On the external indicating status of zonal biochronological scales

Research subject. The possibility of creating an external biochronological scale in stratigraphy is discussed. Materials and methods. Factors that ensure the independence of the events selected for constructing a biochronological scale from the geological setting of their occurrence are analyzed. Results. A category of biochronological scales, which are constructed based on studying evolutionary changes in a certain part of the skeleton, homologous to members of a long-existing group of organisms, was distinguished. Such scales are proposed to be referred to as meronomical. The specifics of constructing meronomical scales based on the study of conodonts is discussed. The evolutionary sequence of fossil species ensures the continuity of the scale and its external indicating status, which implies the independence of the scale from the facial features of the sections compared with its help. The main features of divergence arising in the process of evolution in the competitive relationships of related species are discussed. The correspondence of the main features arising in the development of skeletal elements during the evolution of conodonts with the prediction based on the accepted model of an ensemble development of related species is shown. In particular, such features include an increase in the variability of platform elements and stabilization of the morphology of ramiform elements, as well as a directed change in Pa elements, which serves as the basis for constructing conodont meronomical scales. The evolutionary morphological trend of the Pa element, which arises in the process of competitive relations between related species, does not depend on the particular external abiotic conditions in which these relationships are carried out. Accordingly, the biochronological scale built on the basis of the evolutionary trend of the Pa element states can also be considered as external in relation to the measured geological events captured in specific sections. The facts of the brief existence and wide distribution of periodically occurring Pa element morphotypes are explained by the phenomenon of evolutionary oscillations. This phenomenon implies that, at certain time periods in spatially separated populations of related species, their gene pools change simultaneously and in a similar way. The process of a synchronous increase in the frequency of a certain trait covers isolated and semi-isolated populations of related species in an area stretching hundreds and thousands of kilometers and almost simultaneously. A similar picture can be observed in the morphological transformations of conodonts at certain stratigraphic boundaries. Although the reasons for such evolutionary oscillations are still unclear, the established fact of their synchronous manifestation in large areas excludes the dependence of related populations on the abiotic conditions of specific locations. This circumstance represents another condition that makes it possible to consider the historical morphogenesis of Pa elements observed in the process of the described ensemble evolution of related conodont species as independent of abiotic causes and determined only by internal factors. Conclusion. Biochronological scales, which are based on the stages of evolutionary changes in a certain part of the skeleton, homologous to members of a long-existing group of organisms, are largely protected from the influence of abiotic conditions and can be considered as external scales.

1. Beauchamp B., Henderson Ch. (1994) The Lower Permian Raanes, Great Bear Cape and Trappers Cove formations, Sverdrup Basin, Canadian Arktic: Stratigraphy and conodont zonation. Bull. Canad. Petrol. Geol., 42(4), 562-597.

2. Boardman D.R., Wardlaw B.R., Nestell M.K. (2009) Stratigraphy and Conodont Biostratigraphy of Uppermost Carboniferous and Lower Permian from North American Midcontinent. Kansas Geol. Survey. Bull., 255, 42.

3. Chernykh V.V. (1986) The problem of the integrity of highest taxons. Moscow, Nauka Publ., 143 p. (In Russ.)

4. Chernykh V.V. (2005) Zonal method in biostratigraphy. Zonal scale of the Lower Permian of the Urals by the conodonts. Ekaterinburg, IGG UrO RAN, 217 p. (In Russ.)

5. Chernykh V.V. (2008) Determination of the stage boundaries of the International Stratigraphic Scale by the conodonts. Lithosphere (Russia), (1), 3-17. (In Russ.)

6. Chernykh V.V. (2016) Bases of zonal biochronology. Ekaterinburg, IGG UrO RAN, 268 p. (In Russ.)

7. Chernykh V.V. (2020) General patterns in the development of Gzhelian-Asselian conodonts. Lithosphere (Russia), 20(4), 471-485. (In Russ.)

8. Dajo R. (1975) Fundamentals of ecology. Moscow, Progress Publ., 415 p. (In Russ.)

9. Golubovskii M.D., Ivanov Yu.N., Zakharov I.K., Berg R.L. (1974) Study synchronous parallel changes of the gene pool in natural populations of fruit fly Drosophila melanogaster. Genetika, 10(4), 72-83. (In Russ.)

10. Henderson C.M., Chernykh V.V. (2021) To be or not to be Sweetognathus asymmetricus? Permophiles, 70, 10-13.

11. Henderson C.M., Schmitz M., Crowley J., Davydov V.I. (2009) Evolution and geochronology of the Sweetognathus lineage from Bolivia and the Urals of Russia: Biostratigraphic problems and implications for Global Stratotype Section and Point (GSSP) definition. Permophiles (ICOS Abstracts), 35, suppl. 1, 19.

12. Henderson Ch.M., McGugan A. (1986) Permian conodont biostratigraphy of the Ishbel Group, southwestern Alberta and southeastern British Columbia. Rocky Mountain Geol., 24(2), 219-235.

13. Larson J.A., Clark D.L. (1979) The Lower Permian (Sakmarian) Portion of the Oquirrh Formation, Utah. Conodont Biostratigraphy of the Great Basin and Rocky Mauntains. Brigham Young University Geol. Studies, 26(3), 135-142.

14. Leonov G.P. (1974) Bases of the stratigraphy. V. 2. Мoscow, MGU, 486 p. (In Russ.)

15. Mair E. (1968) Animal species and evolution. Мoscow, Mir Publ., 597 p. (In Russ.)

16. Meyen S.V. (1977) Taxonomy and meronomy. Questions of methodology in geological sciences. Kiev, Nauk. Dumka Publ., 25-33. (In Russ.)

17. Meyen S.V. (1989) Introduction to the theory of stratigraphy. Moscow, Nauka Publ., 216 p. (In Russ.)

18. Odum Yu. (1975) Fundamentals of ecology. Moscow, Mir Publ., 740 p. (In Russ.)

19. Popov A.V. (1993) Principles of stratigraphy. St.Petersburg, SPbGU, 67 p. (In Russ.)

20. Popov A.V. (2003) Measuring Geological Time: Principles of Stratigraphy and Patterns of Evolution. St.Petersburg, SPbGU, 144 p. (In Russ.)

21. Rauzer-Chernousova D.M. (1967) About zones of unified and regional scales. Izv. AN SSSR, Ser. geol., (7), 104- 118. (In Russ.)

22. Riglos Suarez M., Hunicken M.A., Merino D. (1987) Conodont biostratigraphy of the Upper Carboniferous-Lower Permian rocks of Bolivia. Conodonts: Investigative techniques and applications. (Ed. by R.L. Austin). London, British Micropalaeontological society; Ellis Horwood Publishers, 317-325.

23. Ritter S.M. (1986) Taxonomic revision and phylogeny of post-Early crisis bisselli-whitei Zone conodonts with comments on Late Paleozoic diversity. Geol. Palaeontol., 20, 139-165.

24. Shindewolf O. (1975) Stratigraphy and stratotype. Moscow, Mir Publ., 136 p. (In Russ.)

25. Sigal J. (1961) Existe-t-il plusieurs stratigraphies? BRGM France, Serv. Inform. Gеol. Bull. Trimest, 13th year, (51), 2-5.

26. Soo-In Park (1989) Microfossils of the Permo-Carboniferous Strata of Nongam Area in Mungyeong Coalfield. J. Korean Earth Sci. Soc., 10(1), 102-110.

27. Stepanov D.L. (1958) Principles and methods of biostratigraphic studies. Tr. VNIGRI, (113). Leningrad, Gostoptekhizdat Publ., 180 p. (In Russ.)

28. Wang Zhi-hao (1991) Conodonts from Carboniferous-Permian boundary strata in China with comments on the boundary. Acta Palaeontol. Sinica, 30(1), 6-41