Late Ordovician palaeogeography and the positions of the Kazakh terranes through analysis of their brachiopod faunas

Abstract

ABSTRACT:Popov, L.E. and Cocks, L.R.M. 2017. Late Ordovician palaeogeography and the positions of the Kazakh terranes through analysis of their brachiopod faunas. Acta Geologica Polonica, 67 (3), 323-380. Warszawa.Detailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the south-western margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.

Cambrian rhynchonelliform nisusioid brachiopods: phylogeny and distribution

“…) is a sister taxon to Bellistrophia sp. from the Miaolingian (Wuliuan) of the Chingiz–Tarbagatay island arc system which, according to Popov & Cocks (), was located in low southern latitudes in proximity of western margin of Australasian Gondwana during the Cambrian (Fig. ).…”

“…Laurentia, Baltica, Gondwana and Siberia) for Cambrian, Wuliuan (e.g. Torsvik & Cocks ) with emendations for Australasian peri‐Gondwana mainly after Popov & Cocks ().…”

An Early Ordovician (late Tremadocian) bivalve fauna from Iran

“…Note that the Tremadocian (Alborz) and Floian (South Wales) occurrences are at identical latitudes. The later Yunnan fauna (Sibumasu) is at a slightly lower latitude (based on Popov, Holmer, Bassett, Ghobadi Pour, & Percival, , with major modifications; palaeogeography of Australasian peri‐Gondwana mainly after Popov & Cocks, )…”

Altaethyrella(Brachiopoda) from the Late Ordovician of the Tarim Basin, Northwest China, and its significance

“…During the Late Ordovician, the Tarim paleoplate was located approximately in tropical latitudes (e.g., Cocks and Torsvik, 2013, fig. 7; Popov and Cocks, 2017, fig. 13), although its precise location is still uncertain.…”