the archaeological record of the north coast of santa cruz (argentine patagonia) is characterized by the presence of large quantities of accumulations of mollusc shells from anthropogenic sources, commonly known as shellmiddens. these have been interpreted as evidence of intense occupation by human populations during the middle and, mainly, late holocene. previous studies have analyzed the variability of surface shellmiddens in the study area. in this paper we analyze the structural characteristics of seven archaeomalacological accumulations excavated in three archaeological localities in different areas of this vast coastline. using geoarchaeological variables and the study of malacological remains we discuss the formation processes and postdepositacional alterations of these deposits in order to advance the discussion of the exploitation, consumption and disposal of shellfish by patagonian populations in the past.