LATE CRETACEOUS EARLY TERTIARY SEDIMENTATION IN A SEMIARID FORELAND BASIN (NEUQUEN BASIN, WESTERN ARGENTINA)

A Late Cretaceous transgression and a subsequent Paleocene regression is recorded in the Neuquén Basin of western Argentina in the sediments of the Upper Malargüe Group. Seven facies associations (D through J) representing different depositional subenvironments have been recognized in the younger depositional sequence. Facies association E, green calcareous mudstones, was deposited in the outer shelf. Facies association F, bioclastic carbonates, represents inner-shelf deposits to littoral sediments. Facies association G, sandy calcarenites, corresponds to nearshore to coastal deposits. Facies association H, oolitic calcarenites, and facies association D, evaporites, composed a shallowing upward carbonate sequence. Facies association I, cross-bedded lithic sandstones, and facies association J, red mudstones, are characterized as meandering fluvial deposits. The lateral and vertical distribution of facies association changes from north to south in the basin, according to several depositional controls. The foreland setting of the Neuquén Basin at this time, with different sediment input and paleoslopes on the retro-arc vs. the cratonic side of the basin, influenced sedimentation. Basin embayment geometry caused differences in tidal regime, which in turn affected depositional environments. Westerly winds generated clockwise tidal currents inside the basin, which affected alongshore lateral facies association variation. The semi-arid climate favoured deposition of mixed carbonate-siliciclastic lithologies and evaporites. © 1990.