Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes
<p>The geochemical conditions conducive to dolomite formation in shallow evaporitic environments along the Triassic Tethyan margin are still poorly understood. Large parts of the Triassic dolomites in the Austroalpine and the southern Alpine realm are affected by late diagenetic or hydrotherma...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-07-01
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| Series: | Solid Earth |
| Online Access: | https://www.solid-earth.net/10/1243/2019/se-10-1243-2019.pdf |
| _version_ | 1819103156052688896 |
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| author | M. Rieder W. Wegner M. Horschinegg S. Klackl N. Preto A. Breda S. Gier U. Klötzli S. M. Bernasconi G. Arp P. Meister |
| author_facet | M. Rieder W. Wegner M. Horschinegg S. Klackl N. Preto A. Breda S. Gier U. Klötzli S. M. Bernasconi G. Arp P. Meister |
| author_sort | M. Rieder |
| collection | DOAJ |
| description | <p>The geochemical conditions conducive to dolomite formation in
shallow evaporitic environments along the Triassic Tethyan margin are still
poorly understood. Large parts of the Triassic dolomites in the Austroalpine
and the southern Alpine realm are affected by late diagenetic or
hydrothermal overprinting, but recent studies from the Carnian Travenanzes
Formation (southern Alps) provide evidence of primary dolomite. Here a
petrographic and geochemical study of dolomites intercalated in a
100 <span class="inline-formula">m</span> thick Carnian sequence of distal alluvial plain deposits is presented
to gain better insight into the conditions and processes of dolomite
formation. The dolomites occur as 10 to 50 <span class="inline-formula">cm</span> thick homogeneous beds,
millimetre-scale laminated beds, and nodules associated with palaeosols. The
dolomite is nearly stoichiometric with slightly attenuated ordering
reflections. Sedimentary structures indicate that the initial primary
dolomite or precursor phase consisted largely of unlithified mud. Strontium
isotope ratios (<span class="inline-formula"><sup>87</sup>Sr∕<sup>86</sup>Sr</span>) of homogeneous and laminated dolomites
reflect Triassic seawater composition, suggesting precipitation in
evaporating seawater in a coastal ephemeral lake or sabkha system. However,
the setting differed from modern sabkha or coastal ephemeral lake systems by
being exposed to seasonally wet conditions with significant siliciclastic
input and the inhibition of significant lateral groundwater flow by
impermeable clay deposits. Thus, the ancient Tethyan margin was different
from modern analogues of primary dolomite formation.</p> |
| first_indexed | 2024-12-22T01:45:58Z |
| format | Article |
| id | doaj.art-4c404e01d09b4a48a665f91b2ab27327 |
| institution | Directory Open Access Journal |
| issn | 1869-9510 1869-9529 |
| language | English |
| last_indexed | 2024-12-22T01:45:58Z |
| publishDate | 2019-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Solid Earth |
| spelling | doaj.art-4c404e01d09b4a48a665f91b2ab273272022-12-21T18:43:05ZengCopernicus PublicationsSolid Earth1869-95101869-95292019-07-01101243126710.5194/se-10-1243-2019Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopesM. Rieder0W. Wegner1M. Horschinegg2S. Klackl3N. Preto4A. Breda5S. Gier6U. Klötzli7S. M. Bernasconi8G. Arp9P. Meister10Department of Geodynamics and Sedimentology, University of Vienna, Althanstr. 14, 1090 Vienna, AustriaDepartment of Lithospheric Research, University of Vienna, Althanstr. 14, 1090 Vienna, AustriaDepartment of Lithospheric Research, University of Vienna, Althanstr. 14, 1090 Vienna, AustriaDepartment of Geodynamics and Sedimentology, University of Vienna, Althanstr. 14, 1090 Vienna, AustriaDepartment of Geosciences, University of Padua, Via Gradenigo 6, 35131 Padua, ItalyDepartment of Geosciences, University of Padua, Via Gradenigo 6, 35131 Padua, ItalyDepartment of Geodynamics and Sedimentology, University of Vienna, Althanstr. 14, 1090 Vienna, AustriaDepartment of Lithospheric Research, University of Vienna, Althanstr. 14, 1090 Vienna, AustriaGeological Institute, ETH Zürich, Sonneggstr. 5, 8092 Zurich, SwitzerlandGeoscience Centre, University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, GermanyDepartment of Geodynamics and Sedimentology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria<p>The geochemical conditions conducive to dolomite formation in shallow evaporitic environments along the Triassic Tethyan margin are still poorly understood. Large parts of the Triassic dolomites in the Austroalpine and the southern Alpine realm are affected by late diagenetic or hydrothermal overprinting, but recent studies from the Carnian Travenanzes Formation (southern Alps) provide evidence of primary dolomite. Here a petrographic and geochemical study of dolomites intercalated in a 100 <span class="inline-formula">m</span> thick Carnian sequence of distal alluvial plain deposits is presented to gain better insight into the conditions and processes of dolomite formation. The dolomites occur as 10 to 50 <span class="inline-formula">cm</span> thick homogeneous beds, millimetre-scale laminated beds, and nodules associated with palaeosols. The dolomite is nearly stoichiometric with slightly attenuated ordering reflections. Sedimentary structures indicate that the initial primary dolomite or precursor phase consisted largely of unlithified mud. Strontium isotope ratios (<span class="inline-formula"><sup>87</sup>Sr∕<sup>86</sup>Sr</span>) of homogeneous and laminated dolomites reflect Triassic seawater composition, suggesting precipitation in evaporating seawater in a coastal ephemeral lake or sabkha system. However, the setting differed from modern sabkha or coastal ephemeral lake systems by being exposed to seasonally wet conditions with significant siliciclastic input and the inhibition of significant lateral groundwater flow by impermeable clay deposits. Thus, the ancient Tethyan margin was different from modern analogues of primary dolomite formation.</p>https://www.solid-earth.net/10/1243/2019/se-10-1243-2019.pdf |
| spellingShingle | M. Rieder W. Wegner M. Horschinegg S. Klackl N. Preto A. Breda S. Gier U. Klötzli S. M. Bernasconi G. Arp P. Meister Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes Solid Earth |
| title | Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes |
| title_full | Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes |
| title_fullStr | Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes |
| title_full_unstemmed | Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes |
| title_short | Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes |
| title_sort | precipitation of dolomite from seawater on a carnian coastal plain dolomites northern italy evidence from carbonate petrography and sr isotopes |
| url | https://www.solid-earth.net/10/1243/2019/se-10-1243-2019.pdf |
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