News



Mediterranean Limpets

In our new study in Scientific Reports, we tested LIBS on modern limpet shells that were previously analysed by Amy Prendergast and Bernd Schöne using δ18O values and a high resolution sampling approach. With their large isotopic dataset and good knowledge of the shells' growth structure, we had a great starting point to compare Mg/Ca ratios with changes in sea surface temperature (SST)

A link between the two has been shown in Mediterranean limpets before by Ferguson et al. (2011) , but the connection was not found consistently or in every shell specimen. So we wanted to find out whether there might be spatial differences in the elemental patterns across one growth increment. This would mean that at the same time and within the same time slice, which is represented by one increment, different Mg/Ca ratios were deposited in the record, although the SST would be the same. This kind of spatial variability could have some implications for other Mg/Ca studies that try to come up with temperature equations that translate Mg/Ca ratios into °C

Corrgraph

In fact, we found several spatial patterns in the elemental maps with the potential to skew an elemental proxy record, if analysed using only a line scan instead of mapping. Interestingly, after we had knowledge of these patterns, we were able to run line scans that take the spatial variability into account and resulted in very good correlation.

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Tasmanian Limpets

Find below a short update on limpet shells which we recently analysed for Fleur King (La Trobe University) and the archaeological sites of her PhD in Tasmania. They are modern Cellana solida shells related to a small shell midden in Rocky Cape.

We looked at 3 of the specimens and they look similar to specimens of the Californian Mussel (see blog post below) with Mg/Ca patterns differing clearly between calcite and aragonite sections of the same increment. Calcite shows up with much higher (brighter) ratios and aragonite with much lower (darker) ratios, but at the same time, they show similar patterns of change, allowing us to tentatively relate the changes through time in both layers.

The banding patterns on both sides of the shell can tentatively be linked to changes in sea surface temperature (SST), as has been shown in Mediterranean limpets Ferguson et al. (2011). If this is the case will become clear with oxygen isotope measurements of the same increments in the future. However, the different minimum and maximum ratios that we found for these shells, suggests that there are specimen-specific offsets, that will prevent a general equation between Mg/Ca ratios and SST.

Also there is an interesting line of high Mg/Ca that follow the direction of growth and seemingly separates the M+2 and M+3 layers in the calcite part of the shell. Since this pattern is not changign through time, it is unlikely to be controlled by climatic change. If the line really does show the border of the M+2 and M+3 layers, which we still need to determine, it is likely describing some changes in the crystal fabric, that lead to different incorporation of Mg-ions.

What we are also interested in at the moment is whether we can consistently find the accurate season of death for modern samples. When we apply this to shells from archaeological contexts, the season of death will tell us when people in the past would have eaten these shells.

Cellanas

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Irish Oysters

Find below a short update on oyster shells which I recently analysed for Chris Hunt (University of Liverpool) and one if his Irish sites. They are O. edulis shells from a small shell midden with samples of mixed preservation. As it is often the case, the hinges were better preserved than other parts, so I went ahead and made sections through left and right valves, which both worked fairly well.

I will not go into each analysed shell but instead show 3 of the specimens that are representative of the various Mg/Ca patterns that I have seen in the overall assemblage.

With further research, I hope to figure out, what elemental distribution is typical or most common in Oyster shells and get a general idea, to then make better interpretations of individual shell-records.

Irish Oysters

With further research, I hope to figure out, what elemental distribution is typical or most common in Oyster shells and get a general idea, to then make better interpretations of individual shell-records.

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Mg/Ca ratios in Californian mussels

After meeting Christopher Jazwa (Assistant Professor, University of Nevada) at the SAAs earlier this year, he sent me some of his Mytilus californianus shells to play with and test our LIBS system on.

I will not go into each analysed shell but instead show 3 of the specimens that are representative of the various Mg/Ca patterns that I have seen in the overall assemblage.

The shells are from Santa Rosa Island, which is known for its abundance of shell middens (albeit less entertaining than the middens on San Miguel Island). Santa Rosa middens and their shells are a massive source for climate data ranging back into the Mid-Holocene and provide first hand insights into the human exploitation of marine shells.

California Mussels

Christopher analyses the shell's geochemical properties, because these can change as a result of environmental change. The shells that Chris sent over were modern shells that he previously analysed using stable isotope measurements (?18O) to see what environmental change generally looks like within the records of Californian musses from Santa Rosa.

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New paper on elemental mapping of Shells using LIBS

We are happy to announce the first major publication of the ACCELERATE Project: Elemental mapping of Mg/Ca intensity ratios in marine mollusc shells using laser-induced breakdown spectroscopy in the Journal of Atomic and Analytical Spectroscopy.

In this paper we showcase our LIBS setup to carry out a rapid analysis of the elemental composition of shell carbonate, with over 2,000 sampling points per hour and little to no sample preparation.

We tested the LIBS setup using sections of three mollusc shells (Conomurex fasciatus, Ostrea edulis, Anomalocardia flexuosa) and successfully mapped the Mg/Ca ratio within them.

Our next step is to make the setup more user friendly and for it to easily provide the analysis of various selected elemental ratios.

Posted on June 26, 2017 by Niklas Hausmann


Resampling of C. fasciatus shell with improved setup

Here is a quick update on the most recent changes to our LIBS setup and a newer map of elemental ratios (Mg/Ca and Sr/Ca) from our Conomurex fasciatus shell recently published in JAAS.

The preliminary verdict here is that C. fasciatus from the Farasan Islands still remain difficult to interpret and are far from being used as a seasonality proxy. A more detailed report that compares the elemental ratios with stable oxygen isotopes is currently under review and I'll post it here when it comes out.

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ACCELERATE Project featured in documentary about life in Greece

The program '24 hours in Greece' of the Hellenic Broadcasting Corporation (ERT) covers everyday aspects of various parts of Greece, with the most recent episode featuring research in the laboratories of the Foundation for Research and Technology - Hellas, located in Heraklion, Crete.

The ACCELERATE project is featured as an example of innovative studies carried out at the Institute of Electronic Structures and Laser.

Posted on February 13, 2017 by Niklas Hausmann


Royal Society Meeting on Lost and Future Worlds

The Royal Society hosted a meeting to discuss the study of submerged landscapes.

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Preliminary results and update on the ACCELERATE Project

Generally, having more data points per shell or the ability to have more shells per site, has a lot of advantages. Firstly, it was shown that a large number of samples per shell increases the temporal resolution and thus allows us to determine the season of exploitation more accurately (Jew et al., 2013a, 2013b). Secondly, it is necessary to have a representative number of shells per site to determine a general site-seasonality (Thomas, 2015). Lastly, shells can also be used to create a seasonal structure for a layer or context, enhancing our understanding of site formation process or the use of artefacts (Hausmann and Meredith-Williams, 2016; Thompson and Andrus, 2011).

With these future applications in mind, I have worked on an experimental setup that allows the quick analysis of elemental ratios and their relation to environmental changes during the mollusc?s lifetime. In some cases, the ratios between elements (e.g. Mg, Sr, Ba ) and Ca have been linked to changes in environmental conditions, notably temperature and salinity, although other interplaying factors make more general statements very difficult (Graniero et al., 2017).

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Niklas Hausmann gives guest lecture at the University of Crete

Niklas Hausmann delivered a guest lecture at the Department of History and Archaeology at the University of Crete in Rethymno on 9th December 2016 entitled "Prehistoric coastal exploitation on the Farasan Islands, Saudi Arabia".

In his lecture Niklas described the outcomes of his PhD thesis that he finished at the University of York last year as a part of the ERC Project DISPERSE. The project aimed to study the dispersal of humans between Africa and Arabia, with a focus on the southern Red Sea as a gateway out of Africa. Niklas's research is based on excavations on the Holocene shell midden sites on the Farasan Islands, Saudi Arabia. He carried out a pilot study on the ecology of the marine gastropod Conomurex fasciatus, the main component of the shell middens, to understand the human exploitation of the marine resources. His study used the analysis of growth increments as well as stable oxygen and carbon isotopes of the shell carbonate. The results helped to understand seasonal growth patterns and isotope composition of the shells, which can be applied to seasonal patterns of mollusc consumption and human mobility.

The results of his PhD showed a strong reliance on marine resources and a intense exploitation of C. fasciatus in particular. They also showed that seasonal grouping of shells within midden layers can occur, which can help to further analyse the processes behind shell midden construction. However, this makes it necessary to increase the amount of samples that are analysed per layer, which is time consuming and often too costly.

In the final part of his lecture Niklas presented initial results from his current research project ACCELERATE at the Foundation for Research and Technology - Hellas in the Institute of Electronic Structure and Laser. The project aims to produce seasonal signals from shell carbonate using the rapid technique of elemental analysis, Laser Induced Breakdown Spectroscopy.

University of Crete

Posted on December 9, 2016 by Niklas Hausmann


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New paper shows the importance of high-res seasonality data

Our paper, Exploring Accumulation Rates of Shell Deposits Through Seasonality Data was recently published in the Journal of Archaeological Method and Theory. It explores the use of seasonality data combined with stratigraphic information to find distinct groups of shells that were deposited (eaten) at the same time and as the same meal.

Finding these pockets of meals will help to reconstruct the temporal scaffolds of shell midden sites.

One necessity for answering these questions is the availability of large amounts of seasonality values. The core objective of the ACCELERATE Project.

Posted on May 16, 2016 by Niklas Hausmann


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GRC Conference Catalunya

Niklas was invited to present a poster at the Gordon Research Conference on Biomineralization in Catalunya (14-19 August). It provides an outline of the project and its application in the future.

Find the full version of the poster here

GRC Conference Catalunya

Posted on August 23, 2016 by Niklas Hausmann


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Presentation at AEA Conference in Orkney

On the 2nd of April, Niklas presented the ACCELERATE project at the AEA conference on Orkney. The 3-day conference was hosted by the University of Highlands and Islands in Scotland and was attended by an international group of environmental Archaeologists. Keynote speaker was the long-term member and emeritus professor Terry O'Connor from the University of York.

GRC Conference Catalunya

Posted on April 3, 2016 by Niklas Hausmann


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Welcome to the Project Website

Here you will find all recent updates on the ACCELERATE Project and also the major research outputs. We aim to add a gallery once the first chapters of the project have been finished.

The first step in the next few weeks is the acquisition of new equipment and material for the laboratories. Exciting times!

Until then!

Niklas

Niklas Hausmann

Posted on April 1, 2016 by Niklas Hausmann


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