Journal of South American Earth Sciences 74 (2017) 1e26 Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames Structure and age of the Lower Magdalena Valley basin basement, northern Colombia: New reflection-seismic and U-Pb-Hf insights into the termination of the central andes against the Caribbean basin J. Alejandro Mora-Bohorquez a, *, Mauricio Ibanez-Mejia b, c, Onno Oncken d, Mario de Freitas e, Vickye Velez a, Andres Mesa f, Lina Serna a a Hocol S.A., Cra 7 No. 113-46, 16th Floor, Bogota, Colombia b Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA c Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA d Deutsches GeoForschungsZentrum GFZ, Telegranfenberg 14473, Potsdam, Germany e Caravela Energy, Bogota, Colombia f Horizonz Consulting, Bogota, Colombia article info abstract Article history: Detailed interpretations of reflection seismic data and new U-Pb and Hf isotope geochemistry in zircon, Received 8 July 2016 reveal that the basement of the Lower Magdalena Valley basin is the northward continuation of the Received in revised form basement terranes of the northern Central Cordillera, and thus that the Lower Magdalena experienced a 19 December 2016 similar pre-Cenozoic tectonic history as the latter. New U-Pb and Hf analyses of zircon from borehole Accepted 3 January 2017 basement samples retrieved in the basin show that the southeastern region consists of Permo-Triassic Available online 3 January 2017 (232-300Ma) metasediments, which were intruded by Late Cretaceous (75e89 Ma) granitoids. In the northern Central Cordillera, west of the Palestina Fault System, similar Permo-Triassic terranes are also Keywords: Lower Magdalena Valley intruded by Late Cretaceous felsic plutons and display ESE-WNW-trending structures. Therefore, our new San Jacinto fold belt data and analyses prove not only the extension of the Permo-Triassic Tahamí-Panzenú terrane into the Caribbean western Lower Magdalena, but also the along-strike continuity of the Upper Cretaceous magmatic arc of Reflection seismic the northern Central Cordillera, which includes the Antioquia Batholith and related plutons. Hf isotopic Basement analyses from the Upper Cretaceous Bonga pluton suggest that it intruded new crust with oceanic af- U-Pb and Hf isotope geochronology finity, which we interpret as the northern continuation of a Lower Cretaceous oceanic terrane (Que- bradagrande?) into the westernmost Lower Magdalena. Volcanic andesitic basement predominates in the northwestern Lower Magdalena while Cretaceous low-grade metamorphic rocks that correlate with similar terranes in the Sierra Nevada de Santa Marta and Guajira are dominant in the northeast, sug- gesting that the Tahamí-Panzenú terrane does not extend into the northern Lower Magdalena. Although the northeastern region of the Lower Magdalena has a similar NE-SW fabric as the San Lucas Ridge of the northeastern Central Cordillera and the Sierra Nevada de Santa Marta, lithologic and geochronologic data suggest that the San Lucas terrane terminates to the north against the northeastern Lower Magdalena, as the Palestina Fault System bends to the NE. The NE-SW trend of basement faults in the northeastern Lower Magdalena is probably inherited from the Jurassic rifting event which is responsible for the conspicuous fabric of surrounding terranes outcropping to the east of the Palestina Fault System, while the ESE-WNW trend in the western Lower Magdalena is inherited from a Late Cretaceous to Eocene strike-slip and extension episode that is widely recognized in the western Andean forearc from Ecuador to Colombia. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction The Lower Magdalena Valley basin is an Oligocene to recent * Corresponding author. basin of northwestern Colombia, located between two basement E-mail address: [email protected] (J.A. Mora-Bohorquez). massifs, the Central Cordillera and the Sierra Nevada de Santa http://dx.doi.org/10.1016/j.jsames.2017.01.001 0895-9811/© 2017 Elsevier Ltd. All rights reserved. 2 J.A. Mora-Bohorquez et al. / Journal of South American Earth Sciences 74 (2017) 1e26 Marta (Fig. 1). It is considered to be a forearc basin associated to the substratum of modern forearc basins such as the Lower Magdalena northern Colombia subduction complex, where the oceanic crust of remains a matter of controversy, primarily because the basin floor the Caribbean Plate subducts towards the ESE beneath the conti- is buried under a thick cover of post-Oligocene forearc sediments nental crust of the South American plate (Mantilla, 2007; Mantilla (Dickinson and Seely, 1979; Dickinson, 1995). Despite several re- et al., 2009; Bernal-Olaya et al., 2015a; Syracuse et al., 2016). The searchers having considered the basement beneath the Lower basin lies between the inactive magmatic arc of the northern Magdalena to be related to the continental basement exposed in Central Cordillera in the SE and the forearc high and the Southern the Central Cordillera and Sierra Nevada de Santa Marta (Duque- Caribbean accretionary prism to the west. The nature of the Caro, 1979; Reyes et al., 2000; Montes et al., 2010), the paucity of Fig. 1. Geological map of northern Colombia (Gomez et al., 2007), highlighting basement terranes and pre-Tertiary sedimentary units and integrating subsurface basement maps in depth (meters) of the LMV and Guajira. Colored circles are wells that drilled into the basement and have basic rock descriptions; previous and new geochronological data from the basement is depicted. CAF: Cauca-Almaguer fault; ESF: Espiritu Santo fault; SJF: San Jeronimo Fault; PFS: Palestina Fault System; UF: Uramita Fault; SF: Sinu fault; SMF: Santa Marta fault; SL: Sevilla Lineament; OF: Oca Fault; CuF: Cuisa Fault; CRB: Cesar-Rancheria basin; PR: Perija Ridge; EC: Eastern Cordillera. Inset: Tectonic map of northwestern South America with topography and bathymetry, showing the location of the Lower Magdalena Valley basin (LMV) and the Sinú-San Jacinto fold belt (SSJFB). Present-day tectonic plate motions are shown in yellow (after Trenkamp et al., 2002). WC: Western Cordillera; CC: Central Cordillera; EC: Eastern Cordillera; RFS: Romeral Fault System; PFS: Palestina Fault System; BF: Bucaramanga Fault; SMF: Santa Marta Fault; OF: Oca Fault. J.A. Mora-Bohorquez et al. / Journal of South American Earth Sciences 74 (2017) 1e26 3 basement data from the Lower Magdalena has precluded the Paleocene times and that it is represented by localized and poorly development of robust arguments in support of such correlations. preserved serpentinized peridotites outcropping in northern Cen- However, because the Lower Magdalena Valley basin holds tral Cordillera and southern LMV. The oceanic domains of the WC important hydrocarbon reserves at different stratigraphic levels are thought to have accreted during the Mesozoic, along the RFS (ICP , 2000), the last two decades have seen a considerable increase (Barrero et al., 1969; Barrero, 1979; Etayo et al., 1983; Restrepo and in exploratory drilling and geophysical tools applied to this basin Toussaint, 1988; Cediel et al., 2003). In the northern part of the such as gravimetry, magnetics and reflection seismic. These new country, where the influence of the Caribbean plate and collision of data have provided valuable information about the basement the Choco-Panam a block has continued into the Cenozoic, the structure of the Lower Magdalena and have allowed improved Central and Western cordilleras terminate as they plunge to the regional correlations, structural evaluation and mapping to be north and get progressively buried under Tertiary sediments of the conducted (Reyes et al., 2000; Ceron et al., 2007; this study). In Lower Magdalena Valley basin (LMV) and the Sinú and San Jacinto spite of the numerous oil exploration wells that have reached the fold belts. The LMV is limited to the east and northeast by the left- Lower Magdalena basement during the past few decades, very few lateral, strike-slip Santa Marta-Bucaramanga fault system, and localized analyses have been carried out to provide robust composed of the Santa Marta fault system (SMF) in the north and of geochronologic and geochemical constraints on the type and age of the Bucaramanga Fault system (BF) in the south (Fig. 1). While a the basement that underlies it (Montes et al., 2010; Silva et al., basement high (Cachira) in the northernmost Central Cordillera 2017). Considering the unique location of the Lower Magdalena in (CC) is separating the LMV from the Middle Magdalena Valley basin northwestern South America, where several tectonic plates have (MMV), the Santa Marta-Bucaramanga fault system is separating it been complexly interacting through time, new information about from the Cesar-Ranchería (CR) Basin and from the Sierra Nevada de its basement structure, type and age is relevant to understanding Santa Marta (SNSM, Fig. 1). To the southeast and south, the LMV is the formation and evolution of this important hydrocarbon- limited by the northernmost termination of the CC, the Palestina producing basin in Colombia. Fault System (PFS) and the San Lucas Ridge. Its western boundary The aim of this paper is to present new information on the has been considered to be the inferred extension to the north of the structure and age of the basement of the Lower Magdalena Valley trace of the RFS (Romeral, Duque-Caro,