Volume 3
Chapter 17
https://doi.org/10.32685/pub.esp.37.2019.17 Published online 22 May 2020
Different Levels of Exhumation across the Bucaramanga Fault in the Cepitá Area of the Southwestern Santander Massif, Colombia: Implications for the Tectonic Evolution of the Northern Andes in Northwestern South America
Servicio Geológico Colombiano Dirección de Recursos Minerales Diagonal 53 n.° 34–53 Bogotá, Colombia
Sergio AMAYA–FERREIRA1* , Carlos Augusto ZULUAGA2 and Matthias BERNET3
,
Universidad Nacional de Colombia Sede Bogotá Departamento de Geociencias Carrera 30 n.° 45–03
Abstract Apatite and zircon fission–track data from crystalline rocks collected along an
east–to–west elevational profile across the Bucaramanga strike–slip fault in the Cepitá
area and thermal history modeling show the four–stage thermal history of the southwestern Santander Massif of the northern Andes in Colombia. A 60 my phase of burial heating from the Late Jurassic to the Late Cretaceous was followed by three cooling phases beginning in approximately 65–60 Ma, which were related to regional tectonic events. The Late Cretaceous – early Paleocene accretion of an island arc and interac-
tions of the Caribbean Plate with the northwestern South America plate first triggered
the surface uplift and erosional exhumation of the Santander Massif. During the late
Oligocene – early Miocene, the collision of the Panamá–Chocó Block with northwestern
South America caused an acceleration in the cooling and exhumation of the Santander
Massif and differential surface uplift to the east and west of the Bucaramanga Fault in
the Cepitá area. The present–day topography of the Santander Massif probably formed
at that time. Locally recorded late Miocene cooling may be related to movement on the
secondary fault pattern in the study area or minor magmatic activity.
Bogotá, Colombia
3
*[email protected] Université Grenoble Alpes Insitut des Sciences de la Terre 1381 rue de la piscine, CS 40700, 38058 Grenoble cedex 9, France Corresponding author
Keywords: exhumation, fission–track analysis, Santander Massif, Bucaramanga Fault, thermal modeling.
Resumen Datos de huellas de fisión en apatito y zircón de rocas cristalinas colectadas a lo largo de un perfil de elevación este–oeste a través de la Falla de Bucaramanga, falla de rumbo, en el área de Cepitá y el modelamiento de la historia termal muestran una historia termal en cuatro etapas para el suroeste del Macizo de Santander de los
Andes del norte en Colombia. A los 60 millones de años, una fase de calentamiento por
enterramiento desde el Jurásico Tardío al Cretácico Tardío fue seguida por tres fases de
enfriamiento que comenzaron aproximadamente a los 65–60 Ma, y están relacionadas
con eventos tectónicos regionales. En el Cretácico Tardío–Paleoceno temprano, la acre-
ción de un arco de islas y las interacciones de la Placa del Caribe con el noroccidente de la Placa de Suramérica desencadenaron el primer levantamiento de superficie y la
Citation: Amaya–Ferreira, S., Zuluaga, C.A. & Bernet, M. 2020. Different levels of exhumation
across the Bucaramanga Fault in the Cepitá area of the southwestern Santander Massif, Co- lombia: Implications for the tectonic evolution of the northern Andes in northwestern South America. In: Gómez, J. & Mateus–Zabala, D. (editors), The Geology of Colombia, Volume 3 Pa- leogene – Neogene. Servicio Geológico Colombiano, Publicaciones Geológicas Especiales 37, p. 491–507. Bogotá. https://doi.org/10.32685/pub.esp.37.2019.17
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exhumación erosiva del Macizo de Santander. Durante el final del Oligoceno y el Mioceno temprano, la colisión del Bloque Panamá–Chocó con el noroeste de Suramérica provocó la aceleración del enfriamiento y de la exhumación del Macizo de Santander
y la elevación diferencial de la superficie al este y al oeste de la Falla de Bucaramanga
en el área de Cepitá. Probablemente, la topografía actual del Macizo de Santander
se formó en ese momento. El enfriamiento del Mioceno tardío registrado localmente
puede estar relacionado con el movimiento en el patrón de falla secundaria en el área
de estudio o con la actividad magmática menor.
Palabras clave: exhumación, análisis de huellas de fisión, Macizo de Santander, Falla de Bucaramanga, modelamiento termal.
1. Introduction
Batholith in the Central Cordillera (Restrepo–Moreno et al.,
2009). Parra et al. (2012) argued, on the basis of AFT data from
The rise of orogenic mountain belts, particularly in the northern the Nuevo Mundo Syncline sedimentary basin fill and thermal
Andes, has a significant influence on regional climate and at- modeling, for a Paleocene – early Eocene (60–50 Ma) phase of
mospheric circulation and precipitation patterns, and forms bar
-
pronounced shortening and cooling of the western margin of
riers to species migration and the creation of new habitats and the Eastern Cordillera associated with tectonic inversion and ecological niches (e.g., Hoorn et al., 2010; Mapes et al., 2003). the first surface uplift and erosion of the Eastern Cordillera. For paleogeographic reconstructions, it is important to link the However, the Parra et al. (2012) study lacked information from
exhumation of deep–seated crystalline rocks and the formation ZFT or zircon (U–Th)/He thermochronometers and therefore
of high orogenic topography with the plate–tectonic evolution the pre–depositional thermal histories in their models were ful-
of the area of interest. Here, we present a study on the exhuma- ly unconstrained. Regardless, the absence of Cretaceous sed
-
tion history of the southern Santander Massif in northeastern imentary cover rocks in large areas of the Santander Massif,
Colombia because this mountain belt holds a key position in the which are otherwise widespread in the Eastern Cordillera of
northern Andes, forming the northwest–striking continuation of Colombia, suggests erosion was an important process during
the Eastern Cordillera at the junction between the Eastern Cor- the exhumation history of the Santander Massif. Evidence of
dillera and the Mérida Andes in Venezuela to the east (Figure 1). Paleogene and Neogene erosional exhumation of the Santander
The Santander Massif is part of the so–called Maracaibo Block, Massif basement and sedimentary cover rocks is preserved in
which is delineated by the Santa Marta–Bucaramanga and Oca the stratigraphic sequences of the Lisama, La Paz, Esmeraldas,
strike–slip Fault Systems and the southwestern fold–and–thrust Mugrosa, Colorado, and Real Formations in the Nuevo Mundo,
belt of the Mérida Andes (Figure 1; e.g., Colletta et al., 1997; Armas, and Andes Synclines of the Middle Magdalena Valley Mann et al., 2006). The Maracaibo Block also includes the Si- (Figure 1; Caballero et al., 2013; Parra et al., 2012; Sánchez et erra Nevada de Santa Marta and the serranía de Perijá (Figure al., 2012). Deformation of the Middle Magdalena Valley area
1). The cooling history of the crystalline rocks of the central and probably began during the Paleocene, with structures such as
southern Santander Massif has been previously studied with the Lisama Anticline (Caballero et al., 2013).
low–temperature thermochronology, with apatite fission–track
The objective of this study was to more precisely constrain
(AFT) ages ranging from 20 to 7 Ma and zircon fission–track the exhumation history of the southwestern Santander Massif
(ZFT) ages ranging from 172 to 20 Ma (Amaya et al., 2017; in the Cepitá area, to the east and west of the Chicamocha River
Shagam et al., 1984; van der Lelij et al., 2016; Villagómez et (Figure 2). Thus far, very few and spatially dispersed thermoal., 2011). In addition, from outcrops to the east of the city of chronological data have been published from this region (Ca-
Bucaramanga and the Bucaramanga Fault, Mora et al. (2015) ballero et al., 2013; Shagam et al., 1984; van der Lelij et al.,
first presented AHe ages between 8.2 and 16 Ma and ZHe ages 2016). Therefore, we present data of 10 AFT and 9 ZFT sam-
between 22.6 and 24.2 Ma. Along the same profile, Amaya et al. ples collected from igneous and metamorphic crystalline rocks
(2017) demonstrated an exhumed ZFT partial annealing zone, along a profile across the Chicamocha Canyon and the Buca-
which was rapidly exhumed between 25 and 20 Ma. All these ramanga Fault System near Cepitá, referred to here as the west-
data show the importance of late Oligocene regional tectonics ern and eastern blocks of the Santander Massif (Figures 2, 3), driving the exhumation of the Santander Massif along the Bu- respectively. The Chicamocha River does not exactly follow the caramanga Fault, which is related to the break–up of the Far- trace of the Bucaramanga Fault System but does mark the presallón Plate and the collision of the Panamá–Chocó Block with ent–day morphologic separation between the two blocks. While
northwestern South America (Farris et al., 2011; Taboada et the western block reaches an elevation of only approximately
al., 2000; O’Dea et al., 2016). This regional tectonic influence 1600 m in the study area, the eastern block rises to more than
has already been shown in the exhumation of the Antioquian 3200 m in this part of the Santander Massif (Figure 3). Expo-
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Different Levels of Exhumation across the Bucaramanga Fault in the Cepitá Area of the Southwestern Santander Massif, Colombia
Lesser Antillas
Caribbean Plate
OAF
- SSF
- SNSM
SP
10° N
MTB
Mérida Andes
Barinas Apure
Basin
SM
- Cocos Plate
- South American Plate
Llanos Orientales
Basin
NMS
5° N
EC
MMV
Guiana Shield
Nazca Plate
0°
Caguán–Vaupés
Basin
Oriente Basin
Amazonas Basin
- 0
- 200
- 400 km
study area
Figure 1. Overview map showing the major tectonic features of northern South America (modified from Colmenares & Zoback, 2003). (SCF)
Southern Caribbean Marginal Fault; (SNSM) Sierra Nevada de Santa Marta; (OAF) Oca–Ancón Fault; (SSF) San Sebastián Fault System; (LBESF)
Los Bajos–El Soldado Fault System; (SP) serranía de Perijá; (MTB) Maracaibo Triangular Block; (SBF) Santa Marta–Bucaramanga Fault; (BF) Boconó Fault; (PSZ) Panamá suture zone; (SM) Santander Massif; (GF) Garrapatas Fault; (IBF) Ibagué Fault; (NMS) Nuevo Mundo Syncline;
(EC) Eastern Cordillera; (MMV) Middle Magdalena Valley; (EAFFS) Eastern Andean Front Fault System; (DGM) Dolores–Guayaquil Megashear.
sure of crystalline rocks at high surface elevations implies both de Perijá, and the Mérida Andes of Venezuela along two of its
exhumation and surface uplift. The thermochronological data of three sides (Figure 1). Even if two of the main bounding faults of
this study were used in t–T models to provide constraints on the the Maracaibo Block, the dextral Oca Fault to the north and the
timing of cooling. The cooling histories were then interpreted sinistral Santa Marta–Bucaramanga Fault on its western flank,
in terms of erosional and tectonic exhumation. To constrain the are strike–slip fault systems with an unknown vertical offset,
difference in relative surface uplift between the western and considerable topographic surface elevations have been attained
eastern blocks, ZFT cooling ages at similar elevations on both in the Sierra Nevada de Santa Marta and the Santander Massif sides of the Bucaramanga Fault were compared. Furthermore, (up to 4530 m at Paramo del Almorzadero). The Santa Marta–
the apparent fission–track cooling ages were translated into ex- Bucaramanga Fault extends for over 600 km from Santa Marta
humation rates (e.g., Willett & Brandon, 2013) for the crystal- in the north to the Chicamocha Canyon, approximately 40–70 line rocks that were buried beneath sedimentary rocks at least km south of Bucaramanga, where it ceases defining the western since the Late Jurassic and throughout most of the Cretaceous. margin of the Santander Massif (Figure 1). The Boconó strike– slip fault dominates the late Miocene to Pliocene evolution and
2. Geological Setting
exhumation of the Mérida Andes of Venezuela (Bermúdez et
al. 2010, 2011, 2013; Kohn et al. 1984), but the southeastern
The fault–bounded triangular Maracaibo Block in the northern fold–and–thrust belt is thought to delimit the Maracaibo Block
Andes is an interesting geological feature, as this block not only to the southeast against the South American continental plate
hosts the highest coastal mountain belt in the world including (e.g., Figure 1; Colletta et al., 1997; Mann et al., 2006).
- the 5700 m–high Pico Cristobal Colón of the Sierra Nevada de
- Late Proterozoic to Paleozoic metamorphic rocks intruded
Santa Marta, but also features the Santander Massif, the serranía by Triassic and Jurassic plutonic rocks form the crystalline core
493
AMAYA–FERREIRA et al.
Triassic – Jurassic intrusives
7.30° N
Guaca–La Virgen (low–grade metamorphic rocks)
Páramo Rico Tonalite
Silos
Berlín
Orthogneiss
Bucaramanga
Paleozoic intrusive rocks Silgará Schists
Santa Barbara Quartz Monzonite
Bucaramanga Gneiss
La Corcova Quartz Monzonite
21.4 Ma
15.7 Ma
93 Ma
Zircon fission–track age this study
Guaca
13.7 Ma
21.4 Ma
18.9 Ma
Apatite fission–track age this study
Published zircon fission–track data
Published apatite fission–track data
6.86° N
20 Ma
172 Ma
18.5 Ma
Cepitá Aratoca
166.7 Ma
18.9 Ma
Jordán
25.1 Ma 24.6 Ma
5.4 Ma 6.9 Ma
25.3 Ma
7.3 Ma
34.5 Ma
12.9 Ma
127.5 Ma
88.7 Ma
Faults Folds
145.6 Ma
36.2 Ma
264.8 Ma
19.6 Ma
122.8 Ma
Mogotes
Quartz Monzonite
County
- 0
- 10
- 20 km
Figure 2. Geological map and sample locations. Taken and modified from Zuluaga & López (2018).
3500 3000 2500 2000 1500 1000
500
3500 3000 2500 2000 1500 1000
500
- Cepitá area apatite fission–track age profile
- Cepitá area zircon fission–track age profile
ab
Bucaramanga Fault zone
Bucaramanga Fault zone
Chicamocha River valley
- Western block
- Eastern block
- Western block
- Eastern block
34.5 ± 17.5
18.9 ± 7.1
36.2 ± 5.8 12.9 ± 4.6
25.1 ± 6.3
145.6 ± 25.7
166.7 ± 32.7
- 24.6 ± 3.9
- 5.4 ± 6.3
18.5 ± 4.8
25.3 ± 7.7
- 6.9 ± 2.4
- 88.7 ± 28.3
122.8 ± 18.3
127.9 ± 37.8
142.4 ± 21.2
7.3 ± 4.6
19.6 ± 9.6
264.8 ± 110.9
21.4 ± 5.5
- Topography
- Topography
- AFT age ± 2SE
- ZFT age ± 2SE
- 0
- 0
- Longitude (W)
- Longitude (W)
Figure 3. Topographic profile with sample locations.
of the Santander Massif (Goldsmith et al., 1971). In this study, (Figures 2, 3). The Jurassic and Cretaceous sedimentary cover only the late Proterozoic Bucaramanga Gneiss, Paleozoic Sil- rocks, with a cumulative thickness of ca. 2500 to ca. 3500 m
gará Schists, Jurassic Mogotes Batholith and Pescadero Granite (Shagam et al., 1984), were used as a constraint for thermal
are of interest because samples were only collected from these history modeling for the phase and amplitude of the Jurassic lithological units to the east and west of the Chicamocha River and Cretaceous burial heating in the study area. A zircon fission
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Different Levels of Exhumation across the Bucaramanga Fault in the Cepitá Area of the Southwestern Santander Massif, Colombia
track age in the study area of 172.0 ± 16.4 Ma from the Pes-
Our study also employed the most robust and revealing
cadero Granite of van der Lelij et al. (2016) indicates that burial method plotting length against a kinetic parameter (Dpar),
heating was insufficient to fully reset the zircon fission–track noting whether trends exist and, if possible, defining coherent
system to the west of the Bucaramanga Fault. Our samples of kinetic populations (e.g., Burtner et al., 1994). This approach the western profile were collected between 612 and 1347 m not only can result in more accurate age interpretation but also
elevation between Cepitá and Aratoca, whereas eastern profile allows length data to be segregated to enable proper inverse
samples were collected from elevations ranging between 900 modeling. Because fission–track lengths shorten as a function
and 1050 m to the east of Cepitá (Figure 2; Table 1).
of the thermal history they have undergone, a set of length mea-
The Chicamocha River is a tributary of the Magdalena surements constitutes an integrated record of the temperatures
River. In the Cepitá area, the Chicamocha River flows in a experienced by a sample.
N–NW direction, before following the secondary NE–SW–
oriented fault pattern of the Santander Massif and turning to 3.3. Exhumation Rate Estimates
the SW and flowing toward the village of Jordán (Figure 2). In
the study area, the Chicamocha Canyon shows at least 1000 First–order exhumation rates based on AFT and ZFT ages can
m of incision with respect to the highest elevations of the be estimated from the simple 1–D thermal advection mod-
western block (Figure 3).
el age2dot created by Mark BRANDON (see Ehlers et al.,
2005). For these first–order estimates, we assumed a constant
pre–exhumation thermal gradient of 30 °C/km, which we ac-
knowledge is a very simplistic assumption but sufficient for the
purpose of this study. The AFT model was selected for chlorine
apatite, which is justifiable with regard to the measured Dpar
3. Methods
3.1. Fission–Track Analysis
Sample preparation for the fission–track analysis was complet- values shown in Table 2. For the ZFT model, we selected an-
ed at the Servicio Geológico Colombiano in Bogotá, following nealing parameters for radiation–damaged zircon, given that
the methodology described by Amaya et al. (2017). All samples the ZFT cooling ages are on average older than 100 Ma for
were irradiated at the FRM II research reactor in Garching, the western block. For the eastern block samples 13SACZ03
Germany. For track length measurements of horizontally con- and 07, we used a zero–damage model, considering that these
252
fined tracks, apatite samples were irradiated with Cf at the zircons rapidly cooled below the zircon fission–track closure
University of Melbourne. Samples were analyzed dry at 1250x temperature and through the zircon partial annealing zone bewith an Olympus BX51 optical microscope, using the FTStage tween 25 and 20 Ma (Table 3).
4.04 system of Trevor Dumitru in the fission–track laboratory
of the Servicio Geológico Colombiano in Bogotá and in the 4. Results
fission–track laboratory at ISTerre, Université Grenoble Alpes.
4.1. Fission–Track Data
3.2. Time–Temperature History Modeling
The samples from the western profile, to the west of the
For t–T history modeling of the western profile samples, we used Chicamocha River and the Bucaramanga Fault zone, have
the QTQt program (v 4.6) of Gallagher (2012) to model age pairs AFT ages between 36 and 7 Ma depending on elevation
of samples for which we have AFT and ZFT data and length mea- (Figure 4a). The lowest sample, i.e., 12SACEP11 from the
surements of horizontally confined tracks in apatite. The QTQt Silgará Schists, yields a central AFT age of 21.4 ± 5.5 Ma
program determines cooling history scenarios using a Bayesian and was collected at 612 m along the secondary fault pat-