Projects / Programmes
Terrestrial carbonates: mineral products of geobiological processes in the critical zone
| Code |
Science |
Field |
Subfield |
| 1.06.00 |
Natural sciences and mathematics |
Geology |
|
| Code |
Science |
Field |
| P005 |
Natural sciences and mathematics |
Geology, physical geography |
| Code |
Science |
Field |
| 1.05 |
Natural Sciences |
Earth and related Environmental sciences |
Terrestrial carbonates, Critical zone, Geobiology, Sedimentology, Fibrous microcrystalline calcite, Calcretes, Speleothems,Metagenomics
Researchers (8)
Organisations (2)
Abstract
The proposed project deals with a large group of terrestrial carbonate deposits, which form in soils and caves through a variety of physical, chemical, biological and geological processes that operate at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. The studied interface corresponds to the unsaturated (vadose) belowground part of the Critical Zone – a system defined from the outer extent of vegetation down to the lower limits of groundwater.
The project will focus on fibrous microcrystalline calcite (FMC), one of the most common and widespread forms of secondary calcium carbonate in vadose terrestrial environments (caves, soils, surficial sediments.). FMC is characterized by nonequilibrium crystal shapes composed of low-Mg calcite. The origin of FMC crystals has generally been attributed either to purely physicochemical processes or to microbial biomineralisation. The current biogenic hypotheses are largely based on common co-occurrence of fibrous calcite and microbial features, and the similarity in dimensions and morphology of calcite fibres and fungal hyphae and filamentous bacteria. Morphological arguments for biogenicity have been supported by geochemical and petrographic data, considered as biosignatures preserved in certain forms of FMC.
The purpose of the proposed project is to examine precipitation mechanisms of FMC using in-situ and laboratory investigation of calcite moonmilk speleothems, actively precipitating Slovenian karst caves, and analogous deposits from a fundamentally different setting – Mediterranean calcareous soils and calcretes. The research is aimed at testing a hypothesis that FMC may form through non-classical crystal growth pathways. The main objectives are: 1) to perform a comparative micromorphological study of fibrous microcrystalline calcite from a maximum diversity of terrestrial settings; 2) to extract an characterise extracellular polymeric substances (EPS) present in FMC sediment interstitial waters; 3) to analyse stable isotopes of carbon and oxygen of FMC samples from different microenvironments; 4) to perform microbiological characterisation of cave and soil FMC deposits using environmental metagenomics; and 5) to test crystallisation processes of FMC in vitro in the presence of previously identified polymers.
The anticipated study sites in Slovenian caves are targeted because they include all different microenvironments of FMC precipitation. All the caves is close to the laboratory and easily accessible throughout the year and will be used as a main field site for regular sampling of water and mineral precipitates, as well as for continuous microclimate determination. Comparative material will be provided from Mediterranean regions, known for active accumulations of FMC carbonates in extensive root systems.
The research will contribute to the understanding of fundamental principles of calcium carbonate deposition in near-surface terrestrial settings, an inherent subject of sedimentology. The addressed problems are on the interface of several scientific fields from geomicrobiology, cave & karst studies, soil science, and crystallography: expected results will thus bear significance in all these disciplines.
Significance for science
The proposed research will contribute to the understanding of fundamental principles of calcium carbonate deposition in near-surface terrestrial settings, an inherent subject of sedimentology. The addressed problems are on the interface of several scientific fields from geomicrobiology, cave & karst studies, soil science, and crystallography: expected results will thus bear significance in all these disciplines.
The approach of the proposed project is specific in entering a largely unexplored gap between pure biogenic and inorganic models of precipitation of fibrous microcrystalline carbonates. One of the aims of the project is to strengthen the perception of non-classical crystallisation mechanisms in natural, geological settings.
Methodologically, the project will introduce an integrated geobiological approach to the study of moonmilk speleothems and biologically-induced accumulations of calcium carbonate in modern soils. Part of the project will be dedicated to development of modified cryogenic techniques applied to particularly problematic geobiological materials, such as calcite moonmilk, which are predominantly composed of water and with only minor inorganic, hard matter, embedded in organic matrices.
Geobiological research of calcretes is aimed to contribute a broader understanding of carbonate formation in soils, influenced by a specific climate (palaeoclimate) and vegetation in the Mediterranean region.
The proposed research can have a significant impact in its results of crystallisation mechanisms of microcrystalline fibrous calcite that can be potentially applied to climate change mitigation through removal of atmospheric CO2 in soil carbonates. Namely, recent studies have shown an immense potential of CO2 sequestration by enhanced precipitation of Ca carbonates in artificial soils.
The results will also provide a basis for the evaluation of geological sites in the studied caves in terms of their conservation, protection and educational value. These will be focused on identification and conservation of cave sediments of specific scientific importance.
The study sites in karst caves are formally protected, therefore our research activities will be coordinated with the Nature Protection Institute and the national Environmental Agency and will follow initiatives and concepts of forums such as the European Association for the Conservation of the Geological Heritage. The proposed research plan has already been approved by the Nature Protection Institute of the Republic of Slovenia.
Finally, the project is aimed at introducing the concept of the Critical Zone to geological community and society in general.
Significance for the country
The proposed research will contribute to the understanding of fundamental principles of calcium carbonate deposition in near-surface terrestrial settings, an inherent subject of sedimentology. The addressed problems are on the interface of several scientific fields from geomicrobiology, cave & karst studies, soil science, and crystallography: expected results will thus bear significance in all these disciplines.
The approach of the proposed project is specific in entering a largely unexplored gap between pure biogenic and inorganic models of precipitation of fibrous microcrystalline carbonates. One of the aims of the project is to strengthen the perception of non-classical crystallisation mechanisms in natural, geological settings.
Methodologically, the project will introduce an integrated geobiological approach to the study of moonmilk speleothems and biologically-induced accumulations of calcium carbonate in modern soils. Part of the project will be dedicated to development of modified cryogenic techniques applied to particularly problematic geobiological materials, such as calcite moonmilk, which are predominantly composed of water and with only minor inorganic, hard matter, embedded in organic matrices.
Geobiological research of calcretes is aimed to contribute a broader understanding of carbonate formation in soils, influenced by a specific climate (palaeoclimate) and vegetation in the Mediterranean region.
The proposed research can have a significant impact in its results of crystallisation mechanisms of microcrystalline fibrous calcite that can be potentially applied to climate change mitigation through removal of atmospheric CO2 in soil carbonates. Namely, recent studies have shown an immense potential of CO2 sequestration by enhanced precipitation of Ca carbonates in artificial soils.
The results will also provide a basis for the evaluation of geological sites in the studied caves in terms of their conservation, protection and educational value. These will be focused on identification and conservation of cave sediments of specific scientific importance.
The study sites in karst caves are formally protected, therefore our research activities will be coordinated with the Nature Protection Institute and the national Environmental Agency and will follow initiatives and concepts of forums such as the European Association for the Conservation of the Geological Heritage. The proposed research plan has already been approved by the Nature Protection Institute of the Republic of Slovenia.
Finally, the project is aimed at introducing the concept of the Critical Zone to geological community and society in general.
Most important scientific results
Interim report
Most important socioeconomically and culturally relevant results
