Moonmilk is a well-known carbonate speleothem mainly consisting of calcite and other CaCO3 polymorphs with varying crystal morphology that forms on the walls of natural and anthropogenic underground environments, especially those found in carbonate bedrock. The genesis of moonmilk is poorly understood, both abiotic and biogenic processes may contribute to its formation, but a large number of studies demonstrated that the metabolic activity of microbial communities plays a major role in the minerogenesis of such deposits. However, the physicochemical properties of the host rocks significantly affect the moonmilk formation regulating the environmental conditions under which the bacterial communities grow as well as influencing the mineral composition of speleothems. Close to the town of Tarquinia (Central Italy), the area where is located the Etruscan necropolis of Monterozzi hosts numerous hypogean environments where moonmilk speleothems diffusively proliferate. Due to the heterogeneous lithology of bedrock (Macco Formation), consisting of calcarenite and hybrid sandstone, this restricted area offers a favourable chance to investigate the role of bedrock in the genesis of the moonmilk.
The main goals of this project are: 1) to provide a stratigraphic reconstruction of the Macco Formation and a detailed characterization of the main lithofacies in terms of mineral, chemical and C, O, Sr and Ca isotopic composition and physical properties also to support the archaeological studies and the restoration works on the Monterozzi necropolis; 2) to analyse the morphological, mineralogic and chemical features of the moonmilk concretions in relation to the variable physicochemical characters of the geologic substrate in order to also achieve a better understanding of how all these parameters can influence the microbial ecology.
