New invertebrate peri-glacial faunal assemblages in the Agua de Lucho Formation, Rio Blanco basin, Argentina. The most complete marine fossil record of the early Mississippian in South america

STERREN, A.F.; CISTERNA, G.; RUSTÁN, JUAN JOSÉ; VACCARI, N.E.; BALSEIRO, DIEGO; EZPELETA, M.; PRESTIANNI, C.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021 vol. 106 p. 1 - 18

0895-9811

A new fossil record of early Mississippian marine faunas is described from sedimentarysuccessions of the Agua de Lucho Formation in the Sierra de las Minitas (La Rioja province, RíoBlanco Basin, western Argentina). Considered Tournaisian in age based on local palynologicaldata and biostratigraphic correlations, this faunal record is notably diverse and linked to glaciallyinfluenced sedimentary settings, in contrast with other early Mississippian assemblages fromArgentina, traditionally described as developed in warm to temperate climates. The verticaldistribution of bivalves and brachiopods, in particular, indicates significant faunal changesthrough the thick section studied, and their occurrences are compared with those describedfrom the Zorritas Formation in northern Chile. The new records include some typicalcomponents of the regional Michiganites scalabrinii-Azurduya chavelensis assemblage Zone,but important vertical and lateral compositional variations of this biozone are discussed. It is also highlights the importance of the species Azurduya chavelensis as a conspicuouscomponent of the Early Mississippian deposits from South America, which would become aproper macrofaunal tool to intra and inter-basinal correlations.