The Karatau Fault System of southern Kazakstan forms a crustal-scale zone of strike-slip dominated transpressional tectonics which has undergone multiple phases and styles of deformation during a protracted history of reactivation from the Neoproterozoic to the Cenozoic. Ductile fabrics associated with dextral kinematic indicators are present in amphibolites along the Main Karatau Fault. The ages of the (possibly ophiolitic) protoliths and the ductile fabrics are not well constrained, but they are plausibly pre-late Riphean. Late Ordovician granites stitch thrusts and folds which deform late Riphean to Llanvirn clastics, preserved beneath a regional Late Devonian angular unconformity. This deformation may be related to a contemporary continental collision NE of the Karatau. Two phases of late Palaeozoic deformation affected the Upper Devonian and Carboniferous carbonate succession. The first phase is related to sinistral transpression along the Karatau Fault System, the second to dextral transpressional reactivation. The combination of these events produced a regional-scale dome-and-basin fold interference pattern. Similar polyphase deformation appears to have affected large areas of Central Asia and was possibly caused by the late Palaeozoic orogenies at Asia’s margins, such as the accretion of Tarim and the East European Craton to Asia, and the closure of the Kazakstan Orocline. Normal faults in the Karatau are related to the formation of the Leontiev Graben, South Turgay Basin and the Yarkand–Fergana Basin in the Early to Mid-Jurassic, during renewed dextral slip along the Karatau/Talas–Fergana Fault. Late Cenozoic deformation is minor, and resulted in the uplift and incision of a Cretaceous–Palaeogene peneplain without a major tectonic overprint. Reversals in the sense of strike-slip dominated transpressive deformation across major fault systems results in transpressive inversion . This represents an ideal process with which to generate overprinting orthogonal fold systems, resulting in classic dome and basin interference patterns on a regional scale.
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.
The base of the Cordylodus proavus conodont Zone is the most appropriate horizon for the Cambrian-Ordovician Boundary. At Batyrbay the horizon reflects a significant global eustatic event that is marked by distinctive geochemical changes and by drastic changes in the trilobite and conodont faunas. The palaeomagnetic polarities change from reversal to normal just below this horizon.
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The Main Karatau fault is a classical crustal strike-slip zone. It originated as a continental rift structure in the Late Proterozoic and had been developed incessantly for almost 1 billion years as inherited structure. The fault was subjected to polyphase deformations associated with both dextral and sinistral shifts. The Main Karatau fault crosses the Earth’s crust, including the structures of granite-metamorphic layer and granulite-basitic layer and fades without crossing the Moho discontunious. The amplitude of displacement of the Syr-Daria and Chu-Sarysu blocks relative to each other along the Main Karatau fault is estimated at approximately 200 km.
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