Abstract Most buildings of architectural heritage in Paris and its surroundings are built with Lutetian limestone. Several historic buildings of the ‘Vexin Normand’ region show Lutetian limestone in the upper parts of their walls, while the lower parts are built with a chalk known as ‘Pierre de Vernon’. The ‘Pierre de Vernon’ appears up to the first metre, although in exceptional cases it can reach the middle height of a building. Commonly, chalks exhibit low durability due to their high porosity. However, ‘Pierre de Vernon’ is supposed to have greater durability than other chalks because of its historic use for basement construction. The objective of this research was to understand the use of the ‘Pierre de Vernon’ in the lower part of the constructions. A petrophysical characterization of Vernon chalk and Lutetian limestone was carried out, focusing mainly on the differences in porosity and water uptake. Salt crystallization tests were done to contrast their response to decay. Colour and roughness measurements and scanning electron microscope observations were performed. Results show that the different porous networks of these two limestones lead to a high contrast in their hydric properties and responses to decay, and the use of Vernon chalk in the lower sections of buildings has been found to be appropriate.

Abstract Organo-clay fabric and physico-chemistry of marine mud play important roles in early sediment diagenesis including the development of mass physical properties, consolidation behavior, and sequestration of organic matter (OM) in sediments over geologic time. Transmission electron microscopy (TEM) images of nano- and microfabric reveal that organic matter is sequestered following enzymatic digestion despite the pervasive openness of pore-fluid pathways observed in 3D rotated images. The locations of sequestered organic matter correspond to those predicted by modeling of the potential energy of interaction. Initial flume experiments on high porosity clay-mineral-rich mud deposited under dynamic flow and static (vertical settlement) conditions demonstrate differences in clay fabric and the distribution of organic matter (we define the term organo-clay fabric as the contiguous association and arrangement of organic matter and clay domains). These differences in organo-clay fabric impact the preservation-degradation mechanisms and dynamics during depositional and burial processes. Organo-clay fabric and physico-chemical modeling of potential energy fields coupled with direct observations of organo-clay fabric, three-dimensional (3-D) clay fabric reconstructions, sediment static and dynamic properties, and controlled flume experiments are providing new insight into the developmental history of sedimentary sequences, nano- to macroscale environmental processes, and diagenesis from unconsolidated mud to shale.