δ13C and δ18O-based interpretation of Miocene carbonates of the Miranda-Trebiño basin, NE Iberia: preliminary insights

The stable isotopes (C and O), bulk mineralogy and sedimentary facies types of the Miocene lacustrine palustrine carbonates of the Cucho Section (Miranda-Trebiño basin, N Iberia) are studied. The results indicate deposition in a freshwater carbonate lake recording significant biogenic CO2 input, changing Precipitation/Evaporation rates and variations in vegetation cover and pedogenesis on palustrine areas. Short-lived stages of higher salinity and evaporative conditions are recorded by the relative abundance of fine-grained dolomite. The highest δ13C values suggest 12C sequestration in anoxic bottom waters due to water column stratification. These new data support the general deepening trend of the lake system established from previous sedimentological analyses.