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CSPG Special Publications

Abstract


Intl. Symposium of the Devonian system: Papers, Volume II, 1967
Pages 777-787
Palaeontology

Late Silurian and Early Devonian Trilobites of Central Kazakhstan

Z. A. Maximova

Abstract

Central Kazakhstan is of great interest as a region which, in Late Silurian and Early Devonian, was a route for faunal migration between the Atlantic and Pacific realms.

In this region the Upper Silurian and Lower Devonian are represented by marine terrigenous deposits containing numerous faunal remains, among which more than 70 species of trilobites have been discriminated. Although endemic forms are predominant, about 20 percent of the species are analogous or close to west European ones (Barrandian, Harz) and about 30 per cent are close to known species from North America (New York, Appalachians).

The Late Silurian trilobites of Central Kazakhstan have many features in common with trilobites of the Ludlovian and of the Barrandian (Phacops fecundus orientalis Z. Max., Cheirurus quenstedti orientalis Z. Max., etc.).

In the first half of the Early Devonian (Pribalkhash horizon), the trilobites of Kazakhstan show a close resemblance to the trilobites found in the Helderbergian of North America (Phacops logani balchashensis Z. Max., Phacops saryarkensis Z. Max., etc.)

The trilobites of the later half of the Early Devonian permit a firm correlation of the Sarzhal’sky horizon with the Pragian, (Phacops cephalotes Hawle et Corda, Crotalocephalus hexaspinus Z. Max. of the C. group, etc.). At the same time, the abundance of trilobite species close to those described from the Devonian of North America (Phacops cristata Hall group, the subgenus Crassiproetus Stumm, the genus Dechenellurus Z. Max., etc.) allows a correlation with the Oriskany, Schoharie and Lower Onondaga beds. Since, however, this comparison is based upon similarities rather than identities, a relatively detailed correlation is difficult. We may suppose that trilobites of this type appeared in the Early Devonian of Kazakhstan and later migrated to the east through the regions of Altai, Mongolian Altai, Transbaikal and the Far East, because their remains are observed in North America in higher deposits than the analogues of the Pragian stage.


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