Sedimentary dynamics of the shallow water facies of Puncoviscana basin in the Neoproterozoic – Early Cambrian transition, NW Argentina

The Neoproterozoic-Early Cambrian deposits from NW Argentina conform the infilling of the Puncoviscana Basin. It represents an elongate, northward opened, foreland marine basin, developed between Amazonia, Antofalla and Pampia Terranes derived from the fragmentation of Rodinia. This basin registers sedimentation of basal diamictites and platform to deep marine deposits to the west, followed by cap carbonates that transitionally pass to shallow clastic sequences with few interlayered pyroclastites (Puncoviscana Formation). Shallow marine Puncoviscana Formation contains diagnostic sedimentary structures belonging to intertidal and shallow subtidal environments. Tidal processes are evident from lenticular to flaser stratification, soft-sediment deformation, tidal rhythmites, herringbones and double-crested ripples. Facies associations resemble shoreface environments along the west margin, which evolved to tidal flats laterally and upper sequence. The tides flooded over a mesotidal coast, while palaeocurrents’ analysis display bimodal bipolar and polymodal patters due to a reversal N-S flood and ebb circulation, and littoral drift. From published zircon ages’ population sourced to the Puncoviscana Formation we interpret that subsidence of the basin was episodic. The initial episode of active faulting and subsidence (~570-545 Ma, deposition of the lower Puncoviscana Formation) was followed by a ~10 Ma-episode of sea level rise (middle Puncoviscana Formation) and a final ~20 Ma-episode that included tectomagmatic activity that progressed to uplift and closure.