Exploring the potential of moonmilk speleothems as archives of palaeo-environmental information

Moonmilk is an intriguing cave deposit that has a soft, plastic texture composed of two types of fibrous calcite crystals: needle fibre calcite and calcite nanofibres. These crystals create a 3D-mesh with extremely high porosity, giving moonmilk a water content of up to 95wt%.

The exact mode of formation of moonmilk is still elusive, and thus, a large part of this project is dedicated to understanding the environmental, geochemical and microbiological conditions under which it is formed.

An important property of moonmilk speleothems is their potential to retain palaeo-environmental information. Such information is critical to reconstruct palaeoclimate, which is essential to our understanding of how the environment responds to different climate modes and forcing mechanisms. Moonmilk has been mostly overlooked as a possible palaeo-environmental archive, in part due to a lack of understanding as to how environmental signals are encoded and preserved in this deposit.

Through the study of cave climate, water and rock geochemistry, petrography (micromorphology) and microbiology of active and inactive moonmilk deposits, we will explore the potential of this fascinating material as a new archive of palaeo-environmental information and investigate how diagenetic pathways may affect proxy signals. With data obtained from caves at various altitudes, reflecting various temperatures, we will gain a more complete understanding of the conditions required for moonmilk formation and how these reflect environmental changes.

Key words: carbonate speleothems, palaeoclimate, needle fibre calcite, geochemistry, cave monitoring, microscopy, geomicrobiology.