Macroinvertebrates of the Capivari marine bed, late Paleozoic glacial Itarare Group, northeast Parana Basin, Brazil: Paleoenvironmental and paleogeographic implications

摘要

A 2-m-thick silty shale bed within the Taciba Formation, Itarare Group, Parana Basin, State of Sao Paulo, southeastern Brazil, records marine sedimentation in a siliciclastic-dominated, low-energy, shelf setting, during a short-lived deglacial event. The bed is located 100-150 m below the base of the lower Permian, post-glacial Tatui Formation. The marine assemblage is dominated by rhynchonelliform brachiopods, with subordinate bivalves, gastropods and crinoids, recording the highest phylum-level diversity so far identified within a given fossil-bearing horizon in the uppermost portion of the Itarara Group. Two new species are described, one brachiopod Biconvexiella saopauloensis and one gastropod Peruvispira brasilensis. Additionally, shells of Lyonia rochacamposi, Rhynchopora grossopunctata, Quinquenella rionegrensis, Phestia tepuelensis, Streblopteria aff. S. lagunensis, Limipecten capivariensis, Praeundulomya cf. subelongata and Mourlonia (Woolnoughia)? sp. are identified. Crinoid columns were assigned to oPentaridica sp. (a genus based on elements of the columnal). This is the first systematic description of members of the Eurydesma-Lyonia fauna in the northeastern part of the Parana Basin, Brazil. The overwhelming majority of brachiopods belong to Biconvexiella saopauloensis, followed by Rhynchopora grossopunctata. The record of Lyonia rochacamposi closely resembles that of the uppermost part of the Taciba Formation in southern Brazil. Hence, the Capivari marine fauna correlates approximately with that of the upper part of the Taciba Formation. Lyonia rochacamposi also indicates correlation with Permian units of the Sauce Grande-Colorado (Argentina), Huab (Hardap shale of the Dwyka Group), Aranos area (Namibia), southwest Africa, and the Carnavon (Western Australia) basins. These correlations support a latest Asselian-earliest Sakmarian age for the fauna.