Stages in development of the Silurian fauna and flora in the type areas ofeast Siberia

Three hundred twenty one species of graptolites, chitinozoans, acritarchs, cephalopods, trilobites, brachiopods, scolecodonts, conodonts, bryozoans, o stracodes, gastropods, crinoids, tetracorals, tabulates, heliolitids, strom atoporoids, and tentaculitids were recorded in the Silurian type areas of E ast Siberia. Three type areas, namely, Moiero, Turukhansk, and Noril'sk, ar e situated within the belt of shallow shelf facies predominantly bearing be nthic species intermediate between the deep-water and shoal biotas. Faunal and floral evolutionary stages were analyzed within local biointervals that correspond to the global biointervals (biochrons). The species of wide and limited stratigraphic ranges and peculiarities of their appearance and dis appearance were revealed. The major trend of species evolution in the type Silurian areas of East Siberia is their mass appearance and disappearance a t the initial and terminal Silurian time. This was associated with the glob al Silurian transgression at the beginning of the period and with the globa l regression at the end. Both events affected most sedimentary basins of th e platform. Secondary stages were associated with oscillations of the globa l sea level.