New sediment archive for historical climate research

Date:
October 21, 2020
Source:
Graz University of Technology
Summary:
Geological investigations of low-temperature young deposits on
the Styrian Erzberg provide paleoclimatology with new data on the
Earth's history and its development.



FULL STORY ==========================================================================
How has the climate changed in the course of the earth's history? Which climatic processes have influenced the earth and its atmosphere? Paleoclimatology seeks answers to such questions in order to better
understand climate changes and to derive forecasts for future climate scenarios. So-called sedimentary archives serve as a basis for this. They
are rock deposits whose components and composition provide information
about the temperatures and climatic conditions at the time of their
formation. Correspondingly recent geological deposits provide information
about the climate development in the recent history of the earth since the
last ice age 20,000 years ago. Compared to widespread seawater deposits, however, sedimentary archives on the mainland -- such as in the Alpine
region -- are very rare.


==========================================================================
New data for palaeoclimate research An international consortium led by the Institute of Applied Geosciences (IAG) of Graz University of Technology
has now made a sensational discovery in this area. In a publication for Communications Earth and Environment, the group presents newly discovered, geologically very young deposits on the Styrian Erzberg, whose importance
as a sedimentary archive for paleoclimate research was investigated for
the first time. "The fact that we have now found such young geological deposits, which are usually only found in marine sedimentary archives,
in a continental sedimentary archive is sensational and a treasure trove
of data for climate research," explains the first author of the study,
Andre Baldermann of the IAG.

Low formation temperature and recent deposition age Specifically, these
are sedimentary fillings of faults and fractures which consist of the
carbonate minerals dolomite, aragonite and calcite. It is known that
the carbonate mineral dolomite crystallizes when seawater evaporates,
which in turn requires high temperatures. Baldermann and his team have
now been able to show for the first time that the mineral can also form
at temperatures between zero and twenty degrees Celsius -- there has
been no absolute data on this so far.

In addition, the researchers discovered that these are comparatively geologically young minerals that were formed shortly after the last ice
age about 20,000 years ago in a non-marine (continental) depositional
area.

Baldermann: "This is a novelty, as recent formations of the mineral have
been restricted almost exclusively to seawater deposits until now."
Material analysis through multi-method approach The entire range of
geological investigation methods was used in the analyses.

The rock samples were microscopically described and systematically
classified.

The mineralogical composition was determined by X-ray diffraction and
the chemical properties were defined using high-resolution electron
microscopy. For age dating and temperature reconstructions, the samples
were analysed elementally and isotopically using state-of-the-art
mass spectrometry. "The large number of results allowed us to draw
conclusions about water flow, water composition, mineral growth and
formation temperatures," says Baldermann.

Benefits for climate research "Climate research works mainly by
analysing marine sediments, because we have archived a large number of sediments (marine sediments, note) over the entire course of the earth's history. Continental sedimentary archives are rare and are only very
rarely considered. Their deposits usually provide only little information
about old environmental conditions," says Baldermann. He is convinced
that the newly published data on the deposits on the Erzberg will remedy
this situation and provide new perspectives on climate development of
the recent past.

This research area is anchored in the Field of Expertise "Advanced
Materials Science," one of the five strategic foci of TU Graz.

The work was supported by NAWI Graz Central Lab Water, Minerals and Rocks,
by the mining company VA Erzberg and by researchers from the Universities
of Vienna and Graz. Financial resources were made available from the
European Regional Development Fund (ERDF).


========================================================================== Story Source: Materials provided by
Graz_University_of_Technology. Original written by Christoph Pelzl. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Andre Baldermann, Florian Mittermayr, Stefano M. Bernasconi, Martin
Dietzel, Cyrill Grengg, Dorothee Hippler, Tobias Kluge, Albrecht
Leis, Ke Lin, Xianfeng Wang, Andrea Zu"nterl, Ronny Boch. Fracture
dolomite as an archive of continental palaeo-environmental
conditions. Communications Earth & Environment, 2020; 1 (1) DOI:
10.1038/s43247-020-00040-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201021112324.htm

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