M. Isabel Prudêncio

RAW MATERIAL SOURCES FOR THE ROMAN BRACARENSE CERAMICS (NW IBERIAN PENINSULA)

The Bracarense ceramics are characterized by a fine, pale yellow paste covered with a brownish yellow slip. The name is derived from Bracara Augusta, the Roman town located in the north of Portugal, where this type of ceramic paste was first found and identified. Various forms with the same type of paste occur, such as imitations of sigillata, terra sigillata and thin walls from the Augustus-Tiberius period, and common ware. Later, similar ceramics were also found in other archeological sites, e.g. Aquis Querquennis (Galiza, Spain), which question the location of the production center of this type of ceramic paste.Mineralogical and chemical analyses showed that the majority of the Bracarense shards studied differ from the common ware of the Braga region. Despite minor differences, the Bracarense shards collected in Aquis Querquennis have the same geochemical pattern as those found in Bracara Augusta, i.e. they appear to have been manufactured with the same clay type. The firing products found indicate a kaolin character of the source clay, and point to firing temperatures near 900°C. The Aquis Querquennis shards have greater Br contents, which can be explained by use-wear and/or post-depositional processes, as this site is located in a thermal-water region.

UPPER CRETACEOUS CLAYEY LEVELS FROM WESTERN PORTUGAL (AVEIRO AND TAVEIRO REGIONS): CLAY MINERAL AND TRACE-ELEMENT DISTRIBUTION

Clay-rich deposits of Upper Cretaceous levels in the Taveiro (Reveles and S. Pedro) and Aveiro (Bustos) regions of west-central Portugal are economically and environmentally important, but detailed chemical and mineralogical characterization is lacking. The purpose of this study was to partially fill that gap by correlating the trace-element geochemistry (particularly the rare earth elements, REE) with the mineralogy of both the whole rock and of the <2 μm fraction along selected stratigraphic levels of the formations. The results will help the ceramics industry in the region and will be important in paleoreconstruction environmental studies.Mineralogical and chemical characterizations were carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), and instrumental neutron activation analysis (INAA). The following clay-mineral associations were identified: (1) at Reveles — smectite, illite, and kaolin minerals; (2) at S. Pedro — kaolin minerals and illite; and (3) at Bustos — illite, kaolin minerals, and mixed-layer illite-smectite. The distribution of trace elements in the <2 μm fraction depended on the clay mineralogy, suggesting that the trace elements were incorporated in, adsorbed to, or even replaced major elements in the clays, as follows: (1) first-row transition elements, particularly Zn and Ga, were enriched when smectite predominated; (2) As, Rb, and Cs were enriched in this fraction of the S. Pedro deposit, the only one with Fe (oxyhydr)oxides and a high proportion of illite; and (3) REE were more concentrated when kaolin minerals predominated. Eu was enriched in the <2 μm fraction, which was due to preferential incorporation in the Fe (oxyhydr)oxides and/or carbonates.

A micro-invasive approach using INAA for new insights into Palaeolithic flint archaeological artefacts

Instrumental neutron activation analysis of small flakes from the same flint fragment of archeological artefacts from Palaeolithic sites (“Abrigo de la Quebrada”, “Cova de les Cendres” and “Cova Negra”), and geological sources (Chelva, Valencia, and Alcoi, Alicante) from the eastern Spain, was performed. The chemical contents of 27 elements were obtained. Ga, Ce, Nd, Yb, Zr and Hf were discarded due to high variations within the same fragment. The identification of chemical fingerprints within heterogeneous flint fragments was able to differentiate flint types and variants (“Domeño” and “Serreta”), contributing to provenance and human mobility in ancient times.

Imprints of the 1755 tsunami in the Tróia Peninsula shoreline, Portugal

ABSTRACT Rebêlo, L., Costas, S., Brito, P., Ferraz, M., Prudêncio, M. I. and Burbidge, C., 2013. Imprints of the 1755 tsunami in the Tróia Peninsula shoreline, Portugal A large earthquake shook the offshore region of Portugal in November 1st 1755 with an estimated magnitude of 8.5±0.3 in the Richter scale. It lead to the massive destruction of the city of Lisbon, which was followed by intense fires. Although most of the detailed consequences of the earthquake and tsunami focused in Lisbon, the effect of tsunami destruction was also reported in other locations along the Peninsula coasts and Morocco. At Setúbal, located 30 km to the south of Lisbon in the Sado estuary, evidences of inundation were also documented, reporting wave heights that reached a first floor height. Despite the magnitude of the inundation in the interior of the estuary, there has not been reported any evidence of the impact of this event on the estuarine shorelines. In order to understand the consequences of such a wave on the sandy shores of the region, we explore the inlet shoreline and seaward exposed region of the estuary, the Tróia peninsula. To do so, we integrate multiple types of data and information: dune ridge position were extracted from aerial photographs, shorelines from the historical maps, shoreline progradation rates, Ground Penetrating Radar profiles and optically stimulated dating of barrier sediments. This information allows us to reconstruct the shoreline following the tsunami, documenting a greater impact towards the inlet where the water flow concentrate as it entered the estuary. The impact of the tsunami in Tróia peninsula translates on the erosion of about 1000 years of barrier deposits within the spit end.