António M. Monge Soares

COASTAL UPWELLING AND RADIOCARBON—EVIDENCE FOR TEMPORAL FLUCTUATIONS IN OCEAN RESERVOIR EFFECT OFF PORTUGAL DURING THE HOLOCENE

This paper focuses on the use of the radiocarbon content of marine shells collected along the Portuguese coast as a proxy for the intensity of coastal upwelling off of Portugal. Differences in the 14C ages of closely associated marine mol- lusk shells and terrestrial material (charcoal or bones) from several Portuguese archaeological contexts seem to be significant throughout the Holocene. ∆R values range from 940 ± 50 to -160 ± 40 14C yr. Five of these values are significantly higher than the modern value (250 ± 25 14C yr), while the remaining values are lower. The modern value was calculated by measuring the 14C content of live-collected, pre-bomb marine mollusk shells. This value is in accordance with an active upwelling of strong intensity that currently occurs off of Portugal. Some primary observations based on data presented here can be made: i) during the Holocene important changes have occurred in the ocean reservoir effect off the Portuguese coast; ii) these fluctuations may be correlated with regional oceanographic changes, namely with changes in the strength of coastal upwelling; and iii) these changes suggest some sort of variability of the climatic factors forcing coastal upwelling off of Portugal.

Reservoir Effect of Coastal Waters off Western and Northwestern Galicia

Differences in the radiocarbon ages of closely associated marine mollusk shells and terrestrial material(charred wood or bones) from several Galician archaeological contexts are significant from the Iron Age to Medieval times. Δ R values show high variability, ranging from 280 70 to 270 40 14C yr. The set of Δ R values also presents a strong positive peak ( Δ R = 270 40 14C yr) at 860 90 BP, which matches another peak found for western Portuguese coastal waters. The data obtained, namely the negative or close to zero Δ R values, suggest that the reduced offset between atmospheric and surface water 14C content is due to the existence of a strong stratification of the water column and environmental factors in the Galician ras during the Iron Age and the Medieval period.

Marine Radiocarbon Reservoir Effect in Late Pleistocene and Early Holocene Coastal Waters off Northern Iberia

Radiocarbon dating of closely associated marine mollusk shells and terrestrial material (mammal bones or charred wood) collected from archaeological contexts in northern Atlantic Iberian coastal areas is used to quantify the marine 14C reservoir effect (ΔR) for the coastal waters off the Cantabrian coast (northern Iberia). For the first time, ΔR values were reliably determined for these coastal waters, and also for the first time a ΔR was calculated for the Late Pleistocene in Atlantic Iberia. Pairs of coeval samples of different carbon reservoirs selected from Upper Paleolithic (Late Pleistocene) and Mesolithic (Early Holocene) contexts yielded ΔR weighted mean values of −117±70 14C yr and −105±21 14C yr, respectively. These values show oceanographic conditions characterized by a reduced offset between atmospheric and surface water 14C contents, suggesting a nonexistent or a very weak upwelling and some stratification of the water column. Similar oceanographic conditions have been recorded in other areas of Atlantic Iberia during the Holocene, such as off Andalusian and northwestern Galician coasts. Results not only provide useful information on environmental conditions but also a framework to obtain more precise and reliable absolute chronologies for the Late Pleistocene and Early Holocene in northern Iberia.

Microstructural Signatures of Bronze Archaeological Artifacts from the Southwestern Iberian Peninsula

This study concerns the elemental and microstructural characterization of proto-historic bronze rings from the southwestern Iberian Peninsula. Micro-EDXRF analyses demonstrate that the artifacts are binary bronze alloys (8–13% Sn) with arsenic and lead as the major impurities. Optical microscopy and SEM-EDS allowed the identification of common inclusions (e.g. copper sulphides) and alteration processes (redeposited copper, intergranular and intragranular corrosion). Microstructures consisting of fine dendrites, coarse and/or equiaxial grains were also identified, as well as the presence of (+) eutectoid, deformed inclusions, twinned grains and/or slip bands. The combination of these characteristics allowed establishing the metallurgical procedures (casting, forging and annealing) used in the production of the bronze rings. The identification of different thermomechanical operational sequences indicates that the metallurgical knowledge was well established in the southwestern Iberian Peninsula during those ancient times.

The ITRAX core scanner, a useful tool to distinguish anthropic vs. climatic influences in lagoon of Aveiro (N Portugal)

ABSTRACT Martins, V. A., Dias, J. A., Bernardes, C., Rubio, B., Bernabeu, A., , Rey, D., Soares, A.M., Sobrinho, F., Laut, L.M., Frontalini, F., Terroso, D., Miranda, P., Fernández-Fernández. S., Rodrigues, M.A., Figueira, R., Sousa, S.M., Amaral, P. Mahiques, M. and Rocha, F., 2013. The ITRAX core scanner, an useful tool to distinguish anthropic vs climatic influences in lagoon of Aveiro (N Portugal). The main goal of this work is to distinguish anthropic and climatic influences in sediments from the lagoon of Aveiro (Portugal). This study is based on a core (240-cm long) collected in Murtosa Channel. Optical and X-radiographic images and high-resolution elemental profiles were acquired with ITRAX micro-X-ray fluorescence (XRF) core scanner. Samples collected at each ≈3 cm along the core were analysed for grain size and total organic carbon. Furthermore, the fine fraction of selected layers was subjected to geochemical analysis by ICP-MS, after total acid digestion of the sediments, and mineralogical analysis, by XRD techniques. A radiocarbon age was determined by AMS, using molluscs shells collected at a depth of 90 cm. Sediments along the core are composed by fine and medium sand, with several mud layers. Sediments composing the first 100-cm may have been deposited after 1950, as it is indicated by the radiocarbon data, the increasing trend of Zn/Al, Pb/Al and Cu/Al and total concentrations of Zn, Pb, Cu, V, Cr, As and Ni in this interval that therefore might be linked with industrial activities of Chemical Complex of Estarreja. The progressive increase of Si/Al, Cl/Al, Rb/Al, K/Al and Br/Al and reduced Al concentrations, from the base to the top of this core, are interpreted as being related to higher marine influence and greater differences in tidal currents with longer exposition to air of the sediments with the consequent formation of brines favouring minerals precipitation in the area (e.g. anhydrite). These results seem to be a consequence of several works developed over time like: i) dredging to improve the navigation access to the harbour, located in the external sector of the lagoon; ii) the control of the course of some rivers influencing the supply of sediments. The tendency of sea level rise may have also emphasized the gradual increase of marine influence in this area. Fine-grained sections, related to an increase in Al, phyllosilicates, organic matter, pyrite and siderite contents would be attributed to phases of greater supply of fine-sediments during heavy rainfall events by the nearby Antuã river and other streams during negative phases of North Atlantic Oscillation. Higher deposition of organic matter enhanced diagenetic changes with pyrite and siderite formation. In the bottom of the core another record of pollution was unveiled to mining activities at the beginning of 20th century.

Effects of Long-Term Aging in Arsenical Copper Alloys.

Archaeological materials present unique records on natural processes allowing the study of long-term material behaviors such as structural modifications and degradation mechanisms. The present work is focused on the chemical and microstructural characterization of four prehistoric arsenical copper artifacts. These artifacts were characterized by micro-energy dispersive X-ray fluorescence spectrometry, optical microscopy, scanning electron microscopy with X-ray microanalysis, micro-X-ray diffraction and synchrotron radiation micro-X-ray diffraction. Cu3As is the expected intermetallic arsenide in arsenical copper alloys, reported in the literature as exhibiting a hexagonal crystallographic structure. However, a cubic Cu3As phase was identified by X-ray diffraction in all of our analyzed archaeological artifacts, while the hexagonal Cu3As phase was clearly identified only in the artifact with higher arsenic content. Occurrence of the cubic arsenide in these particular objects, suggests that it was precipitated due to long-term aging at room temperature, which points to the need of a redefinition of the Cu-As equilibrium phase constitution. These results highlight the importance of understanding the impact of structural aging for the assessment of original properties of archaeological arsenical copper artifacts, such as hardness or color.

Metallurgical production from the Chalcolithic settlement of Moita da Ladra, Portugal

ABSTRACT The Chalcolithic site of Moita da Ladra, on the right bank of the River Tagus, near Vila Franca de Xira (Portugal), was mainly settled during the second half of the 3rd millennium BC. The large amount of metal artifacts and metallurgical remains recovered at the site indicates local metallurgical activities. Chemical and microstructural characterization of 62 copper-based artifacts and 8 metallic nodules from the settlement are presented. Micro-EDXRF, optical microscopy, SEM-EDS and Vickers microhardness testing were applied in this research. Elemental determinations show artifacts containing variable amounts of arsenic. Forty-five percent of the artifacts have an arsenic content at impurity level (As < 2 wt.%), while the remaining items range from 2.0 wt.% to 5.4 wt.% As. Microstructural analysis shows that artifacts were shaped by hammering and annealing cycles, being 33% of the artifacts finished by cold working. Metallic nodules were produced by smelting operations, and are chemically consistent with the analysed artifact collection. Results are compared with those obtained by similar researches carried out on important contemporary materials from the same geographical area (Portuguese Estremadura) and other Iberian regions (Southern Portugal and Western Andalusia).

Manufacture of copper weapons and tools from the chalcolithic settlement of São Pedro (Portugal)

ABSTRACT A collection of 30 copper-based artefacts recovered during archeological excavations at the São Pedro settlement (Redondo, Portugal) was characterized by optical microscopy and Vickers microhardness testing. The radiocarbon dating of bone samples and the existence of Bell Beaker ceramics establish a chronology of c. 2700–2000 BC for tools and weapons made of copper with varying arsenic contents. The manufacture included one or more cycles of forging and annealing, while final work hardening was uncommon. The collection shows a wide range of hardness (52–142 HV0.2) without any correlation with typology or arsenic content, suggesting unawareness of the hardening potential of this alloying element. Technological features of São Pedro artefacts were compared with those of coeval metallurgies from neighboring regions (Portuguese Estremadura and Southern Andalusia) revealing common and distinctive characteristics that help to understand the use of arsenical copper alloys among communities of the third millennium BC.

Holocene palaeoenvironmental evolution of Saltés Island (Tinto and Odiel estuary, SW Spain) during the Roman period (1st century BC–5th century AD)

A multidisciplinary analysis of Holocene sediments from Saltés Island (Tinto-Odiel estuary, SW Spain) has allowed to differentiate eigth sedimentary facies, according to their textural characteristics, internal structure, paleontology and archaeological content. Its interpretation and the chronological datings carried out reconstruct a transition from a sandy tidal plain to a final occupation by a Roman salting (cetaria) between the 1st century BC to 5th century A. This evolution includes the deposit of washover fans derived from high-energy events between the 1st century BC to 3th century AD. The integration of these new data with others from previous research has allowed partially complete the palaeoenviromental reconstruction of the marine domain of the Tinto-Odiel estuary.ResumenEl análisis multidisciplinar de sedimentos holocenos procedentes de la isla Saltés, situada en el estuario de los ríos Tinto y Odiel (SO de España), ha permitido diferenciar ocho facies sedimentarias, de acuerdo a sus características texturales, estructura interna, contenido paleontológico y restos arqueológicos presentes. Su interpretación y las dataciones cronológicas efectuadas han permitido reconstruir una transición desde una llanura mareal arenosa a la ocupación final de la zona por una factoría romana de salazones (cetaria) entre los siglos I BC y V AD. Esta evolución incluye el depósito de washover fans derivados de la acción de eventos de alta energía entre los siglos I BC y III AD. La integración de estos nuevos datos con otros procedentes de investigaciones previas ha permitido completar parcialmente la reconstrucción paleoambiental del dominio marino del estuario de los ríos Tinto y Odiel.

A cronologia relativa e absoluta da ocupação sidérica do Castelo de Castro Marim

A diacronia da ocupacao da Idade do Ferro do Castelo de Castro Marim foi estabelecida tendo em consideracao a sequencia estratigrafica observada e, naturalmente, os espolios recolhidos nessa mesma sequencia. Com base nesses dados, foram ja apresentadas propostas de atribuicao cronologica as quatro fases de ocupacao siderica que pudemos caracterizar tambem relativamente aos espolios e a arquitectura. A recolha de material orgânico em todos os niveis da sequencia estratigrafica permitiu obter datacoes absolutas, efectuadas sobre carvoes e faunas malacologicas. Neste trabalho, os dados da cronologia de radiocarbono obtidos sao apresentados, sendo cruzados e discutidos com os que os restantes elementos possibilitaram. A relacao entre as datacoes de 14C e as obtidas pela analise morfologica dos espolios recolhidos ao longo da sequencia estratigrafica permite estabelecer bases consideravelmente mais solidas para a evolucao diacronica da Idade do Ferro do Castelo de Castro Marim. In this work, the data from the radiocarbon chronology are presented and discussed by themselves and related with the others. The relationship between the 14C dates and those obtained by morphological analysis of the materials collected along the stratigraphic sequence bring more solid bases to analyze the diachronic evolution of Castro Marim Iron Age.