INVESTIGADORES
GIMENEZ Mario Ernesto
congresos y reuniones científicas
Título:
Preliminary Geophysic Results In The Calingasta Bolson, Province Of San Juan, Argentina.
Autor/es:
MARTINEZ, M. PATRICIA; GIMENEZ, MARIO E; INTROCASO, ANTONIO.; RUÍZ, FANCISCO
Lugar:
Acapulco
Reunión:
Congreso; Eos Trans. AGU, 88/(23), Jt. Assem. Suppl.; 2007
Institución organizadora:
AGU
Resumen:
The
Calingasta bolson is situated between the Frontal Cordillera and the Andean
Precordillera from 31º to 32º south latitude and 69º 20 to 69º 45 West
longitude. Its average elevation is about 1600 m a.s.l.
The seismic
information indicates that the Eastern margin of this tectonic depression was
affected by convergence during the latest Tertiary and the Quaternary.
The
depositional Mesozoic sequences in this bolson lie on a strong angular
unconformity evidenced by a marked lithologic and structural change. These
deposits Triassic in age occur in remnants of continental half-grabens formed
by rifting that gave rise to NNW SSE trending basins with rapid subsidence (Kokogian and Mancilla, 1989; Kokogian et al., 1999). These rift
basins are coeval to the Triassic depocenters in the oil producing Cuyana basin
(Legarreta et al., 1992).
Contemporary
marine sedimentation is restricted to the Chilean territory, that is, to the
west of the Frontal Cordillera, where narrow troughs were opened to the NW as
marine embayments (Suárez and Bell, 1992).
In the Calingasta bolson, the
outcropping Triassic deposits were laid mainly in fluvial and lacustrine
environments and are exposed along the western flank of the Precordillera, as
observed at the latitude of the locality of Hilario, among other localities.
The bolson can be considered as a ramp basin formed between the Precodillera
and the Frontal Cordillera, limited by antithetic overthrusts controlled by the inversion of the
extensional faulting associated to the Triassic fill of the basin (Rossello et
al., 1996).
A new gravimetric survey carried
out in the Calingasta bolson area led to the generation of a recent gravimetric
chart, which was processed with different modern analytical and interpretation
techniques such as Analytic Signal, Tilt and its Gradient and Euler
Deconvolution.
The Bouguer anomaly chart was
filtered with the upward continuation at H= 40 km. The negative Bouguer
isoanomalies in the resulting residual anomaly chart describe the geometry of
the Calingasta bolson. Two outstanding depocenters with concentric isoanomalies
of -20 mGal were determined, one at the latitude of the Calingasta village and
the other situated to the SW of the locality of Barreal.
The depths arising from the solutions of the localized
Euler deconvolution, in the depocenters, reach 5000 meters.
The distribution of the solutions of the Euler
Deconvolution, as the responses of the Analytic Signal and Tilt Gradient,
indicate the presence of zones with NNW-SSE and NNE-SSW trends which segment
the bolson and separates both depocenters. This trends are interpreted as
produced by antithetic (or conjugated) faulting, which is in accordance to
seismic results.
References
Kokogian, D. A. and Mancilla, O., 1989. Análisis estratigráfico secuencial de la
cuenca cuyana. En Chebli G. y L.A. Spalletti (Eds.) Cuencas sedimentarias,
Serie Correlación Geológica 6: 169-202. Tucumán.
Kokogian, D. A.; Spalletti, L. A.;
Morel, E.; Artabe, A.; Martínez, R. N.; Alcober, O.A.; Milana, J. P.;
Zavattieri, A. M. and Papu, O.H., 1999. Los depósitos continentals triásicos.
En: Geología Argentina, Instituto de Geología y Recursos Minerales, Anales 29
(15): 377-398. Buenos Aires.
Legarreta, L.; Kokogian, D.A. and Dellapé, D. A.,1992.
Estructuración terciaria de la Cuenca Cuyana: ¿cuánto de inversión tectónica?
Revista de la Asociación Geológica Argentina, 47 (1): 83-86.
Suárez, M. and Bell, C. M. , 1992. Triassic rift-related sedimentary
basins in northern Chile (24°-29º S). Journal of South American Earth
Sciences, 6: 109-121.
Rossello, E.A.; López-Gamundí,
O.R. and Vaillard, C. L., 1996. Geometry of an Andean ramp basin: the Calingasta Valley, western Argentina. 30º International Geological Congress (Beijing), Abstract 2 ( 5-6-45): 318.