Cleia Detry

The Emergence of Muge Mesolithic Shell Middens in Central Portugal and the 8200 cal yr BP Cold Event

ABSTRACT The emergence of Portugals Muge Mesolithic, with its characteristic shell middens and human burials, is widely seen as a response to the formation of a highly diverse terrestrial and aquatic ecotone in the Tagus basin by the Flandrian transgression. Recently, some have suggested that this was an adaptive response to the 8200 cal yr BP event. Using the available radiocarbon data for the shell middens, paleoclimatic data, and paleoceanographic data we present a new model for the appearance of the Muge Mesolithic shell middens and changes in settlement between the Boreal and Atlantic phases for central Portugal. Coastal ecosystems were altered due to diminution in upwelling and the occurrence of the 8.2 kyr cold event, with declining availability of marine resources, rapid sea level rise, and changes in coastal morphology. The result was that the previous coastal setting was no longer suitable for the hunter-gatherer-fishers causing a settlement shift to the new, large, and stable estuary of the Tagus Valley.

Changes in the exploitation dynamics of small terrestrial vertebrates and fish during the Pleistocene–Holocene transition in the SW Iberian Peninsula: A review

The Pleistocene–Holocene transition c. 11.5 ka cal. BP is associated with dramatic climatic changes. These events led to fundamental shifts in landscape and have, therefore, been seen as responsible for a major impact on the human ecological behavior of the last hunter–gatherers in the Western European territory. In the case of Iberian Peninsula, it is commonly assumed that these human ecological adaptations are reflected in the new settlement and subsistence patterns that characterized the Late Upper Paleolithic–Mesolithic transition. Following the argument, the main aim of this paper is to present the state-of-the-art and consider this theoretical model using zooarchaeological data of small terrestrial vertebrates and fish from SW Portugal. Archaeological data are reviewed and discussed in order to analyze the change in the exploitation of small game, birds, and aquatic resources during this period. In this paper, we reinforce the idea that in SW Iberia, subsistence intensification and diversification precede the transition itself and are more likely to be related to other long-term phenomena, cultural and/or demographical, than to the changes in settlement behavior. The state-of-the-art discussed here led to new research questions related to the role of small vertebrates on the changes in human subsistence behavior during the Pleistocene–Holocene from Western Iberia.

Mesolithic human occupation and seasonality: sclerochronology, δ18O isotope geochemistry, and diagenesis verification by Raman and LA-ICP-MS analysis of Argyrosomus regius (meagre) sagittae otoliths from layer 1 of Cabeço da Amoreira Mesolithic shell midden (Muge, Portugal)

We present preliminary sclerochronological analysis on 15 Argyrosomus regius (meagre) otoliths collected from two different human occupation levels from the Cabeço da Amoreira shell midden (Muge valley, Portugal). The otoliths were sectioned and observed under a reflected light stereomicroscope to examine seasonal growth rings. Carbonates collected from individual growth rings subsampled with a micromill sampling device were analyzed for their stable oxygen isotope content with the objective of determining the predominant season of capture and therefore season of site use, environmental conditions, and sites of resource procurement (local versus regional). The otoliths’ stable isotope records show clear seasonality and a season of capture estimate that seems consistent with a “good season” (warmer season, i.e., from spring to late summer/beginning of autumn in this area) site use in the last occupation layer (the great majority of otoliths are from layer 1), except for four samples giving heaver oxygen isotope (δ18O) values that suggest colder conditions and only one with markedly positive δ18O values. Potential effect of diagenesis on the otolith records was also assessed through coupled laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS) and by micro-X-Ray diffraction (μ-XRD). Results revealed the presence of only aragonite and no traces of calcite, providing no evidence of diagenesis that could significantly alter isotope results and lead to erroneous interpretations. The implications of these results are discussed and compared with data from other archeological sites, as well as data from micromorphology regarding continuity or interruption of site use and other faunal remains.