Holocene shortening in the transition between the Pampean Ranges and the Eastern Cordillera, Calchaquí valley (26°00?-25°50?lat, 66°00?-65°50?long), Argentina

LEONARDO ESCALANTE; SARA FIGUEROA; MANFRED R STRECKER; FERNANDO HONGN

Viena

Congreso; EGU General Assembly 2018; 2018

Despite its location in the orogen interior, the intermontane Calchaqui Valley (CV) in the transition between thereverse-faulted Eastern Cordillera and Sierras Pampeanas morphotectonic provinces of the NW Argentine Andesis characterized by active seismicity and hosts numerous geomorphic manifestations of sustained Quaternarytectonic activity. These include offset alluvial fans and pediments, and different generations of folded lacustrinesediments. These deposits are thus valuable tools for bridging the gap between historical/instrumental seismicitydata and deformation intervals that may span several millennia. As such, an analysis of these neotectonic featuresmay help to define intraplate fault recurrence and the assessment of the regional seismic potential.We studied this Quaternary fluvial-lacustrine and alluvial-fan sediments exposed on the E side of the eastern CV.The folded units are separated by angular unconformities which were used to separate them into eight differentstratigraphic units. The lacustrine units reflect repeated valley impoundments in the narrow Las Conchas east ofthe confluence between the Calchaquí and Santa María rivers.The youngest deformed lacustrine deposit (unit 7) is tentatively correlated with a paleolake existing between13.830±790 and 4810±500a (surface exposure ages on the landslide that generated the rockfall-dammed lake,Hermanns et al. 2004).The units 1 to 7 have all been affected by post-sedimentary deformation associated with fault-propagation foldsand thrusts. These deformed units were balanced using 2D Move to further quantify deformation in this region.Considering that the deformation that affected the youngest lacustrine deposits occurred