In situ <scp>U–Pb</scp> geochronology of Pre?Salt carbonates reveals links between diagenesis and regional tectonics

Identification of processes driving carbonate diagenesis requires an accurate chronology, particularly along volcanic margins where complex mineral parageneses develop. The Cretaceous “Pre-Salt” carbonates formed in the proto-South Atlantic and are now extensive hydrocarbon reservoirs offshore Brazil Angola. Primary diagenetic textures strongly affect reservoir properties, but timings deposition (c. Barremian–early Aptian) poorly constrained. This study provides first direct age measurements from Pre-Salt using situ U–Pb geochronology. Depositional calcites Santos Basin (Brazil) do not preserve depositional ages, instead yielding Albian recrystallization 106.9 ± 4.3 Ma. Dolomite rhombs bridges have Palaeocene ages 59.2 5.3 Ma, 58.0 4.6 respectively. Calcite was linked to onset oceanic spreading South Atlantic. Contrary existing models, dolomites much later, during a time enhanced tectono-magmatism southeastern Brazil.