Characterization of a new protocol for mortar dating: 13C and 14C evidences

This paper reviews the present knowledge about the analysis of mortars in the framework of artworks absolute chronology determination with the aim to formulate a new methodology capable of systematically and accurately estimating the age of these constructive and/or art materials. The core of the proposed methodology is represented by a physical procedure (ultrasonication) selecting only carbonaceous materials represented by carbonates formed after the absorption of atmospheric CO2 (carbonatation) by mortars (binder) during their setting. With the aim to evaluate the procedure efficiency in the isolation of binder signal from the most important source of carbonates, the proposed procedure was tested on a series of laboratory mortars produced, in a simplified version, in the laboratory environment. Mortar production was characterized by means of a series of measurements allowing to draw important indications about the applied procedure. The radiocarbon value of isolated binder carbonates was compared with the CO2 signal sampled form laboratory air during mortar setting. The observed results confirmed preliminarily the good protocol accuracy for radiocarbon dating suggesting its capability for the application to real study cases

THE BEGINNING OF THE IRON AGE AT ARSLANTEPE: A 14C PERSPECTIVE

The Iron Age chronology at Arslantepe is the result of the interpretation of Luwian hieroglyphic inscriptions and archaeological data coming from the site and its surrounding region. A new round of investigations of the Iron Age levels has been conducted at the site over the last 10 years. Preliminary results allowed the combination of the archaeological sequence with the historical events that extended from the collapse of the Late Bronze Age empires to the formation and development of the new Iron Age kingdoms. The integration into this picture of a new set of radiocarbon (14C) dates is aimed at establishing a more solid local chronology. High precision 14C dating by accelerator mass spectrometry (AMS) and its correlation with archaeobotanical analysis and stratigraphic data are presented here with the purpose of improving our knowledge of the site’s history and to build a reliable absolute chronology of the Iron Age. The results show that the earliest level of the sequence dates to ca. the mid-13th century BC, implying that the site started developing a new set of relationships with the Levant already before the breakdown of the Hittite empire, entailing important historical implications for the Syro-Anatolian region at the end of the 2nd millennium BC

Datando argamasas: tres ejemplos de arquitectura medieval hispana

One of the major issues in building archaeology is finding the age of elements and structures discovered. Mortars represent a class of material basically constituted by a mixture of different phases (i.e. binder, aggregates, water) and are widely used for constructive uses and artworks. Current scientific literature regarding the possibility of accurate radiocarbon dating for mortars reports different and still contradictory results. In this study, a new protocol for radiocarbon dating of mortar developed at the Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) is used to perform 14C measurements on archaeological mortars coming from three medieval architectures of northern Spain (two churches and the walls of a castle). Results observed will be discussed and compared with independent age estimations (i.e. radiocarbon dating performed on organic materials found in the same study site, archaeological analyses) in order to frame experimental observations in the actual site knowledge by means of a multidisciplinary approach.Una de las principales problemáticas a las que se enfrenta la arqueología de la arquitectura es datar los elementos y las estructuras. Las argamasas son un tipo de material constituido por una mezcla de diferentes elementos (agregados, agua) y empleadas en muchos tipos de construcciones. Los estudios realizados hasta la actualidad en torno a la posibilidad de realizar dataciones radiocarbónicas precisas han proporcionado resultados contradictorios. El objetivo de este artículo es el de presentar un nuevo protocolo para datar la arquitectura histórica desarrollado por el Centre for Isotopic Research on Cultural and Enviromental Heritage (CIRCE), basado en la realización de dataciones radiocarbónicas de argamasas a partir del análisis de tres arquitecturas medievales del norte del España, dos iglesias y la muralla de un castillo. Los resultados obtenidos han sido confrontados y comparados con otros indicadores cronológicos independientes (dataciones radiocarbónicas realizadas en los mismos yacimientos, materiales y análisis arqueológicos) con el fin de analizar estos valores desde un enfoque multidisciplinar

AMS radiocarbon dating of mortar: The case study of the medieval UNESCO site of Modena

The carbon dioxide contributing to binder formation during the set of a lime mortar reflects the atmospheric 14C content at the time of construction of a building. For this reason, the 14C dating of mortars is used with increasing frequencies in archaeological and architectural research. Mortars, however, may also contain carbonaceous contaminants potentially affecting radiocarbon dating. The Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) of the Second University of Naples (SUN) has recently obtained some promising results in mortar radiocarbon dating thanks to the development of a procedure (i.e. CryoSoniC/Cryo2SoniC) aiming to eliminate exogenous C contamination that may occur in a mortar. The construction history of the UNESCO World Heritage Site of Modena (Italy) is still controversial and represents a challenging case study for the application of absolute dating methodologies for different reasons. From the point of view of 14C dating, for example, given the high percentage of carbonate aggregates composing these samples, Modena mortars represent an experimental test particularly indicative of exogenous carbon sources suppression ensuring methodology accuracy. In this paper several AMS Radiocarbon dates were carried out on lime lumps with the aim to: (i) verify procedure accuracy by a comparison of the results obtainable from lime lumps dated after different treatments (i.e. bulk lime lumps vs. CryoSoniC purified lime lumps); (ii) compare different building phases absolute chronology for the medieval UNESCO site of Modena, with that assumed by historical sources in order to assess preliminary the 14C dating feasibility for of the site. Historical temporal constraints and mortar clustering, based on petrography, have been applied to define a temporal framework of the analyzed structure. Moreover, a detailed petrographic characterization of mortars was used both as a preliminary tool for the choice of samples and to infer about the lack of accuracy (when verified) of the applied mortar 14C dating procedure

Long tree-ring chronologies provide evidence of recent tree growth decrease in a central african tropical forest

It is still unclear whether the exponential rise of atmospheric CO2 concentration has produced a fertilization effect on tropical forests, thus incrementing their growth rate, in the last two centuries. As many factors affect tree growth patterns, short -term studies might be influenced by the confounding effect of several interacting environmental variables on plant growth. Long-term analyses of tree growth can elucidate long-term trends of plant growth response to dominant drivers. The study of annual rings, applied to long tree-ring chronologies in tropical forest trees enables such analysis. Long-term tree-ring chronologies of three widespread African species were measured in Central Africa to analyze the growth of trees over the last two centuries. Growth trends were correlated to changes in global atmospheric CO2 concentration and local variations in the main climatic drivers, temperature and rainfall. Our results provided no evidence for a fertilization effect of CO2 on tree growth. On the contrary, an overall growth decline was observed for all three species in the last century, which appears to be significantly correlated to the increase in local temperature. These findings provide additional support to the global observations of a slowing down of C sequestration in the trunks of forest trees in recent decades. Data indicate that the CO2 increase alone has not been sufficient to obtain a tree growth increase in tropical trees. The effect of other changing environmental factors, like temperature, may have overridden the fertilization effect of CO2.It is still unclear whether the exponential rise of atmospheric CO2 concentration has produced a fertilization effect on tropical forests, thus incrementing their growth rate, in the last two centuries. As many factors affect tree growth patterns, short -term studies might be influenced by the confounding effect of several interacting environmental variables on plant growth. Long-term analyses of tree growth can elucidate long-term trends of plant growth response to dominant drivers. The study of annual rings, applied to long tree-ring chronologies in tropical forest trees enables such analysis. Long-term tree-ring chronologies of three widespread African species were measured in Central Africa to analyze the growth of trees over the last two centuries. Growth trends were correlated to changes in global atmospheric CO2 concentration and local variations in the main climatic drivers, temperature and rainfall. Our results provided no evidence for a fertilization effect of CO2 on tree growth. On the contrary, an overall growth decline was observed for all three species in the last century, which appears to be significantly correlated to the increase in local temperature. These findings provide additional support to the global observations of a slowing down of C sequestration in the trunks of forest trees in recent decades. Data indicate that the CO2 increase alone has not been sufficient to obtain a tree growth increase in tropical trees. The effect of other changing environmental factors, like temperature, may have overridden the fertilization effect of CO2

Contribution and stability of forest-derived soil organic carbon during woody encroachment in a tropical savanna. A case study in Gabon

In this study, we quantified the contribution of forest-derived carbon (FDC) to the soil organic C (SOC) pool along a natural succession from savanna (S) to mixed Marantaceae forest (MMF) in the Lopè National Park, Gabon. Four 1-ha plots, corresponding to different stages along the natural succession, were used to determine the SOC stock and soil C isotope composition (δ13C) to derive the FDC contribution in different soil layers down to 1 m depth. Besides, to investigate changes in SOC stability, we determined the 14C concentration of SOC to 30 cm depth and derived turnover time (TT). Results indicated that SOC increased only at the end of the succession in the MMF stage, which stored 46% more SOC (41 Mg C ha−1) in the 0–30 cm depth than the S stage (28.8 Mg C ha−1). The FDC contribution increased along forest succession affecting mainly the top layers of the initial successional stages to 15 cm depth and reaching 70 cm depth in the MMF stage. The TT suggests a small increase in stability in the 0–5 cm layer from S (146 years) to MMF (157 years) stages. Below 5 cm, the increase in stability was high, suggesting that FDC can remain in soils for a much longer time than savanna-derived C. In conclusion, the natural succession toward Marantaceae forests can positively impact climate change resulting in large SOC stocks, which can be removed from the atmosphere and stored for a much longer time in forest soils compared to savanna soils

A Holocene tephra layer within coastal aeolian deposits north of Caleta Olivia (Santa Cruz Province, Argentina)

In this paper we illustrate the stratigraphy, geochronology, and geochemistry (major, minor, trace elements and Sr-isotopes) of a Holocene tephra layer found within coastal sedimentary deposits north of Caleta Olivia (Santa Cruz Province, Argentina). The stratigraphic succession comprises beach deposits with basal erosive surface resting on the local substrate (“Formación Patagonia”) followed by a poorly developed paleosoil. The paleosoil is covered by a lenticular fine grained (Mdφ: 5.2, 0.027 mm), well sorted (σφ: 1.2) volcanic ash layer and aeolian sands. The geochemical composition of shard fragments points to an origin from the Hudson volcano, located in the southern Andes, ca. 400 km to the west. The geochemistry, Sr-isotopes and the radiometric constraints (younger than the age of the underlying marine layer dated at ca. 4,100 a cal BP) further allow correlating this tephra with the so-called H2 eruption (ca. 3,900 a cal BP). This finding is of interest owing to the poor preservation potential of tephra within the Late Holocene sedimentary deposits of the Atlantic coast of Patagonia and represents the first finding of H2 eruption in this area, improving our knowledge of the dispersion of the fine-grained distal deposit of the Hudson volcanic explosive activity, thus allowing a better estimate of the eruptive dynamics and the risks associated with the Hudson volcano

Mid-Holocene relative sea-level changes along Atlantic Patagonia: new data from Camarones, Chubut, Argentina

This paper concerns the relative sea-level changes associated with the Atlantic Patagonian coast derived from sea-level index points whose elevation was determined by a differential global position system (DGPS). Bio encrustations from outcrops located near Camarones, Chubut, Argentina, consist of autochthonous deposits characterized by Austromegabalanus psittacus (Molina, 1782), encrusting acer vulinid foraminifera, coralline red algae and bryozoans. The association of the different organisms is interpreted as being associated with an intertidal environment, and they have been used as index points to establish the relative sea-level position. The main conclusion is that the relative sea-level between c. 7000 and 5300 cal. yr BP was in the range ofc. 2?4 m a.s.l., with a mean value of c. 3.5 m a.s.l. Our data seem to support the existence of different rates of relative sea-level fall in different sectors of Atlantic Patagonia during the Holocene and highlight the importance of a more precise and accurate relative sea-level estimation by producing new data and revisiting the indicative meaning of most of the indicators so far used in the area.Facultad de Ciencias Naturales y Muse

Niveles altos del mar durante el Último Máximo Interglacial deducidos mediante muescas de abrasión y márgenes internos de terrazas marinas en Puerto Deseado, Provincia de Santa Cruz, Argentina

A detailed geomorphological survey was undertaken in the area of Puerto Deseado (Santa Cruz Province, Argentina) to reconstruct the Relative Sea-level (RSL) position during the Last Interglacial highstand. The presence of active and well-preserved abrasive notches and inner margins of terraces related to the MIS5e and to the Holocene, measured with DGPS, allowed to accurately estimate the RSL change from the present to the MIS5e highstand at ca. 21 m. The geomorphological and geochronological analyses support the notion of the presence of a significant regional tectonic uplift in the Atlantic Patagonia, which can be locally estimated at ca. 0.12 mm/yr.Se realizó un estudio geomorfológico detallado en la zona de Puerto Deseado (provincia de Santa Cruz, Argentina) para reconstruir la posición relativa del nivel (RNM) del mar durante el Último Máximo Interglacial. La presencia de muescas de abrasión activas y bien conservadas, y la posición de los márgenes internos de las terrazas relacionadas con el MIS5e y el Holoceno, medido con GPS diferencial, permitió estimar con precisión el cambio RNM desde el presente hasta la transgresión MIS5e en aproximadamente 21 m. Los análisis geomorfológicos y geocronológicos sustentan la noción de la presencia de un significativo levantamiento tectónico regional en la Patagonia Atlántica, que puede estimarse localmente en alrededor de 0,12 mm/año.Facultad de Ciencias Naturales y Muse

Una capa de tefra holocena intercalada en los depósitos eólicos costeros ubicados al norte de Caleta Olivia (Provincia de Santa Cruz, Argentina)

In this paper we illustrate the stratigraphy, geochronology, and geochemistry (major, minor, trace elements and Sr-isotopes) of a Holocene tephra layer found within coastal sedimentary deposits north of Caleta Olivia (Santa Cruz Province, Argentina). The stratigraphic succession comprises beach deposits with basal erosive surface resting on the local substrate (“Formacion Patagonia”) followed by a poorly developed paleosoil. The paleosoil is covered by a lenticular fine-grained (Mdφ: 5.2, 0.027 mm), well sorted (σφ: 1.2) volcanic ash layer and aeolian sands. The geochemical composition of shard fragments points to an origin from the Hudson volcano, located in the southern Andes, ca. 400 km to the west. The geochemistry, Sr-isotopes and the radiometric constraints (younger than the age of the underlying marine layer dated at ca. 4,100 a cal BP) further allow correlating this tephra with the so-called H2 eruption (ca. 3,900 a cal BP). This finding is of interest owing to the poor preservation potential of tephra within the Late Holocene sedimentary deposits of the Atlantic coast of Patagonia and represents the first finding of H2 eruption in this area, improving our knowledge of the dispersion of the fine-grained distal deposit of the Hudson volcanic explosive activity, thus allowing a better estimate of the eruptive dynamics and the risks associated with the Hudson volcano.Este artículo aborda la estratigrafía, geocronología y geoquímica (elementos mayoritarios, minoritarios, trazas e isótopos de Sr) de un nivel de tefra holocena que forma parte de una secuencia de sedimentos costeros ubicados al norte de Caleta Olivia (provincia de Santa Cruz, Argentina). La secuencia comprende depósitos sedimentarios que se disponen sobre una superficie basal erosiva que suprayace al sustrato local (“Formación Patagonia”), y continúa esta secuencia con un paleosuelo de escaso desarrollo. El paleosuelo está cubierto por una capa lenticular de cenizas volcánicas de grano fino (Mdφ: 5,2, 0,027 mm), bien seleccionada (σφ: 1,2) y arenas eólicas. La composición geoquímica de los shards indica que esta tefra se originó en el volcán Hudson, ubicado en los Andes del sur, a aproximadamente 400 km hacia el oeste. La geoquímica, los isótopos de Sr y las restricciones radiométricas (más joven que la edad de la capa marina que la subyace, fechada en aproximadamente 4.100 a cal AP) permiten correlacionar esta tefra con la denominada erupción H2 de dicho volcán (ocurrida aproximadamente 3.900 a cal AP). Este hallazgo es de interés debido al escaso potencial de preservación de los depósitos de tefra dentro de las secuencias sedimentarias costeras del Holoceno Tardío, en la costa atlántica de Patagonia y representa el primer hallazgo del evento eruptivo H2 en esta área, lo cual contribuye a mejorar el conocimiento sobre la dispersión de la tefra generada por la actividad volcánica explosiva del volcán Hudson, lo que permite una mejor estimación de la dinámica eruptiva y los riesgos asociados con este volcán.Centro de Estudios Integrales de la Dinámica Exógen