From arc-continent collision to continuous convergence, clues from Paleogene conglomerates along the southern CaribbeanaSouth America plate boundary

• Published in: Tectonophysics 2012-12, Vol.580, p.58-87
• Main Authors: Cardona, A, Montes, C, Ayala, C, Bustamante, C, Hoyos, N, Montenegro, O, Ojeda, C, Nino, H, Ramirez, V, Valencia, V, Rincon, D, Vervoort, J, Zapata, S
• Format: Article
• Language: English
• Subjects: Basins; Boundaries; Convergence; Deformation; Exposure; Geochronology; Hafnium; Preserves
• ISSN: 0040-1951
• DOI: 10.1016/j.tecto.2012.08.039

A Paleogene conglomeratic-sandy succession preserves the complex record of arc-continent collision, orogen collapse and basin opening, followed by inversion related to renewed oblique convergence. This record is unique because both arc and continental margin are now severely fragmented and only partially exposed along the southern CaribbeanaSouth American boundary in northern Colombia. We studied these clastic sequences in the San Jacinto deformed belt using an integrated provenance study that includes conglomerate clast counting, geochemistry and UaPb and Hf isotopic analysis in magmatic clasts, together with sandstone petrography, heavy mineral analysis and detrital zircon UaPb geochronology. The record of events extracted from these coarse clastic rocks includes the formation and approach of an allochthonous Upper Cretaceous intra-oceanic arc active from 88 Ma until 73 Ma. This arc collides against the upper Paleozoic to Triassic continental margin after 73 Ma, but before late Paleocene times. Poorly exposed remnants of serpentinized peridotites and middle pressure metamorphic detritus are related to closure of an intervening oceanic basin between the continent and the colliding arc. This orogen was emerged in late Maastrichtianaearly Paleocene, and then collapsed as recorded by the thick upper Paleocene and younger succession of the San Jacinto deformed belt where the coarse clastics, subject of this study, are exposed.