Basin Development and Tectonic History of the Llanos Basin, Colombia

Abstract

The Llanos basin lies east of the Eastern Cordillera in northeastern Colombia. Basin development commenced with a Triassic-Jurassic synrift megasequence related to the separation of North and South America in the Caribbean. Basin development continued in the Cretaceous as a back-arc megasequence behind the Andean subduction zone. Marine deposition was abruptly terminated during the early Maastrichtian due to final accretion of the Western Cordillera. The accretion of the Western Cordillera created the pre-Andean foreland basin megasequence (Paleocene-early Miocene), which covered the Magdalena Valley, Eastern Cordillera, and Llanos basin. This megasequence is dominated by fluviodeltaic strata. The overlying Andean foreland basin megasequence commenced with deformation in the Central Cordillera and Magdalena Valley. The Andean foreland basin megasequence also includes the Guayabo Formation, which is a classic molasse sequence shed from the developing mountains of the Eastern Cordillera as deformation moved eastward into the Llanos foothills. The deformation in the Llanos foothills is a combination of inversion of preexisting extensional faults and thin-skinned thrusting.