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Title: Unsteady deformation along the Southwest Spanish Pyrenean thrust front
Authors: Teletzke, Allison L.
Parés, Josep María
Parés, Josep María
Anastasio, David J.
Issue Date: 2011
Publisher: American Geophysical Union
Abstract: A history of unsteady fault slip is recorded by magnetic reversals in a section of Oligocene continental growth strata on the forelimb of the blind thrust Santo Domingo-Tafalla anticline. Progressive tilting during deposition of the fluvial-lacustrian mollase of the Campodarbe formation is related to slip on the foreland dipping backthrust. Tilt rates calculated with 0.15-.7 Ma resolution, constrained by the magnetostratigraphy, vary from 3°/myr to 45°/myr, indicating times of near quiescence alternating with more rapid deformation over the 5 myr history recorded in the section. The new magnetostratigraphy established in this study is further west than previous studies and provides new age control for late-stage deformation of the Pyrenean thrust front. A dense array of more than 500 samples from 164 horizons over the 3,300 m of growth section was used to develop the magnetostratigraphy. A progressive 15-step thermal demagnetization (150°-690°C) was used to determine the characteristic remanent magnetization (ChRM) by principal component analysis (PCA). The ChRM is primarily carried by magnetite and hematite, and goethite is also present in the samples. PCA and calculation of virtual geomagnetic poles determined normal and reversed polarities within the section that are correlated to the geomagnetic polarity timescale. Previous work in the Campodarbe Fm ~30 km to the east by Hogan and Burbank (1996) B. Oliva-Urcia (personal comm.) tie the base of the section to C12r, and preliminary results suggest the Campodarbe Fm extends into C8. The first 1,000 m of section is pregrowth. The onset of the progressive unconformity in the section records the onset of deformation at ~30.5 Ma. Initial deformation was rapid with 25° of dip change over 0.65 myr (38°/myr). The next 0.5 myr was nearly quiescent with only 2° of dip change (4°/myr). Subsequently deformation steadily increased to 15°/my before returning to rates near 35°/Ma. Thus, this study shows the range of fault growth unsteadiness, as well as new age controls for late-stage deformation of the Spanish Pyrenees.
Description: Ponencia presentada en: American Geophysical Union, Fall Meeting, 5-9 de diciembre 2011, San Francisco
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Type: Presentation
Appears in Collections:Congresos, encuentros científicos y estancias de investigación

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