Optical parameters of maturity of organic matter dispersed in sediments: first results from the Central Apennines (Italy)

Levels of organic maturity of Mesozoic and Tertiary sequences outcropping in the Central Apennines have been established, using vitrinite reflectance techniques, the Thermal Alteration Index and fluorescence colours of organic matter dispersed in sediments. These results provide new constraints throughout the Meso-Cenozoic evolution of this crustal sector. The pre-terrigenous Meso-Cenozoic sequences show a low grade of organic maturity. Field analysis indicates that the cause of these low maturity levels is that thick sequences of turbidites were never deposited during the Neogene evolution of the Apennine thrust belt. Moreoever, Upper Miocene turbiditic deposits also show low maturity levels, with Ro values that are less than 0.5%, indicating that these dpeosits were never overthrusted by huge volumes of rocks, during the chain building. The slight increase in the maturity level recorded in the Marsica area may be related to local heating, along shear zones in areas of strike-slip tectonics.