Facies architecture and stratigraphic evolution of the Taquarembó Formation, North Basin - UY

This study’s main objective is the sedimentary and stratigraphic analysis of the Tacuarembó Formation (Upper Jurassic /Lower Cretaceous) through the faciological characterization, the reconstruction of the depositional... [ view full abstract ]

This study’s main objective is the sedimentary and stratigraphic analysis of the Tacuarembó Formation (Upper Jurassic /Lower Cretaceous) through the faciological characterization, the reconstruction of the depositional models, and the definition of the contact relations between the Batoví and Rivera members. Additionally, the present study aims to discuss the sedimentation controlling mechanisms, attempting to distinguish allociclic and autociclic factors in fluvial-aeolian systems. Starting from the survey of columnar profiles in a 1:50 scale, the elaboration of lateral sections from the confection of photomosaics and the collection of paleocurrent data, different facies associations were individualized. The Batoví Member is formed by facies associations of (1) aeolian dunes and interdunes and (2) fluvial channels. The Rivera Member, on the other hand, is essentially made of aeolian dunes facies associations. The frequent shift between aeolian and fluvial deposits generates cycles measuring up to approximately 5 meters, which genesis may be related to autociclic or allociclic mechanisms. Contrastingly, the Rivera Member was characterized by the successive aeolian dunes climbing, without the occurrence of wet or damp interdunes deposits, defining a dry aeolian system. The sudden change of depositional systems marked by a flat surface, occasionally containing clasts, points to the existence of an unconformity between the Batoví and Rivera members. Combined with those characteristics, the change in depositional models suggests a climatic variation, from an arid to semi-arid climate during the deposition of the Batoví Member, to a hyper arid climate context by the time the Rivera Member was being deposited. The aeolian dunes were covered by the basaltic lavas of the Arapey Formation, which allowed the preservation of their morphology.