Gondwanan faunal signatures from Early Palaeozoic terranes of Kazakhstan and Central Asia: evidence and tectonic implications

Abstract

Two separate tectonic blocks in the southwestern segment of the Kazakhstanian orogen, the Chu–Ili terrane and the Karatau–Naryn terrane (with particular attention to Malyi Karatau), are selected to illustrate their geological history and major biogeographical signatures from the Cambrian to the early Silurian. Mid- to Late Ordovician brachiopod and trilobite faunas of Chu–Ili show increased endemicity of shallow shelf assemblages, whereas distinct links to equatorial (‘east’) peri-Gondwanan are more evident in trilobite assemblages of the outer shelf. In the Late Ordovician, strong biogeographical affinities to equatorial Gondwanan faunas became firmly established and they are also traceable into the Silurian. Early Cambrian faunas of Malyi Karatau show remarkable similarity to those of South China. From the Middle Cambrian this region evolved as an isolated carbonate seamount, but until the Early Ordovician links to South China faunas were still evident. Benthic faunas from both regions show weak links to contemporaneous faunas of Baltica and little in common with Cambrian and Ordovician faunas of the Siberian craton. This suggests their location in low southern latitudes, in relative proximity to East Gondwana, which places some constraints on plate-tectonic reconstructions in relation to the southern cluster of Kazakhstanian terranes, including Karatau–Naryn, North Tien Shan and Chu–Ili.

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

“…1), are identified as the key tectonostratigraphic units for understanding the tectonic evolution and positioning of the Kazakh Orogen in the Early Palaeozoic. The Early Katian faunas of the Karatau-Naryn unit were described by Misius (1986), whose data have been reassessed by Popov et al (2009), and Popov and Cocks (2014). The Katian brachiopods of KalmykkolKokchetav are under study and some preliminary results are included here.…”

“…It was probably also the time when amalgamation of the eastern and western components of the Boshchekul Terrane occurred. In contrast, the extensive accretionary wedge in front of the Chu-Ili Terrane continued to grow throughout the Silurian and Early Devonian (Bandaletov and Palets 1980;Popov et al 2009). Şengör and Natal'in (1996) and other authors considered that the western component of the Boshchekul Terrane is a detached segment of the Chingiz-Tarbagatai island arc, but that is rather unlikely from faunal and sedimentological data.…”

“…Olenid trilobite biofacies in Early Katian black graptolitic shales at Ak-Kerme Peninsula (Nikitin et al 1980;Ghobadi Pour et al 2011, fig. 2.20); 5, Isograptid graptolite biofacies and thin pelagic layers of radiolarian cherts in distal turbidites from the 'Kusheke' Formation (Floian to Dapingian) at North Betpak-Dala (Nikitina et al 2008;Popov et al 2009); 6, Deep water limestones of the Shundy Formation (Darriwilian) with radiolarians and hexactinellide sponges (Nazarov and Popov 1980); 7, Triplococcus-dominated radiolarian assemblage and associated olenid trilobite biofacies from the Shundy Formation (Darriwilian) at Aksuran Mountain (Pouille et al 2013); 8, Radiolarian cherts and tuffites of the Taldyespe Formation with Katian conodonts and Llandovery to Wenlock conodonts and graptolites of the Egizkara Formation (Nikitin 2002;Koren et al 2003); 9, Isograptid graptolite biofacies in the Kusheke Formation (Dapingian) in Baikanur Region, 4 km south of Kuyandy Lake (Tsai 1974); 10, Isograptid graptolite biofacies in the Zorievka Formation (Dapingian) at Selety River basin (Tsai 1974); 11, Radiolarian cherts of Itmurundy, Kazyk, and Turetai formations with Darriwilian to Sandbian conodonts at Itmurundy, North Balkash Region; 12, Continuous Tremadocian to Floian sedimentary succession (Agalatas, Kendyktas and Kurdai formations) with olenide trilobite biofacies (Lisogor 1961;Popov and Holmer 1994). Metamorphic terranes: 13, Aktyuz; 14 Makbal; 15, Anrakhai…”

“…Apart from Fauna 16, the listed faunal assemblages are composite, and derived from the individual localities of Misius (1986). Popov et al (2009) concluded that Chu-Ili was a Japanese type active margin and an accretionary wedge in front of the North Tien Shan Microcontinent, and the Early Palaeozoic sedimentary and palaeontological record for Chu-Ili is the best in the Kazakh Orogen. The south-western boundary of Chu-Ili is the Zhalair-Naiman Fault Zone (Text- fig.…”

Chronology of early Cambrian biomineralization

“…The region was situated in proximity to East Gondwana and embraces Kazakhstanian terranes (Holmer et al 2001;Popov et al 2009). Among them, sections in the Lesser Karatau Range that include the Kyrshabakty and Chulaktau formations and the Shabakty Group in ascending order are the best studied and most continuous lower Cambrian sequences in Kazakhstan (Missarzhevsky & Mambetov, 1981;Holmer et al 2001).…”