Analyses of site formation processes in the Argentine Puna are uncommon and they are mainly devoted to answering taphonomic questions; understanding site formation processes is a prerequisite before inferring past human activity from the spatial distribution of the material remains recovered at any site. The main objective for this research (focusing on a high altitude marsh called "Vega de San Francisco" in the Puna region, located 21 km from the Argentina-Chile border) was to reconstruct the formation processes of the excavated units through the analysis of their sediments, providing the necessary information to discuss human occupation intensity as well as to examine site usage throughout the passage of time. The sediment analysis provided three research avenues: physical/chemical properties, microvertebrates and microfossils. A fourth avenue was explored by using information obtained through experimental control sites.