Exploring shell midden formation through tapho-chronometric tools: A case study from Beagle Channel, Argentina

Abstract

Time resolution of shell middens is normally addressed through estimation of shell accumulation rates, where calculations are based on radiocarbon analysis. Density values by volume or discard rates by time units are also normally estimated for comparative purposes. In this paper, we support the idea that time has many measurable properties in archaeological deposits. These can be used as tapho-chronometric tools (e.g., bone weathering, shell fragmentation, soil formation, etc.) to identify differential time-averaging in shell midden formation, and to evaluate their archaeological implications regarding the material record. One site in the Beagle Channel, Argentina, was chosen to (a) demonstrate how different processes that interact in shell midden formation can provide information on temporal resolution and (b) discuss the implications of the time-averaged properties of shell middens for different analytical approaches and methodological pathways. Results show that several factors involved in the formation of mounds should be addressed prior to advancing interpretations about different behavioral aspects of the past: a) shell deposits do not necessarily represent a gradual accumulation of waste; b) these middens can represent occupations of varied duration that are expressed independently of both the thickness of the deposit and the rate of accumulation of the material; c) the formation of shell middens includes the actions of several cultural and natural processes that occur over variable time spans; d) re-occupations modify the shell deposits produced by previous occupations in the same location. Finally, we argue that to explore shell middens as time-averaged records helps to clarify distinctive aspects of mound formation, which in turn have significant effects on archaeological interpretations.