The Middle Magdalena Valley basin (MMVB) is a roughly N-S oriented intermontane basin that separates the Central and Eastern Cordilleras. The structural evolution of the basin involved both extensional and compressional tectonics. During the late Triassic to early Jurassic period the opening of the proto-Atlantic and the separation of South America and Africa set up east-west extensional stresses in the Precambrian continental block. This resulted in the formation of a rift structure in central Colombia.

This resulted in the formation of a rift structure in central Colombia. The syn-rift infill is represented by fluvial and lacustrine sandstones and shales (Giron and Tambor Formations) overlain by marine limestone and shale (Rosablanca and Paja Formations). By the Early Aptian the extension had decreased and post-rift thermal subsidence began during which marine limestone and shale of the Tablazo, El Salto and La Luna Formations and sandstones of the Umir Formation were deposited.

Three main compressive phases are recognised in the basin: Late Cretaceous to Paleocene, early to middle Eocene and Oligocene. These compressive phases reactivated the earlier extensional faults and resulted in the formation of the Eastern and Central Cordilleras. Sedimentation throughout the uppermost Cretaceous and Tertiary episodes was dominated by marginal marine and fluvial sandstone and shale.

The main source rocks in the MMVB are the marine limestone and shale of the Tablazo to La Luna Formations. The La Luna Formation especially is regionally extensive and ranks as ‘world class’ in terms of quality and quantity. Most of the fields found to date in the MMVB produce oil from Tertiary sandstone reservoirs. However, fractured carbonates in the Cretaceous also produce locally but these are a relatively under-explored target in the basin.