 |
| Titel |
The magnesium isotope record of cave carbonate archives |
| VerfasserIn |
S. Riechelmann, D. Buhl, A. Schröder-Ritzrau, D. F. C. Riechelmann, D. K. Richter, H. B. Vonhof, J. A. Wassenburg, A. Geske, Christoph Spötl, A. Immenhauser |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1814-9324
|
| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 6 ; Nr. 8, no. 6 (2012-11-20), S.1849-1867 |
| Datensatznummer |
250005973
|
| Publikation (Nr.) |
 copernicus.org/cp-8-1849-2012.pdf |
|
|
|
| Schlagwörter |
Speläologie, Höhle, Stalagmit, Paläoklima, Klimarekonstruktion, Isotope, Magnesiumisotop, Isotopenanalyse, Geochemie, Speläothem |
| Geograf. Schlagwort |
International, Österreich, Tirol, Schwaz (Bezirk), Spannagelhöhle, Tuxer Alpen, Deutschland, Peru, Marokko |
| Blattnummer |
149 [Lanersbach] |
| Blattnummer (UTM) |
2230 [Mayrhofen] |
|
|
|
|
|
| Zusammenfassung |
| Here we explore the potential of magnesium (δ26Mg) isotope
time-series data as continental climate proxies in speleothem calcite
archives. For this purpose, a total of six Pleistocene and Holocene
stalagmites from caves in Germany, Morocco and Peru and two flowstones from
a cave in Austria were investigated. These caves represent the semi-arid to
arid (Morocco), the warm-temperate (Germany), the equatorial-humid (Peru)
and the cold-humid (Austria) climate zones. Changes in the calcite magnesium
isotope signature with time are compared against carbon and oxygen isotope
records from these speleothems. Similar to other proxies, the non-trivial
interaction of a number of environmental, equilibrium and disequilibrium
processes governs the δ26Mg fractionation in continental
settings. These include the different sources of magnesium isotopes such as
rainwater or snow as well as soil and host rock, soil zone biogenic
activity, shifts in silicate versus carbonate weathering ratios and
residence time of water in the soil and karst zone. Pleistocene stalagmites
from Morocco show the lowest mean δ26Mg values (GDA: −4.26 ± 0.07‰ and HK3: −4.17 ± 0.15‰), and the data are well explained in
terms of changes in aridity over time. The Pleistocene to Holocene
stalagmites from Peru show the highest mean value of all stalagmites (NC-A
and NC-B δ26Mg: −3.96 ± 0.04‰) but only minor variations
in Mg-isotope composition, which is consistent with the rather stable
equatorial climate at this site. Holocene stalagmites from Germany (AH-1
mean δ26Mg: −4.01 ± 0.07‰; BU 4 mean δ26Mg:
−4.20 ± 0.10‰) suggest changes in outside air temperature was the
principal driver rather than rainfall amount. The alpine Pleistocene
flowstones from Austria (SPA 52: −3.00 ± 0.73‰; SPA 59: −3.70 ± 0.43‰) are affected by glacial versus interglacial climate change with
outside air temperature affecting soil zone activity and weathering balance.
Several δ26Mg values of the Austrian and two δ26Mg
values of the German speleothems are shifted to higher values due to
sampling in detrital layers (Mg-bearing clay minerals) of the speleothems.
The data and their interpretation shown here highlight the potential but
also the limitations of the magnesium isotope proxy applied in continental
climate research. An obvious potential lies in its sensitivity for even
subtle changes in soil-zone parameters, a hitherto rather poorly understood
but extremely important component in cave archive research. Limitations are
most obvious in the low resolution and high sample amount needed for
analysis. Future research should focus on experimental and conceptual
aspects including quantitative and well-calibrated leaching and
precipitation experiments. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|