Seep-carbonates in a thrust-related anticline at the leading edge of an orogenic wedge: The case of the middle-late Miocene Salsomaggiore Ridge (Northern Apennines, Italy)

Seep-carbonates are important indicators of seafloor submarine fluid expulsion and dewatering of sediments along convergent margins and accretionary prisms. In the Northern Apennine compressional wedge, seep-carbonates usually occur in pelitic successions from different settings of the middle -late Miocene foreland basin system. In Serravallian foredeep deposits of the Salsomaggiore area, seep-carbonates cemented and/or encrusted coarse-grained sandstones and conglomerates. Fluid expulsion, strictly related to variable intensities in tectonic stresses, generated seep-carbonate facies and sediment instabilities, depending on the position of the fluid-pathway feeders within the Salsomaggiore Ridge, a middle-late Miocene intra-basinal high, at the leading edge of the Apenninic orogenic wedge. This site provides a unique opportunity for analyzing depositional characters, and the three-dimensional distribution and evolution of a seepage system in a thrust-related anticline. The resulting evolutionary model shares common features with recent ridges in other accretionary wedges. In this model a strict relationship between tectonics, seepage and sediment instability during a major orogenytectonic phase is outlined. Because of the concentration of seep-carbonates during the late Serravallian global high-frequency climatic changes, or Miller events, these type of deposits assume a fundamental role to aid in understanding the feed-back between tectonic and climatic processes in convergent margins.