Guaduas Formation

The Guaduas Formation (Formación Guaduas, K2P1G, K2E1G, KPgg, KTg, TKg, Ktg) is a geological formation of the Middle Magdalena Basin and the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The predominantly shale with coalbed formation dates to the Late Cretaceous and Paleogene periods; Maastrichtian-Paleocene epochs, and has a maximum thickness of 1090 m. Fossils of Coussapoa camargoi, Ficus andrewsi, Berhamniphyllum sp. and Archaeopaliurus boyacensis have been found in coalbeds in Zipaquirá and Tasco, Boyacá.

Etymology
The formation was first described by Hettner in 1894 and named in 1931 by Hubach after Guaduas, Cundinamarca, former northern territory of the Panche.

Lithologies
The Guaduas Formation consists mainly of shales with intercalated sandstone beds. The formation contains coalbeds that are widely explored in the area. Fossil remains of Coussapoa camargoi, Ficus andrewsi, Berhamniphyllum sp. and Archaeopaliurus boyacensis have been found in coalbeds in Zipaquirá and Tasco, Boyacá.

Stratigraphy and depositional environment
The Guaduas Formation unconformably overlies the Arenisca Labor-Tierna Formation of the Guadalupe Group and is overlain by the Cacho Formation. The age has been estimated to be Upper Maastrichtian-Lower Paleocene, spanning the K-T boundary. The Guaduas Formation is thicker in Cundinamarca than in Boyacá. This has been explained by a decrease in subsidence and a higher amount of erosion in the northern area of original deposition. The lateral thickness variations are thought to be the result of the movement of the Soapaga Fault. The formation has been deposited in a coastal plain setting.

Outcrops
The Guaduas Formation is apart from its type locality, found in the Eastern Hills of Bogotá, the Ocetá Páramo and many other locations in the Eastern Ranges, such as Granada, the Dintel Synclinal north of Facatativá, the Suesca Synclinal, east of Junín, and surrounding Lake Tota. The northeast-southwest Canocas Fault crosscuts the Guaduas Formation near San Cayetano. The synclinals of the Río Frío, Neusa, Zipaquirá, Checua-Lenguazaque, Sesquilé, Sisga, Subachoque, Teusacá and Usme and Soacha are composed of the Guaduas Formation. The Suba Hills are entirely composed of the Guaduas Formation. The formation also has outcrops in the Sumapaz Páramo.