Detailed study of a new outcrop of Purbeckian sediments at Bienne (Switzerland) has shown that microfacies are very varied, indicating sabkha, tidal-flat, brackish to marine lagoonal, and freshwater paleoenvironments. These microfacies and associated sedimentary structures define shallowing-upward sequences. The base of a sequence is transgressive and formed by oolites or reworked carbonate sediments, which then pass into inter- to supratidal facies. Abundant bioturbation and erosion surfaces frequently mark the top of a sequence. Brecciated beds are thought to have collapsed after dissolution of underlying evaporites. Micropaleontological data complement the interpretation of the microfacies. Dating with charophytes and ostracods places the Purbeckian of Bienne in the Early Berriasian. Furthermore, sedimentological criteria allow for a better definition of the limit between the Purbeckian facies and the marine Berriasian in the western Jura Mountains.