LOWER MIOCENE GLAUCONY-BEARING DEPOSITS IN THE SE-TERTIARY PIEDMONT BASIN (NORTHERN ITALY)

The sedimentological, mineralogical and geochemical characterization o f glaucony from the Lower Miocene formations of the Alto Monferrato (T ertiary Piedmont Basin) allows two populations of grains to be clearly differentiated on the basis of marked differences in terms of genetic attributes, maturity, and composition. Glaucony associated with conde nsed, outer-shelf arenites (Visone Formation) has a predominantly auto chthonous origin, high maturity and displays the typical association w ith phosphate grains. In contrast, glaucony associated with turbidite arenites ('Marly Unit') is allochthonous, poorly evolved and has a dis tinctive geochemical signature. The differentiation of glaucony associ ated with outer-shelf and deep-marine deposits, respectively, document s the intrasequential variability of glaucony characteristics as a fun ction of the complex relationships among glauconitization, transport, and reworking processes. Characterization of glaucony attributes provi des an example of the possible use of glaucony for basin analysis and provenance studies.