Widespread cementation induced by inflow of continental water in the eastern part of the Paris basin: O and C isotopic study of carbonate cements

Mesozoic limestones from the eastern part of the Paris Basin display, mostly in strata rich in bioherms, abundant macro-cavities (vugs) and some connected micro-fractures almost completely filled with euhedral calcite crystals (late calcite spar). The interparticle porosity of limestones is also filled with euhedral calcite spar cements similar to those observed in vugs and fractures, and rarely displays the preservation of the structures typical of early marine cements. These calcite spars (both from vugs/fractures infillings and from cemented porosity) were studied in drilled cores cross-cutting the Kimmeridgian to Bathonian series with the main objective of determining the nature and flow regime of the fluids responsible for the strong porosity reduction observed in that part of the Paris Basin Mesozoic limestones. The approach combined mineralogical and geochemical studies (O and C stable isotopic compositions measured by conventional and SIMS methods) with temperature estimates from fluid inclusion analyses.