Role Of Extensional Structures In The Development Of The Middle Magdalena Valley Basin – Colombia

The MMVB was developed through different tectonic stages related with the interaction of the tectonic plates at the Northwestern corner of South America. During Jurassic and early Cretaceous the MMVB went through rift stage that evolved to an aulacogen. Many of the structures related with the extensional phase of the MMVB were modified after the Tertiary tectonics, however the rift structures in the northern portion of the basin are still well preserved. The northern part of the MMVB is a monocline dipping toward the southeast that represents a half graben inside the rift. The monocline structure is dipping south-eastern, as is the direction, where isopach contours thicken. Most of the structures present at the area are normal and reverse faults of variable vergence, oriented in northeast-southwest direction. Kinematics of the rift seemed to be rotational during the syn-rift accumulation and non-rotational during post-rift sedimentation. Most of the faults remaining the rift structure were inverted after compressional tectonics that started at Late Cretaceous. According the model proposed by Hayward and Graham (1989), inversion seemed to be mild in the northern MMVB area. Transpresion caused by the oblique collision of the Western Cordillera, added a strike-slip component to the reactivation process, through the clockwise rotation of the blocks.