Stratigraphic development of a Late Oligocene Reef Complex under strong fluviatile influence in the Tertiary Piedmont Basin (Liguria, NWItaly)

The modern-day decline of coral reefs due to bleaching events has been recognized as one of the major consequences of man-driven climate change. However, also eutrophication has been highlighted as an equally great danger for coral reefs and as such for biodiversity hotspots. In the latest years this phenomenon has moved to the forefront in the scientific community. Fossil reefs play a key role in studying the emergence, development and faunal/floral diversity of reef environments under eutrophic conditions. Their importance as valuable data sources for studying long-term changes of coral reef environments and their resilience cannot be disputed, especially since they may record the complete life cycle of a reef complex. In this study, nine sections nearby the town of Dego (Savona Province, NW Italy) are presented and discussed with regards to their lithostratigraphic and paleontological contents. Due to the extensive amount of data, the original morphology of a fringing reef, consisting of core, flank and fore reef, under strong fluviatile influence could be reconstructed. This study emphasizes the importance of the coralline red algae association in such biocarbonatic build-ups as major constituent and as substrate stabilizers. The sections record the original colonization event of the local basement by the builder community, the emergence of the coral reef and finally the suffocation by the fluviatile sediments. The variation of the red algae association reflects a deepening trend and is possibly correlated to enhanced fluvial input, which tends to deteriorate ecological conditions and functions as a major trigger for initial reef suffocation.