The volcanic section at Nazas, Durango, Mexico, and the possibility of widespread Eocene volcanism within the Sierra Madre Occidental
Por:
Aguirre-Diaz G.J., McDowell F.W.
Publicada:
1 ene 1991
Resumen:
At Nazas, Durango, on the eastern flank of the Sierra Madre Occidental, a well-exposed section includes voluminous felsic volcanic rocks of both Eocene and Oligocene age. The oldest igneous rocks at Nazas include a small exposure of intermediate volcanic breccias and lava flows that overlie Cretaceous limestones and apparently were deformed with them during Laramide tectonism. More commonly, the limestones are overlain by Tertiary volcanic rocks and continental clastic deposits. The Tertiary volcanic section is about 800m thick, not including intercalated fanglomerates. The section records three distinct magmatic episodes: from 51 to 40 Ma, comprising felsic ash flow tuffs and intermediate lava flows and domes; a pulse at about 30 Ma, comprising voluminous felsic ash flow tuffs with an aggregate thickness of about 500 m; and from 24 to 20 Ma, comprising alkalic basalts. The composition and volcanic styles of Eocene and Oligocene rocks are compared. -after Authors
Filiaciones:
Aguirre-Diaz G.J.:
Dept Geological Sciences, Univ of Texas at Austin, TX, USA, United States
McDowell F.W.:
Dept Geological Sciences, Univ of Texas at Austin, TX, USA, United States
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