Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

the specificity of the LIP group is its 30 years of innovations

and experience in AMS, while being the

largest European tandem accelerator with a broad

AMS program in the European scientific landscape.

International Cooperation

Our group has several projects in collaboration

with international institutions. We are collaborating

with the Norwegian Geological Survey (NGU),

Norway, and the Istanbul Technical, the Tunceli,

the Ankara and the Hacettepe Universities in Turkey.

These projects focus on the dating of several

Quaternary deposits in different geological settings

(e.g. alluvial fans) with different approaches

of cosmogenic nuclide dating (burial, isochronburial,

depth-profile dating). Here we underline

our project with the Ankara and the Hacettepe

Universities. Within this collaboration, we recently

dated two fluvial terraces in Central Turkey with

isochron-burial dating to 140 ± 30 ka and 1030 ±

230 ka. These are our first isochron-burial ages and

show that this approach may work in the dating of

fluvial deposits (s.l.).

With these collaborations, we are improving and

refining our technique, and this know-how is directly

transferred into our project.

Assessment 2012 and

Perspectives for 2013

As our project has only run for three months in

2012, we successfully started our project and one

PhD candidate with a surface exposure dating

background is allocated. All the conditions were

optimal for this period.

In addition to the continued literature review by

PhD candidate Anne Claude, our work in 2013

will focus on site selection and optimization of 10 Be

and 26 Al determinations.

In early 2013, a meeting of all involved parties

will take place. The key issue is selection of sampling

sites. Criteria include not only importance

with respect to «the timing of Deckenschotter deposition»

but also matching of site character to

the requirements of each dating method (burial,

isochron-burial and depth-profile dating). For example,

the latter does require an upper surface of

the deposit which is as unmodified as possible (socalled

«flat top») and a sampling site that is tens

of meters away from any fluvial incision or slope

instability along the sides of the landform.

For the reasons described above optimization of

26

Al is critical. Improvements in 26 Al capabilities are

underway and discussed in detail at LIP, this project

does indicate the clear need for these capabilities.

Our work will proceed on three fronts:

1. Accuracy of ICP-MS 27 Al measurements must

be checked with known Al content quartz standards.

(Note ICP-MS itself attains excellent precision,

it is the accuracy in the frame-work of our

extraction procedures that must be looked into),

2. Purity of the Al 2 O 3 delivered to the ETH accelerator

facility must be checked (ICP-MS),

3. Tests to increase ion source currents for Al at the

6 MV tandem are now being performed.

4. Changes to the detection system on the 0.5 MV

Tandy accelerator are being made to allow 26 Al

measurements on the smaller machine in addition

to on the 6 MV tandem.

We will work closely with LIP, especially the PhD

student, to ensure that optimizations are directly

applicable to this project.

As we employ a three-pronged approach: burial,

isochron-burial and depth-profile dating, we have

flexibility and can adjust as results are obtained.

With careful site selection, depth-profile dating

is not expected to be problematic. As described

above, certain challenges are required for burial

and isochron-burial dating. These challenges are

mainly related to the optimization of 26 Al measurements.

Depending on the requirements of the

approach, candidate sites will be evaluated, and

the best will be selected for sampling. The first

sampling campaign will be in the first half of 2013.

In late 2013, we will meet for the second time in

order to evaluate the first results and assess the

improvements and «to do list» for the next steps.

Publications

Akçar N., Ivy-Ochs S., Alfimov V., Graf H.R.,

Kubik P.W., Rahn M., Kuhlemann J., Schlüchter

C. in preparation. End of Deckenschotter Glaciations

in the Swiss Alps.

Claude A., Akçar N., Ivy-Ochs S., Graf H.R., Kubik

P.W., Vockenhuber C., Dehnert A., Rahn M.,

Schlüchter C. submitted. Cosmogenic nuclide

dating of Swiss Deckenschotter. The 8 th International

Conference on Geomorphology of the

International Association of Geomorphologists,

abstract for poster presentation.

ENSI Erfahrungs- und Forschungsbericht 2012 285

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