Gracias Formation

Gracias Formation
Stratigraphic range: Miocene
Type	Formation
Underlies	Pleistocene basalt
Overlies	Padre Miguel Group
Thickness	200–300 m (660–980 ft)
Lithology
Primary	Sandstone, siltstone, claystone
Other	Conglomerate
Location
Coordinates	21°12′N100°42′W / 21.2°N 100.7°W / 21.2; -100.7
Approximate paleocoordinates	21°42′N98°00′W / 21.7°N 98.0°W / 21.7; -98.0
Region	Lempira Department
Country	Honduras
Type section
Named for	Gracias
Named by	Williams & McBirney
Year defined	1969
Gracias Formation (Honduras)

The Gracias Formation is a geologic formation in Honduras. The mainly sandstones, siltstones and claystones preserve vertebrate fossils dating back to the Neogene period. ^[1]

Description

The Gracias Formation is a sedimentary unit, consisting of sandstone, siltstone, claystone and a few conglomeratic beds. The formation crops out in western Honduras and ranges from 200 to 300 metres (660 to 980 ft) in thickness. The formation overlies the Padre Miguel Group, while it is overlain by Pleistocene basalts. ^[2] The Padre Miguel Group provided the provenance for the sedimentary material for the Gracias Formation. The clasts in the formation are largely composed of rhyolite, rhyodacite, pumice, vitric ash, quartz, feldspar, and minor biotite fragments. ^[3]

Fossil content

• Borophagus secundus
• Calippus hondurensis ^[4]
• Cormohipparion ingenuum
• Procamelus cf. grandis
• Prosthennops cf. serus
• Protolabis cf. heterodontus
• Pseudoceras skinneri
• Rhynchotherium cf. blicki
• Teleoceras sp.
• Rhinocerotidae indet.

See also

• Earth sciences portal
• Paleontology portal

• List of fossiliferous stratigraphic units in Honduras

References

1. Gracias Formation at Fossilworks.org
2. N.N., s.a., Informe de Apoyo, A-9
3. Sánchez Barreda, 1999, p.25
4. Hulbert, 1988, p.272

Bibliography

• Hulbert, Jr., R.C (1988), "Calippus and Protohippus (Mammalia, Perissodactyla, Equidae) from the Miocene (Barstovian-early Hemphillian) of the Gulf Coastal Plain", Bulletin of the Florida State Museum, Biological Sciences, 32: 221–340, retrieved 2019-02-09
• Sánchez Barreda, Luis A (1999), Geology of Mosquitía and Tela Basins, Honduras (PDF), University of Texas at Austin, pp. 1–55, retrieved 2019-02-09
• N., N, Informe de Apoyo - Estudio Geológico para la ciudad Tegucigalpa (PDF), pp. A1-57, retrieved 2019-02-09

Further reading

• E. C. Olson and P. O. McGrew. 1941. Mammalian fauna from the Pliocene of Honduras. Bulletin of the Geological Society of America 52:1219-1244
• S. D. Webb and S. C. Perrigo. 1984. Late Cenozoic Vertebrates from Honduras and El Salvador. Journal of Vertebrate Paleontology 4(2):237-254