HR: 15:00h
AN: U53A-05    [Abstracts]
TI: Tectonic growth of a Cretaceous-Eocene accretionary orogen formed at the southern margin of the Caribbean Plate: integrated geological insights from northernmost Colombia
AU: * Cardona, A
EM: cardonaa@si.edu
AF: Smithsonian Tropical Research Institute, Balboa, Ancon, Panama, Panama
AU: Weber, M B
EM: mweber@unalmed.edu.co
AF: Universidad Nacional de Colombia, Carrera 80, #65-223, Medellin, Colombia
AU: Bayona, G
EM: gbayona@cgares.org
AF: Smithsonian Tropical Research Institute, Balboa, Ancon, Panama, Panama
AU: Bayona, G
EM: gbayona@cgares.org
AF: Corporación Geológica Ares, Calle 57, #23-09 Of. 202, Bogota, Colombia
AU: Jaramillo, C
EM: jaramillo@si.edu
AF: Smithsonian Tropical Research Institute, Balboa, Ancon, Panama, Panama
AU: Montes, C
EM: Camilo.Montes@Cerrejoncoal.com
AF: Carbones de Cerrejón, Calle 100, #21-64, Piso 12 , Bogotá, Colombia
AU: Ojeda, G
EM: german.ojeda@ecopetrol.com.co
AF: Instituto Colombiano del Petroleo, Km 14, Autopista Piedecuesta, Bucaramanga, Colombia
AU: Duque, J F
EM: jduquetr@gmail.com
AF: IGEOMINAS, Diagonal 53, #34-53, Bogota, Colombia
AU: Salazar, C A
EM: csalazar@usp.br
AF: Universidade de Sao Paulo, Rua do Lago 562, Sao Paulo, Brazil
AB: Geological characteristics from the Cretaceous to Eocene metamorphic and igneous basement rocks from the Guajira and the NW corner of the Sierra Nevada de Santa Marta massifs in the northern Colombian Caribbean region, and the stratigraphy of adjacent basins, reveal different stages of growth of a segmented Late Cretaceous to Eocene accretionary orogen formed by interaction between the NW margin of South America and the Caribbean plate. Extensive intercalations of metavolcano-sedimentary rocks in the Santa Marta region, chemical composition of spinels and pyroxenes from serpentinized mantle tectonites and gabbros, as well as whole rock geochemistry from basaltic dykes from the Guajira massifs, record the evolution of a Cretaceous intra-oceanic arc in a succesion of Mariana- and Chile-type subduction styles. Geological and positive gravity signatures suggest that this arc was accreted and tectonically underplated to the continental margin of South America, creating a Maastrichian-Paleocene syn-orogenic basin, presently cropping out in the Cesar-Rancheria valley. After this collisional event, subduction of the Caribbean plate under South America started, as revealed by intrusion of composite stitched Late Paleocene-Eocene granitoids in the NW corner of the SNSM and Guajira massifs. These plutons show continental calc-alkaline geochemical signatures and more evolved Sr and Nd isotopic compositions than juvenile and older intra-oceanic arc magmatic rocks. This new subduction environment is linked to the convergence between North and South America at this time. Low pressure estimations and fast cooling rates between 450-250° for the Eocene granitoids in the Guajira and Santa Marta regions, indicate shallow < 7 Km depths of intrusion. Local unconformable stratigraphic relationships with Eocene-Miocene sediments at the Guajira region and overimposed post-magmatic low temperature deformation in some of these granitoids suggest an important Late Eocene unroofing and deformational event that may record the regional modification of plate motion vectors and rates that controlled the Late Eocene- Miocene Caribbean orogenic phase.
DE: 1115 Radioisotope geochronology
DE: 8100 TECTONOPHYSICS
DE: 8139 Obduction tectonics
SC: Union [U]
MN: 2007 Joint Assembly