The missing sedimentological section linking the Neogene and quaternary of the Tandilia system and the Salado basin, Buenos Aires province, Argentina

Abstract

The Tandilia system and the Salado basin are two adjacent morphostructural units located within the Argentine Pampean plain, each exhibiting distinct and independent geological histories. The Tandilia system preserves outcrops of Argentina’s oldest Proterozoic rocks, while the sedimentary record of the Salado basin began during the Jurassic period. However, starting in the Cenozoic era, both units began to display common continental sedimentary fill characteristics. Despite this connection between the Tandilia system and the Salado basin, there is no unified lithostratigraphic framework for the Cenozoic that varies according to the studied localities. This study aims to define the stratigraphy of a sedimentary section that demonstrates the link between these morphostructural units from the Neogene onwards and to correlate it with the formal lithostratigraphic frameworks proposed in the literature. The analysis of well records led to the description of lithofacies and the establishment of facies associations, which were integrated to generate three correlation transects between the wells. Four facies associations were identified, three of which were fluvial and one aeolian. The analysis of these facies associations revealed that the sedimentary fill could be divided into two sedimentary sequences, lower sedimentary sequence and upper sedimentary sequence, separated by a sequence boundary marked by conglomeratic deposits. The definition of a stratigraphic framework for the middle section of the Del Azul creek basin and its correlation with the formal lithostratigraphic frameworks of the region indicate that from the Neogene onwards, both morphostructural units, the Tandilia system and the Salado basin, share sedimentological and tectonic characteristics. This study highlights the significance of subsurface information in understanding the geology of plain areas and its influence on regional geological evolution.