Basement-cored uplift deformation in the northern Sierras Pampeanas: Three-dimensional uplift structure, basement deformation, and regional analysis

Persistent Link:
http://hdl.handle.net/10150/280775
Title:
Basement-cored uplift deformation in the northern Sierras Pampeanas: Three-dimensional uplift structure, basement deformation, and regional analysis
Author:
Elena García, Pilar
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 structure of basement-cored uplift mountains is fundamentally controlled by the geometry of the basement and the basement unconformity. In the Sierra de Hualfin, an uplift located in the Sierras Pampeanas of NW Argentina, the well-exposed basement unconformity displays along-strike structural variations. The Sierra de Hualfin is composed of a core of Ordovician granitoid overlain by and thrust over Tertiary sedimentary rocks. The range is uplifted by an east-directed thrust fault, creating a steep range-front on the east and a gently dipping backlimb on the west. In the central region, however, basement and cover rocks in the backlimb are folded. Cross sections across the uplift and a three-dimensional computer model show that the variations along strike are due to differences in the geometry of the underlying fault or faults that deform the basement unconformity. Analysis of the folded basement unconformity on the west side of Sierra de Hualfin shows that brittle processes of faulting, cataclasis and fracture foliation help the basement attain a folded form. Pervasive and continuous joint fractures, and an unconformity-parallel fracture foliation at the surface, set up a condition for "flow" of granitic materials. Additionally, in order for basement to fold, the tip of the underlying fault must be located within the basement before it begins propagating towards the surface. Using the knowledge gained from the detailed structural studies, two regional cross sections were constructed in the region of Sierra de Hualfin, showing spatial and geometric relations between the adjacent uplifts, and the thrust systems of the eastern Puna Plateau. The cross sections show detachment levels at 16 km and ∼27 km for uplifts in the northern Sierras Pampeanas. Thrust faults of the northern Sierras Pampeanas, and of the eastern edge of the Puna can be interpreted as part of the same east-directed thrust system, with intervening west-directed backthrust development. The combination of the modeling of Sierra de Hualfin and the regional cross sections with detachments at 16 to 27 km depth suggests that basement-cored uplifts can be formed by gently-dipping faults detaching in the middle crust and near the base of the crust.
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:
Davis, George H.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleBasement-cored uplift deformation in the northern Sierras Pampeanas: Three-dimensional uplift structure, basement deformation, and regional analysisen_US
dc.creatorElena García, Pilaren_US
dc.contributor.authorElena García, Pilaren_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 structure of basement-cored uplift mountains is fundamentally controlled by the geometry of the basement and the basement unconformity. In the Sierra de Hualfin, an uplift located in the Sierras Pampeanas of NW Argentina, the well-exposed basement unconformity displays along-strike structural variations. The Sierra de Hualfin is composed of a core of Ordovician granitoid overlain by and thrust over Tertiary sedimentary rocks. The range is uplifted by an east-directed thrust fault, creating a steep range-front on the east and a gently dipping backlimb on the west. In the central region, however, basement and cover rocks in the backlimb are folded. Cross sections across the uplift and a three-dimensional computer model show that the variations along strike are due to differences in the geometry of the underlying fault or faults that deform the basement unconformity. Analysis of the folded basement unconformity on the west side of Sierra de Hualfin shows that brittle processes of faulting, cataclasis and fracture foliation help the basement attain a folded form. Pervasive and continuous joint fractures, and an unconformity-parallel fracture foliation at the surface, set up a condition for "flow" of granitic materials. Additionally, in order for basement to fold, the tip of the underlying fault must be located within the basement before it begins propagating towards the surface. Using the knowledge gained from the detailed structural studies, two regional cross sections were constructed in the region of Sierra de Hualfin, showing spatial and geometric relations between the adjacent uplifts, and the thrust systems of the eastern Puna Plateau. The cross sections show detachment levels at 16 km and ∼27 km for uplifts in the northern Sierras Pampeanas. Thrust faults of the northern Sierras Pampeanas, and of the eastern edge of the Puna can be interpreted as part of the same east-directed thrust system, with intervening west-directed backthrust development. The combination of the modeling of Sierra de Hualfin and the regional cross sections with detachments at 16 to 27 km depth suggests that basement-cored uplifts can be formed by gently-dipping faults detaching in the middle crust and near the base of the crust.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.advisorDavis, George H.en_US
dc.identifier.proquest3016470en_US
dc.identifier.bibrecord.b41902592en_US
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