Perfiles geoquímicos y luminiscencia en las cámaras y concha de Crassostrea sp. de la Formación Zufía, Navarra (Albiense superior-Cenomaniense inferior). Parte II

Abstract

Shells of the oyster Crassostrea sp. from the Zufia Formation show chambers filled with different diagenetic carbonates that record a complex diagenetic history. Evidences of «burial» diagenesis, represented by the formation of ferrous «saddle» dolomite, suggest high formation temperatures. However, the absence of dissolution/recrystallization features in the Regular Foliated microstructure (RF) indicates its remarkable resistance to diagenetic alteration. Avoiding the camouflage of diagenetic signals, such microstructure is therefore the propitious one to undertake geochemical studies when searching for environmental information. After the «burial» diagenesis stage, an «uplift» process was experienced, characterized by the influence of more aggressive, meteoric fluids with lower Fe and Mn concentrations. As a consequence, pressure-solution textures were developed in the contact Ds and RF. Likewise, a dedolomitization process, progressing from the walls of the cameras to the center, originated the calcitic late digenetic stages C1, C2 and C3