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In this contest, chemoherms seem to be indicators of the advancing deformational front of the chain, thus heralding main tectonic phases.

Sandstones sampled are from five upper Eocene to Pliocene clastic units deposited in a piggy-back setting and from one Miocene unit in the foreland basin of the northern Apennines.

The intergranular volume of the sandstones indicates that in younger piggy-back units calcite cement was introduced after maximum burial or nearly so, whereas in older and more deeply buried piggy-back and foreland units minor compaction continued in host sandstones after concretion growth stopped.

The concretions differ little from their host sandstones in bulk framework composition, abundance of detrital carbonate grains, and chemistry of feld-spars.

The sandstones have a lithic composition, characterized by abundant sedimentary and metasedimentary rock fragments (35-56% of the terrigenous framework), little feldspar (Micritic limestones locally called "calcari a Lucina" packed with dense large bivalves and characterized by autoclastic breccias and fluid-flow conduits are present in middle-late Miocene sediments of the northern Apennines.

After many years of geologic controversies, these limestones have been reinterpreted as cold vent deposits, thus becoming special indicators of clathrate dissociation and revealing important relationships between methane seepages, sediment instability, and tectonics.

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