Subsurface Quaternary stratigraphy of the lower Río Paraná basin.

Abstract

The study area is underground deposits in the lower basin of Paraná River (Paraná Delta area), from Diamante city in Entre Ríos province southward to the San Fernando city in the Buenos Aires province. The recent sedimentary deposits in this zone are directly related with the evolution of the environmental conditions throughout the Quaternary. This paper carries out based on a study well set and outcrops data set a analysis of the differents sedimentary agents, process and events that have intervened producing different geological data that exceeded to current deltaic deposits. We propose here, from the litologic study, clay minerals fraction, the C14 analysis and geologic outcrop a depositional model. This depositional model involves a transgressive regressive analysis of the different fluvial, estuaric and sea paleoenvironment prosseses occurred during the Holocene. In accordance with this geologic underground analysis we defined that the transgressive event throughout the Holocene has had more the one pulse of advance and regression. We propose an alternation of the estuaric environment and coast marginal environment which recurs according to the evolution of the advance and regression pulses of each event in the study area. Finally and with the analisys of data obtained sofor, it is not clear if the regressions of the sea level form the last great transgressive pulse occurred in only one stage, or if this stage it occurred with interruptions due to relative sea level increases of minor magnitude.