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Cerro La Bota (Miocene of Argentina)

Also known as Zone of Chasichimys bonaerense

Where: La Pampa, Argentina (37.4° S, 65.5° W: paleocoordinates 37.6° S, 62.6° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Chasicoan mammal zone, Cerro Azul Formation, Chasicoan (10.0 - 9.0 Ma)

• Early late Miocene

•The stratotype is the lower level of the Cerro Azul Formation outcropping at this locality

•Montalvo et al. 2019: The revision of the vertebrate assemblage from this locality, as well as new geomorphologic and sedimentological interpretations of the Cerro Azul Formation in the area, confirms the previous assignation to the Chasicoan age.

Environment/lithology: fluvial; lithified, massive, red, sandy siltstone and lithified, medium-grained, sandy conglomerate

• Montalvo et al. 2019: Sedimentological and stratigraphic descriptions of the Cerro Azul Formation at Cerro La Bota locality were originally performed by Goin et al. (2000). These authors interpreted that the levels cropping out in this site represent ephemeral fluvial deposits. We propose here a new interpretation (Fig. 2) by recognizing two facies associations: loess-palaeosol association (FA1) and fluvial deposits association (FA2).

•The amalgamated conglomeradic–sandy bodies suggest the episodic development of perennial streams without flow division on a loessic substrate.

•Schmidt et al. 2018: Levels of Cerro Azul formation at Cerro La Bota represent an ephemeral fluvial event (Goin et al. 2000; Verzi et al. 2008).

• The Cerro Azul formation is composed of massive brown reddish sandy silts, with loessic erosion. A detailed description of the geology and stratigraphy of this formation can be seen in Linares et al. (1980) and Goin et al. (2000).

•Montalvo et al. 2019: The FA1 crops out in the lower part of the studied section and is 1.7 m thick (Fig. 2). It includes sheet-like strata with non-erosive bases, composed of massive and commonly very fine-grained siltstones (facies Fsm) with root traces (facies P).The FA2 is 2.2 m thick and overlays FA1 deposits with erosive contact (Fig. 2). It is constituted by a lateral and vertical erosive superposition of sandstone (facies St) and conglomeratic (facies Gt) bodies.

Size classes: macrofossils, mesofossils

Collection methods: Montalvo et al. 2019: specimens recovered belong to the Paleontological Collection of the Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa (La Pampa Province, Argentina).

•Esteban, et al. 2000: Todos los ejemplares analizados están depositados en

•la Cátedra de Geología Histórica de la Facultad de Ciencias Exactas y Naturales de la Universidad Nacional ele La Pampa, Argentina, cuyo acrónimo es GHUNLPam

Primary reference: D. H. Verzi, C. I. Montalvo, and C. M. Deschamps. 2008. Biostratigraphy and biochronology of the Late Miocene of central Argentina: Evidence from rodents and taphonomy. Geobios 41:145-155 [C. Jaramillo/M. Vallejo] more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 152063: authorized by Carlos Jaramillo, entered by Maria Vallejo on 05.11.2013, edited by Grace Varnham and Miranta Kouvari

Creative Commons license: CC BY (attribution)