Lake patterns as related to neotectonics in subsiding basins: The example of the Ucamara Depression, Peru

Abstract

Two Northeast trending elongated lakes from the Andean foredeep (Ucamara Depression, south Maranon Basin) are analyzed in relation to basement structures, neotectonic and Scismotectonic data from the surrounding areas. Lake Puinahua (25 × 60 km) lies over pre-Cretaceous basement faults and Lake Punga (9 × 35 km), which subsided in a historical times, lies over a Paleozoic basement uplift. P axes from earthquake focal mechanisms located east and west of the Ucamara Depression are parallel to the lakes. The trend of lineaments, together will neotectonic data from the craton border, suggest that lakes develop along extensional faults. The western limit of the lakes are lie over folds from the front of the Sub-andean Zone. Comparison of elongated lakes from the Ucamara Depression with other lakes from the Andean foredeep suggests close relationships between lake pattern and geodynamics. Ria lakes are located along the front of the upper foothills and are possibly related to subsidence due to tectonic overloading of the sub-Andean border. Elongated lakes from the Ucamara Depression are situated in front of the wide, low foothills of the Sub-andean Thrust and Fault Belt. Subsidence is related to block faulting, and tectonic overloading is weak. These results are compared with previous studies of rectangular lakes from the Beni Basin, which appear to be related to the bending of the craton border. Analysis of lake pattern is suggested as a complementary approach for the neotectonic study of active subsiding areas.