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Title: Stratigraphic, tectonic and magmatic evolution of the early miocene oxaya formation ignimbrites, Central Andes
Author: Zalinge, Marit Elise van
ISNI:       0000 0004 6057 1219
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2016
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Between 22.7 Ma and 19.7 Ma a series of large volume ignimbrites, collectively known as the Oxaya Formation, covered large parts of the Western Andean Slope, in northernmost Chile, representing the onset of large volume ignimbrite volcanism in the Central Andes. Despite significant Miocene uplift and deformation, the Oxaya Formation is exceptionally well preserved, due to the dry climate of the Atacama Desert. Thorough examination of intact cores recovered from nine drill holes that penetrated the up to 1000 m thick Oxaya Formation enabled detailed reconstruction of the stratigraphic and magmatic evolution of the ignimbrites, as well as the tectonic evolution of the Western Andean Slope in this area. The Oxaya Formation consists of five members: the Poconchile ignimbrite; the volcaniclastic member; the Cardones ignimbrite; the Molinos ignimbrite; and the Oxaya ignimbrite. Medial and distal deposits of the 21.9 Ma Cardones ignimbrite are between 300 and 1000 m thick, . representing one of the thickest outflow sheets on Earth. A line-balanced reconstruction with the uneroded, but deformed, surface of this ignimbrite restores the covered pre-eruptive palaeotopography and constrains post-eruptive deformation. The extreme, but variable thickness of the Cardones ignimbrite results from a highly irregular pre-21.9 Ma palaeo-topography that was characterized by an up to 1700 m high proto-slope that was incised by rivers. After this palaeoslope was inundated by the Cardones ignimbrite, the area experienced up to 2000 m of structural relief of which ca. 80% can be attributed to fault-related folding into the ",40 km wide Huaylillas Anticline and ca. 20% to regional fore-arc tilting. The main folding likely occurred during the mid-and late Miocene and ceased by ca. 6 Ma.
Supervisor: Sparks, R.S.J. ; Cooper, F.J. ; Evenstar, L.A. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available