Brachiopods from the Río del Peñón Formation. Río Blanco Basin, Upper Palaeozoic of Argentina.

Abstract

This paper reviews the brachiopod fauna from the Ríoo de! Peñón Formation, Río Blanco Basin, Upper Palaeozoic of La Rioja province, Argentina. Traditionally, this unit was referred to the Carboniferous, however the braquiopod fauna here studied suggests a new biostratigraphical interpretation, indicating an age range from the latest Carboniferous to Early Permian. Three different brachiopod assemblages can be identified in the section: Assemblage I, from the lower member, includes Streptorhynchus? sp., Dyschrestia? sp., Costatumulus sp. A, Trigonotreta sp., Spiriferellina sp., Orbiculoidea sp., and unidentifiable productids and strophomenids.Assemblage II, from the middle member, includes Tivertonia jachalensis (Amos), Kochiproductus riojanus (Leanza), Costatumulus sp. B, Trigonotreta riojanensis (Lech and Acefiolaza) and Orbiculoidea sp. Assemblage III, from the highest part of the middle member, includes Neochonetes pegnonensis sp. nov., Costatumulus sp. C, Rhynchopora sp., Septosyringothyris jaguelensis Lech, and Orbiculoidea sp. These brachiopod assemblages demonstrate close affinities with faunas from the lower Permian of Western Australia and India. Affinities with faunas from Peru and Texas are less close.