Abstract

Three major volcanic events have occurred in Nicaragua since middle Tertiary time. First, the Oligocene was dominated by rhyolite shield volcanism, producing the Highland ignimbrite. Second, creation of northeast- and later northwest-striking dilatational fracture zones allowed the extrusion of basaltic to andesitic magmas along the Pacific coast, constructing the northwest-oriented Coyol volcanic arc. This Miocene arc can be followed all along the Pacific coast of the Chortis block. Third, a Pliocene-Pleistocene southwestward shift of arc volcanism created the modern volcanic arc. This volcanic history is supported by a new stratigraphy based on volcanic centers and related facies. The old cyclic, layer-cake stratigraphy of the Coyol Group has been abandoned.

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