Volume 2 Quaternary Chapter 10 Neogene https://doi.org/10.32685/pub.esp.36.2019.10 Cretaceous Record from a Mariana– to an Published online 15 May 2020 Andean–Type Margin in the Central Cordillera 1 [email protected] of the Colombian Andes Universidad Nacional de Colombia Paleogene Sede Medellín Facultad de Minas Departamento de Procesos y Energía 1 2 3 Agustín CARDONA * , Santiago LEÓN , Juan S. JARAMILLO , Grupo de Investigación en Geología y 4 5 6 Geofísica (EGEO) Victor A. VALENCIA , Sebastian ZAPATA , Andrés PARDO–TRUJILLO , Medellín, Colombia 7 8 9 Axel K. SCHMITT , Dany MEJÍA , and Juan Camilo ARENAS 2 [email protected] Cretaceous Universidad Nacional de Colombia Abstract The Cretaceous tectonic evolution of the western margin of South America Sede Medellín Grupo de Investigación en Geología y involves a shift from an extensional convergent margin toward a more compressional Geofísica (EGEO) Medellín, Colombia setting that marks the beginning of the Andean Orogeny. In the Colombian Andes, this Smithsonian Tropical Research Institute Jurassic changing scenario is recorded in the Cretaceous sedimentary and magmatic rocks of Ancón, Panamá 3 [email protected] the Central Cordillera. A review of field relationships, together with analysis of inte- Universidad Nacional de Colombia grated provenance constraints, including sandstone petrography and detrital zircon Sede Medellín Facultad de Minas geochronology from various localities, suggests that during the Early Cretaceous until Departamento de Materiales y Minerales the Aptian – Albian, siliciclastic basin fills were characterized by transgressive fining– Grupo de Investigación en Geología y Triassic Geofísica (EGEO) upward trends, with prominent first–cycle quartzose provenances that indicate strong Medellín, Colombia chemical weathering in the source areas. Jurassic, Triassic, and older detrital zircon 4 [email protected] Washington State University U–Pb ages suggest that the igneous and metamorphic rocks forming the basement School of the Environment Pullman, USA of the Central Cordillera were the main sources. Furthermore, the presence of Early Permian 5 [email protected] Cretaceous detrital ages between 120 and 100 Ma, together with interlayered volcanic Smithsonian Tropical Research Institute Ancón, Panamá rocks at the top of the sequence characterized by mixed arc–like, MORB, and E–MORB Missouri University of Science and Technology geochemical signatures, can be related to the evolution of an extensional arc with Department of Geology and Geophysics USA associated back–arc basin formation. Plutonic rocks with ca. 98 Ma crystallization ages 6 [email protected] Universidad de Caldas show Nd, Sr, Hf, and O isotope evidence for the existence of thinned continental crust Carboniferous Instituto de Investigaciones en Estratigrafía that may account for the dominant mantle signature. By ca. 93 Ma, the Early Creta- (IIES) ceous sedimentary sequences were deformed and intruded by plutonic rocks, which Manizales, Colombia 7 [email protected] conversely show isotopic fingerprints characteristic of crustal signatures that can be Heidelberg University Institute of Earth Sciences explained by the involvement of thicker crust that promoted melt interaction with the Devonian Heidelberg, Germany more radiogenic host rocks. 8 [email protected] This tectonic change from a Mariana– to an Andean–type subduction style was Universidad Nacional de Colombia Sede Medellín probably triggered by regional–scale plate kinematic reorganizations, as suggested by Facultad de Minas similar coeval tectonic scenarios along the entire South American margin, and set the Departamento de Materiales y Minerales Grupo de Investigación en Geología y Silurian conditions for the construction of the Andean chain. Geofísica (EGEO) Medellín, Colombia Keywords: Cretaceous, back-arc, intra–arc, Andean Orogeny, Geochemistry. 9 Universidad Nacional de Colombia Sede Medellín Departamento de Geociencias y Medio Resumen La evolución tectónica del borde occidental de Suramérica durante el Cre- Ambiente Medellín, Colombia tácico está marcada por el cambio de un margen convergente extensional hacia una Ordovician configuración más compresiva que marca el inicio de la Orogenia Andina. En los Andes * Corresponding author Citation: Cardona, A., León, S., Jaramillo, J.S., Valencia, V., Zapata, S., Pardo–Trujillo, A., Schmitt, Supplementary Information: A.K., Mejía, D. & Arenas, J.C. 2020. Cretaceous record from a Mariana– to an Andean–type margin Cambrian in the Central Cordillera of the Colombian Andes. In: Gómez, J. & Pinilla–Pachon, A.O. (editors), S: https://www2.sgc.gov.co/ The Geology of Colombia, Volume 2 Mesozoic. Servicio Geológico Colombiano, Publicaciones LibroGeologiaColombia/tgc/ Geológicas Especiales 36, p. 335–373. Bogotá. https://doi.org/10.32685/pub.esp.36.2019.10 sgcpubesp36201910s.pdf 335 Proterozoic CARDONA et al. colombianos, este cambio está registrado en las rocas sedimentarias y magmáticas cretácicas de la cordillera Central. La revisión de las relaciones de campo, junto con el análisis de procedencia de rocas siliciclásticas (petrografía de areniscas y geocro- nología en circones detríticos de varias localidades), sugiere que durante el Cretácico Temprano hasta el Aptiano–Albiano el relleno siliciclástico de la cuenca se caracterizó por tener un carácter transgresivo granodecreciente y una composición cuarzosa con componentes de primer ciclo asociados a condiciones de meteorización intensa en el área fuente. Las edades U–Pb en circón jurásicas, triásicas y más antiguas sugieren que las fuentes principales fueron las rocas ígneas y metamórficas que conforman el basa- mento de la cordillera Central. Además, la presencia de edades detríticas del Cretácico Temprano entre 120 y 100 Ma, junto con la de rocas volcánicas intercaladas al tope de la secuencia que se caracterizan por una mezcla de firmas geoquímicas de arco, MORB y E–MORB, puede estar relacionada con la evolución de un arco extensional y la for- mación de una cuenca de retroarco. Las rocas plutónicas con edades de cristalización de ca. 98 Ma muestran evidencias isotópicas de Nd, Sr, Hf y O de afinidad mantélica que estarían asociadas a la existencia de una corteza continental adelgazada. A los ca. 93 Ma, las secuencias sedimentarias del Cretácico Temprano fueron deformadas e in- truidas por rocas plutónicas, las cuales en cambio muestran características isotópicas corticales que pueden explicarse por la participación de una corteza más gruesa que promovió la interacción del fundido con las rocas caja más radiogénicas. Este cambio tectónico de un estilo de subducción de tipo Marianas a uno de tipo andino es común en toda la margen continental suramericana y estaría asociado con reorganizaciones cinemáticas a escala de placas que marcarían el inicio de la cons- trucción de la cadena andina. Palabras clave: Cretácico, retroarco, intraarco, Orogenia Andina, geoquímica. 1. Introduction geochemical data, together with new results from magmatic and detrital zircon U–Pb geochronology, whole–rock geo- During the Cretaceous, the western margin of South Ameri- chemistry, zircon Hf and O isotopes, sandstone petrography, ca experienced a major change from a dominantly extensional and field relationships of Cretaceous units from selected lo- system (Mariana–type) toward a more compressional tecton- calities exposed between the two flanks of the Central Cor- ic style (Chile–type; Uyeda & Kanamori, 1979; Stern, 2012), dillera of the Colombian Andes (Figure 1). The analysis of which marks the initiation of the Andean orogeny (see reviews available data and the new data presented here allows doc- in Tunik et al., 2010; Horton, 2018). Whereas the Mesozoic umenting an Aptian – Albian extensional margin associat- – Cenozoic tectonic evolution of the central and southern An- ed with the formation of different intra–arc and back–arc dean segments was characterized by a subduction–dominated extensional domains, which were inverted and deformed orogeny, the northern Andes constitutes a classic accretionary before 90 Ma and subsequently experienced the formation orogen in which interspersed terrane accretion and subduction of a younger Late Cretaceous arc and the collision of an tectonics were responsible for orogenic growth (see a review intra–oceanic terrane. in Ramos, 2009). With such a complex scenario and the con- The Early to Late Cretaceous record in the Central Cor- tinuous superimposition of tectonic events, clear discrimination dillera provides additional constraints on the continental–scale between subduction–dominated extensional and compressional transition from extension to compression that gave rise to the tectonics remains a major challenge. Andean Orogeny (Horton, 2018; Tunik et al., 2010). The long–term spatiotemporal and compositional changes in magmatic rocks integrated with the stratigraphic and prove- 2. Geological Setting nance evolution of contemporaneous basins are sensitive mark- ers of the evolution of convergent margins and can be used to Within the Colombian Andes, the Cretaceous geological re- address alternating settings between extension and compression cord is found in three different tectonostratigraphic domains, (Busby, 2012; Cawood et al., 2009; Marsaglia, 2012). which closely coincide with major morphostructural features In this contribution, we present a review of published represented by the three main cordilleras and the intervening field observations and petrographic, geochronological,