Yecua Formation

Yecua Formation
Yecua Formation
Stratigraphic range: Late Langhian-Early Messinian; (Colloncuran-Huayquerian); ~
Underlies	Tariquia Formation
Overlies	Petaca Formation
Thickness	~50–300 m (160–980 ft)
Lithology
Primary	Mudstone, Sandstone[1]
Other	Gypsum
Location
Region	Chaco Basin
Country	Bolivia;

The Yecua Formation is a geological Formation in what is now Bolivia. Studies suggest that the Yecua Formation preserves a coastal setting with humid to semiarid floodplains, shorelines and tidal as well as shallow marine environments including marshes, streams, lakes and brackish bodies of water. There may have been a connection to the Amazon Basin or the Paranaense Sea.[2]

Bivalves

Name	Species	Member	Material	Notes
Tellina[1]	T. sp
cf. Cyrena[1]	cf. C. sp
cf. Astarte[1]	cf. A. sp
cf. Lucina[1]	cf. L. sp
Senis[1]	S. cf. elongatus
cf. Corbula or Cymbophora sp.[1]	cf. C. sp
cf. Nucula[1]	cf. N. sp

Gastropods

Name	Species	Member	Material	Notes
cf. Gyrodes or Natica sp.[1]
cf. Turritella[1]	cf. T. sp

Crustaceans

Name	Species	Member	Material	Notes
Bythocypris[1]	B. sp
Cyprideis[1]	C. sp
cf. Balanus[1]	cf. B. sp
indetermined crabs [1]

Vertebrates

Name	Species	Material	Notes
cf. Theosodon[1]	cf. T. sp	distal limb bone	a litopternan
Rodentia indet.[1]		tooth
Mourasuchus[3]	M. sp.	skull fragments, partial vertebrae & ribs
Pleurodira[3]		shell elements
Humboldtichthys[4]	Humboldtichthys kirschbaumi	incompletely preserved anterior portion of the body and posterior head	a Glass Knifefish
Siluriformes indet.[1]			possibly Ariidae
Characiformes or Clupeiformes[1]		a scale

References

Marshall, L.G.; Sempere, T.; Gayet, M. (1993). "The Petaca (Late Oligocene - Middle Miocene) and Yecua (Late Miocene) Formations of the Subandean-Chaco Basin, Bolivia, and their Tectonic Significance". Travaux et Documents des Laboratoires de Géologie de Lyon. 125: 291–301.
Hulka, C.; Gräfe, K.U.; Sames, B.; Uba, C.E.; Heubeck, C. (2006). "Depositional setting of the Middle to Late Miocene Yecua Formation of the Chaco Foreland Basin, southern Bolivia". Journal of South American Earth Sciences. 21: 135–150. doi:10.1016/j.jsames.2005.08.003.
Tineo, D.E.; P. Bona; L.M. Pérez; G.D. Vergani; G. González; D.G. Poiré; Z. Gasparini, and P. Legarreta. 2015. Palaeoenvironmental implications of the giant crocodylian Mourasuchus (Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of Bolivia. Alcheringa 39. 1–12.
Albert, J.S.; Fink, W.L. (2010). "Phylogenetic relationships of fossil neotropical electric fishes (Osteichthyes: Gymnotiformes) from the upper Miocene of Bolivia". Journal of Vertebrate Paleontology. 27 (1): 17–25. doi:10.1671/0272-4634(2007)27[17:PROFNE]2.0.CO;2.

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[Marshall1993-1] Marshall, L.G.; Sempere, T.; Gayet, M. (1993). "The Petaca (Late Oligocene - Middle Miocene) and Yecua (Late Miocene) Formations of the Subandean-Chaco Basin, Bolivia, and their Tectonic Significance". Travaux et Documents des Laboratoires de Géologie de Lyon. 125: 291–301.

[Hulka06-2] Hulka, C.; Gräfe, K.U.; Sames, B.; Uba, C.E.; Heubeck, C. (2006). "Depositional setting of the Middle to Late Miocene Yecua Formation of the Chaco Foreland Basin, southern Bolivia". Journal of South American Earth Sciences. 21: 135–150. doi:10.1016/j.jsames.2005.08.003.

[Tineo2015_p4-3] Tineo, D.E.; P. Bona; L.M. Pérez; G.D. Vergani; G. González; D.G. Poiré; Z. Gasparini, and P. Legarreta. 2015. Palaeoenvironmental implications of the giant crocodylian Mourasuchus (Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of Bolivia. Alcheringa 39. 1–12.

[Albert10-4] Albert, J.S.; Fink, W.L. (2010). "Phylogenetic relationships of fossil neotropical electric fishes (Osteichthyes: Gymnotiformes) from the upper Miocene of Bolivia". Journal of Vertebrate Paleontology. 27 (1): 17–25. doi:10.1671/0272-4634(2007)27[17:PROFNE]2.0.CO;2.