Redefining the Huayquerian Stage (Upper Miocene – Lower Pliocene) of the South American chronostratigraphic scale based on biostratigraphic analyses and geochronological dating

ROMANO MUÑOZ, CRISTO; GARRIDO, ALBERTO; BARBEAU, D. L.; VERA, ROCÍO; BONINI, R.; BOSCAINI, ALBERTO; CERDEÑO, ESPERANZA; CRUZ, LAURA; ESTEBAN, GRACIELA; DE LA FUENTE, MARCELO; FERNÁNDEZ-MONESCILLO, MARCOS; FERNICOLA, JUAN CARLOS; KRAPOVICKAS, VERÓNICA; MADOZZO JAÉN, M; PEREZ, MARIA; PUJOS, FRANCOIS; RASIA, LUCIANO; TURAZZINI, GUILLERMO; VERA, BÁRBARA; MACPHEE, ROSS; FORASIEPI, ANALÍA; PREVOSTI, FRANCISCO

PALAEONTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2023

0031-0239

The Huayquerian Stage of the South American chronostratigraphic scheme was named in the Huayquerías del Este, Argentina, and defined originally based on a poorly-known mammal association from the Huayquerías Formation, with six recognised taxa. We studied geology, age, and fauna of the Neogene sequence in this area, including the Huayquerías, Tunuyán and Bajada Grande formations. The sequence comprises a monotonous succession of synorogenic epiclastic sediments developed under arid to semi-arid conditions. Zircon U-Pb dating from ten tuffaceous levels (7.2–1.6 Ma) place the deposition of the Huayquerías Formation during the late Tortonian/Messinian – early Zanclean, the Tunuyán Formation during the Zanclean–Piacenzian, and the Bajada Grande Formation during the Piacenzian–Calabrian. We present 43 and 31 new mammal taxa records for the Huayquerías and Tunuyán formations, respectively. Progressive faunal change was observed along the sequence. The first records of the Chaco tortoise Chelonoidis chilensis and the notoungulate Xotodon major, and the latest records of Interatheriidae and Typotheriopsis (notoungulates), Metacaremys calfucalel, Phtoramys hidalguense, and Lagostomus pretrichodactyla (rodents), Chasicotatus ameghinoi and Macroeuphractus morenoi (xenarthrans) are reported. The faunal associations of the Huayquerías and lower Tunuyán formations are highly similar, as well as with other coeval localities in Argentina. The Macroeuphractus morenoi Assemblage Biozone is proposed as the basis to redefine the Huayquerian Stage, based on the co-occurrence of three taxa of wide geographic distribution in southern South America: Macroeuphractus morenoi,105 Pseudotypotherium subinsigne, and Lagostomus pretrichodactyla. This Macroeuphractus morenoi Assemblage Biozone is constrained between c. 8 – c. 5 Ma in its type area.