The long term preservation of late jurassic sandstone dinossaur footprints in a museum environment

This study focuses on the assessment of the degradation processes occurring in three sandstone infills of fossilized Late Jurassic ornithopod tridactyl footprints, found in 2001 in a coastline cliff in Porto das Barcas (Lourinha, Portugal) and exhibited in a museum display since 2004. These dinosaur footprints present nowadays severe decay phenomena compromising their physical integrity and leading gradually to their loss of value. The deterioration patterns were recorded, a map of their distribution was prepared and several samples were collected both in the dinosaur footprints and in the coastline cliff. Different analytical procedures were applied such as XRD, FTIR, FESEM and Ion Chromatography. A microclimatic survey was also performed and air temperature and relative humidity were measured during eight months both indoors and also outdoors. The decay patterns observed are a combination of intrinsic and extrinsic factors: the stone material, namely the swelling of clay minerals in the rock matrix(smectite and chlorite-smectite mixed-layer), the presence of salts (mainly chlorides), the application of past conservation treatments (poly(vinyl) acetate and epoxy resins) and the indoor thermohygrometric conditions (mainly non-stable hygrometric conditions) of the museum. This scientific knowledge is therefore essential to the sustainable preservation of this paleontological heritage.