Biostratigraphy

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biostratigraphy

[¦bī·ō·strə′tig·rə·fē]
(paleontology)
A part of paleontology concerned with the study of the conditions and deposition order of sedimentary rocks.

Biostratigraphy

 

a branch of stratigraphy which studies the distribution of fossil remains of organisms in sedimentary deposits with the object of determining the relative age and the correlations between layers of the same age in different territories. The task of biostratigraphy is the elaboration of scales of the relative age of layers (in various degrees of detail and of various scopes, but in zonal layers in particular). The succession of biostratigraphic zones reflects the change in geological cross section of fossil remains from a group of extinct organisms of different taxonomic classes or their systems. Of special importance in the differentiation of zones, and above all of biozones, are groups of extinct organisms that had relatively short life-spans but that attained widespread distribution, significant abundance, and variety (for example, nummulites, graptolites, and dinosaurs). Zones are frequently based on stages in the evolution of certain rapidly changing groups of extinct organisms (for example, corals of the subclass Rugosa). The study of the remains of ancient microscopic organisms (micropaleontology), the quantity of which can be extremely large even in small specimens (for example, from deep chinks), is important for the goals of biostratigraphy. Remnants of planktonic organisms (foraminifers, algae, and others) that were carried for great distances by currents allow zones of great territorial expanse to be distinguished. Fossil remains of plant spores and pollen, which were carried for great distances by the wind, are important for correlating deposits of maritime or continental origin that are of the same age. Biostratigraphy makes broad use of the methods of paleoecology for reconstructing the conditions under which ancient organisms existed in order to distinguish complexes of organisms of the same age living in different conditions from complexes of organism of different ages living in similar conditions.

REFERENCES

Menner, V. V. “Biostratigraficheskie osnovy sopostavleniia morskikh, lagunnykh i kontinental’nykh svit.” Tr. geologicheskogo instituta AN SSSR, 1962, issue 65.
Stratigraficheskaia klassifikalsiia, terminologiia i nomenklatura. Leningrad, 1965.
Stepanov, D. L. Printsipy i metody biostratigraficheskikh issledovanii. Leningrad, 1958.

R. L. MERKLIN

References in periodicals archive ?
The latest Ordovician is biostratigraphically dated in the westernmost Baltic section (drill core S-7; Ulst 1992), where strata with some Hirnantia brachiopods are overlain by graptolite-bearing rocks, most likely of the Normalograptus extraordinarius Zone (Fig.
Later, Dufka (1992) discovered the abundant occurrence of the biostratigraphically significant chitinozoan Margachitina margaritana.
Most are biostratigraphically based, but other criteria have been used, such as the iridium spike at the base Cenozoic, the carbon isotope anomaly at the base of the Eocene, and a specific Milankovitch cycle at the base of the Pleistocene.
Regardless of the small thickness of the Leetse Formation in the Saka section, its sequence is biostratigraphically the most complete on the North Estonian Klint.
The age of the Woodbine Formation was established biostratigraphically by Kennedy and Cobban (1990) using ammonites from marine members in the lower part of the formation.
Some of these sites reflect a Rancholabrean age based on presence of Bison, while others cannot be biostratigraphically assigned.
Outliers of Westphalian Cumberland Group rocks are found locally in the western Cobequid Highlands between Port Greville and Cape Chignecto, including an area identified by Donohoe and Wallace (1982) at De Wolfe Brook, where the rocks lithologically and biostratigraphically correlate with the Polly Brook Formation of Ryan et al.
Meanwhile, this group of microphytoplankton has been proven to be biostratigraphically useful and may appear particularly useful for interregional correlations, while most of the other fossil groups in Siberia exhibit rather a high degree of endemism.
Lower-middle Llandovery sections of three drill cores (Poltsamaa, Heimtali, and Ikla) were biostratigraphically correlated by means of chitinozoans and conodonts.
Except in the northeasternmost part of the Prague Syncline (including the Prague-Repy section), the black shale succession was interrupted by a hiatus (rather a long-term omission of sedimentation) in the upper part of the Parakidograptus acuminatus Biozone (Storch 2006) which resulted in a biostratigraphically dated paraconformity in most of the sections (including the Hlasna Treban and Radotin tunnel sections).