THE NEAR-HYDROTHERMAL FAUNA OF THE SILURI AN PALEOOCEAN IN THE SOUTH URAL

Well preserved, abundant burials of the fauna of near-hydrothermal ben thic communities have been found in the Yaman-Kasyn sulfide ore struct ures of the South Ural. These structures were formed in the early Silu rian period (430-450 million years ago) in the regions of hydrothermal activity of a marginal sea of the Ural paleoocean. The burials proved lo be more ancient (by 50 million years) that our previous findings d ated from the middle Devonian period (Kuznetsov et al., 1991). Just as in the Sibai region of the South Ural, the burials were represented b y residues of the same groups of benthic animals: vestimintifers, biva lves of the vesicomiid type, and polychaetes of the alvinellid type. T hese groups constituted and now constitute the basic fauna near the ho t and warm hydrothermal springs in the Devonian, Cretaceous and contem porary communities. With respect to the structural-functional organiza tion, the near-hydrothermal communities of these periods formed as par allel (similar) isocommunities-analogs, thus illustrating the universa l principles of formation and functioning of communities in the marine hydrosphere.