Tectonic Controls on Cenozoic Foreland Basin Development in The

EAGE Basin Research (2010) 22, 874–903, doi: 10.1111/j.1365-2117.2009.00459.x Tectonic controls on Cenozoic foreland basin development in the north-eastern Andes, Colombia Mauricio Parra,n Andre´ s Mora,n,w Carlos Jaramillo,z Vladimir Torres,w Gerold Zeilingern and Manfred R. Streckern nInstitut fˇr Geowissenschaften, UniversitÌt Potsdam, Potsdam, Germany wInstituto Colombiano del Petro¤leo, Ecopetrol Bucaramanga, Colombia zSmithsonianTropical Research Institute, Balboa, Ancon, Republic of Panama ABSTRACT In order to evaluate the relationship between thrust loading and sedimentary facies evolution, we analyse the progradation of £uvial coarse-grained deposits in the retroarc foreland basin system of the northern Andes of Colombia.We compare the observed sedimentary facies distribution with the calculated one-dimensional (1D) Eocene to Quaternary sediment-accumulation rates in the Medina wedge-top basin andwith a three-dimensional (3D) sedimentary budget based on the interpretation of 1800km of industry-style seismic re£ection pro¢les and borehole data. Age constraints are derived from a new chronostratigraphic framework based on extensive fossil palynological assemblages.The sedimentological data from the Medina Basin reveal rapid accumulation of £uvial and lacustrine sediments at rates of up to 500 m my À1 during the Miocene. Provenance data based on gravel petrography and paleocurrents reveal that theseMiocene £uvial systemswere sourced from Upper Cretaceous and Paleocene sedimentary units exposed to the west in the Eastern Cordillera. Peak sediment-accumulation rates in the upper Carbonera Formation and the Guayabo Group occur during episodes of coarse-grained facies progradation in the early and late Miocene proximal foredeep.Weinterpret this positive correlation between sediment accumulation and gravel deposition as the direct consequence of thrust activityalong theServita¤ ^Lengupa¤ faults.This contrasts with one class of models relating gravel progradation in more distal portions of foreland basin systems to episodes of tectonic quiescence. INTRODUCTION (e.g., Burbank, 1992); (2) an increase in the e⁄ciency of erosion triggered byglobal climatic oscillations(e.g., Mol- Grain-size trends and the basinwide distribution of nar, 2004) or by orographic e¡ects (Ho¡man & Grotzinger, coarse-grained strata in foreland basins have been used to 1993; Masek etal.,1994); (3) tectonic quiescence favouring a interpret the tectonic and climate-related controls on fore- decrease in subsidence and progradation of coarse- land basin accumulation (e.g., Flemings & Jordan, 1990; grained sediments to the distal part of the basin(e.g.,Hel- Heller & Paola, 1992; Paola et al., 1992). In general, the ba- ler et al., 1988; Flemings & Jordan, 1990; Burbank, 1992; sin’s stratigraphic architecture is a function of the relative Heller & Paola, 1992); and (4) increase of erosion rates and importance between sediment discharge and the rate of sediment discharge due to a decrease in the resistance to creation of accommodation space (e.g., Schlunegger et al., erosion of the source areas, (e.g., DeCelles et al., 1991; Car- 2007). Multiple mechanisms have been proposed to ac- roll et al., 2006). Numerical modelling has been used to count for the progradation of coarse-grained sediments evaluate the role of each of these controlling factors on in foreland basins: (1) uplift of the source areas by either the overall distribution of coarse-grained facies in basins increased tectonic activity in the fold-and-thrust belt with di¡erent £exural rigidities (e.g., Flemings & Jordan, (e.g., Burbank et al., 1988; Schlunegger et al., 1997a, b; Hor- 1989; Flemings & Jordan, 1990; Sinclair et al., 1991; Paola ton et al., 2004) or erosionally driven isostatic rebound etal.,1992). A critical factor determining a basin’s sedimentary response to the aforementioned changes, however, in- Correspondence: Mauricio Parra, Institut fˇr Geowissenschaf- volves an improved knowledge of the time scales over ten, Universitt Potsdam, Karl-Liebknecht-Strasse 24, Haus 27, which variations in the external forcings occur compared 14476 Potsdam, Germany. E-mail: [email protected] with an inherent background level of erosional and deposi- potsdam.de tional processes in the basin. While considerable debate Present address: Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, has existed on the role of each of these factors in the distal TX 7871-0254, USA portion of foreland basins (Burbanketal.,1988; Helleretal., r 2010 The Authors 874 Basin Research r 2010 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists Controls on foreland-basin sedimentation, Colombia 1988), combined ¢eld evidence and numerical models have Medina Basin with a three-dimensional (3D) sedimentary demonstrated that coarse-grained sediments accumulate budget for an area of 5000 km2, based on the interpreta- in the proximal part of foreland basins, irrespective of pre- tion of 1800 km of industry-style depth-migrated, mul- cise tectonic and climatic regimes (e.g., Flemings & Jordan, tichannel seismicre£ectionpro¢les andborehole datatied 1990; Jones et al., 2004). These inherent characteristics to a new biostratigraphic framework. Importantly,our data complicate a rigorous assessment of the role exerted by show that episodes of coarse-grained sedimentation are each of these competing factors on the accumulation of coeval with rapid subsidence throughout the basin history, coarse-grained sediments in proximal sectors of foreland illustrating that increased tectonic activity in the Eastern basins. Provided su⁄cient temporal control, tectonically Cordillera has exerted a dominant control on the geome- and climatically controlled forcing factors re£ected in de- try and pattern of sediment distribution. Our work has im- positional characteristics may be deconvolved for an im- plications for the understanding of the response time of proved understanding of the spatiotemporal trends in surface processes to tectonic forcing. tectonic and sedimentary processes of convergent orogenic belts. Such is the case in the northern Andes, where contractional deformation and orogenic growth have been linked with reactivated long-lived basement anisotropies GEOLOGIC BACKGROUND (Mora et al., 2008; Parra et al., 2009b) that have fundamen- Geodynamic and structural setting tally in£uenced the loci of tectonic deformation, erosion and sediment dispersal. TheMedinaBasinisa90Â 25 km wedge-top depocentre In the eastern Andes of central Colombia, the sedimen- located atop the most external east-verging thrust- tary record of subduction-related orogenesis is preserved sheet along the eastern margin of the Eastern Cordillera in Late Cretaceous to Cenozoic basins that extend east of of the Colombian Andes (Fig.1).The Eastern Cordillera is the Central Cordillera, the present-day magmatic arc the easternmost branch of a retroarc fold-and-thrust belt (Fig.1).Mesozoic rifting occurredin the areapresentlyoc- related to Late Cretaceous to Cenozoic shortening, result- cupied by the Eastern Cordillera north of 21N(e.g., ing from the interaction between the Nazca, Caribbean Campbell & Bˇrgl,1965; Mora et al., 2006; Sarmiento-Ro- and South American plates (e.g., Cooperet al.,1995;Taboa- jas etal., 2006). In the course of Cenozoic contraction, ma- da et al., 2000; Go¤ mez et al., 2005; Parra et al., 2009a). Late jor inherited extensional faults became the locus for Cretaceous ( 80 Ma) oblique accretion of relicts of a Pa- preferential accommodation of thrust loading and defor- ci¢c oceanic plateau (e.g., Kerr & Tarney,2005;Vallejo etal., mation (Mora et al., 2006, 2008; Parra et al., 2009a, b), and 2006) constituted the Western Cordillera and triggered therefore prevented a signi¢cant eastward advance of the crustal shortening and thickening and initial mountain orogenic front.This con¢guration has led to the unroo¢ng building within the present-day Central Cordillera (e.g., of progressively older structural levels from the eastern Cooper et al., 1995). The tectonic loading exerted by this £ank of the Eastern Cordillera and resulted in the coeval range created a foreland-basin system, east of the Central accumulation of sediments in the Llanos Basin to the east. Cordillera (Cooper et al., 1995; Go¤ mez et al., 2005). Subse- Plio^Pleistocene eastward advance of the foreland fold- quent deformation compartmentalized the foreland basin and-thrust system to the present-day frontal structure in a nonsystematic manner due to the selective reactivation (Mora, 2007) has incorporated only the proximal part of of crustal anisotropies inherited from Proterozoic and Pa- this Mio^Pliocene foredeep into the orogen in the form laeozoic collision and subduction episodes (e.g., Restrepo- of the Medina wedge-top basin. This exhumed foredeep Pace et al., 1997; Cediel et al., 2003, and references therein), o¡ers a unique,yet areallylimited locationwhere the sedi- and more importantly extensional structures generated mentary record of the late stages of Andean uplift and ex- during Mesozoic rifting (e.g., Cooper et al., 1995; Mora humation are well exposed. However, because of the et al., 2006; Sarmiento-Rojas et al., 2006). In this context, absence of radiometrically datable minerals and the pau- initial middle Eocene tectonic inversion of Mesozoic rift city of published biostratigraphic markers, the sedimen- basins in the area of the present-day Eastern

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