The Final Phase of Tropical Lowland Conditions in the Axial Zone of The

Home , Anodontites, Early Miocene, Llanos Basin, Magdalena River Valley, Sabana Formation

Journal of South American Earth Sciences 39 (2012) 157e169

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Journal of South American Earth Sciences

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The ﬁnal phase of tropical lowland conditions in the axial zone of the Eastern Cordillera of Colombia: Evidence from three palynological records

D. Ochoa a,b,*, C. Hoorn c, C. Jaramillo a, G. Bayona d, M. Parra e, F. De la Parra f a Smithsonian Tropical Research Institute, P.O. Box 0843, Balboa, 03092 Ancon, Panama b Department of Biological Sciences, East Tennessee State University e ETSU, Johnson City, TN 37614-14850, USA c Paleoecology and Landscape Ecology, Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands d Corporación Geológica ARES, Calle 44A #53-96, Bogotá, Colombia e Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78712, USA f Instituto Colombiano del Petróleo - Ecopetrol, Km 7 vía Piedecuesta-Bucaramanga, Colombia article info abstract

Article history: Deformation of the Eastern Cordillera, as a double-verging thrust belt that separates the Magdalena Received 10 May 2011 Valley from the Llanos Basin, is a defining moment in the history of the northern Andes in South America. Accepted 2 April 2012 Here we examine the age and depositional setting of the youngest stratigraphic unit in three sectors of the Eastern Cordillera: (i) the Santa Teresa Formation (western flank), (ii) the Usme Formation (southern Keywords: central axis), and (iii) the Concentración Formation (northeastern central axis). These units were Eastern Cordillera deposited prior to the main Neogene deformation events. They represent the last preserved record of Santa Teresa Formation lowland conditions in the Eastern Cordillera, and they are coeval with a thick syn-orogenic deposition Usme Formation Concentración Formation reported in the Llanos Basin and Magdalena Valley. Based on palynological data, we conclude that the Andean orogeny upper Usme Formation was deposited during the Bartonian-earliest Rupelian? (Late Eocene-earliest Late Eocene-Early Miocene Oligocene?); the Concentración Formation was deposited during the Late Lutetian-Early Rupelian (Middle Eocene to Early Oligocene), and the upper Santa Teresa Formation was accumulated during the Burdigalian (Early Miocene). These ages, together with considerations on maximum post-depositional burial, provide important time differences for the age of initial uplift and exhumation along the axial zone and western foothills of the Eastern Cordillera. The switch from sediment accumulation to erosion in the southern axial zone of the Eastern Cordillera occurred during the Rupelian-Early Chattian (Oligocene, ca 30 to ca 26 Ma), and in the northeastern axial zone occurred prior to the latest Chattian- Aquitanian (latest Oligocene-Early Miocene ca 23 Ma). In contrast, in the western flank, the switch occurred during the Tortonian (Late Miocene, ca 10 Ma). In addition, we detected a marine transgression affecting the Usme and Concentración formations during the Late Eocene; coeval marine transgression has been also documented in the Central Llanos Foothills and Llanos Basin, as evidenced by the similarity in floras, but not in the western foothills. Our dataset supports previous sedimentological, geochemical and thermochronological works, which indicated that (i) deformation in the Eastern Cordillera was a diachronous process, (ii) the sedimentation along the axial zone stopped first in the south and then in the north during the Oligocene, (iii) depositional systems of the axial zone and central Llanos Foothills kept partly connected at least until the Late Eocene, and (iv) Miocene strata were only recorded in adjacent foothills as well as the Magdalena and Llanos basins. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction

The northern Andes Mountains are the result of a complex interaction between the continental South American plate and the * Corresponding author. Smithsonian Tropical Research Institute, P.O. Box 0843, oceanic Caribbean and Nazca plates (Fig.1). One consequence of this Balboa, 03092 Ancon, Panama. multistage orogeny was the asynchronous building of three E-mail addresses: [email protected], [email protected] different mountain belts -the Western, Central, and Eastern (D. Ochoa), [email protected] (C. Hoorn), [email protected] (C. Jaramillo), [email protected] (G. Bayona), [email protected] (M. Parra), felipe.delaparra@ Cordilleras- throughout the Mesozoic and Cenozoic (Barrero, 1979; ecopetrol.com.co (F. De la Parra). Etayo et al., 1983; Villamil, 1999). Deformation of the Eastern

Fig. 1. Geographical location of studied sections. Modiﬁed after Pardo-Trujillo (2004).CC¼ Central Cordillera, WC ¼ Western Cordillera, UMV ¼ Upper Magdalena Valley, SNSM ¼ Sierra Nevada de Santa Marta, SNCo ¼ Sierra Nevada del Cocuy, CatB ¼ Catatumbo Basin. D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169 159

Cordillera (EC), as a double-verging orogen with intermontane Table 1 basins along the axial zone (Cooper et al., 1995; Cortés et al., 2006), Location of selected sedimentary sections. was of particular significance in the geological history of northern Formation Syncline Regional location Coordinates Samples fi South America as it modi ed river drainages (Guerrero,1997; Hoorn Latitude Longitude Analyzed et al., 1995, 2010), promoted vertical surface uplift in the last N 74.63W9 e Santa Teresa Guaduas Middle Magdalena 4.86 3 5 m.y. (Gregory-Wodzicki, 2000; Mora et al., 2008b), and created Fm. Valley new habitats, such as páramos and cloud forests in the axial zone of Usme Fm. Usme Bogotá High Plain 4.52N 74.15W16 the EC (Hooghiemstra, 1984, 1988; Van der Hammen et al., 1973). Concentración Floresta Paz del Río, Boyacá 6.03N 72.76W16 Tectono-sedimentological, geodynamic and thermochronological Fm. studies have shown that the Eastern Cordillera in the Colombian Andes was already tectonically active during the Early Paleocene The fossil-rich Santa Teresa Formation was defined by De Porta (Bayona et al., 2008; Parra et al., 2012) and the Late Eocene-Early (1966) and originally thought to be the Early-Middle Miocene La Oligocene (Bande et al., 2012; Bayona et al., 2008; Gómez et al., Cira Formation (Raasveldt and Carvajal, 1957; Van der Hammen, 2005, 2003; Horton et al., 2010b; Mora et al., 2010a; Nie et al., 1958), which outcrops in the northern Middle Magdalena Valley 2010; Parra et al., 2009a, 2009b; Saylor et al., 2011; Toro et al., Basin. However, De Porta (1966) suggested a different nomination, 2004). During the Late Neogene, the tectonic activity in the assigning the Santa Teresa name for the rocks outcropping in the Eastern Andes rapidly increased (Duque-Caro, 1990; Helmens and area of the Guaduas Syncline. The formation conformably overlies Van der Hammen, 1994; Hooghiemstra and Van der Hammen, the San Juan de Río Seco Formation and is w475 m thick along the 1998; Hoorn et al., 1987; Mora et al., 2010b; Shephard et al., 2010; Bogotá-Cambao road. It has a lithofacies distinctive of quiet Taboada et al., 2000), generating a major exhumation pulse of the EC lagoonal settings (De Porta, 1966), which is partially confirmed by in the last w7 m.y. (Bayona et al., 2008; Cortés et al., 2006; Mora some forms of sapropelic organic matter (alginite and liptode- et al., 2010b). These pulses led to changes in regional climate trinite), reported in the upper half of the unit (Gómez, 2001). Acosta (Ehlers and Poulsen, 2009; Insel et al., 2009; Sepulchre et al., 2009) and Ulloa (2001) report lithofacies representative of shallow, and the sedimentary regimes in the adjacent lowlands which freshwater environments with channels filled with conglomeratic resulted in the establishment and evolution of the Amazon River and sandy lithologies, presence of several coal beds, abundant leaf (Figueiredo et al., 2009, 2010; Hoorn, 1994; Hoorn et al., 1995, 2010; impressions, fish bones, gastropods and bivalves along the Balú Hoorn and Wesselingh, 2010; Shephard et al., 2010) and increased Creek in Cundinamarca. Pilsbry and Olsson (1936), in contrast, biodiversity in western Amazonia (Hoorn et al., 2010). suggested occasional presence of salty waters based on some Both the onset of double-verging deformation of the EC and horizons with gastropods and mollusks favoring brackish waters consequent isolation of the Magdalena River Valley from the Llanos (Corbula). The age of the formation is uncertain although Oligocene region are critical to the development of the northern Andes. In (De Porta and De Porta, 1962), Late Oligocene (Acosta and Ulloa, order to understand the final phase of the sedimentation within the 2001 ), Oligocene-Early Miocene? (De Porta, 1966), and Early EC, we have dated the youngest sediments preserved in three Miocene ages (Nuttall, 1990) have been suggested based on mala- different synclines located (1) along the western flank of the EC cological and palynological data. The formation broadly correlates (Santa Teresa Formation in the Guaduas Syncline), (2) in the with the Colorado and La Cira formations in the Middle Magdalena southern axial zone of the EC (Usme Formation in the Usme Valley Basin (De Porta, 1974; Van der Hammen, 1958). Syncline, Bogotá High Plain), and (3) in the northeastern axial zone The Usme Formation was proposed by Hubach (1957) and of the EC (Concentración Formation in the Floresta Syncline, foot- Julivert (1963), it overlies the Regadera Formation. The type of wall of the Soapaga Fault) (Fig. 1). In addition, we have provided contact is variable, from unconformable in the eastern flank of the temporal estimates of the switch from burial to exhumation Usme Syncline (Hoorn et al., 1987; Julivert, 1963) to conformable in through the assessment of the magnitude of post-depositional the western flank (Julivert, 1963; Montoya and Reyes, 2005). The burial based on recently published paleothermal and thermo- Usme Formation is unconformably overlain by Late Miocene? - chronometric data. Finally, we have reviewed several depositional Pliocene alluvial, gravity-flow material and lacustrine deposits, and kinematic models to evaluate the degree of connectivity corresponding to the Marichuela Formation (De Porta, 1974; De between the basins during the Late Eocene to Early Miocene. Porta, 2003; Helmens, 1990; Helmens and Van der Hammen, 1994; Hoorn et al., 1987; Roddaz et al., 2009; Toro et al., 2003). 2. Lithostratigraphic setting The Usme Formation is w365 m thick and has been traditionally subdivided into two members (Hoorn et al., 1987; Julivert, 1963). The Late Eocene to Miocene evolution of the EC is recorded in The lower member consists dominantly of dark brown and gray- three different large synclines located across the EC (Table 1). The colored claystones, siltstones, and shales. Some dark gray silt- youngest sediments, which are preserved at the core of each stones beds are intercalated with thin coal layers and abundant syncline, also represent the youngest sediments preserved in the plant remains. A general upward-coarsening trend in grain size is EC, other than the Pliocene lake and alluvial sediments from the evident in the lower member. Towards the upper part of this Bogota High plain (Helmens, 1990; Helmens and Van der Hammen, member, some very fine to fine quartzitic sandstones with cross- 1994; Hooghiemstra and Van der Hammen, 1998; Hoorn et al., stratification are interbedded with bioturbated shales and silt- 1987). All stratigraphic sections were measured near the area stones levels (Hoorn et al., 1987; Montoya and Reyes, 2005). The where the type section of each formation was proposed (De Porta, lower member has been interpreted as coastal plain deposits 1974). In the western flank, we studied the youngest sediments of incised by subtidal channels (Hoorn et al., 1987). The upper the Guaduas Syncline, represented by the Santa Teresa Formation member of the Usme Formation is dominated by multicolored (De Porta, 1966; De Porta, 1974). In the southern axial zone, we siltstones and shales, intercalated with yellowish massive to cross- examined the youngest strata of the Usme Syncline, represented by bedded sandstones varying from coarse sand to conglomeratic the Usme Formation (De Porta, 1974; Hoorn et al., 1987). Lastly, in lithologies (Hoorn et al., 1987). Towards the top of the section, the northeastern axial zone, we studied the youngest strata of the several coal and lignite layers with abundant plant material are Floresta Syncline, represented by the Concentración Formation found. The upper member is interpreted as the product of deltaic to (Rodríguez and Solano, 2000; Ulloa et al., 2001)(Fig. 1). intertidal settings, with sand bars, and interdigitated and 160 D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169 abandoned channels (Hoorn et al., 1987). The formation has been the procedure of Punyasena et al. (2012) (Appendix 1). Additionally, dated by palynological analysis as Late Eocene to Early Oligocene a Marine Influence Index (MI) was calculated using the ratio (Hoorn et al., 1987) or Middle Eocene to Middle Oligocene (Van der proposed by Santos et al. (2008), in order to estimate the relation Hammen, 1957); whereas as Middle to Late Oligocene based on the between marine and terrestrial palynomorphs. The index was presence of Globorotalia fohsi andina (Bürgl, 1955). The Usme estimated for each sample as MI ¼ M/T, where M is the total number Formation has been correlated with the Concentración Formation of marine palynomorphs and T is the total number of paly- in the Floresta Basin (De Porta, 1974; Van der Hammen and Parada, nomorphs counted per sample (Rull, 2002; Santos et al., 2008). All 1958; Villamil, 1999) and the Upper Mirador Formation and Lower analyses were conducted using standard libraries from the program Carbonera C8 member in the Foothills and Llanos basins (Cooper R(R Development Core Team, 2009), which is a free-software, et al., 1995; Pulham et al., 1997). The Upper Mirador consists of developed by several contributors and administered by the R dark shales interbedded with fine to coarse sandstones, and the Foundation for Statistical Computing (http://www.R-project.org). Lower Carbonera is composed of tabular sandstone interbedded In addition, the Stratigraph package was used to produce the with dark gray mudstone, and flaser and lenticular lamination (De palynostratigraphic range charts (Green et al., 2010). Porta, 1974; Parra et al., 2009a). These lateral differences in lithology have been interpreted as facies changes between fluvial 4. Palynological results and marine-influenced conditions (Cooper et al., 1995; Pulham et al., 1997; Roddaz et al., 2009; Saylor et al., 2011). 4.1. Santa Teresa Formation The Concentración Formation was proposed by Alvarado and Sarmiento (1944) and conformably overlies the Picacho Forma- Palynological matter was recovered only from the upper 266 m tion (Rodríguez and Solano, 2000). It is w1 km thick and composed of the Santa Teresa Formation. The palynoflora includes a large of an upward-coarsening sequence of laminated mudstones inter- abundance of ferns spores (e.g. Psilatriletes and Laevigatosporites) bedded with sandstones (Saylor et al., 2011). Oolitic ironstones, and palms (Mauritiidites). Fungal remains are common throughout plant fragments and bioturbation are common throughout the the entire section, also a 78.5 m thick interval with abundant section (Saylor et al., 2011). The sedimentary sequence is inter- Pediastrum and Botryococcus algae was observed (from 549.74 m to preted as having formed in a coastal plain environment with 628.24 m) (Fig. 3). Neither mangrove elements nor marine paly- lagoonal to partially closed estuarine conditions (Saylor et al., 2011; nomorphs were observed (Fig. 3). The most abundant paly- Villamil, 1999). Oolitic ironstone up to 3 m thick, which is nomorphs included Mauritiidites franciscoi, Perisyncolporites commercially mined, occurs towards the base of the unit pokornyi, Magnaperiporites spinosus, Rhoipites guianensis, Psilamo- (Kimberley, 1980; Saylor et al., 2011; Van Houten, 1967). Villamil nocolpites, Laevigatosporites, Polypodiisporites and Psilatriletes (1999) interpreted these oolitic layers as evidence of a Late groups (Appendices 2 and 3). Eocene regional seaway that flooded northern South America. The co-occurrence of Magnastriatites grandiosus (First Appear- Based on palynological data, the formation has been dated as ance Datum [FAD] at 451.2 m), M. spinosus (FAD at 456.79 m), Middle Eocene to Late Oligocene (Hubach, 1957; Van der Hammen, Concavissimisporites fossulatus (FAD at 470.7 m), and Bom- 1957). Deposition of the Concentración Formation is considered bacacidites muinaneorum (FAD at 468.71 m) (Fig. 4), as well as the coeval with the active stage of the Soapaga Fault system, which overall abundance of other key taxa, such as Bombacacidites brevis, affected only the northern axial zone of the cordillera (Saylor et al., Echiperiporites akanthos, Mauritiidites franciscoi, Perisyncolporites 2011). The unit correlates with the Usme Formation in the Bogotá pokornyi, Ranunculacidites operculatus, Retitrescolpites? irregularis, High Plain area (De Porta, 1974; Van der Hammen and Parada, Spirosyncolpites spiralis, Striatriletes saccolomoides, Tetracolpor- 1958), with the Carbonera and León formations in the Catatumbo opollenites maculosus and Tetracolporopollenites transversalis, indi- Basin (De Porta, 1974; Van der Hammen, 1958), and with the Upper cates that this palynoflora corresponds to the palynological zones Mirador and Lower Carbonera formations in the Foothills and Lla- T-12 and T-13. These two zones have been dated as 16.1e23 Ma, nos basins (Cazier et al., 1995; Cooper et al., 1995; Santos et al., corresponding to the Aquitanian-Burdigalian, Miocene (Jaramillo 2008; Villamil, 1999)(Fig. 1). et al., 2011). This interpretation is supported by maximum likelihood analysis (Fig. 5), which indicates a high probability of corre- 3. Methods lation with the upper part of palynological zone T-12 Horniella lunarensis and zone T-13 Echitricolporites maristellae (Burdigalian, A total of 41 samples from the three formations (Table 1)were 19e16 Ma). processed for palynological analysis following standard procedures (Traverse, 2007). All samples were digested by using 10% HCl and 40% HF. Each sample was sieved using 10 mm and 100 mm meshes; 4.2. Usme Formation finally, permanent montages were prepared. Light microscopy was used to examine the palynological content and at least 100 grains Good pollen recovery was found for most of the section, except were counted per slide. Morphological features were compared for the lower 116 m and the uppermost 60 m, where no pollen was with descriptions and illustrations from various resources (Dueñas, found. The palynoflora is characterized by high abundances of fern 1980; Germeraad et al., 1968; Gonzalez, 1967; Hoorn et al., 1987; spores (e.g. Polypodiisporites and Laevigatosporites) and palms (e.g. Jaramillo et al., 2010; Jaramillo et al., 2007; Jaramillo and Dilcher, Mauritiidites)(Appendices 4 and 5). Four levels contain dinofla- 2001; Jaramillo et al., 2011; Leidelmeyer, 1966; Lorente, 1986; gellate cysts and acritarchs (2140 m, 2141 m, 2152 m, and 2258 m). Muller et al., 1987; Van der Hammen, 1956; Van der Hammen and Levels located towards the base of the upper member exhibit the García de Mutis, 1966) and taxonomical nomenclature followed highest Marine Influence Index values (at 2140 m, 2141 m and Jaramillo and Dilcher (2001). 2152 m, MI ¼ 0.05, 0.09 and 0.029, respectively), whereas marine The sections were dated using a maximum likelihood estima- influence was minimal at the top of the section, at 2258 m tion based on the palynological zonation proposed by Jaramillo (MI ¼ 0.012) (Fig. 3). Colonies of Pediastrum sp. were common et al. (2011), which has been time-calibrated using carbon between 2140 m and 2142.6 m, and high frequencies of mangrove isotopes, radiometric dating, foraminifera and magnetic- elements (Rhizophoraceae and Pellicieraceae) occurred between stratigraphy data (Fig. 2). Maximum likelihood analysis follows 2258 m and 2299 m (mean 5.6%) (Fig. 3). D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169 161

Fig. 2. Palynological zonation proposed for the Cenozoic of the Llanos and Llanos Foothills by Jaramillo et al. (2011) and Muller et al. (1987). Geologic time scale after Gradstein et al. (2004). 162 D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169

Fig. 3. Relative abundances of terrestrial plants, marine and fresh waters elements present in each unit. Marine Inﬂuence (MI) Index values ranges from 0 (fully terrestrial) to 1 (fully marine). Palynological zones after Jaramillo et al. (2011). Vertical scales vary in each section.

The most common angiosperm taxa recovered include M. fran- dated as Late Eocene (38e 33.9 Ma) (Jaramillo et al., 2009, 2011) ciscoi, Echitriporites trianguliformis orbicularis, Longapertites prox- (Fig. 2). This dating is also supported by the maximum likelihood apertitoides var. proxapertitoides, P. pokornyi, R. guianensis, T. analysis, which indicates a high probability of correlation with zone maculosus, T. transversalis, and the Psilamonocolpites and Reti- T-07 Echitriporites trianguliformis orbicularis for the entire section, tricolporites groups. except for the last sample (Fig. 5). Cicatricosisporites dorogensis and the Laevigatosporites, Poly- Only one sample with poor recovery (2354 m) was obtained podiisporites, and Psilatriletes groups dominated pteridophyte from the uppermost 60 m of section. Among other taxa, F. hammenii spores composition. Other important taxa recovered include Are- was recovered in this sample. The LAD of F. hammenii is considered cipites regio, Cricotriporites guianensis, E. akanthos, Echitetracolpites? as an important biostratigraphic event and was estimated at tenuiexinatus, Foveotriporites hammenii, Lanagiopollis crassa, 33.24 Ma (Jaramillo et al., 2011). Based on the presence of this Monoporopollenites annulatus, Poloretitricolpites absolutus, Spi- taxon, we consider the upper sediments to be no younger than rosyncolpites spiralis, Syncolporites marginatus and Zonocostites early Oligocene (earliest Rupelian, ca 33 Ma). In consequence, we ramonae (Appendices 4 and 5). Echitriporites trianguliformis orbi- suggest a Bartonian-earliest Rupelian? age (ca 38 to 33 Ma) for the cularis occurs throughout the section, except for the uppermost upper-lower to upper Usme Formation. sample, at 2354 m. A single occurrence of C. fossulatus was also found at 2254 m (Fig. 4). 4.3. Concentración Formation The frequent occurrence of Echitriporites trianguliformis orbicularis, along with the Last Appearance Datum [LAD] of A. regio (at Good pollen recovery was obtained in almost the entire 2254 m), S. marginatus (at 2294 m) and Echitetracolpites? tenuiex- sequence except for the upper part of the section, where palyno- inatus (at 2299 m), the FAD of E.chiperiporites akanthos (at 2254 m), logical recovery was poor (1211 me1440 m) (Appendices 6 and 7). and the presence of P. absolutus (single occurrence at 2267 m) The palynoﬂoral assemblage is dominated by fern spores (C. dor- (Fig. 4) indicates that up to meter 2299 the palynoﬂora belongs to ogensis, Laevigatosporites, M. grandiosus, and Polypodiisporites) and palynological zone T-07 Echitriporites trianguliformis orbicularis, angiosperms including M. franciscoi, Psilamonocolpites medius, T. D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169 163

Fig. 4. Palynological zones established for each section. Arrows indicated the occurrence of key taxa used to deﬁne the palynological zones. Note Santa Teresa Formation includes from the upper part of zone T-12 to zone T-13, Usme Formation only includes zone T-07 and Concentración Formation includes from zone T-06 to T-09. Vertical scales vary in each section.

maculosus, T. transversalis, and L. crassa. Three peaks of mangrove 5. Discussion of palynological data abundance (L. crassa, a Pellicieraceae) occur throughout the section at 40.49 m (23.7% of the palynoflora), 559.99 m (11.5%), and 5.1. Age between 774.49 m and 832 m (47%) (Fig. 3). Three intervals with increased abundances of freshwater algae were found at 40.49 m We found that the upper sediments of the Santa Teresa (0.7%), from 360 m to 391.49 m (0.6%) and from 715.49 m to Formation (corresponding to the uppermost 266 m) have a high 751.49 m (1.5%). Four intervals displaying high MI values were probability of belonging to the upper part of palynological zone T- found at 40.49 m (MI ¼ 0.13), at 560 m (MI ¼ 0.019), from 751.49 m 12 H. lunarensis and zone T-13 E. maristellae (Burdigalian, Early to 774.5 m (MI ¼ 0.02), and from 797.5 m to 832.49 m (MI ¼ 0.15) Miocene, 19e16 Ma) (Figs. 4 and 5). Earlier stratigraphic, malaco- (Fig. 3). logical and palynological studies considered the formation as The palynoflora indicates the presence of four palynological having accumulated during the Oligocene (De Porta and De Porta, zones as follows: zone T-06 Spinizonocolpites grandis from the base 1962), Late Oligocene (Acosta and Ulloa, 2001), Oligocene to Early to 116.9 m; zone T-07 Echitriporites trianguliformis orbicularis from Miocene? (De Porta, 1966) or Early Miocene (Nuttall, 1990). 116.9 m to 735.5 m; zones T-08 Nothofagidites huertasii to T-09 De Porta and De Porta (1962) studied the palynological associ- Foveotricolporites etayoi from 735.5 m to 1210.5 m. ations within the section and reported occurrences of Poly- Palynological zone T-06 is identified by the LAD of S. grandis (at podiisporites usmensis, Psilamonocolpites, Mauritiidites and 116.9 m) (Fig. 4). In addition, it is supported by the co-occurrence of Psilatriletes groups, and by using the relative abundance of each C. dorogensis, Laevigatosporites catanejensis and R. guianensis, all of group, they correlated the section with the Oligocene zones which have their FADs at 40.49 m. Palynological zone T-07 is indi- proposed by Van der Hammen (1958). Van der Hammen’s zones are cated by the LADs of Echitriporites trianguliformis orbicularis (at based on abundance peaks of broad categories that represent 735.5 m), Proxapertites magnus (at 391.4 m), and Racemonocolpites modifications in the vegetation due to regional climatic changes. facilis (at 371.9 m), and by FADs of Striatriletes saccolomoides (at Thus, each abundance cycle had a certain chronostratigraphic value 559.9 m) and Polypodiisporites usmensis (at 391.49 m) (Fig. 4). The according to the climate variation. This methodology has been occurrence of Echitetracolpites? tenuiexinatus (at 334.49 m) also described as inappropriate for biostratigraphic purposes (Jaramillo supports this zone. Finally, zones T-08 N. huertasii toT-09 F etayoi are et al., 2011; Moore et al., 1991), because it depends on factors such noted by the FAD of M. grandiosus (at 1101.0 m), and the LAD of as environmental settings during deposition, type of sediments Spinizonocolpites echinatus (at 797.49 m) (Fig. 4). Zone T-09 is also sampled, and it is also greatly affected by the “closed sum” math- supported by high abundances of C. dorogensis, occurring towards ematical effect (Kovach and Batten, 1994; Moore et al., 1991). the top of the section (see Appendices 6 and 7). These four palyno- Furthermore, Van der Hammen’s approach did not use an external logical zones, also supported by the maximum likelihood analysis age-dataset for calibration. (Fig. 5), indicate a Lutetian-Early Rupelian (Middle Eocene-Early De Porta (1966) suggested an Oligocene to Early Miocene? age. Oligocene, ca 39 to 31.5 Ma) age for the Concentración Formation. He established the Oligocene age by using the stratigraphic position 164 D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169

Likewise, Nuttall (1990) assigned an Early Miocene age after reviewing the malacological material collected and described by Anderson (1929). Although both studies assigned an Early Miocene age to the fauna, they also discussed extensively the uncertainty of the exact stratigraphic position of this association within the Gua- duas Syncline. Furthermore, Nuttall (1990) pointed out that there is no precise information indicating that the mollusk fauna actually belongs to any level from the Guaduas structure. He also argued that Butler (1939) tentatively located the fauna close to the core of the Guaduas Syncline, and as a result, the mollusk assemblage has been placed at the upper part of the Santa Teresa Formation. In addition to the stratigraphic uncertainty, De Porta (1966) signaled that the correlation with the Miocene La Cira Formation based on the mollusk fauna was biased by the high frequency of endemic species within the Santa Teresa Formation. Consequently, De Porta (1966) and Nuttall (1990) concluded that although the fauna probably could suggest an Early Miocene age, the certainty of the dating was very low. The new palynological data presented herein supports a Burdigalian, Miocene (19e16 Ma) age for the upper sediments from the Santa Teresa Formation (Figs. 4 and 5). However, the lower part of the Santa Teresa still needs to be dated. The palynofloral assemblage recovered from upper part of the lower Usme Formation and lower part of the upper Usme Forma- tion corresponds to palynological zone T-07 Echitriporites trianguliformis orbicularis of Jaramillo et al. (2011) (Figs. 4 and 5), which is dated as Late Bartonian-Priabonian, Eocene (38e33.9 Ma) (Fig. 2). The uppermost 60 m of the section did not provide conclusive evidence supporting zone T-07, and it contains F hammenii, a taxon whose extinction is estimated at 33.24 Ma (Jaramillo et al., 2011). Therefore we consider the upper-lower and upper Usme Formation as Bartonian to earliest? Rupelian (Late Eocene to earliest? Oligo- cene, 38e33 Ma) in age. Van der Hammen (1957) dated the Usme section as Middle Eocene to Middle Oligocene, based on the stratigraphic position of the unit and occurrence peaks of Striatriletes susannae, a junior synonym of C. dorogensis (Potonie and Johann, 1933). As discussed before, age dating based on vegetation cycles may be biased because it may signal ecological settings rather than chronological events. Hoorn et al. (1987), following the palynological zonation proposed by Muller et al. (1987), designated a Late Eocene-Early Oligocene age by correlation with the Echiperiporites estelae and Magnastriatites-Cicatricosisporites Zones (see Fig. 2). The latter zone was supported by the co-occurrence of M. grandiosus and C dorogensis in the uppermost part of the Usme Formation. We carefully reanalyzed the same palynological slides examined by Hoorn et al. (1987) but never detected the presence of M. grandiosus. Moreover, we did not find M. grandiosus in additional samples from the rest of the section. It is possible that large specimens of C. dorogensis sometimes can be confused with small specimens of M. grandiosus, and this could be the case in Hoorn et al.’s (1987) work. The palynoflora recovered from the Concentración Formation ranges from the upper T-06 S. grandis to T-09 F. etayoi of Jaramillo et al. (2011) (Figs. 4 and 5). Thus, we interpret the lower 1210 m Fig. 5. Stratigraphic age estimates per section calculated using the probabilistic of the section as having accumulated during the Late Lutetian to Maximum Likelihood approach based on the taxa abundance. Normalized likelihood Early Rupelian (latest Middle Eocene to early Early Oligocene, 39 to values are represented by color with higher and lower likelihood values symbolized by green and blue, respectively. Inferior axis showing geologic time (Ma), vertical axis 31.5 Ma). Because we did not recover pollen from the upper representing depth and superior axis marking the palynological zones proposed by w240 m, we were unable to directly establish the depositional age Jaramillo et al. (2011). Vertical scales vary in each section. Samples are represented by for this segment. Nevertheless, we estimate the approximate age at yellow bars. the top of the formation as Rupelian (ca 31.5 Ma), by assuming constant sedimentation rates in the upper 240 m, and by using the FAD of M. grandiosus within the section (1101.0 m) as age reference of the section and previous palynological data as discussed above (ca 33.67 Ma, according to Jaramillo et al., 2011). (De Porta and De Porta, 1962), whereas the Early Miocene? age was Van der Hammen (1957) dated the Concentración Formation as based on the mollusk association Anodontites laciranus, Hemisinus extending from the Middle Eocene to the earliest Late Oligocene waringi and Diplodon opocitonis described by Anderson (1929). based on vegetational abundance peaks. As in the case of the Usme D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169 165

Formation, he based the Oligocene age mainly on high occurrences environments (Cooper et al., 1995) and contains both marine of Striatriletes susannae, a junior synonym of C. dorogensis (Potonie palynomorphs and mollusks (Gómez et al., 2009; Jaramillo et al., and Johann, 1933). Van der Hammen confirmed this age by using 2011). The pattern suggests that Santa Teresa, Barzalosa and the a coal seam from the Usme Formation, which was previously dated upper Mugrosa formations were part of a large lacustrine system as Middle Oligocene also on the basis of a peak in C. dorogensis (Van along the Magdalena River Basin, whereas the Llanos Basin was der Hammen,1957). Given that non-independent data were used to already separated from the Magdalena Basin and part of a different constrain the chronostratigraphic frame in both the Usme and drainage basin. This conclusion is also supported by the detrital Concentración formations, the dating may have relied on circular zircon analysis of Horton et al. (2010b), who found a significant reasoning. Nevertheless, the age proposed by Van der Hammen is absence of MesozoiceCenozoic zircons in Middle and Late Miocene similar to the age proposed here. samples from the Guayabo and Corneta formations (Llanos Basin); The dating established herein implies a revision of the tradi- this was attributable to the effective topographic barrier created by tional chronostratigraphic correlations for the Eastern Cordillera. In the EC by the Middle Miocene, which separated the Central particular, the Usme and Concentración formations have generally Cordillera source area from the Llanos Basin. Our data suggest that been considered as coeval units (Gómez et al., 2005; Van der this barrier was already present by the Early Miocene. However, Hammen, 1957, 1958), deposited during the Middle Eocene- given that the Santa Teresa palynological record contains abundant Middle Oligocene. As shown here, the upper boundaries of the floristic elements from lowland regions and none from Andean or two formations are not coeval (see Figs. 4 and 5). The uppermost páramo vegetation, this topographic barrier apparently did not part of the Usme Formation is dated as Bartonian-earliest Rupelian? reach elevations higher than 1000 m by the Early Miocene. (33.9 to ca 33 Ma), whereas the youngest dated strata of the Con- The Usme palynoflora, with common presence of mangrove and centración Formation are at least Early Rupelian (ca 31.5 Ma). marine elements (Fig. 3) together with high abundances of lowland Nevertheless, lithological features in both formations indicate that terrestrial floras, suggests that accumulation took place in coastal they share similar depositional settings (Hubach, 1957) and periods plains with tidal influence, as had been suggested herein and of marine influence (see Section 8). previously (Hoorn et al., 1987; Montoya and Reyes, 2005). A well- defined marine flooding event in the middle part of the forma- 5.2. Paleoenvironments tion (2130 me2160 m) is indicated by the MI index (Fig. 3). A similar marine flooding event in the Late Eocene has already been The pollen association from all three sites is indicative of identified in the Central Llanos and Llanos Foothills basins (Santos lowland regions (e.g. Mauritiidites, P. pokornyi, L. crassa, R. guia- et al., 2008). The presence of Late Campanian-Maastrichtian paly- nensis, Spirosyncolpites spiralis). No pollen or spore species typical nomorphs (Buttinia andreevi and Syndemicolpites typicus) within of Andean or páramo vegetation (Hooghiemstra et al., 1993; the recovered palynoflora (Appendices 4 and 5) indicates an active Hooghiemstra and Ran, 1994; Van der Hammen et al., 1973; erosional recycling from Campanian-Maastrichtian rocks (Guada- Wijninga, 1996) were found. lupe-Guaduas formations?). The palynofloral assemblage recovered from the Santa Teresa The palynoflora of the Concentración Formation is similar to Formation is typical for wetlands and swampy areas and, mostly that of the Usme Formation having moderate abundances of both restricted to freshwaters conditions, as neither mangrove elements mangrove and marine elements (Fig. 3), together with high abun- nor marine palynomorphs were found. Furthermore, a freshwater dances of terrestrial lowland floras. This corroborates previous (lacustrine) interval was also inferred from high abundances of suggestions that accumulation took place in coastal plains with both Botryococcus sp. and Pediastrum sp. (549.74 me628.24 m) tidal influence (Saylor et al., 2011; Villamil, 1999). There are three (Fig. 3). We agree with the conclusions of previous works that the distinctive marine intervals (Fig. 3). The first event occurs within upper part of this unit was formed in a lacustrine setting (Acosta zone T-06 (40.49 m) during the Middle Eocene (Bartonian), the and Ulloa, 2001; De Porta, 1966). De Porta (1966) suggested that second within zone T-07 (560 m) during the Late Eocene (Priabo- the sedimentary sequence was formed in a lagoonal setting but nian) and third within the uppermost T-07 to the lower T-08 zone with occasional connections to the sea based on the presence of (751.49 me832.49 m), during the latest Eocene to Early Oligocene brackish-water mollusks and gastropods reported by Anderson (latest Priabonian to Early Rupelian) (Fig. 3). A Middle Eocene (1929). However, Nuttall (1990) revisited the fauna described by marine event that has been identified in the central Llanos Foothills Anderson, and he concluded that neither of the two reviewed (Jaramillo and Dilcher, 2001), in the middle of the Mirador genera ascribed to the section (Pachydon and Verena)isadefinitive Formation, can be correlated with the first marine interval indicator of brackish waters. Moreover, living species from the (40.49 m). Another flooding event during the Late Eocene can be genus Verena are salinity intolerant and therefore restricted to correlated with the event observed in Usme, which is registered freshwater environments (Nuttall, 1990). Consequently, there is no throughout the Llanos and Llanos Foothills basins (Santos et al., evidence supporting a connection to the sea. 2008). Our results agree with previous MI values reported by Similar lacustrine conditions have been reported for the upper Santos et al. (2008) for the Paz del Río area (MI < 0.02) (Fig. 3). Mugrosa (Middle Magdalena Valley) and Barzalosa formations Santos et al. (2008) proposed that a NWeSE marine incursion (Upper Magdalena Valley). The upper part of the Early Miocene entered via the Lower Magdalena Valley and inundated the basin Mugrosa Formation (Caballero et al., 2010; Hubach, 1957) is a thick up to the Central Llanos Foothills. In this way, marginal marine and lacustrine deposit (Nuttall, 1990), which might correlate with the estuarine settings were established along the northern axial zone lacustrine levels of Santa Teresa. Likewise, the Barzalosa Formation of the Eastern Cordillera. Our results support their interpretation. (De Porta, 1966) consists of multicolored mudstones interbedded The Early Rupelian (Early Oligocene) flooding corresponds to with some conglomeratic and gravel levels and contains thick a maximum flooding surface that has been identified at several lacustrine deposits characterized by blue and green claystones of sites in Colombia and Ecuador including the lower Orteguaza Early Miocene age (De Porta, 1966). On the other side of the EC, the Formation in the Putumayo Basin (Christophoul et al., 2002; Early Miocene C2 member of the Carbonera Formation was Jaramillo et al., 2011; Osorio et al., 2002). This flooding has been continuously deposited in the easternmost flank of the EC (Parra identified in the southern part of the Upper Magdalena Valley et al., 2009a) and in the Llanos Basin, east of the EC (Cooper et al., (Neiva Subbasin), the Putumayo Basin (Osorio et al., 2002) to the 1995). The C2 accumulated in marine-influenced coastal plain north (Fig. 1), and the Marañon Basin (Christophoul et al., 2002). 166 D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169

6. Overburden (Section 5.1) exposes the difference between the preserved sediments and those that should have been accumulated but were lost Vitrinite reflectance (Ro) data in strata from the Santa Teresa by erosion, thus providing further evidence that the youngest Formation in the Guaduas Syncline show Ro values of 0.54e0.60% preserved sediments may not represent the last deposited (Gómez, 2001; Gómez et al., 2003), which represent maximum sediments. temperatures of w95e105 C for heating rates of 2e10 C, The Ro/thermochronology ages reported herein agree with according to the kinetic model of Burnham and Sweeney (1989). previous thermochronological, structural, and sedimentological In the absence of evidence of other heating mechanisms, we data (e.g. detrital zircon UePb ages, apatite-fission tracks, and calculate that 2.5e4.5 km of overburden, with a thermal gradient of paleocurrents data), which indicate that initial exhumation of the 20e30 C/km and a surface temperature of 25 C -similar to Eastern Cordillera took place during the Late Eocene-Early Oligo- present-day values- would account for the observed Ro values. cene (see Fig. 10 in Horton et al., 2010b)(Bande et al., 2012; Bayona There are no robust constraints on the time associated with the et al., 2008; Horton et al., 2010b; Mora et al., 2010a; Moreno et al., accumulation of such eroded overburden. However, Gómez (2001) 2011; Nie et al., 2010; Parra et al., 2009b; Saylor et al., 2011; Toro calculated a concordant apatite-fission track (AFT) age of et al., 2004). Evidence from the Usme Syncline (i.e. UeTh/He in 12.1 2.3 Ma (1s error) from sandstones of the Oligocene San Juan apatite and lithological features) indicates onset of exhumation by de Río Seco Formation [Ro ¼ 0.64%; Temp ¼ 115 C], in the Guaduas the end of the Eocene (Bayona et al., 2010). All these sets of data Syncline, by using 20 apatites with average chlorine content of combined suggest that sedimentation indeed ceased in the 0.34%. An in-depth analysis of these data shows that a kinetic southern axial zone of the Eastern Cordillera by the Early Oligo- population of 19 apatites with chlorine content of 0.1% has an AFT cene. Our data also support the hypothesis of a heterogeneous age of 8.1 2.3 Ma. We thus interpret this cooling age of 6e10 Ma in Neogene uplifting process across the EC (Bande et al., 2012; Bayona samples that attained temperatures for full thermal resetting of et al., 2008; Horton et al., 2010a; Mora et al., 2008a, 2010a, 2006, fluorapatites as a reasonable approximation for the age of end of 2010b; Moreno et al., 2011; Parra et al., 2009b), being older in burial and accumulation. the axial zone and having younger phases at the eastern and In the Usme Syncline, a Ro value of 0.27% in the Usme Formation western flanks, and being older in the south than the north of the (Mora et al., 2008b) documents burial temperatures lower than axial EC. 50 C. Using similar surface temperature and geothermal parame- ters as for the Guaduas Syncline, these paleotemperatures corre- 8. Regional implications spond to up to w1 km of overburden. Apatite (UeTh)/He thermochronology (closure temperature w70 C) in two sand- Three different tectonic scenarios have been proposed to explain stone samples from the lower part of the Bogotá Formation along the Cenozoic tectonic development of the axial zone of the EC and its western limb shows highly reproducible ages (samples C540 and adjacent Magdalena and Llanos basins to the west and east, D937, palynologically dated as Middle/Late Paleocene and Early respectively. According to the first model, the EC corresponds to Eocene, respectively; see Bayona et al., 2010), based on 4 aliquots a large foreland basin system, including what are now the Llanos per sample, of 30.7 1.8 Ma and 26.4 1.6 Ma (Bayona et al., 2010). and the Magdalena Valley basins (Cooper et al., 1995; Villamil, These data reveal ongoing exhumation in the western limb of this 1999). Initial breakup of the foreland basin occurred during the syncline by Late Eocene-Oligocene times. We believe that ca Late Oligocene, with a complete segmentation by the Middle 30e26 Ma is also a maximum age for the switch from sediment Miocene. The second model considers a fragmentation of a contin- accumulation and burial to non-deposition in the core of the uous Paleocene foreland basin during the Middle-Late Eocene, with syncline, where the Usme strata are preserved. complete isolation of the Llanos from the Magdalena Basin occur- Paleotemperature estimates based on Ro and AFT data for the ring by the Early-Middle Oligocene (Gómez et al., 2005; Horton Cenozoic units in the Floresta area are highly variable (Mora et al., et al., 2010a, 2010b; Moreno et al., 2011; Nie et al., 2010; Parra 2010a), indicating a greater magnitude of burial the farther to the et al., 2009a; Saylor et al., 2011). A third model proposes that north in the direction of the El Cocuy area (see Fig. 1). In the north, a syn-orogenic basin to the east of the Central Cordillera was at w6200, the Concentración Formation has a Ro value of 0.80%, interrupted by several localized uplifts throughout the EC (Bayona corresponding to a temperature of 140e150 C, whereas 30 km to et al., 2008; Fabre, 1987; Sarmiento-Rojas, 2001; Shagam et al., the southwest Ro is 0.71% (temperature w115e130 C). Based on 1984). These intrabasinal uplifts, which would give rise to the considerations cited above, these estimates represent burial multiple intermontane basins, are the result of latest Cretaceous- exceeding 4e6 km in the north and 1 km less in the southern area Middle Eocene events of tectonic deformation. sampled. Thermal histories derived from Ro and AFT data in both The biostratigraphic data presented here indicate that the last areas are consistent with an onset of exhumation occurring ca preserved record of sedimentation along the present EC are not 23e20 Ma (Mora et al., 2010a). coeval. Sediments were accumulated and preserved until the latest Bartonian-earliest Rupelian? (Late Eocene-earliest Oligocene?) in 7. Stepwise cessation in sediment preservation along the the southern central region (Usme Formation) and at least until the Eastern Cordillera Early Rupelian (Early Oligocene) in the northeastern central region (Concentración Formation), long before the major latest Miocene- The transition from burial to exhumation occurred first in the Pliocene uplift of the EC (Van der Hammen et al., 1973). In southern central axial zone of the Eastern Cordillera (Usme contrast, the western foothills (Santa Teresa Formation) and eastern Formation) during the Rupelian-Early Chattian (ca 30eca 26 Ma). foothills (Carbonera Formation) (Parra et al., 2009a) continued Subsequently, sediment accumulation stopped along the north- accumulating sediments during the Miocene. These marked time eastern axial zone of the Eastern Cordillera (Concentración differences of the youngest preserved units across the EC suggest Formation) not before the Late Chattian (ca 23 Ma); and finally, it that a single foreland that covered the Magdalena Valley, EC and the was not until the Late Miocene (ca 10e6 Ma) that exhumation was Llanos Basin was disrupted in the earliest Oligocene prior to the initiated along the western flank of the Eastern Cordillera (Santa onset of major Late Neogene exhumation pulses, in contrast to the Teresa Formation). The observed age differences between the Ro/ simpler model that was proposed during the 1990s (Cooper et al., thermochronology estimates and the reported palynological dating 1995; Villamil, 1999). D. Ochoa et al. / Journal of South American Earth Sciences 39 (2012) 157e169 167

Our palynological results indicate that during the Late Eocene References the Usme and Concentración formations were part of the Central Llanos Foothills and Llanos Basin, as evidenced by the similarity in Acosta, J., Ulloa, C.E., 2001. Memoria explicativa de la plancha 227 La Mesa, escala fl fl 1:100.000. Ingeominas, Bogotá, p. 79. oras and the ooding event observed across this basin (Fig. 3), Alvarado, B., Sarmiento, R., 1944. Informe Geológico Sobre los Yacimientos de suggesting that depositional systems of the Llanos-EC basin were Hierro, Carbón y Caliza de la Región de Paz del Río. In: Servicio Geológico still connected. Growth strata in the western flank of the EC and Nacional. Departamento de Boyacá, Bogotá, Informe 468 (unpublished), p. 132. Anderson, F.M., 1929. Marine Miocene and related deposits of North Colombia. Magdalena Basin that record west-verging deformation of the Proceedings of the California Academy of Sciences 18, 73e212. western flank of the EC (Cortés et al., 2006; Gómez et al., 2003) Bande, A., Horton, B.K., Ramírez, J.C., Mora, A., Parra, M., Stockli, D.F., 2012. Clastic mark the westernmost boundary of depositional systems within deposition, provenance, and sequence of Andean thrusting in the frontal the Llanos-EC basin. The connection of this large depositional Eastern Cordillera and Llanos foreland basin of Colombia. Geological Society of America Bulletin 124, 59e76. system between the EC and the Llanos probably was broken during Barrero, L.D., 1979. Geology of the Central Western Cordillera, West of Buga and the earliest Oligocene, as has been suggested by the models of Roldanillo, Colombia. Instituto Colombiano de Geología y Minería-INGEOMI- Gómez et al. (2005), Parra et al. (2009a), Horton et al. (2010b) and NAS, Bogotá, Colombia, p. 75. Bayona, G., Cortés, M., Jaramillo, C., Ojeda, G., Aristizabal, J.J., Reyes-Harker, A., 2008. Saylor et al. (2011). This is further supported by the similarity An integrated analysis of an orogenesedimentary basin pair: latest Creta- between depositional environments of the EC, Llanos Foothills, and ceouseCenozoic evolution of the linked Eastern Cordillera orogen and the Magdalena Valley basins until the Late Eocene (Parra et al., 2009a; Llanos foreland basin of Colombia. Geological Society of America Bulletin 120, 1171e1197. Saylor et al., 2011). Bayona, G., Montenegro, O., Cardona, A., Jaramillo, C., Lamus, F., Morón, S., Quiroz, L., Ruiz, M.C., Valencia, V., Parra, M., Stockli, D.F., 2010. Estratigrafía, procedencia, subsidencia y exhumación de las unidades Paleógenas en el Sinclinal de Usme, 9. Conclusions sur de la zona axial de la Cordilla Oriental. Geología Colombiana 35, 5e35. Bürgl, H., 1955. Globorotalia fohsi en la Formación de Usme. Boletín Geológico del Servicio Geológico Nacional 3, 56e65. Biostratigraphic data from the youngest sediments preserved Burnham, A.K., Sweeney, J.J., 1989. A chemical kinetic model of vitrinite maturation in all three synclines indicate different ages associated with the and reflectance. Geochimica et Cosmochimica Acta 53, 2649e2657. uppermost formations in each stratigraphic sequence. We esti- Butler, J.W., 1939. Geology of middle and upper Magdalena valley. World Petroleum 10, 95e100. mated the age of the sediments from the Usme Formation (Usme Caballero, V., Parra, M., Mora, A.R., 2010. Late Eocene - Early Oligocene initial uplift Syncline) as Bartonian-earliest Rupelian? (38e33 Ma), from the of the Oriental cordillera of Colombia: sedimentary provenance on the Nuevo e Concentración Formation (Floresta Syncline) as Late Lutetian- Mundo syncline, middle Magdalena basin. Boletín de Geología 32, 45 77. e Cazier, E.C., Hayward, A.B., Espinosa, G., Velandia, J., Mugniot, J.F., Leel Jr., W.G., 1995. Early Rupelian (39 31.5 Ma), and uppermost Santa Teresa rocks Petroleum geology of the Cusiana Field, Llanos basin foothills, Colombia. (Guaduas Syncline) as Burdigalian (19e16 Ma). In addition, the American Association of Petroleum Geologists Bulletin 79, 1444e1463. combination of biostratigraphic, thermochronometric, and pale- Christophoul, F., Baby, P., Dávila, C., 2002. Stratigraphic responses to a major tectonic event in a foreland basin: the Ecuadorian Oriente Basin from Eocene to othermometric data suggests that cessation of sediment accu- Oligocene times. Tectonophysics 345, 281e298. mulation in the EC was diachronous. In the southern axial zone of Cooper, M.A., Addison, F.T., Alvarez, R., Coral, M., Graham, R.H., Hayward, A.B., the Eastern Cordillera (Usme Syncline), the shift from sediment Howe, S., Martínez, J., Naar, J., Penas, R., Pulham, A.J., Taborda, A., 1995. Basin development and tectonic history of the Llanos basin, eastern cordillera, and accumulation and burial to non-deposition occurred during the middle Magdalena valley, Colombia. American Association of Petroleum Geol- Late Rupelian-Early Chattian (ca 30e26 Ma), whereas in the ogists Bulletin 79, 1421e1443. northeastern axial zone of the Eastern Cordillera (Floresta Cortés, M., Colletta, B., Angelier, J., 2006. Structure and tectonics of the central segment of the Eastern Cordillera of Colombia. Journal of South American Earth Syncline) it was estimated as latest Chattian-Aquitanian (ca Sciences 21, 437e465. 23e20 Ma); and in the western flank (Guaduas Syncline) as De Porta, J., 1966. Geología del extremo sur del Valle Medio del Magdalena. Boletín Tortonian-Messinian (10e6 Ma). These estimates agree with dates de Geología 22e23, 347. of published ages of exhumation of the EC, suggesting that the De Porta, J., 1974. Lexique Stratigraphique International. In: Amerique Latine; fascicule 4b; Colombie (deuxième partie), Tertiaire et Quaternaire, vol. V. process of uplifting of the EC is very complex and happened in International Union of Geological Sciences, Paris, p. 651. several steps. Finally, the palynoflora indicates the exclusive De Porta, J., 2003. La formación del Istmo de Panamá: su incidencia en Colombia. Revista e presence of lowland plant communities in all three areas, de la Academia Colombiana de Ciencias Exactas. Fisicas y Naturales 27, 191 216. De Porta, J., De Porta, S., 1962. Discusión sobre las edades de las formaciones Hoyón, including the Burdigalian (Early Miocene) Santa Teresa Forma- Gualanday y La Cira en la región de Honda-San Juan de Río Seco. Boletín de tion, suggesting that the EC still was less than 1000 m in elevation Geología 9, 69e85. by the Early Miocene. Lowland conditions in the area of the Dueñas, J.H., 1980. Palynology of Oligocene-Miocene strata of borehole Q-E-22, Planeta Rica, Northern Colombia. Review of Palaeobotany and Palynology 30, present EC gradually ended between the Oligocene and the Late 313e328. Miocene. Duque-Caro, H., 1990. The Choco Block in the northwestern corner of South America; structural, tectonostratigraphic, and paleogeographic implications. Journal of South American Earth Sciences 3, 71e84. fl Acknowledgments Ehlers, T.A., Poulsen, C.J., 2009. In uence of Andean uplift on climate and paleo- altimetry estimates. Earth and Planetary Science Letters 281, 238e248. Etayo, F., Barrero, D., Lozano, H., Espinosa, A., González, H., Orrego, A., Ballesteros, I., We thank the Colombian Petroleum Institute, the Smithsonian Forero, H., Ramirez, C., Zambrano, F., Vargas, R., Tello, A., Alvarez, J., Ropain, C., Tropical Research Institute, the Corporación Geológica Ares, and Cardozo, E., Galvis, N., Sarmiento, L., Duque, H., Albers, J.P., Case, J.E., Singer, D.A., Bowen, R.W., Berger, B.R., Cox, D.P., Hodges, C.A., Instituto Nacional de Inves- Colciencias for their financial, logistic, and technical support. tigaciones Geológico-Mineras Colombia, U. S. Geol. Surv., 1983. Mapa de ter- Thanks to Andrés Pardo (Universidad de Caldas) for the palyno- renos geológicos de Colombia. Instituto Colombiano de Geología y Minería- logical analysis of most of the samples of the Concentración INGEOMINAS, Bogota, Colombia, p. 235. Fabre, A., 1987. Tectonique et generation d’hydrocarbures; un modele de l’evolution Formation. We specially thank J. Saylor, B. Horton, J. 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