Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica)
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| Formato: | Artículo científico |
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Universitat de Barcelona
2006
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| _version_ | 1876488997851627520 |
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| author | P. Denyer |
| author_facet | P. Denyer |
| contents | Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica) P. Denyer P.O. Baumgartner Ciencias de la Tierra Cherts Basalts Gabbros Jurassic Cretaceous We present a new model to explain the origin, emplacement and stratigraphy of the Nicoya Complex in the NWpart of the Nicoya Peninsula (Costa Rica) based on twenty-five years of field work, accompanied with the evolutionof geochemical, vulcanological, petrological, sedimentological and paleontological paradigms. Theigneous-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 CaribbeanPlateau, in which the deepest levels are exposed in the NW-Nicoya Peninsula. Over 50% of the igneous rocksare intrusive (gabbros and in less proportion plagiogranites) which have a single mantle source; the remainderare basalts with a similar geochemical signature. Ar39/Ar40 radioisotopic whole rock and plagioclase ages rangethroughout 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 (MiddleJurassic) to Albian (middle Cretaceous). These Mn-radiolaritic blocks are set in a matrix of multiple gabbrosand diabases intrusions. Chilled margins of magmatites, and hydrothermal baking and leaching of the radiolaritesconfirm the Ar39/Ar40 dating of igneous rocks being consistently younger than most of the radiolariancherts. 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 multiplemagmatic 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. 2006 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50540212 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.1-2 Vol.4 |
| format | Artículo científico |
| id | redalyc_50540212 |
| institution | Redalyc |
| language | en |
| publishDate | 2006 |
| publisher | Universitat de Barcelona |
| spellingShingle | Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica) P. Denyer Ciencias de la Tierra Cherts Basalts Gabbros Jurassic Cretaceous Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica) P. Denyer P.O. Baumgartner Ciencias de la Tierra Cherts Basalts Gabbros Jurassic Cretaceous We present a new model to explain the origin, emplacement and stratigraphy of the Nicoya Complex in the NWpart of the Nicoya Peninsula (Costa Rica) based on twenty-five years of field work, accompanied with the evolutionof geochemical, vulcanological, petrological, sedimentological and paleontological paradigms. Theigneous-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 CaribbeanPlateau, in which the deepest levels are exposed in the NW-Nicoya Peninsula. Over 50% of the igneous rocksare intrusive (gabbros and in less proportion plagiogranites) which have a single mantle source; the remainderare basalts with a similar geochemical signature. Ar39/Ar40 radioisotopic whole rock and plagioclase ages rangethroughout 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 (MiddleJurassic) to Albian (middle Cretaceous). These Mn-radiolaritic blocks are set in a matrix of multiple gabbrosand diabases intrusions. Chilled margins of magmatites, and hydrothermal baking and leaching of the radiolaritesconfirm the Ar39/Ar40 dating of igneous rocks being consistently younger than most of the radiolariancherts. 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 multiplemagmatic 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. 2006 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50540212 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.1-2 Vol.4 |
| title | Emplacement of Jurassic-Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica) |
| topic | Ciencias de la Tierra Cherts Basalts Gabbros Jurassic Cretaceous |
| url | https://www.redalyc.org/articulo.oa?id=50540212 |