The Castillo Formation is an Early Miocene (Burdigalian, Colhuehuapian to Santacrucian in the SALMA classification) geologic formation in the Falcón Basin of Venezuela. The formation unconformably overlies the Matatere, Misoa, El Paují and Jarillal Formations.[1] The Castillo Formation is overlain by Quaternary alluvium and in places by the Capadare Formation.[2] The formation, deposited in a calm near-shore lagoonal brackish environment, with possibly fluvial influence, has provided a rich assemblage of fossil crocodylians, turtles, giant sloths and various types of fish.
| Castillo Formation | |
|---|---|
| Stratigraphic range: Burdigalian (Colhuehuapian-Santacrucian) ~ | |
| Type | Geological formation |
| Unit of | Falcón Basin |
| Underlies | Capadare Formation |
| Overlies | Matatere, Misoa, El Paují and Jarillal Formations |
| Thickness | 367 m (1,204 ft) |
| Lithology | |
| Primary | Argillaceous marl |
| Other | Hardground, gypsum |
| Location | |
| Coordinates | 10°33′50″N 69°43′42″W / 10.56389°N 69.72833°W |
| Approximate paleocoordinates | 9°36′N 66°42′W / 9.6°N 66.7°W |
| Region | Falcón, Lara |
| Country |  Venezuela |
| Extent | From La Mesa to Siquisique |
| Type section | |
| Named by | Wheeler |
| Year defined | 1960 |
 Paleogeography of Northern South America, 20 Ma by Ron Blakey | |
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Description edit
The Castillo Formation crops out cover a wide semicircular area that extends through the northwestern Venezuelan states of Falcón and Lara. During Oligocene to Miocene times, the formation formed the northwest to southeast edge of the Falcón Basin.[3] The formation, with a minimum thickness of 367 metres (1,204 ft),[4] has formerly been regarded as Late Oligocene in age (Wheeler, 1960), but more recent workers, regard it to be Early Miocene. The Castillo Formation at Cerro La Cruz comprises 87 metres (285 ft) of clayey marls, interbedded with numerous thin (less than 1 metre (3.3 ft)) hardground units. The strata are underlain and overlain by sandstones, and the upper 15 metres (49 ft) are gypsiferous.
The formation was deposited in a calm near-shore marine to brackish lagoonal environment with possibly fluvial influence.[5] Elements of the fauna are consistent with the hypothesis that a tributary and/or delta of the Orinoco existed in this area of northwestern Venezuela during Early Miocene times.[6] Other authors did not find convincing results to support this hypothesis.[7]
Fossil content edit
In the formation, apart from corals, fossils of the giant sloth Baraguatherium takumara, the turtle Chelus colombiana, the crocodylians Siquisiquesuchus venezuelensis,[8] Purussaurus, Caiman,[9] Gryposuchus,[10] and indeterminate other crocodylians,[11] and the pelican-like Pelagornis sp. have been found. The pelican-like fossil is the oldest of South America.[12][13]
Other fossils reported from the formation are:[6][14]
- silky shark (Carcharhinus falciformis)
- wahoo (Acanthocybium sp.)
- barracuda (Sphyraena sp.)
- Carcharhinus cf. obscurus
- Carcharhinus cf. perezi
- Hemipristis serra
- aff. Prosqualodon australis
- Bairdemys sp.
- Rhinoptera sp.
- Scirrotherium sp.
- Arecaceae indet.
- Astrapotheriidae indet.
- Iniidae indet.
- Litopterna indet.
- Mylodontidae indet.
- Platanistoidea indet.
- Squalidae indet.
- Tardigrada indet.
- Trionychoidea indet.
See also edit
References edit
- ^ Urbani & Mendi, 2010, p.17
- ^ Urbani & Mendi, 2010, p.19
- ^ Solórzano et al., 2018a, p.3
- ^ Rincón et al., 2014, p.510
- ^ Cerro La Cruz at Fossilworks.org
- ^ a b Cerro La Cruz, Unit C at Fossilworks.org
- ^ Rincón et al., 2014, p.522
- ^ Siquisique at Fossilworks.org
- ^ Solórzano et al., 2018a, p.12
- ^ Solórzano, 2018b, p.121
- ^ Solórzano et al., 2018, p.1
- ^ (in Spanish) Tres curiosos animales prehistóricos emergen del subsuelo venezolano Archived 2017-08-16 at the Wayback Machine
- ^ (in Spanish) Hallan restos de tres animales prehistóricos en Lara Archived 2017-08-16 at the Wayback Machine
- ^ Cerro La Cruz at Fossilworks.org
- ^ Cerro Guariro at Fossilworks.org
Bibliography edit
- Johnson, Kenneth G.; Marcelo R. Sánchez Villagra, and Orangel A. Aguilera. 2009. The Oligocene-Miocene transition on coral reefs in the Falcón Basin (NW Venezuela). PALAIOS 24. 59–69. Accessed 2017-08-15.
- Rincón, Ascanio D.; Andrés Solórzano; H. Gregory McDonald, and Mónica Núñez Flores. 2017. Baraguatherium takumara, gen. et sp. nov., the earliest mylodontoid sloth (early Miocene) from northern South America. Journal of Mammalian Evolution 24(2). 179–191. Accessed 2019-02-12.
- Rincón, Ascanio D.; Andrés Solórzano; Mouloud Benammi; Patrick Vignaud, and H. Gregory McDonald. 2014. Chronology and geology of an Early Miocene mammalian assemblage in North of South America, from Cerro La Cruz (Castillo Formation), Lara State, Venezuela: implications in the 'changing course of Orinoco River' hypothesis. Andean Geology 41. 507–528. Accessed 2018-09-07.
- Solórzano, Andrés; Ascanio D. Rincón; Giovanne M. Cidade; Mónica Núñez Flores, and Leonardo Sánchez. 2018a. Lower Miocene alligatoroids (Crocodylia) from the Castillo Formation, northwest of Venezuela. Palaeobiodiversity and Palaeoenvironments _. 1–19. Accessed 2018-09-07.
- Solórzano, Andrés; Mónica Núñez Flores, and Ascanio D. Rincón. 2018b. Gryposuchus (Crocodylia, Gavialoidea) from the early Miocene of Venezuela. PalZ 92. 121–129. Accessed 2018-09-07.
- Urbani, Franco, and David Mendi. 2010. Notas sobre la discordancia del margen sur de la cuenca Oligo-Miocena de Falcón estados Lara, Falcón y Yaracuy, Venezuela. Boletín de la Academia de Ciencias Físicas, Matemáticas y Naturales LXX. 9–25. Accessed 2017-08-15.
Further reading edit
- C. A. Brochu and A. D. Rincón. 2004. A gavialoid crocodylian from the Lower Miocene of Venezuela. Special Papers in Palaeontology 71:61-79
- R. M. Feldmann and C. E. Schweitzer. 2004. Decapod Crustaceans from the Lower Miocene of North-Western Venezuela (Cerro La Cruz, Castillo Formation). Special Papers in Palaeontology 71:7-22
- M. R. Sánchez Villagra, R. J. Asher, A. D. Rincón, A. A. Carlini, P. Meylan and R. W. Purdy. 2004. New faunal reports for the Cerro La Cruz locality (lower Miocene), north-western Venezuela. Special Papers in Palaeontology 71:105-112
- M. R. Sánchez Villagra, R. J. Burnham, D.C. Campbell, R.M. Feldmann, E.S. Gaffney, R.S. Kay, R. Lozsan, R. Purdy, and J.G.M. Thewissen. 2000. A new near-shore marine fauna and flora from the early Neogene of northwestern Venezuela. Journal of Paleontology 74(5):957-968