Rio Chico (Miocene of Argentina)

Where: Chubut, Argentina (42.1° S, 70.5° W: paleocoordinates 42.6° S, 66.3° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Colloncuran mammal zone, Collon Cura Formation, Middle Miocene (16.0 - 11.6 Ma)

• In general terms, in the area of study the Collón Curá Formation (middle Miocene) overlies conformably and unconformably the La Pava (late lower Miocene) Formation and is unconformably overlaid by the Río Negro Formation (Miocene-Pliocene).

Environment/lithology: fluvial-lacustrine; volcaniclastic sandstone

• In this depression, two sections of the Collón Curá Formation crop out. The lower section is formed mainly by lacustrine facies, characterized by silts, sandstones, marls and limestones. The upper section starts with fine-grained, silty and somewhat greenish sandstones, followed by yellowish-gray sandstones with alternating sandstones of varying granulometry, sabulites, and scarce inclusions of breccia. About 22 kilometers north from Calera Esparza, on the Chico river, Bilmes et al. (2013, 2014) describe in detail a sequence of the Collón Curá Formation, mentioning that it has a maximum thickness of 300 meters, composed of whitish, tufaceous sandstones and tuffs. The authors informally divide it into three sections: a lower one characterized by an ephemeral lacustrine system, a medium section characterized by a deep lacustrine system, with offshore facies and deltas, and an upper one characterized by a deep lacustrine environment with shallow facies. The fossils are rolled out from sandstone levels with high content of pyroclastic material.

Size class: macrofossils

Collection methods: surface (in situ),

• LIEB-PV, Laboratorio de Investigaciones en Evolución y Biodiversidad, Facultad de Ciencias Naturales sede Esquel, Universidad Nacional de la Patagonia “San Juan Bosco”, Esquel, Chubut province, Argentina

Primary reference: C. Oriozabala, J. Sterli, and L. Gonzalez Ruiz. 2018. Morphology of the mid-sized tortoises (Testudines: Testudinidae) from the Middle Miocene of Northwestern Chubut. Ameghiniana 55(1):30-54 [E. Vlachos/E. Vlachos/E. Vlachos]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 186559: authorized by Evangelos Vlachos, entered by Evangelos Vlachos on 26.06.2017

Creative Commons license: CC BY (attribution)

Taxonomic list

 Testudines - Pantestudinidae
Chelonoidis gringorum Simpson 1942 turtle