DEPOSITIONAL AND DIAGENETIC FACTORS AFFECTING THE DEVELOPMENT OF BED-PARALLEL, BURIAL-RELATED STRUCTURES IN OLIGO-MIOCENE RAMP CARBONATES (MAIELLA MOUNTAIN, CENTRAL ITALY)

Bed-parallel pressure solution seams and compaction bands represent structural elements that may form, due to a vertical loading, in carbonate rocks under diagenetic and low grade metamorphic conditions. In the present contribution, we present the results of an integrated field and laboratory study conducted on Oligo-Miocene skeletal grainstones to mudstones of the Bolognano Formation, which crops out in the Maiella Mountain, Central Italy. These rocks were deposited on a carbonate ramp. The results of this work are consistent with the following statements: (i) bed-parallel compaction bands formed only within poorly cemented, porous grainstones (now days porosity > 15%); (ii) distribution of the bed-parallel compaction bands was strongly controlled by intergranular porosity, which depended on sorting of the skeletal grains which constitute the rock; (iii) bed-parallel pressure solution seams formed, predominantly, within carbonate grainstones and packstones characterized by small amounts of clay (2-4% of the total rock volume), and fine, well-sorted, spherical carbonate grains. Considering the depositional settings of the carbonates studied, bed-parallel compaction bands formed, predominantly, in carbonates deposited in high-energy, shallow-water sectors of carbonate ramps. On the contrary, carbonates pervasively crosscut by bed-parallel pressure solution seams were deposited in transitional zones lying between the high- and low-energy sectors of the same ramps. This suggests a strong link between the paleo-depositional environments, biological, depositional and diagenetic processes responsible for compositional, sedimentological and pore network characteristics of the carbonates under study and the relative formation and distribution of burial-related, bed-parallel structures.