An investigation to establish the source of the Roman lime mortars used in Wallsend, UK

This paper presents the results of analytical work which aimed to explore potential sources for the lime mortar used in the Hadrianic fort baths and a third-century repair to Hadrian's Wall at Wallsend, UK. It is generally assumed that quick lime for mortar is produced close to the source, however, as yet, no archaeological evidence of kilns has been found in the Wallsend area. After extensive analysis the mortars were found to be very different in characteristics and suggest variable sources for the quarried limestone and for the aggregates used to manufacture the mortar. Precedence exists in other locations for quicklime to be sourced from kilns set at some considerable distance from Roman construction sites. It is only at Housesteads and Vindolanda, sited close to Carboniferous Limestone outcrops, that Roman lime kilns have been discovered to date. Therefore the investigation included a number of potential sources in the vicinity of Housesteads as well as Permian limestones at Trow Point which is geographically the closest source of limestone. Results suggest that Carboniferous limestone was the most likely source for some of the mortars analysed which may suggest that areas for lime production are less numerous than previously thought and may even have been concentrated around one area

Análisis mineralógico integrado (Qemscan y Drx) de lutitas negras: los depósitos tithonianos basales de la Formación Vaca Muerta (Cuenca Neuquina, Argentina)

Se estudia la composición por difracción de rayos X y QEMSCAN (19 muestras) de fangolitas y margas de la Formación Vaca Muerta, acumuladas durante la transgresión tithoniana de la Cuenca Neuquina. Se definen importantes variaciones composicionales entre tipos litológicos y facies sedimentarias. Las rocas del sector marginal de la cuenca muestran fuerte influencia de los aportes terrígenos (cuarzo, feldespatos, illita e illita/esmectita). En las sedimentitas del sector depocentral (facies de pelitas grises oscuras) son importantes los indicadores de productividad orgánica (carbonatos y cuarzo biogénico), de condiciones anóxicas (pirita, siderita) y de un lento ritmo de acumulación sedimentaria. Los depósitos depocentrales de la transgresión tithoniana corresponden a la cocina de hidrocarburos de la Formación Vaca Muerta. Sus amplias variaciones mineralógicas ejercen fuerte impacto en la conversión de materia orgánica y en la liberación de gas y petróleo, así como en las propiedades petrofísicas y la fragilidad de rocas que constituyen la fuente principal para la explotación no convencional de hidrocarburos en la Cuenca Neuquina

Linking derived debitage to the Stonehenge Altar Stone using portable X-ray fluorescence analysis

The Altar Stone at Stonehenge in Wiltshire, UK, is enigmatic in that it differs markedly from the other bluestones. It is a grey-green, micaceous sandstone and has been considered to be derived from the Old Red Sandstone sequences of South Wales. Previous studies, however, have been based on presumed derived fragments (debitage) that have been identified visually as coming from the Altar Stone. Portable X-ray fluorescence (pXRF) analyses were conducted on these fragments (ex situ) as well as on the Altar Stone (in situ). Light elements (Z<37) in the Altar Stone analyses, performed after a night of heavy rain, were affected by surface and pore water that attenuate low energy X-rays, however the dry analyses of debitage fragments produced data for a full suite of elements. High Z elements, including Zr, Nb, Sr, Pb, Th and U, all occupy the same compositional space in the Altar Stone and debitage fragments, and are statistically indistinguishable, indicating the fragments are derived from the Altar Stone. Barium compares very closely between the debitage and Altar Stone, with differences being related to variable baryte distribution in the Altar Stone, limited accessibility of its surface for analysis, and probably to surface weathering. A notable feature of the Altar Stone sandstone is the presence of baryte (up to 0.8 modal%), manifest as relatively high Ba in both the debitage and the Altar Stone. These high Ba contents are in marked contrast with those in a small set of Old Red Sandstone field samples, analysed alongside the Altar Stone and debitage fragments, raising the possibility that the Altar Stone may not have been sourced from the Old Red Sandstone sequences of Wales. This high Ba 'fingerprint', related to the presence of baryte, may provide a rapid test using pXRF in the search for the source of the Stonehenge Altar Stone