The aim of this study is to describe and interpret the paleoenvironmental history of the San Matías Gulf (SMG), in northern Patagonia, Argentina, which is associated with possible biotic and abiotic changes that occurred during the late Quaternary. In this regard, a taphonomic (disarticulation, right/ left valve ratio, fragmentation, abrasion, teeth preservation) and paleoecologic (alpha diversity, species abundance, life habit, substrate preference, feeding mode) analysis of Amiantis purputata (the target species) and its accompanying faunal remains (the non-target species) in modern, Holocene and Pleistocene shell assemblages, was performed. The general trend of the SMG throughout the late Quaternary was that of a low energy environment with varying water energy intensity depending on the study area. Additionally, each study site contains different substrates marked by patches of sand and rock which would have also determined the presence of certain species and, in turn, the proportion of sandy and rocky patches may have changed over time thus leading to the development of different local paleocommunities. Therefore, this gulf presents a dynamic mosaic of environments over time. Its waters would have been sufficiently rich in nutrients to allow the development of the filter feeding fauna which dominated the late Quaternary, especially A. purpurata. Crepidula species, which feed in two distinct ways (herbivore and filter feeding), increased in proportion throughout the Holocene. These changes, among others, coincided with the Last Glacial Maximum, the final configuration of the SMG, the Climatic Optimum of the Holocene and the impact of humans in the area.