decrease in diversity due to their lack of echolocation, which was very useful as the water became colder and cloudier. Other factors to their decline could include climate changes and competition with today's modern cetaceans and the requiem sharks, which also appeared in this epoch. Early desmostylians, like Behemotops, are known from the Oligocene. Pinnipeds appeared near the end of the epoch from an otter-like ancestor.

Evidence for ocean-wide cooling during the Oligocene exists mostly in isotopic proxies. Patterns of extinction and patterns of species migration can also be studied to gain insight into ocean conditions. For a while, it was thought that the glaciation of Antarctica may have significantly contributed to the cooling of the ocean, however, recent evidence tends to deny this.

The lower boundary of the Oligocene (its Global Boundary Stratotype Section and Point or GSSP) is placed at the last appearance of the foraminiferan genus Hantkenina in a quarry at Massignano, Italy. However, this GSSP has been criticized as excluding the uppermost part of the type Eocene Priabonian Stage and because it is slightly earlier than important climate shifts that form natural markers for the boundary, such as the global oxygen isotope shift marking the expansion of Antarctic glaciation (the Oi1 event).

Chattian
The Chattian began 27.82 Ma and ended 23.03 Ma.

The top of the Chattian stage (which is the base of the Aquitanian stage, Miocene series and Neogene system) is at the first appearance of foram species Paragloborotalia kugleri, the extinction of calcareous nanoplankton species Reticulofenestra bisecta (which forms the base of nanoplankton biozone NN1), and the base of magnetic C6Cn.2n.

The Chattian is coeval with regionally used stages or zones such as the upper Avernian European mammal zone (it spans the Mammal Paleogene zones 30 through 26 and part of 25 ); the upper Geringian and lower Arikareean NALMA (mammal zones) of North America; most of the Deseadan SALMA (mammal zone) of South America; the upper Hsandgolian and whole Tabenbulakian Asian Land Mammal Age (mammal zone0 of Asia; the upper Kiscellian and lower Egerian Paratethys stages of Central and eastern Europe; the upper Janjukian and lower Longfordian Australian regional stages; the Otaian, Waitakian, and Duntroonian stages of the New Zealand geologic time scale; and part of the Zemorrian Californian stage and Chickasawhayan regional stage of the eastern US.

The base of the Chattian is at the extinction of the foram genus Chiloguembelina (which is also the base of foram biozone P21b). An official GSSP for the Chattian stage was ratified in October of 2016.

Holarctic-Antarctic Ice Age
53 million years ago during the Eocene Epoch, summer high temperatures in Antarctica were around 25 °C (77 °F). Temperatures during winter were around 10 °C (50 °F). It did not frost during the winter. The climate was so warm that trees grew in Antarctica. Arecaceae (palm trees) grew on the coastal lowlands, and Beech Fagus (beech trees) and Pinophyta (conifers) grew on the hills just inland from the coast.

As the global climate became cooler, the planet was seeing a decrease in forests, and an increase in savannas. Animals were evolving to have a larger body size.

The first bovids, kangaroos, and mastodons came about 15 million years ago. This was the warmest part of the Late Cenozoic Ice Age, with average global temperatures around 18.4 °C (65.1 °F). Atmospheric CO2 levels were around 700 ppm. This time period was called the Mid-Miocene Climatic Optimum (MMCO).

The australopithecines first appear in the fossil record around 4 million years ago, and diversified vastly over the next 2 million years. The Mediterranean Sea was dry between 6 and 5 million years ago.

Rupelian
The Rupelian began 33.9 Ma and ended 27.82 Ma.

The top of the Rupelian stage (the base of the Chattian) is at the extinction of the foram genus Chiloguembelina (which is also the base of foram biozone P21b).

The base of the Rupelian stage (which is also the base of the Oligocene series) is at the extinction of the foraminiferan genus Hantkenina. An official GSSP for the base of the Rupelian has been assigned in 1992 (Massignano, Italy). The transition with the Chattian has also been marked with a GSSP in August 2017 (Monte Conero, Italy).

The Rupelian overlaps the Orellan, Whitneyan and lower Arikareean North American Land Mammal Ages, the upper Mustersan and Tinguirirican South American Land Mammal Ages, the uppermost Headonian, Suevian and lower Arvernian European Land Mammal Mega Zones (the Rupelian spans the Mammal Paleogene zones 21 through 24 and part of 25 ), and the lower Hsandgolian Asian Land Mammal Age. It is also coeval with the only regionally used upper Aldingan and lower Janjukian stages of Australia, the upper Refugian and lower Zemorrian stages of California and the lower Kiscellian Paratethys stage of Central and eastern Europe. Other regionally used alternatives include the Stampian, Tongrian, Latdorfian and Vicksburgian.

Eocene
The Eocene dates from 55.8 ± 0.2 x 106 to 33.9 ± 0.1 x 106 b2k.

Priabonian
The Priabonian began 37.8 Ma and ended 33.9 Ma.

Bartonian
The Bartonian began 41.2 Ma and ended 37.8 Ma.

Lutetian
The Lutetian began 47.8 Ma and ended 41.2 Ma.

Ypresian
The Ypresian began 56.0 Ma and ended 47.8 Ma.

Paleocene
The Paleocene dates from 65.5 ± 0.3 x 106 to 55.8 ± 0.2 x 106 b2k.

Thanetian
The Thanetian began 59.2 Ma and ended 56.0 Ma.

Selandian
The Selandian began 61.6 Ma and ended at 59.2 Ma.

Danian
"Although crinoids appear not to have been involved in the great change in diversity at the Cretaceous-Paleogene (K-Pg) boundary extinction event, it has been assumed that representatives of order Roveacrinida became extinct during this time. Well-preserved fossils from the Danian (early Paleocene) of Poland demonstrate that these crinoids survived into the earliest Cenozoic."

Post-"Cretaceous ammonites of the genus Hoploscaphites have been found at Stevns Klint in Denmark (Machalski & Heinberg, 2005; Machalski et al., 2009)."

"The maximum age for Danian scaphitid survivors from the Cerithium Limestone at Stevns Klint, Denmark, has recently been estimated to be around 0.2 Ma following the K–Pg boundary event (Machalski and Heinberg in press). Assuming the Cretaceous– Paleogene boundary at 65.4 ± 0.1 Ma (Jagt and Kennedy 1994), the present study covers more than 4 Ma of the final stages in scaphitid evolution."

"Scaphitid material from subunit IVf−7 at the very top of the Meerssen Member [...] traditionally regarded to be uppermost Maastrichtian, has recently been reassigned to the lowermost Danian, based on microfossil and strontium isotope evidence (Smit and Brinkhuis 1996). According to Jagt et al. (2003), the scaphitid and baculitid ammonites preserved in subunit IVf−7 are early Danian survivors."

Above center are Hoploscaphites constrictus johnjagti subsp. nov., adult macroconchs, ammonites from the Danian: A. MGUH 27366, lowermost Danian, Stevns Klint, Denmark, in apertural (A1), lateral (A2, A3), and ventral (A4) views.

San Juan Basin
"[P]ollen was the more accurate age indicator and therefore the Ojo Alamo dinosaurs were Paleocene in age. The conclusion was tentative because Paleocene pollen nowhere occurred at exactly the same locality as dinosaur bone. Paleocene pollen is present, however, in the Ojo Alamo near Barrel Spring, within one mile of the Alamo Wash bone locality [...]."

"A Cretaceous dinosaur bone collected from just below the Cretaceous-Paleogene interface yielded a U-Pb date of 73.6 ± 0.9 Ma, in excellent agreement with a previously determined 40Ar/39Ar date of 73.04 ± 0.25 Ma for an ash bed near this site. The second dinosaur bone sample from Paleocene strata just above the Cretaceous-Paleogene interface yielded a Paleocene U-Pb date of 64.8 ± 0.9 Ma, consistent with palynologic, paleomagnetic, and fossil-mammal biochronologic data."

"The second bone sample BB-1, a fragment of a large sauropod femur (Alamosaurus sanjuanensis) was collected from the Paleocene Ojo Alamo Sandstone. This bone shows much less geochemical variation than bone 22799-D and is very well preserved. The weighted average 206Pb/238U date of 64.8±0.9 Ma is interpreted to record the time of bone fossilization. Considering that fossilization times are typically less than a few thousand years, the age result from BB-1 confirms the existence of Paleocene dinosaurs. The strontium isotopic composition of both bones are relatively unradiogenic (0.70811±3 and 0.70860±3, respectively). The strontium content of both bones is remarkably homogeneous, in contrast to the chemical variability displayed by most elements, therefore we interpret the strontium isotope values to reflect the indigenous bone composition."

The right femur of the hadrosaurian dinosaur is shown at left where the bone is in place in A and after excavation, preparation, and mounting in B.

Basque Coast Geopark
"In this environment, [...] sediments and rocks that are rich in microfossils that were deposited between 66.4 and 65.4 Ma, a time interval that includes the known Cretaceous/Paleogene boundary (K/Pg) [were analyzed]. Dated in 66 Ma, the K/Pg boundary divides the Mesozoic and Cenozoic eras and it coincides with one of the five large extinctions of the planet."

"Thanks to these periodicities identified in the Zumaia sediments, we have been able to determine the most precise dating of the climatic episodes that took place around the time when the last dinosaurs lived."

"Carbon-13 isotopic analysis on the rocks in combination with the study of planktonic foraminifera ─microfossils used as high-precision biostratigraphic indicators─ has made it possible to reconstruct the paleoclimate and chronology of that time in the Zumaia sediments. More than 90% of the Cretaceous planktonic foraminiferal species from Zumaia became extinct 66 Ma ago, coinciding with a big disruption in the carbon cycle and an accumulation of impact glass spherules originating from the asteroid that hit Chicxulub, in the Yucatan Peninsula (Mexico)."

Maastrichtian
Extends from 70.6 ± 0.6 to 65.5 ± 0.3 Mya.

The center is a fossil cast of a Baculites grandis shell taken at the North American Museum of Ancient Life.

Baculites baculus, type specimen in the image at right, lower boundary of zone and lower boundary for Maastrichtian dated to 70.6 ± 0.6 Ma and upper boundary dated to 70.00 ± 0.45 Ma.

Edmontonian
Edmontonian extends from 80.8 to 70.7 Mya.

The fossil shown on the right has a bizarre and irregularly shaped shell. Such examples are called heteromorph ammonites.

Classification: Animalia, Mollusca, Cephalopoda, Ammonoidea, Ancyloceratina, Nostoceratidae.

"The Williams Fork Formation represents a period spanning seven ammonite zones from the Didymoceras cheyennense to the Baculites baculus (Meek and Hayden, 1861) Zone (Newman, 1987). Based on the timescale of Obradovich and Cobban (1975), these seven ammonite zones represent approximately three million years, correlative with the late Campanian to early Maastrichtian (Harland et al., 1990). Lillegraven and Ostresh (1990) correlated these seven ammonite zones to the Edmontonian North American Land Mammal Age (NALMA)."

Other ammonite zones include Baculites compressus from the Fruitland Formation above the Didymoceras cheyennense zone. "Baculites compressus age is from a bentonite bed in the Bearpaw Shale, Big Horn County, Montana (Obradovich, 1993 and written communication, Obradovich, 1996)."

The stratigraphic column on the left shows ammonite zones between Didymoceras nebrascense and the Maastrichtian with inferred ages.

Bentonite "marker beds are found throughout the lowermost Williams Fork Formation and the underlying Cameo Coal interval [...] the Yampa ash marker bed, is found near the top of the Cameo Coal interval, suggesting a depositional age equal to or younger than 72.2 ± 0.1 Ma for the lower Williams Fork Formation [...] and time equivalent to the previously mentioned Baculites reesidei zone (Brownfield and Johnson 2008) [...]."

Campanian
The Bearpaw Formation is famous for its well-preserved ammonite fossils. These include Placenticeras meeki and Placenticeras intercalare, and the baculite Baculites compressus.

Extends from 83.5 ± 0.7 to 70.6 ± 0.6 Mya.

The Baylis Formation, Post Creek Formation and the Tuscaloosa Formation are Upper Cretaceous from the Campanian.

Middle Cenomanian
The hierarchy of ammonites in the Middle Cenomanian is shown on the left below beginning at 95.73 ± 0.61.

Shells of Acanthoceras rhotomagensis may reach a diameter of about 36 - 50 cm. Their shells have ornate ribs.

Acanthoceras rhotomagensis fossils may be found in Western Europe and western North America.

Acanthoceras rhotomagensis fossils occur in the Middle Cenomanian just above the boundary with the Lower Cenomanian.

The "highly fossiliferous marl, 1 m in thickness, is the Cast Bed of Price (1877), [where the] lowest record of Acanthoceras rhotomagensis (Brongniart)" occurs.

Cenomanian
The Cenomanian per the International Commission on Stratigraphy is the oldest or earliest age of the Late Cretaceous or the lowest stratigraphic stage of the Upper Cretaceous.

As a unit of geologic time measure, the Cenomanian age spans the time between 100.5 ± 0.9 Ma and 93.9 ± 0.8 Ma, preceded by the Albian and is followed by the Turonian, where the Upper Cenomanian starts approximately at 95 Ma.

The base of the Cenomanian is placed at the first appearance of foram species Rotalipora globotruncanoides in the stratigraphic record, located in an outcrop at the western flank of Mont Risou, near the village of Rosans in the French Alps (département Hautes-Alpes, coordinates: 44°23'33"N, 5°30'43"E), in the reference profile, located 36 meters below the top of the Marnes Bleues Formation.

Jurassic
The Jurassic/Cretaceous boundary occurs at 144.2 ± 2.6 Ma (million years ago).

Perisphinctes tiziani is an index fossil for the Jurassic.

Toarcian
The top of the stage is at the first appearance of ammonite genus Leioceras.

The Toarcian, in the International Commission on Stratigraphy (ICS) geologic timescale, an age and stage in the Early or Lower Jurassic, spans the time between 182.7 Ma and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.

The base of the Toarcian is defined as the place in the stratigraphic record where the ammonite genus Eodactylites first appears, a GSSP for the base is located at Peniche, Portugal.

Pliensbachian
The Pliensbachian, an age of the geologic timescale and stage in the stratigraphic column, is part of the Early or Lower Jurassic epoch or series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma. The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.

The base of the Pliensbachian is at the first appearances of the ammonite species Bifericeras donovani and genera Apoderoceras and Gleviceras, with The Wine Haven profile near Robin Hood's Bay (Yorkshire, England) has been appointed as global reference profile for the base (GSSP).

The Pliensbachian contains five ammonite biozones in the boreal domain:
 * zone of Pleuroceras spinatum
 * zone of Amaltheus margaritatus
 * zone of Prodactylioceras davoei
 * zone of Tragophylloceras ibex
 * zone of Uptonia jamesoni

In the Tethys Ocean domain, the Pliensbachian contains six biozones:
 * zone of Emaciaticeras emaciatum
 * zone of Arieticeras algovianum
 * zone of Fuciniceras lavinianum
 * zone of Prodactylioceras davoei
 * zone of Tragophylloceras ibex
 * zone of Uptonia jamesoni

The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of Bifericeras donovani and of genus Apoderoceras the defining biological marker for the start of the Pliensbachian Stage of the Jurassic, 190.8 ± 1.0 million years ago.

Hettangian
"Since the 1960’s, the LO (lowest occurrence) of the ammonite Psiloceras (usually the species P. planorbis [first image on the right]) has provided the working definition of the TJB (e.g., Lloyd, 1964; Maubeuge, 1964; Cope et al., 1980; Warrington et al., 1994; Gradstein et al., 2004)."

"The Global Stratotype Section and Point (GSSP) defining the base of the Jurassic System Lower Jurassic Epoch and Hettangian Stage is situated at the Kuhjoch pass, Karwendel Mountains, Northern Calcareous Alps, Austria (47°29'02"N/11°31'50"E). The Triassic-Jurassic (T-J) boundary is exposed at Kuhjoch West and at Kuhjoch East [in the second image on the right], and corresponds to the first occurrence (FO) of the ammonite Psiloceras spelae tirolicum [at the top of this section]."

Another FO is that of "the aragonitic foraminifer Praegubkinella turgescens"

The Triassic/Jurassic boundary occurs at 205.7±4.0 Ma (million years ago).

Triassic
Trophites subbuliatus is an index fossil for the Triassic.

Induan
In the diagram on the right, the Permian-Triassic boundary is at the base of the Induan limestone that occurs within the Yinkeng Formation.

"The Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary [...] is defined at the base of Hindeodus parvus horizon, i.e. the base of Bed 27c of Meishan section D, Changxing County, Zhejiang Province, South China."

"Hindeodus parvus is now recognized as the index fossil" occurring in the Zone above the P-T boundary.

The Induan was the earliest part of the Triassic Period, and lasted from about 251.2 to about 251.902 Ma.

Gangetian
The chart above indicates that the Gangetian is in the Brahmanian.

The Permian/Triassic boundary occurs at 248.2 ± 4.8 Ma (million years ago).

Devonian
In the image on the right, a geodized brachiopod fossil is lined with calcite with a single crystal of sphalerite; Middle Devonian; Milwaukee Formation; Lindwurm Member; Milwaukee County, Wisconsin; MPM P29133; collected by K.C. Gass; photograph originally published in K.C. Gass, J. Kluessendorf, D.G. Mikulic, and C.E. Brett, 2019. Fossils of the Milwaukee Formation: A Diverse Middle Devonian Biota from Wisconsin, USA. Siri Scientific Press, Manchester, UK.

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'."

Ordovician
Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era, which spans 41.6 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.

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".

The Sandbian was the last stage of the Upper Ordovician

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.

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."

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

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.

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

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

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)

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.

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."

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

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."

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 [for the Guzhangian] 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.

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

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

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)."

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 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)."

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.

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)

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

"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

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)."

Shashkunar Formation
"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."

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).

"[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
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.

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)."

Upper Adelaidean
The Adelaidean appears to encompass the Delamerian Granites and the Adelaide Rift Complex.

"The deposits include the type sections for the often globally correlated Sturtian and Marinoan glacial sequences (e.g., Preiss, 2000) and the Global Stratotype Section and Point (GSSP) for the newly defined Ediacaran Period (Knoll et al., 2004)."

The later Adelaidean includes the Burra and Caliana Groups.

Ediacaran
"The fossils [of Dickinsonia] were unearthed at Zimnie Gory in the White Sea area of north-west Russia."

"The fossil fat molecules that we've found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought."

"Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Ediacaran Biota were. The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology."

Def. "a geologic period within the Neoproterozoic era from about 620 to 542 million years ago" is called the Ediacaran.

Gaskiers
Deposits attributed to the Gaskiers — assuming that they were all deposited at the same time — have been found on eight separate paleocontinents, in some cases occurring close to the equator (at a latitude of 10-30°). The 300 m-thick name-bearing section at Gaskiers (Newfoundland) is packed full of striated dropstones. Its values are very low (pushing 8‰), consistent with a period of environmental abnormality. The bed lies just below some of the oldest fossils of the Ediacaran biota, leading to early suggestions that the passing of the glaciation may have paved the way for the evolution of these odd organisms. More accurate dating methods have shown that there is in fact a 9 million year gap between the diamictites and the 570 Ma macrofossils.

Marinoan
The Marinoan glaciation was a period of worldwide glaciation that lasted from approximately 650 to 632.3 ± 5.9 Ma (million years ago) during the Cryogenian geologic period. The end of the glaciation might have been hastened by the release of methane from equatorial permafrost.

Elatina glaciation
"The Elatina glaciation has not been dated directly, and only maximum and minimum age limits of c. 640 and 580 Ma, respectively, are indicated."

Cryogenian ice age
Def. "a geologic period within the Neoproterozoic era from about [720] to 600 million years ago" is called the Cryogenian.

Glaciers extended and contracted in a series of rhythmic pulses, supported by microfossil lineages, possibly reaching as far as the equator.

Abundant "agglutinated tests in organic-rich carbonates directly overlying Sturtian glacial deposits [found] from two different paleocontinents: the Rasthof Formation of the Congo craton in northern Namibia and the Tsagaan Oloom Formation of the Dzabkhan terrane in Mongolia. The most abundant tests preserve morphological and compositional characters consistent with those found in at least two different families of modern lobose testate amoebae (Amoebozoa), a group of heterotrophic microbial eukaryotes. The presence of spatially and compositionally variable clay minerals, quartz and microcline on the test walls is a signature of widespread biological agglutination. The post-glacial fossil assemblages differ from the most common pre-Sturtian vase-shaped fossil testate amoebae, perhaps as a result of different preservational mechanisms or of the appearance of new forms after the glaciation."

"Sturtian cap carbonates from Namibia and Mongolia contain many agglutinated tests."

Fossils of testate amoeba (or Arcellinida) first appear during the Cryogenian period.

During the Cryogenian period, the oldest known fossils of sponges, Otavia the first sponge-like animal (and therefore animals) make an appearance.

New groups of life evolved during this period, including the red algae and green algae, stramenopiles, ciliates, dinoflagellates, and testate amoeba.

The end of the period also saw the origin of heterotrophic plankton, which would feed on unicellular algae and prokaryotes, ending the bacterial dominance of the oceans.

Sturtian
The duration of the Sturtian glaciation has been variously defined, with dates ranging from 717 to 643 Ma. Or, the period spans 715 to 680 Ma.

Pre-Sturtian
The "Mariam Bohkahko Formation, coupled with the presence of substantial stromatolitic carbonate and beds of oncoids in sediments directly below the diamictite, suggests that conditions remained warm enough to sustain shallow-water carbonate production until just prior to the deposition of glacial diamictite."

Oncolites are very similar to stromatolites, but, instead of forming columns, they form approximately spherical structures. The oncoids often form around a central nucleus, such as a shell fragment, and a calcium carbonate structure is deposited by encrusting microbes. Oncolites are indicators of warm waters in the photic zone, but are also known in contemporary freshwater environments.

"Stromatolites [are] characteristic of the Matheos-Mariam Bohkahko Formation transition."

"Oncolite [is] from the upper Mariam Bohkahko Formation 23 meters below the Negash Formation diamictite. Oncoids are up to 3 cm in diameter, and are cored by carbonate grains and shale rip-up clasts"

Fossils of testate amoeba (or Arcellinida) first appear during the Cryogenian period. During the Cryogenian period, the oldest known fossils of sponges (and therefore animals) formed.

New groups of life evolved during this period, including the red algae and green algae, stramenopiles, ciliates, dinoflagellates, and testate amoeba. The end of the period also saw the origin of heterotrophic plankton, which would feed on unicellular algae and prokaryotes, ending the bacterial dominance of the oceans.

Vendian
The Vendian occurred about 740 Ma.

Paleontological substantiation of this boundary was worked out separately for the siliciclastic basin (base of the Baltic Stage of the Eastern European Platform ) and for the carbonate basin (base of the Tommotian Stage of the Siberian Platform).

The lower boundary of the Vendian was suggested to be defined at the base of the Varanger (Laplandian) tillites.

The Redkino, Kotlin and Rovno regional stages have been substantiated in the type area of the Vendian on the basis of the abundant organic-walled microfossils, megascopic algae, metazoan body fossils and ichnofossils.

The lower boundary of the Vendian could have a biostratigraphic substantiation as well taking into consideration the worldwide occurrence of the Pertatataka assemblage of giant acanthomorph acritarchs.

Beiyixi glaciaton
The Beiyixi is later than 755 Ma.

Tonian
The Tonian is the first geologic period of the Neoproterozoic Era, from 1000 to 720 Mya, defined by the International Commission on Stratigraphy (ICS) based on radiometric chronometry. The Tonian is preceded by the Stenian Period of the Mesoproterozoic era and followed by the Cryogenian.

The Tonian spans 1000 to 850 Ma.

Def. "a geologic period within the Neoproterozoic era from about 1000 to 850 million years ago" is called the Tonian.

"Re-Os age constraints place the negative isotope excursion preceding the Sturtian glaciation (Islay anomaly) between 739 ± 6 Ma and 732 ± 4 Ma, that is, >15 m.y. before the first diamictites (Rooney et al., 2014; Strauss et al., 2014)."

The "upper ~1 km of the Tambien Group [...] begins with the Didikama Formation—extensively dolomitized and recrystallized pale-brown carbonates interbedded with siltstones. This transitions into well-preserved limestone ribbonite (micrite with ribbon-like laminations) with molar tooth structures of the Matheos Formation. Carbonates near the contact between these two formations record a large negative 𝛅 excursion to values below -6‰ that was tentatively correlated with the Islay anomaly (Swanson-Hysell et al., 2015) [...]. The ribbonites that record the recovery from the negative anomaly transition into the upper Matheos Formation, which is dominated by oolitic grainstones with abundant molar tooth structures. Dolomitized stromatolites and minor fine-grained siliciclastics serve as a distinctive and consistent marker for the base of the overlying Mariam Bohkahko Formation."

"The Islay anomaly is a sharp negative 𝛅 excursion with a nadir below -6‰ recognized to precede the Sturtian glaciation (Hoffman et al., 2012). The anomaly currently is bracketed stratigraphically by two Re-Os isochron ages of 732.2 ± 4.7 Ma and 739.9 ± 6.1 Ma (2V errors with all external uncertainties) from Laurentia (Rooney et al., 2014; Strauss et al., 2014). These constraints suggest that the Islay anomaly precedes the Sturtian glaciation by >15 m.y., which negates direct causative links between the 𝛅 excursion and the initiation of Snowball Earth events (Hoffman et al., 1998; Schrag et al., 2002; Pavlov et al., 2003; Rothman et al., 2003; Tziperman et al., 2011)."

"A couplet of crystal-rich tuffs, 4 and 8 cm thick, and separated by 7 cm, were collected as a single sample (T46–102_2Z) just above the contact between the Didikama and Matheos Formations. The tuffs are within the recovery from the Islay anomaly, as they are 2 m above 𝛅 values of -4‰, and within carbonates with 𝛅 values of ~0‰. Zircons separated from the sample were translucent and euhedral. Dates from these zircons were confined to between 738 and 735 Ma, indicating a lack of detrital zircon input. The weighted mean date for the sample, 735.25 ± 0.25/0.88 Ma (2V; without/with external uncertainties), is within uncertainty of the Re-Os isochron dates of 732.2 ± 4.7 Ma and 739.9 ± 6.1 Ma (2V; including external uncertainties) that are interpreted to bracket the Islay anomaly (Rooney et al., 2014; Strauss et al., 2014). Independent Re-Os and U-Pb age constraints now indicate that the deeply negative Islay isotope anomaly is globally synchronous and precedes the Sturtian glaciation by ~18 m.y. The integrated chemostratigraphy and geochronology now confirm that the Tambien basin uniquely records a prolonged 𝛅 +5‰ plateau preserved in the Matheos and lower most Mariam Bohkahko Formations, followed by less positive values (~+2‰), prior to deposition of the first diamictites [...]."

The first putative metazoans (animal) fossils dated to the late Tonian (ca 800 Mya), e.g. Otavia antiqua, which has been described as a sponge which is consistent with molecular data recovered through genetic studies on modern metazoan species; more recent studies have concluded that the base of the animal phylogenetic tree is in the Tonian.

Karatau
The Karatau spans 1100 to 800 Ma.

Stenian
The Stenian Period is the final geologic period in the Mesoproterozoic Era and lasted from 1200 Mya to 1000 Mya (million years ago) defined chronometrically. The name derives from narrow polymetamorphic belts formed over this period.

Fossils of the oldest known sexually reproducing organism, Bangiomorpha pubescens, a red alga, first appeared in the Stenian.

Ectasian
"The Ectasian [1,400-1,200 Ma] is the second period of the Mesoproterozoic Era, occuring after the Calymmian, and before the Stenian."

"Acritarchs (unidentified organic-walled microfossils of possible fungal, algal or other origins) appear in the fossil record."

Acritarchs were originally defined as non-acid soluble (i.e. non-carbonate, non-siliceous) organic-walled microfossils consisting of a central cavity, and whose biological affinities cannot be determined with certainty.

It is likely that most acritarch species from the Paleozoic represent various stages of the life cycle of algae that were ancestral to the dinoflagellates.

Calymmian
The Calymmian Period is the first geologic period in the Mesoproterozoic Era and lasted from 1600 Mya to 1400 Mya (million years ago), defined chronometrically.

"During the Calymmian Period, oxygen built up above 10 % in the atmosphere and photosynthetic organisms grew rapidly. Eukaryotic cells appeared during this period, about 1,500 million years ago."

Statherian
The Statherian Period is the final geologic period in the Paleoproterozoic Era and lasted from 1800 Mya to 1600 Mya (million years ago), defined chronometrically.

Rafatazmia, controversially claimed to be present in Statherian beds in India, may be the oldest known confirmably eukaryotic fossil organism.

The diversification of crown group eukaryotic macroorganisms seems to have started about 1.6–1 Gya, seemingly coinciding with an increase in key nutrient concentrations. According to phylogenetic analysis, plants diverged from animals and fungi about 1.6 Gya; animals and fungi about 1.5 Gya; Bilaterians and cnidarians (animals respectively with and without bilateral symmetry) about 1.3 Gya; sponges 1.35 Gya; and Ascomycota and Basidiomycota (the two divisions of the fungus subkingdom Dikarya) 0.97 Gya. The earliest known red algae [Ramathallus] mats date to 1.6 Gya. The earliest known fungus dates to 1.01–0.89 Gya from Northern Canada. Multicellular eukaryotes, thought to be the descendants of colonial unicellular aggregates, had probably evolved about 2–1.4 Gya. Likewise, early multicellular eukaryotes likely mainly aggregated into stromatolite mats.

Orosirian
"Prokaryotic micro-fossils [occur] in the carbonaceous shale of Gwalior basin" dated to 2000 Ma (Orosirian Period).

The Orosirian Period is the third geologic period in the Paleoproterozoic Era and lasted from 2050 Mya to 1800 Mya (million years ago).

Rhyacian
The Francevillian biota (also known as Gabon macrofossils or Gabonionta) is a group of 2.1-billion-year-old Palaeoproterozoic, macroscopic organisms known from fossils found in Gabon in the Palaeoproterozoic Francevillian B Formation, a black shale province. The fossils are postulated to be evidence of the earliest form of multicellular life. While the fossils have yet to be assigned to a formal taxonomic position, they have been informally and collectively referred to as the "Gabonionta" by the Natural History Museum Vienna in 2014.

The fossil organisms are up to 17 cm in size. Their bodies were flattened disks with a characteristic morphology, including circular and elongated individuals and a spherical to ellipsoidal central body bounded by radial structures shows three-dimensionality and coordinated growth. Cell-cell communication must be assumed as it existed before multi-cellularity arose.

The Rhyacian Period is the second geologic period in the Paleoproterozoic Era and lasted from 2300 Mya to 2050 Mya Mya (million years ago), defined chronometrically.

Makganyene glaciation
"Cyanobacteria appear to have evolved in the short interval between the Huronian glaciations and the Makganyene glaciation."

The "production of large quantities of free O2 was triggered by the evolution of oxygenic photosynthesis. We suggest the oldest strong geological evidence for O2 is the 2.22 Ga Kalahari Mn member of the Hotazel BIF (1), as in the oceans only free O2 can oxidize soluble Mn(II) into insoluble Mn(IV)."

The "oxygenation event seems to correlate with the Makganyene glaciation, at 2.22 Ga (6). The appearance of red beds in the Upper Timeball Hill formation directly underlying the Makganyene diamictite supports this interpretation."

Huronian ice age
"The Gordon Lake Formation of the Paleoproterozoic Huronian Supergroup is a primarily- siliciclastic succession ranging from 300 to 1100 m thick. Lithostratigraphic and sedimentological analysis of the formation in the Bruce Mines and Flack Lake areas, and Killarney and Lady Evelyn-Smoothwater provincial parks revealed 7 lithofacies, which comprise 3 distinct lithofacies associations. The lithofacies associations are subtidal nearshore, subtidal to shallow shelf, and mixed intertidal flat. Microbially-induced sedimentary structures (MISS) related to microbial mat destruction and decay were recognized in the Flack Lake area. The preserved MISS include sand cracks, mat chips, remnant gas domes, and pyrite patches, and iron laminae. A biological origin for the fossil structures is supported by their similarities to modern and ancient documented examples of MISS, the sand-dominated nature of the substrate in which they are preserved, and key microtextures identified in thin section. The identified MISS support the interpretation of a tidal flat depositional environment."

Grypania is an early, tube-shaped fossil from the Proterozoic eon, with a size over one centimeter and consistent form, could have been a giant bacterium, a bacterial colony, or a eukaryotic alga. The oldest probable Grypania fossils date to about 2300 million years ago (redated from the previous 1870 million) and the youngest extended into the Ediacaran period.

Gowganda glaciation
The Huronian Ice Age is known "mainly from Canada and the United States in North America, where dated rocks range from 2500 to 2100 million years old. The Gowgonda Formation of Ontario is especially noteworthy for its excellent preservation of glaciogenic strata dated about 2300 million years old. Other glacial deposits are found in Wyoming, Michigan, Quebec, and the Northwest Territories. These rocks record extensive Early Proterozoic continental glaciation through a time span of about 400 million years, during which three or more glacial expansions took place. The configuration of the continents during this time is highly speculative."

Grypania is an early, tube-shaped fossil from the Proterozoic eon, with a size over one centimeter and consistent form, could have been a giant bacterium, a bacterial colony, or a eukaryotic alga. The oldest probable Grypania fossils date to about 2300 million years ago (redated from the previous 1870 million) and the youngest extended into the Ediacaran period.

Bruce glaciation
"The second Huronian glaciation is represented by the Bruce diamictite and is correlated with the Vagner diamictite in the Snowy Pass Supergroup (Wyoming) [49]."

"Sandstones and arkoses of the Mississagi Fm. are succeeded by the glacially derived Bruce Fm., which contains dropstones [26] and is immediately overlain by a carbonate with carbon isotope characteristics that broadly resemble those described for Neoproterozoic cap carbonates [17]. Sedimentary rocks of the post-glacial Espanola Fm. constitute a transition from a lower carbonate–limestone member to a higher siltstone-heterolithic member, which is interpreted to have formed in a shallow-marine or restricted lacustrine environment possibly during a period of active continental fragmentation [15,27–29]. Rare columnar stromatolite features have also been reported in the Espanola carbonate [30]."

Ramsey Lake glaciation
"The glacial diamictite of the Ramsey Lake Formation [...] contains dropstones in siltstone interbeds, implies deposition in a glaciomarine setting at an ice margin."

"A recent study of the organic geochemistry of the pre-glacial Matinenda Fm. has documented oil droplets with relatively high levels of 2α-methylhopanes and other biomarkers interpreted to be eukaryotic in origin [22]. It was also suggested that the oil probably migrated in the Matinenda Fm. from the McKim Fm. [which underlays the Ramsey Lake Formation] during post-depositional processes and consider unlikely the possibility that these cyanobacterial biomarkers are indigenous to the Matinenda Fm."

Siderian
The Siderian Period, meaning "iron" period) is the first geologic period in the Paleoproterozoic Era and lasting from 2500 Ma to 2300 Ma (million years ago), based on dates defined chronometrically.

The deposition of banded iron formations, peaking early in this period, were formed as anaerobic cyanobacteria produced waste oxygen that combined with iron, forming magnetite (Fe3O4, an iron oxide), removing iron from the Earth's oceans, presumably turning greenish seas clear, with no remaining iron in the oceans to serve as an oxygen sink, the process allowed the buildup of an oxygen-rich atmosphere, with the second, follow-on event known as the oxygen catastrophe, possibly triggering the Huronian glaciation.

Neoarchean
Def. "a geologic era within the Archaean eon from about 2800 to 2500 million years ago" or the "era from 2,800 Ma to 2,500 Ma" is called a Neoarchean.

Biomarkers of cyanobacteria discovered c. 2,700 Ma, together with steranes (sterols of cholesterol), associated with films of eukaryotes, in shales located beneath banded iron formation hematite beds, in Hamersley Range, Western Australia; skewed sulfur isotope ratios found in pyrites show a small rise in oxygen concentration in the atmosphere; Sturgeon Lake Caldera forms in Wabigoon greenstone belt – contains well preserved homoclinal chain of greenschist facies, metamorphosed intrusive, volcanic and sedimentary layers (Mattabi pyroclastic flow considered third most voluminous eruptive event); stromatolites of Bulawayo series in Zimbabwe form – first verified reef community on Earth.

Mesoarchean
Def. "a geologic era within the Archaean eon from about 3200 to 2800 million years ago; stromatolites have existed from this time" or the "era from 3,200 Ma to 2,800 Ma" is called the Mesoarchean.

The earliest reefs date from this era, and were probably formed by stromatolites.

Paleoarchean
Def. "a geologic era within the Archaean eon from about 3600 to 3200 million years ago; the first aerobic bacteria appeared at this time" or the "era from 3,600 Ma to 3,200 Ma" is called the Paleoarchean.

The earliest known life forms on Earth are putative fossilized microorganisms found in hydrothermal vent precipitates, considered to be about 3.42 billion years old.

The earliest direct evidence of life on Earth are microfossils of microorganisms permineralized in 3.465-billion-year-old Australian Apex chert rocks.

Eoarchean
Def. "a geologic era within the Archaean eon from about 4600 to 3600 million years ago; the first single-celled life began at this time" or the "era from 4,000 Ma to 3,600 Ma" is called the Eoarchean.

"Some graphite contained in the 3.7-billion-year-old metasedimentary rocks of the Isua Supracrustal Belt, Western Greenland1, is depleted in and has been interpreted as evidence for early life2. However, it is unclear whether this graphite is primary, or was precipitated from metamorphic or igneous fluids3,4. Here we analyse the geochemistry and structure of the -depleted graphite in the Isua schists. Raman spectroscopy and geochemical analyses indicate that the schists are formed from clastic marine sediments that contained -depleted carbon at the time of their deposition. Transmission electron microscope observations show that graphite in the schist occurs as nanoscale polygonal and tube-like grains, in contrast to abiotic graphite in carbonate veins that exhibits a flaky morphology. Furthermore, the graphite grains in the schist contain distorted crystal structures and disordered stacking of sheets of graphene. The observed morphologies are consistent with pyrolysation and pressurization of structurally heterogeneous organic compounds during metamorphism. We thus conclude that the graphite contained in the Isua metasediments represents traces of early life that flourished in the oceans at least 3.7 billion years ago." And, possible stromatolites  were discovered in 3.7 billion-year-old metasedimentary rocks in southwestern Greenland.

The earliest time that life forms first appeared on Earth is at least 3.77 billion years ago. Possibly they existed as early as 4.28 billion years.

In 2008, another rock formation was discovered in the Nuvvuagittuq greenstone belt in northern Québec, Canada which has been dated to be.

Hadean
Def. "the geologic eon from about 4,600 to 3,800 million years ago; marked by the formation of the solar system, a stable Earth-Moon orbit and the first rocks" or the "eon before 4,000 Ma" is called the Hadean.

Potential "biotic material, remains of life" were found in 4.1 billion-year-old rocks in Western Australia and described in a 2015 study.

In March 2017, fossilized microorganisms (microfossils) were announced to have been discovered in hydrothermal vent precipitates from an ancient sea-bed in the Nuvvuagittuq Greenstone Belt of Quebec, Canada. These may be as old as 4.28 billion years, the oldest evidence of life on Earth, suggesting "an almost instantaneous emergence of life" after ocean formation 4.41 billion years ago.

The earliest time that life forms first appeared on Earth is even 4.41 billion years —not long after the oceans formed 4.5 billion years ago, and after the formation of the Earth 4.54 billion years ago.

Hypotheses

 * 1) To obtain index fossils in locations where exposures do not occur, corings may provide alternatives.