Dos Bocas Formation

Dos Bocas Formation
Stratigraphic range: Chattian (Deseadan) ~26–24  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Montañita-Olón locality with outcrops of the Dos Bocas Formation
Type	Geological formation
Unit of	Subibaja Group
Underlies	Villingota Formation
Overlies	Zapotal Formation
Lithology
Primary	Sandstone
Location
Coordinates	1°48′S80°48′W / 1.8°S 80.8°W / -1.8; -80.8
Approximate paleocoordinates	3°36′S75°30′W / 3.6°S 75.5°W / -3.6; -75.5
Region	Santa Elena Province
Country	Ecuador
Extent	Progreso Basin

The Dos Bocas Formation is a sedimentary geological formation of the Progreso Basin in southwestern Ecuador. It is dated to the Chattian, about 26 to 24 Ma, (Deseadan in the SALMA classification).

Description

Stratigraphy of the Montañita-Olón locality

The formation comprises moderately-sorted, fine to medium sandstones with angular quartz-feldspathic clasts. Conspicuous rounded green grains are probably glauconite, but berthierine cannot be dismissed. The matrix is micritic and volcanogenic, possibly bentonitic. The formation was deposited in an estuarine to mid shelf environment. Fossils of sharks, turtles and the tropical dolphin Urkudelphis were recovered from the formation. ^{[1] [2]}

Fossil content

The formation has provided fossils of:

• Carcharocles angustidens
• Urkudelphis chawpipacha
• Chelonioidea indet.

See also

• List of fossiliferous stratigraphic units in Ecuador
• Bahía Inglesa Formation
• Coquimbo Formation
• Pisco Formation

References

1. Tanaka, Y.; Abella, J.; Aguirre-Fernández, G.; Gregori, M.; Fordyce, E. R. (2017). "A new tropical Oligocene dolphin from Montañita/Olón, Santa Elena, Ecuador". PLOS ONE. 12 (12): e0188380. Bibcode:2017PLoSO..1288380T. doi: 10.1371/journal.pone.0188380 . PMC   5737981 . PMID   29261688.
2. Carrillo-Briceño, J. D.; Villafaña, J. A.; De Gracia, C.; Flores-Alcívar, F. F.; Kindlimann, R.; Abella, J. (2020). "Diversity and paleoenvironmental implications of an elasmobranch assemblage from the Oligocene–Miocene boundary of Ecuador". PeerJ. 8: e9051. doi: 10.7717/peerj.9051 . PMC   7195833 . PMID   32391203.