Micromorphological perspectives on the stratigraphical excavation of shell middens: a first approximation from the ethnohistorical site Tunel VII, Tierra del Fuego (Argentina)

Due to their problematic stratigraphy, shell middens have traditionally been excavated by artificial stratigraphical cuts. This approach has often led to the obliteration of the original depositional sequence, removing important information regarding depositional and post-depositional processes, and human frequentation. Since the 1970s, an Argentinian team has been excavating archaeological shell middens in the Beagle Channel with a detailed stratigraphical approach, based on the excavation of actual depositional units (peeling), rather than artificial cuts. In the 1980s, Spanish archaeologists joined the Argentinean team and launched a series of new projects involving the excavation of ethnohistorical Yamana fisher-hunter-gatherer sites. The first excavated midden site was Tunel VII, from which two monolith columns of about 50 cm each (C11 and C12) that spanned the whole stratigraphy were extracted. The two columns were consolidated with resin, and two series of thin sections produced to corroborate stratigraphical observations made in the field, and to verify hypotheses related to the formation of archaeological shell midden sites. We present here the first results obtained from the microscopical observation of seven thin sections from column 11 (West column), extracted from a portion of the profile originally described as corresponding to the hut entrance and associated floor. The observation of microscopical features invisible in the field has provided supplemental information about the depositional and post-depositional processes affecting shell midden sites. We have also preliminarily defined a number of micromorphological characteristics identifying human activities such as discrete shell deposition events, phases of preparation of the hut floor, and compression by repeated trampling. Finally, we have explored the possibility of establishing some guidelines to characterise the length and character of frequentation phases of the site previous to its final abandonment at the beginning of the 20th century.