The making of a high elevation plateau: Insights from the central Andean Plateau, Bolivia

Persistent Link:
http://hdl.handle.net/10150/290035
Title:
The making of a high elevation plateau: Insights from the central Andean Plateau, Bolivia
Author:
McQuarrie, Nadine
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The structural link that ties the formation of the central Andean plateau to the evolution of the Andean fold-thrust belt is formation and propagation of basement megathrusts. Balanced cross-sections through a regional west-vergent thrust system in the hinterland of the eastward-verging Andean fold-thrust belt suggest that the Altiplano basin is a crustal-scale, piggy-back basin created as a basement megathrust propagated up and over a half-crustal scale ramp located on the eastern edge of the Altiplano. The backthrust belt, detached above the basement thrust sheet, acted as a crustal-scale, passive-roof duplex building taper after the megathrust overextended the system eastward. Pervasive shortening and vertical elongation seen at the outcrop and regional scales supports the development of the backthrust belt as a taper-building mechanism. The interrelationship of the backthrust belt, basement megathrust, and Andean plateau is shown in a sequential, kinematic model based on balanced cross sections from the volcanic arc to the foreland. The model links the formation of the plateau to east- and west-verging portions of the Andean fold-thrust belt through the eastward propagation of two large basement megathrusts. The megathrusts can explain topographic and structural steps in the Andean fold-thrust belt and accommodate a minimum of 300-330 km of shortening which matches shortening estimates in the tightly folded and faulted cover rocks. To a first approximation, the eastern margin of the central Andean plateau (defined by the 3 km topographic contour) is contiguous with the leading edge of the upper basement megathrust. The relationship between the basement highs and the physiographic boundaries of the Andean plateau suggests that extensive megathrust sheets (involving strong rocks such as crystalline basement or quartzite) play an important role in the formation of the central Andean plateau. Combining the history of foreland basin migration with palinspastically restored regional cross sections across the Bolivian Andes between 18°-20°S argues for an eastward migrating fold-thrust belt/foreland basin system since the late Cretaceous. The longer time span for the Andean orogeny implies greater shortening amounts, a decrease in shortening rates with time and a high (3-4 km) Andean plateau by 20 Ma.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Earth Sciences
Degree Grantor:
University of Arizona
Advisor:
DeCelles, Peter G.; Davis, George H.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleThe making of a high elevation plateau: Insights from the central Andean Plateau, Boliviaen_US
dc.creatorMcQuarrie, Nadineen_US
dc.contributor.authorMcQuarrie, Nadineen_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe structural link that ties the formation of the central Andean plateau to the evolution of the Andean fold-thrust belt is formation and propagation of basement megathrusts. Balanced cross-sections through a regional west-vergent thrust system in the hinterland of the eastward-verging Andean fold-thrust belt suggest that the Altiplano basin is a crustal-scale, piggy-back basin created as a basement megathrust propagated up and over a half-crustal scale ramp located on the eastern edge of the Altiplano. The backthrust belt, detached above the basement thrust sheet, acted as a crustal-scale, passive-roof duplex building taper after the megathrust overextended the system eastward. Pervasive shortening and vertical elongation seen at the outcrop and regional scales supports the development of the backthrust belt as a taper-building mechanism. The interrelationship of the backthrust belt, basement megathrust, and Andean plateau is shown in a sequential, kinematic model based on balanced cross sections from the volcanic arc to the foreland. The model links the formation of the plateau to east- and west-verging portions of the Andean fold-thrust belt through the eastward propagation of two large basement megathrusts. The megathrusts can explain topographic and structural steps in the Andean fold-thrust belt and accommodate a minimum of 300-330 km of shortening which matches shortening estimates in the tightly folded and faulted cover rocks. To a first approximation, the eastern margin of the central Andean plateau (defined by the 3 km topographic contour) is contiguous with the leading edge of the upper basement megathrust. The relationship between the basement highs and the physiographic boundaries of the Andean plateau suggests that extensive megathrust sheets (involving strong rocks such as crystalline basement or quartzite) play an important role in the formation of the central Andean plateau. Combining the history of foreland basin migration with palinspastically restored regional cross sections across the Bolivian Andes between 18°-20°S argues for an eastward migrating fold-thrust belt/foreland basin system since the late Cretaceous. The longer time span for the Andean orogeny implies greater shortening amounts, a decrease in shortening rates with time and a high (3-4 km) Andean plateau by 20 Ma.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEarth Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDeCelles, Peter G.en_US
dc.contributor.advisorDavis, George H.en_US
dc.identifier.proquest3010264en_US
dc.identifier.bibrecord.b41714933en_US
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