Unlike other South American basins, the boundary between Ordovician and Silurian in the Paraná Basin, Brazil, has yet to be studied in detail. This article reports the occurrence and taphonomic analysis of a fauna composed of the organophosphatic brachiopods Kosoidea australis and ?Palaeoglossa sp., the mollusks ?Paleoneilo sp. and ?Cuneamya sp., besides rynchonelliform brachiopods and the ostracods Harpabollia sp. and Satiellina paranaensis. This assemblage indicates a Hirnantian age for the top of the Iapó and the base of the Vila Maria formations, northeastern border of the Paraná Basin. Taphonomic signatures and facies associations point to a pro-glacial environment, at the transitional shoreface, represented by the last sedimentary facies of the Iapó Formation. The overlying transgressive strata represent the beginning of the Vila Maria Formation, in which fossils and lithofacies indicate predominant post-glacial conditions in an offshore setting. Two taphofacies were delineated. One features size- and type-selected fossils, deposited in rain-out facies originated from the melting glacier. The second, with autochthonous to parautochthonous fossils, represents a post-glacial offshore setting. The low faunal diversity points to marine connections between North and South African basins, and with South American basins.

与其他南美盆地不同，巴西巴拉那盆地的奥陶系和志留系之间的边界尚待详细研究。本文报告了由有机磷腕足类Kosoidea australis和?Palaeoglossa sp.组成的动物群的发生和土壤分类分析，软体动物?Paleoneilo sp.。和?Cuneamya sp.，除了 rynchonelliform 腕足动物和介形动物Harpabollia sp。和Satiellina paranaensis. 这个组合表明 Iapó 顶部和 Vila Maria 地层底部的 Hirnantian 时代，巴拉那盆地的东北边界。埋藏学特征和相关联指向过渡岸面的前冰川环境，以 Iapó 组的最后沉积相为代表。上覆的海侵地层代表了 Vila Maria 组的开始，其中的化石和岩相表明近海环境中的主要冰川后条件。划定了两个发胶相。一个特征是尺寸和类型选择的化石，沉积在源自融化的冰川的降雨相中。第二种，具有本土到准本土化石，代表了冰川后的近海环境。