Geochronology/Paleozoic

This is a geochronolgy time spiral. Credit: United States Geological Survey.

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

Notations

Let

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

"The term b2 k [b2k] refers to the ice-core zero age of AD 2000; note that this is 50 years different from the zero yr for radiocarbon, which is AD 1950 [...]."^[1]

Chronostratigraphy

This is an International Chronostratigraphic Chart. Credit: K.M. Cohen, S. Finney, and P.L. Gibbard, International Commission on Stratigraphy.

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

Geochronologic time frames

Permian

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

Carboniferous

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

Pennsylvanian

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

Mississippian

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

Middle Mississippian

"This species has been consistently identified with the considerably younger, late Viséan (late Holkerian to Asbian [late Meramecian to early Chesterian]) genus Beyrichoceras Foord, 1903 (type species, Goniatites obtusus Phillips, 1836) (eg, Gordon, 1965, p. 284."^[5]

Visean

Detail of the Tournaisian/Visean boundary is arrowed in the Pengchong section. Credit: François-Xavier Devuyst, Luc Hance, Hongfei Hou, Xianghe Wu, Shugang Tian, Michel Coen, and George Sevastopulo.

"The first appearance of Eoparastaffella simplex in the lineage Eoparastaffela ovalis - Eoparastaffella simplex (foraminifers) [is] the new biostratigraphic criterion to define the base of the Viséan."^[6]

Tournaisian

"The base of the Carboniferous System, Mississippian Sub-System and Tournaisian Stage is defined at the base of Bed 89 in Trench E' at La Serre, France. It coincides with the first appearance of the conodont Siphonodella sulcata within the evolutionary lineage from Siphonodella praesulcata to Siphonodella sulcata."^[7]

Devonian

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

Famennian

The diagram shows the detailed succession of beds around the GSSP level between beds 31g and 32a. Credit: G Klapper, R Feist, R T Becker and M R House.

Photograph of the succession shows that the GSSP lies between Bed 31g and 32a. Credit: G Klapper, R Feist, R T Becker and M R House.

"The boundary for the Frasnian/Famennian Stage Global Stratotype Section and Point (GSSP) [...] is drawn [above] in a section exposed [in the second image above] near the Upper Coumiac Quarry in the southeastern Montagne Noire, France."^[8]

Silurian

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

Telychian

Current Telychian GSSP is arrowed parallel to the bedding. Credit: Jeremy R. Davies, Richard A. Waters, Stewart G. Molyneux, Mark Williams, Jan A. Zalasiewicz, Thijs R. A. Vandenbroucke & Jacques Verniers.

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

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

Aeronian

Diagram has the Rhuddanian to early Telychian sea level curves where Ⓐ marks the horizon of the Aeronian GSSP. Credit: Jeremy R. Davies, Richard A. Waters, Stewart G. Molyneux, Mark Williams, Jan A. Zalasiewicz, Thijs R. A. Vandenbroucke & Jacques Verniers.

The arrow indicates the Aeronian lower GSSP perpendicular to the bedding. Credit: Jeremy R. Davies, et al.

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

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

Ordovician

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

Actonian

Geological map of the Onny Valley section is with the sample localities. Credit: Thijs R. A. Vandenbroucke, Antonio Ancilletta, Richard A. Fortey and Jacques Verniers.

The "Onny Valley [...] is the type locality for the Actonian and Onnian substages, and a [Site of Special Scientific Interest] SSSI."^[9]

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

Sandbian

Nemagraptus gracilis, Sandbian graptolites, are from the Caparo Formation, Venezuelan Andes. Credit: J.C. Gutiérrez-Marco, D. Goldman, J. Reyes-Abril, and J. Gómez.

"The Lower Sandbian Nemagraptus gracilis Zone comprises one of the most widespread, and easily recognizable graptolite faunas in the Ordovician System. The base of the N. gracilis Zone also marks the base of the Upper Ordovician Series, and is internationally defined by the FAD of the eponymous species, with the Global Stratotype Section and Point (GSSP) located at Fågelsång in Scania, southern Sweden (Bergström et al., 2000, 2009)."^[10]

Abereiddian

Ordovician chart illustrates the main regional series, stage and substage divisions. Credit: Hüseyïn Kozlu, M. Cemal Göncüoğu, Graciela N. Sarmiento & M. Alï Gül.

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

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

Cambrian

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

Furongian

The Furongian Series includes Cambrian Stage 10, Cambrian Stage 9, and the Paibian Stage.^[11]

Stage 10

The FAD of Lotagnosthus americanus is the primary stratigraphic tool for correlation of the base for Stage 10.^[11]

Stage 9

The FAD of Agnostotes orientalis is the primary stratigraphic tool for correlation of the base for Stage 10.^[11]

Paibian

The "FAD of Glyptagnostus reticulatus [is the primary stratigraphic tool for correlation of the base] for the Paibian Stage."^[11]

Guzhangian

The image shows exposure of the GSSP for the base of the Guzhangian Stage (coinciding with the FAD of Lejopyge laevigata) in the Huaqiao Formation, Luoyixi section, Guzhang County, Hunan Province, China. Credit: Shanchi Peng, Loren E. Babcock, Jingxun Zuo, Huanling Lin, Xuejian Zhu, Xianfeng Yang, Richard A. Robison, Yuping Qi, Gabriella Bagnoli, and Yong’an Chen.

The image shows an exoskeleton of the cosmopolitan agnostoid trilobite Lejopyge laevigata. Credit: Shanchi Peng et al.

"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."^[11]

"The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Lejopyge laevigata [in the image on the left] (base of the L. laevigata Zone)."^[11]

Drumian

The "FAD of Ptychagnostus atavus [is the primary stratigraphic tool for correlation of the base (GSSP)] for the Drumian Stage".^[11]

Stage 3

The FAD of trilobites is the primary stratigraphic tool for correlation of the base for Stage 3.^[11]

Terreneuvian

The Terreneuvian Series includes Cambrian Stage 2 and the Fortunian Stage.^[11]

Fortunian

The FAD of Trichophycus pedum is the primary stratigraphic tool for correlation of the base (GSSP) for the Fortunian Stage.^[11]

Precambrian

Def.

1. "the time and geology dated before the Phanerozoic"^[12] or
2. the "eon (or supereon) and rock formations dated before 541.0±1.0 million years ago, coinciding with the first appearance of the fossils of hard-shelled animals"^[12]

is called the precambrian.

Usage notes^[12]

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

Research

Hypothesis:

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

Control groups

This is an image of a Lewis rat. Credit: Charles River Laboratories.

The findings demonstrate a statistically systematic change from the status quo or the control group.

“In the design of experiments, treatments [or special properties or characteristics] are applied to [or observed in] experimental units in the treatment group(s).^[13] In comparative experiments, members of the complementary group, the control group, receive either no treatment or a standard treatment.^[14]"^[15]

Proof of concept

Def. a “short and/or incomplete realization of a certain method or idea to demonstrate its feasibility"^[16] is called a proof of concept.

Def. evidence that demonstrates that a concept is possible is called proof of concept.

The proof-of-concept structure consists of

1. background,
2. procedures,
3. findings, and
4. interpretation.^[17]

See also

References

External links

• Global Boundary Stratotype Section and Point (GSSP) of the International Commission on Stratigraphy

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Development status: this resource is experimental in nature.

Resource type: this resource is an article.

Resource type: this resource contains a lecture or lecture notes.

Subject classification: this is a Geology resource.