gssp

Global Stratotype Section & Point (GSSP)

Mubashir Khan

01-161122-019

Bs Geology-6

Submitted to:

Sir

Bahria University (Islamabad Campus) Department of Earth and Environmental Sciences

TABLE OF CONTENTS :

1. INTRODUCTION………………………………………………………………………………………………02-05

1.1 Global Stratotype Section & Point (GSSP)

1.1 Back ground

1.2 Definitions

1.3 Requirements for the selection of boundary stratotypes of chronostratigraphic units:

2. EXAMPLES…………………………………………………….………………………05-09

2.1 The Global Stratotype Section and Point (GSSP) for the boundary between the Capitanian and Wuchiapingian Stage (Permian).

2.2 The Global Stratotype Section and Point (GSSP) of the Induan/Olenekian Boundary (Early Triassic): (Nammal Nala (Salt Range, Pakistan).

2.3 The Global Stratotype Section and Point (GSSP) of the Permian-Triassic Boundary.

3. References……………………………………………………………….........................10

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Global Stratotype Section & Point (GSSP):

1.1Background:For most of the nineteenth century and first two-third of the twentieth century, the standard geologic time unit of the Phanerozoic Eons (periods, epochs, and ages) was generally conceptualized in different ways. Many workers have contributed to the present status of the GSSP concept, but there can be little doubt that the efforts of hollis D. Hedberg were primarily responsible for the eventual acceptance of stratotype based, permanent , internationally-accepted definition for the standard global geochronological /chronostraitatigraphic unit of the Phenerozoic time scale. Nevertheless, Hedberg had predecessors, and Harland (1978, p. 22) and Vai (2001) noted that embryonic concept of the GSSP can be found in some early straitigraphic discussion. Some fairly modern general views on defining a standard Global time scale were discussed in the text book of Grabau (1924, pp. 1100-1101).

1.2 Definitions:

1.2.1 Standard definitions:

Named stratigraphic units must be defined or characterized at a specified locality where they are well exposed and developed in order that there will be a common, material standard of reference for their identification.

1.2.2 Reference to a specific rock section:

The particular sequence of strata chosen as a standard of reference of a layered stratigraphic unit is called a stratotype. In the case of non layered rocks the standard of reference is a type locality. It may be an area of exposure (or well or mine) and is an essential part of the establishment of a formal stratigraphic unit. In cases where the written description and the stratotype are not the same, the data from the stratotype take precedence.

For some stratigraphic units, such as biostratigraphic range zones, the standard of the unit cannot be tied to a specific stratigraphic section or area because the stratigraphic scope of the unit may vary with increasing information. However, the characterization and description of these and other biostratigraphic units can be enhanced by the designation of one or more specific reference sections.

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1.2.3 Stratotype (type section):

The designated exposure of a named layered stratigraphic unit or of a stratigraphic boundary that serves as the standard of reference. A stratotype is the specific strata sequence used for the definition and/or characterization of the stratigraphic unit or boundary being defined.

1.2.4 Unit stratotype:

The type section of a layered stratigraphic unit that serves as the standard of reference for the definition and characterization of the unit .

1.2.5 Boundary Stratotype:

The specified sequence of strata that contains the specific point that defines a boundary between two stratigraphic units.

1.2.6 Composite Stratotype:

A unit stratotype formed by the combination of several specified intervals of strata combined to make a composite standard of reference.

1.2.7 Type Locality:

The specific geographic locality was the stratotype of a layered stratigraphic unit is situated. The name also refers to the locality where the unit was originally described and/or named. In the case of units composed of non layered igneous or metamorphic rocks, the type locality is the specific geographic locality where the unit was originally defined.

1.2.8 Type Area or Type Region:

The geographic area or region that encompasses the stratotype or type locality of a stratigraphic unit or boundary.

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1.3 Requirements for the selection of boundary stratotypes of chronostratigraphic units:

Chronostratigraphic units offer the best promise of being identified, accepted, and used globally and of being, therefore, the basis for international communication and understanding because they are defined on the basis of their time of formation, a universal property. Particularly important in this respect are the units of the Standard Global Chronostratigraphic (Geochronologic) Scale. The term "Global Boundary Stratotype Section and Point" (GSSP) has been proposed for the standard boundary-stratotypes of the units of this scale.

In addition to the general requirements for the selection and description of stratotypes, boundary stratotypes of chronostratigraphic units should fulfill the following requirements:

1. The boundary stratotypes must be selected in sections representing essentially continuous deposition. The worst possible choice for a boundary-stratotype of a chronostratigraphic unit is at an unconformity.

2. The boundary-stratotypes of Standard Global Chronostratigraphic Units should be in marine, fossiliferous sections without major vertical lithofacies or biofacies changes. Boundary stratotypes of chronostratigraphic units of local application may need to be in a non marine section.

3. The fossil content should be abundant, distinctive, well preserved, and represent a fauna and/or flora as cosmopolitan and as diverse as possible.

4. The section should be well exposed and in an area of minimal structural deformation or surficial disturbance, metamorphism and diagenetic alteration, and with ample thickness of strata below, above and laterally from the selected boundary-stratotype.

5. Boundary stratotypes of the units of the Standard Global Chronostratigraphic Scale should be selected in easily accessible sections that offer reasonable assurance of free study, collection, and long-range preservation. Permanent field markers are desirable.

6. the selected section should be well studied and collected and the results of the investigations published, and the fossils collected from the section securely stored and easily accessible for study in a permanent facility.

7. The selection of the boundary stratotype, where possible, should take account of historical priority and usage and should approximate traditional boundaries.

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8. To insure its acceptance and use in the Earth sciences, a boundary stratotype should be selected to contain as many specific marker horizons or other attributes favorable for long-distance time correlation as possible.

The IUGS International Commission on Stratigraphy is the body responsible for coordinating the selection and approval of GSSPs of the units of the Standard Global Chronostratigraphic (Geochronologic) Scale.

EXAMPLES:

2.1 The Global Stratotype Section and Point (GSSP) for the boundary between the Capitanian and Wuchiapingian Stage (Permian):

The Global Stratotype Section and Point (GSSP) for the boundary between the Capitanian and Wuchiapingian stages, also the boundary between the Guadalupian and Lopingian Series is defined at the First Appearance Datum (FAD) of the conodont Clarkina postbitteri postbitteri at the base of Bed 6k in the Penglaitan Section along the Hongshui River in Guangxi Province, South China. This point is within a chronomorphocline from Clarkina postbitteri hongshuiensis to C. dukouensis and nearly coincides with the Middle-Upper Absaroka Megasequence boundary and as such is documented within a continuously deposited carbonate lowstand succession with deep-water facies of the Maokou Formation below and deep-water facies of the Heshan For- mation above. Furthermore, this point also coincides with a major extinction of various Permian fossils including corals, fusulinaceans, ammonoids and brachiopods. The proximity to an apparently global major sequence boundary and extinction event will serve as a means of correlation of this GSSP into other regions in which the defining taxon is not present because of pro- found provincialism during the

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Middle and Upper Permian. Carbon isotopic trends and magnetostratigraphic signatures are also provided to help correlate this GSSP into other regions, including those with continental facies successions. The Tieqiao Section near the county town of Laibin is also described as a supplementary reference section.

The Global Stratotype Section and Point (GSSP) for the basal boundary of the Wuchiapingian Stage has been defined at the first occurrence of the conodont Clarkina postbitteri postbitteri Mei and Wardlaw (in Mei et al., 1994a) at the base of Bed 6k of the Penglaitan Section.

In Pakistan:

Capitanian-Wuchiapingian (C/W) boundary successions were also reported from the Salt Range, Pakistan. Loping an strata is in part related to recognizing a distinct post- Guadalupian depositional sequence because the boundary level falls within an interval represented by one of the lowest stands of sea-level in the Phanerozoic. Among the chemostratigraphic fluctuations, a substantial negative shift of carbon isotopic values occurring near the G/L boundary may serve as a distinct marker (Wang et al., 2004; Kaiho etal, 2005). It has been traced around the boundary between Members 3 and 4a in the Salt Range, Pakistan (Baud et al., 1995), which is below the Clarkina dukouensis Zone (Wardlaw and Mei, 1999).

. Since the upper part of the Wargal Formation is dominated by reversed polarity in the Salt Range, Pakistan, it is reasonable to refer to this interval as part of a reversed polarity zone (Haag et al., 1991). The lower boundary of this polarity zone is below the occurrence of the conodont Clarkina dukouensis and thus, it correlates with the Early Wuchiapingian (Wardlaw and Mei, 1998). The GSSP for the C/W boundary is marked by excellent exposures, continuous deposition, diverse and abundant fossils, favorable open marine facies for long distance correlation, and chemostratigraphic signatures. It has not been subjected to major tectonic disturbances or strong diagenetic alteration and it is free from vertical facies changes and accessible. It meets all basic GSSP requirements.

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2.2 The Global Stratotype Section and Point (GSSP) of the Induan/Olenekian Boundary (Early Triassic): (Nammal Nala (Salt Range, Pakistan) :

Here we present detailed biostratigraphical results based on new collections of ammonoids and conodonts from Nammal Nala (Salt Range, Pakistan), a classical locality for Early Triassic ammonoids, which had never been studied in detail. Our results show that this section provides by far the most complete profile for the definition of the Induan-Olenekian boundary (IOB). The GSSP’s golden spike for the base of the Olenekian could be located at the first occurrence of Flemingitidae (a typical Smithian ammonoid family) and of the conodont genus Novispathodus. It also coincides with a positive shift of δ13 Corg of ca. 6‰, with a sequence boundary and with a palynofacies change (Hermann et al., 2011). In this expanded stratigraphical series the IOB falls within the Ceratite Marls without any significant facies change, an ideal configuration for the definition of a boundary. The same sequence of faunal associations had previously been recognized in Mud (Spiti Valley, India; Brühwiler et al. 2010), another GSSP candidate for this boundary proposed by Krystyn et al. (2007a, b). Here, the faunal turnover occurs 1 m below the previously proposed IOB (in bed 10 instead of bed 13 of Krystyn et al. 2007a, b; Brühwiler et al. 2010), and is associated with a facies change (from dark shales with early diagenetic calcareous concretions to massive, bioturbated limestone beds) in a much more condensed section. Moreover, it has undergone strong diagenetic alteration, so no palyno- logical record is available. Conodonts also allow detailed correlation with the section of Chaohu (SE China).

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2.3 The Global Stratotype Section and Point (GSSP) of the Permian-Triassic Boundary:

The Permian-Triassic Boundary Working Group (PTBWG) was established in 1981 by the International Commission on Stratigraphy (ICS) under the leadership of T. Tozer. Until 1984, the ammonoid Otoceras was considered as the index fossil of the Permian-Triassic boundary (PTB). In 1986, Hindeodus parvus was proposed to substitute Otoceras as the boundary marker (Yin et al., 1986), which later obtained the majority approval of PTBWG. The Chinese Working Group on PTB sug- gested the base of Hindeodus parvus horizon, Bed 27c of Meishan section, Changxing County in Zhejiang Province of South China as the GSSP of PTB. During a workshop at Calgary meeting (1993), the PTBWG proposed four candidates for the stratotype of this boundary, i.e., Meishan of Zhejiang, Guryul Ravine of Kash- mir, Shangsi of Sichuan, and Selong of Tibet. In the later years search for adequate index fossils at the Shangsi section has not led to valuable discovery. Fruitful teamwork in Selong (Jin et al., 1996; Orchard et al, 1994) revealed, however, the conspicuous hiatus right below the boundary and the uncertainty of the existence of Changhsingian Stage of this section. Work at Guryul Ravine was blocked by the unstable political condition in Kashmir. Although important achievements have been made in other sections of the world, at Gartnerkofel of the Alps, in Arctic Canada and Spiti region of the Himalayas, generally they are still below the standard required by the ICS Guidelines, and no substitute proposal for GSSP of PTB have been made. Meanwhile, works on the Meishan section have been vigorously carried out to satisfy the GSSP requirements. Naturally Meishan became the sole candidate for the GSSP of PTB. In 1996 nine members of PTBWG published a formal

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recommendation to set the Permian-Triassic boundary at the first appearance of Hindeodus parvus, Bed 27c of Meishan (Yin et al., 1996). This paper later served as the draft for a formal submission of the PTBWG for ballot. On September 18, 1999, the official Chinese Xinhua Daily Dispatch declared a list of localities, including Changxing County, that were ratified to be opened to foreigners by the State Council of China, and quoted: "The spokesman of the Ministry of Public Security announced that according to the 'Foreigner entry and exit law of the People's Republic of China', no travel permits are required for foreigners with valid visas or residential identifications to travel in the above areas." Thus the Meishan section meets the ICS requirement of authorized accessibility for a GSSP. From 1999 to 2000, the proposal for Meishan as the GSSP of PTB passed three runs of ballot. The results are as follows: (1) Vote by PTBWG (October 1999 to January 2000): voting members, 26; votes received, 23 (88%); yes, 20 (87%); no, 3; (2) Vote by the Sub commission on Triassic Stratigraphy (April to June, 2000): voting members, 31; votes received, 27 (87%); yes, 22 (81%); no, 2; abstention, 2; yes for Meishan as GSS, but at different Point, 1; (3) Vote by ICS (September to November, 2000): voting members, 18; votes received, 17 (94.4%); yes, 17 (100%). The proposal was finally ratified by the IUGS Executive Committee in March, 2001. Thus, the GSSP of the Permian-Triassic Boundary is defined at the base of Bed 27c, Meishan Section D, Changxing County, Zhejiang Province, China, at the horizon where the conodont Hindeodus parvus first appeared.

In Pakistan:

Yan and Li (1987) noticed an unstable clay between the Chhidru formation and the lower unit of the Katwai Member at Nammal section of Salt Range.there is first appearance of H.Parvus at the base of the Mittiwali Member about 4m away from the base of the Middle Kathwai member(Baud et al 1985).it is based on Eventostratigraphy and chemostratigraphy Besides the earlier δ13C curves provided by Xu and Yan (1993) and other authors, new curves have been presented in Jinet al Bowling et al. (1998) and Hansen et al.(1999a). The latter two show a similar profile to previous works since in other sections of the world there is usually only one depletion, and at Nammal section of Salt Range where two depletions occur, the lower one is considered to be due to diagenetic cement (Yin, ed., 1996).

The marker of the boundry stratotype point is the appearance of Hindeodus parvus; Auxiliary marker is δ13C excursion.

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References:

1. Baud, A., Atudorei, V. and Zachary, S., 1995, The Upper Permian of the Salt Range revisited: New stable isotope dat: Permophiles, no.29, pp.39–42.

2. Pakistani-Japanese Research Group, 1985, Permian and Triassic Systems in the Salt Range and Surghar Range, Pakistan, in Nakazawa, K. and Dick-ins, J. M., eds, The Tethys, her paleogeography and paleobiogeography from Paleozoic to Mesozoic: Takai University Press, Tokyo, pp.221–312.

3. https://engineering.purdue.edu/Stratigraphy/gssp/index.php?parentid=all4. https://engineering.purdue.edu/Stratigraphy/references/Induan.pdf5. Brühwiler, T., Ware, D., Bucher, H., Krystyn, L. And Goudemand, N. 2010. New Early

Triassic ammonoid faunas from the Dienerian/Smithian boundary beds at the Induan/Olenekian GSSP candidate at Mud (Spiti, Northern India). Journal of Asian Earth Sciences, 39, 724-739.

6. Chinese Triassic Working Group 2007. Final report of the GSSP candidate for the I/O boundary at West Pingdingshan Section in Chaohu, Southeastern China. Albertiana, 36, 10-21.

7. Hermann, E., Hochuli, P. A., Méhay, S., Bucher, H., Brühwiler, T., Ware, D., Hautmann, M., Roohi, G., Ur-Rehman, K. And Yaseen, A. 2011. Organic matter and palaeoenvironmental signals during the Early Triassic biotic recovery: The Salt Range and Surghar Range records. Sedimentary Geology 234:19-41.

8. Krystyn, L., Bhargava, O. N. And Richoz, S. 2007a. A candidate GSSP for the base of the Olenekian Stage: Mud at Pin Valley; district Lahul & Spiti, Himachal Pradesh (Western Himalaya), India. Albertiana, 35, 5-29.

9. Krystyn, L., Richoz, S. And Bhargava, O. N. 2007b. The Induan-Olenekian Boundary (IOB) in Mud – an update of the candidate GSSP section M04. Albertiana, 36, 33-45.

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https://engineering.purdue.edu/Stratigraphy/references/Induan.pdf

https://engineering.purdue.edu/Stratigraphy/gssp/index.php?parentid=all


10. Yin, H., Wu, S., Ding,M., Zhang, K., Tong, J., Yang, F. and Dulong, L., 1996b, The Meishan section. Candidate of the global stratotype and point (GSSP) of the Permian-Triassic boundary (PTB), in H. Yin, (eds.), The Paleozoic-Mesozoic Boundary. Candidates of the Global Stratotype Section and Point of the Permian-Triassic Boundary: Wuhan, China University of Geosciences Press, p. 31-47.

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stratigraphic boundary

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point gssp

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standard geologic time