Lower Tremadocian (Ordovician) lingulate brachiopods from the Central Andean Basin (NW Argentina) and their biogeographical links

Abstract

The Cambrian-Ordovician linguliform brachiopods from the richly fossiliferous successions of Northwestern Argentina have received increasing attention during recent years, improving our knowledge on these ubiquitous marine organisms. An Upper Cambrian assemblage of lingulids, acrotretids and siphonotretids was described by Mergl et al. (2015) from the Lampazar Formation at the Angosto de Lampazar locality. Benedetto & Muñoz (2015) reported several obolid species from the Tremadocian Devendeus and Santa Rosita formations exposed in the Quebrada Humacha and Parcha (Jujuy Province). Later, Benedetto et al. (2018) recorded a low diversity brachiopod association dominated by the elkaniid Broggeria omaguaca Benedetto & Lavié, 2018 in Benedetto et al. (2018), from upper Tremadocian open-shelf mudstones of the Coquena and Santa Rosita formations, in the Santa Victoria and Purmamarca regions. The main goal of this paper is to describe and illustrate a new fauna recovered from the lower Tremadocian Pupusa Formation at Angosto del Moreno, in the Jujuy Province, and to provide a discussion on its biogeographic affinities considering all Tremadocian lingulides identified up to the present from NW Argentina. Such palaeobiogeographic analysis allows testing the hypothesis of a migratory route linking the Central Andean Basin with north Gondwana and Perunica via the clastic platforms fringing the North African and Brazilian shields (Benedetto & Muñoz 2015). Geological settingIn northwestern Argentina, the Cambrian and Ordovician systems are superbly represented by continuous and richly fossiliferous clastic shelf deposits reaching over 3,500 m in thickness. The succession has been referred originally to the Santa Victoria Group (Turner 1960), encompassing the Santa Rosita and the Acoite formations. Stratigraphic nomenclature, however, differs through the basin because of substantial lateral and vertical lithofacial changes (Astini 2003). In the studied area, located on the western slope of the Cordillera Oriental (Fig. 1), the succession has been referred to the Guayoc Chico Group (Ramos 1973), which is coeval with the lower part of the Santa Rosita Formation (Vaucher et al. 2020). The Guayoc Chico Group encompasses, from bottom to top, the