Yecua Formation

Yecua Formation
Yecua Formation
Stratigraphic range: Late Langhian-Early Messinian; (Colloncuran-Huayquerian); ~14–7 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Underlies	Tariquia Formation
Overlies	Petaca Formation
Thickness	~50–300 m (160–980 ft)
Lithology
Primary	Mudstone, Sandstone
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 litoptern
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

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r 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 (1–2): 135–150. doi:10.1016/j.jsames.2005.08.003.
^ ^a ^b Tineo, D.E.; Bona, P.; Pérez, L.M.; Vergani, G.D.; González, G.; Poiré, D.G.; Gasparini, Z.; Legarreta, P. (2015). "Palaeoenvironmental implications of the giant crocodylian Mourasuchus (Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of Bolivia". Alcheringa. 39 (2): 1–12. doi:10.1080/03115518.2015.967162. hdl:11336/33274. S2CID 129930697.
^ 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. S2CID 35007130.

[Marshall1993-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r 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 (1–2): 135–150. doi:10.1016/j.jsames.2005.08.003.

[Tineo2015_p4-3] Tineo, D.E.; Bona, P.; Pérez, L.M.; Vergani, G.D.; González, G.; Poiré, D.G.; Gasparini, Z.; Legarreta, P. (2015). "Palaeoenvironmental implications of the giant crocodylian Mourasuchus (Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of Bolivia". Alcheringa. 39 (2): 1–12. doi:10.1080/03115518.2015.967162. hdl:11336/33274. S2CID 129930697.

[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. S2CID 35007130.

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