Geology and stratigraphy of the sheet 3246-ii Miramar, Costa Rica

[摘要] The oldest rocks of the Miramar sheet are represented by sediments of the Punta Carballo Formation (Miocene), which are exposed at the SW corner. However, volcanic rocks of the older Aguacate Group (Miocene-Pliocene) and overlying Monteverde Formation (Lower Pleistocene) dominate the area. The Pliocene to Pleistocene silicic ignimbrites and Quaternary sediments are subordinate. New K-Ar ages yielded 4,41±0,15 to 4,99±0,36 Ma for the Aguacate Group and 1,71±0,22 to 1,77±0,11 Ma for the Monteverde Formation. Gabrodioritic stock was newly mapped in the Aguacate Group accompanying numerous other intrusive bodies of variable composition. New K-Ar ages were obtained for the rhyodacitic domes: 1,71±0,14 Ma for the cerro La Cruz Dome and 1,59±0,12 Ma for the cerro San Miguel Dome. Definition of volcanic units is based on detailed petrography, XRD, microprobe and 33 new bulk-rock chemical analyses.

[学科分类] 地质学

[关键词] /span> geological map;Miramar;stratigraphy;K-Ar geochronology;geochemistry;Costa RicaResumenLas rocas más antiguas de la hoja Miramar están conformadas por los sedimentos de la Formación Punta Carballo del Mioceno que afloran al SO de la hoja