The first record of microforaminiferal linings from the early Pennsylvanian of Argentina is presented as consisting of Trochospiral Type I, Planospiral Type II and cf. Uniserial indet. (sensu Stancliffe) forms while associated with acritarchs, prasinophytes, freshwater algae, spores and pollen grains. Microforaminiferal linings and associated microflora were obtained from the well core YCF.CO3 borehole (interval of 850–851.5 metres below drill floor), which comprises the lower part of the Ordóñez Formation (Chacoparaná Basin). This association documents the development of estuarine or shallow marine environments in the western part of the basin during the Pennsylvanian (Bashkirian?). The origin of these environments was associated with the final phases (transgressions) of the Carboniferous glaciation of Gondwana, documented in the diamictites of the Ordóñez Formation.