This paper reports results of the application of combined refraction and geoelectric geophysical methods to the study of the El Paso rock glacier in the arid Andes of Argentina. The data allow inferences to be made upon the internal structure, and permafrost thickness of the rock glacier. The El Paso rock glacier is located in the arid to hyper‐arid Agua Negra basin. Due to its altitude, it records some of the world's highest global radiation. The active layer thickness was studied using refraction seismic methods. Seasonal monitoring of this layer showed large variations in thickness, being thicker in summer and thinner in winter. Geoelectric methods allowed detection of a wet layer underlying permafrost, thereby providing information about the character of the rock‐glacier base. The maximum inferred thickness of El Paso permafrost was 18.5 m. Three main layers were detected: an upper deposit of dry debris over a debris‐water layer, a debris‐ice‐mixture (i.e. permafrost), and a lower one composed of wet debris. The geophysical results permit a first estimate of the volume of water (6.3 hm3) enclosed in the rock glaciers of this region, indicating that locally, rock glaciers are important water resources. However the incidence of water availability to the arid lowlands is unknown. Copyright © 2002 John Wiley & Sons, Ltd.

ABSTRACT. We present a gravimetric study on the northeast edge of the North Patagonian massif in the province of Rio Negro, to ascertain the depth distribution of the different outcrop units in the study area, as well as the geometry of the Navarrete Plutonic Complex. The negative anomalies in the Bouguer residual map reproduce the lateral density contrast between what would be the bedrock of Cambrian age and the lithologic units of the Mesozoic age. The solutions of the analytical signal along with variations in the curve of the horizontal gradient of gravity, obtained along a profile across the outcrops of the Navarrete Plutonic Complex, show contacts between the intrusive body and the bedrock with different densities. Over this profile we obtained a 2D (dimensional) gravimetric forward model adjusted with the density data of the surface rocks. Above the outcrop of the Yaminué Complex there exists a gravimetric high which does not correspond to the density in this area. This is a new evidence that proves that it is a series of intrusions and thin subhorizontal tectonic slices and that its thickness is probably thin. On the other hand the Navarrete Pluton shows the greatest development in size and depth to the east of Treneta stream.Keywords: gravimetry, Navarrete Pluton, through, Yaminué Complex. RESUMEN.Se presenta un estudio gravimétrico en el borde noreste del macizo Norpatagónico provincia de Río Negro, con el objeto de conocer la distribución en profundidad de las distintas unidades aflorantes en elárea de estudio, como así también, la geometría del Complejo Plutónico Navarrete. Las anomalías negativas en el mapa residual de Bouguer reproducen el cambio lateral de densidad entre lo que sería el basamento de edad Cámbrica y las unidades litológicas de edad Mesozoica. Las soluciones de la señal analítica junto a las variaciones en la curva del gradiente horizontal de la gravedad, obtenidas a lo largo de un perfil transversal a los afloramientos del Complejo Plutónico Navarrete, evidencian contactos entre el cuerpo intrusivo y la roca de caja de diferente densidad. Sobre este perfil se obtiene un modelo de inversión gravimétrico 2D ajustado con datos de densidad de rocas en superficie. Sobre el afloramiento del Complejo Yaminué existe un máximo gravimétrico que no se corresponde con su densidad en superficie. Esto es una nueva evidencia de que el mismo es una serie de intrusiones y escamas tectónicas delgadas subhorizontales y que su espesor es probablemente de poca magnitud. Por otro lado el Plutón Navarrete muestra mayor desarrollo en su tamaño y profundidad hacia el este del arroyo Treneta.Palabras-clave: gravimetría, plutón Navarrete, profundidades, Complejo Yaminué.

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