The Valle Alto Formation (, Jva) is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

of the

Central Ranges Central Ranges (code CER) is an Australian bioregion, with an area of 101,640.44 square kilometres (39,244 sq mi) spreading across two states and one territory: South Australia, Western Australia, and the Northern Territory.Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

. The formation is composed of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s and conglomerates and dates to the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

period.

Ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

s and fossil flora have been found in the Valle Alto Formation.

Etymology

The formation was described and named in 1977 by González et al. after Hacienda Valle Alto, San Félix, Caldas.Moreno Sánchez et al., 2007Mojica, 1984, p.132

Lithologies

The Valle Alto Formation is composed of

s and conglomerates.Isagen, 2009, p.9

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 In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

origin segmented by tectonic forces of the Central Ranges. 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.Mojica & Kammer, 1995, p.170

Fossil content

Fossils of '' Piazopteris branneri'', '' 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.Mojica, 1984, pp.131-132Valle Alto Formation
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org

Outcrops

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

Notes

References

Bibliography

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Maps

* {{Paleontology in Colombia, state=expanded Geologic formations of Colombia Jurassic System of South America Jurassic Colombia Tithonian Stage Fossiliferous stratigraphic units of South America Paleontology in Colombia Sandstone formations Shale formations Shallow marine deposits Formations