Introduction

The Cenozoic Andean orogeny in the Northern Andes of Colombia (Fig. 1) was preceded by the evolution of Mesozoic extensional basins and magmatism (Sarmiento 2001; Sarmiento-Rojas et al. 2006; Kammer and Sánchez 2006; Mora et al. 2009, 2013; Kammer et al. 2020). Several studies on the northwestern Andes of Colombia have unraveled main traits of their Mesozoic tectono-magmatic evolution (e.g., McCourt et al. 1984; Aspden et al. 1987; Vásquez and Altenberger 2005; Bayona et al. 2006; Vásquez et al. 2010; Cochrane et al. 2014a, b; Bustamante et al. 2016; Rodríguez-García et al. 2020) and showed that the magmatism is related to subduction of the Farallon oceanic plate beneath northwestern South America (Jaillard et al. 1990; Toussaint 1995; Ramos and Aleman 2000; Sarmiento-Rojas et al. 2006; Ramos and Folguera 2009; Pindell and Kennan 2009).

Fig. 1
figure 1

a Main topographic and tectonic features of the Northern Andes. The extent of b is indicated by the orange box. b Regional geological map of the study area after Gómez et al. (2015). Abbreviations are WC (Western Cordillera), CC (Central Cordillera), EC (Eastern Cordillera), CR (Cordillera Real), MA (Merida Andes), SNSM (Sierra Nevada de Santa Marta), LMV (Lower Magdalena Valley), MMV (Middle Magdalena Valley), UMV (Upper Magdalena Valley) for mountain ranges and basins; FM (Floresta Massif), SM (Santander Massif), and SL (San Lucas range) for basement exposures; LC (Los Cobardes anticline), AA (Arcabuco anticline), PA (Portones Anticline), and NM (Nuevo Mundo syncline) for regional folds and LMF (La Morena fault), SMBF (Santa Marta Bucaramanga fault), LSF (La Salina fault), SF (Suarez fault), AF (Aratoca fault), BF (Boyaca fault), SOF (Soapaga fault) for main faults

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Basin development in the northeastern Andes started in the Triassic (Cediel 1968, 2019; Maze 1984; Jaillard et al. 1990; Cooper et al. 1995; Sarmiento 2001, 2011). An extensional setting is documented from the Triassic to the Early Cretaceous by the presence of normal faults (Sarmiento 2001; Sarmiento-Rojas et al. 2006; Branquet et al. 2002; Kammer and Sánchez 2006; Mora et al. 2006). In the Cretaceous, an extensive marine basin was established (Fig. 2). The Triassic-Jurassic plutonism principally comprises calc-alkaline magmas (McCourt et al. 1984; Aspden et al. 1987; Rodríguez-García et al. 2020). At the end of the Jurassic period, plutonism ceased in the Eastern Cordillera and Middle Magdalena Valley (McCourt et al. 1984; Aspden et al. 1987; Bayona et al. 2020) but continued further west. Proposed explanations for the westward retreating magmatism include changes in slab dip or convergence velocity (Cross and Pilger 1982; Jarrard 1986; Metcalf and Smith 1995). According to Bustamante et al. (2016), the steepening of the subduction angle associated with slab rollback or changes in convergence obliquity were the mechanisms that controlled the location of magmatism. Early-middle Cretaceous small mafic intrusive bodies occur further east in the Eastern Cordillera. These gabbroic rocks have alkaline to tholeiitic compositions (Vásquez and Altenberger 2005) interpreted to reflect different degrees and depths of partial melting, with tholeiitic magmas corresponding to the thinnest lithosphere (Vásquez and Altenberger 2005; Vásquez et al. 2010).

Fig. 2
figure 2

Mesozoic stratigraphic chart for the Eastern Cordillera and Middle Magdalena Valley, showing the depositional environments, lithologies, and magmatic activity. Data compiled from Renzoni (1962), (1967), Cediel (1968), Cooper et al. (1995), Clavijo (1996), Mojica et al. (1996), Sarmiento (2001), Sarmiento-Rojas et al. (2006), Kammer and Sánchez (2006), Mora et al. (2006, 2009, 2013), Clavijo et al. (2008), Caballero et al. (2013), Horton et al. (2010, 2015), Moreno et al. (2013), Bayona et al.(2020), Rodríguez-García et al. (2020) and complemented with the new measurements and data obtained in this work. Location of stratigraphic transect in Fig. 1

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During the last decades, geochronological and geochemical information has been collected from several plutonic bodies. However, as Bayona et al. (2020) noted, unconstrained stratigraphic positions and scarcity of the samples have hindered the elaboration of a chronostratigraphic model that integrates plutonism, volcanism, and deposition of sedimentary rocks for specific time slices and tectonic settings. Points that remain incompletely understood include the onset and extent of Mesozoic extension and the basin configuration (Sarmiento 2001; Kammer and Sánchez 2006; Mora et al. 2006, 2009; Horton et al. 2010). Also, Mesozoic extension has been attributed to either intracontinental rifting or back-arc extension (e.g., Maze 1984; Aspden et al. 1987; Cediel et al. 2003; Vásquez and Altenberger 2005; Bayona et al. 2006; Pindell and Kennan 2009; Zapata et al. 2020a).

Our study integrates geochronology, petrography, stratigraphy, and balanced cross sections to illustrate the Mesozoic basin development and the tectonic setting of the initial magmatism. We present new U/Pb ages from the Girón, Jordán, La Rusia, Montebel, and Arcabuco formations in the axial zone of the Eastern Cordillera, and from the Noreán Fm. in the northern part of the Middle Magdalena Valley. We relate these new results to petrography, sedimentary thicknesses, and structural data. We present a conceptual evolutionary model that incorporates recent information on structures, plutonism, volcanism, and sedimentation to constrain the timing of extension events and their relationship with magmatism on the active margin of northwestern South America during the Mesozoic.

Geologic framework

Stratigraphic and tectonic overview

The basement in the Eastern Cordillera is composed of high-to-medium grade metamorphic rocks. The oldest rocks are Mesoproterozoic in age, such as the high-grade Bucaramanga gneiss in the Santander Massif (Restrepo-Pace and Cediel 2010), which is associated with the ~ 1.0 to 1.2 Ga Grenvillian-Orinoquiense tectonothermal event. This was followed by the Paleozoic Caparonensis-Quetame orogenic event (~ 0.47 Ga), which is characterized by middle-grade metamorphism, such as that affecting the metapelites of the Silgará Fm. exposed in the Santander Massif (Restrepo 1995; Restrepo-Pace and Cediel 2019).

Patchily preserved Paleozoic strata in the Eastern Cordillera unconformably overlie the basement. These variable but predominantly siliciclastic sedimentary rocks record marine to nonmarine deposition (Horton et al. 2010). They comprise conglomerates, sandstones and shales of Early Devonian to Carboniferous age. Limestones are intercalated in the Carboniferous succession (Ward et al. 1973). The Paleozoic strata were dated and assigned to environments ranging from deltaic and coastal to epicontinental marine based on brachiopods, plant fossils, and spores (Cardona et al. 2016; Moreno-Sánchez et al. 2020).

Mesozoic strata are exposed throughout the Eastern Cordillera, with significant variations in thickness from hundreds to thousands of meters for some rock units (Table 1). Triassic rocks rest unconformably on Paleozoic rock units or metamorphic basement. Deposition during the Triassic-Jurassic occurred in two basin compartments, the first underlying the Eastern Cordillera with its foreland basins and the western sectors of the Guyana Shield (Cediel et al. 2003; Sarmiento-Rojas et al. 2006), and the second termed Payande-San Lucas-Sierra Nevada (Etayo-Serna 1968) along the NE-trending Central Cordillera. The Triassic-Jurassic stratigraphic sequences have been interpreted by Julivert (1963), Renzoni (1967), Cediel (1968), Clavijo (1996), Mojica and Kammer (1995), Mojica et al. (1996), and Kammer and Sánchez (2006) as predominantly continental deposits (Figs. 2 and 3). Thick successions of conglomerates and sandstones comprise sporadic volcanic effusive and pyroclastic deposits as well as local marine facies such as the Montebel Fm. (Renzoni 1967; Sarmiento 2001). The Triassic continental clastic sequence has been interpreted as an overall regressive cycle (Cooper et al. 1995; Cediel 2019), that evolved from coastal sandstones with intercalated mudstones and siltstones to red sandstones and conglomerates interbedded with tuffaceous sandstones and mudstones (Cediel 1968; Geyer 1969, 1982; Mojica et al. 1996; Clavijo et al. 2008) (Figs. 2 and 3). In the region south of the Sierra Nevada de Santa Marta, the Triassic sandstones of the Bocas Fm. were deposited in a marginal marine environment established by a transgression (Irving 1975). The volcaniclastic and pyroclastic deposits of the latest Triassic to Early-Middle Jurassic (Mojica et al. 1996) accumulated in sub-basins along the continental margin that were created by an asynchronous extension (Mojica and Kammer 1995) (Figs. 1, 2, and 3).

Fig. 3
figure 3

Stratigraphic columns of the formations analyzed in this work. Sources: Noreán and Bocas Fms. from Clavijo (1996); Girón and Jordán formations from Cediel (1968), Palermo, Montebel, La Rusia and Arcabuco Fms. compiled from Renzoni (1967). Locations in Fig. 1

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According to Ward et al. (1973), the Santa Marta-Bucaramanga strike-slip fault (SMBF in Fig. 1) played a fundamental role during the early stages of Mesozoic rifting. This interpretation is based on sub-basins filled by synrift strata in the western block of the Santa Marta-Bucaramanga fault system. Late Triassic-Early Jurassic activity of the Santa Marta-Bucaramanga fault is also inferred from radiometric ages obtained from the granitoids of the Santander Massif which intruded along the strike-slip fault (Cediel et al. 2003; Kammer and Sánchez 2006; Mantilla-Figueroa et al. 2013) (Fig. 4).

Fig. 4
figure 4

Mesozoic magmatic bodies of the Eastern Cordillera and Middle Magdalena Valley after Bayona et al. (2020) and Rodríguez-García et al. (2020). Published age data and locations of our samples are shown. Note the alignment of intrusions along the Bucaramanga-Santa Marta strike-slip fault (SMBF). Abbreviations are SMBF Santa Marta-Bucaramanga fault, LSF La Salina fault, SF Suarez fault, BF Boyacá fault and SOF Soapaga fault

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Initial Jurassic deposition in the study area is characterized by transitional mudstones interbedded with coarser-grained clastic rock units that were mostly deposited in continental environments (Cediel 1968; Mojica et al. 1996; Sarmiento 2001) (Table 1). The coarse-grained deposits are linked to the Jurassic activity of normal faults (Mojica et al. 1996; Sarmiento 2001; Kammer and Sánchez 2006). The presence of marine bivalves and ammonites documents local marine ingressions predominantly during the Early Jurassic (Renzoni 1967; Geyer 1969). Volcaniclastic and pyroclastic deposits were mainly deposited during the Middle Jurassic (Clavijo 1996; Mojica et al. 1996; Sarmiento 2001), see Figs. 2 and 3. Nevertheless, in the Los Cobardes region (Fig. 1) in the center of the study area, such rocks were deposited since the Early Jurassic (Cediel 1968).

The Cretaceous in the Eastern Cordillera is represented by fluvial deposits at the early stages (Table 1), followed by a succession of shallow marine deposits laid down in progressively deepening environments until maximum water depth was reached during the Early Cretaceous (Valanginian) (Mora et al. 2009). Maximum flooding was followed by multiple transgressive–regressive events, interpreted to be in part due to the accretion of the multiple oceanic terranes of the Western Cordillera (see Fig. 2). The accretion of terranes caused uplift, which resulted in regression of the shoreline. Furthermore, this also caused an increase in clastic influx resulting in continental deposition during the Paleocene and part of the Eocene (Sarmiento 2001; Sarmiento-Rojas et al. 2006; Caballero et al. 2013).

The study area was transformed from a back-arc to a retroarc foreland basin in the Late Cretaceous/Paleogene (Horton et al. 2015; Carvajal-Torres et al. 2022). The Cenozoic succession comprises non-marine deposits from alluvial fan to proximal fluvial environments (Cooper et al. 1995; Horton et al. 2010). The Late Paleocene to middle Eocene sequence that unconformably overlies the Late Cretaceous deltaic marine deposits represents the main clastic wedge of fluvial facies derived from the rising Andes in the west (Horton et al. 2010; Carvajal-Torres et al. 2022). Mudstones deposited in a lacustrine environment during the Late Eocene were followed by Oligocene and Quaternary coarse-grained fluvial and alluvial sandstones and conglomerates (Cooper et al. 1995). The absence of Miocene deposits in the Eastern Cordillera is attributed to non-deposition caused by a period of basin inversion and uplift (Horton et al. 2010).

Sampled formations

Samples from the Noreán, Bocas, Girón, Jordán, La Rusia, Montebel, and Arcabuco Fms. were analyzed (Figs. 2 and 3) (Table 1). In its type locality, the Noreán Fm. comprises continental strata with volcanic intercalations. In some areas, the total thickness of this formation exceeds 4500 m as measured, for instance, on the road from Buturama to Bombeadero in the Noreán region (Figs.1 and 3; Clavijo 1996). The samples analyzed derive from the Epiclastic Unit as defined by Clavijo (1996), and are mostly comprised of pink-colored lithic andesite to dacite tuffs with intercalated mud-supported conglomerates. The sequence is well stratified and has a thickness of 1500 m (Fig. 3). Tuffs were macroscopically identified throughout the section.

The type locality of the Bocas Fm. is near the town of Aguachica, while its outcrops studied here are located along the Rio de Oro in the northern part of the study area. This section contains a thick succession of gray sandstones and mudstones with intercalated tuffs and volcanic flows of intermediate composition, with a total thickness of 781 m (Fig. 3; Clavijo 1996). The samples of the Bocas Fm. analyzed in this study come from the andesite lava flows described by Toro-Toro et al. (2021), northwest of the Santander Massif (Fig. 1).

The Girón Fm. has been described and defined by Cediel (1968) in the Lebrija River, where he measured a thickness of 4640 m. It is a continental unit composed of interbedded mudstones and sandy conglomerates with volcaniclastic rocks at the base. Higher up, the sequence presents variations from mudstones to coarse-grained red sandstones, and near the top, the predominant mudstones give way to conglomerates. (Fig. 3). Sampling was conducted around the valley of the Sogamoso River (Fig. 1), and macroscopic analysis was applied to the sandstones and the volcaniclastic layers at the bottom of the stratigraphic section.

The Jordán Fm. was defined and described by Cediel (1968) near the town of Jordán. It essentially consists of coarse-grained sandstones and sparse conglomerates with sporadic intercalations of mudstones, followed by an alternation of red beds. This 420 m thick section has interbedded red tuffs known as the welded tuffs of Jordán (Fig. 3).

The Montebel Fm., which crops out along the eastern flank of the Arcabuco anticline was described by Shell Geologists (in Renzoni 1967) as interbedded black shales and mudstones with the presence of several lenses of red sands, with a total thickness of 400 m (Fig. 3) including some levels of volcaniclastic deposits (App. 1). Overlying this formation along the eastern flank of the Arcabuco anticline, is an intercalation of sandstones and conglomerates with a total thickness of 682 m (Fig. 3) that was defined by Renzoni (1967) as La Rusia Fm. To the south, along the anticline plunge, see Appendix 1, a section composed of interbedded sandstones with thin layers of shale and a thickness of 600 m (Fig. 3) was defined as the Arcabuco Fm. by Renzoni (1967).

Materials and methods

We collected samples from four areas: (1) the Noreán region, which is located in the northern part of the Middle Magdalena Valley, where we collected information from the Noreán and Bocas Fms. and obtained samples from the hanging-wall blocks of the Aguachica and La Morena faults (Fig. 1b); (2) the Los Cobardes region (Fig. 1b), which is located in the central part of the Eastern Cordillera along the Los Cobardes anticline, where we obtained samples from the Girón Fm. and basal Cretaceous rock units. The dated samples come from the footwall block of the Suarez fault; (3) the Jordán region (Fig. 1b), which is located in the Chicamocha canyon to the east of the Los Cobardes region, where we sampled the Jordán Fm. in the hanging-wall block of the Aratoca fault, and finally, (4) the Arcabuco region (Fig. 1b), which is located in the southeastern part of the Eastern Cordillera, where we collected samples from the Arcabuco, Montebel, La Rusia, and Palermo Fms, all from the Arcabuco anticline in the hanging-wall of the Boyacá fault.

Table 1 Mesozoic lithostratigraphic and depositional environments summary for the Eastern Cordillera and Middle Magdalena Valley shown in Fig. 2
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Description and classification of different lithologies were performed through optical microscopical analysis, including the selection of samples for dating. The microscopically determined mineral content was used for the classifications of Streckeisen (1980) and Schmid (1981) for volcanic rocks and volcaniclastic material, respectively. Those analyses were conducted on samples collected from all the Mesozoic rock units present in the four regions.

The in-situ geochronological U/Pb measurements were performed by laser-ablation single-collector sector-field inductively coupled plasma mass spectrometry (LA-SF-ICP-MS) on zircon, conducted in the GÖochron Laboratories, University of Göttingen, following the analysis procedures and protocols of Frei and Gerdes (2009). The data was collected using single spot analysis with a laser beam diameter of 33 µm and a crater depth of approximately 10 µm. The laser was fired at a repetition rate of 5 Hz with a nominal laser energy output of 25%. Two laser pulses were used for pre-ablation. The carrier gases were He and Ar. The ICP-MS measured analytes of 238U, 235U, 232Th, 208Pb, 207Pb, 206Pb, 204Pb, and 202Hg. The data reduction was based on the processing of ca. 50 selected time slices (corresponding to ca. 14 s) starting ca. 3 s after the beginning of the signal. If the ablation hit zones or inclusions with highly variable actinide concentrations or isotope ratios, then the integration interval was slightly resized, or the analysis was discarded (~ 1% of the spots). The individual time slices were tested for possible outliers by an iterative Grubbs test (applied at P = 5% level). This test filtered out only the extremely biased time slices, and in this way, less than 2% of the time slices were rejected. The age calculation and quality control are based on the drift- and fractionation correction by standard-sample bracketing using GJ-1 zircon reference material (Jackson et al. 2004). For further control, the Plešovice zircon (Sláma et al. 2008) and 91,500 zircons (Wiedenbeck et al. 1995) were analyzed as "secondary standards". The age results of the standards were consistently within 2σ of the published ID-TIMS values. Drift- and fractionation corrections and data reductions were performed by in-house software UranOS (Dunkl et al. 2008). The level of Hg-corrected 204Pb signal was deficient; thus, no typical lead correction was required. The age spectra, concordia, and histogram plots were constructed with the help of Isoplot/Ex 3.75 (Ludwig 2012) age measurements, and analytical results are attached in the supplementary material.

Based on previous geological mapping, and stratigraphic and structural measurements, we constructed a set of new balanced cross sections in order to show the present-day structural setting of our sampling locations. The sections are partially restored in order to illustrate the role of extension throughout the study area. A Mesozoic stratigraphic chart was constructed by employing data from boreholes kindly provided by the National Hydrocarbons Agency (ANH) and previously published studies from the Middle Magdalena Valley to the Eastern Cordillera (referenced in the caption to Fig. 2). The chronostratigraphic framework is based on geochronological data and biostratigraphic information obtained during the last decades in the region to calibrate the regional-scale correlations.

Results

Petrography of pyroclastic and volcaniclastic samples

Microscopic analyses were performed on samples from volcaniclastic lithologies identified as potential targets for age dating. The tuffs present mainly porphyritic texture, and the most frequent phenocrysts/clasts are of quartz and plagioclase feldspar, with a smaller fraction of lithics, glass, and mafic minerals. Two different types of tuff are present: (1) rhyolitic, with a high percentage of quartz, and (2) andesitic, with a high content of plagioclase feldspar.

Sample NR-021 from the Noreán Fm. presents a porphyritic texture, with phenocrysts mainly of plagioclase (80%), quartz (15%), and accessories (5%). A compound of muscovite, lithics, zircon, and devitrified glass constitutes the matrix (20–40% of the total rock). This sample is interpreted as lithic andesite ash (Fig. 5a). Samples NR-011 and NR-012 contain phenocrysts of quartz (90–95%) and plagioclase or accessories (5%). The matrix is composed of quartz, devitrified glass, and feldspar. According to the mineral proportions, this was classified as lithic rhyolite ash (Fig. 5b).

Fig. 5
figure 5

Characteristic microscopic features of the samples studied: a Resorbed quartz grain as evidence of volcanic origin. Noreán Fm. b porphyritic texture, large population of angular quartz grains. Noreán Fm. c porphyritic texture, plagioclase as principal component, mafic minerals. Bocas Fm. d porphyritic texture with pumice fragments. Jordán Fm

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Samples NR-333 and NR-322 from the Bocas Fm. display a high percentage of plagioclase phenocrysts (85–90%). Accessory phenocryst minerals or clasts are quartz (2–5%), lithics (5–10%), and mafic minerals (2–8%). The matrix is composed of quartz, feldspar, pumice, and chlorite, permitting a classification as lithic andesite ash (Fig. 5c).

Samples JR-412 and JR-432 from the Jordán Fm. are composed of pumice clasts (60–40%), quartz (30–10%) and plagioclase (10–5%), phenocrysts lithics (5–15%) and muscovite (2–5%). The matrix is composed of pumice, quartz, devitrified glass, and feldspar and represents 20–40% of the total rock. This sample is classified as lithic rhyolite ash (Fig. 5d).

Zircon populations

A total of 305 zircon crystals from 10 samples from the different sections were analyzed using a binocular lens and cathodoluminescence images to distinguish different populations and correlate them with petrogenetic indicators. To characterize the crystal morphology, we employed the Pupin (1980) classification for shape variations (Fig. 6a). This classification uses a combination of prisms and pyramids to describe crystal shapes. Specific shapes are represented by different letters i.e., S, P, R, and others. In all our samples, the largest population of crystals is P2.

Fig. 6
figure 6

Zircon morphology classification after Pupin (1980) with the main crystal families found in the analyzed samples. Cathodoluminescence images of zircon showing grains from b the Noreán Fm., c the Jordán Fm. and d the Arcabuco Fm. Blue spots are the ablated regions

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Three samples from the Noreán Formation have been analyzed and show different zircon populations. The predominant color is light brown; nevertheless, gray, colorless, and yellowish crystals are also present. Magmatic zoning is common in samples NR-012 and NR-021, where the zircons show a better selection and where the major population of zircons are classified as P2 crystals, representing more than 90% of the total amount of crystals in this sample (Fig. 6b), whereas Sample NR-011 contains a poor selection of crystals with different type of crystal such as S4, S9, S10, S19, P1, P2, and R2. Inclusions are present mainly in crystals with rounded edges (Fig. 6b).

Samples from the Jordán Formation primarily display a crystal population that is colorless to light brown. Sample JR-431 (Fig. 6c) reflects an excellent selection of crystals, with the majority consisting of P1 and P2. The crystals have well-preserved edges, and show clear evidence of magmatic zoning.

The detrital sample AR-222, from the Arcabuco Formation, presents different shapes, from oval to rounded crystals. Most of the zircons are not well preserved. They show significant variation in size from 50 to 200 microns (Fig. 6d) and variable crystal types P2, P3, S5, S10, and S19. A significant amount of the total crystals (80%) analyzed in this sample present inclusions, and magmatic zoning is scarce.

U/Pb geochronology

We dated more than 300 zircon grains from 10 samples using the U/Pb technique; see raw data in Appendix 2. Sampling locations are shown in Fig. 1, general stratigraphic positions in the chronostratigraphic chart (Fig. 2), and detailed stratigraphic positions within the sampled formations in Fig. 3.

The samples were mainly volcaniclastic and tuff layers from the Mesozoic rock units. Still, a significant percentage of those samples show a polymodal age distribution, and just two samples have unimodal distributions. The zircon ages obtained in this work are distributed in 14 subgroups. The oldest ages are Mesoproterozoic (ca. 1.54–1.01 Ga) and Neoproterozoic (ca. 995–562 Ma), while only three Paleoproterozoic ages (ca. 1.72–1.62 Ga) were identified. The most represented age groups are Lower to Middle Ordovician (ca. 478–458 Ma), Upper Triassic (ca. 209–201 Ma), and Lower Jurassic (ca. 200–175 Ma). Other smaller age subgroups are Cambrian (ca. 499–485 Ma), Upper Ordovician (ca. 457–445 Ma), Silurian (ca. 440–437 Ma), Devonian (ca. 405–373 Ma), Carboniferous with two ages (ca. 345–314 Ma) obtained from the samples AR-222 and NR-012; Permian (ca. 278–256 Ma), Lower Triassic (ca. 249–247 Ma), and Middle Jurassic ages (ca. 173–167 Ma).

We dated the samples NR-011, NR-012, and NR-021 from the Noreán Formation. In sample NR-011, classified as lithic rhyolite ash, 27 ages were obtained ranging from 175 to 1550 Ma (Fig. 7a), displaying a multimodal distribution with a principal population of Early Jurassic ages. A concordia age of 177.6 ± 1.6 Ma (Toarcian) with a MSWD (Mean Squared Weighted Deviation) of 2.1 (Fig. 7b) was calculated from a subgroup of 5 grains with Mesozoic ages. For sample NR-012, described as lithic rhyolite ash, a total of 25 ages were analyzed with values between 176 to 1620 Ma (Fig. 7c). The distribution within this range is multimodal with a significant peak in the Early Jurassic. A concordia age of 178.8 ± 1.2 Ma (Toarcian) and a MSWD of 1.03 was obtained from 10 zircons with Mesozoic ages (Fig. 7d). Both samples contain Precambrian and Paleozoic inherited zircons. Mesozoic grains represent ~ 60% of the total grain population of samples NR-011 and NR-012. The Triassic ages range from 247 to 201 Ma, though only one grain with a Lower Triassic age was found in sample NR-011. For sample NR-021, classified as lithic andesite ash, which contains no inherited zircons (Fig. 7e), a narrow unimodal distribution was obtained from 26 concordant ages giving a Toarcian concordia age of 176.85 ± 0.63 Ma with a MSWD of 0.075 and with ~ 70% of grains in the 180–174 Ma age range (Fig. 7f).

Fig. 7
figure 7

Histogram and Wetherill concordia plots of zircon U–Pb results drawn using ISOPLOT (Ludwig 2012). a Histogram plot of the Noreán Fm. b detailed concordia plot of the black square in a for the Mesozoic ages of Noreán Fm. c histogram plot of the Noreán Fm. d detailed concordia plot for the black box in c Noreán Fm. e histogram plot of the Noreán Fm. f detailed concordia plot of the black square of e. Noreán Fm

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Regarding the Girón Formation, we dated samples LC-031 and LC-032. Sample LC-031, classified as volcaniclastic sandstone, yielded a total of 26 ages that vary from 200 to 1600 Ma (Fig. 8a). The distribution of the ages is multimodal, with two maxima at 200 Ma and 460 Ma. The most representative group contains Mesozoic ages, mainly Late Triassic, with a concordia age of 200.8 ± 1 Ma (Hettangian) and a MSWD = 0.058 (Fig. 8b) calculated from a subgroup of 6 grains. For the volcaniclastic sandstone sample LC-032, 14 grains were analyzed, with ages between 190 and 1500 Ma (Fig. 8c). The distribution is multimodal with a significant population of Early Jurassic ages. A concordia age of 199.5 ± 1.8 Ma (Hettangian) with a (MSWD = 1.15) was obtained from a subgroup of 4 grains with Mesozoic ages (Fig. 8d).

Fig. 8
figure 8

Histogram and Wetherill concordia plots of zircon U–Pb results drawn using ISOPLOT (Ludwig 2012). a, c Histogram plots for samples LC 031 and LC 032 from the Girón Fm. b, d detailed concordia plots of Mesozoic ages inside the black squares of a and c. e, g histogram plots for samples JR 431 and JR 451 from the Jordán Fm. f, h detailed concordia plots of the black squares in e and g, respectively

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Samples JR-431 and JR-531 from the Jordán Formation have been dated as part of this study. Sample JR-431 classified as lithic rhyolite ash contains long prismatic zircons that were analyzed, and 23 concordant ages were obtained with values between 190 and 205 Ma (Fig. 8e), generating a unimodal distribution with a concordia age of 195.7 ± 1.3 Ma (Sinemurian) and a (MSWD = 0.69) with ~ 60% of grains between 198 to 192 Ma (Fig. 8f). Sample JR-531 described as lithic rhyolite ash includes 33 concordant ages in a range from 185 to 1400 Ma (Fig. 8g). The distribution is multimodal with a major population of Precambrian ages with a predominance of ages between 1.6 and 1.0 Ga. Nevertheless, Mesozoic zircon grains are also present from which a concordia age of 187.3 ± 2.5 Ma (Pliensbachian) was calculated on a subgroup of 3 grains. An MSWD of 1.0 was obtained (Fig. 8h). This sample has both Precambrian and Paleozoic grains.

From the Montebel Formation, a total of 50 ages were analyzed from the red sandstones associated with sample AR-351. The ages range between 440 and 1750 Ma (Fig. 9a), which yielded a multimodal distribution with a significant peak of Ordovician ages. The concordia age is 471.4 ± 2.0 Ma (Florian) obtained from a subgroup of 18 grains with Ordovician ages (Fig. 9b). All ages are associated with inherited zircons.

Fig. 9
figure 9

Histogram and Wetherill concordia plots of zircon U–Pb results drawn using ISOPLOT (Ludwig 2012). a Histogram plot of sample AR 351 from the Montebel Fm. b detailed concordia plot of ages inside the black square in a. c Histogram plot of sample AR 222 from the Arcabuco Fm. d Detailed concordia plot of ages inside the black square in c. e Histogram plot of sample AR 451 from the La Rusia Fm. f Detailed concordia plot of ages inside the black square of e

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From the Arcabuco Formation, we obtained 50 ages ranging from 370 to 1500 Ma (Fig. 9c) from quartz sandstone sample AR-222. The zircons have a multimodal distribution showing a significant peak of Ordovician ages. The concordia age for this range is 466.0 ± 4.0 Ma (Darriwilian) (Fig. 9d) obtained from 12 grains with Ordovician values. All ages obtained are related to inherited zircons.

From the volcaniclastic sandstones of La Rusia Formation, 30 zircons from the sample AR-451, were obtained and dated. Ages are in a range of 450–1500 Ma (Fig. 9e), with a multimodal distribution. A significant population of Ordovician values with 9 grains gives a concordia age of 466.2 ± 4.0 Ma (Darriwilian) (Fig. 9f). All ages obtained are related to inherited zircons.

Structural cross sections

We illustrate the structural setting of the sampled formations in four cross sections constrained by outcrop and subsurface data. The cross sections were constructed using the software MOVE (PETEX). The method employed for horizon construction was kink band extrapolation (Suppe 1983) due to its simplicity, and the parallel folding style observed in the field. For restoration, we employed the fault parallel flow (Egan et al. 1997), and flexural slip unfolding (Williams et al. 1997) algorithms. The cross sections are described from north to south.

Noreán region

In the northeastern sector of the Middle Magdalena Valley basin, near the northern tip of the Eastern Cordillera, the topographic range front coincides with the Aguachica thrust (Figs. 1 and 10). In this region, the NW–SE striking Aguachica thrust also forms the deformation front separating the western foothills of the Eastern Cordillera from the Middle Magdalena Valley basin. It is considered to be a basement-involved or thick-skinned structure. The present-day configuration of the cross section (Fig. 10a) shows an open syncline in the footwall of the Aguachica thrust, and a syncline-anticline pair in its hanging-wall dissected by two smaller thrust faults including the La Morena fault.

Fig. 10
figure 10

Balanced cross section of the Noreán region in the northern part of the study area, extending from the Middle Magdalena Valley to the hanging wall of the La Morena fault. Location in Fig. 1. Sample locations illustrated by yellow and red pentagons. a Present-day configuration. b Cross section restored to Late Cretaceous situation

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The kinematic restoration of this cross section to the end of the rifting phase before shortening (Fig. 10b), is not well constrained because Cenozoic and Cretaceous strata have been completely eroded from the hanging-wall in the foothills. The western part of the cross section in the Middle Magdalena basin has a relatively thin Cenozoic sedimentary sequence of less than 1100 m. We infer that the eroded Cenozoic thickness was similar to or greater than the total thickness present in the foreland. In our structural section we interpret the Aguachica fault as the main inverted normal fault during orogenesis in this region, in view of the large thickness of preserved Jurassic and Triassic successions.

Los Cobardes region

Located in the central part of the study area, this cross-sectional traverses, from northwest to southeast, the Lisama buried anticline, the Nuevo Mundo syncline, and the Los Cobardes anticline (Figs. 1 and 11). The present-day structure (Fig. 11a) shows the east-dipping La Salina thrust forming the western deformation front of the Eastern Cordillera. In its footwall, two minor thin-skinned thrusts with associated hanging-wall anticlines are present (Caballero et al. 2013; Moreno et al. 2013).

Fig. 11
figure 11

Balanced cross section of the Los Cobardes region in the central part of the study area. Location in Fig. 1. Section extends from the Middle Magdalena Valley to the footwall of the Suarez fault in the Eastern Cordillera across the Nuevo Mundo syncline and Los Cobardes anticline. Sample location shown by orange polygon. a Present-day configuration. b Cross section restored to Late Cretaceous situation

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The Los Cobardes anticline is an inversion anticline in the hanging-wall of the Suarez fault. In this sector, the Cenozoic strata are much thicker than in the Noreán region. The thickness of Cenozoic rock units preserved in the Middle Magdalena basin is ~ 5500 m. The maximum Mesozoic thickness along the cross- section has been observed in the hanging-wall of the Suarez fault (> 3 km), which contrasts with the thinner sequence in the footwall of the same fault. That documents a very likely fault-controlled creation of accommodation space. The principal structures that control the deformation are thick-skinned structures including the west-verging La Salina, and the east-verging Suarez fault, interpreted as Mesozoic normal faults inverted during the Andean Cenozoic orogeny (Cooper et al. 1995; Sarmiento 2001, 2011; Kammer and Sánchez 2006; Sarmiento-Rojas et al. 2006). This is illustrated in the kinematic restoration of our cross section to a pre-inversion configuration (Fig. 11b).

Jordán Region

The Jordán region is located in the core of the Eastern Cordillera (Fig. 1b), ~ 20 km south of the previously described Los Cobardes region. The cross section is located from the eastern side of the Los Cobardes anticline bounded by the Suarez fault and extends to the boundary of the Santander Massif. The main structure in this cross section is the basement-involved Suarez fault.

The present-day configuration (Fig. 12a) shows the gently folded Los Cobardes basement block uplifted by the Suarez fault. The footwall of the Suarez fault is deformed into a synclinorium exhibiting numerous short-wavelength folds. Within this structural domain, we document a small Jurassic graben whose boundaries are non-reactivated normal faults. In this context, Jurassic strata terminate against the eastern Aratoca fault (Julivert 1963). In this region, the Cenozoic strata are eroded, and according to Tesón et al. (2013), in the northern segment of the Eastern Cordillera, the exhumation is less than 7 km based on estimates of potentially removed amounts of overburden. The maximum thickness of Mesozoic units was accommodated in the hanging-wall of the Suarez fault during its normal motion in the extension phase (Fig. 12b).

Fig. 12
figure 12

Balanced cross section along the Chicamocha canyon in the Jordán region, central part of the study area. Location in Fig. 1. Section extends from the hanging-wall of the Suarez fault in the Eastern Cordillera to the footwall of the Aratoca fault. Sample location indicated by orange and red pentagons. a Present-day configuration. The Jordán Fm. is interpreted to be bounded by the Aratoca fault and an antithetic normal fault. b Cross section restored to end-Late Cretaceous situation

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Arcabuco region

The southernmost cross section analyzed in this work is located in the central-eastern region of the Eastern Cordillera. It crosses the Arcabuco anticline, and Floresta massif (or antiform) of the Eastern Cordillera axial zone from east to west (Figs. 1 and 13). These folds are basement-involved structures strongly controlled by the Mesozoic extensional faults in their present configuration (Kammer and Sánchez 2006; Tesón et al. 2013). The main structures that controlled the evolution of the two anticlines are the Boyacá, and Soapaga faults (Kammer and Sánchez 2006) (Fig. 13a). The west-dipping Boyacá and Soapaga faults strike NE-SW and have been interpreted as reactivated Mesozoic normal faults with dextral strike-slip components conjugate to the Santa Marta-Bucaramanga fault (Kammer 1999; Kammer and Sánchez 2006; Kammer et al. 2020).

Fig. 13
figure 13

Balanced cross section of the Arcabuco region in the southern part of the study area. Location in Fig. 1. Section extends across the Arcabuco anticline bounded by the Boyacá fault and the Floresta anticline bounded by the Soapaga fault. Sample location is shown by orange polygon. a Present-day configuration. b Cross section restored to end-Late Cretaceous situation

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The Arcabuco anticline is a first-order, large-wavelength gentle fold controlled by the Boyacá fault. A narrow graben containing Jurassic strata occurs on the eastern flank of the Floresta anticline, bounded by the Soapaga fault, and a non-reactivated east-dipping antithetic normal fault. The preserved Cenozoic strata in the Floresta region can reach ~ 2200 m, including the Middle Eocene. According to thickness estimates, the stratigraphic throw on the Boyacá fault is ~ 4000 m (Tesón et al. 2013) (Fig. 13a). To the hanging-wall of the Boyacá fault, where the depocenter is situated, the basin underwent a lower Mesozoic thickening (Fig. 13b).

Discussion

Our new data provide improved temporal constraints on the Late Triassic to Early Cretaceous basin development in the northern Andes. We discuss the new geochronological data in chronological order and relate them to structural kinematics, stratigraphic thicknesses, facies variations, petrology and geochemistry of plutonism, and geochronological data from plutons and Mesozoic rock units.

Zircon provenance

Potential source regions of detrital grains

Precambrian ages in our new samples most probably come from the western part of the northern Amazon craton (Guyana Shield) where they correlate to the principal Proterozoic events (Ibanez-Mejia et al. 2011; Kroonenberg 2019). The Cambrian zircon ages can be related to a regional metamorphic event that occurred in the Santander Massif, whereas the Ordovician grain ages coincide with arc magmatism and metamorphism related to the Caparonesis-Famatinian Orogeny (Restrepo-Pace and Cediel 2010; van der Lelij et al. 2016; Moreno-Sánchez et al. 2020). Ordovician grains in the easternmost samples from the axial Eastern Cordillera have potential sources in the Floresta, and Santander Massifs (van der Lelij et al. 2016). Other Paleozoic grains give Silurian and Devonian ages. The Devonian grain population is less prominent than a Devonian age component interpreted as detrital zircons in samples from the Santander Massif (Cardona et al. 2016). These Devonian zircons suggest magmatic activity during the Devonian (Pastor-Chacón et al. 2023) however, its location is unknown. Late Paleozoic, Carboniferous to Permian zircons are present in minor proportion. Such ages were found in plutons of the San Lucas Massif, the Sierra Nevada de Santa Marta, and the Perijá range (Rodríguez-García et al. 2020).

Mesozoic grains are distributed in four populations: (1) Lower Triassic, (2) Upper Triassic, (3) Lower Jurassic and (4) Middle Jurassic, with fewer zircon grains of Early Triassic and Middle Jurassic ages. Early Triassic ages are only present in two samples Upper Triassic and Lower Jurassic grain populations are abundant in the majority of the samples dated in this work. These zircons are interpreted to be derived from the Late Triassic-Early Jurassic arc magmatism of the northern Andes, which started at this time in the Santander Massif (Spikings et al. 2015; van der Lelij et al. 2016; Rodríguez-García et al. 2020). Middle Jurassic grains in one sample from the northern part of the Middle Magdalena Valley are also interpreted to come from a magmatic arc, their age range being similar to ages obtained in the San Lucas Massif (Rodríguez-García et al. 2020).

Age patterns

Our samples fall into three groups according to their zircon age patterns: The first group has unimodal age distributions with mean ages matching the interpreted stratigraphic range of the Mesozoic rocks they come from. The second group has polymodal age distributions indicating admixture of older zircon grains, but still youngest zircons of Mesozoic age. The third group has exclusively pre-Mesozoic zircons.

Unimodal samples

Only two of ten samples have (nearly) unimodal age distributions. One age of ~ 177 Ma from the Noreán region, and a second age of ~ 196 Ma from the Los Cobardes region were obtained from volcanic tuffs with rhyolite and andesite composition. They match plutonic ages of the San Lucas and Santander massifs, respectively. We interpret our unimodal ages to date the stratigraphic age of the sampled rocks, shifting the onset of extensional basin formation to the Early instead of Middle Jurassic (Horton et al. 2010, 2015). They overlap with the age range of a dominant Jurassic peak in the detrital zircon age patterns from subsurface samples of the Girón Fm. (Horton et al. 2015). The authors proposed that the near-unimodal patterns reflect a drainage system that fed the Middle Magdalena Valley from the San Lucas range and Santander Massif. Our new ages suggest that local magmatic sources could have made a substantial contribution.

Polymodal samples with Mesozoic zircons

Samples LC-031 and LC-032 from the Girón Fm. have their major grain density in an age peak of 185–209 Ma. Mesozoic zircon grains in both samples represent the largest percentage of the total grain population. The oldest Mesozoic age of 209.4 ± 3.6 Ma was identified in sample LC-032, and the youngest age of 189 ± 6.1 Ma in sample LC-031. In the two samples from the Jordán Fm., the oldest Mesozoic age of 205.7 ± 3.1 Ma was found in sample JR-431 and coincides with the age range obtained in sample LC-032, and this value is also interpreted as related to the initial extension event in the Eastern Cordillera. The youngest age of 186.5 ± 4.9 Ma was found in sample JR-531 and may be coeval with the end of the volcanic activity in the surroundings of the Santander Massif. Both samples were taken from the hanging-wall of the Aratoca fault (see Fig. 1 for location).

As with the unimodal samples, the Triassic-Jurassic zircon age peaks overlap with the ages of plutons. The oldest ages can be associated with the Upper Triassic granitoid bodies of the Santander Massif (González et al. 2015; van der Lelij et al. 2016; Arango et al. 2020; Correa-Martínez et al. 2020a, b; Mantilla-Figueroa et al. 2013; Rodríguez et al. 2020a, b, c; Rodríguez-García et al. 2020;), the younger ones to its Jurassic plutons (González et al. 2015; Zapata et al. 2020a; Arango et al. 2020; Rodríguez-García et al. 2020). Lower Jurassic (Toarcian) ages are frequent in the Noreán Fm. and correlate with plutonic ages from the Santa Marta Massif and the San Lucas Massif (González et al. 2015; Correa-Martínez et al. 2020a, b; Rodríguez-García et al. 2020) (see Fig. 4 for location). Middle Jurassic ages are only present in sample NR-021 and coincide with the youngest ages obtained in the Santander Massif (Paul et al. 2018).

Polymodal samples without Mesozoic zircons

Two sandstone samples from the Montebel and Arcabuco Fms. (AR-351, AR-222) and the volcaniclastic sample from the La Rusia Fm. (AR-451), all collected from the Arcabuco anticline, show polymodal distributions of U/Pb zircon ages with different pre-Mesozoic age peaks from Precambrian to Carboniferous. The youngest age identified in this region is 345.2 ± 5.5 Ma (Carboniferous) from a single zircon grain in sample AR-222. The main zircon grain population ranges between 499–446 Ma (Ordovician), and represents ~ 45% of the total ages.

The La Rusia, Montebel, and Arcabuco Fms. from which the volcaniclastic and detrital samples in the Arcabuco anticline were taken (Fig. 13) are Jurassic in age according to fossils and their stratigraphic relations (Fig. 2) (Renzoni 1967). However, our new samples yielded predominantly Lower to Middle Ordovician and no Mesozoic zircon ages. This distinguishes them from all other samples. The Floresta Massif in the axial zone of the Eastern Cordillera that exposes Paleozoic rocks of a Late Cambrian-Ordovician magmatic belt unconformably below Mesozoic units (Horton et al. 2010; van der Lelij et al. 2016; Leal-Mejía et al. 2019) is the nearest source for Ordovician magmatic zircons for the Mesozoic magmatism in the region of the Arcabuco anticline. We interpret the Floresta Massif as a rift shoulder and dominant proximal source area for the Mesozoic units in the Arcabuco region. Similar Ordovician ages appear in almost all our samples but are mixed there with varying proportions of other Mesozoic and Paleozoic zircons.

Paleoproterozoic and Mesoproterozoic age peaks correspond to the ages of the Amazon craton. One main Precambrian peak in many samples is ~ 1.2 to 1.0 Ga, which is related to the Guyana shield (Restrepo-Pace and Cediel 2010). Other, smaller Mesoproterozoic age peaks are also interpreted as deriving from the western side of the Amazon craton based on the basement and metamorphic ages there (Horton et al. 2010; Kroonenberg 2019; Ibañez-Mejia and Cordani 2020). We caution that Precambrian signals could be related to second-cycle detritus from the Paleozoic rocks in the Floresta and Santander massifs. Neoproterozoic ages in our samples range from 600 to 985 Ma, where older ages coincide with basement ages obtained in the San Lucas range (Cuadros et al. 2014) and the Santa Marta Massif (Piraquive et al. 2022).

Basin configuration and sediment sources

The mixture of Precambrian, Paleozoic and Mesozoic ages in most of our samples suggests two source types (cf. Horton et al. 2010). The proximal Mesozoic and Paleozoic sources probably correspond to coeval local volcanism or erosion from the footwalls of nearby normal faults, while the Precambrian ages suggest more distal sources, either from the Amazon craton in the east or the San Lucas Range to the west (see Figs. 1 and 4 for location). The proximal sources, indicating local relief and volcanic activity, suggest coeval active tectonics. This agrees with the volcano-sedimentary texture and low textural maturity of the detrital component in our samples as documented by petrographic analysis. Also, the conglomeratic facies of the Girón Formation in the footwall of the inverted Suárez fault to the west (Fig. 11) suggests short-distance sediment transport from topographic highs to the east. We hypothesize that this relief was generated by Mesozoic activity of the Bucaramanga fault (see the location of sample LC-031 relative to the Bucaramanga fault in Figs. 1 and 4) and accompanying smaller normal faults (e.g. the Aratoca fault, Fig. 12). The contribution of the proximal, fault-related sources is variable. For instance, Precambrian to Paleozoic zircons from distal, in part cratonic sources predominate in sample JR-531, whereas sample JR-431 has ~ 60% of grains aged 198 to 192 Ma. A low proportion of locally derived material could be due to subdued topography in the initial rifting phases with lesser influence of local sources. Alternatively, it could reflect a sample location away from the main drainage systems that eroded local source areas in fault footwalls.

Stratigraphic correlation of the Girón and Jordán formations

The Girón Fm. is thought to overlie the Jordán Fm. However, sample LC-031 from near the base of the Girón Fm. with an age of about 201 Ma is markedly older than both samples from the Jordán Fm. (Figs. 1, 2, 3 and 8). Possible explanations for the older ages obtained from the Girón Fm. include: (1) Sample LC-031 dated in this work comes from a volcaniclastic deposit that reworked older volcanic material. This interpretation is consistent with the absence of glass and increased quartz content of the Girón Fm. sample, in contrast with the welded tuffs that contain glass matrix and have a typical pyroclastic texture. (2) A time-transgressive base of the Girón Fm., making the Jordán Fm. a lateral equivalent of higher parts of the Girón Fm. in other locations. The most likely explanation for the presence of abundant Precambrian zircons in sample JR-531 is minor footwall uplift associated with the Aratoca fault which, however, was enough to isolate the hanging wall block from the larger catchments draining the Bucaramanga fault.

Tectonic setting and timing of extension

The Eastern Cordillera of the northern Andes has long been recognized as a Mesozoic rift basin inverted during the Cenozoic (Cooper et al. 1995; Sarmiento 2001; Sarmiento-Rojas et al. 2006; Mora et al. 2006, 2009). Two tectonic models have been proposed for the Mesozoic basin evolution of the northwestern Andes in Colombia: (1) an intracontinental rift, supported by paleogeographic reconstructions based on structural and stratigraphic data (Cediel et al. 2003; Pindell and Kennan 2009) or (2) a subduction-related extensional back-arc, supported by geochemical and petrographic analysis (Maze 1984; Aspden et al. 1987; Toussaint 1995; Bayona et al. 2006; Villagómez et al. 2011; Cochrane et al. 2014b; Bustamante et al. 2016; Zapata et al. 2020a). We begin with a brief review of the known magmatic (mostly plutonic) history.

The main Late Triassic plutonic bodies occur in the Santander Massif. They are associated with the NNW-striking Santa Marta Bucaramanga fault. Plutonism in the Eastern Cordillera and Middle Magdalena Valley peaked during the Early Jurassic (Sinemurian-Pliensbachian) times according to the U/Pb ages from the diverse Early Jurassic magmatic bodies (González et al. 2015; Zapata et al. 2020a, b; Arango et al. 2020; Rodríguez et al. 2020c). Most of the Early Jurassic plutons are still aligned with the Santa Marta-Bucaramanga strike-slip fault but large plutons are also present on the western side of the Middle Magdalena Valley. Magma generation thus seems to have increased considerably from the Late Triassic to the Early Jurassic. In general, the plutons are predominantly I-type with some transitional and S-type granitoids (González et al. 2015; Zapata et al. 2020a; Arango et al. 2020; Rodríguez et al. 2020c), indicating a magmatic arc with an important contribution of continental crust (Rodríguez et al. 2020c). Arc magmatism is interpreted to result from the subduction of the Farallon plate beneath the South American plate (Pindell and Kennan 2009). During the Middle Jurassic to Late Jurassic, plutonism declined considerably in the Eastern Cordillera and Middle Magdalena Valley basin. However, intermediate to acid plutonic bodies still occur in the south of the Sierra Nevada de Santa Marta and San Lucas range (Rodríguez-García et al. 2020), and in the Central Cordillera (Vesga and Barrero 1978; González et al. 2015; Bustamante et al. 2016). Plutonism further decreased and came to an end during the Early Cretaceous. This has been interpreted by Bustamante et al. (2016) to be a consequence of highly oblique convergence with slow subduction, reducing the input of subducted sediment and mélange inferred to be one magma source on the basis of radiogenic isotope compositions (Fig. 14). Alternatively, the low magma production from the Middle Jurassic to Early Cretaceous could be attributed to an episode of flat subduction following the foundering of a thickened, eclogitisized arc root (DeCelles et al. 2009).

Fig. 14
figure 14

Tectonic evolution model for the Late Triassic to Late Cretaceous in the Northern Andes of Colombia, illustrating the migration of the magmatic arc and evolution of depositional environments in the Eastern Cordillera. Terrestrial sediments are shown in yellow, marine in blue. Cross sections are not drawn to scale. Vertical dashed lines are basin boundaries. Abbreviations are CC Central Cordillera, MMV Middle Magdalena Valley, EC Eastern Cordillera and LLAB Llanos basin

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A few small Cretaceous mafic plutons with an average exposed area of ~ 60 km2 per body and K–Ar ages ranging from ca. 130 to 113 Ma are present in the Eastern Cordillera (Vásquez and Altenberger 2005; Vásquez et al. 2010). From west to east, their composition changes from tholeiitic to alkaline. In conjunction with other geochemical signatures, this has been interpreted as an eastward decreasing influence of subduction-related metasomatized mantle and increasing depth of melting in a rift setting (Vásquez and Altenberger 2005). By contrast, the Las Brisas extrusive unit on the northwestern side of the Middle Magdalena Valley (Mantilla et al. 2006) comprises porphyritic rocks of andesitic composition that gave an Early Cretaceous (Albian) K–Ar age of 107 ± 4 Ma (Fig. 4). These rocks indicate late Early Cretaceous arc magmatism in the west (Fig. 14). According to the subsidence analysis of Sarmiento (2001), this region of the Eastern Cordillera experienced pulsed lithospheric stretching until the Early Cretaceous (Hauterivian). In the southeastern part of the Eastern Cordillera, Mora et al. (2006, 2009) also suggest an Early Cretaceous (Berriasian to Barremian) age of rifting based on stratigraphic and structural relationships. Interestingly, there is no evidence of older rift events in this area (e.g., Mora et al. 2013) (Figs. 14 and 15).

Fig. 15
figure 15

Non-palinspastic paleostructural maps of the Eastern Cordillera and Middle Magdalena Valley, illustrating the evolution of the main extensional faults during the Mesozoic. Abbreviations are LSF La Salina fault, SF Suarez fault, BF Boyacá fault, PPF Paya-Pajarito fault. The normal faults are interpreted as being kinematically linked to the Santa Marta Bucaramanga strike-slip fault (SMBF) which also provided a pathway for the ascent of granitoid magmas. Light blue hexagons indicate the samples dated in this work. Inactive faults are shown as unornamented gray lines in each time slice

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Our new ages show that volcanism was synchronous with Late Triassic and Early Jurassic plutonism in the study area. Based on the presence of locally derived detritus (Horton et al. 2010, 2015) and terrestrial red bed facies with thick conglomerates and rapid thickness variations, we interpret that extension in the Eastern Cordillera basin of the northern Andes already started during the latest Triassic. In detail, the timing of volcanism as constrained by our zircon ages differs between the Girón, Jordán and Noreán formations. Volcanism in the Girón Fm. lasted from about 201 to 199 Ma, immediately followed by its onset in the Jordán Fm. at around 196 Ma. There, it continues to at least 187 Ma. Volcanism in the Noreán Fm. may be younger altogether, beginning no later than 179 Ma and lasting at least until 175 Ma.

The structural analysis and new ages presented in this paper, combined with those from previous studies, illustrate the changing locations of deformation and magmatism during the Mesozoic (Fig. 15): In the Late Triassic (Rhaetian), a rift started to form in the northern part of the Eastern Cordillera basin. During the Jurassic, rifting apparently migrated westward along with magmatic activity, most likely driven by roll-back of the subducting plate to the west. By contrast, Early Cretaceous rifting is mainly localized in the eastern parts of the Eastern Cordillera (e.g. Mora et al. 2009), with mafic magmatism present in some grabens (Vásquez and Altenberger 2005; Vásquez et al. 2010; Figs. 14 and 15). These observations can be interpreted in two ways: (1) Early Cretaceous eastward widening of the back-arc domain, with andesitic flows of the Las Brisas Fm. (Mantilla et al. 2006) marking the magmatic arc. Mafic plutonism in this scenario is the product of continued lithospheric stretching and thinning. (2) Two phases of rifting: an intra-arc rift during the Triassic to Jurassic, and a back-arc or intracontinental rift with mafic plutonism in the Early Cretaceous. (Fig. 14). The clear change in the type of magmatism and the pause of magmatism during the Late Jurassic lead us to favor two separate pulses of extension.

Conclusions

New U/Pb zircon ages obtained from ten samples of volcanic and volcaniclastic rock units constrain the evolution of Mesozoic rift basins in the Eastern Cordillera and Middle Magdalena Valley of Colombia. Our samples exhibit three types of zircon age pattern: (1) unimodal age distributions with Mesozoic mean ages, (2) polymodal age distributions with youngest zircons of Mesozoic age and variable admixture of older grains and (3) exclusively pre-Mesozoic zircons. The Mesozoic zircons range from about 209 to 167 Ma in age. The rocks sampled are associated with synrift deposits and the ages constrain the early phases of extension to the latest Triassic-Early Jurassic, substantially earlier than previously interpreted from zircon age patterns. The new zircon ages from the Girón and Jordán formations do not match the interpreted stratigraphic succession, suggesting that at least some synrift formations are diachronous and in part laterally equivalent.

Mesozoic grains in the Noreán, los Cobardes and Jordán regions most probably derive from the magmatism also expressed in Late Triassic-Early Jurassic plutons of the Santander Massif and San Lucas range. A small number of Precambrian grains is attributed to distal cratonic sources. In the Arcabuco region Mesozoic grains are absent, and the largest grain population has Lower-Middle Ordovician ages. These ages match the basement of the Floresta massif that we interpret as main sediment source for the Arcabuco region.

The mix of locally sourced Mesozoic and Paleozoic zircons with a distal Precambrian component from the Amazon craton suggests a segmented rift basin with depocenters on the hanging walls and source regions in the uplifted footwalls of active Mesozoic normal faults such as the Bucaramanga, Suarez and Boyacá faults. Age variations between the Noreán, Jordán and Girón formations suggest that volcanism and/or extensional basin formation, migrated from the central region of the Eastern Cordillera to the northwest during the latest Triassic to Early Jurassic, possibly related to slab roll-back. Early Cretaceous to middle Cretaceous mafic intrusions again are spread across the Eastern Cordillera. We propose that two clearly different extensional phases can be distinguished: the first extension event from the Late Triassic to the Early/Middle Jurassic occurred in an intra-arc position and was synchronous with voluminous calc-alkaline arc magmatism. Arc-related volcanic and volcaniclastic rocks including those dated here were accommodated in evolving rift basins bounded by normal faults. Only the second, Cretaceous extension event occurred in a back-arc setting and was associated with rift-related magmas of alkaline to tholeiitic composition, suggesting thinning of the lithosphere.