Boreskov

PP‐23EVOLUTION OF TRILOBITE BIOFACIES IN EARLY AND MIDDLE CAMBRIAN(OUTER SHELF OF THE SIBERIAN PALEOBASIN)Korovnikov I.V. 1 , Sabanov Yu.Ya. 21 Trofimuk Institute of Petroleum‐Gas Geology and Geophysics SB RAS, Novosibirsk 630090,Academician Koptjug Prospect 3, Russia, KorovnikovIV@ipgg.nsc.ru ;2 Siberian Research Institute of Geology, Geophysics and Mineral Resources, Novosibirsk630091, Krasny Prospect 67, Russia, Cambrian@sniiggims.ruTrilobites associations lived in similar facies conditions are considered as TrilobiteBiofacies. Studies of the Cambrian Trilobite Biofacies on the Siberian platform can be veryuseful for biostratigraphy, paleobiogeographical analysis, detection paleoecological featuresof habitats and the evolution of the basic elements of marine ecosystems of the EarlyPaleozoic, which played an important role in the Phanerozoic biosphere.The Siberian platform is an ancient piece of continental crust that was an islandcontinent in Cambrian time. Three distinct facies belts comprise the Early Cambrian andEarly Middle Cambrian of the Siberian Platform: a western belt of restricted‐circulation,evaporitic carbonate sediments (Turukhan–Irkutsk–Olekma facies region), a reef‐shoaltransitional belt of archaeocyathan‐microbial facies (Anabar–Syn facies region), and anopen‐marine eastern and northern belt (Judoma–Olenek facies region).Trilobites, which appeared in the Early Cambrian to Early Middle Cambrian widelydispersed in the territory of the Siberian platform. They had high rates of evolution and havebecome the most numerous and diverse group of organisms that time and existed in allthree facial regions. There is a dependency of the trilobites associations from their place inthe Siberian platform and the facial nature of rocks, which enclosed the remains of trilobites(Pegel, 2000). The main factors influencing the settlement of trilobites were salinity, depthand nature of substrate (Repina, 1977). In addition to the spatial variability observed changeof a Trilobite Biofacies over time. Often these changes are associated with changes in facialconditions. But sometimes these changes occurred regardless of changes in facial conditions.The authors analyzed the trilobites associations from the Eastern part of the SiberianPlatform, which existed in the Early and Early Middle Cambrian on the outer shelf of theSiberian paleobasin. Most of trilobites associations rigidly tied to facies, although someassociations are found in different rocks.171