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Bahia de Guayacan (Pliocene of Chile)

Where: Coquimbo, Chile (30.0° S, 71.4° W: paleocoordinates 30.1° S, 70.3° W)

• coordinate estimated from map

When: Coquimbo Formation, Zanclean (5.3 - 3.6 Ma)

• middle Miocene?, Demere et al. (2005) questionably assign this collection to the Piacenzian, while Dathe (1983) had called it lower Pliocene

•In his original description, Dathe [155] did not specify the formation that has yielded the specimen, but stated that the fossil had been found at the western end of the “Bahia de Guayacan”, southwest of Coquimbo. He furthermore speculated that the fossil had come from a sandstone of Early Pliocene age, although he could not exclude the possibility of a Middle Miocene age. Dathe‟s figure of the type locality [155: fig. 10] shows primarily the Bay of Tongoy, which is dominated by exposures of the Miocene–Pliocene Coquimbo Formation [156, 157]. The latter is divided into 16 lithostratigraphic units, 5 of which (units 3, 4 and 11–13) have yielded cetaceans remains [156, 158]. Of the latter, only units 4 and 11– 13 contain sandstone, with only unit 11 being dominated by this lithology. Strontium dating and biostratigraphic evidence place units 3 and 4 in the Tortonian (11.9–11.2 Ma), and thus make them much older than the Early Pliocene age suggested by Dathe [155]. By contrast, units 11–13 have been dated to the earliest Pliocene based on biostratigraphic grounds, as well as Sr dates of 5.2 ± 0.7 Ma for the base of unit 12, 4.9 ± 0.7 Ma 2 m above the base ofunit 12, and 2.2 ± 0.5 Ma 6 m below the top of unit 14 (inferred mean ages for units 12 and 13 are 5.0 and 4.3 Ma, respectively) [156]. Considering the coincidence of (i) the occurrence of numerous cetacean fossils in units of the correct lithology and age; and (ii) the broad exposure of these units in the type area of “M. hubachi”, we suggest that the holotype of this species was recovered from the upper, Early Pliocene portion of the Coquimbo Formation. As a result, we follow Dathe [155] in assigning an Early Pliocene (Zanclean, 5.3–3.6 Ma) age to the holotype. Note, however, that Deméré et al. [59] suggested a Piacenzian (3.6–2.6 Ma) age for this specimen. (Marx & Fordyce, 2015)

Environment/lithology: slope; lithology not reported

• scarp-controlled rocky shoreline to upper continental slope

Size class: macrofossils

Primary reference: F. Dathe. 1983. Megaptera hubachi n. sp., ein fossiler Bartenwal aus marinen Sandsteinschichten des tieferen Pliozaens Chiles. Zeitschrift fuer Geologische Wissenschaften 11(7):813-848 [M. Uhen/M. Uhen/M. Uhen] more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 56460: authorized by Mark Uhen, entered by Mark Uhen on 18.11.2005

Creative Commons license: CC BY (attribution)