Tracking Silurian-Devonian events and paleobathymetric curves by ichnologic and taphonomic analyzes in the southwestern Gondwana

摘要

Trace fossils have been used worldwide to access paleoecologic data in sedimentary sections. In Parana Basin (southern Brazil), trace fossils are stratigraphically well distributed; however, they are understudied if compared to body macrofossils or microfossils. Only few studies applied ichnology to the Silurian-Devonian strata, and mostly focused in an ichnotaxon. This comprehensive study aims to analyze the ecospace colonization represented by trace fossils in a Silurian-Devonian section from Parana Basin, and to associate the paleoenvironmental data provided by trace fossils with the decline of the Malvinokaffric Realm. In this sense, trace fossils were analyzed in six sedimentary sections to encompass the whole outcropping supersequence. The vertical distribution of trace fossils (Glossifungites, Skolithos and Cruziana ichnofacies) was compared with the distribution of the Malvinokaffric macrofossils. Paleoecologic and ichnodisparity analyzes allowed to infer dominance of stable conditions throughout the Silurian-Devonian section; however, some levels express dysoxic to anoxic conditions, and in others the high energetic conditions biased the ichnologic record. The stratigraphic distribution of Zoophycos suggests a change in the basin configuration during Eifelian, which might be related to the decline in the diversity of the Malvinokaffric fauna.