Structure and Tectonics of the Central Segment of the Eastern Cordillera of Colombia

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Journal of South American Earth Sciences xxx (2006) xxx–xxx www.elsevier.com/locate/jsames

Structure and tectonics of the central segment of the Eastern Cordillera of Colombia

Martı´n Corte´s a,*, Bernard Colletta b, Jacques Angelier a

a Laboratoire de Tectonique, Universite´ P and M. Curie Case 129, T56-E2, 4 Place Jussieu, 75252 Paris Cedex 05, France b Institut Franc¸ais du Pe´trole, 1 et 4 Avenue de Bois-Pre´au 92852, Rueil-Malmaison, Cedex, France

Received 1 October 2004; accepted 1 February 2006

Abstract

In the Eastern Cordillera of Colombia, a new structural model constrained by field data, paleontologic determinations, and interpre- tations of seismic reflection profiles is proposed. The model implies 70 km of shortening, including reactivation of basement structures as inverse faults in both flanks of the chain. These faults propagated within the lower Cretaceous strata, inducing passively rooted and transported thrust sheets as the successive basement faults were reactivated. Two structural styles are identified in the western flank: (1) positive flower structures in a transpressive regime, which affected rocks older than upper Paleocene and were unconformably covered by post–late Paleocene sediments, and (2) compressive structures during the late Miocene–Recent Andean phase. Presently, WNW-ESE compression reactivates Late Paleocene structures, which locally affect Andean trends. In the western margin of the Eastern Cordillera, the Cambao thrust takes up most displacement, whereas the Bituima fault takes only a minor part. To the south, this relationship revers- es, suggesting complementary behavior by the Bituima and Cambao faults, as well as a transfer zone. This suggestion explains the southward termination of the Guaduas syncline as a structure related to the Cambao fault, whereas the Bituima fault increases its displacement southward, generating the Girardot foldbelt that takes over the structural position of the Guaduas syncline.

Keywords: Northern Andes; Eastern Cordillera; Structure; Colombia

Resumen

En la Cordillera Oriental de Colombia, se propone un nuevo modelo estructural basado en datos de campo, dataciones paleontolo´gicas e interpretaciońdelıńeas sı´smicas. El modelo implica 70 km de acortamiento, incluyendo estructuras del basamento reactivadas como fallas inversas en ambos flancos de la cadena. Estas fallas se propagaron dentro de la secuencia del Cretaćico Inferior, induciendo escamas de cabalgamiento que fueron pasivamente rotadas y transportadas cuando se reactivaban las fallas de basamento. En el flanco occidental de la Cordillera Oriental se identificaron dos estilos estructurales: (1) estructuras transpresivas en flor positiva afectaron rocas anteriores al Paleoceno Superior y estań cubiertas por sedimentos posteriores, y (2) estructuras compresivas de la fase Andina del Mioceno al Reciente. El re´gimen actual en compresioń WNW-ESE reactivo´ las estructuras Paleocenas, las cuales cortan las estructuras de la fase Andina. En la margen oeste de la Cordillera Oriental, la falla de Cambao acomoda la mayor parte del desplazamiento mientras que la falla de Bituima solo una parte menor. Hacia el sur esta relacioń se invierte, sugiriendo la presencia de una zona de transferencia. Esto explica porque el Sinclinal de Guaduas desaparece al sur, ya que es una estructura asociada a la falla de Cambao, mientras que la falla de Bituima aumenta su desplazamiento, generando el Cinturoń plegado de Girardot, que toma la posicioń estructural del Sinclinal de Guaduas. 2006 Elsevier Ltd. All rights reserved.

Palabras claves: Andes del Norte; Cordillera Oriental; Estructura; Colombia

* Corresponding author. Present address: Corporacio´n Geolo´gica Ares, Bogota´, Colombia. Fax: +571 3101736. E-mail address: [email protected] (M. Corte´s).

Please cite this article as: Martı´n Corte´s et al., Structure and tectonics of the central segment of the Eastern ..., Journal of South American Earth Sciences (2006), doi:10.1016/j.jsames.2006.07.004. ARTICLE IN PRESS

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1. Introduction phologic units, the northern Andes are composed of oceanic and continental domains. Oceanic terrains in 1.1. Structural and tectonic setting Colombia include the Baudo Range, Western Cordillera, and the western flank of the Central Cordillera (Fig. 1). The northern Andes in Colombia resulted from a com- Gravimetric data, geochemical analyses, and stratigraphic plex interaction between the NW corner of the continental studies support this idea (Barrero, 1979; Case et al., 1971, plate of South America and the oceanic Caribbean and 1973; Duque-Caro, 1990; Etayo-Serna et al., 1982). The Nazca plates (Fig. 1). Presently, this plate configuration Romeral-Cauca fault zone (Figs. 1 and 2) separates this defines a triple junction that accommodates permanent oceanic complex from the continental deformed basement strain in the Panama-Choco block and northern Andes under the eastern flank of the Central and Eastern cordill- (Ego et al., 1996; Corte´s, 2004). eras (Fig. 2). The present Andean system in Colombia thus resulted The Eastern Cordillera of Colombia (EC) is a double- from a continuous process of subduction, obduction, and verging mountain system bounded by major inverse faults accretion of oceanic terranes in the western and northwest- that locally involve crystalline and metamorphic basement ern margins of Colombia since the Paleozoic (Barrero, rocks, Precambrian–Lower Paleozoic in age, as well as 1979; Bourgois et al., 1982, 1987; Etayo-Serna et al., Upper Paleozoic–Cenozoic sedimentary and volcanic 1982; Alvarez, 1983; Duque-Caro, 1984, 1990; McCourt sequences. et al., 1984; Resprepo-Pace, 1995). As a result, the northern Andes are composed of three main mountain belts: the 1.2. General evolution of the EC and northern Andes Western, Central, and Eastern cordilleras. Other isolated topographic elevations in the northern Andes include the The Mesozoic to present tectonic evolution of the north- Sierra Nevada de Santa Marta and the Baudo and Maca- ern Andes, particularly of the EC, may be summarized as rena ranges (Fig. 1). Considering the origin of these mor- follows: Continuous subduction of the Farallon plate

Fig. 1. Major tectonic and structural features around the northern Andes. PCB, Panama-Choco block; CC, Central Cordillera; WC, Western Cordillera; EC, Eastern Cordillera; RF, Romeral fault; BR, Baudo range; SN, Santa Marta range; PR, Perija range; SM, Santander, MA, Merida Andes; BF, Bocono´ fault; GF, Guaicaramo fault; SMF, Santa Maria fault; AG, Algeciras fault; MR, Macarena range. Plate velocity vectors in mm/yr with respect to South America after Trenkamp et al. (2002).

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Fig. 2. Study area in the central segment of the EC of Colombia. Modified after Cediel and Caćeres (1988), Raasveldt (1956), and Raasveldt and Carvajal (1957). GS, Guaduas syncline; SB, Sabana de Bogota; GFB, Giradot foldbelt. beneath the NW border of South America during the Late phase attained 2b for the Late Cretaceous (He´brard, 1985; Paleozoic–Early Cretaceous was accompanied by large, Fabre, 1987; Sarmiento, 2001) and allowed deposition of a granite-type intrusions in the modern Central Cordillera, 6 km thick shallow marine sequence in the EC basin (Coo- Magdalena Valley, and EC (Resprepo-Pace, 1995). During per et al., 1995; Sarmiento, 2001). the Early Cretaceous, a backarc tectonic setting dominated During the Maastrichtian–Early Paleocene, a new tec- the area of the EC, accounting for crustal thinning of tonic pulse related to accretion of oceanic terranes of the approximately 1.3b and subcrustal thinning of 2b, mainly Western Cordillera along the Romeral fault system (Barre- related to tectonic subsidence (He´brard, 1985; Fabre, ro, 1979). As a consequence, uplifting in the Central Cor- 1987; Sarmiento, 2001). This phase of extension probably dillera (Gomez et al., 2003) and generation of positive was enhanced by the opening of the Atlantic and Paleo- flower structures in the Magdalena Valley occurred, due Caribbean oceans during the Early Cretaceous (Pindell to the reactivation of basement structures in a transpressive and Dewey, 1982; Pindell, 1985; Jaillard et al., 1990). A setting (Montes, 2001; Corte´s, 2004). This phase induced a first period of accretion occurred in the Early Aptian when change in the settings and basin mechanisms of the EC, the Amaime terrain was accreted, inducing deformation in which became mainly of continental affinity and related the area of the Central Cordillera (Alvarez, 1983). This tec- to the flexural response of the lithosphere, as well as rem- tonic pulse preceded a period of thermal subsidence in the nant thermal subsidence (Sarmiento, 2001). From the Early EC during the Late Cretaceous and was concomitant with Eocene to the present, a change in the regional tectonic set- continuous subduction of the Farallon plate in the western ting of the South Caribbean region also occurred, related margin of Colombia. The total crustal stretching after this to a shifting from relative divergence to convergence

4 M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx between the Americas, which induced a compressive regime mechanisms of the chain in terms of the geodynamics of in the EC (Corte´s et al., 2005). This new tectonic regime the northern Andes. As a result, two kinds of models have allowed inversion of ancient basement faults in both flanks been proposed to explain the present-day structure and of the EC during the Andean tectonic phase, producing geodynamic setting of the EC. Colletta et al. (1990) suggest most of the present-day relief of the northern Andes (Col- a continental subduction below the axial zone of the EC to letta et al., 1990; Cooper et al., 1995). The Late Miocene explain the double vergence of the chain. According to this collision of the Panama arch in western Colombia has been model, the bending of the continental slab below the axial correlated with the main Andean tectonic phase (Duque- zone of the EC produced a mechanical anisotropy that Caro, 1990; Taboada et al., 2000). induced a double-verging system (Fig. 3A). Significant We present a structural model of the western flank of the changes in the stratigraphic thickness of the Lower Creta- EC based on field data, paleontologic determinations, and ceous units around most of the major faults of the EC subsurface data. In addition, we propose a regional bal- prompt Colletta et al. (1990) to propose a model of inver- anced cross-section of the central segment of the EC. Final- sion of ancient normal faults. This balanced cross-section ly, we discuss some implications of this model for the deep implies a tectonic shortening of 105 km. The inversion structure of the EC and the present geodynamic architec- model also has been adopted by Sarmiento (2001) and ture of the northern Andes. Cooper et al. (1995) and modified by Taboada et al. (2000), who calculated 120 km of shortening in the same 1.3. Structure of the EC section. In addition, Sarmiento (2001), in constructing a palinpastic model of the EC, notes a general southward Early works pertaining to the regional structure of the decrease in the amount of regional shortening. EC consider the chain a relatively simple, double-verging In contrast, Dengo and Covey (1993) propose that the belt bounded at both flanks by high-angle, thick-skinned EC is essentially an east-verging structure formed during inverse faults (Campbell, 1965; Campbell and Bu¨rgl, two main tectonic phases. The first tectonic phase induced 1965; Julivert, 1970; Irving, 1975). Later geological models a thin-skinned style that created large, east-verging thrust of the EC were constrained by new geological information faults, detached into Lower and Upper Cretaceous and and the construction of regional balanced cross-sections, Paleogene sequences. In this model, the low-angle faults which enabled models that accounted for deep structural are rooted in the Central Cordillera and in the western sub-

Fig. 3. Two geodynamic models accounting for structural mechanisms of the EC (A) Colletta et al. (1990), intracontinental subduction beneath the axial zone of the EC. (B) Dengo and Covey (1993), mid-crustal, low-angle detachment rooted in the western subduction complex of Colombia.

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 5 duction zone through a mid-crustal detachment that decap- superimposed on the previous low-angle faults, led to itated Jurassic graben structures (Fig. 3B). A second tec- new, thick-skinned inverse faults that produced the pres- tonic pulse during the late Miocene Andean phase, ent-day structural relief of the EC. As a result, Dengo

Fig. 4. Generalized stratigraphic scheme of the central segment of the EC (see Fig. 2 for location).

Fig. 5. Stratigraphic position of fossils constraining the structural model.

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Fig. 6. Examples of small-scale structures that allow reconstruction of paleostress regimes in EC. and Covey (1993) calculate 140 km of shortening in the Jones (1995) proposes that the thrust faults in the western northern segment of the EC (Fig. 3b). Their geodynamic flank of the EC are rooted in a major, listric, normal fault model, which includes a mid-crustal detachment linked to located in the eastern flank. the western subduction zone of Colombia, has been adopt- However, in the northern and central segments of the ed by Cooper et al. (1995), who find 68 km of shortening EC, there is no evidence of major shear zones or normal for the northern segment of the EC. Roeder and Chamber- faults. In addition, evidence from present-day fault kine- lain (1995) propose a structural style of low-angle basement matics (Taboada et al., 2000; Corte´s et al., 2005), seismicity faults with dominant east-verging tectonic transport, distributions, and present-day kinematics derived from implying 190 km of tectonic shortening. The crustal struc- focal mechanism of earthquakes (Corredor, 2003; Dimate ture of the EC in this model is constrained according to the et al., 2003; Corte´s and Angelier, 2005) suggest compressive Moho root. behavior by the major faults bounding the EC, though Alternative models also have been proposed to explain some degree of stress partitioning prior to the main the kinematics of the EC. Some postulate a transpressive Andean phase has been observed (Taboada et al., 2000; origin of the chain, suggesting that the geometry of the Sarmiento, 2001; Branquet et al., 2002; Corte´s, 2004). EC resembles that of a positive flower structure, related This study focuses on two regions of the EC: the Sabana to a major central shear zone (Montes, 2001), or is bound de Bogota´, in the axial segment of the chain, and the Gua- by major transpressive systems in both flanks, generating duas syncline and the Girardot fold belt in the western en echelon–type structures (Kammer, 1999). In contrast, flank (Fig. 2). In these areas, geological field mapping

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Fig. 7. Geologic map of Guaduas syncline and Sabana de Bogota´ region. SRF, San Juan de Rio Seco fault. and analyses of mesoscopic-scale structures indicate 1.4. Stratigraphy sequences of paleostress regimes that prevailed in the EC from the Late Cretaceous to the present day (Corte´s In our study, we use the stratigraphic nomenclature pro- et al., 2005). These regimes are characterized by an active posed by Raasveldt (1956) and Raasveldt and Carvajal compression in a dominant WSW-ENE to E-W direction (1957) for the Cenozoic sequence in the Guaduas syncline that lasted until the late Paleocene. The tectonic phase region and that of Caćeres and Etayo-Serna (1969),Cać- was followed by a change in the regional direction of com- eres (1970), and Martinez and Vergara (1999) for the Cre- pression that shifted to NW-SE during the Early Eocene taceous succession of the western flank. In Sabana de and finally become WNW-ESE during the last episodes Bogota, we adopt the nomenclature used by McLaughlin of the Andean tectonic phase. and Arce (1975). The stratigraphic nomenclature of Bran- Previous works considering the structure of the western quet et al. (2002) and Casero et al. (1997) is used for the flank of the EC and the Sabana de Bogota have been car- eastern flank of the EC (Fig. 4). ried out by Cardozo (1989), Montes (2001), Namson et al. Age determinations of macrofossils collected in the Cre- (1994), Ramirez (1989), and Restrepo-Pace (1999). These taceous strata of the Apulo region and Guaduas syncline authors agree about the presence of major post-Miocene, were carried out by Dr. Fernando Etayo-Serna. These west-verging thrust faults (i.e., Bituima and Cambao) that determinations constrain the age of sedimentary units overthrusted the western flank of the EC on the foreland involved in thrust sheets in structural complex areas (i.e., sediments of the Magdalena Valley (Fig. 7). The Ibague La Vega thrust front, see Section 2.2.2). The positions of fault, also a key structural piece of the study area, is a base- fossils in the stratigraphic column appear in Fig. 5, with ment-inherited fault, reactivated as right-lateral shear. This details in Appendix A. fault has been considered the southern limit of the Middle Magdalena Valley and a major fault controlling deposition 2. Balanced cross-sections of Early Cretaceous sediments (Cooper et al., 1995). Paleo- cene activity in a transpressive structural setting around 2.1. Field data and geologic map this fault has been identified by Montes (2001) and Corte´s et al. (2005). Fieldwork in the study area focused on detailed geological mapping and a structural data survey. The analyses of

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Fig. 8. (Left) Radar image with location of seismic lines used herein and regions of detailed field mapping: I, Guaduas syncline; II, Sabana de Bogota. (Right) Interpretation of main structural features of the central segment of EC. SB, Sabana de Bogota´; GS, Guaduas syncline; IF, Ibague´ fault; HF, Honda fault; CF, Cambao fault; BF, Bituima fault; FS, Fusagasuga´ syncline. kinematic indicators, particularly the inversion of fault- this region of Sabana de Bogota, Corte´s (2004) and Montes striated plains, indicate small-scale structures related to a et al. (1994) present field evidence suggesting relationships pre-Eocene, WSW-ENE to E-W compression and post- between salt domic structures and the set of NW-SE Middle Eocene to present-day, NW-SE to WNW-ESE wrench faults. compression (Corte´s et al., 2005). Such structures were In these models, the diapiric process seems triggered by measured in rock formations ranging in age from Early lateral transtensional displacements associated with the set Cretaceous to Miocene (Fig. 6). of faults. In addition, Ujueta (1993a,b,c), through remote- The geologic map (Fig. 7) shows the most relevant struc- sensing analyses, suggests these lineaments and faults are tures for the western flank of the EC and suggests two main pervasive along most of the EC and Merida Andes. structural trends. The Guaduas syncline and major west- Finally, such faults (NW-SE) seem to have controlled verging thrust faults (i.e., Bituima, Cambao, and Honda) the southern extent of Early Cretaceous sediments in the show roughly a NNE-SSW trend. southern extreme of the study area, as noted by Fabre In contrast, a SW-NE trend appears in structures of the (1987) and Sarmiento (2001). Similar cases of deflection Girardot fold belt and Sabana de Bogota´, which is also the of structural trends and plunging fold axes have been asso- structural grain of the Ibague fault and other similar faults ciated with the presence of major lateral ramps (Macedo affecting the axis of the Guaduas syncline locally (i.e., San and Marshak, 1999; Wilkerson et al., 2002). These structur- Juan de Rio Seco, Fig. 7). The Ibague fault disappears al and stratigraphic relationships suggest that the NW-SE– below the Cambao thrust in the area where the Guaduas trending faults may have been basement-inherited struc- syncline deflects its trend to a NE-SW direction and disap- tures, possibly transfer faults, that behaved as traverse- pears (Fig. 7). lateral ramps during the Andean orogeny (Fig. 8). Addi- In this same region, the Girardot fold belt takes the tional fieldwork and geophysical evidence in conjunction place of the Guaduas syncline, which suggests that the Iba- with structural modeling are necessary to support this idea. gue fault acted as a barrier that locally separates two structural domains with remarkable differences in their trends 2.2. Structural cross-sections and folding styles. In Sabana de Bogota, a set of faults trending NW-SE is In Fig. 8, we present the positions of seismic reflection identified, most corresponding to left-lateral strike-slip profiles used in the structural interpretation. In addition, faults. Locally, some folds deflect and show plunging axes we use surface structural, stratigraphic, and paleontologic around the NW-SE left-lateral faults (Figs. 7 and 8). For data from our geologic map and those in the literature

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Fig. 9. Geologic map of the central segment of EC (modiﬁed after Cediel and Ca´ceres, 1988; Raasveldt, 1956; Raasveldt and Carvajal, 1957) and location of local and regional balanced cross-sections (see Fig. 2 for location). Other geologic maps used in this study: 1. Ulloa and Acosta (1978);2.Ulloa et al. (1993);3.McLaughlin and Arce (1975);4.Renzoni (1965);5.Ulloa et al. (1975);6.Segovia and Renzoni (1999). Other structural cross-sections: (C) Casero et al. (1997); (D) Rowan and Linares (2000).

(Fig. 7). This database supports the construction of eight Cretaceous succession (Restrepo, 1989). In addition, in partial and one complete balanced cross-section in the cen- the Medina anticline region (Fig. 9), the presence of tral segment of the EC (Fig. 9). sheared evaporite beds interbedded with Early Cretaceous shales (Branquet et al., 2002) seems to confirm that region- 2.2.1. Sabana de Bogota´ ally, the base of the Cretaceous behaved as a major The structural interpretation of the eastern margin of detachment. the Sabana de Bogota´ is constrained with seismic line 1 In seismic line 1 (Fig. 10), the base of the Cretaceous and and structural data from geologic maps 2 and 3 (Fig. 9). even the Jurassic fits the position of a opaque level, located From a regional point of view, the structure of Sabana at approximately 3–3.5 s (TWT), well, which we consider de Bogota is characterized by large symmetric synclines, induced by the low acoustic impedance of the salt-rich stra- ranging in amplitude 15–25 km and associated with tighter ta. The balanced cross-section based on this seismic line overturned anticlines. Locally, the folds show plunging axi- shows a local shortening of 8 km. To balance the sedimen- al surfaces, which deflect its trend around NW-SE traverse tary cover shortening and basement strain, in this section, faults. Previous works considering structural models of the major thrust faults merge in depth with basement faults folds in Sabana de Bogota´ have been carried out by Julivert (Fig. 11). (1963), McLaughlin and Arce (1975), Camargo (1995), and The structural cross-section of the western margin of Ortiz (1996). In these studies, the presence of evaporate- Sabana de Bogota´ was constrained by seismic line 2, struc- bearing beds seems to determine the position of major tural and stratigraphic data from well Chitasuga-1 (Fig. 8), decollements within the lower Cretaceous strata (Kicaf and data from geologic map 2 (Fig. 9). This structure seems and Kich, Fig. 4). In this same area, salt domic structures quite simple, with a SE-verging hangingwall anticline seem associated with NW-SE lateral ramps (Montes involving the Lower Cretaceous units (Kicaf) and second- et al., 1994; Corte´s, 2004). Dating of parental rock xeno- ary SE-verging thrust faults detached into the Upper Cre- liths involved in the salt body reveals an Early Cretaceous taceous shales (Ksch) (Fig. 12). age of the evaporite beds (Bricenõ et al., 1990). However, in The balanced cross-section constructed with the seismic the Quetame massif area (Fig. 9), detailed field data suggest line in Fig. 12 suggests at least 8.5 km of shortening related the presence of a major detachment along the base of the to NW-verging structures (Fig. 13). This cross-section is at

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Fig. 10. Seismic line 1 and interpretation. Note seismic opaque reflector at 3–3.5 s (TWT), matching the position of Jurassic–Early Cretaceous salt-rich strata, a potential decollement (see Figs. 8 and 9 for location; same stratigraphic units as in Figs. 4–6). the western boundary of Sabana de Bogota, near the thrust pervasive as mechanisms that accommodate internal strain front of La Vega (Figs. 7 and 9). La Vega thrust front is a near the main detachments (Fig. 14). complex of predominantly west-verging thrust belts, In this section, both the slaty cleavage and fabric dia- detached within the Lower Cretaceous strata. Around this grams of small-scale folds reveal a NW direction of tecton- area, a marked change in facies and thickness of the Lower ic transport and structural vergence, which confirms the Cretaceous units occurs. In effect, west of the Subachoque tectonic origin of small-scale folding (Fig. 15). The bal- syncline, the Lower Cretaceous sequences are similar to anced cross-section was accomplished by area-balance units of the Apulo and Guaduas syncline areas (Fig. 9). methods, assuming 0.9 km of constant thickness of the bas- In contrast, west of the Subachoque syncline, the Lower al unit (Kin). This section implies a minimum tectonic Cretaceous sequences are thicker and could be described shortening of 17 km (30%). However, previous works show as typical sequences of Sabana de Bogota (Fig. 4). This that slaty cleavage and associated layer parallel shortening sharp stratigraphic and structural boundary could be probably imply an additional 15% of shortening in the explained by the presence of a normal fault that induced plane of the section (Hossack, 1979). facies changes during the Early Cretaceous (see Section Field data and age assignments of fossils (Appendix A) 1.2). If so, the Subachoque syncline resulted from tectonic reveal the presence of three main detachments, labeled 1–3 inversion of the normal fault. This kind of structure and its in Fig. 15. These detachments, deeper westward, are locat- subsequent inversion has been observed in the northern ed on the upper segment of the Berramian Trincheras For- segment of the EC (Julivert, 1970; Colletta et al., 1990). mation (Kit) and on top and at the base of the Naveta Formation (Kin, see also Figs. 4, 5). 2.2.2. La Vega thrust front and Villeta anticline At the northern tip of the Villeta anticline, cross-section West of Sabana de Bogota is La Vega thrust front IV (Fig. 9) confirms the presence of three regional detach- (Fig. 9), an area structurally characterized by the presence ments. Fault N 1(Fig. 16) is located along the base of the of imbricated, west-verging thrust sheets involving the Naveta Formation in the Villeta anticline. The presence of Lower Cretaceous strata. Given the facial similarities of penetrative folding and slaty cleavage confirms the pres- units in this area, mostly composed of monotonous, sili- ence of a major detachment at this level. Farther west, ceous, black shales, and its structural complexity, the col- the fault takes up the base of the Trincheras Formation lection and age assignments of ammonites identify and outcrops as a set of imbricated, west-verging thrust tectonic repetitions (Figs. 5and 15). In this section, meso- sheets in Villeta. Locally, this fault also involves the base scopic-scale disharmonic folding and slaty cleavage are of the Aptian (Kiv). In this model, the Bituima (fault 2.2,

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Fig. 11. Balanced cross-section I, based on seismic line 1 of Fig. 10. Eastern segment of the Sabana de Bogota (see Fig. 9 for location). Same stratigraphic units as in Figs. 4–6.

Fig. 16) and Cambao (fault 2.1, Fig. 16) faults merge at tion of the Guaduas syncline as the Girardot fold belt occu- depth. To balance sedimentary cover shortening and pies its structural position (Fig. 9). basement strain, the major faults were rooted in In this area, coarse-grained strata of Upper Cretaceous basement-involved structures (fault 2, Fig. 16). age (Cimarrona Formation, Fig. 4) and growing strata in The structural geometry in the area suggests that early the Cenozoic sequences account for the syntectonic nature thrust sheets were passively folded and transported as of the Guaduas syncline as a piggy-back basin (Corte´s, new basement structures were reactivated in a breaking- 2004). This basin was active from Maastrichtian to Paleo- forward sequence. Such structures, including reactivation cene times, when early uplifting of the Central Cordillera of basement-inherited faults that folded and passively began, and continued its eastward displacement during transported the prior thin-skinned structures, have been the Cenozoic (Gomez et al., 2003). Fission-track data and observed in other folded chains, such as the Apennines, facies changes suggest that this early tectonic pulse also Alps, and Pyrenees (Roure et al., 1990). This model also activated the western flank of the EC (Gomez and Pedraza, explains the occurrence of thick-skinned structures offset- 1994; Gomez et al., 2003). ting previous thin-skin structures, as observed by Dengo In the western thrust front of the EC, the Guaduas syn- and Covey (1993) in the northern segment of the EC. cline is transported along the hangingwall block of the west-verging Cambao fault (Figs. 7 and 9). This structure 2.2.3. Guaduas syncline and Girardot fold belt preserves most of the Cenozoic strata, reaching locally a In the region of the Guaduas syncline and Girardot fold thickness of more than 3 km of syntectonic sediments belt, four balanced cross-sections can be constructed (Figs. (Fig. 17). In the hangingwall block of the Cambao fault, 8 and 9, sections IV–VIII). These sections clarify the lateral the Guaduas syncline involves upper Cretaceous units, variations of the major faults of the western thrust front of which in the axial segment of the syncline reach a hanging- the EC, enabling an explanation of the southward termina- wall flat at the base of the Aptian beds. In contrast, in the

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Fig. 12. Seismic line 2 (see Fig. 8 for location) and interpretation of the western margin of the Sabana de Bogota. Labels correspond to same stratigraphic units as in Figs. 4–6. western flank, the Upper Cretaceous units are involved in a Also in the eastern flank, the Bituima fault places Lower hangingwall ramp and, farther west, a hangingwall flat at Cretaceous strata on Upper Cretaceous units (Figs. 17A the base of the upper Cretaceous (Umir shale, Fig. 4). In and B). This fault branches, and its westernmost segment the northern segment, the Cambao fault outcrops as a set merges at depth with the Cambao thrust in the axial zone of west-verging thrust faults, whereas in the southern seg- of the Guaduas syncline. As a consequence, the Bituima ment, it is a single fault. Therefore, the amount of shorten- fault partially translates displacement on the Cambao ing in the Cambao fault tends to decrease southward. thrust front along a hangingwall flat located at the base In contrast, in the eastern flank of the Guaduas syn- of the Aptian (Hilo Formation fault 2’, Fig. 18a). In addi- cline, the structural relief of the hangingwall block of tion, a branch of the Bituima fault outcrops as a west-verg- the Cambao fault, which exceeds 4 km, suggests that the ing thrust, whereas a minor part of the displacement is fault involves the whole Cretaceous sequence and the translated on the El Trigo fault (Figs. 17A and B). basement. The lowermost Cretaceous unit (Kin, Fig. 4) Farther west, Cambao leading translates some of its dis- crops out east of the Guaduas syncline in the Apulo anti- placement on the foreland basin throughout the Honda cline (Fig. 7). fault, which merges with the Cambao thrust at the axial

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Fig. 13. Balanced cross-section II, constrained with seismic line 2 (Fig. 8) and surface data from geologic map 2 (Fig. 9). Inverted normal fault beneath Subachoque syncline accounts for facies changes in the Lower Cretaceous and contrasting structural styles on each side of the syncline. Same stratigraphic units as in Figs. 4–6. zone of the Guaduas syncline at approximately 2.5 s (twt) as normal faults that controlled the western extent for (Fig. 17A). According to data from wells Chiripa-1, Men- the lower Cretaceous sedimentation. dez-1, and Beltran-1, this fault in its eastern extreme places In almost all seismic profiles, a set of positive flower struc- a hangingwall flat on a footwall flat along the basal Upper tures locally offset the thrust faults. Some of these faults crop Eocene unit (Hoyoń Formation, Figs. 17A and 18a). In out, as is the case of the San Juan de Rio Seco fault (Fig. 7), a contrast, in its western extreme, the Honda fault crosses WSW-ENE–trending, right-lateral wrench fault (Ibague- up-section through a hangingwall ramp and outcrops. type) that offsets by more than 1 km the axis of the Guaduas The northernmost section of the Guaduas syncline is syncline (Figs. 7 and 17b). This offset suggests that reactiva- constrained with seismic lines 3 and 4 (Fig. 8) and sub- tion of the SW-NE basement-involved structures, as right- surface data from wells Chiripa-1, Mendez-1, and Madri- lateral wrench faults, is the latest tectonic event. gal-1 (Fig. 17a-A). In this area, the Chiripa-1 and In the southernmost section, seismic line 9 (Fig. 17B-D) Mendez-1 wells drilled Miocene–Oligocene strata in the shows the area where the Ibague fault joins the western flank hangingwall block of the Honda fault and the Oligo- of the Guaduas syncline and Cambao thrust. The Ibague´ cene–Paleocene sequence in the footwall. The metamor- fault appears associated with an anticline structure uncon- phic basement occurs at approximately 3000 m. South formably buried below the late Paleocene sediments of the of this section, the Beltran-1 well shows roughly the Hoyoń Formation. In the axial zone of the anticline, some same sequences but with a thin sequence of Upper Cre- subvertical faults delineate a positive flower structure. In this taceous strata overlying the basement as well. This addi- area, Corte´s et al. (2005) and Montes (2001) find field evi- tion shows a general southward and eastward increasing dence of a WSW-ENE to E-W direction of compression dur- thickness of the Upper Cretaceous strata overlying the ing the Coniacian–Early Paleocene. Such a state of stress, basement. However, the Cretaceous thickness changes oblique with respect to SW-NE–trending faults, would allow from less than 200 m in the Beltran-1 well to a sequence the reactivation of this type of fault as right-lateral wrench of more that 3000 m in the hangingwall block of the faults, as supported by field data. This possibility argues in Cambao fault in a horizontal distance of less than favor of pre-Late-Paleocene (or pre-Andean) activity of the 30 km (calculated in the balanced section). Thus, the Ibague fault as a wrench fault and suggests a minor, recent frontal ramps of the Cambao and Bituima faults behaved reactivation of this structure as a right-lateral shear.

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Fig. 14. Small-scale structures accommodating internal strain in the lower Cretaceous sequence of the western flank of the EC (La Vega thrust front). Stop 425, Small-scale thrust fault locally repeating turbidite sandstone with flexural flow fold as a mechanism of folding in the footwall. Stop 427, NW-verging disharmonic kink fold associated with small-scale thrust fault. Stop 426, Small-scale fault-propagation fold with overturned frontal limb. Stop 423, Mesoscopic-scale box fold with internal disharmonic folds in turbidite sandstone of lower Cretaceous age. Stop 431, Penetrative slate cleavage in Barremian shales.

Additional evidence of Paleocene activity appears in imately 3.5–4 s (twt). In the western ﬂank, the Paleocene seismic line 3 (Fig. 17A), which shows a positive structure strata onlaps, suggesting pre- and syn-Early Paleocene below the eastern ﬂank of the Guaduas syncline at approx- development of structural relief.

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 15

Fig. 15. Balanced cross-section III. La Vega thrust front, western ﬂank of EC (see Fig. 9 for location; see the Appendix A for details about fossils constraining age and location of thrust sheets 1). Same stratigraphic units as in Figs. 4–6.

2.3. Balanced cross-sections of Guaduas syncline and shortening (approximately 20 km total shortening on aver- Girardot fold belt age) for sections VI and VIII. To constrain the behavior of each fault in the western The analyses of seismic profiles (Figs. 17A and B), well thrust front of the EC better, we calculate for each fault data, and field mapping imply four balanced cross-sections on the balanced cross-sections the amount of displacement, (sections V–VIII) of the western margin of the EC (Figs. as well as the total displacement for the ensemble of faults, 18a and b). In this area, there are basically two kinds of presented as vectors (Fig. 19). In the northern segment of faults. The first (Ibague´-type) are traverse faults that trend the Guaduas syncline, the largest displacement is accom- SW-NE and are oblique with respect to the plane of the modated on the Cambao fault, which shows approximately structural sections. These faults (e.g., fault 1 in Fig. 18) 12 km of shortening. In contrast, the Bituima fault trans- are associated with pre-Late Paleocene positive structures lates to only 4 km of displacement on the Cambao thrust in the footwall block of the Cambao fault. front through the deep branch and less than 2 km on the The amount of shortening in the transverse faults was outcropping branch. To the south, this relationship is considered in the total displacement vector. The amount inverse, and the Cambao fault decreases its displacement of displacement out of the plane of the section on the obli- as the Bituima fault increases. This decreasing displace- que faults of sections V and VII was neglected because of ment on the Cambao fault is particularly marked between the small amount of lateral displacement (<0.5 km on aver- section VI and VII (Fig. 19). In the southernmost section, age). However, on the San Juan de Rio Seco and Ibague the Bituima fault translates to more that 9 km on the Cam- faults (sections VI and VIII, respectively), the amount of abao thrust front and began to translate part of its dis- lateral displacement was on the order of 1 km, which would placement to the Girardot fold belt (Fig. 18b, section VII). imply a maximum displacement of 0.7 km out of the plane The Bituima fault translates a larger amount of displace- of the section (1 km · COS 45). This result suggests an ment between sections VI and VII, compensating for the average maximum error of 3.5% in the estimated total abrupt loss of displacement on the Cambao fault in this

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Fig. 16. Structural cross-section IV; northern extreme of the Villeta anticline, western flank of EC (see Fig. 9 for location). Same stratigraphic units as in Figs. 4–6. area. This action allows the total displacement vector to Bogota. Immediately to the east and west of Sabana de behave homogeneously, with a constant tendency to Bogota´, two strips of west- and east-verging imbricated decrease southward (Fig. 19). This compensatory behavior thrust faults, respectively, are associated with major suggests that the Bituima and Cambao faults merge in a decollement surfaces on the Lower Cretaceous strata. In sole thrust. In addition, the southward tendency of the both flanks of the chain, associated with major thrust Cambao thrust to disappear as the Bituima fault becomes faults, large synclinal structures preserve and transport predominant can be explained with a model of transfer Cenozoic syntectonic strata. These major faults are the zone (Dahlstrom, 1969). This model also explains the Cambao and Bituima in the western flank and the Lengupa southward termination of the Guaduas syncline as a struc- and Aguaclara in the eastern flank (Fig. 9). ture associated with the Cambao fault, while the Girardot In the eastern flank of the EC, the Medina anticline is a fold belt takes its place as a structure associated with the hangingwall ramp anticline (Casero et al., 1997; Rowan Bituima fault (Fig. 20). and Linares, 2000; Branquet et al., 2002). The ramp seems to fit a large pre-Cretaceous normal fault, which acted as 3. Regional structure of the EC the eastern boundary for Early Cretaceous sediments. The entire sequence is detached in the lower Cretaceous To estimate the regional shortening of the EC, we use shales. Immediately to the west of the Medina anticline, local balanced cross-sections I–V, as presented in the previ- the Nazareth syncline shows a western flank overturned ous sections, and we project these profiles in a regional and affected by an east-verging fault (Fig. 9)—the Lengupa cross-section through the entire EC (Fig. 9, AB). Because fault, perhaps the most important fault of the EC in its cen- our field data and local sections are mainly for the western tral segment. This fault has exhumed metamorphic and flank of the EC and Sabana de Bogota´, we use structural crystalline basement in the area of the Quetame Massif data and cross-sections of the eastern flank of the EC from (Fig. 9). the literature (Fig. 9). The regional balanced cross-section of the EC was According to geologic maps (Fig. 9), the EC is a sym- restored at the top of the Maastrichtian (Guadalupe and metrical structure whose center is occupied by Sabana de Cimarrona formations) as a reference line (Fig. 4). The

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 17

Fig. 17. Seismic lines of the western thrust belt of the EC. (A) Seismic lines 3 and 4 of structural cross-section V. (B) Seismic lines 5 and 6 of balanced cross-section VI (see Figs. 8 and 9 for location). (C) Seismic lines 7 and 8 used in structural cross-section VII. (D) Seismic lines 9 and 10 used in balanced cross section VIII (see Figs. 8 and 9 for location). Labels correspond to same stratigraphic units as in Figs. 4–6. total regional shortening is estimated at 70 km, 40 km on ment at 14 km below the basement top. In our case, the west-verging structures and 30 km on the east-verging according to the regional restored sections of Fig. 21, the ones (Fig. 21). regional structural relief is approximately 1040 km2.In To estimate the depth of the basal decollement associat- conjunction with a regional tectonic shortening of 70 km, ed with the EC, we apply the depth-to-detachment method this location implies a basal detachment located 15 km (Hossack, 1979), previously used by Colletta et al. (1990) in below the top of the basement or 23 km below the top of the northern segment of the EC to estimate a basal decolle- the sedimentary cover in the axial zone of the EC

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Fig 17. (continued)

(Fig. 22). The limit between the lower and the upper crust in the axial zone of the EC (He´brard, 1985; Fabre, 1987; thus may have behaved as a surface with appropriate rhe- Sarmiento, 2001), which ﬁts the position of the restored ological contras to allow the development of such a region- basal detachment estimated herein (curve 1 in restored sec- al detachment. The depth of this major decollement is tion of Fig. 23). Therefore, a misﬁt of approximately 15 km similar to the thickness of the Maastrichtian crust, as esti- occurs between the structurally restored Moho and the pre- mated by back-stripping methods (He´brard, 1985; Fabre, dicted Moho from stratigraphic data (shadow area in 1987; Sarmiento, 2001), which suggests a Late Cretaceous restored section of Fig. 23). inheritance of the basal decollement of the EC. There are several possible explanations for this discrep- Finally, in the place between the basal decollement and ancy. We may have underestimated the amount of shorten- the top of the basement, we draw and restore, with a listric ing of the EC, in which case a model with an original geometry, the possible architecture of basement faults crustal thickness of 15–20 km and 170 km of shortening (Fig. 23). could explain the present crustal thickness of 48 km of In Fig. 23, we add the Moho root, according to gravi- the axial region of the EC. A similar solution was proposed metric data of Salvador (1991) (curve 2 in the deformed by Roeder and Chamberlain (1995) in the northern seg- state section of Fig. 23). In the restored crustal model, ment of the EC. Perhaps the Lengupa´-Guaicaramo´ fault the restored Moho root implies a crustal thickness of would experience greater shortening, which may explain approximately 35 km for the Maastrichtian. However, this some important stratigraphic changes in the Cretaceous estimated crustal thickness is estimated in less than 20 km and Cenozoic sequences on both sides of this fault.

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 19

Fig. 18. (a) Balanced cross-sections of the northern and central segments of the Guaduas syncline. (b) Balanced cross-sections of the southern segments of the Guaduas syncline and northern extreme of the Girardot foldbelt. (1) Pre-Late Paleocene wrench fault; (2) Bituima fault; (2’) Bituima fault merged with Cambao thrust front; (3) Cambao fault; (3’) Cambao thrust front; (4) Honda fault; (5) S.J. de Rio Seco fault (see Fig. 9 for location). Labels correspond to same stratigraphic units as in Figs. 4–6.

Another possible explanation for this problem is that would be shallower. However, it is also possible that the the present-day thickness of the crust was overestimated back-stripping models of the EC include erroneous in the gravimetric model; therefore, the present Moho root assumptions, and the Maastrichtian crust may have been

20 M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx

Fig 18. (continued) thicker than the predictions made by these models. In this Maybe the explanation is simply the result of all these case, an initial non-thermally equilibrated or thicker origi- factors and assumptions in the models (i.e., structural, nal crust could explain misﬁts. Finally, magmatic additions gravimetric, and tectosedimentary). The answer to this of the mantle and asthenosphere or a deep ductile mecha- question is beyond the scope of this article, but we know nism incorporating mass on the plane of the section could that continued work is needed to understand the crustal explain such abnormal crustal thickness. structure and depth mechanisms that have aﬀected the EC.

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 21

ey (1993) (Fig. 3b). However, fault kinematic reconstruc- tions (Taboada et al., 2000; Corte´s et al., 2005), focal mechanisms of earthquakes, seismicity distribution patterns (Corredor, 2003; Dimate et al., 2003; Corte´s and Angelier, 2005), and tomographic images (Gutscher et al., 2000; Taboada et al., 2000) suggest that the northern segment of the EC is under the influence of the Caribbean plate in a present-day compressive WNW-ESE state of stress. This model shows a relatively Caribbean flat slab plunging in the asthenosphere, below the axial zone of the EC. This suggestion argues in favor of a model of subduction below the EC as the mechanism that produced uplift of the belt (Colletta et al., 1990; Fig. 3a). In the central segment of the EC, the axial zone of lithospheric bending may be located below the Magdalena Valley, which implicates the Central Cordillera in the deformation. However, faults of the Romeral system and oceanic wes- Fig. 19. Displacement vectors of major faults in the western margin of tern complex (Fig. 1) accommodate strain related to sub- EC. Note constant southward decreasing of displacement of the Cambao duction of the Nazca plate and the triple junction area fault, compensated by increasing amount of shortening in the Bituima (Ego et al., 1996; Corte´s, 2004). Large amounts of stress fault. deflection and partitioning involving lateral displacements on these faults is related to the E-W stress regime of the Finally, our regional structural cross-section argues in Nazca plate (Ego et al., 1996; Corte´s, 2004; Corte´s et al., favor of a geodynamic model in which the Central Cordil- 2005), in contrast with the homogeneous WNW-ESE, pres- lera behaves as a rigid block that induces strain in faults ent-day state of stress in the area of the EC, which argues and blocks inside the EC, as suggested by Dengo and Cov- against a model (Dengo and Covey, 1993) linking the

Fig. 20. Structural scheme of a transfer zone, explaining southward-decreasing displacement on the Cambao fault and consequent termination of the associated Guaduas syncline. The Bituima fault increases its displacement southward, generating the Girardot foldbelt, which takes the structural position of the Guaduas syncline.

22 M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx

Fig. 21. Regional balanced cross-section of the central segment of EC of Colombia (see Fig. 9 for location). The Moho’s root for Maastrichtian times after Sarmiento (2001). Labels correspond to same stratigraphic units as in Figs. 4–6.

Fig. 22. Method used to estimate depth to detachment (Hossack, 1979) applied in EC of Colombia, implying a 23 km decollement below the axial zone of the EC. Labels correspond to same stratigraphic units as in Figs. 4–6.

Fig. 23. Model of the crustal structure of the EC, implying basement faults with listric geometry that merge in a major detachment at 23 km depth. Restoration for late Maastrichtian. Labels correspond to same stratigraphic units as in Figs. 4–6.

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 23

Fig. 24. Schema of the geodynamics of the northern Andes accounting for the structure of the EC of Colombia. Subduction of the Caribbean plate beneath the axial zone of the EC. The Nazca plate interacts with the western oceanic complex, whereas the Caribbean plate influences the EC. PCB, Panama-Choco block; WC, Western Cordillera; CC, Central Cordillera; EC, Eastern Cordillera; EP, Eastern plains; RF, Romeral fault; OF, Oca fault. Adapted from McCourt et al. (1984), Colletta et al. (1990), Taboada et al. (2000), and Corte´s (2004). deformation of the western oceanic complex with the EC Lengupa´ and Aguaclara. All these data suggest a structural (Fig. 3b). Fig. 24 shows a schematic model of the geody- symmetry of the EC. namics of the northern Andes, in particular of the EC, that In the western thrust front of the EC, two main structur- fits the field data, seismic models, and seismologic informa- al styles are identified. Positive flower structures and asso- tion well. ciated anticlines involve pre-upper Paleocene rocks. These structures formed when E-W compressional stress regimes 4. Discussion and conclusions acted on SW-NE–trending subvertical faults that were reactivated as right-lateral wrench faults (i.e., Ibague fault). In the EC, it is possible to identify three main structural These structures were later unconformably covered by regions whose deformation patterns differ. In Sabana de post-Upper Paleocene sediments. Subsequently, during Bogota´, large syncline structures are separated by narrow, the Miocene–recent Andean phase, the entire sedimentary overturned anticlines. The presence of salt-rich strata in sequence was involved in major thrust faults in both flanks the Lower Cretaceous strata provides a major decollement of the EC in a compressive NW-SE stress regime. Finally, that highly influenced the structural style. In the region west the present-day WNW-ESE state of stress reactivated the of Sabana de Bogota´, which we call La Vega thrust front, the Paleocene structures, which offset and modify the compres- structural style is characterized by imbricated, west-verging sive Andean trends. thrust sheets with penetrative, mesoscopic-scale folding In the western thrust front of the EC, complementary and slaty cleavage, accommodating approximately 17 km behavior by the Bituima and Cambao faults is identified. of shortening. This thrust belt is detached within the lower In the northern segment of the Guaduas syncline, the Cam- Cretaceous fine-grained sequences. In the hinterland area, bao fault takes up most of the displacement (12 km), near Sabana de Bogota, these faults merge in basement struc- whereas the Bituima fault takes only a minor part tures that passively folded and transported successive thrust (4 km). This relationship is inverse in the southern sheets. Similarly, in the eastern flank of the EC, east of extreme of the Guaduas syncline, where the Cambao fault Sabana de Bogota´, a region shows the same structural style tends to disappear and the Bituima assumes most of the and detachment levels as observed in La Vega thrust front. displacement. In the central segment of the Guaduas syn- In the western thrust front of the EC, the Guaduas cline, the Cambao fault lost most of its displacement, syncline, bounded by the Cambao and Bituima faults, whereas the Bituima Fault increases considerably. This preserved and transported syntectonic sediments of the complementary behavior defines a transfer zone between western foreland basin. In the eastern flank, the same kind the Cambao and Bituima faults and allows the western of structures are found (i.e., Medina anticline, Nazareth thrust front to have homogeneous behavior, characterized syncline), involving and transporting syntectonic sequences by a general tendency to southward-decreasing displace- of the Llanos foothills. The major faults in this area are the ment. The northernmost section shows more than 20 km

24 M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx of shortening, whereas the southern section shows less than Acknowledgments 15 km. The presence of a transfer zone in the western thrust We thank the Colombian oil Company ECOPETROL, front of the EC explains why the Guaduas syncline termi- which provided seismic lines and wells. This article summa- nates to the south, as a structure associated to the Cambao rizes some results from the doctoral dissertation of Martıń fault, whereas the Girardot fold belt, associated with the Corte´s at the University Pierre et Marie Curie, Paris IV, Bituima fault, takes its structural position. and the French Petroleum Institute (IFP), which we also The construction of a regional balanced cross-section of thank. Special thanks to Dr. Fernando Etayo-Serna for the central segment of the EC shows minimum tectonic paleontologic determinations and Carlos Jaramillo and shortening of 70 km, distributed as 40 km in the west-verg- Milton Rueda for palynological identifications. We also ing faults and 30 km in the east-verging structures. This thank Germań Bayona and Claudia Osorio for critical dis- amount of shortening, in conjunction with 1040 km of cussions and Fabricio Combita for his enthusiastic assis- regional structural relief, implies a basal detachment locat- tance in the field. Helpful reviews and comments on the ed 15 km below the top of the basement or 23 km below the original manuscript were provided by Dr. Raul Seggiaro- top of the sedimentary cover in the axial zone of the EC. Sarmiento and Dr. Fernando Hector Bettini. This work This basal decollement fits Maastrichtian crustal thickness, was supported by the Corporacioń Geologica Ares (Bogo- suggesting that the base of the crust served as a major ta´), the Fundacioń Banco de la Repu´blica, research project decollement during post-Maastrichtian tectonic phases. 1102 (Bogota´), Colfuturo (Bogota´), and EGID (Paris).

Appendix A

Paleontologic data Stop N W Unit Fossils Age 88 044001300 743401400 Kih Oxytropidoceras sp., Lower-Late Albian Venezoliceras venezolanum Stieler, Venezoliceras multicostatum Renz 99 043704700 743405100 Kih? Venezoliceras sp., Lower-Late Albian Hysteroceras cf. bucklandi Spath 100 043704400 743405200 Kih? Mortoniceras Lower-Late Albian (Mortoniceras) cf. arietiforme Spath 122 043200900 743303600 Kis?? Eodouvillieceras horridum Upper- Late Aptian (Riedel), Corteziceras latecostata (Riedel) 124 043202600 743304100 Kis?? Colombiceras cf. foreroi Late Aptian Etayo Serna 125 043203000 743304600 Kic? Acanthohopilites Late Aptian eleganteante Etayo Serna, Parahoplites hubachi Etayo Serna 126 043203600 743305200 Kic? Roiometra columbiana Early Albian Clark, Douvilleiceras cf. Tarapacaence Etayo serna 127 043205100 743400500 Kic? Cupressinocladus Early Albian pompeckji (Salfeld), Douvilleiceras cf. mammillatum (Schlotheim), Neodeshayesites columbianus (Riedel) 130 043201100 743303900 Kis? Acanthohopilites Late Aptian eleganteante Etayo Serna (continued on next page) Please cite this article as: Martı´n Corte´s et al., Structure and tectonics of the central segment of the Eastern ..., Journal of South American Earth Sciences (2006), doi:10.1016/j.jsames.2006.07.004. ARTICLE IN PRESS

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 25

Table 1 (continued) Stop N W Unit Fossils Age 131 043200900 743304900 Stoyanowiceras Late Aptian treffryanus (Karsten). Acanthohoplites triston Etayo Serna, Crassatella aequalis Gerhardt, Cupressinocladus cf. pompeckji (Salfeld) 132A 043200100 743304500 Acanthohopilites Late Aptian eleganteante Etayo Serna 135 043104300 743304800 Kic? Eodouvillieceras horridum Late Aptian (Riedel), Juandurhamiceras cf. juandurhammi Etayo Serna 138A 043102800 743304000 Kit? Corbis (Sphaera) corrugata Sowerby 139 043105100 743303400 Kit Corbis (Sphaera) Barremian (?) corrugata Sowerby, Nododelphinula bellisculptata Jaworsky, Pterotrigonia tocaimaana (Lea) Ptychomia robinaldina buchiana Karsten, Mesoglauconia sp., 152 043102100 743404400 Kic Desmoceras (Desmoceras) Early Albian (?) cf. latidorsatum (Michilin) 156 043601100 742900100 Gagasiceras interiectum Late Aptian (Riedel) 156A 043601100 742900100 Podozamites sp., 183A 043300700 743405600 Kih Oxytropidoceras hubbardi Middle Albian (?) Knechtel, Oxytropidoceras aff. Douglasi Knechtel 183b Sergipia scheibei Heinz, 183c Benavidesites sp?, Upper-Middle Albian- Dipoloceras aff. Lower-Late Albian Bouchardianum (d0Orbygny) 208 Coilopoceras sp. Upper- Middle Turonian 278 051004600 0742803300 Kin Buchotrigonia cf. Etayoi Valanginian (?) Villamil, Mesoglauconia studeri peruana (Fritzsche) 281 051201100 0743002400 Kic? Kih Crassatella aequalis Late Aptian Gerhardt, Epicheloniceras cf. amazonarum (Burckhardt) 291 051201600 0742905400 Kit Heinzia (Gerhardtia) Lower- Middle Barremian galeatoides (Karsten), Emericiceras sp. 293 051201600 0743000300 Kic? Kih Gargasiceras interiectum Late Aptian (Gr.Villeta) (Riedel), Gargasiceras acutecostum (Riedel) (continued on next page) Please cite this article as: Martıń Corte´s et al., Structure and tectonics of the central segment of the Eastern ..., Journal of South American Earth Sciences (2006), doi:10.1016/j.jsames.2006.07.004. ARTICLE IN PRESS

26 M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx

Table 1 (continued) Stop N W Unit Fossils Age 294 051205600 0743002400 Above Kih Sergipia sp., Upper- Middle Albian- Ralphimlayites cf. Lower-Late Albian Prorsocurvatum (Gerhardt), 299 051103500 0743103300 Kic Dufrenoyia sp. Late Aptian

302 051102500 0743200200 Kih Hysteroceras sp. Upper- Middle Albian- Lower-Late Albian 312 050104600 0743003800 Kit Pulchellia aff. galeata (von Upper-Early Barremian Buch) 316 050103100 0743101200 Kis? Pseudoaustraliceras Late Aptian columbiae (Basse)?, Stoyanowiceras treffryanus (Karsten)? Crassatella aequalis Gerhardt? 317 050103600 0743102200 Kis? Stoyanowiceras Late Aptian treffryanus (Karsten), Crassatella aequalis Gerhardt, Pseudoaustraliceras columbiae (Basse)?, Hypophylloceras wiedmanni Etayo Serna, Acanthohoplites bigouretiforme Etayo Serna 319A 050101700 0743101500 Kis? top Crassatella aequalis Late Aptian Gerhardt, Acanthohoplites sp., Gargasiceras sp. 319B 050101700 0743101500 Kic Riedelites obliquum Late Aptian (Riedel), Epicheloniceras sp., Crassatella aequalis Gerhardt 319C 050101700 0743101500 Kic ? Base Crassatella aequalis Early Albian Gerhardt?, Trochleiceras sp. 322A 050103900 0743104300 Kih Oxytropidoceras Upper-Middle Albian- carbonarium (Gabb), Lower-Late Albian Stramentum alvaradoi (Royo y Gomez), Protanisoceras cf. nodosum (J. Sowerby), Mortoniceras sp. 384a 042604900 0743501800 Kih Oxytropidoceras Lower-Late Albian carbonarium (Gabb), Hysteroceras cf. orbigny (Spatt) 384B 042604900 0743501800 Kih Venezoliceras aff. acostae Lower-Late Albian (d’Orbygny), Stramentum cf. Alvaradoi Royo y Gomez, Hysteroceras cf. Carinatum Spatt (continued on next page) Please cite this article as: Martıń Corte´s et al., Structure and tectonics of the central segment of the Eastern ..., Journal of South American Earth Sciences (2006), doi:10.1016/j.jsames.2006.07.004. ARTICLE IN PRESS

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 27

Table 1 (continued) Stop N W Unit Fossils Age 385 042605300 0743401400 Kih ? Hysteroceras cf. andinum Lower-Late Albian Renz 394 042604000 0743200800 Kis? Acanthohoplites sp. Ind. Late Aptian 395 045203400 0743104300 Kih Stoyanowiceras Late Aptian treffryanus (Karsten), Hamiticeras cf. Pilsbryi Anderson 396 045202700 0743104800 Kic? Kih Melchiorites palmeri Late Aptian Etayo Serna?, Epicheloniceras pardoi Etayo Serna? 423 0504018,700 07426013,700 Kin Mexicanoceras hermelini Valanginian Etayo Serna? 426 0504005,900 07425044,700 Kin Pseudoosterella ubalaensis Valanginian Haas, Berriasella colombiana Haas? 428b 050400,5600 07425030,900 Kin Olcostephanus Late Valanginian (Jeannoticeras) sp., Leptoceras ubalaence Haas? 428a 050400,5600 07425030,900 Kin Berriasella colombiana Valanginian Haas? 430 0504000,800 07424051,700 Kit ? Nicklesia pulchella Lower-Early Barremian (d’Orbygny), Karsteniceras aff. beyrichi (Karsten) 431a 0503054,900 07424041,100 Kit Nicklesia pulchella Lower-Early Barremian (d’Orbygny), Crioceratites aff. emerici Leveille 433 0503026,600 07424010,300 Kit Nicklesia cf. pulchella Upper-Middle Barremian (d’Orbygny) (?) 440 0503026,600 07424010,300 Kit Pedioceras sp?, Middle-Early Barremian Pseudocrioceras sp? (?) 441 050200,6100 07422023,500 Kis Epicheloniceras sp., Late Aptian (?) Colombiceras foreroi Etayo Serna, Riedelites obliquum (Riedel) 442 050200,6100 07422023,500 Kih ? Hysteroceras sp?, Prohysteroceras sp? 444a 0501055,800 07422011,900 Kic ? Sergipia scheibei Heinz, Upper- Middle Albian- Lower-Late Albian 533 0507031.400 07359027.700 Ksg Peroniceras (Zuluiceras) Late Coniacian cf. bajuvaricum (Redtenbacher)

References Bourgois, J., Toussaint, J.F., Gonzalez, H., Azema, J., Calle, B., Desmet, A., Murcia, L.A., Acevedo, A.P., Parra, E., Tournon, J., 1987. Alvarez, A.J., 1983. Geologı´a de la Cordillera Central y el occidente Geological history of the Cretaceous ophiolitic complex of North- Colombiano y petroquı´mica de los intrusivos granitoides mesocen- western South America (Colombian Andes). Tectonophysics 143, 307– ozoicos. 26(2), Boletin Geologico Ingeominas, Bogota´. 327. Barrero, D., 1979. Geology of the Central Western Cordillera, west of Branquet, Y., Cheilletz, A., Cobbold, P.R., Baby, P., Laumonier, Buga and Roldanillo Colombia. Ingeominas, Bogota´ 4, 75pp. B., Giuliani, G., 2002. Andean deformation and rift inversion, Bourgois, J., Calle, B., Tournon, J., Toussaint, J.F., 1982. The Andean eastern edge of Cordillera Oriental (Guateque-Medina area), ophiolitic megastructures on the Buga-Buenaventura transverse Colombia. Journal of South America Earth Sciences 15, 391– (Western Cordillera-Valle Colombia). Tectonophysics 82, 207–229. 407.

28 M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx

Bricenõ, A., Buitrago, J., Lopez, C., 1990. Edad y origen de los depo´sitos Duque-Caro, H. (Ed.), 1984. Structural style, diapirism and accretionary de sal de la Sabana de Bogota´. Bc.S Thesis, Universidad Nacional de episodes of the Sinu´-San Jacinto terrane, southwestern Caribbean Colombia, Bogota´, 83pp. boreland. The Caribbean-South American Plate Boundary and Caćeres, C., Etayo-Serna, F. (Eds.), 1969. Bosquejo geolo´gico de la regioń Regional Tectonics. Geological Society of America, Memoir 162, pp. del Tequendama. Opu´sculo guıá de la excursioń pre-congreso, I 303–316. Congreso Colombiano de Geologıá. Universidad Nacional de Colom- Duque-Caro, H., 1990. The choco block in the northwestern corner of bia, Facultad de Ciencias, Bogota´, p. 23. South America: structural, Tectonostratigraphic, and Paleogeographic Camargo, A., 1995. Elemento estructurales del a´rea de la Sabana de implications. Journal of South America Earth Sciences 3, 71–84. Bogota´ y alredeores, Memoria, congreso Colombaino del petro´leo, Ego, F., Se´brier, M., Lavenu, A., Yepes, H., Egues, A., 1996. Quaternary Bogota´. Asociacioń Colombiana de Geo´logos del Petroleo, Bogota´, state of stress in the Northern Andes and the restraining bend model of pp. 197–209. the Ecuadorian Andes. Tectonophysics 259, 101–116. Campbell, C.J., 1965. Section through the Eastern Cordillera of Colom- Etayo-Serna, F., Parra, E., Rodriguez, G., 1982. Ana´lisis facial del bia, South America. Geological Society of America Bulletin 76, 567– ‘‘Grupo del Dagua’’ con base en secciones aflorantes al oeste de Toro 590. (Valle del Cauca). Geologıá Norandina 5, 3–12. Campbell, C.J., Bu¨rgl, H., 1965. Section Through the Eastern Cordillera Fabre, A., 1987. Tectonique et geńeration d’hydrocarbures: un mode`le de of Colombia, South America. Geological Society of America Bulletin l’evolution de la Cordille`re Orientale de Colombie et du Bassin de 76, 567–590. Llanos pendant le Cre´tace´ et le Tertiaire. Archives des Sciences Gene`ve Cardozo, E., 1989. Structural style of the central western flank of the 40, 145–190. Cordillera Oriental west of Bogota´, Colombia. M.Sc. Thesis, Univer- Gomez, E., Jordan, T., Almandiger, R., Hegarty, K., Kelly, S., Heizler, sity of South Carolina, Columbia S.C, 146pp. M., 2003. Controls on Architecture of the Late Cretaceous to Cenozoic Case, J.E., Durań, S.L., Lopez, R.A., Moore, W.R., 1971. Tectonic southern Middle Magdalena Valley Basin, Colombia. Geological Investigations in Western Colombia and Eastern Panama. Geological Society America Bulletin 115, 131–147. Society America Bulletin 82, 2685–2712. Gomez, E., Pedraza, P., 1994. El Maastrichtiano de la region Honda- Case, J.E., Barnes, J., Paris, Q., Gonzalez, I.H., Vinã, A., 1973. Trans- Guaduas, lı´mite del Valle Superior del Magdalena: registro sedimen- Andean Geophysical Profile, Southern Colombia. Geological Society tario de un delta dominado por rıós trenzados, Estudios Geolo´gicos America Bulletin 84, 2895–2904. del Valle Superior del Magdalena. Univ. Nacional de Colombia, Casero, P., Salel, J.F., Rossato, A., 1997. Multidisciplinary correlative Ecopetrol, p. 20. evidences for polyphase geological evolution of the foot-hills of the Gutscher, M.A., Spakman, W., Bijwaard, H., Engdahl, E.R., 2000. Cordillera Oriental (Colombia). In: VI Simposio Bolivariano de Geodynamics of flat subduction: Seismicity and tomographic con- Exploracion Petrolera en las Cuencas Subanadinas, Cartagena, pp. strains from the Andean margin. Tectonics 19, 814–833. 100–118. He´brard, F., 1985. Les foothills de la Cordille`re Orientale de Colombie Cediel, F., Caćeres, C., 1988. Geologic map of Colombia. Geotec Ltda, entre les rios Casanare et Cusiana. Evolution geódynamique depuis Bogota´. d’Eo Cre´tace´. Ph.D. Thesis, Univ. Pierre et Marie Curie, Paris, 162pp. Colletta, B., Hebrard, F., Letouzey, J., Werner, P., Rudkiewicz, J.L., 1990. Hossack, J.R., 1979. The use of balanced cross-sections in the calculation Tectonic Style and Crustal Structure of the Eastern Cordillera of orogenic contraction: a review. Journal of the Geological Society of (Colombia) from a Balanced Cross Section. In: Letouzey, J. (Ed.), London 136, 105–111. Petroleum and Tectonics in Mobile Belts. Editions Technip, Paris, pp. Irving, E., 1975. Structural evolution of the northernmost Andes, 81–100. Colombia. Geological Survey Professional Paper 846, 45. Cooper, M.A., Addison, F.T., Alvarez, R., Coral, M., Graham, R.H., Jaillard, E., Soler, E., Carlier, G., Mourier, T., 1990. Geodynamic Hayward, A.B., Howe, S., Martinez, J., Naar, J., Penãs, R., Pulham, evolution of the northern and central Andes during early to middle A.J., Taborda, A., 1995. Basin development and tectonic history of the Mesozoic times: a Thethyan model. Journal of the Geological Society Llanos basin, Eastern Cordillera, and Middle Magdalena Valley, of London 147, 1009–1022. Colombia. America Association of Petroleum Geologists Bulletin 79, Jones, P.B., 1995. Geodynamic Evolution of the Eastern Andes, Colombia 1421–1443. - An Alternative Hypothesis. In: Tankr, R., Suarez, Welsink, H.J. Corredor, F., 2003. Eastward Extent of the Late Eocene-Early Oligocene (Eds.), Petroleum basins of South America. America Association of Onset of Deformation across the Northern Andes: Constraints from Petroleum Geologist Memoir 62, pp. 647–658. the Northern Portion of the Eastern Cordillera Fold Belt, Colombia, Julivert, M., 1963. Los rasgos tectońicos de la Sabana de Bogota´ y los and Implications for Regional Oil Exploration. In: ACGGP (Ed.), mecanı´smos de formacioń de las estructuras. Boletin Geolo´gico VIII Simposio Bolivariano de Exploracioń en las Cuencas Subandinas, Universidad Industrial de Santander 15, 41–59. Cartagena de Indias, pp. 34–45. Julivert, M., 1970. Cover and basement tectonics in the Cordillera oriental Corte´s, M., 2004. Evolution Structurale du Front Centre-Occidental de la of Colombia, South America, and comparison with some other folded Cordille`re Orientale de Colombie. Ph.D. Thesis, Universite´ Pierre et chains. Geological Society America Bulletin 81, 3623–3646. Marie Curie, Paris, 350pp. Kammer, A., 1999. Observaciones acerca de un origen tranpresivo de la Corte´s, M., Angelier, J., 2005. Current states of stress in the northern Cordillera Oriental. Geologıá Colombiana 24, 29–53. Andes as indicated by focal mechanisms of earthquakes. Tectono- Macedo, J., Marshak, S., 1999. Controls on the geometry of fold-thrust physics 403, 29–58. belts salients. Geol. Soc. Am. Bull. 111, 1808–1822. Corte´s, M., Angelier, J., Colletta, B., 2005. Paleostress evolution of the Martinez, J., Vergara, L., 1999. La sucesioń Paleoambiental del Cretaćico northern Andes (Eastern Cordillera of Colombia): implications on de la Regioń de Tequendama y Oeste de la Sabana de Bogota´, plate kinematics of the South Caribbean region. Tectonics 24 Cordillera Oriental Colombiana. Geologıá Colombiana 24, 107–147. (TC1008), 27. McCourt, W.J., Aspend, J.A., Brook, M., 1984. New geological and Dahlstrom, C.D.A., 1969. Balanced cross sections. Canadian Journal of geochronological data from the Colombian Andes: continental growth Earth Sciences 6, 743–757. by multiple accretion. Journal of the Geological Society of London Dengo, C.A., Covey, M.C., 1993. Structure of the eastern Cordillera of 141, 831–845. Colombia: implications for trap Styles and regional tectonics. Amer- McLaughlin, D.H., Arce, H.M., 1975. Mapa geolo´gico del cudrańgulo ican Association of Petroleum Geologists Bulletin 77 (8), 1315–1337. Zipaquira´ (K-11), Colombia. Ingeominas, Bogota´. Dimate, C., Rivera, L., Taboada, A., Bertrand, D., Osorio, A., Jimenez, Montes, C., 2001. Three dimensional structure and kinematics of the E., Fuenzalida, A., Cisternas, A., Gomez, I., 2003. The 19 January Piedras-Girardot fold-belt in the northern Andes of Colombia. Ph.D 1995 Tauramena (Colombia) earthquake: geometry and stress regime. Thesis, The University of Knoxville, Tennessee, 217pp. Tectonophysics 363, 159–180. Please cite this article as: Martıń Corte´s et al., Structure and tectonics of the central segment of the Eastern ..., Journal of South American Earth Sciences (2006), doi:10.1016/j.jsames.2006.07.004. ARTICLE IN PRESS

M. Corte´s et al. / Journal of South American Earth Sciences xxx (2006) xxx–xxx 29

Montes, C., Baquero, M., Castillo, D., Corte´s, M., 1994. Salt-related H.J. (Eds.), Petroleum basins of South America. American Association structures postdating thrust tectonics: an example from the Cordillera of Petroleum Geologists Memoir 62, pp. 633–645. Oriental, Colombia, Abstract with programs, Annual Meeting. The Roure, F., Howell, D.G., Guellec, S., Casero, P., 1990. Shallow Geological Society Of America, Seattle, Washington. structures induced by deep-seated thrusting. In: Letouzey, J. (Ed.), Namson, J., Cunningham, R., Woodcock, G., 1994. Structural Geology Petroleum and Tectonics in Mobile Belts. Editions Technip, Paris, and hydrocarbon potential of the Northern Part of the Upper pp. 15–30. Magdalena Basin, Colombia, V Simposio de Exploracioń Petrolera Rowan, M., Linares, R., 2000. Fold evolution matrices and axial-surface en las Cuencas Subandinas, Puerto de la Cruz, Venezuela, pp. 356–364. analysis of fault-bend folds: application to the medina anticline, Ortiz, J., 1996. Geometrıá estructural del anticlinal de Nemocoń Norte y eastern Cordillera, Colombia. American Association of Petroleum su relacioń con la tectońica de sal en un cinturoń de cabalgamiento, Geologists Bulletin 84, 741–764. Cordillera Oriental, Colombia. Bc.S Thesis, Universidad Nacional de Salvador, M., 1991. Gravity field, topography and crustal structure of the Colombia, Bogota´, 80pp. North Andes. M.Sc. Thesis, University of South Carolina, South Pindell, J.L., 1985. Alleghenian reconstruction and subsequent evolution of Carolina, Columbia, 100pp. the Gulf of Mexico, Bahamas, and Proto-Caribbean. Tectonics 4, 1–39. Sarmiento, L.F., 2001. Mesozoic Rifting and Cenozoic Basin Inversion Pindell, J.L., Dewey, J.F., 1982. Permo-Triassic Reconstruction of History of the Eastern Cordillera, Colombian Andes. Ph.D Thesis, Western Pangea and the Evolution of the Gulf of Mexico/Caribbean Vrije Universiteit, Amsterdam, 295pp. Region. Tectonics 1, 179–211. Segovia, A., Renzoni, G., 1999. Geologıá del cuadrańgulo L-12, Medina. Raasveldt, H.C., 1956. Mapa geolo´gico de la Republica de Colombia, Ingeominas, Bogota´. Plancha L-9 Girardot. Ministerio de Minas y Petro´leos, Instituto Taboada, A., Rivera, L.A., Fuenzalida, A., Cisternas, A., Philip, H., Geolo´gico Nacional, Bogota´. Bijwaard, A., Olaya, J., Rivera, C., 2000. Geodynamics of the northern Raasveldt, H.C., Carvajal, J.M., 1957. Mapa geolo´gico de la Republica de Andes: subductions and intracontinental deformation (Colombia). Colombia, Plancha K-9 Armero. Ministerio de Minas y Petro´leos, Tectonics 19, 787–813. Instituto Geolo´gico Nacional, Bogota´. Trenkamp, R., Kellogg, J.N., Freymueller, J.T., Mora, H., 2002. Wide Ramirez, Q. C., 1989. Structural Style of the upper Magdalena Valley- plate margin deformation, southern Central America and northwest- Eastern Cordillera Border, Cunday-Sylvania area, Colombia. M.Sc ern South America, CASA GPS observations. Journal of South Thesis, University of South Carolina, South Carolina, 67pp. American Earth Sciences 15, 157–171. Renzoni, G., 1965. Geologıá del cudrańgulo L-11, Villavicencio. Ingeom- Ujueta, G., 1993a. Arcos y Lineamientos de Direccioń Noreste-Surest en inas, Bogota´. las cuencas subandinas de Venezuela y Colombia. Geologıá Colom- Resprepo-Pace, P.A., 1995. Late Precambrian to Early Mesozoic Tectonic biana 18, 95–106. Evolution of the Colombian Andes, Based on New Geochronological, Ujueta, G., 1993b. Lineamientos de direccioń Noroeste-Sureste en los Geochemical and Isotopic Data. Ph.D Thesis, The University of Andes Venezolanos. Geologıá Colombiana 18, 75–93. Arizona, Tucson, 194pp. Ujueta, G., 1993c. Lineamientos Muzo, Tanja y paipa en los Departa- Restrepo, P.A., 1989. Restauracioń de la seccioń geolo´gica Ca´queza - mentos de Boyaca´ y Casanare, Colombia. Geologıá Colombiana 18, Puente Quetame: Moderna interpracioń estructural de la deformacioń 65–73. del flanco este de la Cordillera Oriental. B.sc. Thesis, Universidad Ulloa, C., Acosta, J., 1978. Plancha 208, Villeta. Ingeominas, Bogota´. Nacional de Colombia, Bogota´, 65pp. Ulloa, C., Camacho, R., Escovar, R., 1975. Mapa geolo´gico del Restrepo-Pace, P.A., 1999. Fold and thrust belt along the western flank of cuadrańgulo K-12 Guateque, Colombia. Ingeominas, Bogota´. the Eastern Cordillera of Colombia: style, kinematics and timing Ulloa, C., Rodriguez, E., Acosta, J., 1993. Plancha 227, La Mesa. constrains derived from seismic data and detailed surface mapping, Ingeominas, Bogota´. Thrust tectonic conference, Royal Holloway, University of London, Wilkerson, M.S., Apotria, T., Farid, T., 2002. Interpreting the geologic pp. 112–114. map expression of contractional fault-related fold terminations: Roeder, D., Chamberlain, R.L., 1995. Eastern Cordillera of Colombia: lateral/oblique ramps versus displacement gradients. Journal of Jurassic Neogene Crustal evolution. In: Tankr, R., Suarez, Welsink, Structural Geology 24, 593–607.