TRACING THE VOLCANIC AND TECTONIC EFFECTS OF THE MIOCENE ANDEAN STAGE ALONG THE PATAGONIAN RETROARC: AN EXAMPLE OF THE RÍO NEGRO SYSTEM, ARGENTINA

D'ELIA, LEANDRO; GARCÍA, MICAELA; FRANZESE, JUAN R.; BILMES, ANDRÉS; BUCHER, JOAQUÍN; LÓPEZ, MANUEL; FEO, RODRIGO

Hamburgo

Congreso; 25th Latin-American Colloquium of Geoscience; 2019

The Río Negro River system constitutes a drainage network located at the North Patagonian Region (45°S) that connected the Andes with the Atlantic Ocean through more than 600 km long. This corridor is one of the systems that control the transference of materials to submarine shelf, up to sink position, in the Argentina basin. During the Neogene this system was configured in a scenario of profuse arc-explosive volcanism, contractional tilt-block tectonics, the development of the orogenic rain shadow, as well as relative sea level changes. Several fault-bounded exoreic?closed-basins along the retroarc present infill that record endogenous and superficial processes occurred during the birth of the Andean chain, at this latitude, as we observe it today. Even though time-spatial large scale stratigraphic units and holistic geological models were performed to go forward in the understanding of the system, until now are absent high resolution tectonic-volcano-climatic-eustatic models that allow to understand the sediment supply/accommodation space relationship and the reciprocal stratigraphical effects along the whole system, in which the propagation of the environmental signals be consider. Based on a multidisciplinary approach, which includes structural, stratigraphic, geomorphological and geochronological dataset together with previous surface and subsurface regional surveys, the analysis retroarc basin along Río Negro system is carrying out. The preliminary results indicate that many contractional phases related to out of sequence, thick-skinned tectonics, progressed under explosive volcanism which affected in different form the system, according to the frequency order measured and location along the system. At the foot of the Andes, preliminary geochronological and magnetostratigraphic analysis reveals that the main infill of the basins has a maximum depositional time process of 128 Ky related to PDC as well as resedimentated volcaniclastic materials, whereas along the system their show changes in the infill patterns and in the transference systems occurred during middle-upper Miocene. These changes are recorded together with huge climate change related to the uplift and exhumation of the Andes, connection/disconnection of the system with shelf and sea level variations. Future works will aim to the understanding how the subtle interplaying of tectonic-volcano-climatic-eustatic forcing controls determine the reciprocal stratigraphy and its propagation effects from the Andes to the Atlantic sea.