Comparison of the Crystallographic Texture of the Recent, Fossil and Subfossil Shells of Bivalves.

The crystallographic texture of modern, subfossil and fossils (Upper Pleistocene) shells of the bivalves Mytilus galloprovincialis, modern and subfossil Mytilus trossulus, as well as modern and fossil (Upper Pleistocene) Ostrea edulis are studied using neutron diffraction. It is revealed that shells of mussel species of different ages are characterized by a high ordering of calcite crystals—a sharp texture. Aragonite crystals are poorly distributed, depending on the shape of the valves. In a warm, dry climate, shells of M. galloprovincialis undergo stratification of the shell matter, which violates the crystallographic texture. Under land conditions, the ordering of calcite crystals in M. galloprovincialis shells decreases. In the subfossil M. trossulus and fossil M. galloprovincialis and O. edulis, the crystallographic texture intensity of the calcite and aragonite changes over hundreds and thousands of years. [ABSTRACT FROM AUTHOR]