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Backbone of the Americas—Patagonia to Alaska, (3–7 April 2006)

Paper No. 29
Presentation Time: 10:35 AM-7:45 PM

TIMING AND STYLE OF DEFORMATION OF THE ANDES ABOVE THE NORMAL SUBDUCTION SEGMENT, 34º-35º S, SOUTHERN CENTRAL ANDES: COMPARISON WITH THE FLAT SLAB (32º-33º S) AND TRANSITION (33º-34º S) SEGMENTS


GIAMBIAGI, Laura B.1, BECHIS, Florencia1 and GARCÍA, Víctor H.2, (1)IANIGLA-CRICYT, CONICET, Parque San Martín s/n, Mendoza, 5500, Argentina, (2)LAMOGE, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, Buenos Aires, 1428, lgiambia@lab.cricyt.edu.ar

A new kinematic model, which integrates original structural data and new Ar/Ar dating with previous surface and subsurface data, is proposed for the Malargüe fold and thrust belt. This belt extends from 34º to 36º S and forms part of the Cordillera Principal above the normal subduction segment. It is characterised by an eastern sector of thin-skinned deformation and a western sector of thick-skinned deformation related to the inversion of a Triassic-Jurassic half-graben. Cross-cutting relationships, together with emplacement ages, indicate that the main phase of deformation and uplift of the Cordillera Principal occurred between 15 and 9 Ma. Uplift of the Cordillera Frontal began after deformation in the Cordillera Principal had started to wane (post 7 Ma).

The main phase of deformation in the normal subduction segment (15 - 9 Ma) correlates well with the main phase of deformation in the transitional segment (15 - 8.5 Ma). In the flat-slab segment, however, compressional deformation started around 21 - 22 Ma and the main phase of deformation has been constrained between 19 and 8.7 Ma. Although the onset of deformation seem to have migrated from north to south, around 22-21 Ma in the flat slab segment, 18-19 Ma in the transition zone and 16-15 Ma in the normal subduction segment, the waning of deformation started at the same time in all the segments around 9 to 8 Ma. Comparison of the timing of deformation of both Cordillera Principal and Cordillera Frontal in the flat-slab, transitional and normal segments and its relation with the reconstructed Juan Fernandez Ridge track indicates that deformation in the Cordillera Principal cannot be related to the shallow subduction. Instead, there is a good correlation in time between the arrival of the ridge (between 14 and 9 Ma) and the southward migration of deformation in the Cordillera Frontal.

Session No. 3--Booth# 62

T3. Shallowing and Steepening Subduction Zones I
Monday, 3 April 2006: 10:35 AM-7:45 PM
Geological Society of America Abstracts with Programs. Speciality Meeting No. 2, p.44
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