Stratigraphy and sedimentology of the terminal fan of Candeleros Formation (Neuquén group), Lower Cretaceous, Neuquén Basin, provinces of Neuquén and Mendoza, Argentina

Abstract

The Candeleros Formation is represented by a succession of deposits that represent terminal fans starting to fill a foreland basin (back-arc) during the Albian. The different sub-environments of the terminal fan suggest low gradients during the onset of deposition of the Río Limay Subgroup (Neuquén Group). The terminal fan system is represented by distributary zone (TF-DZ), distributary zone-base zone (TF-DZBZ) and base zone deposits (TF-BZ). Its most notable feature is the presence of bitumen in “pockets” and scattered in the sandstone channel fill and crevasse splays deposit. In this system the feeder zone of the terminal fan system has not been identified, however, the distribution of architectural elements and paleocurrent data allow us to infer that the catchment area of the backbone would have been located to the NNW/NW. Distributary zone deposits are characterized by thick deposits of low sinuosity channel, with a high degree of connectivity and strong vertical aggradation of channel belts. Deposits of distributary zone-base zone are characterized by a higher density of channel deposits/distributary plain, but with belt channel less thick, longer laterally, greater width/thickness ratio and connectivity in the braided deposits. The distal parts of the terminal fan are well represented and vary only in the channelized deposits and mantle/floodplain ratio, which is abruptly reduced towards the flood basin connection. The importance of Candeleros Formation deposits is that they are remnants of accommodation that preserved the original architecture and represent exhumed reservoirs.