Evidence of Early to Middle Ordovician arc volcanism in the Cordillera Oriental and Altiplano of southern Peru, Ollantaytambo Formation and Umachiri beds

Abstract:

Volcanic rocks of intermediate to predominantly mafic composition are exposed in the Cordillera Oriental and Altiplano of southern Peru in two localities: (1) the Ollantaytambo Formation, which crops out near Cusco, and (2) the Umachiri beds in the Departamento de Puno. The most notable unit in the Ollantaytambo Formation is an approximately 100m thick succession of lapilli tuffs that originated by hydroclastic fragmentation. These volcanic rocks are of calc-alkaline basaltic to andesitic composition. The tuffs are overlain by fine-grained volcaniclastic sandstones and shales, which grade into quartz-rich turbidites. The Umachiri beds consist of monomict lapilli tuffs with varying lapilli abundance and size, formed by hydroclastic fragmentation, and volcaniclastic sandstones. The rocks have a uniform basaltic andesite composition and tholeiitic affinity. Chondrite-normalized element patterns of both volcanigenic units …

Año de publicación:

2006

Keywords:

Fuente:

google