page_title: Eastern Hills, Bogotá
section_title: Geology
hierarchical_section_title: Eastern Hills, Bogotá / Geology
caption_attribution_description: English: Sample of the organic shale of the Chipaque Formation, from a quarry along the road to Villavicencio between Chipaque and Cáqueza, Cundinamarca, Colombia
context_page_description: The Eastern Hills are a chain of hills forming the eastern natural boundary of the Colombian capital Bogotá. They are part of the Altiplano Cundiboyacense, the high plateau of the Eastern Ranges of the Colombian Andes. The Eastern Hills are bordered by the Chingaza National Natural Park to the east, the Bogotá savanna to the west and north, and the Sumapaz Páramo to the south. The north-northeast to south-southwest trending mountain chain is 52 kilometres long and its width varies from 0.4 to 8 kilometres. The highest hilltops rise to 3,600 metres over the western flatlands at 2,600 metres. The Torca River at the border with Chía in the north, the boquerón Chipaque to the south and the valley of the Teusacá River to the east are the hydrographic limits of the Eastern Hills.
  Geologically, the Eastern Hills are the result of the westward compression along the Bogotá Fault, that thrusted the lower Upper Cretaceous rocks of the Chipaque Formation and Guadalupe Group onto the latest Cretaceous to Eocene sequence of the Guaduas, Bogotá, Cacho and Regadera Formations.
context_section_description: The rocks forming the Eastern Hills range in age from Late Cretaceous to Paleogene and are covered by sub-recent sediments of the Pleistocene and Holocene. The contact between the Maastrichtian to Lower Paleocene Guaduas and Late Paleocene Cacho Formations is discordant, indicating the first uplift of the Andes. Between the Eocene and Pleistocene a hiatus is present, where the Pleistocene formations are followed by Holocene unconsolidated sediments.
  The Cenomanian–Turonian Chipaque Formation got its name from the village Chipaque and is the oldest stratigraphical unit outcropping in the eastern flank of the Eastern Hills. It comprises laminated organic to highly organic shales and mudstones with intercalated sandstone beds. The overlying Guadalupe Group, of Campanian to Maastrichtian age, consists of four formations, from base to top: Arenisca Dura, Plaeners, Arenisca de Labor, and Arenisca Tierna. Some authors define the Guadalupe Group as a formation and call the individual formations, members. The thickness of the Guadalupe Group in its type localities Guadalupe and El Cable Hills is 750 metres (2,460 ft). The competent hilltops of the Eastern Hills are represented by the resistant members of the Guadalupe Group; in the northern parts of the Cerros Orientales they comprise the Labor and Tierna members and are in the southern area represented by the Arenisca Dura.
  Concordantly overlying the Guadalupe Group is the Maastrichtian to Early Paleocene Guaduas Formation, composed of well-laminated compacted grey shales and calcitic claystones with sandstone banks and in the lower parts of the stratigraphical sequence numerous coal beds. In the synclinal of the Bogotá savanna, the thickness of Guaduas varies between 250 and 1,200 metres (820 and 3,940 ft). The Late Paleocene Cacho Formation, a relatively thin 50-to-400-metre (160 to 1,310 ft) stratigraphical unit following the Guaduas Formation, white, yellow and reddish in colour, is represented by thick sandstone banks with intercalations of thin shale beds.
  The Bogotá Formation, named after the capital, is a Paleocene to Lower Eocene argillaceous unit, concordantly overlying the lower Paleogene sequence. The formation is composed of grey, purple and red shales with micaceous sandstone beds towards the top of the stratigraphical unit. The thickness in the subsurface of the Bogotá savanna ranges from 800 to 2,000 metres (2,600 to 6,600 ft) and outcrops at the edges of the flatlands. In this formation fossils of the ungulate Etayoa bacatensis, named after the name for the savanna and its main settlement in present-day Funza, used by the native Muisca; Bacatá, have been found. The estimated size of the South American hoofed mammal was that of a dog. Other fossilised fragments found in the Bogotá Formation are molds of Stephania palaeosudamericana and Menispina evidens.
  Discordantly overlying the Lower Eocene is the Middle Eocene Regadera Formation, consisting of quartzitic and feldspar-rich thick medium- to coarse-grained to conglomeratic sandstone beds intercalated with thin pink claystones. The total thickness of the Regadera unit is very variable throughout the area. Following the Regadera Formation is the discordant Late Eocene Usme Formation, named after the locality in southeastern Bogotá, for the most part located in the Eastern Hills. The unit with a total thickness of 125 metres (410 ft) consists of a lower member composed of grey shales with occasional fine-grained sandstone layers and an upper member of coarse-grained quartzarenites and conglomerates. The Usme Formation represents the last Paleogene stratigraphic unit before the hiatus of approximately 30–35 million years.
  While the Bogotá savanna contains two other formations; the Pliocene Tilatá and Plio-Pleistocene Sabana formations, the Eastern Hills lack these late Neogene stratigraphical units. The basal unit of the Quaternary sequence is the fluvio-lacustrine Subachoque Formation, present in the subsurface of the foreland area of the Eastern Hills. The Tunjuelo Formation, named after the Tunjuelo River that is
caption: An example of the organic shale of the Chipaque Formation
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