CONICET | Buscador de Institutos y Recursos Humanos

The Río Salí Formation (Choromoro Group, middle Miocene) consists of fine grainedclastic, carbonatic, and evaporitic beds that record sedimentation in a variety oflacustrine environments, mainly developed in intermountain valleys in the NorthwesternPampean Ranges of the Tucumán Province. The lower member of this unit, composedof fine-grained sandstones, mudstones, and limestones together with local occurrence ofstromatolites deposited in an open lacustrine setting, provides an opportunity todocument microbially induced wrinkle structures and explore their palaeoecologicalaffinities. These structures are preserved in sandstones and siltstones layers interbeddedwith limestones, occurring on the upper bedding planes or at the lower surfaces of thebeds. The study samples are characterized by the arrangement of linear to sinuouslycurved, frequently bifurcated ridges, usually 1 mm high and 2-1 mm wide, separated byparallel depressions and locally resembling small scale interference ripples. This patternis classified as typical Kinneyia wrinkle structure. The development of these structuresin the bedding planes is related to microbial activity, and its identification allowsunlocking palaeoenvironmental parameters that indicate microbial colonization in amoist substrate and quiet water conditions in subaqueous settings, probably associatedto littoral areas of ephemeral lakes. In addition, the recognition of microbialcolonization brings paleoecological information, particularly on the food web, given theparticipation of microbial communities in the primary productivity. Understanding thepaleoecological parameters that controlled the formation of these structures mayfacilitate exploration of other paleontological and biological signatures in ancient lakedeposits.