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Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica)

Show simple item record Denyer, P. Baumgartner, P. O. 2016-10-31T16:56:23Z 2016-10-31T16:56:23Z 2006
dc.identifier.citation Denyer, P.; Baumgartner, P.O.; (2006). Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica). Geologica Acta: an international earth science journal, Sin mes, 203-218. es_CR
dc.identifier.issn 1695-6133
dc.identifier.uri 10.1344/105.000000366
dc.description.abstract We present a new model to explain the origin, emplacement and stratigraphy of the Nicoya Complex in the NW part of the Nicoya Peninsula (Costa Rica) based on twenty-five years of field work, accompanied with the evolution of geochemical, vulcanological, petrological, sedimentological and paleontological paradigms. The igneous-sedimentary relation, together with radiolarian biochronology of the NW-Nicoya Peninsula is re-examined. We interpret the Nicoya Complex as a cross-section of a fragment of the Late Cretaceous Caribbean Plateau, in which the deepest levels are exposed in the NW-Nicoya Peninsula. Over 50% of the igneous rocks are intrusive (gabbros and in less proportion plagiogranites) which have a single mantle source; the remainder are basalts with a similar geochemical signature. Ar39/Ar40 radioisotopic whole rock and plagioclase ages range throughout the area from 84 to 83 Ma (Santonian) for the intrusives, and from 139 to 88 Ma (Berriasian-Turonian) for the basalts. In contrast, Mn-radiolarites that crop out in the area are older in age, Bajocian (Middle Jurassic) to Albian (middle Cretaceous). These Mn-radiolaritic blocks are set in a “matrix” of multiple gabbros and diabases intrusions. Chilled margins of magmatites, and hydrothermal baking and leaching of the radiolarites confirm the Ar39/Ar40 dating of igneous rocks being consistently younger than most of the radiolarian cherts. No Jurassic magmatic basement has been identified on the Nicoya Peninsula. We interpret the Jurassic-Cretaceous chert sediment pile to have been disrupted and detached from its original basement by multiple magmatic events that occurred during the formation of the Caribbean Plateau. Coniacian-Santonian (Late Cretaceous), Fe-rich radiolarites are largely synchronous and associated with late phases of the Plateau. es_CR
dc.language.iso en_US es_CR
dc.publisher Geologica Acta es_CR
dc.subject Nicoya Complex es_CR
dc.subject Jurassic-Cretaceous es_CR
dc.subject Radiolarites es_CR
dc.subject Cherts es_CR
dc.subject Caribbean Plateau es_CR
dc.subject Basalts es_CR
dc.subject Gabbros es_CR
dc.subject Pacific margin es_CR
dc.subject Costa Rica es_CR
dc.subject complejo de Nicoya es_CR
dc.subject Jurásico-Cretácico es_CR
dc.subject radiolaritas es_CR
dc.subject sílex es_CR
dc.subject meseta del Caribe es_CR
dc.subject basaltos es_CR
dc.subject gabros es_CR
dc.subject margen pacífico es_CR
dc.title Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica) es_CR
dc.type Article es_CR

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