Processes and quantification of CaCO3 fabric-specific layering at hot springs and its environmental implications
Continental carbonate spring deposits can be sensitive records of terrestrial environmental changes due to their very fast CaCO3 precipitation rates and different scales of banding (‘layering’). This study focuses on changes in CaCO3 fabrics and mineralogy that result in typical travertine layering in both recent and ancient deposits. The layered nature has been linked to changes in water composition, precipitation rate or the nature and activity of organisms inhabiting the springs. These parameters, on their turn, may reflect environmental changes. We investigate how changes in temperature, water composition, flow and presence of micro-organisms affects fabrics at micron- to decimeter scale, resulting in travertine laminae. In addition, the impact of early diagenesis on crystal texture and preservation of geochemical signals is addressed. To achieve this, we apply detailed field monitoring of springs and carbonate precipitation (suite of water chemistry parameters, precipitation rates) together with controlled, laboratory experiments and petrography, 3D micro-CT imaging, carbonate geochemistry and mineralogy. The results will finally be used to verify carbonate precipitation rate laws for conditions representative of terrestrial carbonate spring systems where the presence and activity of biota may play a role.
Funding : SNSF Ambizione