[2] The basin, covering an area of 34,000 square kilometres (13,000 sq mi), is situated in the departments of Santander, Boyacá, Cundinamarca and Tolima.

[3] To the south, it terminates against the Upper Magdalena Valley, which consists of the Girardot and Neiva Sub-basins where the Central and Eastern Ranges converge.

[4] The basin is an important producer of oil in Colombia, with main fields Yariguí-Cantagallo, Moriche, Casabe, La Cira-Infantas, Velásquez, Santos, Palagua, Teca, Payoa and Lisama.

[3][4] In the Paleocene, the rate of subduction increased causing the marginal Colombian Sea to close and the Baudo-Island Arc to collide with the South American continent.

[2] The major surface structures of the Middle Magdalena Basin are asymmetric synclines and basement cored anticlines, which formed as a result of thrusting from the Eastern and Central Ranges.

[2] The basement of these sequences is Pre-Mesozoic metaclastics and sediments which are now exposed on the surface of the Central Cordillera as a result of its deformation and uplift.

[2] In the Early Cretaceous, sea level began to rise and formed a shallow marine environment with siltstone and shale deposits of the Cumbre Formation.

[4] The La Luna Formation represents a maximum flooding surface with deep marine deposits of limestone, chert, and shale.

[2] Sea level then began to fall, returning the environment to shallow marine with deposition of the Umir Formation of shales and sandstones.

[2] Similar to the Real Group, the final subsequence is the Pliocene Mesa Formation, which is composed of sandstones and conglomerates deposited due to the Eastern Ranges uplift.

[4] The uppermost sedimentary rocks of the basin are Pleistocene alluvial fan deposits, overlain by Holocene sediments of the Magdalena River.

[4] The primary reservoirs in the Middle Magdalena Basin are fluvial sandstones and conglomerates from the Churro and Chuspas Groups, which have 20 to 25% porosity and 0.5 to 1 D permeability.

[4] The main source of hydrocarbons is the La Luna limestone, with a Total Organic Carbon (TOC) content of 3 to 4% and Type II marine kerogen, sealed by overlying Eocene shales.

[12] Current exploration is focused in the southern area of the basin, where heavy amounts of faulting could house potential hydrocarbons.