An archaeometric study of a Late Neolithic cup and coeval and Chalcolithic ceramic sherds found in the São Paulo Cave, Almada, Portugal

Abstract

A detailed archaeometric study of a Late Neolithic cup found in the São Paulo Cave, Almada, Portugal, has been made, which, according to its unique decorative characteristics, may have had a ceremonial and symbolic utilization. Other 23 sherds, collected around the cup, dated early and late Chalcolithic periods, have also been studied. The conjugation of the information provided by the Raman, X‐ray diffraction, and X‐ray fluorescence emission experiments for the locally collected cup, sherds, and clays, with emphasis on the analysis of the ceramic bodies, allowed the characterization of the artefacts. In the reddish, brownish, or black parts of the surface of the cup, haematite, magnetite, and carbon black pigments were identified, whereas in the whitish parts, quartz was the most common mineral. Three main groups could be identified in the ceramic bodies, although all were made with the use of locally collected clays. In the first group, where the Neolithic cup is included, the potters used Miocene clays, most probably from the Palença clay sources, which were fired at a high temperature of about 950°C. The second group was also produced with raw materials of Miocene origin but the firing temperature was much lower, around 800°C, as revealed by the existing amount of muscovite. The third group, with clays of a Pliocene origin, exhibited a much lower content of calcium carbonate, as evaluated by the R index ([SiO2 + Al2O3 + K2O]/CaO), considered as ceramic raw material or a geological source indicator. These clays contain high amounts of kaolinite, muscovite, quartz, microcline, and anatase.

Portuguese 16th to Early 18th Century tin Glazed Ceramics Found at the Tagus Estuary Saltpans

“…The Lisbon region presents two main different geological areas: one is located North of Tagus River, with Cretaceous, Paleogenic (basalt complex of Lisbon) and Neogenic (Miocene) formations [14,[16][17][18]. South of Tagus River also some Miocenic outcrops can be found.…”

“…However this second region is quite different from the first one, and corresponds to an area of Pliopleistocene deposits. It should be emphasized that in the Lisbon region, Miocene clays can be found North and South of Tagus River, while Pliocene clays only exist South of Tagus River [14,[16][17][18]. Further details on the geological context for the Lisbon ceramics can be found in references [16,17].…”

“…It should be emphasized that in the Lisbon region, Miocene clays can be found North and South of Tagus River, while Pliocene clays only exist South of Tagus River [14,[16][17][18]. Further details on the geological context for the Lisbon ceramics can be found in references [16,17]. Lisbon clay sources are traditionally grouped as West Lisbon and East Lisbon, for white or red clays respectively [14].…”

“…The XRD experiments, micro-Raman, and XRF spectroscopies and details regarding the firing procedures of the collected clays are described in previous publications of our group [10][11][12][13]16,17,22,23].…”

“…Type 2 ceramic pastes, shown in curve (ii) of Figure 4, evidence several major differences from Type 1, namely the presence of anorthite (An, CaOAl 2 O 3 (SiO 2 ) 2 ) and also of very large amounts of diopside, (D, CaMgSi 2 O 6 ), a calcium and magnesium silicate, in this way establishing a clear difference from Type 1 ceramics. The presence of diopside requires the existence of magnesium in the raw materials and also firing temperatures above ~850ºC [16,17,24]. Finally, the large amounts of anorthite shown in curve (ii) of Figure 4 are an evidence for very high firing temperatures in the kiln (above ~900ºC -950ºC) and also of long-lived firing [16,17,24].…”