Emplacement of Jurassic - Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica)
Details
State: Public
Version: author
Serval ID
serval:BIB_8F7BEFDF459F
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Emplacement of Jurassic - Lower Cretaceous radiolarites of the Nicoya Complex (Costa Rica)
Journal
Geologica Acta
ISSN-L
1695-6133
Publication state
Published
Issued date
2006
Peer-reviewed
Oui
Volume
4
Pages
203-218
Language
english
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.
Keywords
Nicoya Complex. Jurassic-Cretaceous. Radiolarites. Cherts. Caribbean Plateau. Basalts. Gabbros. Pacific margin. Costa Rica.
Create date
23/01/2009 0:25
Last modification date
20/08/2019 15:53