Bio-retexturing in limestone used in the built heritage of Malta

Abstract

The paper addresses bio-retexturing within the Lower Globigerina Limestone, the limestone used in the construction of the island’s built cultural heritage which dates back to the Neolithic Period. Samples from the host sedimentary layer and burrow infills were analysed to establish the varying petrological, geochemical and mineralogical charcateristics. Petrological examination in thin section indicates that burrowing introduces unlithified sediment in the primary depositional fabric. XRF and XRD indicate that the mineralogy of the infill is qualitatively and quantitatively different from the host rock, often richer in goethite which accounts for its dark yellow ochre colour. Bio-retexturing introduces predominantly non-carbonate rich infill and modifies the original sediment; due to the intra-particle cement, it transforms its permeability and porosity.