Rosablanca Formation

The Rosablanca Formation (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 m in the valley of the Sogamoso River.

Definition
The formation was first defined by Wheeler in 1929.

Lithologies
The Rosablanca Formation is characterised by a sequence of grey limestones, dolomites and shales with a maximum thickness of 425 m in the Sogamoso River valley.

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.

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

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