Late Barremian–early Aptian ammonite bioevents from the Urgonian-type series of Provence, southeast France: Regional stratigraphic correlations and implications for dating the peri-Vocontian carbonate platforms

摘要

This work provides a new ammonite age-calibration of the rudistid limestones of the Urgonian-type Provence carbonate platform (Southeast France) based on sampling along three ～200?km-long platform-to-basin transects and re-examination of historical collections. Ammonite key findings indicate that the first rudistid platform stage (including theAgriopleuraand requieniid–monopleurid beds) develops and spreads northward through theToxancyloceras vandenheckii–Gerhardtia sartousianazones interval (lower upper Barremian). This stage is interrupted by the tectonically-induced deepening of the southern Provence domain during theImerites giraudiZone while the northern regions records the massive deposition ofPalorbitolina–Heterasterbeds. Recovery of the rudistid carbonate system is illustrated by the development of caprinid-bearing rudistid limestones in the North Provence domain through theMartelites sarasiniSubzone (lowerMartelites sarasiniZone, uppermost Barremian), which shows a bidirectional progradation toward the South Provence and Vocontian basins. The caprinid-bearing limestones terminate at a short-term exposure and are overlain by cherty–oobioclastic deposits spanning thePseudocrioceras waagenoidesSubzone (upperM.?sarasiniZone) to the lowerDeshayesites forbesiZone. A regional-wide flooding of the study area is illustrated by the abrupt change to a marl-dominated regime occurring in the upperD.?forbesiZone. Compared to the previous datings, the Barremian/Aptian boundary should be relocated in the lower part of the post-caprinid, cherty–oobioclastic deposits although its precise level cannot be fixed due to the lack of a continuous ammonite record. Ammonite age-calibration of the surrounding Urgonian rudistid platform series is discussed and gives evidence of a comparable twofold demise of the peri-Vocontian rudistid biota during the uppermost Barremian. Accordingly, the link between the final demise of the peri-Vocontian rudistid biota and the onset and/or cu