Valle Alto Formation

The Valle Alto Formation (Spanish: Formación Valle Alto, Jva) is a geological formation of the Central Ranges of the Colombian Andes. The formation is composed of shales, sandstones and conglomerates and dates to the Late Jurassic period. Ammonites and fossil flora have been found in the Valle Alto Formation.

Valle Alto Formation
Stratigraphic range: Late Jurassic
~150–145 Ma
↓
TypeGeological formation
Unit ofQuebradagrande Complex
Lithology
PrimaryShale, sandstone
OtherConglomerate
Location
Coordinates5°22′08″N 75°22′03″W
RegionCaldas Department
Central Ranges
Andes
Country Colombia
Type section
Named forHacienda Valle Alto
Named byGonzález et al.
LocationSan Félix
Year defined1977
Coordinates5°22′08″N 75°22′03″W
Approximate paleocoordinates3.1°N 72.4°W / 3.1; -72.4
RegionCaldas
Country Colombia

Paleogeography of Northern South America
150 Ma, by Ron Blakey
Landscape around San Félix, Caldas, where the formation is found

Etymology

The formation was described and named in 1977 by González et al. after Hacienda Valle Alto, San Félix, Caldas.[1][2]

Lithologies

The Valle Alto Formation is composed of shales, sandstones and conglomerates.[3]

Stratigraphy, age and depositional environment

The Valle Alto Formation, part of the Quebradagrande Complex, is not defined as a proper formation, rather as a collection of rocks of different facies origin segmented by tectonic forces of the Central Ranges.[1]

The Valle Alto Formation has been deposited as the result of marine incursions from the proto-Caribbean into Colombia, preceding the larger-scale transgression of the Cretaceous.[4]

Fossil content

Fossils of Piazopteris branneri,[note 1] Cladophlebis sp., Classopollis sp., Ctenozamites sp., Desmiophyllum sp., Gleichenites sp., Nilssoniopteris sp., Otozamites sp., Pachypteris sp., Ptilophyllum sp., Rhabdoderas sp., Sagenopteris sp., Sandlingites sp., Sphenopteris sp., Substeuroceras sp., Trigonia sp., and Zamites sp. have been found in the Valle Alto Formation.[5][6]

Outcrops
Type locality of the Valle Alto Formation in Caldas

The Valle Alto Formation is found near its type locality in the Central Ranges of the Colombian Andes, around Pácora and Salamina.[1]

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See also
Geology of the Eastern Hills
Geology of the Ocetá Páramo
Geology of the Altiplano Cundiboyacense

Notes
  1. Piazopteris branneri listed as the Permian genus Glossopteris (branneri)[5]

References
  1. Moreno Sánchez et al., 2007
  2. Mojica, 1984, p.132
  3. Isagen, 2009, p.9
  4. Mojica & Kammer, 1995, p.170
  5. Mojica, 1984, pp.131-132
  6. Valle Alto Formation at Fossilworks.org

Bibliography

Maps
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