Using Mg/Ca ratios from the limpet Patella depressa Pennant, 1777 measured by laser-induced breakdown spectroscopy (LIBS) to reconstruct paleoclimate

Measurement of the elemental composition of shells is increasingly emerging as an avenue for obtaining high-resolution insights into paleoclimate and past seasonality. Several studies have shown significant correlations between Mg/Ca ratios measured on shell carbonate and the sea surface temperature (SST) within which this carbonate was precipitated. However, other investigations have reported large variability in this relationship between species. Therefore, further studies, including taxa previously not considered are still required in order to validate these new species as suitable climate proxies. Here, we measured Mg/Ca ratios for limpet Patella depressa Pennant, 1777 samples live-collected in northern Spain for the first time. The elemental ratio was measured using laser-induced breakdown spectroscopy (LIBS), a technique that significantly decreases the time required for sample preparation and increases the number of shells that can be analyzed. In this study, calibration-free LIBS (CF-LIBS) methods were applied to estimate molar concentrations of chemical elements on biogenic calcium carbonate. The Mg/Ca ratio evolution along the shell growth axis was compared with stable oxygen isotope (δ18O) profiles obtained from these same limpets and the SST at the place where the mollusk grew to determine if the sequences obtained correctly reflected environmental conditions during the life-span of the mollusk. The results showed a significant correlation between Mg/Ca ratio series and both δ18O profiles and SST, highlighting the paleoenvironmental and archaeological potential of LIBS analyses on this mollusk species that is frequently found in archaeological contexts in the western Europe.This research was performed as part of the projects HAR2016-75605-R, HAR2017-86262-P and PID2019-107270RB-C21/AEI/10.13039/501100011033, funded by the Spanish Ministry of Economy and Competitiveness, MINECO. During the development of this research A.G.E was funded by the Basque Country Postdoctoral Program through a postdoctoral grant (POS_2020_2_0032). This study has also been supported by the Prehistoric Research Consolidated Group of the Basque Country University (IT-1223-19), funded by the Basque Country Government. P.R. is funded by the Max Planck Society

Growth patterns of the topshell Phorcus lineatus (da Costa, 1778) in northern Iberia deduced from shell sclerochronology

Combined shell growth pattern and oxygen isotope analysis has become a powerful approach in palaeoclimate and archaeological studies for reconstructing palaeoclimate conditions and littoral exploitation patterns, respectively. Recent investigations have shown that the gastropod Phorcus lineatus (da Costa, 1778) forms its shell in conditions of near equilibrium with the oxygen isotope signature of the seawater environment, demonstrating the utility of this species for reconstruction of sea surface temperature and determination of the season of harvest in archaeological studies. In contrast, the shell growth patterns of this species have received virtually no attention despite providing information on the rate and timing of shell growth that is crucial for correctly interpreting environmental proxies derived from shell geochemistry. In this paper, we compare microgrowth patterns and isotopic profiles of four modern individuals of the gastropod P. lineatus from northern Iberia to determine the timing and periodicity of subannual growth markers within the shells. Results of this sclerochronological study showed the presence of two types of growth lines/increments: i) large-scale accretionary units formed with variable periodicity, and ii) small-scale accretionary units formed by micro growth lines and increments determined by semidiurnal tidal cycles. Results suggest that shells grew uninterruptedly during early ontogeny. However, older specimens exhibited growth cessation/slowdown during summer and winter/spring. Therefore, shell growth rate is not only controlled by environmental conditions, but also by ontogenetic age and/or endogenous rhythms. A high correlation was found between seawater temperature derived from shell oxygen isotopes and instrumental seawater temperature (r2 = 0.88–0.98; p-values < 0.0001). This study shows that establishing accurate growth patterns of the topshell P. lineatus is essential for correctly reconstructing past seawater temperature conditions in palaeoclimate studies and for determining with higher precision the season(s) when the subfossil shells were collected by humans.This research was performed as part of the project TRACECHANGE: Tracing Climatic Abrupt Change Events and their Social Impact during the Late Pleistocene and Early Holocene (15–7 ky cal BP) (2014–2016) (HAR2013-46802-P), funded by the Spanish Ministry of Economy and Competitiveness, MINECO. AGE was funded by the University of Cantabria through a predoctoral grant (no code available). IGZ was also supported by the Juan de la Cierva Research Programme (grant number JCI-2012-12094) funded by the MINECO

Automated measurement of magnesium/calcium ratios in gastropod shells using laser-induced breakdown spectroscopy for paleoclimatic applications

The chemical composition of mollusk shells offers information about environmental conditions present during the lifespan of the organism. Shells found in geological deposits and in many archeological sites can help to reconstruct past climatic conditions. For example, a correlation has been found between seawater temperature and the amount of some substituent elements (e.g., magnesium, strontium) in the biogenerated calcium carbonate matrix of the shell, although it is very species-specific. Here we propose the use laser-induced breakdown spectroscopy (LIBS) to estimate Mg/Ca ratios in modern specimens of the common limpet Patella vulgata. An automated setup was used to obtain a sequence of Mg/Ca ratios across a sampling path that could be compared with the seawater temperatures recorded during the organism's lifespan. Results using four shells collected in different months of the year showed a direct relationship between the Mg/Ca ratios and the seawater temperature, although the sequences also revealed small-scale (short-term) variability and an irregular growth rate. Nevertheless, it was possible to infer the season of capture and the minimum and maximum seawater temperatures from the LIBS sequences. This fact, along with the reduction in sampling and measurement time compared with other spectrometric techniques (such as inductively coupled plasma mass spectrometry [ICP-MS]), makes LIBS useful in paleoclimatic studies.The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article. This research was part of the projects TEC2013-47264-C2-1-R and HAR2013-46802-P, both funded by the Spanish Ministry of Economy and Competitiveness. Asier García-Escázaga was funded by the University of Cantabria through a predoctoral grant and Igor Gutierrez-Zugasti was supported by the Juan de la Cierva programme (JCI-2012-12094) funded by the Spanish Ministry of Economy and Competitiveness

Stable oxygen isotope analysis of Phorcus lineatus (da Costa, 1778) as a proxy for foraging seasonality during the Mesolithic in northern Iberia

The Mesolithic period in the Cantabrian region, a coastal area located in northern Spain, is characterised by a marked increase in the human use of coastal resources in comparison with previous periods, resulting in the formation of so-called "shell middens". Archaeological investigations have provided insights into the formation processes of these shell middens, as well as long-term changes in human exploitation of different marine resources and the relationship of foraging strategies to past climate changes. However, efforts to reconstruct the key environmental factor governing coastal subsistence and foraging resilience, the seasonal availability and use of different marine resources, have been limited in the region and, indeed, across coastal Mesolithic Europe more widely. Here, we use stable oxygen isotope analysis of Phorcus lineatus (da Costa, 1778), one of the most widespread molluscs in northern Iberian mesolithic coastal sites, in order to determine the season in which humans collected key coastal resources at the site of EL Mazo (Llanes, Asturias). We demonstrate that P. lineatus was exclusively collected in late autumn, winter and early spring. An experimental programme, in which modern P. lineatus specimens were collected in situ over the course of three years, established that relative meat yield varied within this species throughout the annual cycle, with higher relative meat yield during colder months. We argue that mollusc collection patterns were driven by a cost-benefit principle during the Mesolithic in the Cantabrian region and human populations had intimate knowledge of the seasonal developmental cycles of exploited marine taxa. This also highlights the importance of developing intra-annual records of resource use and climate change if coastal foraging is to be properly understood in prehistory.This research was performed as part of the projects HAR2016-75605-R and HAR2017-86262-P, funded by the Spanish Ministry of Economy and Competitiveness, MINECO. During the development of this research, AGE was funded by the University of Cantabria through a pre-doctoral grant (no code available) and is currently supported by the Basque Country Postdoctoral Programme (grant number POS_2018_1_0016). DCS was supported by the Juan de la Cierva Research Programme (IJCI-2014-20590) of the Spanish Ministry of Economy and Competitiveness

Bayesian estimates of marine radiocarbon reservoir effect in northern Iberia during the Early and Middle Holocene

Reconstructing the past variability of marine radiocarbon reservoir effects (MRE) is crucial for generating reliable chronologies for marine species and their consumers. We investigated the temporal MRE variability at the Early-to Mid-Holocene site of El Mazo (Asturias, northern Spain) by using a combination of new and previously published radiocarbon measurements on marine and terrestrial samples. The El Mazo site is characterized by overall well-defined archaeological layers of unknown occupation length with the predominant presence of two mollusc species (Patella vulgata Linnaeus, 1758 and topshell Phorcus lineatus [da Costa, 1778]) which were analysed for radiocarbon measurements. We employed the recently released IntCal20 calibration curve for the northern hemisphere and Bayesian modelling to reconstruct the site?s chronology and temporal variability in MREs according to mollusc species. Obtained radiocarbon modelling results, although the estimate precision is not high, reveal a temporal variability in MREs that can be interpreted in view of known past climatic and environmental events such as the 8.2 ka event. The results also revealed differences in MREs according to mollusc species, which need to be taken into account in future chronological modelling. Overall, our results provide reference MRE values for the study of chronologies in northern Iberia during the Early-to Mid-Holocene. In this respect, a non-conservative ?R reference for local marine samples dating earlier than c. 8.1 ka cal BP is - 238 ± 28 14C years.This research was performed as part of the projects HAR 2016- 75605-R and HAR 2017-86262-P, funded by the Spanish Ministry of Economy and Competitiveness, MINECO. During the development of this research AGE was funded by the Basque Country Postdoctoral Programme through a postdoctoral grant (POS_2020_2_0032) and University of La Rioja (no code available). This study has also been supported by the Prehistoric Research Consolidated Group of the Basque Country University (IT-1223-19), funded by the Basque Country Government. PR and RF are funded by the Max Planck Society. We thank the Fishing Activity Service of the Cantabrian Government for the authorization to collect modern specimens. We also thank the Max Plank Society, University of La Rioja, Basque Country University (UPV/EHU), University of Cantabria (UC) and Instituto Internacional de Investigaciones Prehist´oricas de Cantabria (IIIPC) for providing support

Automated analysis of the elemental composition of mollusk shells by Laser Breakdown Spectroscopy (LIBS)

RESUMEN: La composición de las conchas de moluscos marinos ofrece una valiosa información sobre el entorno en el que se han desarrollado, por ejemplo, la temperatura del agua en cada momento de su crecimiento puede estimarse a partir de la relación magnesio/calcio o estroncio/calcio, o también a partir de la distribución de isótopos de oxígeno en diferentes puntos de la concha. Sin embargo, las técnicas actuales de análisis (como ICP-OES) necesitan de un proceso de muestreo y extracción de material a lo largo de la concha que es largo y tedioso. En este trabajo se propone la utilización de la técnica de espectroscopía atómica LIBS mediante láseres pulsados intensos para una estimación cuantitativa de los ratios Mg/Ca y Sr/Ca en cualquier punto de la concha y de forma automatizada, permitiendo reconstruir la secuencia de temperaturas del agua marina durante el crecimiento del molusco. Aplicada esta técnica a restos arqueológicos de conchas, es posible determinar la estación de captura e inferir por tanto información sobre el comportamiento de las poblaciones humanas en áreas costeras.ABSTRACT: The chemical composition of marine mollusk shells offers useful information about the their environment during their life span, for example, the seawater temperature at any moment can be estimated from the magnesium/calcium or strontium/calcium ratios, or from the oxygen isotopes distribution at specific points in the shell. However, current analytic techniques (like ICP-OES) need of long and cumbersome sampling procedures over the shell area. In this work, we propose to use the Laser Breakdown Spectroscopy (LIBS) technique with intense pulsed lasers to get a quantitative estimation of the Mg/Ca and Sr/Ca ratios at any point in the shell and in an automated way, allowing the reconstruction of the seawater temperature sequences during the mollusk lifespan. This technique can be applied to archaeological shells from the Mesolithic period to infer the season of capture and thus, to get information about the seasonality patterns of prehistoric groups in coastal areas

Mobility and the use of littoral resources in the Late Mesolithic of Northern Spain: the case of La Chora cave (Voto, Cantabria, N Spain)

Unidad de excelencia María de Maeztu CEX2019-000940-MLittoral resources have been consumed by humans since at least the Middle Palaeolithic. Examples of the use of molluscs have been documented along the shores of Europe during that period but it was not until many millennia later that European hunter-fisher-gatherer societies exploited those resources intensively-see the case of Nerja cave during the Younger Dryas. This economic activity caused the accumulation of shells at archaeological sites during the Mesolithic, resulting in the formation of the so-called shell middens, a very common type of deposit along the Atlantic seaboard of Europe. Despite the large number of research projects that have studied the exploitation of coastal environments and the way of life of Mesolithic populations, questions such as the relationship between human mobility and mollusc exploitation patterns still remain. The archaeomalacological study of the shell midden in La Chora cave (Cantabria, Spain) confirms that people foraged for shellfish at several places along the coast, mainly in the estuary of the River Asón. The main difference between La Chora and other Mesolithic sites is its longer shellfish collection radius as the inhabitants travelled over 10 km to the open coast to collect shellfish. This study has expanded the available data about the subsistence strategies of Mesolithic groups in a little-studied area and improved our knowledge of mobility patterns among Mesolithic societies in the northern Iberian Peninsula

Climate changes and exploitation of coastal resources during the upper Palaeolithic and the Mesolithic: a decade of investigations in Cantabria

RESUMEN: Tradicionalmente, las actividades relacionadas con la explotación de recursos marinos han sido consideradas como secundarias dentro de las estrategias de subsistencia de las poblaciones de cazadores-recolectores-pescadores de la región. En los últimos diez años se han desarrollado varios proyectos de investigación coordinados desde el Instituto Internacional de Investigaciones Prehistóricas de Cantabria (IIIPC) cuyos objetivos generales son la reconstrucción de las condiciones climáticas y medioambientales del pasado, el establecimiento de los patrones de ocupación de la costa, y el papel de los recursos costeros en las estrategias económicas y sociales de las poblaciones humanas del Paleolítico superior y el Mesolítico. En este artículo se realiza un repaso a los resultados obtenidos en dichos proyectos a partir del estudio de los moluscos, equinodermos y crustáceos. Los resultados obtenidos hasta la fecha reflejan una continuada y variada utilización de estos recursos a lo largo de todo el periodo, y sugieren que su importancia fue mayor de lo que se pensaba.ABSTRACT: Traditionally, activities related to the exploitation of marine resources have been considered secondary within the subsistence strategies of populations of hunter-gatherer-fishers in the region. In the last ten years we have developed several research projects coordinated by the International Institute of Prehistoric Research of Cantabria (IIIPC), aiming to reconstruct past climatic and environmental conditions, establish coastal settlement patterns and to assess the role of coastal resources in economic and social strategies of Upper Palaeolithic and Mesolithic human populations. This article reviews the results of these projects through the study of molluscs, echinoderms and crustaceans. The results to date reflect a continued and varied use of marine resources throughout the entire period, and suggest that their importance was greater than previously thought.Las investigaciones descritas en este artículo se han desarrollado en el marco de los proyectos HUM 2006-13729, HAR2010-22115-C02-01 y HAR2013- 46802-P financiados por el Gobierno de España, el proyecto NF100413 financiado por la British Academy y la Royal Society a través del programa Newton International Fellowships, y el proyecto UFG54/Proyecto1470 financiado por la Fundación Marcelino Botín. IGZ y DCS disfrutan de sendos contratos del programa Juan de la Cierva (JCI-2012-12094 e IJCI-2014- 20590, respectivamente) financiado por el Ministerio de Economía y Competitividad (MINECO). AGE disfruta de un contrato predoctoral de la Universidad de Cantabria y RSR cuenta con el apoyo de una ayuda para contratos predoctorales para la formación de doctores (BES-2014-070075) financiada por el MINECO

Crónica de las IX Jornadas de Jóvenes en Investigación Arqueológica. Arqueología en 3D: herramienta social, agente histórico y ciencia natural. Instituto Internacional de Investigaciones Prehistóricas de Cantabria (IIIPC), Universidad de Cantabria (UC), S

Crónica de las IX Jornadas de Jóvenes en Investigación Arqueológica. Arqueología en 3D: herramienta social, agente histórico y ciencia natural. Instituto Internacional de Investigaciones Prehistóricas de Cantabria (IIIPC), Universidad de Cantabria (UC),

Comparison of Mg/Ca concentration series from Patella depressa limpet shells using CF-LIBS and LA-ICP-MS

The elemental composition of marine mollusk shells can offer valuable information about environmental conditions experienced by a mollusk during its lifespan. Previous studies have shown significant correlations between Mg/Ca concentration ratios measured on biogenic carbonate of mollusk shells and sea surface temperature (SST). Here we propose the use of Laser-Induced Breakdown Spectroscopy (LIBS) and the validation of the Calibration-Free LIBS (CF-LIBS) approach for the rapid measurement and estimation of Mg/Ca molar concentration profiles within Patella depressa Pennant, 1777 limpet shells. To achieve these objectives, results derived from CF-LIBS methodology are compared with those obtained from an established analytical technique for this purpose, such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Concentration series obtained with both methodologies show defined temporal patterns and reflect the season-of-capture in each specimen. The results evidence a significant correlation (R2 = 0.63–0.81) between CF-LIBS and LA-ICP-MS Mg/Ca molar concentration profiles within four live-collected P. depressa shells. Averaged error for the molar concentration estimated with CF-LIBS was lower than 10% in every specimen. The comparison between the results obtained from two techniques used in this study has allowed us to demonstrate for the first time that Mg/Ca molar concentration measured in biogenic carbonates were accurately inferred using CF-LIBS technique. The CF-LIBS approach validation represents great potential for the rapid and large-scale paleoenvironmental and archaeological analysis of this mollusk species, which is frequently found in archaeological sites.1. Introduction 2. Materials and methods 2.1. Sample preparation 2.2. LA-ICP-MS setup and analyses 2.3. LIBS setup and measurements 2.4. CF-LIBS application 3. Results and discussion 3.1. LA-ICP-MS concentration profiles 3.2. CF-LIBS approach results 3.3. CF-LIBS and LA-ICP-MS comparison 3.4. Implications for paleoclimatology and archaeology 4. Conclusion