Gravity collapse structures in the Central Precordillera fold-andthrust belt, Argentina

HORACIO N. VARGAS; YANINA ESPER ANGILLIERI; LUIS MARTIN ROTHIS; LAURA P. PERUCCA; CARLA TAPIA; HORACIO N. VARGAS; YANINA ESPER ANGILLIERI; LUIS MARTIN ROTHIS; LAURA P. PERUCCA; CARLA TAPIA

JOURNAL OF IBERIAN GEOLOGY

SERVICIO PUBLICACIONES

Lugar: Madrid; Año: 2016 vol. 42 p. 151 - 160

1698-6180

AbstractSeveral landforms found in the fold-and-thrust belt area of the Andean Central Precordillera of Argentina, which were often associatedwith tectonic shortening, are in fact related to superficial gravity tectonic structures. These gravitational collapse structures have developedin the western flank of sierras de La Dehesa and Talacasto. These include rock-slides, rock falls, wrinkle folds, slip sheets and flaps, amongothers; which together constitute a monoclinal fold dipping between 30º and 60º to the west. Gravity collapse structures are parallel to theregional strike of the sierras de la Dehesa and Talacasto are placed in Ordovician limestones and dolomites. Their sloping towards the west,the presence of bed planes, fractures and joints; and the lithology (limestone interbedded with incompetent argillaceous layers) would havefavored their occurrence. Detachment and initial transport of gravity collapse structures and rockslides in the western flank of the Sierra dela Dehesa were tightly controlled by three structural elements: 1) the bedding, when It is dipping >30° in the slope direction; 2) joint setsthat constitute lateral and transverse traction cracks which release extensional stresses; and 3) discontinuities fragmenting sliding surfaces.Some other factors that could be characterized as local (lithology, structure and topography) and as regional (high seismic activity andpossibly wetter conditions during the postglacial period) were determinant in favoring the steady loss of the western mountain side in theeasternmost foothills of the Central Precordillera.