Sequence Stratigraphy Of The Late Silurian - Devonian Subandean Basin In Southern Bolivia And Northern Argentina

Due to the recent discovery of several giant gas fields in the Subandean Basin in both Argentina and Bolivia, it has been noticed an increasing interest in detailing the stratigraphic setting of the Devonian reservoirs in these areas. Although extensive regional geological studies have been already performed in that area, they were carried out according to a lithostratigraphic approach. The absence of a suitable chronostratigraphic control was a major constraint for the understanding of the late silurian - Devonian paleogeography. The present work intends to apply a modern sequence stratigraphic approach on the late silurian - devonian section within the study area, in order to provide more reliable chronostratigraphic correlations between outcrop and well data. In this sense, selected outcrops were studied, regarding their palynological content, sedimentary facies and related processes, depositional systems and sequence stratigraphic elements. Well data, some of them related to recent gas discoveries, were also regionally integrated. The interpretation of outcrop and well data provided a suitable chronostratigraphic input for the recognition of sequence stratigraphic key elements and definition of 2nd and 3rd order sequences. More consistent regional correlations resulted from this new approach, including major devonian highstand and lowstand sand bodies, main reservoirs in the Subandean Basin gas fields.