A new sediment core from the Bedoulian (Lower Aptian) stratotype at Roquefort-La Bédoule, SE France

► New sediment cores from La Bédoule (SE France) resolve onset of OAE1a in unprecedented resolution. ► δ13C data confirm expanded negative excursion at base of OAE1a. ► Pulsed release of light organic carbon to the atmosphere occurred over extended interval (>200 kyr) prior to positive shift.