During the course of the excavations of the San Quirce open-air archaeological site in Spain, an unusual negative structure was identified in the Holocene level dated ca. sixth millennium cal BC. A fire pit alongside a single post-hole and intense fire-burning activity was recorded. Yet, the most striking feature of the structure is the absence of any artifactual or faunal record associated to it, something without a known archaeological parallel. Its interpretation represents an archaeological challenge addressed through a multidisciplinary approach including geoarchaeological, palaeobotanical techniques and experimental archaeology. Fifteen stratigraphically distinguishable combustion events showing a diachronic fire record, the significant structure’s dimensions and particularly the post-hole, indicate its anthropic origin. Archaeomagnetic and micromorphological data allowed reconstructing and temporally sequencing some formation and post-depositional processes, some involving water flows. Maximum heating temperatures between 480 and 525 °C were determined in one of the combustion features studied. The identification of grassy tufts would suggest a seasonal settlement of the site. We cannot yield a definite explanation for the artifactual absence, but the available data and an experimental archaeology recreation suggest that the structure could be used as a small hut/open-air bivouac, over which short-lived occupations were repeatedly carried out.
