Earth:Rosablanca Formation

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Short description: Geologic formation in the Andes
Rosablanca Formation
Stratigraphic range: Valanginian
~136–133 Ma
TypeGeological formation
UnderliesPaja Fm., Ritoque Fm.
OverliesCumbres Fm., Girón Fm., Los Medios Fm.
Thickness~470 m (1,540 ft)
Lithology
PrimarySandstone
OtherShale
Location
Coordinates [ ⚑ ] : 4°27′07″N 74°03′20″W / 4.45194°N 74.05556°W / 4.45194; -74.05556
RegionAltiplano Cundiboyacense
Eastern Ranges, Andes
Country Colombia
Type section
Named byWheeler
LocationMesa de Los Santos
Year defined1929
Coordinates [ ⚑ ] 4°27′07″N 74°03′20″W / 4.45194°N 74.05556°W / 4.45194; -74.05556
RegionBoyacá, Santander
Country Colombia

The Rosablanca Formation (Spanish: Formación Rosablanca, Kir) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes and the Middle Magdalena Basin. The formation consists of grey limestones, dolomites and shales with at the upper part sandstones. The formation dates to the Early Cretaceous period; Valanginian epoch and has a thickness of 425 metres (1,394 ft) in the valley of the Sogamoso River.

Definition

The formation was first defined by Wheeler in 1929.[1]

Description

Lithologies

The Rosablanca Formation is characterised by a sequence of grey limestones, dolomites and shales with a maximum thickness of 425 metres (1,394 ft) in the Sogamoso River valley.[1]

Stratigraphy and depositional environment

The Rosablanca Formation overlies the Arcabuco Formation and is overlain by the Ritoque Formation. The age has been estimated to be Valanginian. Stratigraphically, the formation is time equivalent with the Macanal Formation.[1]

Fossils

Fossils of the decapod crustacean Diaulax rosablanca have been found in and named after the Rosablanca Formation.[2] In 2019, fossils of brachiopodSellithyris elizabetha were described from the formation.[3] In 2020 remains of indeterminate pterosaurs were described from the formation, including pterodactyloids and non-Pteranodontian ornithocheiroids.[4] In 2005 the remains of Platychelyid sea turtle Notoemys zapatocaensis were described,[5] and in 2023 the limbs and shell elements of protostegids were described as some of the largest Early Cretaceous turtles.[6]

Outcrops

Rosablanca Formation is located in Santander Department
Rosablanca Formation
Type locality of the Rosablanca Formation in Santander

The Rosablanca Formation is found, apart from its type locality on the Mesa de Los Santos, Santander, in Boyacá and the Middle Magdalena Basin.

Regional correlations

See also

Featured article candidate Geology of the Eastern Hills
B-Class article Geology of the Ocetá Páramo
C-Class article Geology of the Altiplano Cundiboyacense

Notes and references

Notes

References

Bibliography

Maps

External links