In this thesis I used a regional geological and geophysical dataset to reconstruct the Late Cretaceous to Recent evolution of the Lower Magdalena Valley basin and San Jacinto fold belt of NW Colombia. My detailed interpretations of reflection seismic data and new geochronology analyses reveal that the Lower Magdalena basement is the northward continuation of the basement terranes of the northern Central Cordillera, consisting of Permo-Triassic metasediments, which were intruded by Late Cretaceous granitoids. Structural analyses suggest that the NE-SW trend of basement faults in the northeastern Lower Magdalena is inherited from a Jurassic rifting event, while the ESE-WNW trend in the western part is inherited from a Late Cretaceous to Eocene strike-slip and extension episode. The Upper Cretaceous to lower Eocene sediments preserved in the present day San Jacinto fold belt were deposited in a forearc marine basin formed by the oblique convergence between the Caribbean and the South American plates. A lower to middle Eocene angular unconformity at the top of the San Cayetano sequence, the termination of the activity of the Romeral Fault system and the cessation of arc magmatism are interpreted to indicate the onset of low-angle subduction of the Caribbean plateau beneath South America, which occurred between 56 and 43 Ma. Flat subduction of the plateau has continued to the present and would be the main cause of amagmatic post-Eocene deposition and formation of the Lower Magdalena Valley basin. After the collapse of a pre-Oligocene magmatic arc, late Oligocene to early Miocene fault-controlled subsidence allowed initial infill of the Lower Magdalena with relatively low sedimentation rates. Extensional reactivation of inherited, pre-Oligocene basement faults was crucial for the tectonic segmentation of the basin with the formation of its two depocenters (Plato and San Jorge). Oligocene to early Miocene uplift of Andean terranes made possible the connection of the Lower and Middle Magdalena valleys, and the formation of the most important Colombian drainage system (Magdalena River system). This drainage system started delivering high volumes of sediment in middle Miocene times, as fault-controlled subsidence was gradually replaced by sagging due to increased sedimentary load. Such an increase in sedimentation delivering great sediment volumes to the trench, caused the formation of forearc highs in San Jacinto and of an accretionary prism farther to the west. These results highlight the fundamental role of changes in plate kinematics, of the inherited basement structure and of sediment flux on the evolution of forearc basins such as Lower Magdalena and San Jacinto. Based on my interpretations and results about the evolution of the Lower Magdalena and San Jacinto, a three-dimensional model of the Lower Magdalena Valley basin was built from seismic and well data, and used to reconstruct the thermal and maturation history of the basin. I reconstructed the stratal architecture of the basin, implemented within the model episodes of uplift and erosion, and built a geothermal gradient map, which was used to construct heat flow maps for 3-D modeling. Model results indicate that the onset of hydrocarbon generation occurred at ~15 Ma (middle Miocene) for upper Oligocene to lower Miocene hydrocarbon source rocks in the northern part of the basin (Plato depocenter), while younger, lower Miocene sources started generating at ~ 9 Ma (middle-late Miocene). Maturation was influenced by sedimentation at very high rates of thick, deep marine to deltaic, Oligocene to upper Miocene sequences. Late Miocene generation was interrupted by shortening and uplift events at Pliocene (4-3 Ma) and Pleistocene times, though it appears to be ongoing in main depocenters. Low to fair source rock quality appears to be compensated by high thicknesses of the Oligocene to lower Miocene sources, which would still be generating below 3,350 m (11,000 ft) in the main pod of active source rock in the northern Lower Magdalena (Plato depocenter). By contrast, the effects of shortening pulses and low heat flow would have inhibited maturation of Oligocene to lower Miocene source rocks in the San Jorge graben of the southern Lower Magdalena, suggesting the need of additional hydrocarbon sources to explain the dry gas occurrences in that part of the basin. Proposed additional sources are pre-Oligocene units preserved in the western San Jorge depocenter, and biogenic generation. The results of this thesis provide new insights into the controls of plate tectonics and basin evolution on petroleum systems.
