José L. Lagos

By José L. Lagos and Ana M. Combina

During the Miocene, in the distal sectors of the Bermejo Basin, a complex relationship developed between a floodplain and contemporary volcanic activity. Seven stages of sedimentation are established to interpret this paleoenvironmental relationship. Stage I corresponds to the development of the floodplain previous to pyroclastic activity; in Stage II, pyroclastic activity is manifested by fall deposits and dry pyroclastic surges. A probable calm in the volcanic activity, associated with exceptional rains, generates laharic deposits (Stage III). Stage IV is dry pyroclastic surges that collapse the floodplain. Subsequently, the river system is reestablished (Stage V) under a regime of low to null volcanic activity. During Stages VI and VII, thick deposits of dry and wet pyroclastic surges, which have records of contemporary seismic activity. The presence of deformational structures within the pyroclastic deposits and lahars indicate that the volcanic centers were in distant areas. The volcanism that generated these deposits is probably associated with the migration to the east of the Miocene volcanic arc of the Cordillera de Los Andes or could be associate with the volcanism of the Sierra de Famatina.

Part of the book: Progress in Volcanology