Late Cretaceous-Cenozoic basin evolution and structural compartmentalization along the Middle Magdalena Valley to Eastern Cordillera transition (5-6°N), Colombian Andes

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records (Posters)

Presenting Author:

Natthakorn Konguthaithip

Authors:

Konguthaithip, Natthakorn¹, Horton, Brian K.², Parra, Mauricio³, Ketcham, Richard A.⁴, Mora, Andrès⁵, Malkowski, Matthew A⁶

(1) University of North Carolina at Chapel Hill, chapel hill, NORTH CAROLINA, USA, (2) University of Texas at Austin, Jackson School of Geosciences, Austin, TX, USA, (3) Institute of Energy and Environment, University of São Paulo, São Paulo, Brazil, (4) Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA, (5) ECOPETROL-Instituto Colombiano del Petroleo, Piedecuesta-Santander, Colombia, (6) Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA,

Abstract:

Topographic development of the northernmost Andes is recorded in Mesozoic to Cenozoic clastic basin fill along the structural transition between the Middle Magdalena Valley and Eastern Cordillera fold-thrust belt of Colombia. The Volador study area (5.5-6.0 °N) displays structures that pre-date and post-date an Eocene regional unconformity. The contrasting sedimentary successions above and below the unconformity define a major shift from organic-rich clastic marine deposition of regional extent to more localized coarse-grained fluvial and alluvial fan deposition with significant lateral variations. New detrital zircon U-Pb geochronological results reveal stepwise provenance changes in response to the shift from post-extensional (thermal) to foreland basin (flexural) subsidence. A latest Cretaceous to late Eocene shift from Andean basement and cratonic sources (eastern provenance) to principally forearc and magmatic arc sources (western provenance) points to early Andean shortening in western Colombia. This phase of basin reorganization is associated with exhumation of the Western Cordillera and igneous activity in the Central Cordillera magmatic arc during shortening-induced uplift and foreland conditions in the MMV. Western sources of detrital sediment persisted through Eocene unconformity development and west-verging thrust activity in the Eastern Cordillera, consistent with eastward propagation of topographic development during progressive Andean shortening.

Vitrinite reflectance results indicate spatial variations in burial of Cretaceous-Paleocene units related to compartmentalized deformation of different fault-bounded blocks and associated folding before and during unconformity development. The maximum depositional age (MDA) values from U-Pb results for stratigraphic units across the unconformity indicate a ca. 10 Myr hiatus of early to middle Eocene age. The MDA values also provide constraints for timing and potential geometry of upper crustal shortening and basin reorganization during early topographic growth of the Eastern Cordillera. Integration of detrital zircon U-Pb geochronology and vitrinite reflectance results with cross-cutting structural and stratigraphic relations indicates Cretaceous extension and post-extensional subsidence followed by Paleogene basin inversion during early Andean orogenesis. This study helps assess the kinematic sequence of deformation to identify linkages between uplift and sediment dispersal across the Middle Magdalena Valley and the flanking Eastern Cordillera and Central Cordillera during Andean topographic development, with attention to the role of tectonic inheritance in shaping the stratigraphic and structural history.